A light-emitting device with a high resolution and high efficiency is provided. The light-emitting device includes a first EL layer, an intermediate layer, and a second EL layer between first and second electrodes. The first EL layer is provided between the first electrode and the intermediate layer, and the second EL layer is provided between the second electrode and the intermediate layer. Side surfaces of the first EL layer, the intermediate layer, and the second EL layer are substantially aligned. The first EL layer includes a layer having an electron-transport property. The intermediate layer is provided in contact with the layer having an electron-transport property. The intermediate layer includes a first organic compound and an alkali metal or a compound of an alkali metal. The layer having an electron-transport property includes a second organic compound. The second organic compound has a higher glass transition temperature than the first organic compound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a light-emitting device, a display module, an electronic device, and a method for manufacturing any of them.

Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention include a semiconductor device, a light-emitting apparatus, a power storage device, a memory device, an electronic device, a lighting device, an input device (e.g., a touch sensor), an input/output device (e.g., a touch panel), a method for driving any of them, and a method for manufacturing any of them.

2. Description of the Related Art

Light-emitting devices (also referred to as light-emitting elements) including organic compounds and utilizing electroluminescence (EL) have been put to practical use. In the basic structure of such organic EL devices, an organic compound layer containing a light-emitting material is interposed between a pair of electrodes. Carriers are injected by application of voltage to the device, and recombination energy of the carriers is used, whereby light emission can be obtained from the light-emitting material.

Light-emitting apparatuses including light-emitting devices have been developed, for example. Light-emitting devices utilizing electroluminescence (also referred to as EL devices or EL elements) have features such as ease of reduction in thickness and weight, high-speed response to input signals, and driving with a constant DC voltage power source, and have been used in light-emitting apparatuses.

Recent light-emitting apparatuses have been expected to be applied to a variety of uses. Usage examples of large-sized light-emitting apparatuses include a television device for home use (also referred to as a TV or a television receiver), digital signage, and a public information display (PID). In addition, a smartphone, a tablet terminal, and the like each including a touch panel are being developed as portable information terminals.

Higher-resolution light-emitting apparatuses have been required. For example, devices for virtual reality (VR), augmented reality (AR), substitutional reality (SR), or mixed reality (MR) are given as devices requiring high-resolution light-emitting apparatuses and have been actively developed.

Patent Document 1 discloses a light-emitting apparatus using an organic EL device (also referred to as an organic EL element) for VR. Patent Document 2 discloses a light-emitting device with a low driving voltage and high reliability that includes an electron-injection layer formed using a mixed film of a transition metal and an organic compound including an unshared electron pair.

REFERENCE

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide a semiconductor device with high design flexibility. Another object of one embodiment of the present invention is to provide a light-emitting apparatus with high display quality. Another object of one embodiment of the present invention is to provide a high-resolution light-emitting apparatus. Another object of one embodiment of the present invention is to provide a high-definition light-emitting apparatus. Another object of one embodiment of the present invention is to provide a highly reliable light-emitting apparatus. Another object of one embodiment of the present invention is to provide a novel light-emitting apparatus that is highly convenient, useful, or reliable. Another object of one embodiment of the present invention is to provide a novel display module that is highly convenient, useful, or reliable. Another object of one embodiment of the present invention is to provide a novel electronic device that is highly convenient, useful, or reliable. Another object of one embodiment of the present invention is to provide a novel light-emitting apparatus, a novel display module, a novel electronic device, or a novel semiconductor device.

Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all of these objects. Other objects can be derived from the description of the specification, the drawings, and the claims.

One embodiment of the present invention is a light-emitting device including a first EL layer, an intermediate layer, and a second EL layer between a first electrode and a second electrode. The first EL layer is between the first electrode and the intermediate layer. The second EL layer is between the second electrode and the intermediate layer. A side surface of the first EL layer, a side surface of the intermediate layer, and a side surface of the second EL layer are substantially aligned. The first EL layer includes a layer having an electron-transport property. The intermediate layer is provided to be in contact with the layer having an electron-transport property. The intermediate layer includes a first organic compound and an alkali metal or a compound of an alkali metal. The layer having an electron-transport property includes a second organic compound. A glass transition temperature of the second organic compound is higher than that of the first organic compound.

Another embodiment of the present invention is a light-emitting device including a first EL layer, an intermediate layer, and a second EL layer between a first electrode and a second electrode. The first EL layer is between the first electrode and the intermediate layer. The second EL layer is between the second electrode and the intermediate layer. A side surface of the first EL layer, a side surface of the intermediate layer, and a side surface of the second EL layer are substantially aligned. The second EL layer includes a first layer and a layer having an electron-transport property. The first layer is positioned between the layer having an electron-transport property and the second electrode. The first layer is provided to be in contact with the layer having an electron-transport property. The first layer includes a first organic compound and an alkali metal or a compound of an alkali metal. The layer having an electron-transport property includes a second organic compound. A glass transition temperature of the second organic compound is higher than that of the first organic compound.

Another embodiment of the present invention is a light-emitting device including a first EL layer, an intermediate layer, and a second EL layer between a first electrode and a second electrode. The first EL layer is between the first electrode and the intermediate layer. The second EL layer is between the second electrode and the intermediate layer. A side surface of the first EL layer, a side surface of the intermediate layer, and a side surface of the second EL layer are substantially aligned. The first EL layer includes a first layer having an electron-transport property. The intermediate layer is provided to be in contact with the first layer having an electron-transport property. The intermediate layer includes a first organic compound and an alkali metal or a compound of an alkali metal. The first layer having an electron-transport property includes a second organic compound. A glass transition temperature of the second organic compound is higher than that of the first organic compound. The second EL layer includes a first layer and a second layer having an electron-transport property. The first layer is positioned between the second layer having an electron-transport property and the second electrode. The first layer is provided to be in contact with the second layer having an electron-transport property. The first layer includes a third organic compound and an alkali metal or a compound of an alkali metal. The second layer having an electron-transport property includes a fourth organic compound. A glass transition temperature of the fourth organic compound is higher than that of the third organic compound.

Another embodiment of the present invention is the light-emitting device in which the glass transition temperature of the fourth organic compound is higher than that of the third organic compound by 15° C. or more.

Another embodiment of the present invention is the light-emitting device in which the glass transition temperature of the second organic compound is higher than that of the first organic compound by 15° C. or more.

Another embodiment of the present invention is the light-emitting device in which a refractive index of the fourth organic compound is higher than that of the third organic compound.

Another embodiment of the present invention is the light-emitting device in which a refractive index of the second organic compound is higher than that of the first organic compound.

Another embodiment of the present invention is the light-emitting device in which the third organic compound includes a first heteroaromatic ring, the fourth organic compound includes a first polycyclic heteroaromatic ring, and the number of rings in the first polycyclic heteroaromatic ring is larger than or equal to that of rings in the first heteroaromatic ring.

Another embodiment of the present invention is the light-emitting device in which the first organic compound includes a second heteroaromatic ring, the second organic compound includes a second polycyclic heteroaromatic ring, and the number of rings in the second polycyclic heteroaromatic ring is larger than or equal to that of rings in the second heteroaromatic ring.

Another embodiment of the present invention is the light-emitting device in which the first heteroaromatic ring includes a phenanthroline skeleton.

Another embodiment of the present invention is the light-emitting device in which the second heteroaromatic ring includes a phenanthroline skeleton.

Another embodiment of the present invention is the light-emitting device in which the first polycyclic heteroaromatic ring includes two or more nitrogen atoms.

Another embodiment of the present invention is the light-emitting device in which the second polycyclic heteroaromatic ring includes two or more nitrogen atoms.

Another embodiment of the present invention is the light-emitting device in which a LUMO level of the fourth organic compound is lower than that of the third organic compound by 0.2 eV or more.

Another embodiment of the present invention is the light-emitting device in which a LUMO level of the second organic compound is lower than that of the first organic compound by 0.2 eV or more.

Another embodiment of the present invention is the light-emitting device including a second intermediate layer and a third EL layer between the first electrode and the second electrode.

One embodiment of the present invention can provide a semiconductor device with high design flexibility. Another embodiment of the present invention can provide a light-emitting apparatus with high display quality. Another embodiment of the present invention can provide a high-resolution light-emitting apparatus. Another embodiment of the present invention can provide a high-definition light-emitting apparatus. Another embodiment of the present invention can provide a highly reliable light-emitting apparatus. Another embodiment of the present invention can provide a novel light-emitting apparatus that is highly convenient, useful, or reliable. Another embodiment of the present invention can provide a novel display module that is highly convenient, useful, or reliable. Another embodiment of the present invention can provide a novel electronic device that is highly convenient, useful, or reliable. Another embodiment of the present invention can provide a novel light-emitting apparatus, a novel display module, a novel electronic device, or a novel semiconductor device.

Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Other effects can be derived from the description of the specification, the drawings, and the claims.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to the drawings. Note that the embodiments of the present invention are not limited to the following description, and it will be readily appreciated by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description in the following embodiments.

The position, size, range, or the like of each component illustrated in drawings does not represent the actual position, size, range, or the like in some cases for easy understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings.

Note that the terms “film” and “layer” can be used interchangeably depending on the case or the circumstances. For example, the term “conductive layer” can be replaced with the term “conductive film”. As another example, the term “insulating film” can be replaced with the term “insulating layer”.

In this specification and the like, a device formed using a metal mask or a fine metal mask (FMM) may be referred to as a device having a metal mask (MM) structure. In this specification and the like, a device formed without using a metal mask or an FMM may be referred to as a device having a metal maskless (MML) structure.

In this specification and the like, a hole or an electron is sometimes referred to as a carrier. Specifically, a hole-injection layer or an electron-injection layer may be referred to as a carrier-injection layer, a hole-transport layer or an electron-transport layer may be referred to as a carrier-transport layer, and a hole-blocking layer or an electron-blocking layer may be referred to as a carrier-blocking layer. Note that the above-described carrier-injection layer, carrier-transport layer, and carrier-blocking layer cannot be distinguished from each other depending on the cross-sectional shape, properties, or the like in some cases. One layer may have two or three functions of the carrier-injection layer, the carrier-transport layer, and the carrier-blocking layer in some cases.

In this specification and the like, a light-emitting device (also referred to as a light-emitting element) includes an EL layer between a pair of electrodes. The EL layer includes at least a light-emitting layer. In this specification and the like, a light-receiving device (also referred to as a light-receiving element) includes at least an active layer functioning as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode and the other may be referred to as a common electrode.

In this specification and the like, a tapered shape indicates a shape in which at least part of a side surface of a component is inclined to a substrate surface. For example, a tapered shape preferably includes a region where the angle between the inclined side surface and the substrate surface (such an angle is also referred to as a taper angle) is less than 90°. Note that the side surface of the component and the substrate surface are not necessarily completely flat and may be substantially flat with a slight curvature or with slight unevenness.

Note that the light-emitting apparatus in this specification includes, in its category, an image display device that uses an organic EL device. The light-emitting apparatus may also include a module in which an organic EL device is provided with a connector such as an anisotropic conductive film or a tape carrier package (TCP), a module in which a printed wiring board is provided at the end of a TCP, and a module in which an integrated circuit (IC) is directly mounted on an organic EL device by a chip on glass (COG) method. Furthermore, a lighting device or the like may include the light-emitting apparatus.

An organic EL element (hereinafter also referred to as a light-emitting device) includes an organic compound layer (corresponding to an organic semiconductor film) containing a light-emitting substance, between electrodes (between a first electrode and a second electrode), and energy generated by recombination of carriers (holes and electrons) injected to the organic compound layer from the electrodes causes light emission.

FIG.1Aillustrates a light-emitting device130of one embodiment of the present invention. The light-emitting device of one embodiment of the present invention is a tandem light-emitting device and includes an organic compound layer103that includes a first light-emitting unit501including a first light-emitting layer113_1, a second light-emitting unit502including a second light-emitting layer1132, and an intermediate layer116, between a first electrode101including an anode and a second electrode102including a cathode. Note that the light-emitting unit is also referred to as an EL layer.

Although a light-emitting device including one intermediate layer116and two light-emitting units is described as an example in this embodiment, the light-emitting device may include n (n is an integer greater than or equal to 1) intermediate layer(s) (hereinafter also referred to as charge generation layer(s)) and n+1 light-emitting units.

For example, the light-emitting device130illustrated inFIG.1Bis an example of a tandem light-emitting device with n=2 including the first light-emitting unit501, a first intermediate layer116_1, the second light-emitting unit502, a second intermediate layer116_2, and a third light-emitting unit503. The intermediate layer116includes at least a p-type layer117(hereinafter also referred to as a charge generation region) and an n-type layer119(hereinafter also referred to as an electron-injection buffer region). Between the n-type layer119and the p-type layer117, an electron-relay layer118(hereinafter also referred to as an electron-relay region) for smooth donation and acceptance of electrons between the two layers may be provided.

Note that the color gamut of light emitted by the light-emitting layers in the light-emitting units may be the same or different. In addition, the light-emitting layer may have a single-layer structure or a stacked-layer structure. For example, white light emission can be achieved with a structure where light-emitting layers in the first light-emitting unit and the third light-emitting unit emit light in a blue region and light-emitting layers in a stacked-layer structure of the second light-emitting unit emit light in a red region and light in a green region.

The light-emitting device of one embodiment of the present invention may be manufactured by a lithography method such as a photolithography method. In the case of employing the photolithography method, at least the second light-emitting layer113_2and layers in the organic compound layer which are closer to the first electrode101than the second light-emitting layer113_2are processed at the same time so that end portions thereof are substantially aligned in the perpendicular direction with respect to the substrate.

Note that in a light-emitting device, a high voltage has been required for injecting carriers, especially electrons, into an organic compound layer where in general electricity is unlikely to flow because of a high energy barrier. In view of this, currently, an n-type layer in an intermediate layer or an electron-injection layer in contact with the cathode includes an alkali metal such as lithium (Li) or a compound of an alkali metal, whereby a reduction in voltage can be achieved.

However, when exposure to the air is performed in a manufacturing process of a light-emitting device, the alkali metal or the compound thereof diffuses into an adjacent layer, which might cause an increase in driving voltage or a decrease in emission efficiency of the light-emitting device.

In particular, a tandem light-emitting device has a structure where a plurality of light-emitting layers are stacked in series with an intermediate layer therebetween, and the intermediate layer has a structure including a layer containing an alkali metal or a compound of an alkali metal so that electrons can be injected into a light-emitting unit that is in contact with the anode side of the intermediate layer. That is, the probability that the layer containing an alkali metal or a compound of an alkali metal will react with an atmospheric component such as water or oxygen is higher in the tandem light-emitting device than in the light-emitting device with the single structure.

In recent years, as a method for forming an organic semiconductor film in a predetermined shape, a vacuum evaporation method with a metal mask (mask vapor deposition) is widely used. However, density and resolution have been recently increasing; thus, increasing resolution in the mask deposition is reaching its limit due to problems typified by a problem of the degree of positioning precision and a problem of the arrangement interval of the substrate. By contrast, a finer pattern can be formed by shape processing of an organic semiconductor film by a photolithography method. Moreover, because of the easiness of large-area processing in this method, the processing of an organic semiconductor film by a photolithography method is being researched.

However, in the case where a tandem light-emitting device is manufactured by a photolithography method, an intermediate layer is exposed to the air, a resist resin, water, a chemical solution, or the like in a processing step, resulting in degradation of characteristics due to a layer of an alkali metal or a compound of an alkali metal. That is, like exposure of the electron-injection layer to the atmospheric component and a photolithography process, the exposure of the layer of an alkali metal or a compound of an alkali metal in the intermediate layer to the atmospheric component and the photolithography process causes a significant increase in driving voltage and a significant decrease in emission efficiency.

In view of this, a layer provided to be in contact with a layer including an alkali metal such as Li or a compound of an alkali metal, such as the n-type layer of the intermediate layer or the electron-injection layer, is preferably formed using a material that inhibits diffusion of the alkali metal such as Li or the compound of the alkali metal.

For example, as illustrated inFIG.2A, the light-emitting device130has a structure where an organic compound layer12containing lithium14is provided over and in contact with an organic compound layer10. Note that the organic compound layer10corresponds to the first electron-transport layer1141, the second electron-transport layer114_2, and the like illustrated inFIG.1A. The organic compound layer12containing the lithium14corresponds to the n-type layer119, an electron-injection layer115, and the like illustrated inFIG.1A.

In the case where the organic compound layer10has lithium diffusibility higher than or equal to that of in the organic compound layer12, exposure to the air or a photolithography process performed after formation of the structure illustrated inFIG.2Amakes the lithium14contained in the organic compound layer12diffuse into the organic compound layer10, as illustrated inFIG.2C.

Meanwhile, when a layer with low lithium diffusibility is used as the organic compound layer10, as illustrated inFIG.2B, diffusion of the lithium14into the organic compound layer10can be inhibited even when exposure to the air or a photolithography process is performed.

An organic compound used for the layer with low diffusibility of an alkali metal such as Li or a compound of an alkali metal preferably has a high molecular weight, a high density, and high robustness. Thus, the organic compound used for the organic compound layer10preferably has a higher glass transition temperature (Tg) than the organic compound used for the organic compound layer12including an alkali metal or a compound of an alkali metal.

For example, the glass transition temperature (Tg) of the organic compound used for the organic compound layer10is higher than that of the organic compound used for the organic compound layer12by preferably 15° C. or more, further preferably 20° C. or more, still further preferably 25° C. or more. Specifically, for example, the glass transition temperature (Tg) of the organic compound used for the organic compound layer10is preferably higher than or equal to 120° C., further preferably higher than or equal to 140° C., still further preferably higher than or equal to 160° C.

Note that the glass transition temperature (Tg) of the organic compound can be measured by differential scanning calorimetry (DSC) measurement, for example. In the case where processing is performed by a photolithography method, the use of an organic compound with a high glass transition temperature, which is less likely to be affected by temperatures, an atmosphere, a resist resin, water, a chemical solution, or the like to which the organic compound is exposed during the process, enables manufacturing of a device with high design flexibility.

In addition, an organic compound with a high refractive index has a high density and high robustness, and thus is suitable as the organic compound used for the organic compound layer10. Therefore, the organic compound used for the organic compound layer10preferably has a higher refractive index than the organic compound used for the organic compound layer12including an alkali metal or a compound of an alkali metal.

For example, the refractive index of the organic compound used for the organic compound layer10is higher than that of the organic compound used for the organic compound layer12by preferably 0.03 or more, further preferably 0.06 or more, still further preferably 0.1 or more. Specifically, for example, the ordinary refractive index of the organic compound used for the organic compound layer10at a wavelength of 633 nm is preferably higher than or equal to 1.80, further preferably higher than or equal to 1.84, still further preferably higher than or equal to 1.88. The refractive index of the organic compound can be measured by a spectroscopic ellipsometer, for example.

In addition, the organic compound used for the layer with low diffusibility of an alkali metal such as Li or a compound of an alkali metal preferably has excellent electron-transport property and high chemical stability for the favorable voltage characteristics and reliability of the light-emitting device. Therefore, as the organic compound used for the organic compound layer10, it is preferable to use an organic compound with the lowest unoccupied molecular orbital (LUMO) level lower than that of the organic compound used for the organic compound layer12including an alkali metal or a compound of an alkali metal.

For example, the LUMO level of the organic compound used for the organic compound layer10is lower than that of the organic compound used for the organic compound layer12by 0.2 eV or more. Specifically, for example, the LUMO level of the organic compound used for the organic compound layer10is preferably lower than or equal to −2.8 eV, further preferably lower than or equal to −2.9 eV, still further preferably lower than or equal to −3.0 eV and higher than or equal to −3.2 eV. The LUMO level of the organic compound can be derived from the electrochemical characteristics (the reduction potentials) of the compound which is measured by cyclic voltammetry (CV), for example.

As the organic compound suitable for the organic compound layer10, a material including a π-electron deficient heteroaromatic ring and having favorable electron-transport property is preferably used. In order to have a high electron-transport property and high robustness, the organic compound used for the organic compound layer10preferably includes a polycyclic heteroaromatic ring with the same or a larger number of rings as or than the heteroaromatic ring of the organic compound used for the organic compound layer12including an alkali metal or a compound of an alkali metal.

Specifically, as the organic compound suitable for the organic compound layer10, an organic compound including a heteroaromatic ring having a pyridine skeleton, an organic compound including a heteroaromatic ring having a diazine skeleton, or an organic compound including a heteroaromatic ring having a triazine skeleton can be used, for example. In order to have high chemical stability and a high electron-transport property, the organic compound preferably includes a six-membered heteroaromatic ring and two or more nitrogen atoms. For example, it is possible to use an organic compound including a nitrogen-containing polycyclic heteroaromatic ring having a diazine skeleton, such as a quinoxaline skeleton, a quinazoline skeleton, a benzoquinoxaline skeleton, or a benzoquinazoline skeleton.

The organic compound layer12is formed using a material that diffuses an alkali metal such as Li or a compound of an alkali metal more than the organic compound suitable for the organic compound layer10. As the organic compound suitable for the organic compound layer12, a material including a TE-electron deficient heteroaromatic ring and having a favorable electron-transport property is preferably used. Specifically, for example, an organic compound including a heteroaromatic ring having a pyridine skeleton, an organic compound including a heteroaromatic ring having a diazine skeleton, or an organic compound including a heteroaromatic ring having a triazine skeleton can be used. Alternatively, an organic compound including a polycyclic heteroaromatic ring such as a phenanthroline skeleton can be used.

In particular, an organic compound having a phenanthroline skeleton such as mTpPPhen, PnNPhen, or mPPhen2P is preferable, and an organic compound having a phenanthroline dimer structure such as mPPhen2P has excellent stability and thus is further preferable. In addition, the organic compound including a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound including a heteroaromatic ring having a triazine skeleton are preferable because they have a high electron-transport property and contribute to a reduction in driving voltage of the light-emitting device.

Structures of the light-emitting device130other than the above-described structures are specifically described below.

The first light-emitting unit501and the second light-emitting unit502may each include a functional layer in addition to the light-emitting layer. AlthoughFIG.1Aillustrates the structure where the first light-emitting unit501is provided with a hole-injection layer111, a first hole-transport layer112_1, and a first electron-transport layer114_1in addition to the first light-emitting layer113_1and the second light-emitting unit502is provided with a second hole-transport layer1122, a second electron-transport layer1142, and the electron-injection layer115in addition to the second light-emitting layer1132, the structure of the organic compound layer103in the present invention is not limited thereto and any of the layers may be omitted or other layers may be added. Typical examples of the other layers include a carrier-block layer and an exciton-block layer.

Since the intermediate layer116includes the n-type layer119, the n-type layer119serves as an electron-injection layer for the light-emitting unit on the anode side. Therefore, an electron-injection layer may be provided as necessary in the light-emitting unit on the anode side (the first light-emitting unit501inFIG.1A). Similarly, since the intermediate layer116includes the p-type layer117, the p-type layer117serves as a hole-injection layer for the light-emitting unit on the cathode side. Therefore, a hole-injection layer may be provided as necessary in the light-emitting unit on the cathode side (the second light-emitting unit502inFIG.1A).

Note that the n-type layer119, which is a layer including an alkali metal or a compound of an alkali metal as described above, may include one or more of a metal, a metal compound, and a metal complex.

The p-type layer117which is a charge generation layer is preferably formed using a composite material containing a material having an acceptor property and an organic compound having a hole-transport property. As the organic compound having a hole-transport property used in the composite material, any of a variety of organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and high molecular compounds (e.g., oligomers, dendrimers, and polymers) can be used. Note that the organic compound having a hole-transport property used in the composite material preferably has a hole mobility higher than or equal to 1×10−6cm2/Vs. The organic compound having a hole-transport property used in the composite material preferably has a condensed aromatic hydrocarbon ring or a π-electron rich heteroaromatic ring. As the condensed aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferable. As the π-electron rich heteroaromatic ring, a condensed aromatic ring having at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton is preferable; specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed to a carbazole ring or a dibenzothiophene ring is preferable.

