Imaging element and imaging device

An imaging element according to an embodiment of the present disclosure includes: a first electrode; a second electrode that is disposed to be opposed to the first electrode; and an organic layer that is provided between the first electrode and the second electrode. The organic layer includes a compound represented by a general formula (1).

TECHNICAL FIELD

The present disclosure relates to an imaging element in which an organic material is used and an imaging device including this.

BACKGROUND ART

For example, PTL 1 discloses a photoelectric conversion element including an organic layer containing the compound represented by the following general formula (2). R1 and R4 of the compound represented by the general formula (2) are alkyl groups such as methyl groups.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Incidentally, an imaging element in which an organic material is used is requested to have increased spectral characteristics.

It is desirable to provide an imaging element and an imaging device each of which makes it possible to increase spectral characteristics.

An imaging element according to an embodiment of the present disclosure includes: a first electrode; a second electrode that is disposed to be opposed to the first electrode; and an organic layer that is provided between the first electrode and the second electrode. The organic layer includes a compound represented by the following general formula (1):

(where R1 and R4 each independently represent a hydrogen atom or a deuterium atom; R2 and R3 each independently represent an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group; R5 and R6 each independently represent a halogen atom, a hydrogen atom, or a alkyl group; R7 represents an aryl group, a heteroaryl group, or an alkenyl group; M represents boron or an m-valent metal atom and includes at least one of germanium, beryllium, magnesium, aluminum, chromium, iron, nickel, copper, zinc, or platinum; L represents a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; and n represents an integer greater than or equal to 1 and less than or equal to 6 and L's each independently represent a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group in a case where n−1 is 2 or more.)

An imaging device according to an embodiment of the present disclosure includes pixels each including one or more organic photoelectric conversion sections and includes the imaging element according to the embodiment of the present disclosure described above as each of the organic photoelectric conversion sections.

In the imaging element according to the embodiment of the present disclosure and the imaging device according to the embodiment, the organic layer is formed by using the compound represented by the general formula (1) described above. This increases the selectivity for a wavelength detected by the organic layer.

MODES FOR CARRYING OUT THE INVENTION

The following describes an embodiment of the present disclosure in detail with reference to the drawings. The following description is a specific example of the present disclosure, but the present disclosure is not limited to the following modes. In addition, the present disclosure is not also limited to the disposition, dimensions, dimension ratios, and the like of the respective components illustrated in the respective diagrams. It is to be noted that description is given in the following order.

1. First Embodiment

(An example of an imaging element including an organic photoelectric conversion section including an organic layer that includes a BODIPY compound including hydrogen atoms at a first position and a seventh position)

1-1. Configuration of Imaging Element

1-2. Method of Manufacturing Imaging Element

1-3. Workings and Effects

2. Second Embodiment (an example in which two organic photoelectric conversion sections are stacked on a semiconductor substrate)

3. Third Embodiment (an example in which three organic photoelectric conversion sections are stacked on a semiconductor substrate)

4. Application Examples

5. Practical Application Examples

6. Working Examples

1. First Embodiment

FIG.1illustrates an example of a cross-sectional configuration of an imaging element (an imaging element10A) according to a first embodiment of the present disclosure.FIG.2illustrates a planar configuration of the imaging element10A illustrated inFIG.1.FIG.3is an equivalent circuit diagram of the imaging element10A illustrated inFIG.1.FIG.3corresponds to a region100illustrated inFIG.2.FIG.4schematically illustrates the disposition of a lower electrode21and a transistor included in a control section of the imaging element10A illustrated inFIG.1. The imaging element10A is included, for example, in one pixel (a unit pixel P) of an imaging device (an imaging device1; seeFIG.17) such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor used for an electronic apparatus such as a digital still camera or a video camera. The imaging element10A according to the present embodiment includes an organic photoelectric conversion section20in which the lower electrode21, a photoelectric conversion layer24, and an upper electrode25are stacked in this order. The photoelectric conversion layer24detects the band of any of an infrared region and a visible region. The photoelectric conversion layer24is formed by using the compound represented by a general formula (1) described below. This photoelectric conversion layer24corresponds to a specific example of an “organic layer” according to the present disclosure.

