Organic light-emitting display device

An organic light-emitting display device including a thin film transistor (TFT) on a substrate; an organic light emitting diode (OLED) electrically connected to the TFT, the OLED including a pixel electrode, an organic layer, and an opposite electrode; a pixel defining layer (PDL) on the pixel electrode, the PDL including an opening that exposes at least one portion of the pixel electrode; and a light scattering layer between the pixel electrode and the organic layer.

BACKGROUND

1. Field of the Invention

Embodiments relate to an organic light-emitting display device, and more particularly, to an organic light-emitting display device having an improved outdoor visibility and luminescent efficiency, and a method of manufacturing the organic light-emitting display device.

2. Description of the Related Art

An organic light-emitting display device is an active matrix type display device having a wide viewing angle, high contrast, and quick response time. Accordingly, the organic light-emitting display device may be applied to mobile display devices including a digital camera, a video camera, a camcorder, a portable information terminal, a smart phone, an ultra-slim notebook, a tablet personal computer, and a flexible display device, or to electronic/electric products such as an ultra-slim television.

The organic light-emitting display device may realize colors via a process in which a hole and an electron that are inserted into an anode and a cathode are recombined in an emission layer (EML) and emit light. In this regard, when an exciton (that is the combination of the inserted hole and electron) returns from an excited state to a ground state, light emission occurs. The organic light-emitting display device has a stack structure in which the EML is inserted between the anode and the cathode.

SUMMARY

Embodiments are directed to an organic light-emitting display device.

According to an embodiment, there is provided an organic light-emitting display device including a thin film transistor (TFT) formed on a substrate; an organic light emitting diode (OLED) electrically connected to the TFT, and comprising a pixel electrode, an organic layer, and an opposite electrode; and a pixel defining layer (PDL) comprising an opening to expose at least one portion of the pixel electrode, and covering the pixel electrode, wherein a light scattering layer is formed between the pixel electrode and the organic layer.

The light scattering layer may include particles that correspond to a residual layer of the PDL formed on a surface of the pixel electrode, and a conductive layer that covers the particles.

The conductive layer may have unevenness.

Protrusions having a bulged micro-lens shape may be formed on a surface of the conductive layer while the protrusions vertically correspond to the particles.

The conductive layer may be formed of a metal nano ink.

The conductive layer may be formed to cover the particles by using a coating method or a printing method.

A plasma treatment, an ultraviolet treatment, or an ozone treatment may be performed on the surface of the pixel electrode on which the particles are arrayed.

The light scattering layer may include particles that correspond to a residual layer of the PDL formed on a surface of the pixel electrode, wherein the particles have unevenness formed via a graft polymerization.

The particles may be covered by a planarization layer.

The light scattering layer may include particles that correspond to a residual layer of the PDL formed on a surface of the pixel electrode, wherein the particles have unevenness formed by graft-polymerizing an intermediate layer.

A surface treatment may be performed on the pixel electrode on which the particles are arrayed.

The intermediate layer may include a polyimide component obtained by polymerizing polyamic acid.

The TFT may include a semiconductor active layer, a gate electrode, source and drain electrodes, and a plurality of insulating layers interposed therebetween, and, the pixel electrode may be electrically connected to one of the source and drain electrodes.

The pixel electrode may include a first electrode that includes a transparent conductive material, and a second electrode that is formed on the first electrode and includes a metal material.

The first conductive layer may include at least one material selected from the group of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

The first conductive layer may be externally exposed via the opening of the PDL, and the light scattering layer and the organic layer may be stacked on the first conductive layer.

DETAILED DESCRIPTION

Korean Patent Application No. 10-2012-0022032, filed on Mar. 2, 2012, in the Korean Intellectual Property Office, and entitled, “Organic Light-Emitting Display Device,” is incorporated by reference herein in its entirety.

Particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the embodiments to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the embodiments are encompassed in the embodiments. In the description of the embodiments, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention.

An organic light-emitting display device according to an embodiment will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant explanations may be omitted.

FIG. 1illustrates a cross-sectional view of an organic light-emitting display device100according to an embodiment.FIG. 2illustrates a flowchart of a process of forming a light scattering layer120ofFIG. 1.

Referring toFIGS. 1 and 2, a substrate101may be arranged in the organic light-emitting display device100. The substrate101may include, e.g., a glass substrate or a plastic substrate formed of materials including polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), or the like.