Such an organic compound having a hole-transport property further preferably has any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine including a substituent that has a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that has a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine through an arylene group may be used. Note that the organic compound having a hole-transport property preferably includes an N,N′-bis(4-biphenyl)amino group to enable manufacturing a light-emitting device with a long lifetime.

Examples of the aromatic amine compounds that can be used as the material having a hole-transport property include N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

As the substance having an acceptor property contained in the p-type layer117, an organic compound having an electron-withdrawing group (a halogen group or a cyano group) can be used, and the examples include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. A compound in which electron-withdrawing groups are bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, is particularly preferable because it is thermally stable. A [3]radialene derivative having an electron-withdrawing group (in particular, a cyano group, a halogen group such as a fluoro group, or the like) has a very high electron-accepting property and thus is preferable. Specific examples include α,α′,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3, 5-difluoro-4-(trifluoromethyl)be nzeneacetonitrile], and α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. As the substance having an acceptor property, a transition metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, or manganese oxide can be used, other than the above-described organic compounds.

The electron-relay layer118contains a substance having an electron-transport property and has a function of preventing an interaction between the n-type layer119and the p-type layer117and smoothly transferring electrons. The LUMO level of the substance having an electron-transport property contained in the electron-relay layer118is preferably between the LUMO level of the acceptor substance in the p-type layer117and the LUMO level of an organic compound contained in a layer that is included in the light-emitting unit on the first electrode101side and is in contact with the intermediate layer116(the first electron-transport layer114_1in the first light-emitting unit501inFIG.1A). As a specific value of the energy level, the LUMO level of the substance having an electron-transport property in the electron-relay layer118is preferably higher than or equal to −5.0 eV, further preferably higher than or equal to −5.0 eV and lower than or equal to −3.0 eV. Note that as the substance having an electron-transport property in the electron-relay layer118, a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand is preferably used.

A tandem light-emitting device including the intermediate layer116does not suffer a significant increase in driving voltage and a significant decrease in emission efficiency even when the organic compound layer103is processed by a photolithography method, and thus has favorable characteristics.

Then, components of the light-emitting device130, other than the intermediate layer116, are described.

The first electrode101is the electrode including an anode. The first electrode101may have a stacked-layer structure where a layer in contact with the organic compound layer103functions as the anode. The anode is preferably formed using any of metals, alloys, and conductive compounds with a high work function (specifically, higher than or equal to 4.0 eV), mixtures thereof, and the like. Specific examples include indium oxide-tin oxide (ITO: indium tin oxide), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). Films of such conductive metal oxides are usually formed by a sputtering method, but may be formed by application of a sol-gel method or the like. For example, a film of indium oxide-zinc oxide is formed by a sputtering method using a target in which 1 wt % to 20 wt % zinc oxide is added to indium oxide. Furthermore, a film of indium oxide containing tungsten oxide and zinc oxide (IWZO) can be formed by a sputtering method using a target in which 0.5 wt % to 5 wt % tungsten oxide and 0.1 wt % to 1 wt % zinc oxide are added to indium oxide. Alternatively, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), nitride of a metal material (e.g., titanium nitride), or the like can be used for the anode. Graphene can also be used for the anode. Note that when a composite material contained in the p-type layer117in the intermediate layer116is used for a layer that is in contact with the anode (the layer is typically a hole-injection layer), an electrode material can be selected regardless of the work function.

The organic compound layer103has a stacked-layer structure. As the stacked-layer structure,FIG.1Aillustrates the structure including the first light-emitting unit501including the first light-emitting layer113_1, the intermediate layer116, and the second light-emitting unit502including the second light-emitting layer113_2. In the structure, two light-emitting units are stacked with the intermediate layer therebetween; however, three or more light-emitting units may be stacked. Also in that case, an intermediate layer is provided between the light-emitting units. Each of the light-emitting units also has a stacked-layer structure. The light-emitting units can include a variety of functional layers such as a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, carrier-block layers (a hole-block layer and an electron-block layer), and an exciton-block layer as appropriate, without being limited to the structure illustrated inFIG.1A.

The hole-injection layer111is provided in contact with the anode and has a function of facilitating injection of holes into the organic compound layer103(the first light-emitting unit501). The hole-injection layer111can be formed using a porphyrin-based compound such as phthalocyanine (abbreviation: H2Pc), a phthalocyanine-based complex compound such as copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a high molecular compound such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS).

The hole-injection layer111may be formed using a substance having an electron-accepting property. As the substance having an acceptor property, any of substances described as examples of the acceptor substance that is used in the composite material contained in the p-type layer117in the intermediate layer116can similarly be used.

Furthermore, the hole-injection layer111may be formed using the same composite material contained in the p-type layer117in the intermediate layer116.

In the hole-injection layer111, it is further preferable that the organic compound having a hole-transport property used in the composite material have a relatively deep HOMO level higher than or equal to −5.7 eV and lower than or equal to −5.4 eV. Using the organic compound having a hole-transport property which has a relatively deep HOMO level in the composite material makes it easy to inject holes into the hole-transport layer and to obtain a light-emitting device having a long lifetime. In addition, when the organic compound having a hole-transport property that is used in the composite material has a relatively deep HOMO level, induction of holes can be inhibited properly so that the light-emitting device can have a longer lifetime.

The formation of the hole-injection layer111can improve the hole-injection property, which allows the light-emitting device to be driven at a low voltage.

Among substances having an acceptor property, the organic compound having an acceptor property is easy to use because it is easily deposited by vapor deposition.

Since the p-type layer117in the intermediate layer116functions as a hole-injection layer, another hole-injection layer is not provided in the second light-emitting unit502; however, a hole-injection layer may be provided in the second light-emitting unit502.

The hole-transport layer (the first hole-transport layer112_1and the second hole-transport layer112_2) each include an organic compound having a hole-transport property. The organic compound having a hole-transport property preferably has a hole mobility higher than or equal to 1×10−6cm2/Vs.

The light-emitting layers (the first light-emitting layer113_1and the second light-emitting layer113_2) each preferably include a light-emitting substance and a host material. The light-emitting layer may additionally include other materials. Alternatively, the light-emitting layer may be a stack of two layers with different compositions.

As the light-emitting substance, fluorescent substances, phosphorescent substances, substances exhibiting thermally activated delayed fluorescence (TADF), or other light-emitting substances may be used.

Examples of the material that can be used as a fluorescent substance in the light-emitting layer are as follows. Other fluorescent substances can also be used.

Examples of the material that can be used when a phosphorescent substance is used as the light-emitting substance in the light-emitting layer are as follows.

Other examples include organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), and bis[4,6-di(naphthalen-1-yl)pyrimidinato] (dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]); organometallic iridium complexes having a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]); organometallic iridium complexes having a pyridine skeleton, such as tris(1-phenylisoquinolinato-N,C2′)iridium(III) (abbreviation: [Ir(piq)3]) and bis(1-phenylisoquinolinato-N,C2′)iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]); platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]). These compounds emit red phosphorescent light and have an emission peak in the wavelength range from 600 nm to 700 nm. Furthermore, the organometallic iridium complexes having a pyrazine skeleton can provide red light emission with favorable chromaticity.

Besides the above phosphorescent compounds, known phosphorescent compounds may be selected and used.

Examples of the TADF material include a fullerene, a derivative thereof, an acridine, a derivative thereof, and an eosin derivative. Furthermore, a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), can be given. Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP), which are represented by the following structural formulae.

Alternatively, a heterocyclic compound having one or both of a TE-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring that is represented by the following structure formulae, such as 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-tria zine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), or 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA) can be used. Such a heterocyclic compound is preferable because of having high electron-transport and hole-transport properties owing to a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring. Among skeletons having the π-electron deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, and a pyridazine skeleton), and a triazine skeleton are preferable because of their high stability and reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because of their high acceptor properties and high reliability. Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton have high stability and reliability; thus, at least one of these skeletons is preferably included. A dibenzofuran skeleton is preferable as a furan skeleton, and a dibenzothiophene skeleton is preferable as a thiophene skeleton. As a pyrrole skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable. Note that a substance in which the π-electron rich heteroaromatic ring is directly bonded to the π-electron deficient heteroaromatic ring is particularly preferable because the electron-donating property of the π-electron rich heteroaromatic ring and the electron-accepting property of the π-electron deficient heteroaromatic ring are both improved, the energy difference between the S1 level and the T1 level becomes small, and thus thermally activated delayed fluorescence can be obtained with high efficiency. Note that an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron deficient heteroaromatic ring. As a π-electron rich skeleton, an aromatic amine skeleton, a phenazine skeleton, or the like can be used. As a π-electron deficient skeleton, a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring having a cyano group or a nitrile group, such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, or the like can be used. As described above, a π-electron deficient skeleton and a π-electron rich skeleton can be used instead of at least one of the π-electron deficient heteroaromatic ring and the π-electron rich heteroaromatic ring.

Alternatively, a TADF material whose singlet excited state and triplet excited state are in a thermal equilibrium state may be used. Since such a TADF material enables a short emission lifetime (excitation lifetime), the efficiency of a light-emitting device in a high-luminance region can be less likely to decrease. Specifically, a material having the following molecular structure can be used.

Note that a TADF material is a material having a small difference between the S1 level and the T1 level and a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Thus, a TADF material can upconvert triplet excitation energy into singlet excitation energy (i.e., reverse intersystem crossing) using a small amount of thermal energy and efficiently generate a singlet excited state. In addition, the triplet excitation energy can be converted into light emission.

An exciplex whose excited state is formed of two kinds of substances has an extremely small difference between the S1 level and the T1 level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.

A phosphorescent spectrum observed at a low temperature (e.g., 77 K to 10 K) is used for an index of the T1 level. When the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescent spectrum at a tail on the short wavelength side is the S1 level and the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescent spectrum at a tail on the short wavelength side is the T1 level, the difference between the S1 level and the T1 level of the TADF material is preferably smaller than or equal to 0.3 eV, further preferably smaller than or equal to 0.2 eV.

When a TADF material is used as the light-emitting substance, the S1 level of the host material is preferably higher than that of the TADF material. In addition, the T1 level of the host material is preferably higher than that of the TADF material.

As the host material in the light-emitting layer, various carrier-transport materials such as materials having an electron-transport property and/or materials having a hole-transport property, and the TADF materials can be used.

The material having a hole-transport property is preferably an organic compound having an amine skeleton or a π-electron rich heteroaromatic ring skeleton, for example. Examples of the material include compounds having an aromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N′-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N′-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF); compounds having a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); compounds having a thiophene skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV); and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above materials, the compound having an aromatic amine skeleton or the compound having a carbazole skeleton is preferable because the compound is highly reliable and has a high hole-transport property to contribute to a reduction in driving voltage. In addition, the organic compounds given as examples of the material having a hole-transport property that can be used for the hole-transport layer can also be used.

As the TADF material that can be used as the host material, the above materials mentioned as the TADF material can also be used. When the TADF material is used as the host material, triplet excitation energy generated in the TADF material is converted into singlet excitation energy by reverse intersystem crossing and transferred to the light-emitting substance, whereby the emission efficiency of the light-emitting device can be increased. Here, the TADF material functions as an energy donor, and the light-emitting substance functions as an energy acceptor.

This is very effective in the case where the light-emitting substance is a fluorescent substance. In this case, the S1 level of the TADF material is preferably higher than that of the fluorescent substance in order that high emission efficiency can be obtained. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than that of the fluorescent substance.

It is also preferable to use a TADF material that emits light whose wavelength overlaps with the wavelength on a lowest-energy-side absorption band of the fluorescent substance. This enables smooth transfer of excitation energy from the TADF material to the fluorescent substance and accordingly enables efficient light emission, which is preferable.

In addition, in order to efficiently generate singlet excitation energy from the triplet excitation energy by reverse intersystem crossing, carrier recombination preferably occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material not be transferred to the triplet excitation energy of the fluorescent substance. For that reason, the fluorescent substance preferably has a protective group around a luminophore (a skeleton which causes light emission) of the fluorescent substance. As the protective group, a substituent having no π bond and a saturated hydrocarbon are preferably used. Specific examples include an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms. It is further preferable that the fluorescent substance have a plurality of protective groups. The substituents having no π bond are poor in carrier transport performance, whereby the TADF material and the luminophore of the fluorescent substance can be made away from each other with little influence on carrier transportation or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) that causes light emission in a fluorescent substance. The luminophore is preferably a skeleton having a π bond, further preferably includes an aromatic ring, and still further preferably includes a condensed aromatic ring or a condensed heteroaromatic ring. Examples of the condensed aromatic ring or the condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. Specifically, a fluorescent substance having any of a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton is preferable because of its high fluorescence quantum yield.

In the case where a fluorescent substance is used as the light-emitting substance, a material having an anthracene skeleton is suitably used as the host material. The use of a substance having an anthracene skeleton as the host material for the fluorescent substance makes it possible to obtain a light-emitting layer with high emission efficiency and high durability. Among the substances having an anthracene skeleton, a substance having a diphenylanthracene skeleton, in particular, a substance having a 9,10-diphenylanthracene skeleton, is chemically stable and thus is preferably used as the host material. The host material preferably has a carbazole skeleton because the hole-injection and hole-transport properties are improved; further preferably, the host material has a benzocarbazole skeleton in which a benzene ring is further condensed to carbazole because the HOMO level thereof is shallower than that of carbazole by approximately 0.1 eV and thus holes enter the host material easily. In particular, the host material preferably has a dibenzocarbazole skeleton because the HOMO level thereof is shallower than that of carbazole by approximately 0.1 eV so that holes enter the host material easily, the hole-transport property is improved, and the heat resistance is increased. Accordingly, a substance that has both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole or dibenzocarbazole skeleton) is further preferable as the host material. Note that in terms of the hole-injection and hole-transport properties described above, instead of a carbazole skeleton, a benzofluorene skeleton or a dibenzofluorene skeleton may be used. Examples of such a substance include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(1-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,β-ADN), 2-(10-phenylanthracen-9-yl)dibenzofuran, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: βN-mβNPAnth), and 1-{4-[10-(biphenyl-4-yl)-9-anthracenyl]phenyl}-2-ethyl-1H-benzimidazole (abbreviation: EtBImPBPhA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit excellent properties and thus are preferably selected.

Note that the host material may be a mixture of a plurality of kinds of substances; in the case of using a mixed host material, it is preferable to mix a material having an electron-transport property with a material having a hole-transport property. By mixing the material having an electron-transport property with the material having a hole-transport property, the transport property of the light-emitting layer113can be easily adjusted and a recombination region can be easily controlled. The weight ratio of the content of the material having a hole-transport property to the content of the material having an electron-transport property may be 1:19 to 19:1.

Note that a phosphorescent substance can be used as part of the mixed material. When a fluorescent substance is used as the light-emitting substance, a phosphorescent substance can be used as an energy donor for supplying excitation energy to the fluorescent substance.

An exciplex may be formed of these mixed materials. These mixed materials are preferably selected so as to form an exciplex that exhibits light emission whose wavelength overlaps with the wavelength on a lowest-energy-side absorption band of the light-emitting substance, in which case energy can be transferred smoothly and light emission can be obtained efficiently. The use of such a structure is preferable because the driving voltage can also be reduced.

Note that at least one of the materials forming an exciplex may be a phosphorescent substance. In this case, triplet excitation energy can be efficiently converted into singlet excitation energy by reverse intersystem crossing.

In order to form an exciplex efficiently, a material having an electron-transport property is preferably combined with a material having a hole-transport property and a HOMO level higher than or equal to that of the material having an electron-transport property. In addition, the LUMO level of the material having a hole-transport property is preferably higher than or equal to that of the material having an electron-transport property. Note that the LUMO levels and the HOMO levels of the materials can be derived from the electrochemical characteristics (the reduction potentials and the oxidation potentials) of the materials that are measured by cyclic voltammetry (CV).

In the cyclic voltammetry (CV) measurement, the values of HOMO and LUMO levels can be calculated on the basis of an oxidation peak potential (Epa) and a reduction peak potential (Epc), which are obtained by changing the potential of a working electrode with respect to that of a reference electrode within an appropriate range. In the measurement, the HOMO and LUMO levels are obtained by potential scanning in positive direction and potential scanning in negative direction, respectively.

Calculation steps of the HOMO and LUMO levels are described in detail. A standard oxidation-reduction potential (Eo) (=Epa+Epc)/2) is calculated from the oxidation peak potential (Epa) and the reduction peak potential (Epc), which are obtained by the cyclic voltammogram of a material. Then, a potential energy (Ex) of the reference electrode with respect to a vacuum level is subtracted from the standard oxidation-reduction potential (Eo), whereby the HOMO and LUMO levels can be obtained.

Note that the reversible oxidation-reduction wave is obtained in the above case; in the case where an irreversible oxidation-reduction wave is obtained, the HOMO level is calculated as follows: a value obtained by subtracting a predetermined value (e.g., 0.1 eV) from the oxidation peak potential (Epa) is assumed to be the reduction peak potential (Epc), and the standard oxidation-reduction potential (Eo) is calculated to one decimal point. To calculate the LUMO level, a value obtained by adding a predetermined value (e.g., 0.1 eV) to the reduction peak potential (Epc) is assumed to be the oxidation peak potential (Epa), and the standard oxidation-reduction potential (Eo) is calculated to one decimal point. Note that the values of the HOMO and LUMO levels obtained in the case where an irreversible oxidation-reduction wave is obtained are reference values.

The formation of an exciplex can be confirmed by a phenomenon in which the emission spectrum of the mixed film in which the material having a hole-transport property and the material having an electron-transport property are mixed is shifted to the longer wavelength side than the emission spectrum of each of the materials (or has another peak on the longer wavelength side) observed by comparison of the emission spectra of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials, for example. Alternatively, the formation of an exciplex can be confirmed by a difference in transient response, such as a phenomenon in which the transient photoluminescence (PL) lifetime of the mixed film has longer lifetime components or has a larger proportion of delayed components than that of each of the materials, observed by comparison of transient PL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials. The transient PL can be rephrased as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in transient response observed by comparison of the transient EL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials.

The electron-transport layers (the first electron-transport layer114_1and the second electron-transport layer114_2) each contain a substance having an electron-transport property. The material having an electron-transport property preferably has an electron mobility higher than or equal to 1×10−7cm2/Vs, further preferably higher than or equal to 1×10−6cm2/Vs in the case where the square root of the electric field strength [V/cm] is 600. Note that any other substance can also be used as long as the substance has an electron-transport property higher than a hole-transport property. An organic compound including a TE-electron deficient heteroaromatic ring is preferable as the above organic compound. The organic compound including a π-electron deficient heteroaromatic ring is preferably one or more of an organic compound including a heteroaromatic ring having a polyazole skeleton, an organic compound including a heteroaromatic ring having a pyridine skeleton, an organic compound including a heteroaromatic ring having a diazine skeleton, and an organic compound including a heteroaromatic ring having a triazine skeleton.

As the organic compound having an electron-transport property that can be used in the electron-transport layer, the organic compound that can be used as the organic compound having an electron-transport property in the n-type layer of the intermediate layer116can be similarly used. Among the above materials, the organic compound including a heteroaromatic ring having a diazine skeleton, the organic compound including a heteroaromatic ring having a pyridine skeleton, and the organic compound including a heteroaromatic ring having a triazine skeleton are preferable because of having high reliability. In particular, the organic compound including a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound including a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage.

The electron mobility of the electron-transport layer in the case where the square root of the electric field strength [V/cm] is 600 is preferably higher than or equal to 1×10−7cm2/Vs and lower than or equal to 5×10−5cm2/Vs. The amount of electrons injected into the light-emitting layer can be controlled by the reduction in the electron-transport property of the electron-transport layer114, whereby the light-emitting layer can be prevented from having excess electrons. It is particularly preferable to employ this structure when the hole-injection layer is formed using a composite material that includes a material having a hole-transport property with a relatively deep HOMO level higher than or equal to −5.7 eV and lower than or equal to −5.4 eV, in which case a long lifetime can be achieved. In this case, the material having an electron-transport property preferably has a HOMO level higher than or equal to −6.0 eV.

As the electron-injection layer115, a layer containing an alkali metal, an alkaline earth metal, a rare earth metal, a compound thereof, or a complex thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), 8-hydroxyquinolinato-lithium (abbreviation: Liq), or ytterbium (Yb) in addition to the above-described organic compound having a basic skeleton, can be used. An electride or a layer that is formed using a substance having an electron-transport property and includes an alkali metal, an alkaline earth metal, or a compound thereof can be used as the electron-injection layer115. Examples of the electride include a substance in which electrons are added at a high concentration to calcium oxide-aluminum oxide.

Note that as the electron-injection layer115, it is possible to use a layer containing a substance having an electron-transport property (preferably an organic compound having a bipyridine skeleton) that contains a fluoride of the alkali metal or the alkaline earth metal at a concentration higher than that at which the electron-injection layer115becomes in a microcrystalline state (50 wt % or higher). Since the layer has a low refractive index, a light-emitting device including the layer can have favorable external quantum efficiency.

The second electrode102is an electrode including a cathode. The second electrode102may have a stacked-layer structure where a layer in contact with the organic compound layer103functions as the cathode. For the cathode, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function (specifically, lower than or equal to 3.8 eV) can be used, for example. Specific examples of such a cathode material are elements belonging to Group 1 or 2 of the periodic table, such as alkali metals (e.g., lithium (Li) or cesium (Cs)), magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these elements (e.g., MgAg and AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these rare earth metals. However, when the electron-injection layer is provided between the second electrode102and the electron-transport layer, any of a variety of conductive materials such as Al, Ag, ITO, and indium oxide-tin oxide containing silicon or silicon oxide can be used for the cathode regardless of the work function.

When the second electrode102is formed using a material that transmits visible light, the light-emitting device can emit light from the second electrode102side.

Films of these conductive materials can be formed by a dry process such as a vacuum evaporation method or a sputtering method, an ink-jet method, a spin coating method, or the like. Alternatively, a wet process using a sol-gel method or a wet process using a paste of a metal material may be employed.

Furthermore, any of a variety of methods can be used for forming the organic compound layer103, regardless of a dry method or a wet method. For example, a vacuum evaporation method, a gravure printing method, an offset printing method, a screen printing method, an ink-jet method, a spin coating method, or the like may be used.

Different deposition methods may be used to form the electrodes or the layers described above.

FIG.1Cillustrates two adjacent light-emitting devices (a light-emitting device130aand a light-emitting device130b) included in the light-emitting apparatus of one embodiment of the present invention.

The light-emitting device130aincludes an organic compound layer103abetween a first electrode101aand the second electrode102over an insulating layer175. In the organic compound layer103a, a first light-emitting unit501aand a second light-emitting unit502aare stacked with an intermediate layer116ainterposed therebetween. AlthoughFIG.1Cillustrates the structure where two light-emitting units are stacked, three or more light-emitting units may be stacked. The first light-emitting unit501aincludes a hole-injection layer111a, a first hole-transport layer112a_1, a first light-emitting layer113a_1, and a first electron-transport layer114a_1. The intermediate layer116aincludes a p-type layer117a, an electron-relay layer118a, and an n-type layer119a. The electron-relay layer118ais not necessarily provided. The second light-emitting unit502aincludes a second hole-transport layer112a_2, a second light-emitting layer113a_2, a second electron-transport layer114a_2, and the electron-injection layer115.

The light-emitting device130bincludes an organic compound layer103bbetween a first electrode101band the second electrode102over the insulating layer175. In the organic compound layer103b, a first light-emitting unit501band a second light-emitting unit502bare stacked with an intermediate layer116binterposed therebetween. AlthoughFIG.1Cillustrates the structure where two light-emitting units are stacked, three or more light-emitting units may be stacked. The first light-emitting unit501bincludes a hole-injection layer111b, a first hole-transport layer112b_1, a first light-emitting layer113b_1, and a first electron-transport layer114b_1. The intermediate layer116bincludes a p-type layer117b, an electron-relay layer118b, and an n-type layer119b. The electron-relay layer118bis not necessarily provided. The second light-emitting unit502bincludes a second hole-transport layer112b_2, a second light-emitting layer113b_2, a second electron-transport layer114b_2, and the electron-injection layer115.