(1-1. Configuration of Imaging Element)

The imaging element10A is, for example, a so-called vertical spectroscopic imaging element in which the one organic photoelectric conversion section20and two inorganic photoelectric conversion sections32B and32R are stacked in the vertical direction. The organic photoelectric conversion section20is provided on a first surface (the back surface; a surface30S1) side of a semiconductor substrate30. The inorganic photoelectric conversion sections32B and32R are formed to be buried in the semiconductor substrate30and stacked in the thickness direction of the semiconductor substrate30. The organic photoelectric conversion section20includes the photoelectric conversion layer24between the lower electrode21and the upper electrode25as described above as an organic layer that is formed by using an organic material. The lower electrode21and the upper electrode25are disposed to be opposed to each other. This photoelectric conversion layer24includes a p-type semiconductor and an n-type semiconductor and has a bulk heterojunction structure in the layer. The bulk heterojunction structure is a p/n junction surface formed by mixing a p-type semiconductor and an n-type semiconductor.

The organic photoelectric conversion section20and the inorganic photoelectric conversion sections32B and32R perform photoelectric conversion by selectively detecting the respective wavelengths (the respective pieces of light) of wavelength bands different from each other. For example, the organic photoelectric conversion section20absorbs the wavelength of a green band and acquires a color signal of green (G). The inorganic photoelectric conversion sections32B and32R respectively absorbs the wavelength of a blue band to acquire a color signal of blue (B) and absorbs the wavelength of a red band to acquire a color signal of red (R) because of different absorption coefficients. This allows the imaging element10A to acquire a plurality of types of color signals in one pixel without using any color filters.

It is to be noted that, in the present embodiment, a case is described where the electron of a pair (an electron-hole pair) of an electron and a hole generated by photoelectric conversion is read out as signal charge (a case where an n-type semiconductor region is used as a photoelectric conversion layer). In addition, in the drawings, “+(plus)” attached to “p” and “n” indicates high p-type or n-type impurity concentration.

A second surface (the front surface;30S2) of the semiconductor substrate30is provided, for example, with floating diffusions (floating diffusion layers) FD1(a region36B in the semiconductor substrate30), FD2(a region37C in the semiconductor substrate30), FD3(a region38C in the semiconductor substrate30), transfer transistors Tr2and Tr3, an amplifier transistor (a modulation element) AMP, a reset transistor RST, a selection transistor SEL, and a multilayer wiring layer40. The multilayer wiring layer40has, for example, a configuration in which wiring layers41,42, and43are stacked in an insulating layer44.

It is to be noted that the first surface (the surface30S1) side of the semiconductor substrate30is referred to as light incidence side S1and the second surface (the surface30S2) side is referred to as wiring layer side S2in the drawings.

The organic photoelectric conversion section20includes the lower electrode21, a semiconductor layer23, the photoelectric conversion layer24, and the upper electrode25that are stacked in this order from the first surface (the surface30S1) side of the semiconductor substrate30. In addition, there is provided an insulating layer22between the lower electrode21and the semiconductor layer23. The lower electrodes21are separately formed, for example, for the respective imaging elements10A. Although described in detail below, each of the lower electrodes21includes a readout electrode21A and an accumulation electrode21B that are separated from each other with the insulating layer22interposed in between. The readout electrode21A of the lower electrode21is electrically coupled to the semiconductor layer23through an opening22H provided in the insulating layer22.FIG.1illustrates an example in which the semiconductor layer23, the photoelectric conversion layer24, and the upper electrode25are provided as continuous layers common to the plurality of imaging elements10A, but the semiconductor layers23, the photoelectric conversion layers24, and the upper electrodes25may be separately formed for the respective imaging elements10A. There are provided, for example, a dielectric film26, an insulating film27, and an interlayer insulating layer28between the first surface (the surface30S1) of the semiconductor substrate30and the lower electrode21. There is provided a protective layer51above the upper electrode25. There is provided, for example, a light shielding film52at a position corresponding to the readout electrode21A in the protective layer51. This light shielding film52does not overlap with at least the accumulation electrode21B, but it is sufficient if the light shielding film52is provided to cover the region of the readout electrode21A in direct contact with at least the semiconductor layer23. There are provided optical members such as a planarization layer (not illustrated) and an on-chip lens53above the protective layer51.

There is provided a through electrode34between the first surface (the surface30S1) and the second surface (the surface30S2) of the semiconductor substrate30. This through electrode34is electrically coupled to the readout electrode21A of the organic photoelectric conversion section20and the organic photoelectric conversion section20is coupled to a gate Gamp of the amplifier transistor AMP and the one source/drain region36B of the reset transistor RST (a reset transistor Tr1rst) through the through electrode34. The one source/drain region36B of the reset transistor RST (the reset transistor Tr1rst) also serves as the floating diffusion FD1. This allows the imaging element10A to favorably transfer the electric charge generated in the organic photoelectric conversion section20on the first surface (a surface30S21) side of the semiconductor substrate30to the second surface (the surface30S2) side of the semiconductor substrate30and makes it possible to increase the characteristics.