If the organic light-emitting display device100is a bottom emission type organic light-emitting display device (in which an image is realized toward the substrate101), the substrate101may be formed of a transparent material. On the other hand, if the organic light-emitting display device100is a top emission type organic light-emitting display device (in which an image is realized away from the substrate101), the substrate101may not have to be formed of a transparent material. For example, the substrate101may be formed of a metal material or other non-transparent material.

When the substrate101is formed of a metal material or other non-transparent material, the substrate101may include, e.g., at least one selected from the group of carbon, iron, chromium, manganese, nickel, titanium, molybdenum, stainless steel (SUS), Invar alloys, Inconel alloys, and Kovar alloys. In an implementation, the substrate101may also be formed of a metal foil.

A buffer layer102may be formed on the substrate101. The buffer layer102may form a planar surface on the substrate101and may help prevent moisture or foreign substances from penetrating into the substrate101. The buffer layer102may be formed of, e.g., SiO2, SiNx, or the like. The buffer layer102may be deposited by a deposition method including, e.g., a plasma enhanced chemical vapor deposition (PECVD) method, an atmospheric pressure CVD (APCVD) method, a low pressure CVD (LPCVD) method, or the like.

A semiconductor active layer106may be patterned on the buffer layer102. In a case where the semiconductor active layer106is formed of polysilicon, amorphous silicon may be formed and then may be crystallized to become polysilicon.

In order to crystallize amorphous silicon, a method including, e.g., a rapid thermal annealing (RTA) method, a solid phase crystallization (SPC) method, an excimer laser annealing (ELA) method, a metal induced crystallization (MIC) method, a metal induced lateral crystallization (MILC) method, a sequential lateral solidification (SLS) method, or the like, may be used.

A source region107and a drain region108may be formed in the semiconductor active layer106by being doped with an N-type impurity or a P-type impurity. A region between the source region107and the drain region108may be a channel region124that is not doped with an impurity.

A first insulating layer103may be formed on the semiconductor active layer106. The first insulating layer103may have, e.g., a single-layer structure including SiO2or a double-layer structure including SiO2and SiNx.

A gate electrode119may be formed on a predetermined region of the first insulating layer103. The gate electrode119may include a first conductive layer112and a second conductive layer113on the first conductive layer112. For example, the gate electrode119may include the first conductive layer112including a transparent conductive material, and the second conductive layer113including a metal material.

The first conductive layer112may be formed on the first insulating layer103. The first conductive layer112may help improve adhesion between the first insulating layer103and the second conductive layer113. The first conductive layer112may include, e.g., at least one material selected from the group of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

The second conductive layer113may be formed on the first conductive layer112and may function as a line for delivering an electrical signal. The second conductive layer113may have a single-layer or multiple-layer structure including at least one metal material selected from the group of aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu).

For example, the second conductive layer113may include a first layer113aformed of Mo, a second layer113bon the first layer113aand formed of Al, and a third layer113con the second layer113band formed of Mo. When the second conductive layer113has a Mo/Al/Mo structure, Al may function a line or an electrode, and Mo may function a barrier layer.

A capacitor114may be formed and may be separate from the semiconductor active layer106. The capacitor114may include a capacitor lower electrode115and a capacitor upper electrode116.

The capacitor lower electrode115may be formed on the buffer layer102. For example, the capacitor lower electrode115may be formed on the same layer as the semiconductor active layer106. The capacitor lower electrode115may be formed of, e.g., an inorganic semiconductor such as amorphous silicon or polysilicon, or an organic semiconductor.

The capacitor upper electrode116may be formed on the first insulating layer103. The capacitor upper electrode116may be formed at a position that vertically corresponds to the capacitor lower electrode115, and maybe formed on a same layer as the gate electrode119. The capacitor upper electrode116may be insulated from the capacitor lower electrode115by having the first insulating layer103interposed therebetween.

The capacitor upper electrode116may be formed of a same material and may have a same structure as that of the first conductive layer112of the gate electrode119. Thus, the capacitor upper electrode116may correspond to the first conductive layer112and may include a transparent conductive material.

As described above, the capacitor lower electrode115may be formed on the same layer as the semiconductor active layer106, and the capacitor upper electrode116may be formed on the same layer as the gate electrode119, so that a thickness of the organic light-emitting display device100may be efficiently decreased.