The electron-injection layer115and the second electrode102are each preferably one layer shared by the light-emitting device130aand the light-emitting device130b. The layers except for the electron-injection layer115are separated between the organic compound layer103aand the organic compound layer103bbecause processing by a photolithography method is independently performed after a layer to be the second electron-transport layer114a_2is formed and after a layer to be the second electron-transport layer114b_2is formed. The end portions (outlines) of the layers in the organic compound layer103aexcept for the electron-injection layer115are substantially aligned in the direction perpendicular to the substrate due to the processing by a photolithography method. The end portions (outlines) of the layers in the organic compound layer103bexcept for the electron-injection layer115are substantially aligned in the direction perpendicular to the substrate due to the processing by a photolithography method.

Since the organic compound layers are processed by a photolithography method, a distance d between the first electrodes101aand101bcan be shorter than that in the case of employing mask vapor deposition; the distance d can be longer than or equal to 2 μm and shorter than or equal to 5 μm.

The structure of this embodiment can be used in combination with any of the other structures as appropriate.

As illustrated as an example inFIGS.3A and3B, a plurality of light-emitting devices130, which are described in the above embodiment, are formed over the insulating layer175to constitute part of a light-emitting apparatus. In this embodiment, the light-emitting apparatus of one embodiment of the present invention will be described in detail.

A light-emitting apparatus100includes a pixel portion177in which a plurality of pixels178are arranged in matrix. The pixel178includes a subpixel110R, a subpixel110G, and a subpixel110B.

In this specification and the like, for example, matters common to the subpixels110R,110G, and110B are sometimes described using the collective term “subpixel110”. As for components that are distinguished from each other using letters of the alphabet, matters common to the components are sometimes described using reference numerals excluding the letters of the alphabet.

The subpixel110R emits red light, the subpixel110G emits green light, and the subpixel110B emits blue light. Thus, an image can be displayed on the pixel portion177. Note that in this embodiment, three colors of red (R), green (G), and blue (B) are given as examples of colors of light emitted by subpixels; however, the structure of the present invention is not limited to this structure. That is, subpixels of a different combination of colors may be employed. The number of subpixels is not limited to three, and four or more subpixels may be used, for example. Examples of four subpixels include subpixels emitting light of four colors of R, G, B, and white (W), subpixels emitting light of four colors of R, G, B, and yellow (Y), and four subpixels emitting light of R, G, and B and infrared light (IR).

In this specification and the like, the row direction and the column direction are sometimes referred to as the X direction and the Y direction, respectively. The X direction and the Y direction intersect with each other and are perpendicular to each other, for example.

FIG.3Aillustrates an example where subpixels of different colors are arranged in the X direction and subpixels of the same color are arranged in the Y direction. Note that subpixels of different colors may be arranged in the Y direction, and subpixels of the same color may be arranged in the X direction.

A connection portion140and a region141may be provided outside the pixel portion177. The region141is preferably positioned between the pixel portion177and the connection portion140, for example. The organic compound layer103is provided in the region141. A conductive layer151C is provided in the connection portion140.

AlthoughFIG.3Aillustrates an example where the region141and the connection portion140are positioned on the right side of the pixel portion177, the positions of the region141and the connection portion140are not particularly limited. The number of the regions141and the number of the connection portions140can each be one or more.

FIG.3Bis an example of a cross-sectional view taken along the dashed-dotted line A1-A2 inFIG.3A. As illustrated inFIG.3B, the light-emitting apparatus100includes an insulating layer171, a conductive layer172over the insulating layer171, an insulating layer173over the insulating layer171and the conductive layer172, an insulating layer174over the insulating layer173, and the insulating layer175over the insulating layer174. The insulating layer171is preferably provided over a substrate (not illustrated). An opening reaching the conductive layer172is provided in the insulating layers175,174, and173, and a plug176is provided to fill the opening.

In the pixel portion177, the light-emitting device130is provided over the insulating layer175and the plug176. A protective layer131is provided to cover the light-emitting device130. A substrate120is bonded to the protective layer131with a resin layer122. An inorganic insulating layer125and an insulating layer127over the inorganic insulating layer125may be provided between adjacent light-emitting devices130.

AlthoughFIG.3Billustrates cross sections of a plurality of the inorganic insulating layers125and a plurality of the insulating layers127, the inorganic insulating layers125are preferably connected to each other and the insulating layers127are preferably connected to each other when the light-emitting apparatus100is seen from above. That is, the insulating layer125and the insulating layer127preferably have openings above first electrodes.

InFIG.3B, a light-emitting device130R, a light-emitting device130G, and a light-emitting device130B are each illustrated as the light-emitting device130. The light-emitting devices130R,130G, and130B emit light of different colors. For example, the light-emitting device130R can emit red light, the light-emitting device130G can emit green light, and the light-emitting device130B can emit blue light. Alternatively, the light-emitting device130R, the light-emitting device130G, or the light-emitting device130B may emit visible light of another color or infrared light.

Note that the organic compound layer103includes at least a light-emitting layer and can include other functional layers (a hole-injection layer, a hole-transport layer, a hole-blocking layer, an electron-blocking layer, an electron-transport layer, an electron-injection layer, and the like). The organic compound layer103and a common layer104may collectively include functional layers (a hole-injection layer, a hole-transport layer, a hole-blocking layer, a light-emitting layer, an electron-blocking layer, an electron-transport layer, an electron-injection layer, and the like) included in an EL layer that emits light.

The light-emitting apparatus of one embodiment of the present invention can be, for example, a top-emission light-emitting apparatus where light is emitted in the direction opposite to a substrate over which light-emitting devices are formed. Note that the light-emitting apparatus of one embodiment of the present invention may be of a bottom emission type.

The light-emitting device130R has a structure as described in Embodiment 1. The light-emitting device130R includes the first electrode (pixel electrode) including a conductive layer151R and a conductive layer152R, an organic compound layer103R over the first electrode, the common layer104over the organic compound layer103R, and the second electrode (common electrode)102over the common layer104.

Note that the common layer104is not necessarily provided. The common layer104can reduce damage to the organic compound layer103R caused in a later step. In the case where the common layer104is provided, the common layer104may function as an electron-injection layer. In the case where the common layer104functions as an electron-injection layer, a stack of the organic compound layer103R and the common layer104corresponds to the organic compound layer103in Embodiment 1.

Each of the light-emitting devices130has a structure as described in Embodiment 1 and includes the first electrode (pixel electrode) including a conductive layer151and a conductive layer152, the organic compound layer103over the first electrode, the common layer104over the organic compound layer103, and the second electrode (common electrode)102over the common layer104.

In the light-emitting device, one of the pixel electrode and the common electrode functions as an anode and the other functions as a cathode. Hereinafter, description is made on the assumption that the pixel electrode functions as the anode and the common electrode functions as the cathode unless otherwise specified.

The organic compound layer103R, an organic compound layer103G, and an organic compound layer103B are island-shaped layers that are independent of each other. Alternatively, an organic compound layer of the light-emitting devices of one emission color may be independent of an organic compound layer of the light-emitting devices of another emission color. Providing the island-shaped organic compound layer103in each of the light-emitting devices130can inhibit a leakage current between the adjacent light-emitting devices130even in a high-resolution light-emitting apparatus. This can prevent crosstalk, so that a light-emitting apparatus with extremely high contrast can be obtained. Specifically, a light-emitting apparatus having high current efficiency at low luminance can be obtained.

The organic compound layer103may be provided to cover top and side surfaces of the first electrode (pixel electrode) of the light-emitting device130. In that case, the aperture ratio of the light-emitting apparatus100can be easily increased as compared to the structure where an end portion of the organic compound layer103is positioned on the inner side of an end portion of the pixel electrode. Covering the side surface of the pixel electrode of the light-emitting device130with the organic compound layer103can inhibit the pixel electrode from being in contact with the second electrode102; hence, a short circuit of the light-emitting device130can be inhibited. Furthermore, the distance between a light-emitting region (i.e., a region overlapping with the pixel electrode) in the organic compound layer103and the end portion of the organic compound layer103can be increased. Since the end portion of the organic compound layer103might be damaged by processing, using a region that is away from the end portion of the organic compound layer103as the light-emitting region can increase the reliability of the light-emitting device130.

In the light-emitting apparatus of one embodiment of the present invention, the first electrode (pixel electrode) of the light-emitting device may have a stacked-layer structure. For example, in the example illustrated inFIG.3B, the first electrode of the light-emitting device130is a stack of the conductive layer151and the conductive layer152.

In the case where the light-emitting apparatus100is a top-emission light-emitting apparatus, for example, in the pixel electrode of the light-emitting device130, the conductive layer151preferably has high visible light reflectance and the conductive layer152preferably has a visible-light-transmitting property and a high work function. The higher the visible light reflectance of the pixel electrode is, the higher the efficiency of extraction of the light emitted by the organic compound layer103is. In the case where the pixel electrode functions as an anode, the higher the work function of the pixel electrode is, the easier it is to inject holes into the organic compound layer103. Accordingly, when the pixel electrode of the light-emitting device130is a stack of the conductive layer151with high visible light reflectance and the conductive layer152with a high work function, the light-emitting device130can have high light extraction efficiency and a low driving voltage.

Specifically, the visible light reflectance of the conductive layer151is preferably higher than or equal to 40% and lower than or equal to 100%, further preferably higher than or equal to 70% and lower than or equal to 100%, for example. When the conductive layer152is used as an electrode having a visible-light-transmitting property, the visible light transmittance is preferably higher than or equal to 40%, for example.

In the case where a film formed after the formation of the pixel electrode having a stacked-layer structure is removed by a wet etching method, for example, the stack might be impregnated with a chemical solution used for the etching. When the chemical solution reaches the pixel electrode, galvanic corrosion between a plurality of layers constituting the pixel electrode might occur, leading to deterioration of the pixel electrode.

In view of the above, the conductive layer152is preferably formed to cover the top and side surfaces of the conductive layer151. When the conductive layer151is covered with the conductive layer152, the chemical solution does not reach the conductive layer151; thus, occurrence of galvanic corrosion in the pixel electrode can be inhibited. This allows the light-emitting apparatus100to be manufactured by a high-yield method and to be accordingly inexpensive. In addition, generation of a defect in the light-emitting apparatus100can be inhibited, which makes the light-emitting apparatus100highly reliable.

A metal material can be used for the conductive layer151, for example. Specifically, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals, for example.

For the conductive layer152, an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, an indium tin oxide, an indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, an indium zinc oxide containing gallium, an indium zinc oxide containing aluminum, an indium tin oxide containing silicon, an indium zinc oxide containing silicon, and the like. In particular, an indium tin oxide containing silicon can be suitably used for the conductive layer152because of having a work function of higher than or equal to 4.0 eV, for example.

The conductive layer151and the conductive layer152may each be a stack of a plurality of layers containing different materials. In that case, the conductive layer151may include a layer formed using a material that can be used for the conductive layer152, such as a conductive oxide. Furthermore, the conductive layer152may include a layer formed using a material that can be used for the conductive layer151, such as a metal material. In the case where the conductive layer151has a stacked-layer structure of two or more layers, for example, a layer in contact with the conductive layer152can contain the same material as a layer of the conductive layer152in contact with the conductive layer151.

The conductive layer151preferably has an end portion with a tapered shape. Specifically, the end portion of the conductive layer151preferably has a tapered shape with a taper angle of less than 90°. In that case, the conductive layer152provided along the side surface of the conductive layer151also has an end portion with a tapered shape. When the side surface of the conductive layer152has a tapered shape, coverage with the organic compound layer103provided along the side surface of the conductive layer152can be improved.

In the case where the conductive layer151or the conductive layer152has a stacked-layer structure, at least one of the stacked layers preferably has a tapered side surface. The stacked layers of the conductive layer(s) may have different tapered shapes.

FIG.4Aillustrates the case where the conductive layer151has a stacked-layer structure of a plurality of layers containing different materials. As illustrated inFIG.4A, the conductive layer151includes a conductive layer151_1, a conductive layer151_2over the conductive layer151_1, and a conductive layer151_3over the conductive layer151_2. In other words, the conductive layer151illustrated inFIG.4Ahas a three-layer structure. In the case where the conductive layer151has a stacked-layer structure of a plurality of layers as described above, the visible light reflectance of at least one of the layers included in the conductive layer151is made higher than that of the conductive layer152.

In the example illustrated inFIG.4A, the conductive layer151_2is interposed between the conductive layers151_1and151_3. A material that is less likely to change in quality than the conductive layer151_2is preferably used for the conductive layers151_1and151_3. The conductive layer151_1can be formed using, for example, a material that is less likely to migrate due to contact with the insulating layer175than the material for the conductive layer151_2. The conductive layer151_3can be formed using a material an oxide of which has lower electrical resistivity than an oxide of the material used for the conductive layer151_2and which is less likely to be oxidized than the conductive layer151_2.

In this manner, the structure where the conductive layer151_2is interposed between the conductive layers151_1and151_3can expand the range of choices for the material for the conductive layer151_2. The conductive layer151_2, for example, can thus have higher visible light reflectance than at least one of the conductive layers151_1and151_3. For example, aluminum can be used for the conductive layer151_2. The conductive layer151_2may be formed using an alloy containing aluminum. The conductive layer151_1can be formed using titanium; titanium has lower visible light reflectance than aluminum but is less likely to migrate due to contact with the insulating layer175than aluminum. Furthermore, the conductive layer151_3can be formed using titanium; titanium is less likely to be oxidized than aluminum and an oxide of titanium has lower electrical resistivity than aluminum oxide, although titanium has lower visible light reflectance than aluminum.

The conductive layer151_3may be formed using silver or an alloy containing silver. Silver is characterized by its visible light reflectance higher than that of titanium. In addition, silver is characterized by being less likely to be oxidized than aluminum, and silver oxide is characterized by its electrical resistivity lower than that of aluminum oxide. Thus, the conductive layer151_3formed using silver or an alloy containing silver can suitably increase the visible light reflectance of the conductive layer151and inhibit an increase in the electric resistance of the pixel electrode due to oxidation of the conductive layer151_2. Here, as the alloy containing silver, an alloy of silver, palladium, and copper (also referred to as Ag—Pd—Cu or APC) can be used, for example. When the conductive layer151_3is formed using silver or an alloy containing silver and the conductive layer151_2is formed using aluminum, the visible light reflectance of the conductive layer151_3can be higher than that of the conductive layer151_2. Here, the conductive layer151_2may be formed using silver or an alloy containing silver. The conductive layer151_1may be formed using silver or an alloy containing silver.

Meanwhile, a film formed using titanium has better processability in etching than a film formed using silver. Thus, the use of titanium for the conductive layer151_3makes it easy to form the conductive layer151_3. Note that a film formed using aluminum also has better processability in etching than a film formed using silver.

The conductive layer151having a stacked-layer structure of a plurality of layers as described above can improve the characteristics of the light-emitting apparatus. For example, the light-emitting apparatus100can have high light extraction efficiency and high reliability.

Here, in the case where the light-emitting device130has a microcavity structure, the use of silver or an alloy containing silver, i.e., a material with high visible light reflectance, for the conductive layer151_3can favorably increase the light extraction efficiency of the light-emitting apparatus100.

Depending on the selected material or the processing method of the conductive layer151, a side surface of the conductive layer151_2is positioned on the inner side of a side surface of the conductive layer151_1or the conductive layer151_3and a protruding portion might be formed as illustrated inFIG.4A. The protruding portion might impair coverage of the conductive layer151with the conductive layer152to cause a step-cut of the conductive layer152.

Thus, an insulating layer156is preferably provided as illustrated inFIG.4A.FIG.4Aillustrates an example where the insulating layer156is provided over the conductive layer151_1to include a region overlapping with the side surface of the conductive layer151_2. Such a structure can inhibit occurrence of the step-cut or a reduction in the thickness of the conductive layer152due to the protruding portion; thus, connection defects or an increase in driving voltage can be inhibited.

AlthoughFIG.4Aillustrates the structure where the side surface of the conductive layer151_2is entirely covered with the insulating layer156, part of the side surface the conductive layer151_2is not necessarily covered with the insulating layer156. Also in a pixel electrode with a later-described structure, part of the side surface of the conductive layer151_2is not necessarily covered with the insulating layer156.

Here, the insulating layer156preferably has a curved surface as illustrated inFIG.4A. In that case, a step-cut in the conductive layer152covering the insulating layer156is less likely to occur than in the case where the insulating layer156has a perpendicular side surface (a side surface parallel to the Z direction), for example. In addition, a step-cut in the conductive layer152covering the insulating layer156is less likely to occur also in the case where the side surface of the insulating layer156has a tapered shape, or specifically, a tapered shape with a taper angle of less than 90°, than in the case where the insulating layer156has a perpendicular side surface, for example. As described above, the light-emitting apparatus100can be manufactured by a high-yield method. Moreover, the light-emitting apparatus100can have high reliability since generation of defects is inhibited therein.

Note that one embodiment of the present invention is not limited thereto.FIGS.4B to4Dillustrate other examples of the structure of the first electrode101.

FIG.4Billustrates a structure of the first electrode101inFIGS.1A to1C, in which the insulating layer156covers the side surfaces of the conductive layers151_1,151_2, and151_3instead of covering only the side surface of the conductive layer151_2.

FIG.4Cillustrates a structure of the first electrode101inFIGS.1A to1C, in which the insulating layer156is not provided.

FIG.4Dillustrates a structure of the first electrode101inFIGS.1A to1C, in which the conductive layer151does not have a stacked-layer structure and the conductive layer152has a stacked-layer structure.

A conductive layer152_1has higher adhesion to a conductive layer152_2than the insulating layer175does, for example. For the conductive layer152_1, an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon, for example, can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, an indium tin oxide, an indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, an indium titanium oxide, zinc titanate, an aluminum zinc oxide, an indium zinc oxide containing gallium, an indium zinc oxide containing aluminum, an indium tin oxide containing silicon, an indium zinc oxide containing silicon, and the like. Accordingly, peeling of the conductive layer152_2can be inhibited. The conductive layer152_2is not in contact with the insulating layer175.

The conductive layer152_2is a layer whose visible light reflectance (e.g., reflectance with respect to light with a predetermined wavelength in a range greater than or equal to 400 nm and less than 750 nm) is higher than that of the conductive layers151,152_1, and152_3. The visible light reflectance of the conductive layer152_2can be, for example, higher than or equal to 70% and lower than or equal to 100%, and is preferably higher than or equal to 80% and lower than or equal to 100%, further preferably higher than or equal to 90% and lower than or equal to 100%. For the conductive layer152_2, silver or an alloy containing silver can be used, for example. An example of the alloy containing silver is an alloy of silver, palladium, and copper (APC). In the above manner, the light-emitting apparatus100can have high light extraction efficiency. Note that a metal other than silver may be used for the conductive layer152_2.

When the conductive layers151and152serve as the anode, a layer having a high work function is preferably used as the conductive layer152_3. The conductive layer152_3has a higher work function than the conductive layer152_2, for example. For the conductive layer152_3, a material similar to the material usable for the conductive layer152_1can be used, for example. For example, the conductive layers152_1and152_3can be formed using the same kind of material.

When the conductive layers151and152serve as the cathode, a layer having a low work function is preferably used as the conductive layer152_3. The conductive layer152_3has a lower work function than the conductive layer152_2, for example.

The conductive layer152_3is preferably a layer having high visible light transmittance (e.g., transmittance with respect to light with a predetermined wavelength in a range greater than or equal to 400 nm and less than 750 nm). For example, the visible light transmittance of the conductive layer152_3is preferably higher than that of the conductive layers151and152_2. The visible light transmittance of the conductive layer152_3can be, for example, higher than or equal to 60% and lower than or equal to 100%, and is preferably higher than or equal to 70% and lower than or equal to 100%, further preferably higher than or equal to 80% and lower than or equal to 100%. Accordingly, the amount of light absorbed by the conductive layer152_3among light emitted from the organic compound layer103can be reduced. As described above, the conductive layer152_2under the conductive layer152_3can be a layer having high visible light reflectance. Thus, the light-emitting apparatus100can have high light extraction efficiency.

Next, a manufacturing method example of the light-emitting apparatus100having the structure illustrated inFIGS.3A and3Bis described with reference to FIGS.5A to5E,FIGS.6A to6D,FIGS.7A to7D,FIGS.8A to8C,FIGS.9A to9C, andFIGS.10A to10C.

Manufacturing Method Example

Thin films included in the light-emitting apparatus (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, or the like. Examples of a CVD method include a plasma-enhanced CVD (PECVD) method and a thermal CVD method. An example of a thermal CVD method is a metal organic CVD (MOCVD) method.

Thin films included in the light-emitting apparatus (e.g., insulating films, semiconductor films, and conductive films) can also be formed by a wet process such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating.

Specifically, for manufacturing the light-emitting device, a vacuum process such as an evaporation method and a solution process such as a spin coating method or an ink-jet method can be used. Examples of an evaporation method include physical vapor deposition methods (PVD methods) such as a sputtering method, an ion plating method, an ion beam evaporation method, a molecular beam evaporation method, and a vacuum evaporation method, and a chemical vapor deposition method (CVD method). Specifically, the functional layers (e.g., the hole-injection layer, the hole-transport layer, the hole-blocking layer, the light-emitting layer, the electron-blocking layer, the electron-transport layer, and the electron-injection layer) included in the organic compound layer can be formed by an evaporation method (e.g., a vacuum evaporation method), a coating method (e.g., a dip coating method, a die coating method, a bar coating method, a spin coating method, or a spray coating method), a printing method (e.g., ink-jetting, screen printing (stencil), offset printing (planography), flexography (relief printing), gravure printing, or micro-contact printing), or the like.

Thin films included in the light-emitting apparatus can be processed by a photolithography method, for example. Alternatively, a nanoimprinting method, a sandblasting method, a lift-off method, or the like may be used to process thin films. Alternatively, island-shaped thin films may be directly formed by a film formation method using a shielding mask such as a metal mask.

There are two typical examples of photolithography methods. In one of the methods, a resist mask is formed over a thin film that is to be processed, the thin film is processed by etching, for example, and then the resist mask is removed. In the other method, a photosensitive thin film is formed and then processed into a desired shape by light exposure and development.

For etching of thin films, a dry etching method, a wet etching method, a sandblast method, or the like can be used.

First, as illustrated inFIG.5A, the insulating layer171is formed over a substrate (not illustrated). Next, the conductive layer172and a conductive layer179are formed over the insulating layer171, and the insulating layer173is formed over the insulating layer171so as to cover the conductive layer172and the conductive layer179. Then, the insulating layer174is formed over the insulating layer173, and the insulating layer175is formed over the insulating layer174.

As the substrate, a substrate that has heat resistance high enough to withstand at least heat treatment performed later can be used. When an insulating substrate is used, it is possible to use a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, an organic resin substrate, or the like. Alternatively, it is possible to use a semiconductor substrate such as a single crystal semiconductor substrate or a polycrystalline semiconductor substrate of silicon, silicon carbide, or the like; a compound semiconductor substrate of silicon germanium or the like; or an SOI substrate.

Next, as illustrated inFIG.5A, openings reaching the conductive layer172are formed in the insulating layers175,174, and173. Then, the plugs176are formed to fill the openings.

Next, as illustrated inFIG.5A, a conductive film151fto be the conductive layers151R,151G,151B, and151C is formed over the plugs176and the insulating layer175. The conductive film151fcan be formed by a sputtering method or a vacuum evaporation method, for example. A metal material can be used for the conductive film151f, for example.

Subsequently, a resist mask191is formed over the conductive film151f, for example, as illustrated inFIG.5A. The resist mask191can be formed by application of a photosensitive material (photoresist), light exposure, and development.