The lower end of the through electrode34is coupled to a coupling section41A in the wiring layer41and the coupling section41A and the gate Gamp of the amplifier transistor AMP are coupled through a lower first contact45. The coupling section41A and the floating diffusion FD1(the region36B) are coupled, for example, through a lower second contact46. The upper end of the through electrode34is coupled to the readout electrode21A, for example, through an upper first contact29A, a pad section39A, and an upper second contact29B.

The through electrode34is provided, for example, for each of the organic photoelectric conversion sections20in the respective imaging elements10A. The through electrode34has a function of a connector between the organic photoelectric conversion section20and the gate Gamp of the amplifier transistor AMP and the floating diffusion FD1and serves as a transmission path for the electric charge generated in the organic photoelectric conversion section20.

A reset gate Grst of the reset transistor RST is disposed next to the floating diffusion FD1(the one source/drain region36B of the reset transistor RST). This allows the reset transistor RST to reset the electric charge accumulated in the floating diffusion FD1.

In the imaging element10A according to the present embodiment, light entering the organic photoelectric conversion section20from the upper electrode25side is absorbed by the photoelectric conversion layer24. The excitons generated by this move to the interface between an electron donor and an electron acceptor included in the photoelectric conversion layer24and undergo exciton separation. In other words, the excitons are dissociated into electrons and holes. The electric charge (the electrons and the holes) generated here is carried to different electrodes by diffusion resulting from a difference in concentration between carriers or an internal electric field resulting from a difference in work function between an anode (e.g., the upper electrode25) and a cathode (e.g., the lower electrode21) and detected as a photocurrent. In addition, the application of a potential between the lower electrode21and the upper electrode25makes it possible to control the transport direction of electrons and holes.

The following describes configurations, materials, and the like of the respective sections.

The organic photoelectric conversion section20is an organic photoelectric converter that absorbs light corresponding to a wavelength band of a portion or the whole of a selective wavelength band (e.g., 400 nm or more and 700 nm or less) and generates electron-hole pairs.

As described above, the lower electrode21includes the readout electrode21A and the accumulation electrode21B that are separately formed. The readout electrode21A is for transferring the electric charge generated in the photoelectric conversion layer24to the floating diffusion FD1. For example, the readout electrode21A is coupled to the floating diffusion FD1through the upper second contact29B, the pad section39A, the upper first contact29A, the through electrode34, the coupling section41A, and the lower second contact46. The accumulation electrode21B is for accumulating, in the semiconductor layer23as signal charge, the electrons of the electric charge generated in the photoelectric conversion layer24. The accumulation electrode21B is provided in a region that is opposed to the light receiving surfaces of the inorganic photoelectric conversion sections32B and32R formed in the semiconductor substrate30and covers these light receiving surfaces. It is preferable that the accumulation electrode21B be larger than the readout electrode21A. This makes it possible to accumulate a large amount of electric charge. As illustrated inFIG.4, a voltage application circuit60is coupled to the accumulation electrode21B through a wiring line.

The lower electrode21includes an electrically conductive film having light transmissivity. Examples of a material included in the lower electrode21include an indium-tin oxide including indium tin oxide (ITO), In2O3to which tin (Sn) is added as a dopant, crystalline ITO, and amorphous ITO. In addition to the materials described above, a tin oxide (SnO2-based material to which a dopant is added or a zinc oxide-based material to which a dopant is added may be used as a material included in the lower electrode21. Examples of the zinc oxide-based material include an aluminum zinc oxide (AZO) to which aluminum (Al) is added as a dopant, a gallium zinc oxide (GZO) to which gallium (Ga) is added, a boron zinc oxide to which boron (B) is added, and an indium zinc oxide (IZO) to which indium (In) is added. In addition, CuI, InSbO4, ZnMgO, CuInO2, MgIN2O4, CdO, ZnSnO3, TiO2, or the like may be used as a material included in the lower electrode21. Further, a spinel oxide or an oxide having a YbFe2O4structure may be used. It is to be noted that the lower electrode21formed by using any of the materials as described above generally has a high work function and functions as an anode electrode.