Furthermore, a pixel electrode109may be formed on a same layer as the gate electrode119. For example, the pixel electrode109may be formed on the first insulating layer103and may be separate from the gate electrode119. The pixel electrode109may include a first electrode110and a second electrode111on the first electrode110.

The first electrode110may be formed on a same layer as the first conductive layer112of the gate electrode119. The first electrode110and an opposite electrode118(described in greater detail below) may supply electricity to an organic layer123. The first electrode110may include, e.g., at least one material selected from the group of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

The second electrode111may be formed on a same layer as the second conductive layer113of the gate electrode119. The second electrode111may have a single-layer or multiple-layer structure including at least one metal material selected from the group of aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu).

For example, the second electrode111may include a first layer111aformed of Mo, a second layer111bon the first layer111aand formed of Al, and a third layer111con the second layer111band formed of Mo.

The second electrode111may include a first opening h1for exposing a portion of the first electrode110. The second electrode111may be electrically connected to one of the source and drain electrodes117(described in greater detail below) and may transmit an electrical signal from a thin film transistor (TFT) to the pixel electrode109.

A second insulating layer104may be formed on the gate electrode119and the pixel electrode109. The second insulating layer104may planarize a top surface of a TFT region including the gate electrode119and a top surface of a region including the pixel electrode109, and may insulate the gate electrode119from the source and drain electrodes117.

The second insulating layer104may be formed of various insulating materials. For example, the second insulating layer104may include an inorganic material such as an oxide or a nitride, or an organic material. In an implementation, the second insulating layer104may include an inorganic insulating layer, e.g., SiO2, SiNx, SiON, Al2O3, TiO2, Ta2O5, HfO2, ZrO2, BST, PZT, or the like, or may an organic insulating layer, e.g., polymer derivatives having commercial polymers (PMMA and PS) and a phenol group, an acryl-based polymer, an imide-based polymer, an allyl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinylalcohol-based polymer, or a combination thereof. The second insulating layer104may be formed as a multi-stack including the inorganic insulating layer and the organic insulating layer. The second insulating layer104may be formed by using, e.g., a spin coating method or the like.

The second insulating layer104may include a second opening h2that corresponds to the first opening h1. The first opening h1may be exposed via the second opening h2. In an implementation, the second insulating layer104may include contact holes for exposing the source region107and the drain region108of the semiconductor active layer106.

The source and drain electrodes117may respectively contact the source region107and the drain region108of the semiconductor active layer106via the contact holes. In an implementation, one of the source and drain electrodes117may be electrically connected to the second electrode111of the pixel electrode109.

The source and drain electrodes117may be formed by patterning a metal layer. The metal layer may have a multiple-layer structure. For example, the source and drain electrodes117may have a single-layer or multiple-layer structure including at least one metal material selected from the group of aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu).

A pixel defining layer (PDL)105may be formed on the source and drain electrodes117. The PDL105may be formed of an organic material or an inorganic material. The PDL105may include a third opening h3. The third opening h3may contact the first opening h1and the second opening h2or may be formed in the first opening h1and the second opening h2. The first electrode110of the pixel electrode109may be exposed via the third opening h3.

The organic layer123may contact the first electrode110of the pixel electrode109which is exposed via the first electrode110. The organic layer123may emit light by being electrically driven by the pixel electrode109and the opposite electrode118.

An emission layer (EML) of the organic layer123may be formed of a low molecular weight organic material or a polymer organic material.

When the organic layer123is formed of a low molecular weight organic material, the organic layer123may have a structure in which a hole injection layer (HIL), a hole transport layer (HTL), an EML, an electron transport layer (ETL), an electron injection layer (EIL), or the like are singularly or multiply stacked, and may be formed by using one of various organic materials including copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), tris-8-hydroxyquinoline aluminum)(Alq3), or the like.

When the organic layer123is formed of a polymer organic material, the organic layer123may include an HTL and an EML. The HTL may be formed of PEDOT, and the EML may be formed of a poly-phenylenevinylene-based polymer organic material or a polyfluorene-based polymer organic material.

A type of the organic layer123is not limited thereto and thus various examples may be applied thereto. In an implementation, the organic layer123may be formed on the pixel electrode109by using, e.g., an inkjet printing method, a spin coating method, or the like.

The opposite electrode118may be formed on the organic layer123. The opposite electrode118may face the pixel electrode109by having the organic layer123interposed therebetween. The opposite electrode118may be formed by depositing a small work function metal material including, e.g., silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), lead (Pb), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), or a compound of any of these, and then by depositing a transparent conductive material thereon. For example, the transparent conductive material may include ITO, IZO, ZnO, In2O3, or the like.