Subsequently, as illustrated inFIG.5B, the conductive film151fin a region not overlapping with the resist mask191, for example, is removed by an etching method, specifically, a dry etching method, for instance. Note that in the case where the conductive film151fincludes a layer formed using a conductive oxide such as an indium tin oxide, for example, the layer may be removed by a wet etching method. In this manner, the conductive layer151is formed. In the case where part of the conductive film151fis removed by a dry etching method, for example, a recessed portion (also referred to as a depression) may be formed in a region of the insulating layer175not overlapping with the conductive layer151.

Next, the resist mask191is removed as illustrated inFIG.5C. The resist mask191can be removed by ashing using oxygen plasma, for example. Alternatively, an oxygen gas and any of CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, and a Group 18 element such as He may be used. Alternatively, the resist mask191may be removed by wet etching.

Then, as illustrated inFIG.5D, an insulating film156fto be an insulating layer156R, an insulating layer156G, an insulating layer156B, and an insulating layer156C is formed over the conductive layers151R,151G,151B, and151C and the insulating layer175. The insulating film156fcan be formed by a CVD method, an ALD method, a sputtering method, or a vacuum evaporation method, for example.

For the insulating film156f, an inorganic material can be used. As the insulating film156f, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used, for example. For example, an oxide insulating film containing silicon, a nitride insulating film containing silicon, an oxynitride insulating film containing silicon, a nitride oxide insulating film containing silicon, or the like can be used as the insulating film156f. For the insulating film156f, silicon oxynitride can be used, for example.

Subsequently, as illustrated inFIG.5E, the insulating film156fis processed to form the insulating layers156R,156G,156B, and156C. The insulating layer156can be formed by performing etching substantially uniformly on the top surface of the insulating film156f, for example. Such uniform etching for planarization is also referred to as etch back treatment. Note that the insulating layer156may be formed by a photolithography method.

Then, as illustrated inFIG.6A, a conductive film152fto be the conductive layers152R,152G, and152B and a conductive layer152C is formed over the conductive layers151R,151G,151B, and151C and the insulating layers156R,156G,156B,156C, and175. Specifically, the conductive film152fis formed to cover the conductive layers151R,151G,151B, and151C and the insulating layers156R,156G,156B, and156C, for example.

The conductive film152fcan be formed by a sputtering method or a vacuum evaporation method, for example. The conductive film152fcan be formed by an ALD method. A conductive oxide can be used for the conductive film152f, for example. The conductive film152fcan be a stack of a film formed using a metal material and a film formed thereover using a conductive oxide. For example, the conductive film152fcan be a stack of a film formed using titanium, silver, or an alloy containing silver and a film formed thereover using a conductive oxide.

Then, as illustrated inFIG.6B, the conductive film152fis processed by a photolithography method, for example, whereby the conductive layers152R,152G,152B, and152C are formed. Specifically, after a resist mask is formed, part of the conductive film152fis removed by an etching method, for example. The conductive film152fcan be removed by a wet etching method, for example. The conductive film152fmay be removed by a dry etching method. Through the above steps, the pixel electrode including the conductive layer151and the conductive layer152is formed.

Next, hydrophobization treatment is preferably performed on the conductive layer152. The hydrophobization treatment can change the hydrophilic properties of the subject surface to hydrophobic properties or increase the hydrophobic properties of the subject surface. The hydrophobization treatment for the conductive layer152can increase the adhesion between the conductive layer152and the organic compound layer103formed in a later step and inhibit film peeling. Note that the hydrophobization treatment is not necessarily performed.

Next, as illustrated inFIG.6C, an organic compound film103Rf to be the organic compound layer103R is formed over the conductive layers152R,152G, and152B and the insulating layer175.

Note that in the present invention, the organic compound film103Rf has a structure where a plurality of organic compound layers each including at least one light-emitting layer are stacked with an intermediate layer therebetween. The structure of the light-emitting device130described in Embodiment 1 can be referred to for the specific structure.

As illustrated inFIG.6C, the organic compound film103Rf is not formed over the conductive layer152C. For example, a mask for specifying a film formation area (also referred to as an area mask, a rough metal mask, or the like to distinguish from a fine metal mask) is used, so that the organic compound film103Rf can be formed only in a desired region. Employing a film formation step using an area mask and a processing step using a resist mask enables a light-emitting device to be manufactured by a relatively easy process.

The organic compound film103Rf can be formed by an evaporation method, specifically a vacuum evaporation method, for example. The organic compound film103Rf may be formed by a transfer method, a printing method, an ink-jet method, a coating method, or the like.

Next, as illustrated inFIG.6C, a sacrificial film158Rf to be a sacrificial layer158R and a mask film159Rf to be a mask layer159R are sequentially formed over the organic compound film103Rf, the conductive layer152C, and the insulating layer175.

The sacrificial film158Rf and the mask film159Rf can be formed by a sputtering method, an ALD method (including a thermal ALD method or a PEALD method), a CVD method, or a vacuum evaporation method, for example. Alternatively, the sacrificial film158Rf and the mask film159Rf may be formed by the above-described wet process.

The sacrificial film158Rf and the mask film159Rf are formed at a temperature lower than the upper temperature limit of the organic compound film103Rf. The typical substrate temperatures in formation of the sacrificial film158Rf and the mask film159Rf are each lower than or equal to 200° C., preferably lower than or equal to 150° C., further preferably lower than or equal to 120° C., still further preferably lower than or equal to 100° C., yet still further preferably lower than or equal to 80° C.

Although this embodiment shows an example where a mask film having a two-layer structure of the sacrificial film158Rf and the mask film159Rf is formed, a mask film may have a single-layer structure or a stacked-layer structure of three or more layers.

Providing the sacrificial layer over the organic compound film103Rf can reduce damage to the organic compound film103Rf in the manufacturing process of the light-emitting apparatus, resulting in an increase in reliability of the light-emitting device.

As the sacrificial film158Rf, a film that is highly resistant to the process conditions for the organic compound film103Rf, specifically, a film having high etching selectivity with respect to the organic compound film103Rf is used. For the mask film159Rf, a film having high etching selectivity with respect to the sacrificial film158Rf is used.

The sacrificial film158Rf and the mask film159Rf are preferably films that can be removed by a wet etching method. Using a wet etching method can reduce damage to the organic compound film103Rf in processing of the sacrificial film158Rf and the mask film159Rf, as compared to the case of using a dry etching method.

In the case where a wet etching method is employed, it is particularly preferable to use an acidic chemical solution. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used.

As each of the sacrificial film158Rf and the mask film159Rf, one or more of a metal film, an alloy film, a metal oxide film, a semiconductor film, an organic insulating film, and an inorganic insulating film, for example, can be used.

When a film containing a material having a property of blocking ultraviolet rays is used as each of the sacrificial film and the mask film, the organic compound layer can be inhibited from being irradiated with ultraviolet rays in a light exposure step, for example. The organic compound layer is inhibited from being damaged by ultraviolet rays, so that the reliability of the light-emitting device can be improved.

Note that the same effect is obtained when a film containing a material having a property of blocking ultraviolet rays is used for an after-mentioned inorganic insulating film125f.

For each of the sacrificial film158Rf and the mask film159Rf, it is preferable to use a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, titanium, aluminum, yttrium, zirconium, or tantalum or an alloy material containing any of the metal materials, for example. It is particularly preferable to use a low-melting-point material such as aluminum or silver.

The sacrificial film158Rf and the mask film159Rf can each be formed using a metal oxide such as an In—Ga—Zn oxide, an indium oxide, an In—Zn oxide, an In—Sn oxide, an indium titanium oxide (In—Ti oxide), an indium tin zinc oxide (In—Sn—Zn oxide), an indium titanium zinc oxide (In—Ti—Zn oxide), an indium gallium tin zinc oxide (In—Ga—Sn—Zn oxide), or an indium tin oxide containing silicon.

The sacrificial film158Rf and the mask film159Rf are preferably formed using a semiconductor material such as silicon or germanium, for example, for excellent compatibility with a semiconductor manufacturing process. An oxide or a nitride of the semiconductor material can be used. A non-metallic material such as carbon or a compound thereof can be used. A metal such as titanium, tantalum, tungsten, chromium, or aluminum or an alloy containing at least one of these metals can be used. Alternatively, an oxide containing the above-described metal, such as titanium oxide or chromium oxide, or a nitride such as titanium nitride, chromium nitride, or tantalum nitride can be used.

As each of the sacrificial film158Rf and the mask film159Rf, any of a variety of inorganic insulating films can be used. In particular, an oxide insulating film is preferable because its adhesion to the organic compound film103Rf is higher than that of a nitride insulating film. For example, an inorganic insulating material such as aluminum oxide, hafnium oxide, or silicon oxide can be used for the sacrificial film158Rf and the mask film159Rf As the sacrificial film158Rf and the mask film159Rf, aluminum oxide films can be formed by an ALD method, for example. An ALD method is preferably used, in which case damage to a base (in particular, the organic compound layer) can be reduced.

One or both of the sacrificial film158Rf and the mask film159Rf may be formed using an organic material. For example, as the organic material, a material that can be dissolved in a solvent chemically stable with respect to at least the uppermost film of the organic compound film103Rf may be used. Specifically, a material that will be dissolved in water or an alcohol can be suitably used. In forming a film of such a material, it is preferable to apply the material dissolved in a solvent such as water or an alcohol by a wet process and then perform heat treatment for evaporating the solvent. At this time, the heat treatment is preferably performed in a reduced-pressure atmosphere, in which case the solvent can be removed at a low temperature in a short time and thermal damage to the organic compound film103Rf can be reduced accordingly.

The sacrificial film158Rf and the mask film159Rf may be formed using an organic resin such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, an alcohol-soluble polyamide resin, or a fluorine resin like perfluoropolymer.

For example, an organic film (e.g., a PVA film) formed by an evaporation method or any of the above wet processes can be used as the sacrificial film158Rf, and an inorganic film (e.g., a silicon nitride film) formed by a sputtering method can be used as the mask film159Rf.

Subsequently, a resist mask190R is formed over the mask film159Rf as illustrated inFIG.6C. The resist mask190R can be formed by application of a photosensitive material (photoresist), light exposure, and development.

The resist mask190R may be formed using either a positive resist material or a negative resist material.

The resist mask190R is provided at a position overlapping with the conductive layer152R. The resist mask190R is preferably provided also at a position overlapping with the conductive layer152C. This can inhibit the conductive layer152C from being damaged during the manufacturing process of the light-emitting apparatus. Note that the resist mask190R is not necessarily provided over the conductive layer152C. The resist mask190R is preferably provided to cover the area from the end portion of the organic compound film103Rf to the end portion of the conductive layer152C (the end portion closer to the organic compound film103Rf), as illustrated in the cross-sectional view taken along the line B1-B2 inFIG.6C.

Next, as illustrated inFIG.6D, part of the mask film159Rf is removed using the resist mask190R, whereby the mask layer159R is formed. The mask layer159R remains over the conductive layers152R and152C. After that, the resist mask190R is removed. Then, part of the sacrificial film158Rf is removed using the mask layer159R as a mask (also referred to as a hard mask), whereby the sacrificial layer158R is formed.

Each of the sacrificial film158Rf and the mask film159Rf can be processed by a wet etching method or a dry etching method. The sacrificial film158Rf and the mask film159Rf are preferably processed by wet etching.

Using a wet etching method can reduce damage to the organic compound film103Rf in processing of the sacrificial film158Rf and the mask film159Rf, as compared to the case of using a dry etching method. In the case of using a wet etching method, it is preferable to use a developer, an aqueous solution of tetramethylammonium hydroxide (TMAH), dilute hydrofluoric acid, oxalic acid, phosphoric acid, acetic acid, nitric acid, or a chemical solution containing a mixed solution of any of these acids, for example.

Since the organic compound film103Rf is not exposed in the processing of the mask film159Rf, the range of choice for a processing method for the mask film159Rf is wider than that for the sacrificial film158Rf. Specifically, even in the case where a gas containing oxygen is used as the etching gas in the processing of the mask film159Rf, deterioration of the organic compound film103Rf can be inhibited.

In the case where a wet etching method is employed, it is particularly preferable to use an acidic chemical solution. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used.

In the case of using a dry etching method to process the sacrificial film158Rf, deterioration of the organic compound film103Rf can be inhibited by not using a gas containing oxygen as the etching gas. In the case of using a dry etching method, it is preferable to use a gas containing CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, or a Group 18 element such as He, for example, as the etching gas.

The resist mask190R can be removed by a method similar to that for the resist mask191. At this time, the sacrificial film158Rf is positioned on the outermost surface, and the organic compound film103Rf is not exposed; thus, the organic compound film103Rf can be inhibited from being damaged in the step of removing the resist mask190R. In addition, the range of choice for the method for removing the resist mask190R can be widened.

Next, as illustrated inFIG.6D, the organic compound film103Rf is processed, so that the organic compound layer103R is formed. For example, part of the organic compound film103Rf is removed using the mask layer159R and the sacrificial layer158R as a hard mask, whereby the organic compound layer103R is formed.

Accordingly, as illustrated inFIG.6D, the stacked-layer structure of the organic compound layer103R, the sacrificial layer158R, and the mask layer159R remains over the conductive layer152R. The conductive layers152G and152B are exposed.

The organic compound film103Rf can be processed by dry etching or wet etching. In the case where the processing is performed by dry etching, for example, an etching gas containing oxygen can be used. When the etching gas contains oxygen, the etching rate can be increased. Thus, the etching can be performed under a low-power condition while an adequately high etching rate is maintained. Accordingly, damage to the organic compound film103Rf can be inhibited. Furthermore, a defect such as attachment of a reaction product generated during the etching can be inhibited.

An etching gas that does not contain oxygen may be used. In that case, deterioration of the organic compound film103Rf can be inhibited, for example.

As described above, in one embodiment of the present invention, the mask layer159R is formed in the following manner: the resist mask190R is formed over the mask film159Rf and part of the mask film159Rf is removed using the resist mask190R. After that, part of the organic compound film103Rf is removed using the mask layer159R as a hard mask, so that the organic compound layer103R is formed. In other words, the organic compound layer103R is formed by processing the organic compound film103Rf by a photolithography method. Note that part of the organic compound film103Rf may be removed using the resist mask190R. Then, the resist mask190R may be removed.

Here, hydrophobization treatment for the conductive layer152G may be performed as necessary. At the time of processing the organic compound film103Rf, a surface of the conductive layer152G changes to have hydrophilic properties in some cases, for example. The hydrophobization treatment for the conductive layer152G, for example, can increase the adhesion between the conductive layer152G and a layer to be formed in a later step (which is the organic compound layer103G here) and inhibit film peeling.

Next, as illustrated inFIG.7A, an organic compound film103Gf to be the organic compound layer103G is formed over the conductive layer152G, the conductive layer152B, the mask layer159R, and the insulating layer175.

The organic compound film103Gf can be formed by a method similar to that for forming the organic compound film103Rf. The organic compound film103Gf can have a structure similar to that of the organic compound film103Rf.

Then, as illustrated inFIG.7A, a sacrificial film158Gf to be a sacrificial layer158G and a mask film159Gf to be a mask layer159G are sequentially formed over the organic compound film103Gf and the mask layer159R. After that, a resist mask190G is formed. The materials and the formation methods of the sacrificial film158Gf and the mask film159Gf are similar to those for the sacrificial film158Rf and the mask film159Rf. The material and the formation method of the resist mask190G are similar to those for the resist mask190R.

The resist mask190G is provided at a position overlapping with the conductive layer152G.

Subsequently, as illustrated inFIG.7B, part of the mask film159Gf is removed using the resist mask190G, whereby the mask layer159G is formed. The mask layer159G remains over the conductive layer152G. After that, the resist mask190G is removed. Then, part of the sacrificial film158Gf is removed using the mask layer159G as a mask, whereby the sacrificial layer158G is formed. Next, the organic compound film103Gf is processed to form the organic compound layer103G. For example, part of the organic compound film103Gf is removed using the mask layer159G and the sacrificial layer158G as a hard mask to form the organic compound layer103G.

Accordingly, as illustrated inFIG.7B, the stacked-layer structure of the organic compound layer103G, the sacrificial layer158G, and the mask layer159G remains over the conductive layer152G. The mask layer159R and the conductive layer152B are exposed.

Hydrophobization treatment for the conductive layer152B may be performed, for example.

Subsequently, as illustrated inFIGS.7C and7D, a sacrificial layer158B, a mask layer159B, and the organic compound layer103B are formed from a sacrificial film158Bf, a mask film159Bf, and the organic compound film103Bf, respectively, using a resist mask190B. For the formation methods of the sacrificial layer158B, the mask layer159B, and the organic compound layer103B, the description for the organic compound layer103G can be referred to.

Note that the side surfaces of the organic compound layers103R,103G, and103B are preferably perpendicular or substantially perpendicular to their formation surfaces. For example, the angle between the formation surfaces and these side surfaces is preferably greater than or equal to 600 and less than or equal to 90°.

The distance between two adjacent layers among the organic compound layers103R,103G, and103B, which are formed by a photolithography method as described above, can be reduced to less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, less than or equal to 2 μm, or less than or equal to 1 μm. Here, the distance can be specified, for example, by a distance between opposite end portions of two adjacent layers among the organic compound layers103R,103G, and103B. Reducing the distance between the island-shaped organic compound layers can provide a light-emitting apparatus having a high resolution and a high aperture ratio. In addition, the distance between the first electrodes of adjacent light-emitting devices can also be shortened to for example, less than or equal to 10 μm, less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, or less than or equal to 2 μm. Note that the distance between the first electrodes of adjacent light-emitting devices is preferably greater than or equal to 2 μm and less than or equal to 5 μm.

This embodiment shows an example where the mask layers159R,159G, and159B are removed; however, it is possible that the mask layers159R,159G, and159B are not removed. For example, in the case where the mask layers159R,159G, and159B contain the above-described material having a property of blocking ultraviolet rays, the procedure preferably proceeds to the next step without removing the mask layers159R,159G, and159B, in which case the organic compound layer can be protected from ultraviolet rays.

The step of removing the mask layers can be performed by a method similar to that for the step of processing the mask layers. Specifically, by using a wet etching method, damage applied to the organic compound layers103R,103G, and103B at the time of removing the mask layers can be reduced as compared to the case of using a dry etching method.

The mask layers may be removed by being dissolved in a solvent such as water or an alcohol. Examples of an alcohol include ethyl alcohol, methyl alcohol, isopropyl alcohol (IPA), and glycerin.

After the mask layers are removed, drying treatment may be performed in order to remove water included in the organic compound layers103R,103G, and103B and water adsorbed on the surfaces of the organic compound layers103R,103G, and103B. For example, heat treatment in an inert gas atmosphere or a reduced-pressure atmosphere can be performed. The heat treatment can be performed at a substrate temperature of higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., further preferably higher than or equal to 70° C. and lower than or equal to 120° C. The heat treatment is preferably performed in a reduced-pressure atmosphere, in which case drying at a lower temperature is possible.

Next, as illustrated inFIG.8B, the inorganic insulating film125fto be the inorganic insulating layer125is formed to cover the organic compound layers103R,103G, and103B and the sacrificial layers158R,158G, and158B.

As described later, an insulating film to be the insulating layer127is to be formed in contact with the top surface of the inorganic insulating film125f. Thus, the top surface of the inorganic insulating film125fpreferably has a high affinity for the material used for the insulating film to be the insulating layer127(e.g., a photosensitive resin composition containing an acrylic resin). To improve the affinity, surface treatment may be performed on the top surface of the inorganic insulating film125f. Specifically, the surface of the inorganic insulating film125fis preferably made hydrophobic (or its hydrophobic property is preferably improved). For example, it is preferable to perform the treatment using a silylation agent such as hexamethyldisilazane (HMDS). By making the top surface of the inorganic insulating film125fhydrophobic in such a manner, an insulating film127fcan be formed with favorable adhesion.

Then, as illustrated inFIG.8C, the insulating film127fto be the insulating layer127is formed over the inorganic insulating film125f.

The inorganic insulating film125fand the insulating film127fare preferably formed by a formation method that causes less damage to the organic compound layers103R,103G, and103B. The inorganic insulating film125f, which is formed in contact with the side surfaces of the organic compound layers103R,103G, and103B, is particularly preferably formed by a formation method that causes less damage to the organic compound layers103R,103G, and103B than the method of forming the insulating film127f.

Each of the insulating films125fand127fis formed at a temperature lower than the upper temperature limit of the organic compound layers103R,103G, and103B. When the insulating film125fis formed at a high substrate temperature, the formed insulating film125f, even with a small thickness, can have a low impurity concentration and a high barrier property against at least one of water and oxygen.

The substrate temperature at the time of forming the inorganic insulating film125fand the insulating film127fis preferably higher than or equal to 60° C., higher than or equal to 80° C., higher than or equal to 100° C., or higher than or equal to 120° C. and lower than or equal to 200° C., lower than or equal to 180° C., lower than or equal to 160° C., lower than or equal to 150° C., or lower than or equal to 140° C.

As the inorganic insulating film125f, an insulating film having a thickness of greater than or equal to 3 nm, greater than or equal to 5 nm, or greater than or equal to 10 nm and less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, or less than or equal to 50 nm is preferably formed in the above-described range of the substrate temperature.

The inorganic insulating film125fis preferably formed by an ALD method, for example. An ALD method is preferably used, in which case deposition damage is reduced and a film with good coverage can be formed. As the inorganic insulating film125f, an aluminum oxide film is preferably formed by an ALD method, for example.

Alternatively, the inorganic insulating film125fmay be formed by a sputtering method, a CVD method, or a PECVD method, each of which has a higher deposition rate than an ALD method. In that case, a highly reliable light-emitting apparatus can be manufactured with high productivity.

The insulating film127fis preferably formed by the aforementioned wet process. The insulating film127fis preferably formed by spin coating using a photosensitive material, for example, and specifically preferably formed using a photosensitive resin composition containing an acrylic resin.

The insulating film127fis preferably formed using a resin composition containing a polymer, an acid-generating agent, and a solvent, for example. The polymer is formed using one or more kinds of monomers and has a structure where one or more kinds of structural units (also referred to as building blocks) are repeated regularly or irregularly. As the acid-generating agent, one or both of a compound that generates an acid by light irradiation and a compound that generates an acid by heating can be used. The resin composition may also include one or more of a photosensitizing agent, a sensitizer, a catalyst, an adhesive aid, a surface-active agent, and an antioxidant.

Heat treatment (also referred to as prebaking) is preferably performed after the insulating film127fis formed. The heat treatment is performed at a temperature lower than the upper temperature limit of the organic compound layers103R,103G, and103B. The substrate temperature in the heat treatment is preferably higher than or equal to 50° C. and lower than or equal to 200° C., further preferably higher than or equal to 60° C. and lower than or equal to 150° C., still further preferably higher than or equal to 70° C. and lower than or equal to 120° C. Accordingly, the solvent contained in the insulating film127fcan be removed.

Then, part of the insulating film127fis exposed to visible light or ultraviolet rays. Here, when a positive photosensitive resin composition containing an acrylic resin is used for the insulating film127f, a region where the insulating layer127is not formed in a later step is irradiated with visible light or ultraviolet rays. The insulating layer127is formed in regions that are interposed between any two of the conductive layers152R,152G, and152B and around the conductive layer152C. Thus, the top surfaces of the conductive layers152R,152G,152B, and152C are irradiated with visible light or ultraviolet rays. Note that when a negative photosensitive material is used for the insulating film127f, the region where the insulating layer127is to be formed is irradiated with visible light or ultraviolet rays.

The width of the insulating layer127formed later can be controlled in accordance with the exposed region of the insulating film127f. In this embodiment, processing is performed such that the insulating layer127includes a portion overlapping with the top surface of the conductive layer151.

Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is provided as one or both of the sacrificial layer158(the sacrificial layers158R,158G, and158B) and the inorganic insulating film125f, diffusion of oxygen into the organic compound layers103R,103G, and103B can be inhibited. When the organic compound layer is irradiated with light (visible light or ultraviolet rays), the organic compound contained in the organic compound layer is brought into an excited state and a reaction between the organic compound and oxygen in the atmosphere is promoted in some cases. Specifically, when the organic compound layer is irradiated with light (visible light or ultraviolet rays) in an atmosphere containing oxygen, oxygen might be bonded to the organic compound contained in the organic compound layer. By providing the sacrificial layer158and the inorganic insulating film125fover the island-shaped organic compound layer, bonding of oxygen in the atmosphere to the organic compound contained in the organic compound layer can be inhibited.

Next, as illustrated inFIG.9A, development is performed to remove the exposed region of the insulating film127f, whereby an insulating layer127ais formed. The insulating layer127ais formed in regions that are interposed between any two of the conductive layers152R,152G, and152B and a region surrounding the conductive layer152C. Here, when an acrylic resin is used for the insulating film127f, an alkaline solution, such as TMAH, can be used as a developer.

Next, as illustrated inFIG.9B, etching treatment is performed using the insulating layer127aas a mask to remove part of the inorganic insulating film125fand reduce the thickness of part of the sacrificial layers158R,158G, and158B. Thus, the inorganic insulating layer125is formed under the insulating layer127a. Note that the etching treatment for processing the inorganic insulating film125fusing the insulating layer127aas a mask may be hereinafter referred to as first etching treatment.

In other words, the sacrificial layers158R,158G, and158B are not removed completely by the first etching treatment, and the etching treatment is stopped when the thicknesses of the sacrificial layers158R,158G, and158B are reduced. The sacrificial layers158R,158G, and158B remain over the corresponding organic compound layers103R,103G, and103B in this manner, whereby the organic compound layers103R,103G, and103B can be prevented from being damaged by treatment in a later step.

The first etching treatment can be performed by dry etching or wet etching. Note that the inorganic insulating film125fis preferably formed using a material similar to that for the sacrificial layers158R,158G, and158B, in which case the processing of the inorganic insulating film125fand thinning of the exposed part of the sacrificial layer158can be concurrently performed by the first etching treatment.

By etching using the insulating layer127awith a tapered side surface as a mask, the side surface of the inorganic insulating layer125and upper edge portions of the side surfaces of the sacrificial layers158R,158G, and158B can be made to have a tapered shape relatively easily.

In the case where the first etching treatment is performed by dry etching, for example, a chlorine-based gas can be used. As the chlorine-based gas, one of Cl2, BCl3, SiCl4, CCl4, and the like or a mixture of two or more of them can be used. Moreover, one of an oxygen gas, a hydrogen gas, a helium gas, an argon gas, and the like or a mixture of two or more of them can be added as appropriate to the chlorine-based gas. By the dry etching, the thin regions of the sacrificial layers158R,158G, and158B can be formed with favorable in-plane uniformity.

The first etching treatment can be performed by wet etching, for example. The use of wet etching can reduce damage to the organic compound layers103R,103G, and103B, as compared to the case of using dry etching.

The wet etching is preferably performed using an acidic chemical solution. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used.

The wet etching can be performed using an alkaline solution. For example, TMAH, which is an alkaline solution, can be used for the wet etching of an aluminum oxide film. In that case, puddle wet etching can be performed.

Then, heat treatment (also referred to as post-baking) is performed. The heat treatment can change the insulating layer127ainto the insulating layer127having a tapered side surface (FIG.9C). The heat treatment is performed at a temperature lower than the upper temperature limit of the organic compound layer. The heat treatment can be performed at a substrate temperature higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., further preferably higher than or equal to 70° C. and lower than or equal to 130° C. The heating atmosphere may be an air atmosphere or an inert gas atmosphere. Moreover, the heating atmosphere may be an atmospheric-pressure atmosphere or a reduced-pressure atmosphere. The substrate temperature in the heat treatment of this step is preferably higher than that in the heat treatment (prebaking) after the formation of the insulating film127f.

The heat treatment can improve adhesion between the insulating layer127and the inorganic insulating layer125and increase corrosion resistance of the insulating layer127. Furthermore, owing to the change in shape of the insulating layer127a, an end portion of the inorganic insulating layer125can be covered with the insulating layer127.

When the sacrificial layers158R,158G, and158B are not completely removed by the first etching treatment and the thinned sacrificial layers158R,158G, and158B are left, the organic compound layers103R,103G, and103B can be prevented from being damaged and deteriorating in the heat treatment. This increases the reliability of the light-emitting device.

Next, as illustrated inFIG.10A, etching treatment is performed using the insulating layer127as a mask to remove parts of the sacrificial layers158R,158G, and158B. At this time, part of the inorganic insulating layer125is also removed in some cases. By the etching treatment, openings are formed in the sacrificial layers158R,158G, and158B, and the top surfaces of the organic compound layers103R,103G, and103B and the conductive layer152C are exposed in the openings. Note that the etching treatment for exposing the organic compound layers103R,103G, and103B using the insulating layer127as a mask may be hereinafter referred to as second etching treatment.

The second etching treatment is performed by wet etching. The use of a wet etching method can reduce damage to the organic compound layers103R,103G, and103B, as compared to the case of using a dry etching method. The wet etching can be performed using an acidic chemical solution or an alkaline solution as in the case of the first etching treatment.

Heat treatment may be performed after the organic compound layers103R,103G, and103B are partly exposed. By the heat treatment, water included in the organic compound layer and water adsorbed on the surface of the organic compound layer, for example, can be removed. The shape of the insulating layer127may be changed by the heat treatment. Specifically, the insulating layer127may be widened to cover at least one of the end portion of the inorganic insulating layer125, the end portions of the sacrificial layers158R,158G, and158B, and the top surfaces of the organic compound layers103R,103G, and103B.

FIG.10Aillustrates an example where part of the end portion of the sacrificial layer158G (specifically a tapered portion formed by the first etching treatment) is covered with the insulating layer127and a tapered portion formed by the second etching treatment is exposed (seeFIG.4A).

The insulating layer127may cover the entire end portion of the sacrificial layer158G. For example, the end portion of the insulating layer127may droop to cover the end portion of the sacrificial layer158G. As another example, the end portion of the insulating layer127may be in contact with the top surface of at least one of the organic compound layers103R,103G, and103B.

Next, as illustrated inFIG.10B, a common electrode155is formed over the organic compound layers103R,103G, and103B, the conductive layer152C, and the insulating layer127. The common electrode155can be formed by a sputtering method, a vacuum evaporation method, or the like. Alternatively, the common electrode155may be formed by stacking a film formed by an evaporation method and a film formed by a sputtering method.

Next, as illustrated inFIG.10C, the protective layer131is formed over the common electrode155. The protective layer131can be formed by a vacuum evaporation method, a sputtering method, a CVD method, an ALD method, or the like.

Then, the substrate120is bonded to the protective layer131using the resin layer122, whereby the light-emitting apparatus can be manufactured. In the method for manufacturing the light-emitting apparatus of one embodiment of the present invention, the insulating layer156is provided to include a region overlapping with the side surface of the conductive layer151and the conductive layer152is formed to cover the conductive layer151and the insulating layer156as described above. This can increase the yield of the light-emitting apparatus and inhibit generation of defects.

As described above, in the method for manufacturing the light-emitting apparatus of one embodiment of the present invention, the island-shaped organic compound layers103R,103G, and103B are formed not by using a fine metal mask but by processing a film formed on the entire surface; thus, the island-shaped layers can be formed to have a uniform thickness. Consequently, a high-resolution light-emitting apparatus or a light-emitting apparatus with a high aperture ratio can be obtained. Furthermore, even when the resolution or the aperture ratio is high and the distance between the subpixels is extremely short, the organic compound layers103R,103G, and103B can be inhibited from being in contact with each other in the adjacent subpixels. As a result, generation of a leakage current between the subpixels can be inhibited. This can prevent crosstalk, so that a light-emitting apparatus with extremely high contrast can be obtained. Moreover, even a light-emitting apparatus that includes tandem light-emitting devices formed by a photolithography method can have favorable characteristics.

In this embodiment, the light-emitting apparatus of one embodiment of the present invention will be described with reference toFIGS.11A to11GandFIGS.12A to121.

Pixel Layout

In this embodiment, pixel layouts different from that inFIGS.3A and3Bwill be mainly described. There is no particular limitation on the arrangement of subpixels, and a variety of methods can be employed. Examples of the arrangement of subpixels include stripe arrangement, S-stripe arrangement, matrix arrangement, delta arrangement, Bayer arrangement, and PenTile arrangement.

In this embodiment, the top surface shapes of the subpixels illustrated in the diagrams correspond to top surface shapes of light-emitting regions.

Examples of a top surface shape of the subpixel include polygons such as a triangle, a tetragon (including a rectangle and a square), and a pentagon; polygons with rounded corners; an ellipse; and a circle.

The circuit constituting the subpixel is not necessarily placed within the dimensions of the subpixel illustrated in the diagrams and may be placed outside the subpixel.

The pixel178illustrated inFIG.11Aemploys S-stripe arrangement. The pixel178illustrated inFIG.11Aincludes three subpixels, the subpixel110R, the subpixel110G, and the subpixel110B.

The pixel178illustrated inFIG.11Bincludes the subpixel110R whose top surface has a rough trapezoidal shape with rounded corners, the subpixel110G whose top surface has a rough triangle shape with rounded corners, and the subpixel110B whose top surface has a rough tetragonal or rough hexagonal shape with rounded corners. The subpixel110R has a larger light-emitting area than the subpixel110G. In this manner, the shapes and sizes of the subpixels can be determined independently. For example, the size of a subpixel including a light-emitting device with higher reliability can be smaller.

Pixels124aand124billustrated inFIG.11Cemploy PenTile arrangement.FIG.11Cshows an example where the pixels124aincluding the subpixels110R and110G and the pixels124bincluding the subpixels110G and110B are alternately arranged.

The pixels124aand124billustrated inFIGS.11D to11Femploy delta arrangement. The pixel124aincludes two subpixels (the subpixels110R and110G) in the upper row (first row) and one subpixel (the subpixel110B) in the lower row (second row). The pixel124bincludes one subpixel (the subpixel110B) in the upper row (first row) and two subpixels (the subpixels110R and110G) in the lower row (second row).

FIG.11Dillustrates an example where each subpixel has a rough tetragonal top surface with rounded corners.FIG.11Eillustrates an example where each subpixel has a circular top surface.FIG.11Fillustrates an example where each subpixel has a rough hexagonal top surface with rounded corners.

InFIG.11F, each subpixel is placed inside one of close-packed hexagonal regions. Focusing on one of the subpixels, the subpixel is placed so as to be surrounded by six subpixels. The subpixels are arranged such that subpixels that emit light of the same color are not adjacent to each other. For example, focusing on the subpixel110R, the subpixel110R is surrounded by three subpixels110G and three subpixels110B that are alternately arranged.

FIG.11Gshows an example where subpixels of different colors are arranged in a zigzag manner. Specifically, the positions of the top sides of two subpixels arranged in the column direction (e.g., the subpixels110R and110G or the subpixels110G and110B) are not aligned in the top view.

In the pixels illustrated inFIGS.11A to11G, for example, it is preferred that the subpixel110R be a subpixel R emitting red light, the subpixel110G be a subpixel G emitting green light, and the subpixel110B be a subpixel B emitting blue light. Note that the structures of the subpixels are not limited thereto, and the colors and the order of the subpixels can be determined as appropriate. For example, the subpixel110G may be the subpixel R emitting red light, and the subpixel110R may be the subpixel G emitting green light.

In a photolithography method, as a pattern to be formed by processing becomes finer, the influence of light diffraction becomes more difficult to ignore; therefore, the fidelity in transferring a photomask pattern by light exposure is degraded, and it becomes difficult to process a resist mask into a desired shape. Thus, a pattern with rounded corners is likely to be formed even with a rectangular photomask pattern. Consequently, the top surface of a subpixel may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like.

Furthermore, in the method for manufacturing the light-emitting apparatus of one embodiment of the present invention, the organic compound layer is processed into an island shape with the use of a resist mask. A resist film formed over the organic compound layer needs to be cured at a temperature lower than the upper temperature limit of the organic compound layer. Therefore, the resist film is insufficiently cured in some cases depending on the upper temperature limit of the material of the organic compound layer and the curing temperature of the resist material. An insufficiently cured resist film may have a shape different from a desired shape by processing. As a result, the top surface of the organic compound layer may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like. For example, when a resist mask with a square top surface is intended to be formed, a resist mask with a circular top surface may be formed, and the top surface of the organic compound layer may be circular.

To obtain a desired top surface shape of the organic compound layer, a technique of correcting a mask pattern in advance so that a transferred pattern agrees with a design pattern (an optical proximity correction (OPC) technique) may be used. Specifically, with the OPC technique, a pattern for correction is added to a corner portion of a figure on a mask pattern, for example.

As illustrated inFIGS.12A to121, the pixel can include four types of subpixels.

FIG.12Aillustrates an example where each subpixel has a rectangular top surface.FIG.12Billustrates an example where each subpixel has a top surface shape formed by combining two half circles and a rectangle.FIG.12Cillustrates an example where each subpixel has an elliptical top surface.

FIG.12Dillustrates an example where each subpixel has a square top surface.FIG.12Eillustrates an example where each subpixel has a substantially square top surface with rounded corners.FIG.12Fillustrates an example where each subpixel has a circular top surface.

FIGS.12Gand 12H each illustrate an example where one pixel178is composed of two rows and three columns.

The pixel178illustrated inFIG.12Gincludes three subpixels (the subpixels110R,110G, and110B) in the upper row (first row) and one subpixel (a subpixel110W) in the lower row (second row). In other words, the pixel178includes the subpixel110R in the left column (first column), the subpixel110G in the middle column (second column), the subpixel110B in the right column (third column), and the subpixel110W across these three columns.

The pixel178illustrated inFIG.12Hincludes three subpixels (the subpixels110R,110G, and110B) in the upper row (first row) and three of the subpixels110W in the lower row (second row). In other words, the pixel178includes the subpixels110R and110W in the left column (first column), the subpixels110G and110W in the middle column (second column), and the subpixels110B and110W in the right column (third column). Matching the positions of the subpixels in the upper row and the lower row as illustrated inFIG.12Henables dust that would be produced in the manufacturing process, for example, to be removed efficiently. Thus, a light-emitting apparatus having high display quality can be provided.

In the pixel178illustrated inFIGS.12Gand 12H, the subpixels110R,110G, and110B are arranged in a stripe pattern, whereby the display quality can be improved.

FIG.12Iillustrates an example where one pixel178is composed of three rows and two columns.

The pixel178illustrated inFIG.12Iincludes the subpixel110R in the upper row (first row), the subpixel110G in the middle row (second row), the subpixel110B across the first row and the second row, and one subpixel (the subpixel110W) in the lower row (third row). In other words, the pixel178includes the subpixels110R and110G in the left column (first column), the subpixel110B in the right column (second column), and the subpixel110W across these two columns.

In the pixel178illustrated inFIG.12I, the subpixels110R,110G, and110B are arranged in what is called an S-stripe pattern, whereby the display quality can be improved.

The pixel178illustrated in each ofFIGS.12A to12Iis composed of four subpixels, which are the subpixels110R,110G,110B, and110W. For example, the subpixel110R can be a subpixel emitting red light, the subpixel110G can be a subpixel emitting green light, the subpixel110B can be a subpixel emitting blue light, and the subpixel110W can be a subpixel emitting white light. Note that at least one of the subpixels110R,110G,110B, and110W may be a subpixel emitting cyan light, magenta light, yellow light, or near-infrared light.

As described above, the pixel composed of the subpixels each including the light-emitting device can employ any of a variety of layouts in the light-emitting apparatus of one embodiment of the present invention.

This embodiment can be combined as appropriate with the other embodiments or an example. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.

In this embodiment, light-emitting apparatuses of embodiments of the present invention will be described.

The light-emitting apparatus in this embodiment can be a high-resolution light-emitting apparatus. Thus, the light-emitting apparatus in this embodiment can be used for display portions of information terminals (wearable devices) such as watch-type and bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device like a head mounted display (HMD) and a glasses-type AR device.

The light-emitting apparatus in this embodiment can be a high-definition light-emitting apparatus or a large-sized light-emitting apparatus. Accordingly, the light-emitting apparatus in this embodiment can be used for display portions of a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic devices with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.

FIG.13Ais a perspective view of a display module280. The display module280includes a light-emitting apparatus100A and an FPC290. Note that the light-emitting apparatus included in the display module280is not limited to the light-emitting apparatus100A and may be any of light-emitting apparatuses100B and100C described later.

FIG.13Bis a perspective view schematically illustrating the structure on the substrate291side. Over the substrate291, a circuit portion282, a pixel circuit portion283over the circuit portion282, and the pixel portion284over the pixel circuit portion283are stacked. In addition, a terminal portion285for connection to the FPC290is included in a portion not overlapping with the pixel portion284over the substrate291. The terminal portion285and the circuit portion282are electrically connected to each other through a wiring portion286formed of a plurality of wirings.

The pixel portion284includes a plurality of pixels284aarranged periodically. An enlarged view of one pixel284ais illustrated on the right side inFIG.13B. The pixels284acan employ any of the structures described in the above embodiments.FIG.13Billustrates an example where the pixel284ahas a structure similar to that of the pixel178illustrated inFIGS.3A and3B.

The pixel circuit portion283includes a plurality of pixel circuits283aarranged periodically.

One pixel circuit283ais a circuit that controls driving of a plurality of elements included in one pixel284a. One pixel circuit283acan be provided with three circuits each of which controls light emission of one light-emitting device. For example, the pixel circuit283acan include at least one selection transistor, one current control transistor (driving transistor), and a capacitor for one light-emitting device. A gate signal is input to a gate of the selection transistor, and a video signal is input to a source or a drain of the selection transistor. With such a structure, an active-matrix light-emitting apparatus is achieved.

The circuit portion282includes a circuit for driving the pixel circuits283ain the pixel circuit portion283. For example, the circuit portion282preferably includes one or both of a gate line driver circuit and a source line driver circuit. The circuit portion282may also include at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like.

The FPC290functions as a wiring for supplying a video signal, a power supply potential, or the like to the circuit portion282from the outside. An IC may be mounted on the FPC290.

The display module280can have a structure where one or both of the pixel circuit portion283and the circuit portion282are stacked below the pixel portion284; hence, the aperture ratio (effective display area ratio) of the display portion281can be significantly high. For example, the aperture ratio of the display portion281can be higher than or equal to 40% and lower than 100%, preferably higher than or equal to 50% and lower than or equal to 95%, further preferably higher than or equal to 60% and lower than or equal to 95%. Furthermore, the pixels284acan be arranged extremely densely and thus the display portion281can have a significantly high resolution. For example, the pixels284aare preferably arranged in the display portion281with a resolution of higher than or equal to 2000 ppi, further preferably higher than or equal to 3000 ppi, still further preferably higher than or equal to 5000 ppi, yet still further preferably higher than or equal to 6000 ppi, and lower than or equal to 20000 ppi or lower than or equal to 30000 ppi.

Such a display module280has an extremely high resolution, and thus can be suitably used for a VR device such as a HMD or a glasses-type AR device. For example, even in the case of a structure where the display portion of the display module280is seen through a lens, pixels of the extremely-high-resolution display portion281included in the display module280are prevented from being recognized when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module280can be suitably used for electronic devices including a relatively small display portion. For example, the display module280can be favorably used in a display portion of a wearable electronic device, such as a wrist watch.

The light-emitting apparatus100A illustrated inFIG.14Aincludes a substrate301, the light-emitting devices130R,130G, and130B, a capacitor240, and a transistor310.

The substrate301corresponds to the substrate291inFIGS.13A and13B. The transistor310includes a channel formation region in the substrate301. As the substrate301, a semiconductor substrate such as a single crystal silicon substrate can be used, for example. The transistor310includes part of the substrate301, a conductive layer311, a low-resistance region312, an insulating layer313, and an insulating layer314. The conductive layer311functions as a gate electrode. The insulating layer313is positioned between the substrate301and the conductive layer311and functions as a gate insulating layer. The low-resistance region312is a region where the substrate301is doped with an impurity, and functions as a source or a drain. The insulating layer314is provided to cover the side surface of the conductive layer311.

An element isolation layer315is provided between two adjacent transistors310to be embedded in the substrate301.

An insulating layer261is provided to cover the transistor310, and the capacitor240is provided over the insulating layer261.

The capacitor240includes a conductive layer241, a conductive layer245, and an insulating layer243positioned between the conductive layers241and245. The conductive layer241functions as one electrode of the capacitor240, the conductive layer245functions as the other electrode of the capacitor240, and the insulating layer243functions as a dielectric of the capacitor240.

The conductive layer241is provided over the insulating layer261and is embedded in an insulating layer254. The conductive layer241is electrically connected to one of the source and the drain of the transistor310through a plug271embedded in the insulating layer261. The insulating layer243is provided to cover the conductive layer241. The conductive layer245is provided in a region overlapping with the conductive layer241with the insulating layer243therebetween.

An insulating layer255is provided to cover the capacitor240. The insulating layer174is provided over the insulating layer255. The insulating layer175is provided over the insulating layer174. The light-emitting devices130R,130G, and130B are provided over the insulating layer175.FIG.14Aillustrates an example where the light-emitting devices130R,130G, and130B each have the stacked-layer structure illustrated inFIG.6A. An insulator is provided in regions between adjacent light-emitting devices. For example, inFIG.14A, the inorganic insulating layer125and the insulating layer127over the inorganic insulating layer125are provided in those regions.

The insulating layer156R is provided to include a region overlapping with the side surface of the conductive layer151R of the light-emitting device130R. The insulating layer156G is provided to include a region overlapping with the side surface of the conductive layer151G of the light-emitting device130G. The insulating layer156B is provided to include a region overlapping with the side surface of the conductive layer151B of the light-emitting device130B. The conductive layer152R is provided to cover the conductive layer151R and the insulating layer156R. The conductive layer152G is provided to cover the conductive layer151G and the insulating layer156G. The conductive layer152B is provided to cover the conductive layer151B and the insulating layer156B. The sacrificial layer158R is positioned over the organic compound layer103R of the light-emitting device130R. The sacrificial layer158G is positioned over the organic compound layer103G of the light-emitting device130G. The sacrificial layer158B is positioned over the organic compound layer103B of the light-emitting device130B.

Each of the conductive layers151R,151G, and151B is electrically connected to one of the source and the drain of the corresponding transistor310through a plug256embedded in the insulating layers243,255,174, and175, the conductive layer241embedded in the insulating layer254, and the plug271embedded in the insulating layer261. The top surface of the insulating layer175and the top surface of the plug256are level with or substantially level with each other. Any of a variety of conductive materials can be used for the plugs.

The protective layer131is provided over the light-emitting devices130R,130G, and130B. The substrate120is bonded to the protective layer131with the resin layer122. Embodiment 2 can be referred to for the details of the light-emitting device130and the components thereover up to the substrate120. The substrate120corresponds to the substrate292inFIG.13A.

FIG.14Billustrates a variation example of the light-emitting apparatus100A illustrated inFIG.14A. The light-emitting apparatus illustrated inFIG.14Bincludes the coloring layers132R,132G, and132B, and each of the light-emitting devices130includes a region overlapping with one of the coloring layers132R,132G, and132B. In the light-emitting apparatus illustrated inFIG.14B, the light-emitting device130can emit white light, for example. For example, the coloring layer132R, the coloring layer132G, and the coloring layer132B can transmit red light, green light, and blue light, respectively.

FIG.15is a perspective view of the light-emitting apparatus100B, andFIG.16Ais a cross-sectional view of the light-emitting apparatus100B.

In the light-emitting apparatus100B, a substrate352and a substrate351are bonded to each other. InFIG.15, the substrate352is denoted by a dashed line.