The semiconductor layer23is provided in a lower layer of the photoelectric conversion layer24. Specifically, the semiconductor layer23is provided between the insulating layer22and the photoelectric conversion layer24. The semiconductor layer23is for accumulating the signal charge generated in the photoelectric conversion layer24. It is preferable that the semiconductor layer23be formed by using a material having higher electric charge mobility and having a wider band gap than those of the photoelectric conversion layer24. For example, it is preferable that the band gap of a material included in the semiconductor layer23be 3.0 eV or more. Examples of such a material include an oxide semiconductor material such as IGZO, an organic semiconductor material, and the like. Examples of the organic semiconductor material include transition metal dichalcogenide, silicon carbide, diamond, graphene, a carbon nanotube, a fused polycyclic hydrocarbon compound, a fused heterocyclic compound, and the like. The semiconductor layer23has, for example, a thickness of 10 nm or more and 300 nm or less. The semiconductor layer23including the material described above is provided in a lower layer of the photoelectric conversion layer24. This makes it possible to prevent electric charge recombination during electric charge accumulation and increase the transfer efficiency.

The photoelectric conversion layer24converts light energy to electric energy. The photoelectric conversion layer24according to the present embodiment absorbs, for example, light having a portion or all of wavelengths within a range of 400 nm or more and 700 nm or less. The photoelectric conversion layer24includes, for example, two or more types of organic materials that each function as a p-type semiconductor or an n-type semiconductor. The photoelectric conversion layer24has a junction surface (a p/n junction surface) between a p-type semiconductor and an n-type semiconductor in the layer. The p-type semiconductor relatively functions as an electron donor (a donor) and the n-type semiconductor relatively functions an electron acceptor (an acceptor). The photoelectric conversion layer24provides a field where the excitons generated upon light absorption are separated into electrons and holes. Specifically, the excitons are separated into electrons and holes at the interface (the p/n junction surface) between the electron donor and the electron acceptor.

The photoelectric conversion layer24further includes an organic material or a so-called dye material in addition to a p-type semiconductor and an n-type semiconductor. The organic material or the dye material photoelectrically converts light in a predetermined wavelength band and transmits light in another wavelength band. In a case where the photoelectric conversion layer24is formed by using three types of organic materials including a p-type semiconductor, an n-type semiconductor, and a dye material, the p-type semiconductor and the n-type semiconductor are preferably materials having light transmissivity in a visible region (e.g., 400 nm to 700 nm). The photoelectric conversion layer24has, for example, a thickness of 25 nm or more and 400 nm or less. Preferably, the photoelectric conversion layer24has a thickness of 50 nm or more and 350 nm or less. More preferably, the photoelectric conversion layer24has a thickness of 150 nm or more and 300 nm or less.

In the present embodiment, the photoelectric conversion layer24is formed, for example, to include the compound represented by the following general formula (1) as a dye material. This compound represented by the general formula (1) is a BODIPY dye that has, for example, electron acceptability and absorbs, for example, light of 450 nm or more and 650 nm or less.

(where R1 and R4 each independently represent a hydrogen atom or a deuterium atom; R2 and R3 each independently represent an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group; R5 and R6 each independently represent a halogen atom, a hydrogen atom, or a alkyl group; R7 represents an aryl group, a heteroaryl group, or an alkenyl group; M represents boron or an m-valent metal atom and includes at least one of germanium, beryllium, magnesium, aluminum, chromium, iron, nickel, copper, zinc, or platinum; L represents a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; and n represents an integer greater than or equal to 1 and less than or equal to 6 and L's each independently represent a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group in a case where n−1 is 2 or more.)

As a specific example of the compound represented by the general formula (1) described above, for example, the compounds represented by the following formulas (1-1) to (1-28) are included.

Examples of another organic material included in the photoelectric conversion layer24include fullerene or a fullerene derivative. Further, examples of another organic material included in the photoelectric conversion layer24include a thiophene derivative in which benzodithiophene (BDT) is a mother skeleton or a chrysene derivative having a chrysene skeleton.

The organic materials described above function as a p-type semiconductor or an n-type semiconductor depending on a combination thereof.

It is to be noted that the photoelectric conversion layer24may include an organic material other than the materials described above. As an organic material other than the materials described above, for example, any one of quinacridone, subphthalocyanine, pentacene, benzothienobenzothiophene, naphthalene, anthracene, phenanthrene, tetracene, pyrene, perylene, fluoranthene, and derivatives thereof is favorably used. Alternatively, a polymer such as phenylenevinylene, fluorene, carbazole, indole, pyrrole, picoline, thiophene, acetylene, or diacetylene or a derivative thereof may be used. Additionally, it is possible to preferably use a metal complex dye, a cyanine-based dye, a merocyanine-based dye, a phenylxanthene-based dye, a triphenylmethane-based dye, a rhodacyanine-based dye, a xanthene-based dye, a macrocyclic azaannulene-based dye, an azulene-based dye, naphthaquinone, an anthraquinone-based dye, a chain compound in which a fused polycyclic aromatic group such as anthracene and pyrene and an aromatic ring or a heterocyclic compound are condensed, a cyanine-like dye bonded by two nitrogen-containing hetero rings such as quinoline, benzothiazole, and benzoxazole that have a squarylium group and a croconic methine group as a bonded chain or by a squarylium group and a croconic methine group, or the like. It is to be noted that a dithiol metal complex-based dye, a metallophthalocyanine dye, a metalloporphyrine dye, or a ruthenium complex dye is preferable as the metal complex dye described above, but this is not limitative.