An encapsulation member (not shown) may be further formed on the opposite electrode118. The encapsulation member may help protect the organic layer123and other layers against moisture or oxygen from the outside, and may be formed of a transparent material. For example, the encapsulation member may include a plastic material or may have a composite-layer structure including an organic material and an inorganic material.

When some types of organic light-emitting display devices emit light, only 20% of the light is externally emitted, and 80% of the light may be lost internally. According to an embodiment, the light scattering layer120may be formed in a pixel region so as to improve luminescent efficiency.

The light scattering layer120may be formed between the organic layer123and the first electrode110of the pixel electrode109. The light scattering layer120may include particles121and a conductive layer122covering the particles121.

When the PDL105is patterned, the PDL105may not only be formed in a desired region. For example, a residual layer (e.g., remnants of material that remain after forming the PDL105) having a thickness equal to or less than several tens of Å may remain in another region, e.g., on a surface of the first electrode110. A minute scattering structure may be achieved by not removing the particles121, e.g., the residual layer, and by performing surface modification on the particles121.

In order to cover the particles121, the conductive layer122may be formed on the surface of the first electrode110externally exposed via the third opening h3. The conductive layer122may be formed of a metal nano ink, e.g., an ITO nano ink, a silver nano ink, a nickel nano ink, or the like.

The conductive layer122may be formed by using, e.g., a coating method such as a slit coating method or a spin coating method, or by using a printing method such as an inkjet printing method or a nozzle printing method. When the conductive layer122is printed, a temperature of a base plate on which the organic light-emitting display device100is mounted may remain at about 30° C.

In an implementation, when the conductive layer122is printed, portions thereof overlying the particles121may bulge at a surface of the conductive layer122due to existence of the particles121(compared to portions in which the particles121are not formed). In this manner, protrusions122ahaving a bulged micro-lens shape may be formed on a surface of the conductive layer122. For example, the protrusions122amay vertically correspond to or may be vertically aligned with the particles121.

After the printing operation, a baking process may be performed at about 80° C., and then a sintering process may be performed, so that the light scattering layer120may be formed.

As described above, the light scattering layer120may be formed in a manner such that the conductive layer122has the protrusions122athat have the bulged micro-lens shape and that correspond to or are vertically aligned with the particles121(e.g., residual portions of the PDL105). For example, the residual layer may remain on the surface of the first electrode110when the PDL105is formed, so that the light scattering layer120may scatter light generated in the organic layer123. Accordingly, outdoor visibility and a luminescent efficiency with respect to all wavelength bands may be improved in the organic light-emitting display device100.

FIG. 3illustrates a perspective view of a stage in which a light scattering layer is formed, according to an embodiment.FIG. 4illustrates a perspective view of a stage in a method in which a planarization layer is formed on the light scattering layer ofFIG. 3.FIG. 5illustrates a flowchart of a process of forming the light scattering layer ofFIG. 3.

Here, only elements of the organic light-emitting display device100ofFIG. 1which are related to the light scattering layer are described, and descriptions regarding the other elements may be omitted.

Referring toFIGS. 3 through 5, a first electrode302may be formed on the substrate301. The first electrode302may correspond to the first electrode110of the pixel electrode109ofFIG. 1.

The first electrode302may include at least one material selected from the group of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

The particles303may be formed on the first electrode302. The particles303may correspond to a residual layer of a PDL (refer to the PDL105ofFIG. 1) which remains on a surface of the first electrode302when the PDL (that exposes portions of the first electrode302and simultaneously covers the first electrode302) is formed. A size of each particle303may be equal to or less than several tens of Å.

In an implementation, the PDL105may not be in a polymer state but rather may be in an oligomer state. Thus, the particles303may have a minute uneven structure via a graft polymerization process using an initiator such as imidazole.

In an implementation, the particles303may be formed of a polymer material, e.g., polyimide. Thus, the particles303may have low adhesion with respect to a metal material and the particles303may be graft-polymerized. Via the graft polymerization, a surface of each particle303may be modified, so that the particles303may have unevenness that is equal to or greater than 100 Å. The particles303may perform a function of the light scattering layer.