The light-emitting apparatus100B includes the pixel portion177, the connection portion140, a circuit356, a wiring355, and the like.FIG.15illustrates an example where an integrated circuit (IC)354and an FPC353are mounted on the light-emitting apparatus100B. Thus, the structure illustrated inFIG.15can be regarded as a display module including the light-emitting apparatus100B, the IC, and the FPC. Here, a light-emitting apparatus in which a substrate is equipped with a connector such as an FPC or mounted with an IC is referred to as a display module.

The connection portion140is provided outside the pixel portion177. The connection portion140can be provided along one side or a plurality of sides of the pixel portion177. The number of connection portions140may be one or more.FIG.15illustrates an example where the connection portion140is provided to surround the four sides of the display portion. In the connection portion140, a common electrode of a light-emitting device is electrically connected to a conductive layer, so that a potential can be supplied to the common electrode.

As the circuit356, a scan line driver circuit can be used, for example.

The wiring355has a function of supplying a signal and power to the pixel portion177and the circuit356. The signal and power are input to the wiring355from the outside through the FPC353or from the IC354.

FIG.15illustrates an example where the IC354is provided over the substrate351by a chip on glass (COG) method, a chip on film (COF) method, or the like. An IC including a scan line driver circuit, a signal line driver circuit, or the like can be used as the IC354, for example. Note that the light-emitting apparatus100B and the display module are not necessarily provided with an IC. Alternatively, the IC may be mounted on the FPC by a COF method, for example.

FIG.16Aillustrates an example of cross sections of part of a region including the FPC353, part of the circuit356, part of the pixel portion177, part of the connection portion140, and part of a region including an end portion of the light-emitting apparatus100B.

The light-emitting apparatus100B illustrated inFIG.16Aincludes a transistor201, a transistor205, the light-emitting device130R emitting red light, the light-emitting device130G emitting green light, the light-emitting device130B emitting blue light, and the like between the substrate351and the substrate352.

The stacked-layer structure of each of the light-emitting devices130R,130G, and130B is the same as that illustrated inFIG.6Aexcept for the structure of the pixel electrode. Embodiments 1 and 2 can be referred to for the details of the light-emitting devices.

The light-emitting device130R includes a conductive layer224R, the conductive layer151R over the conductive layer224R, and the conductive layer152R over the conductive layer151R. The light-emitting device130G includes a conductive layer224G, the conductive layer151G over the conductive layer224G, and the conductive layer152G over the conductive layer151G. The light-emitting device130B includes a conductive layer224B, the conductive layer151B over the conductive layer224B, and the conductive layer152B over the conductive layer151B. Here, the conductive layers224R,151R, and152R can be collectively referred to as the pixel electrode of the light-emitting device130R; the conductive layers151R and152R excluding the conductive layer224R can also be referred to as the pixel electrode of the light-emitting device130R. Similarly, the conductive layers224G,151G, and152G can be collectively referred to as the pixel electrode of the light-emitting device130G; the conductive layers151G and152G excluding the conductive layer224G can also be referred to as the pixel electrode of the light-emitting device130G. The conductive layers224B,151B, and152B can be collectively referred to as the pixel electrode of the light-emitting device130B; the conductive layers151B and152B excluding the conductive layer224B can also be referred to as the pixel electrode of the light-emitting device130B.

The conductive layer224R is connected to a conductive layer222bincluded in the transistor205through the opening provided in an insulating layer214. The end portion of the conductive layer151R is positioned on the outer side of the end portion of the conductive layer224R. The insulating layer156R is provided to include a region that is in contact with the side surface of the conductive layer151R, and the conductive layer152R is provided to cover the conductive layer151R and the insulating layer156R.

The conductive layers224G,151G, and152G and the insulating layer156G in the light-emitting device130G are not described in detail because they are respectively similar to the conductive layers224R,151R, and152R and the insulating layer156R in the light-emitting device130R; the same applies to the conductive layers224B,151B, and152B and the insulating layer156B in the light-emitting device130B.

The conductive layers224R,224G, and224B each have a depression portion covering an opening provided in the insulating layer214. A layer128is embedded in the depression portion.

The layer128has a function of filling the depression portions of the conductive layers224R,224G, and224B to obtain planarity. Over the conductive layers224R,224G, and224B and the layer128, the conductive layers151R,151G, and151B that are respectively electrically connected to the conductive layers224R,224G, and224B are provided. Thus, the regions overlapping with the depression portions of the conductive layers224R,224G, and224B can also be used as light-emitting regions, whereby the aperture ratio of the pixel can be increased.

The layer128may be an insulating layer or a conductive layer. Any of a variety of inorganic insulating materials, organic insulating materials, and conductive materials can be used for the layer128as appropriate. Specifically, the layer128is preferably formed using an insulating material and is particularly preferably formed using an organic insulating material. The layer128can be formed using an organic insulating material usable for the insulating layer127, for example.

The protective layer131is provided over the light-emitting devices130R,130G, and130B. The protective layer131and the substrate352are bonded to each other with an adhesive layer142. The substrate352is provided with a light-blocking layer157. A solid sealing structure, a hollow sealing structure, or the like can be employed to seal the light-emitting device130. InFIG.16A, a solid sealing structure is employed, in which a space between the substrate352and the substrate351is filled with the adhesive layer142. Alternatively, the space may be filled with an inert gas (e.g., nitrogen or argon), i.e., a hollow sealing structure may be employed. In that case, the adhesive layer142may be provided not to overlap with the light-emitting device. Alternatively, the space may be filled with a resin other than the frame-like adhesive layer142.

FIG.16Aillustrates an example where the connection portion140includes a conductive layer224C obtained by processing the same conductive film as the conductive layers224R,224G, and224B; the conductive layer151C obtained by processing the same conductive film as the conductive layers151R,151G, and151B; and the conductive layer152C obtained by processing the same conductive film as the conductive layers152R,152G, and152B. In the example illustrated inFIG.16A, the insulating layer156C is provided to include a region overlapping with the side surface of the conductive layer151C.

The light-emitting apparatus100B has a top-emission structure. Light from the light-emitting device is emitted toward the substrate352. For the substrate352, a material having a high visible-light-transmitting property is preferably used. The pixel electrode contains a material that reflects visible light, and the counter electrode (the common electrode155) contains a material that transmits visible light.

The transistor201and the transistor205are formed over the substrate351. These transistors can be fabricated using the same materials in the same steps.

An insulating layer211, an insulating layer213, an insulating layer215, and the insulating layer214are provided in this order over the substrate351. Part of the insulating layer211functions as a gate insulating layer of each transistor. Part of the insulating layer213functions as a gate insulating layer of each transistor. The insulating layer215is provided to cover the transistors. The insulating layer214is provided to cover the transistors and has a function of a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited and may each be one or more.

A material with low diffusibility of impurities such as water and hydrogen is preferably used for at least one of the insulating layers covering the transistors. This is because such an insulating layer can function as a barrier layer. Such a structure can effectively inhibit diffusion of impurities into the transistors from the outside and increase the reliability of the light-emitting apparatus.

An inorganic insulating film is preferably used as each of the insulating layers211,213, and215. As the inorganic insulating film, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film can be used, for example. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. A stack including two or more of the above insulating films may also be used.

An organic insulating layer is suitable as the insulating layer214functioning as a planarization layer. Examples of materials that can be used for the organic insulating layer include an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins. The insulating layer214may have a stacked-layer structure of an organic insulating layer and an inorganic insulating layer. The outermost layer of the insulating layer214preferably functions as an etching protective layer. This can inhibit formation of a recessed portion in the insulating layer214at the time of processing of the conductive layer224R,151R, or152R or the like. Alternatively, a recessed portion may be provided in the insulating layer214at the time of processing of the conductive layer224R,151R, or152R or the like.

Each of the transistors201and205includes a conductive layer221functioning as a gate, the insulating layer211functioning as a gate insulating layer, a conductive layer222aand a conductive layer222bfunctioning as a source and a drain, a semiconductor layer231, the insulating layer213functioning as a gate insulating layer, and a conductive layer223functioning as a gate. Here, a plurality of layers obtained by processing the same conductive film are shown with the same hatching pattern. The insulating layer211is positioned between the conductive layer221and the semiconductor layer231. The insulating layer213is positioned between the conductive layer223and the semiconductor layer231.

There is no particular limitation on the structure of the transistors included in the light-emitting apparatus of this embodiment. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor can be used. A top-gate transistor or a bottom-gate transistor can be used. Alternatively, gates may be provided above and below a semiconductor layer where a channel is formed.

The structure in which the semiconductor layer where a channel is formed is provided between two gates is used for the transistors201and205. The two gates may be connected to each other and supplied with the same signal to operate the transistor. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other of the two gates.

The semiconductor layer of the transistor preferably includes a metal oxide. That is, a transistor including a metal oxide in its channel formation region (hereinafter, also referred to as an OS transistor) is preferably used in the light-emitting apparatus of this embodiment.

Examples of an oxide semiconductor having crystallinity include a c-axis-aligned crystalline oxide semiconductor (CAAC-OS) and a nanocrystalline oxide semiconductor (nc-OS).

Alternatively, a transistor containing silicon in its channel formation region (a Si transistor) may be used. Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor containing low-temperature polysilicon (LTPS) in its semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and excellent frequency characteristics.

With the use of Si transistors such as LTPS transistors, a circuit required to be driven at a high frequency (e.g., a source driver circuit) can be formed on the same substrate as the display portion. This allows simplification of an external circuit mounted on the light-emitting apparatus and a reduction in costs of parts and mounting costs.

An OS transistor has much higher field-effect mobility than a transistor containing amorphous silicon. In addition, the OS transistor has an extremely low leakage current between a source and a drain in an off state (also referred to as an off-state current), and charge accumulated in a capacitor that is connected in series to the transistor can be held for a long period. Furthermore, the power consumption of the light-emitting apparatus can be reduced with the OS transistor.

To increase the luminance of the light-emitting device included in the pixel circuit, the amount of current fed through the light-emitting device needs to be increased. To increase the current amount, the source-drain voltage of a driving transistor included in the pixel circuit needs to be increased. An OS transistor has a higher breakdown voltage between a source and a drain than a Si transistor; hence, a high voltage can be applied between the source and the drain of the OS transistor. Therefore, when an OS transistor is used as the driving transistor in the pixel circuit, the amount of current flowing through the light-emitting device can be increased, so that the luminance of the light-emitting device can be increased.

When transistors operate in a saturation region, a change in a source-drain current relative to a change in a gate-source voltage can be smaller in an OS transistor than in a Si transistor. Accordingly, when an OS transistor is used as the driving transistor in the pixel circuit, a current flowing between the source and the drain can be set minutely by a change in a gate-source voltage; hence, the amount of current flowing through the light-emitting device can be controlled. Consequently, the number of gray levels expressed by the pixel circuit can be increased.

Regarding saturation characteristics of a current flowing when transistors operate in a saturation region, even in the case where the source-drain voltage of an OS transistor increases gradually, a more stable current (saturation current) can be fed through the OS transistor than through a Si transistor. Thus, by using an OS transistor as the driving transistor, a stable current can be fed through light-emitting devices even when the current-voltage characteristics of the light-emitting devices vary, for example. In other words, when the OS transistor operates in the saturation region, the source-drain current hardly changes with an increase in the source-drain voltage; hence, the luminance of the light-emitting device can be stable.

As described above, by using OS transistors as the driving transistors included in the pixel circuits, it is possible to inhibit black-level degradation, increase the luminance, increase the number of gray levels, and inhibit variations in light-emitting devices, for example.

It is particularly preferable that an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) be used for the semiconductor layer. It is preferable to use an oxide containing indium, tin, and zinc. It is preferable to use an oxide containing indium, gallium, tin, and zinc. It is preferable to use an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO). It is preferable to use an oxide containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) (also referred to as IAGZO).

When the semiconductor layer is an In-M-Zn oxide, the atomic proportion of In is preferably greater than or equal to the atomic proportion of Min the In-M-Zn oxide. Examples of the atomic ratio of the metal elements in such an In-M-Zn oxide are In:M:Zn=1:1:1, 1:1:1.2, 2:1:3, 3:1:2, 4:2:3, 4:2:4.1, 5:1:3, 5:1:6, 5:1:7, 5:1:8, 6:1:6, and 5:2:5 and a composition in the neighborhood of any of the above atomic ratios. Note that the vicinity of the atomic ratio includes ±30% of an intended atomic ratio.

For example, in the case of describing an atomic ratio of In:Ga:Zn=4:2:3 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 4, the atomic proportion of Ga is greater than or equal to 1 and less than or equal to 3 and the atomic proportion of Zn is greater than or equal to 2 and less than or equal to 4. In the case of describing an atomic ratio of In:Ga:Zn=5:1:6 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 5, the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than or equal to 5 and less than or equal to 7. In the case of describing an atomic ratio of In:Ga:Zn=1:1:1 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 1, the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than 0.1 and less than or equal to 2.

The transistors included in the circuit356and the transistors included in the pixel portion177may have the same structure or different structures. One structure or two or more kinds of structures may be employed for a plurality of transistors included in the circuit356. Similarly, one structure or two or more kinds of structures may be employed for a plurality of transistors included in the pixel portion177.

All transistors included in the pixel portion177may be OS transistors, or all transistors included in the pixel portion177may be Si transistors. Alternatively, some of the transistors included in the pixel portion177may be OS transistors and the others may be Si transistors.

For example, when both an LTPS transistor and an OS transistor are used in the pixel portion177, the light-emitting apparatus can have low power consumption and high driving capability. Note that a structure in which an LTPS transistor and an OS transistor are used in combination is referred to as LTPO in some cases. For example, it is preferable that an OS transistor be used as a transistor functioning as a switch for controlling electrical continuity between wirings and an LTPS transistor be used as a transistor for controlling a current.

For example, one transistor included in the pixel portion177functions as a transistor for controlling a current flowing through the light-emitting device and can be referred to as a driving transistor. One of a source and a drain of the driving transistor is electrically connected to the pixel electrode of the light-emitting device. An LTPS transistor is preferably used as the driving transistor. In that case, the amount of current flowing through the light-emitting device can be increased in the pixel circuit.

Another transistor included in the pixel portion177functions as a switch for controlling selection or non-selection of a pixel and can be referred to as a selection transistor. A gate of the selection transistor is electrically connected to a gate line, and one of a source and a drain thereof is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. In that case, the gray level of the pixel can be maintained even with an extremely low frame frequency (e.g., lower than or equal to 1 fps); thus, power consumption can be reduced by stopping the driver in displaying a still image.

As described above, the light-emitting apparatus of one embodiment of the present invention can have all of a high aperture ratio, a high resolution, high display quality, and low power consumption.

Note that the light-emitting apparatus of one embodiment of the present invention has a structure including the OS transistor and the light-emitting device having a metal maskless (MML) structure. This structure can significantly reduce a leakage current that would flow through a transistor and a leakage current that would flow between adjacent light-emitting devices (sometimes referred to as a horizontal leakage current or a lateral leakage current). Displaying images on the light-emitting apparatus having this structure can bring one or more of image crispness, image sharpness, high color saturation, and a high contrast ratio to the viewer. When a leakage current that would flow through the transistor and a lateral leakage current that would flow between the light-emitting devices are extremely low, leakage of light at the time of black display (black-level degradation) or the like can be minimized.

In particular, in the case where a light-emitting device having an MML structure employs the above-described SBS structure, a layer provided between light-emitting devices (for example, also referred to as an organic layer or a common layer which is shared by the light-emitting devices) is disconnected; accordingly, side leakage can be prevented or be made extremely low.

FIGS.16B and16Cillustrate other structure examples of transistors.

A transistor209and a transistor210each include the conductive layer221functioning as a gate, the insulating layer211functioning as a gate insulating layer, the semiconductor layer231including a channel formation region231iand a pair of low-resistance regions231n, the conductive layer222aconnected to one of the pair of low-resistance regions231n, the conductive layer222bconnected to the other of the pair of low-resistance regions231n, an insulating layer225functioning as a gate insulating layer, the conductive layer223functioning as a gate, and the insulating layer215covering the conductive layer223. The insulating layer211is positioned between the conductive layer221and the channel formation region231i. The insulating layer225is positioned at least between the conductive layer223and the channel formation region231i. Furthermore, an insulating layer218covering the transistor may be provided.

FIG.16Billustrates an example of the transistor209in which the insulating layer225covers the top and side surfaces of the semiconductor layer231. The conductive layer222aand the conductive layer222bare connected to the corresponding low-resistance regions231nthrough openings provided in the insulating layer225and the insulating layer215. One of the conductive layers222aand222bfunctions as a source, and the other functions as a drain.

In the transistor210illustrated inFIG.16C, the insulating layer225overlaps with the channel formation region231iof the semiconductor layer231and does not overlap with the low-resistance regions231n. The structure illustrated inFIG.16Cis obtained by processing the insulating layer225with the conductive layer223as a mask, for example. InFIG.16C, the insulating layer215is provided to cover the insulating layer225and the conductive layer223, and the conductive layer222aand the conductive layer222bare connected to the corresponding low-resistance regions231nthrough openings in the insulating layer215.

A connection portion204is provided in a region of the substrate351which does not overlap with the substrate352. In the connection portion204, the wiring355is electrically connected to the FPC353through a conductive layer166and a connection layer242. As an example, the conductive layer166has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers224R,224G, and224B; a conductive film obtained by processing the same conductive film as the conductive layers151R,151G, and151B; and a conductive film obtained by processing the same conductive film as the conductive layers152R,152G, and152B. On the top surface of the connection portion204, the conductive layer166is exposed. Thus, the connection portion204and the FPC353can be electrically connected to each other through the connection layer242.

The light-blocking layer157is preferably provided on the surface of the substrate352on the substrate351side. The light-blocking layer157can be provided over a region between adjacent light-emitting devices, in the connection portion140, in the circuit356, and the like. A variety of optical members can be arranged on the outer surface of the substrate352.

A material that can be used for the substrate120can be used for each of the substrates351and352.

A material that can be used for the resin layer122can be used for the adhesive layer142.

As the connection layer242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.

A light-emitting apparatus100H illustrated inFIG.17is different from the light-emitting apparatus100B illustrated inFIG.16Amainly in having a bottom-emission structure.

Light from the light-emitting device is emitted toward the substrate351. For the substrate351, a material having a high visible-light-transmitting property is preferably used. By contrast, there is no limitation on the light-transmitting property of a material used for the substrate352.

The light-blocking layer157is preferably formed between the substrate351and the transistor201and between the substrate351and the transistor205.FIG.17illustrates an example where the light-blocking layer157is provided over the substrate351, an insulating layer153is provided over the light-blocking layer157, and the transistors201and205and the like are provided over the insulating layer153.

The light-emitting device130R includes a conductive layer112R, a conductive layer126R over the conductive layer112R, and a conductive layer129R over the conductive layer126R.

The light-emitting device130B includes a conductive layer112B, a conductive layer126B over the conductive layer112B, and a conductive layer129B over the conductive layer126B.

A material having a high visible-light-transmitting property is used for each of the conductive layers112R,112B,126R,126B,129R, and129B. A material that reflects visible light is preferably used for the common electrode155.

Although not illustrated inFIG.17, the light-emitting device130G is also provided.

AlthoughFIG.17and the like illustrate an example where the top surface of the layer128includes a flat portion, the shape of the layer128is not particularly limited.

A light-emitting apparatus100C illustrated inFIG.18Ais a variation example of the light-emitting apparatus100B illustrated inFIG.16Aand differs from the light-emitting apparatus100B mainly in including the coloring layers132R,132G, and132B.

In the light-emitting apparatus100C, the light-emitting device130includes a region overlapping with one of the coloring layers132R,132G, and132B. The coloring layers132R,132G, and132B can be provided on a surface of the substrate352on the substrate351side. The end portions of the coloring layers132R,132G, and132B can overlap with the light-blocking layer157.

In the light-emitting apparatus100C, the light-emitting device130can emit white light, for example. The coloring layer132R, the coloring layer132G, and the coloring layer132B can transmit red light, green light, and blue light, respectively, for example. Note that in the light-emitting apparatus100C, the coloring layers132R,132G, and132B may be provided between the protective layer131and the adhesive layer142.

AlthoughFIG.16A,FIG.18A, and the like illustrate an example where the top surface of the layer128includes a flat portion, the shape of the layer128is not particularly limited.FIGS.18B to18Dillustrate variation examples of the layer128.

As illustrated inFIGS.18B and18D, the top surface of the layer128can have a shape such that its center and the vicinity thereof are depressed (i.e., a shape including a concave surface) in the cross section.

As illustrated inFIG.18C, the top surface of the layer128can have a shape in which its center and vicinity thereof bulge, i.e., a shape including a convex surface, in the cross section.

The top surface of the layer128may include one or both of a convex surface and a concave surface. The number of convex surfaces and the number of concave surfaces included in the top surface of the layer128are not limited and can each be one or more.

The level of the top surface of the layer128and the level of the top surface of the conductive layer224R may be the same or substantially the same, or may be different from each other. For example, the level of the top surface of the layer128may be either lower or higher than the level of the top surface of the conductive layer224R.

FIG.18Bcan be regarded as illustrating an example where the layer128fits in the depression portion of the conductive layer224R. By contrast, as illustrated inFIG.18D, the layer128may exist also outside the depression portion of the conductive layer224R, i.e., the top surface of the layer128may extend beyond the depression portion.

This embodiment can be combined as appropriate with the other embodiments or an example. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.

In this embodiment, electronic devices of embodiments of the present invention will be described.

Electronic devices of this embodiment include the light-emitting apparatus of one embodiment of the present invention in their display portions. The light-emitting apparatus of one embodiment of the present invention is highly reliable and can be easily increased in resolution and definition. Thus, the light-emitting apparatus of one embodiment of the present invention can be used for display portions of a variety of electronic devices.

Examples of the electronic devices include a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to electronic devices with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.

In particular, the light-emitting apparatus of one embodiment of the present invention can have a high resolution, and thus can be favorably used for an electronic device having a relatively small display portion. Examples of such an electronic device include watch-type and bracelet-type information terminal devices (wearable devices) and wearable devices worn on the head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR device.

The definition of the light-emitting apparatus of one embodiment of the present invention is preferably as high as HD (number of pixels: 1280×720), FHD (number of pixels: 1920×1080), WQHD (number of pixels: 2560×1440), WQXGA (number of pixels: 2560×1600), 4K (number of pixels: 3840×2160), or 8K (number of pixels: 7680×4320). In particular, the definition of 4K, 8K, or higher is preferable. The pixel density (resolution) of the light-emitting apparatus of one embodiment of the present invention is preferably higher than or equal to 100 ppi, further preferably higher than or equal to 300 ppi, further preferably higher than or equal to 500 ppi, further preferably higher than or equal to 1000 ppi, still further preferably higher than or equal to 2000 ppi, still further preferably higher than or equal to 3000 ppi, still further preferably higher than or equal to 5000 ppi, yet further preferably higher than or equal to 7000 ppi. With such a light-emitting apparatus having one or both of a high definition and a high resolution, the electronic device can provide higher realistic sensation, sense of depth, and the like in personal use such as portable use or home use. There is no particular limitation on the screen ratio (aspect ratio) of the light-emitting apparatus of one embodiment of the present invention. For example, the light-emitting apparatus is compatible with a variety of screen ratios such as 1:1 (a square), 4:3, 16:9, and 16:10.

The electronic device in this embodiment can have a variety of functions. For example, the electronic device in this embodiment can have a function of displaying a variety of data (e.g., a still image, a moving image, and a text image) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium.

Examples of head-mounted wearable devices are described with reference toFIGS.19A to19D. These wearable devices have at least one of a function of displaying AR contents, a function of displaying VR contents, a function of displaying SR contents, and a function of displaying MR contents. The electronic device having a function of displaying contents of at least one of AR, VR, SR, MR, and the like enables the user to feel a higher level of immersion.

An electronic device700A illustrated inFIG.19Aand an electronic device700B illustrated inFIG.19Beach include a pair of display panels751, a pair of housings721, a communication portion (not illustrated), a pair of wearing portions723, a control portion (not illustrated), an image capturing portion (not illustrated), a pair of optical members753, a frame757, and a pair of nose pads758.

The light-emitting apparatus of one embodiment of the present invention can be used for the display panels751. Thus, a highly reliable electronic device is obtained.

The electronic devices700A and700B can each project images displayed on the display panels751onto display regions756of the optical members753. Since the optical members753have a light-transmitting property, the user can see images displayed on the display regions, which are superimposed on transmission images seen through the optical members753. Accordingly, the electronic devices700A and700B are electronic devices capable of AR display.

In the electronic devices700A and700B, a camera capable of capturing images of the front side may be provided as the image capturing portion. Furthermore, when the electronic devices700A and700B are provided with an acceleration sensor such as a gyroscope sensor, the orientation of the user's head can be sensed and an image corresponding to the orientation can be displayed on the display regions756.

The communication portion includes a wireless communication device, and a video signal, for example, can be supplied by the wireless communication device. Instead of or in addition to the wireless communication device, a connector that can be connected to a cable for supplying a video signal and a power supply potential may be provided.

The electronic devices700A and700B are provided with a battery, so that they can be charged wirelessly and/or by wire.

A touch sensor module may be provided in the housing721. The touch sensor module has a function of detecting a touch on the outer surface of the housing721. Detecting a tap operation, a slide operation, or the like by the user with the touch sensor module enables various types of processing. For example, a video can be paused or restarted by a tap operation, and can be fast-forwarded or fast-reversed by a slide operation. When the touch sensor module is provided in each of the two housings721, the range of the operation can be increased.

Various touch sensors can be applied to the touch sensor module. For example, any of touch sensors of the following types can be used: a capacitive type, a resistive type, an infrared type, an electromagnetic induction type, a surface acoustic wave type, and an optical type. In particular, a capacitive sensor or an optical sensor is preferably used for the touch sensor module.

In the case of using an optical touch sensor, a photoelectric conversion device (also referred to as a photoelectric conversion element) can be used as a light-receiving element. One or both of an inorganic semiconductor and an organic semiconductor can be used for an active layer of the photoelectric conversion device.

An electronic device800A illustrated inFIG.19Cand an electronic device800B illustrated inFIG.19Deach include a pair of display portions820, a housing821, a communication portion822, a pair of wearing portions823, a control portion824, a pair of image capturing portions825, and a pair of lenses832.

The light-emitting apparatus of one embodiment of the present invention can be used in the display portions820. Thus, a highly reliable electronic device is obtained.

The display portions820are positioned inside the housing821so as to be seen through the lenses832. When the pair of display portions820display different images, three-dimensional display using parallax can be performed.

The electronic devices800A and800B can be regarded as electronic devices for VR. The user who wears the electronic device800A or the electronic device800B can see images displayed on the display portions820through the lenses832.

The electronic devices800A and800B preferably include a mechanism for adjusting the lateral positions of the lenses832and the display portions820so that the lenses832and the display portions820are positioned optimally in accordance with the positions of the user's eyes. Moreover, the electronic devices800A and800B preferably include a mechanism for adjusting focus by changing the distance between the lenses832and the display portions820.

The electronic device800A or the electronic device800B can be mounted on the user's head with the wearing portions823.FIG.19C, for example, shows an example where the wearing portion823has a shape like a temple of glasses; however, one embodiment of the present invention is not limited thereto. The wearing portion823can have any shape with which the user can wear the electronic device, for example, a shape of a helmet or a band.

The image capturing portion825has a function of obtaining information on the external environment. Data obtained by the image capturing portion825can be output to the display portion820. An image sensor can be used for the image capturing portion825. Moreover, a plurality of cameras may be provided so as to cover a plurality of fields of view, such as a telescope field of view and a wide field of view.

Although an example where the image capturing portions825are provided is shown here, a range sensor (hereinafter also referred to as a sensing portion) capable of measuring a distance between the user and an object just needs to be provided. In other words, the image capturing portion825is one embodiment of the sensing portion. As the sensing portion, an image sensor or a range image sensor such as a light detection and ranging (LiDAR) sensor can be used, for example. By using images obtained by the camera and images obtained by the range image sensor, more information can be obtained and a gesture operation with higher accuracy is possible.

The electronic device800A may include a vibration mechanism that functions as bone-conduction earphones. For example, at least one of the display portion820, the housing821, and the wearing portion823can include the vibration mechanism. Thus, without additionally requiring an audio device such as headphones, earphones, or a speaker, the user can enjoy video and sound only by wearing the electronic device800A.

The electronic devices800A and800B may each include an input terminal. To the input terminal, a cable for supplying a video signal from a video output device or the like, power for charging a battery provided in the electronic device, and the like can be connected.

The electronic device of one embodiment of the present invention may have a function of performing wireless communication with earphones750. The earphones750include a communication portion (not illustrated) and has a wireless communication function. The earphones750can receive information (e.g., audio data) from the electronic device with the wireless communication function. For example, the electronic device700A inFIG.19Ahas a function of transmitting information to the earphones750with the wireless communication function. As another example, the electronic device800A inFIG.19Chas a function of transmitting information to the earphones750with the wireless communication function.

The electronic device may include an earphone portion. The electronic device700B inFIG.19Bincludes earphone portions727. For example, the earphone portion727can be connected to the control portion by wire. Part of a wiring that connects the earphone portion727and the control portion may be positioned inside the housing721or the mounting portion723.

Similarly, the electronic device800B illustrated inFIG.19Dincludes earphone portions827. For example, the earphone portion827can be connected to the control portion824by wire. Part of a wiring that connects the earphone portion827and the control portion824may be positioned inside the housing821or the mounting portion823. Alternatively, the earphone portions827and the mounting portions823may include magnets. This is preferred because the earphone portions827can be fixed to the mounting portions823with magnetic force and thus can be easily housed.

The electronic device may include an audio output terminal to which earphones, headphones, or the like can be connected. The electronic device may include one or both of an audio input terminal and an audio input mechanism. As the audio input mechanism, a sound collecting device such as a microphone can be used, for example. The electronic device may have a function of a headset by including the audio input mechanism.

As described above, both the glasses-type device (e.g., the electronic devices700A and700B) and the goggles-type device (e.g., the electronic devices800A and800B) are preferable as the electronic device of one embodiment of the present invention.

The electronic device of one embodiment of the present invention can transmit information to earphones by wire or wirelessly.

An electronic device6500illustrated inFIG.20Ais a portable information terminal that can be used as a smartphone.

The light-emitting apparatus of one embodiment of the present invention can be used in the display portion6502. Thus, a highly reliable electronic device is obtained.

FIG.20Bis a schematic cross-sectional view including an end portion of the housing6501on the microphone6506side.

The display panel6511, the optical member6512, and the touch sensor panel6513are fixed to the protection member6510with an adhesive layer (not illustrated).

Part of the display panel6511is folded back in a region outside the display portion6502, and an FPC6515is connected to the part that is folded back. An IC6516is mounted on the FPC6515. The FPC6515is connected to a terminal provided on the printed circuit board6517.

The light-emitting apparatus of one embodiment of the present invention can be used in the display panel6511. Thus, an extremely lightweight electronic device can be achieved. Since the display panel6511is extremely thin, the battery6518with high capacity can be mounted without an increase in the thickness of the electronic device. Moreover, part of the display panel6511is folded back so that a connection portion with the FPC6515is provided on the back side of the pixel portion, whereby an electronic device with a narrow bezel can be achieved.

FIG.20Cillustrates an example of a television device. In a television device7100, a display portion7000is incorporated in a housing7171. Here, the housing7171is supported by a stand7173.

The light-emitting apparatus of one embodiment of the present invention can be used in the display portion7000. Thus, a highly reliable electronic device is obtained.

Operation of the television device7100illustrated inFIG.20Ccan be performed with an operation switch provided in the housing7171and a separate remote controller7151. Alternatively, the display portion7000may include a touch sensor, and the television device7100may be operated by touch on the display portion7000with a finger or the like. The remote controller7151may be provided with a display portion for displaying information output from the remote controller7151. With operation keys or a touch panel of the remote controller7151, channels and volume can be controlled and images displayed on the display portion7000can be controlled.

Note that the television device7100includes a receiver, a modem, and the like. A general television broadcast can be received with the receiver. When the television device is connected to a communication network with or without wires via the modem, one-way (from a transmitter to a receiver) or two-way (e.g., between a transmitter and a receiver or between receivers) information communication can be performed.

FIG.20Dillustrates an example of a notebook personal computer. A notebook personal computer7200includes a housing7211, a keyboard7212, a pointing device7213, an external connection port7214, and the like. The display portion7000is incorporated in the housing7211.

The light-emitting apparatus of one embodiment of the present invention can be used in the display portion7000. Thus, a highly reliable electronic device is obtained.

Digital signage7300illustrated inFIG.20Eincludes a housing7301, the display portion7000, a speaker7303, and the like. The digital signage7300can also include an LED lamp, operation keys (including a power switch or an operation switch), a connection terminal, a variety of sensors, a microphone, and the like.

FIG.20Fillustrates digital signage7400attached to a cylindrical pillar7401. The digital signage7400includes the display portion7000provided along a curved surface of the pillar7401.

InFIGS.20E and20F, the light-emitting apparatus of one embodiment of the present invention can be used in the display portion7000. Thus, a highly reliable electronic device is obtained.

A larger area of the display portion7000can increase the amount of information that can be provided at a time. The display portion7000having a larger area attracts more attention, so that the effectiveness of the advertisement can be increased, for example.

The touch panel is preferably used in the display portion7000, in which case in addition to display of still or moving images on the display portion7000, intuitive operation by a user is possible. Moreover, in the case of an application for providing information such as route information or traffic information, usability can be enhanced by intuitive operation.

As illustrated inFIGS.20E and20F, it is preferable that the digital signage7300or the digital signage7400can work with an information terminal7311or an information terminal7411, such as a smartphone that a user has, through wireless communication. For example, information of an advertisement displayed on the display portion7000can be displayed on a screen of the information terminal7311or the information terminal7411. By operation of the information terminal7311or the information terminal7411, a displayed image on the display portion7000can be switched.

It is possible to make the digital signage7300or the digital signage7400execute a game with the use of the screen of the information terminal7311or the information terminal7411as an operation means (controller). Thus, an unspecified number of users can join in and enjoy the game concurrently.

The electronic devices illustrated inFIGS.21A to21Ghave a variety of functions. For example, the electronic devices can have a function of displaying a variety of information (e.g., a still image, a moving image, and a text image) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of controlling processing with the use of a variety of software (programs), a wireless communication function, and a function of reading out and processing a program or data stored in a recording medium. Note that the functions of the electronic devices are not limited thereto, and the electronic devices can have a variety of functions. The electronic devices may include a plurality of display portions. The electronic devices may be provided with a camera or the like and have a function of taking a still image or a moving image, a function of storing the taken image in a storage medium (an external storage medium or a storage medium incorporated in the camera), a function of displaying the taken image on the display portion, and the like.

The electronic devices inFIGS.21A to21Gare described in detail below.

FIG.21Ais a perspective view of a portable information terminal9171. The portable information terminal9171can be used as a smartphone, for example. The portable information terminal9171may include the speaker9003, the connection terminal9006, the sensor9007, or the like. The portable information terminal9171can display text and image information on its plurality of surfaces.FIG.21Aillustrates an example where three icons9050are displayed. Furthermore, information9051indicated by dashed rectangles can be displayed on another surface of the display portion9001. Examples of the information9051include notification of reception of an e-mail, an SNS message, an incoming call, or the like, the title and sender of an e-mail, an SNS message, or the like, the date, the time, remaining battery, and the radio field intensity. Alternatively, the icon9050or the like may be displayed at the position where the information9051is displayed.

FIG.21Bis a perspective view of a portable information terminal9172. The portable information terminal9172has a function of displaying information on three or more surfaces of the display portion9001. Here, information9052, information9053, and information9054are displayed on different surfaces. For example, the user of the portable information terminal9172can check the information9053displayed such that it can be seen from above the portable information terminal9172, with the portable information terminal9172put in a breast pocket of his/her clothes. Thus, the user can see the display without taking out the portable information terminal9172from the pocket and decide whether to answer the call, for example.

FIG.21Cis a perspective view of a tablet terminal9173. The tablet terminal9173is capable of executing a variety of applications such as mobile phone calls, e-mailing, viewing and editing texts, music reproduction, Internet communication, and a computer game, for example. The tablet terminal9173includes the display portion9001, the camera9002, the microphone9008, and the speaker9003on the front surface of the housing9000; the operation keys9005as buttons for operation on the left side surface of the housing9000; and the connection terminal9006on the bottom surface of the housing9000.

FIG.21Dis a perspective view of a watch-type portable information terminal9200. The portable information terminal9200can be used as a Smartwatch (registered trademark), for example. The display surface of the display portion9001is curved, and an image can be displayed on the curved display surface. Furthermore, for example, mutual communication between the portable information terminal9200and a headset capable of wireless communication can be performed, and thus hands-free calling is possible. With the connection terminal9006, the portable information terminal9200can perform mutual data transmission with another information terminal and charging. Note that the charging operation may be performed by wireless power feeding.

FIGS.21E to21Gare perspective views of a foldable portable information terminal9201.FIG.21Eis a perspective view illustrating the portable information terminal9201that is opened.FIG.21Gis a perspective view illustrating the portable information terminal9201that is folded.FIG.21Fis a perspective view illustrating the portable information terminal9201that is shifted from one of the states inFIGS.21E and21Gto the other. The portable information terminal9201is highly portable when folded. When the portable information terminal9201is opened, a seamless large display region is highly browsable. The display portion9001of the portable information terminal9201is supported by three housings9000joined together by hinges9055. The display portion9001can be folded with a radius of curvature of greater than or equal to 0.1 mm and less than or equal to 150 mm, for example.

This embodiment can be combined as appropriate with the other embodiments or an example. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.

In this example, a device1A and a device2A, which are embodiments of the present invention described in the above embodiment, and a device3A for comparison were fabricated through an MML process, and the characteristics of the devices were evaluated. The evaluation results are described. For reference, a device1, a device2B, and a device3B were fabricated using the same materials as the above devices through a continuous vacuum process.

The structural formulae of organic compounds used for the devices1A,2A, and3A are shown below.

As illustrated inFIG.22, the devices each have a tandem structure where a first EL layer903, an intermediate layer905, a second EL layer904, and a second electrode902are stacked over a first electrode901formed over a glass substrate900.

The first EL layer903has a structure where a hole-injection layer910, a first hole-transport layer911, a first light-emitting layer912, and a first electron-transport layer913are stacked in this order. The intermediate layer905includes an electron-injection buffer region914and a layer915including an electron-relay region and a charge generation region. The second EL layer904has a structure where a second hole-transport layer916, a second light-emitting layer917, a second electron-transport layer918, and an electron-injection layer919are stacked in this order.

<Fabrication Method of Devices>

Fabrication methods of the devices1A,2A,3A,1B,2B, and3B are described below.

Fabrication Method of Device1A>>

First, as a reflective electrode, an alloy containing silver (Ag), palladium (Pd), and copper (Cu) (abbreviation: APC) was deposited over the glass substrate900to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 100 nm by a sputtering method, whereby the first electrode901was formed. The electrode area was set to 4 mm2(2 mm×2 mm). Note that the reflective electrode and the transparent electrode can be collectively regarded as the first electrode901.

Next, the first EL layer903was provided. First, in pretreatment for forming the device1A over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.

Then, the substrate provided with the first electrode901was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode901was formed faced downward. Over the first electrode901, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03 using a resistance-heating method, whereby the hole-injection layer910was formed.

Next, PCBBiF was deposited to a thickness of 60 nm by evaporation over the hole-injection layer910, whereby the first hole-transport layer911was formed.

Next, the first light-emitting layer912was formed over the first hole-transport layer911. Using a resistance-heating method, 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), and [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phen yl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio between 4,8mDBtP2Bfpm, βNCCP, and Ir(ppy)2(mbfpypy-d3) was 5:5:1, whereby the first light-emitting layer912was formed.

Then, over the first light-emitting layer912, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited to a thickness of 25 nm by evaporation, whereby the first electron-transport layer913was formed.

Next, the intermediate layer905was provided. First, over the first electron-transport layer913, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) and lithium oxide (Li2O) were deposited to a thickness of 5 nm by co-evaporation such that the volume ratio of mPPhen2P to Li2O was 1:0.01 using a resistance-heating method, whereby a layer serving as the electron-injection buffer region914was formed.

Then, as the electron-relay region, copper phthalocyanine (CuPc) was deposited to a thickness of 2 nm. Next, as the charge generation region, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.3 using a resistance-heating method, whereby the layer915including the electron-relay region and the charge generation region was formed.

Next, the second EL layer904was provided. First, PCBBiF was deposited to a thickness of 40 nm by evaporation, whereby the second hole-transport layer916was formed.

Next, 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), and [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phen yl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio between 4,8mDBtP2Bfpm, βNCCP, and Ir(ppy)2(mbfpypy-d3) was 5:5:1 using a resistance-heating method, whereby the second light-emitting layer917was formed.

Then, over the second light-emitting layer917, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) was deposited to a thickness of 30 nm by evaporation, and then mPPhen2P and lithium oxide (Li2O) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of mPPhen2P to Li2O was 1:0.01, whereby the second electron-transport layer918was formed.

After exposure to the air, an aluminum oxide (abbreviation: AlOx) film was formed to a thickness of 30 nm by an ALD method. After that, an oxide containing indium, gallium, zinc, and oxygen (abbreviation: IGZO) was deposited to a thickness of 30 nm by a sputtering method. Then, a resist was formed using a photoresist, and the IGZO was processed into a predetermined shape by a lithography method.

Next, using the IGZO as a mask, the stacked-layer structure formed of the aluminum oxide film, the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918was processed into a predetermined shape, and then the IGZO and the aluminum oxide film were removed. The IGZO and the aluminum oxide film were removed by wet etching using an acidic chemical solution. Note that the predetermined shape was made by forming a slit having a width of 3 μm in a position that is 3.5 μm apart from the end portion of the first electrode901. This makes the side surfaces of the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918be substantially aligned.

Next, heat treatment was performed in vacuum at 110° C. for 1 hour. The heat treatment can remove moisture or the like attached by the above-described processing, the exposure to the air, or the like.

Next, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, over the electron-injection layer919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the device1A was fabricated.

<<Fabrication Method of the Device2A>>

Next, a fabrication method of the device2A is described. The device2A is different from the device1A in the structure of the first electron-transport layer913.

In the device2A, over the first light-emitting layer912, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited to a thickness of 10 nm by evaporation, and then 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) was deposited to a thickness of 15 nm by evaporation using a resistance-heating method, whereby the first electron-transport layer913was formed.

Other components were fabricated in a manner similar to that of the device1A.

Fabrication Method of Device3A>>

Next, a fabrication method of the device3A is described. The device3A is different from the device1A in the structures of the first electron-transport layer913and the second electron-transport layer918.

As in the device2A, in the device3A, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer912, and then 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) was deposited to a thickness of 15 nm by evaporation using a resistance-heating method, whereby the first electron-transport layer913was formed.

In the device3A, over the second light-emitting layer917, 2mPCCzPDBq was deposited to a thickness of 20 nm by evaporation using a resistance-heating method, mPPhen2P was deposited to a thickness of 15 nm by evaporation, and then mPPhen2P and lithium oxide (Li2O) were deposited to a thickness of 5 nm by co-evaporation such that the weight ratio of mPPhen2P to Li2O was 1:0.02, whereby the second electron-transport layer918was formed.

Other components were fabricated in a manner similar to that of the device1A.

Fabrication Methods of Devices1B,2B, and3B>>

Next, fabrication methods of the devices1B,2B, and3B are described. The devices1B,2B, and3B were fabricated using the same materials as the devices1A,2A, and3A through a continuous vacuum process.

Specifically, the devices1B,2B, and3B were fabricated in a manner similar to those of the devices1A,2A, and3A, respectively, up to and including the step of forming the second electron-transport layer918.

Here, without breaking the vacuum, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, without breaking the vacuum, over the electron-injection the electron-injection layer919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the devices1B,2B, and3B were fabricated.

The following table shows the device structures of the devices (the devices1A,1B,2A,2B,3A, and3B).

Through the above steps, the devices were fabricated.

The devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the devices and UV treatment and heat treatment at 80° C. for 1 hour were performed at the time of sealing). Then, the characteristics of the devices were measured.

FIG.23shows the current efficiency-luminance characteristics of the devices.FIG.24shows the luminance-voltage characteristics thereof.FIG.25shows the current efficiency-current density characteristics thereof.FIG.26shows the current density-voltage characteristics thereof.FIG.27shows the luminance-current density characteristics thereof.FIG.28shows the current density-voltage characteristics thereof.FIG.29shows the emission spectra thereof.

The following table shows the main characteristics of the devices at a current density of 50 mA/cm2. Note that luminance, CIE chromaticity, and emission spectra were measured with a spectroradiometer (SR-UL1R manufactured by TOPCON TECHNOHOUSE CORPORATION).

A voltage difference at 50 mA/cm2is as small as 0.26 V between the devices1A and1B and 1.47 V between the devices2A and2B, whereas the voltage difference is as large as 1.86 V between the devices3A and3B for comparison.

A difference in current density at 50 mA/cm2is as small as 2 cd/A between the devices1A and1B and between the devices2A and2B, whereas the voltage difference is as large as 7 cd/A between the devices3A and3B for comparison.

FIGS.23to28and Table 2 show that the devices1A and2A have favorable device characteristics even when fabricated through a process involving exposure to the air and a chemical solution and an etching process (what is called an MML process), and in particular, the device1A has device characteristics equivalent to those of the device1B fabricated though a continuous vacuum process. That is, the device1A is found to be highly resistant to the process involving exposure to the air and the chemical solution and the etching process.

Meanwhile, the device3A fabricated through the MML process, in which the layer with high lithium diffusibility (mPPhen2P) is provided to be in contact with the layer containing lithium (Li), has a higher voltage and lower current efficiency than the device3B fabricated through a continuous vacuum process. It is found that the device3A including two or more layers with high lithium diffusibility (mPPhen2P) which are in contact with the layer containing Li tends to have a higher-voltage characteristics and much lower current efficiency than the device2A including one layer with high lithium diffusibility (mPPhen2P) which is in contact with the layer containing Li.

The glass transition temperatures (Tgs) of the organic compounds used for the first electron-transport layers and the second electron-transport layers of the devices were measured by differential scanning calorimetry (DSC). For the DSC measurement, Pyris 1 DSC manufactured by PerkinElmer, Inc. was used. In the DSC measurement, after the temperature was raised from −10° C. to 300° C. at a temperature rising rate of 40° C./min, the temperature was held for a minute and then decreased to −10° C. at a temperature decreasing rate of 40° C./min. This operation was repeated twice successively. It is found from the DSC measurement that the glass transition temperature of mPPhen2P is 135° C. and that of 2mPCCzPDBq is 160° C. This reveals that 2mPCCzPDBq has a glass transition temperature higher than that of mPPhen2P by 25° C., and thus has high heat resistance.

In addition, the LUMO levels of the organic compounds used for the first electron-transport layers and the second electron-transport layers of the devices were measured. The LUMO level was calculated from the reduction potentials and the oxidation potentials that were measured by cyclic voltammetry (CV) using an electrochemical analyzer (ALS model600A or 600C, manufactured by BAS Inc.). It is found from the CV measurement that the LUMO level of mPPhen2P is −2.71 eV and that of 2mPCCzPDBq is −2.98 eV. This reveals that the LUMO level of 2mPCCzPDBq is lower than that of mPPhen2P by 0.27 eV.

The refractive indices of the organic compounds in a visible light region were measured. The measurement was performed with an M-2000U spectroscopic ellipsometer manufactured by J.A. Woollam Japan Corp. To obtain films used as measurement samples, the organic compounds were each deposited to a thickness of approximately 50 nm over a quartz substrate by a vacuum evaporation method. The ordinary refractive indices at a wavelength of 633 nm are 1.80 in mPPhen2P and 1.88 in 2mPCCzPDBq. This reveals that the refractive index of 2mPCCzPDBq is higher than that of mPPhen2P by 0.08.