After the particles303(having the unevenness of a nano structure) are formed, the planarization layer304may formed to cover the particles303. Surface roughness may adversely affect an efficiency of an organic light-emitting display device. Thus, the planarization layer304may be formed on the particles303so as to make planarization on the particles303.

For example, referring toFIG. 6, an organic layer including an HIL305, an EML306, and an ETL307may be formed on the first electrode302, and an opposite electrode308may be formed on the organic layer.

In an implementation, the planarization layer304may be interposed between the first electrode302and the HIL305. The planarization layer304may include a siloxane-based compound (O—Si—O). The planarization layer304may help maintain surface roughness on the first electrode302at a level equal to or less than 0.5 nm, when the particles303having unevenness are formed on the first electrode302. Thus, it is possible to maintain an electrical characteristic of the HIL305at the same level.

As described above, the particles303having minute unevenness may be formed by graft-polymerizing the residual layer of the PDL105. Thus, the particles303may perform a function of the light scattering layer.

FIG. 7illustrates a flowchart of a process of forming a light scattering layer, according to an embodiment.

The present embodiment is similar to the previous embodiments in that the light scattering layer is formed by using the residual layer of the PDL105and then by performing a thermal treatment at a desired temperature. Thus, features of the present embodiment (ofFIG. 7) will be described.

Referring toFIG. 7, particles may be formed on a first electrode (e.g., a pixel electrode). In this regard, the particles may correspond to a residual layer that remains on the first electrode when a PDL is formed.

Afterward, before an organic layer is deposited, a surface treatment may be performed on the first electrode on which the particles are formed. The surface treatment may include, e.g., an argon plasma treatment. For example, when the surface treatment is performed on the first electrode (on which the particles have been formed), adhesion may be increased via the argon plasma treatment. Thus, the argon plasma treatment may be performed prior to the graft polymerization.

After the argon plasma treatment is performed, selectively, a light scattering layer having an unevenness structure may be formed by graft-polymerizing an intermediate layer, i.e., particles that may react well with the first electrode, by using an initiator such as imidazole. In an implementation, the intermediate layer (that is formed of the particles and that is the residual layer of the PDL) may include a polyimide component obtained by polymerizing polyamic acid. The polyimide component may be a recombination of an outgassed component when polyimide is cured in an oven at a high temperature under a N2atmosphere. In an implementation, the intermediate layer may not be 100% polyimide but may have an intermediate compound in an oligomer state that is an intermediate state of polymer.

FIG. 8illustrates a flowchart of a process of forming a light scattering layer, according to an embodiment.

The present embodiment may be similar to the previous embodiments in that the light scattering layer is formed by using the residual layer of the PDL105and then by performing a thermal treatment at a desired temperature. Thus, the features of the present embodiment (ofFIG. 8) will be described.

Referring toFIG. 8, particles may be formed on a first electrode. The particles may correspond to a residual layer of a PDL that remains on an exposed surface of the first electrode, when the PDL is patterned to cover the first electrode (e.g., except for exposed portions of the first electrode).

Then, before an organic layer is deposited on the first electrode, a surface treatment may be performed on the first electrode. In an implementation, the surface treatment may include a plasma treatment, an ultraviolet treatment, or an ozone treatment. In an implementation, an argon plasma treatment may be performed on the particles that remain on the first electrode with only a very small amount. Via the argon plasma treatment, adhesion between the particles and a conductive layer covering the particles may be improved.

Afterward, the conductive layer (including a metal nano ink such as an ITO nano ink, a silver nano ink, a nickel nano-ink, or the like) may be formed on the first electrode. In an implementation, the conductive layer may be formed by using a printing method such as an inkjet printing method.

Accordingly, protrusions having a bulged micro-lens shape may be formed on a surface of the conductive layer. For example, the protrusions may vertically correspond to or may be vertically aligned with the particles, so that the particles may perform a function of the light scattering layer.

By way of summation and review, it may be difficult to obtain highly efficient emission via a stack structure. Thus, intermediate layers such as an electron injection layer (EIL), an electron transport layer (ETL), a hole transport layer (HTL), a hole injection layer (HIL), and the like may be selectively inserted therebetween. In an organic light-emitting display device, only 20% of light generated in the EML may be externally emitted, and 80% of the light may be lost internally. Thus, it may be desirable for the organic light-emitting display device to have a structure having an improved luminescent efficiency.

As described above, according to an embodiment, outdoor visibility and a luminescent efficiency with respect to all wavelength bands may be improved in the organic light-emitting display device.