Note that mPPhen2P includes a phenanthroline skeleton (a heteroaromatic ring composed of three rings with two nitrogen atoms), and 2mPCCzPDBq includes a dibenzo quinoxaline skeleton (a heteroaromatic ring composed of four rings with two nitrogen atoms). That is, 2mPCCzPDBq includes a polycyclic heteroaromatic ring containing two nitrogen atoms and thus includes a larger number of rings in the heteroaromatic ring than mPPhen2P. The molecular ratios of the organic compound are 586.68 in mPPhen2P and 712.84 in 2mPCCzPDBq. Thus, 2mPCCzPDBq has a larger molecular weight than mPPhen2P.

Therefore, in the case where a layer containing Li is provided in the intermediate layer, an organic compound contained in a layer in contact with the layer containing Li preferably has a higher molecular weight, a lower LUMO level, a higher refractive index, or a higher glass transition temperature (Tg) than an organic compound contained in the layer containing Li. Furthermore, the organic compound contained in the layer in contact with the layer containing Li preferably includes a nitrogen-containing polycyclic heteroaromatic ring with a larger number of rings.

Specifically, in the case where an organic compound including a phenanthroline skeleton is used for the layer containing Li, an organic compound having a higher molecular weight, a lower LUMO level, a higher refractive index, or a higher glass transition temperature (Tg) than phenanthroline is preferably used for the layer in contact with the layer containing Li.

The above results reveal that the use of one embodiment of the present invention enables provision of a light-emitting device having high resistance to a process involving exposure to the air and a chemical solution and an etching process and having favorable device characteristics.

A reliability test was performed on the devices1A,2A, and3A.FIG.30shows time dependence of change in luminance (%) at the time of constant current density driving (50 mA/cm2) when the luminance at the start of light emission is regarded as 100%.

FIG.30also shows that LT80 (h), which is a time taken until the measurement luminance decreases to 80% of the initial luminance, is approximately 140 hours in the devices fabricated using one embodiment of the present invention.

It is found fromFIG.30that the devices1A,2A, and3A have highly reliable device characteristics even when fabricated through the process involving exposure to the air and the chemical solution and the etching process (what is called the MML process).

Accordingly, the device1A is found to be highly resistant to the process involving exposure to the air and the chemical solution and the etching process. That is, with the use of one embodiment of the present invention, a device can have favorable device characteristics even when fabricated through the process involving exposure to the air and the chemical solution and the etching process.

In this example, a device4A and a device5A, which are embodiments of the present invention described in the above embodiment, and a device6A and a device7A for comparison were fabricated through the MML process, and the characteristics of the devices were evaluated. The evaluation results are described. In addition, for reference, a device4B, a device5B, a device6B, and a device7B were fabricated using the same materials as the devices4A,5A,6A, and7A through a continuous vacuum process.

Structural formulae of organic compounds used for the devices4A,5A,6A, and7A are shown below.

Note that the devices (the devices4A,5A,6A,7A,4B,5B,6B, and7B) each have a tandem structure where the first EL layer903, the intermediate layer905, the second EL layer904, and the second electrode902were stacked over the first electrode901formed over the glass substrate900, as illustrated inFIG.22.

The first EL layer903has a structure where the hole-injection layer910, the first hole-transport layer911, the first light-emitting layer912, and the first electron-transport layer913are stacked in this order. The intermediate layer905includes the electron-injection buffer region914and the layer915including an electron-relay region and a charge generation region. The second EL layer904has a structure where the second hole-transport layer916, the second light-emitting layer917, the second electron-transport layer918, and the electron-injection layer919are stacked in this order.

<Fabrication Method of Devices>

Fabrication methods of the devices4A,5A,6A,7A,4B,5B,6B, and7B are described below.

Fabrication Method of Device4A>>

First, as a reflective electrode, an alloy containing silver (Ag), palladium (Pd), and copper (Cu) (abbreviation: APC) was deposited over the glass substrate900to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 100 nm by a sputtering method, whereby the first electrode901was formed. The electrode area was set to 4 mm2(2 mm×2 mm). Note that the reflective electrode and the transparent electrode can be collectively regarded as the first electrode901.

Next, the first EL layer903was provided. First, in pretreatment for forming the device1A over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.

Then, the substrate provided with the first electrode901was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode901was formed faced downward. Over the first electrode901, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03 using a resistance-heating method, whereby the hole-injection layer910was formed.

Next, PCBBiF was deposited to a thickness of 60 nm by evaporation over the hole-injection layer910, whereby the first hole-transport layer911was formed.

Next, the first light-emitting layer912was formed over the first hole-transport layer911. Using a resistance-heating method, 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), and [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-KC]bis[2-(2-pyridinyl-κN)phen yl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio between 4,8mDBtP2Bfpm, βNCCP, and Ir(ppy)2(mbfpypy-d3) was 5:5:1, whereby the first light-emitting layer912was formed.

Then, over the first light-emitting layer912, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited to a thickness of 25 nm by evaporation, whereby the first electron-transport layer913was formed.

Next, the intermediate layer905was provided. First, over the first electron-transport layer913, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) and lithium oxide (Li2O) were deposited to a thickness of 5 nm by co-evaporation such that the volume ratio of mPPhen2P to Li2O was 1:0.01 using a resistance-heating method, whereby a layer serving as the electron-injection buffer region914was formed.

Then, as the electron-relay region, copper phthalocyanine (CuPc) was deposited to a thickness of 2 nm. Next, as the charge generation region, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.3 using a resistance-heating method, whereby the layer915including the electron-relay region and the charge generation region was formed.

Next, the second EL layer904was provided. First, PCBBiF was deposited to a thickness of 40 nm by evaporation, whereby the second hole-transport layer916was formed.

Then, using a resistance-heating method, 4,8mDBtP2Bfpm, βNCCP, and Ir(ppy)2(mbfpypy-d3) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio between 4,8mDBtP2Bfpm, βNCCP, and Ir(ppy)2(mbfpypy-d3) was 5:5:1, whereby the second light-emitting layer917was formed.

Then, over the second light-emitting layer917, 2mPCCzPDBq was deposited to a thickness of 20 nm by evaporation, and mPPhen2P was deposited to a thickness of 20 nm by evaporation, whereby the second electron-transport layer918was formed.

Here, after exposure to the air, an aluminum oxide (abbreviation: AlOx) film was formed to a thickness of 30 nm by an ALD method. After that, an oxide containing indium, gallium, zinc, and oxygen (abbreviation: IGZO) was deposited to a thickness of 30 nm by a sputtering method. Then, a resist was formed using a photoresist, and the IGZO was processed into a predetermined shape by a lithography method.

Next, using the IGZO as a mask, the stacked-layer structure formed of the aluminum oxide film, the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918was processed into a predetermined shape, and then the IGZO and the aluminum oxide film were removed. The IGZO and the aluminum oxide film were removed by wet etching using an acidic chemical solution. Note that the predetermined shape was made by forming a slit having a width of 3 μm in a position that is 3.5 μm apart from the end portion of the first electrode901. This makes the side surfaces of the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918be substantially aligned.

Next, heat treatment was performed in vacuum at 110° C. for 1 hour. The heat treatment can remove moisture or the like attached by the above-described processing, the exposure to the air, or the like.

Next, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, over the electron-injection layer919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the device4A was fabricated.

Fabrication Method of Device5A>>

Next, a fabrication method of the device5A is described. The device5A is different from the device4A in the structure of the first electron-transport layer913.

In the device5A, using a resistance-heating method, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer912. Subsequently, using a resistance-heating method, 2,2′-(2,2′-bipyridine-6,6′-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 6,6′(P-Bqn)2BPy) was deposited to a thickness of 15 nm by evaporation, whereby the first electron-transport layer913was formed.

Other components were fabricated in a manner similar to that of the device4A.

Fabrication Method of Device6A>>

Next, a fabrication method of the device6A is described. The device6A is different from the device4A in the structure of the first electron-transport layer913.

In the device6A, using a resistance-heating method, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer912. Subsequently, using a resistance-heating method, 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) was deposited to a thickness of 15 nm by evaporation, whereby the first electron-transport layer913was formed.

Other components were fabricated in a manner similar to that of the device4A.

Fabrication Method of Device7A>>

Next, a fabrication method of the device7A is described. The device7A is different from the device4A in the structure of the first electron-transport layer913.

In the device7A, using a resistance-heating method, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer912. Sequentially, using a resistance-heating method, 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz) was deposited to a thickness of 15 nm by evaporation, whereby the first electron-transport layer913was formed.

Other components were fabricated in a manner similar to that of the device4A.

Fabrication Methods of Devices4B,5B,6B, and7B>>

Next, fabrication methods of the devices4B,5B,6B, and7B are described. The devices4B,5B,6B, and7B were fabricated using the same materials as the devices4A,5A,6A, and7A through a continuous vacuum process.

The devices4B,5B,6B, and7B were fabricated in a manner similar to those of the devices4A,5A,6A, and7A, respectively, up to and including the step of forming the second electron-transport layer918.

Here, without breaking the vacuum, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, without breaking the vacuum, over the electron-injection the layer919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-J) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the devices4B, DB,6B, and7B were fabricated.

The following table shows the device structures of the devices (the devices4A,5A,6A,7A,4B,2B,6B, and7B).

Through the above steps, the devices were fabricated.

The devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the devices and UV treatment and heat treatment at 80° C. for 1 hour were performed at the time of sealing). Then, the initial characteristics of the devices were measured.

FIG.31shows the current efficiency-luminance characteristics of the devices.FIG.32shows the luminance-voltage characteristics thereof.FIG.33shows the current efficiency-current density characteristics thereof.FIG.34shows the current density-voltage characteristics thereof.FIG.35shows the luminance-current density characteristics thereof.FIG.36shows the current density-voltage characteristics thereof.FIG.37shows the emission spectra thereof.

The following table shows the main characteristics of the devices at a current density of 50 mA/cm2. Note that luminance, CIE chromaticity, and emission spectra were measured with a spectroradiometer (SR-UL1R manufactured by TOPCON TECHNOHOUSE CORPORATION).

A voltage difference at 50 mA/cm2is as small as 0.97 V between the devices4A and4B and 1.38 V between the devices5A and5B, whereas the voltage difference is as large as 2.21 V between the devices6A and6B for comparison and 1.99 V between the devices7A and7B for comparison.

FIGS.31to36and Table 4 show that, even when fabricated through the process involving exposure to the air and the chemical solution and the etching process (what is called the MML process), the devices4A and5A each have a driving voltage close to that of the device fabricated through a continuous vacuum process. That is, the devices4A and5A are found to be highly resistant to the process involving exposure to the air and the chemical solution and the etching process.

Meanwhile, the devices6A and7A fabricated through the MML process, in which the layer with high lithium diffusibility (mPn-mDMePyPTzn or TmPPPyTz) is provided to be in contact with the layer containing Li, has a driving voltage much higher than that of the device fabricated through a continuous vacuum process.

The glass transition temperature (Tg) of the organic compound used for the first electron-transport layer913is as follows: 135° C. in mPPhen2P; 160° C. in 2mPCCzPDBq; 153° C. in 6,6′(P-Bqn)2BPy; 120° C. in mPn-mDMePyPTzn; and 83° C. in TmPPPyTz. This reveals that 2mPCCzPDBq and 6,6′(P-Bqn)2BPy have glass transition temperatures higher than that of mPPhen2P by 25° C. and 18° C., respectively, and thus have high heat resistance. Meanwhile, mPn-mDMePyPTzn and TmPPPyTz are found to have a lower glass transition temperature than mPPhen2P.

The LUMO level of the organic compound is as follows: −2.71 eV in mPPhen2P; −2.98 eV in 2mPCCzPDBq; −2.92 eV in 6,6′(P-Bqn)2BPy; −2.98 eV in mPn-mDMePyPTzn; and −3.00 eV in TmPPPyTz. This reveals that the LUMO levels of 2mPCCzPDBq and 6,6′(P-Bqn)2BPy are lower than that of mPPhen2P by 0.27 eV and 0.21 eV, respectively.

The ordinary index of the organic compound at a wavelength of 633 nm is as follows: 1.80 in mPPhen2P; 1.88 in 2mPCCzPDBq; 1.84 in 6,6′(P-Bqn)2BPy; 1.74 in mPn-mDMePyPTzn; and 1.79 in TmPPPyTz. This reveals that the refractive indices of 2mPCCzPDBq and 6,6′(P-Bqn)2BPy are higher than that of mPPhen2P by 0.08 and 0.04, respectively. Meanwhile, mPn-mDMePyPTzn and TmPPPyTz are found to have a lower refractive index than mPPhen2P.

Note that mPPhen2P includes a phenanthroline skeleton (a heteroaromatic ring composed of three rings with two nitrogen atoms), 2mPCCzPDBq includes a dibenzoquinoxaline skeleton (a heteroaromatic ring composed of four rings with two nitrogen atoms), and 6,6′(P-Bqn)2BPy includes a benzoquinazoline skeleton (a heteroaromatic ring composed of three rings with two nitrogen atoms). That is, 2mPCCzPDBq and 6,6′(P-Bqn)2BPy each include a polycyclic heteroaromatic ring containing two nitrogen atoms and being composed of the same or a larger number of rings as or than the heteroaromatic ring of mPPhen2P. By contrast, mPn-mDMePyPTzn and TmPPPyTz each include a triazine skeleton (a heteroaromatic ring composed of one ring with three nitrogen atoms) and a pyridine skeleton (a heteroaromatic ring composed of one ring with one nitrogen atom), and do not include a polycyclic heteroaromatic ring. The molecular weight of the organic compound is as follows: 586.68 in mPPhen2P; 712.84 in 2mPCCzPDBq; and 664.75 in 6,6′(P-Bqn)2BPy. This reveals that 2mPCCzPDBq and 6,6′(P-Bqn)2BPy each have a lager molecular weight than mPPhen2P.

Therefore, in the case where a layer containing Li is provided in the intermediate layer, an organic compound contained in a layer in contact with the layer containing Li preferably has a higher molecular weight, a lower LUMO level, a higher refractive index, or a higher glass transition temperature (Tg) than an organic compound contained in the layer containing Li. Furthermore, the organic compound contained in the layer in contact with the layer containing Li preferably includes a nitrogen-containing polycyclic heteroaromatic ring with a larger number of rings.

The above results reveal that the use of one embodiment of the present invention enables provision of a light-emitting device having high resistance to a process involving exposure to the air and a chemical solution and an etching process and having favorable device characteristics.

A reliability test was performed on the devices4A,5A,6A, and7A.FIG.38shows time dependence of change in luminance (%) at the time of constant current density driving (50 mA/cm2) when the luminance at the start of light emission is regarded as 100%.

FIG.38also shows that LT90 (h), which is a time taken until the measurement luminance decreases to 90% of the initial luminance, of the devices4A and5A fabricated using one embodiment of the present invention is 94 hours and 119 hours, respectively, revealing that the devices4A and5A are highly stable devices. By contrast, the device6A for comparison has an LT90 of as long as 132 hours but has a large luminance increase in initial driving, and the device7A has an LT90 of as short as 7 hours, which reveals that the devices6A and7A are unstable devices.

That is, with the use of one embodiment of the present invention, a device can have high reliability even when fabricated through the process involving exposure to the air and the chemical solution and the etching process.

In this example, a device8A, which is one embodiment of the present invention described in the above embodiment, and a device9A for comparison were fabricated through the MML process, and the characteristics of the devices were evaluated. The evaluation results are described. For reference, a device8B and a device9B were fabricated using the same materials as the devices8A and9A through a continuous vacuum process.

The structural formulae of organic compounds used for the devices8A and9A are shown below.

As illustrated inFIG.22, the devices each have a tandem structure where the first EL layer903, the intermediate layer905, the second EL layer904, and the second electrode902are stacked over the first electrode901formed over the glass substrate900.

The first EL layer903has a structure where the hole-injection layer910, the first hole-transport layer911, the first light-emitting layer912, and the first electron-transport layer913are stacked in this order. The intermediate layer905includes the electron-injection buffer region914and the layer915including an electron-relay region and a charge generation region. The second EL layer904has a structure where the second hole-transport layer916, the second light-emitting layer917, the second electron-transport layer918, and the electron-injection layer919are stacked in this order.

<Fabrication Method of Devices>

Fabrication methods of the devices8A,9A,8B, and9B are described below.

<<Fabrication Method of Device8A>>

First, as a reflective electrode, an alloy containing silver (Ag), palladium (Pd), and copper (Cu) (abbreviation: APC) was deposited over the glass substrate900to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 100 nm by a sputtering method, whereby the first electrode901was formed. The electrode area was set to 4 mm2(2 mm×2 mm). Note that the reflective electrode and the transparent electrode can be collectively regarded as the first electrode901.

Next, the first EL layer903was provided. First, in pretreatment for forming the device1A over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.

Then, the substrate provided with the first electrode901was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode901was formed faced downward. Over the first electrode901, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03 using a resistance-heating method, whereby the hole-injection layer910was formed.

Next, PCBBiF was deposited to a thickness of 60 nm by evaporation over the hole-injection layer910, whereby the first hole-transport layer911was formed.

Next, the first light-emitting layer912was formed over the first hole-transport layer911. Using a resistance-heating method, 8-(1,1′:4′,1″-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyr imidine (abbreviation: 8mpTP-4mDBtPBfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), and [2-d3-methyl-8-(2-pyridinyl-κC)benzofuro[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyr idinyl-κN2)phenyl-κC]iridium(III) (abbreviation: Ir(5mppy-d3)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio between 8mpTP-4mDBtPBfpm, βNCCP, and Ir(5mppy-d3)2(mbfpypy-d3) was 5:5:1, whereby the first light-emitting layer912was formed.

Then, over the first light-emitting layer912, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited to a thickness of 25 nm by evaporation, whereby the first electron-transport layer913was formed.

Next, the intermediate layer905was provided. First, over the first electron-transport layer913, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) and lithium oxide (Li2O) were deposited to a thickness of 5 nm by co-evaporation such that the volume ratio of mPPhen2P to Li2O was 1:0.01 using a resistance-heating method, whereby a layer serving as the electron-injection buffer region914was formed.

Then, as the electron-relay region, copper phthalocyanine (CuPc) was deposited to a thickness of 2 nm. Next, as the charge generation region, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited to a thickness of 10 nm by co-evaporation such that the weight ratio of PCBBiF to OCHD-003 was 1:0.3 using a resistance-heating method, whereby the layer915including the electron-relay region and the charge generation region was formed.

Next, the second EL layer904was provided. First, PCBBiF was deposited to a thickness of 40 nm by evaporation, whereby the second hole-transport layer916was formed.

Next, over the second light-emitting layer917, 2mPCCzPDBq was deposited to a thickness of 20 nm by evaporation, and then mPPhen2P was deposited to a thickness of 20 nm by evaporation, whereby the second electron-transport layer918was formed.

Here, after exposure to the air, an aluminum oxide (abbreviation: AlOx) film was formed to a thickness of 30 nm by an ALD method. After that, an oxide containing indium, gallium, zinc, and oxygen (abbreviation: IGZO) was deposited to a thickness of 30 nm by a sputtering method. Then, a resist was formed using a photoresist, and the IGZO was processed into a predetermined shape by a lithography method.

Next, using the IGZO as a mask, the stacked-layer structure formed of the aluminum oxide film, the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918was processed into a predetermined shape, and then the IGZO and the aluminum oxide film were removed. The IGZO and the aluminum oxide film were removed by wet etching using an acidic chemical solution. Note that the predetermined shape was made by forming a slit having a width of 3 μm in a position that is 3.5 μm apart from the end portion of the first electrode901. This makes the side surfaces of the first EL layer903, the intermediate layer905, the second hole-transport layer916, the second light-emitting layer917, and the second electron-transport layer918be substantially aligned.

Next, heat treatment was performed in vacuum at 110° C. for 1 hour. The heat treatment can remove moisture or the like attached by the above-described processing, the exposure to the air, or the like.

Next, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, over the electron-injection layer919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the device8A was fabricated.

Fabrication Method of Device9A>>

Next, a fabrication method of the device9A is described. The device9A is different form the device8A in the structure of the first electron-transport layer913.

In the device9A, using a resistance-heating method, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer912, and then mPPhen2P was deposited to a thickness of 15 nm by evaporation, whereby the first electron-transport layer913was formed.

Other components were fabricated in a manner similar to that of the device8A.

Fabrication Methods of Devices8B and9B>>

Next, fabrication methods of the devices8B and9B are described. The devices8B and9B were fabricated using the same materials as the devices8A and9A, respectively, through a continuous vacuum process.

Specifically, the devices8B and9B were fabricated in a manner similar to those of the devices8A and9A up to and including the step of forming the second electron-transport layer918.

Here, without breaking the vacuum, over the second electron-transport layer918, lithium fluoride (LiF) and ytterbium (Yb) were deposited to a thickness of 1.5 nm by co-evaporation such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer919was formed.

Next, without breaking the vacuum, over the electron-injection919, Ag and Mg were deposited to a thickness of 15 nm by co-evaporation such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode902was formed. Note that the second electrode902is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.

After that, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited to a thickness of 70 nm by evaporation as a cap layer.

Through the above steps, the devices8B and9B were fabricated.

The following table shows the device structures of the devices (the devices8A,8B, A,9A, and9B.

Through the above steps, the devices were fabricated.

The devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the devices and UV treatment and heat treatment at 80° C. for 1 hour were performed at the time of sealing). Then, the characteristics of the devices were measured.

FIG.39shows the luminance-current density characteristics of the devices.FIG.40shows the luminance-voltage characteristics thereof.FIG.41shows the current efficiency-current density characteristics thereof.FIG.42shows the current density-voltage characteristics thereof.FIG.43shows the emission spectra thereof.

The following table shows the main characteristics of the devices at a current density of 50 mA/cm2. Note that luminance, CIE chromaticity, and the electroluminescence spectra were measured with a spectroradiometer (SR-UL1R manufactured by TOPCON TECHNOHOUSE CORPORATION).

There was almost no difference in voltage at 50 mA/cm2between the devices8A and8B. By contrast, the difference in voltage at 50 mA/cm2between the devices9A and9B was as large as 2.5 V.

FIGS.39to42and Table 6 show that, even when fabricated through the process involving exposure to the air and the chemical solution and the etching process (what is called the MML process), the device8A has favorable device characteristics equivalent to those of the device8B fabricated though a continuous vacuum process. That is, the device8A of one embodiment of the present invention is found to be highly resistant to the process involving exposure to the air and the chemical solution and the etching process.

The above results reveal that the use of one embodiment of the present invention enables provision of a light-emitting device having high resistance to a process involving exposure to the air and a chemical solution and an etching process and having favorable device characteristics.

A reliability test was performed on the devices8A and9A.FIG.44shows time dependence of change in luminance (%) at the time of constant current density driving (50 mA/cm2) when the luminance at the start of light emission is regarded as 100%.

FIG.44also shows that LT90 (h), which is a time taken until the measurement luminance decreases to 90% of the initial luminance, of the device8A fabricated using one embodiment of the present invention is 110 hours. In addition, the LT90 (h) of the device9A is 87 hours.

It is found fromFIG.44that the device8A has highly reliable device characteristics even when fabricated through the process involving exposure to the air and the chemical solution and the etching process (what is called the MML process). Accordingly, the device8A of one embodiment of the present invention is found to be highly resistant to the process involving exposure to the air and the chemical solution and the etching process.

That is, with the use of one embodiment of the present invention, a device can have high reliability even when fabricated through the process involving exposure to the air and the chemical solution and the etching process.

This application is based on Japanese Patent Application Serial No. 2022-127384 filed with Japan Patent Office on Aug. 9, 2022, the entire contents of which are hereby incorporated by reference.