As with the lower electrode21, the upper electrode25includes an electrically conductive film having light transmissivity. In the imaging device1in which the imaging element10A is used as one pixel, the upper electrodes25may be separated for the respective pixels or formed as an electrode common to the respective pixels. The upper electrode25has, for example, a thickness of 10 nm to 200 nm.

There may be provided other layers between the semiconductor layer23and the photoelectric conversion layer24and between the photoelectric conversion layer24and the upper electrode25as organic layers in addition to the photoelectric conversion layer24.

For example, as in an imaging element10B illustrated inFIG.5, the semiconductor layer23, a hole block layer24A, the photoelectric conversion layer24, and an electron block layer24B may be stacked in order from the lower electrode21side. The compound represented by the general formula (1) described above that has been mentioned as a material included, for example, in the photoelectric conversion layer24is usable for the hole block layer24A and the electron block layer24B.

Further, there may be provided an underlying layer and a hole transport layer between the lower electrode21and the photoelectric conversion layer24and there may be provided a work function adjustment layer, a buffer layer, or an electron transport layer between the photoelectric conversion layer24and the upper electrode25.

The insulating layer22is for electrically separating the accumulation electrode21B and the semiconductor layer23. The insulating layer22is provided, for example, on the interlayer insulating layer28to cover the lower electrode21. In addition, the insulating layer22is provided with the opening22H above the readout electrode21A of the lower electrode21. The readout electrode21A and the semiconductor layer23are electrically coupled through this opening22H. The insulating layer22includes, for example, a single layer film including one of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), and the like or a stacked film including two or more of them. The insulating layer22has, for example, a thickness of 20 nm to 500 nm.

The dielectric film26is for preventing the reflection of light caused by a refractive index difference between the semiconductor substrate30and the insulating film27. It is preferable that a material of the dielectric film26be a material having a refractive index between the refractive index of the semiconductor substrate30and the refractive index of the insulating film27. Further, it is preferable that a material allowing a film to be formed having, for example, negative fixed electric charge be used as a material of the dielectric film26. Alternatively, it is preferable that a semiconductor material or an electrically conductive material having a wider band gap than that of the semiconductor substrate30be used as a material of the dielectric film26. This makes it possible to suppress the generation of dark currents at the interface of the semiconductor substrate30. Such a material includes hafnium oxide (HfOx), aluminum oxide (AlOx), zirconium oxide (ZrOx), tantalum oxide (TaOx), titanium oxide (TiOx), lanthanum oxide (LaOx), praseodymium oxide (PrOx), cerium oxide (CeOx), neodymium oxide (NdOx), promethium oxide (PmOx), samarium oxide (SmOx), europium oxide (EuOx), gadolinium oxide (GdOx), terbium oxide (TbOx), dysprosium oxide (DyOx), holmium oxide (HoOx), thulium oxide (TmOx), ytterbium oxide (YbOx), lutetium oxide (LuOx), yttrium oxide (YOx), hafnium nitride (HfNx), aluminum nitride (AlNx), hafnium oxynitride (HfOxNy), aluminum oxynitride (AlOxNy), and the like.

The insulating film27is provided on the dielectric film26that is formed on the first surface (the surface30S1) of the semiconductor substrate30and a side surface of a through hole30H. The insulating film27is for electrically insulating the through electrode34and the semiconductor substrate30. Examples of a material of the insulating film27include silicon oxide (SiOx), TEOS, silicon nitride (SiNx), silicon oxynitride (SiON), and the like.

The interlayer insulating layer28includes, for example, a single layer film including one of silicon oxide (SiOx), TEOS, silicon nitride (SiNx), silicon oxynitride (SiON), and the like or a stacked film including two or more of them.

The protective layer51includes a material having light transmissivity. The protective layer51includes, for example, a single layer film including any of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), and the like or a stacked film including two or more of them. The protective layer51has, for example, a thickness of 100 nm to 30000 nm.

The semiconductor substrate30includes, for example, an n-type silicon (Si) substrate and includes a p well31in a predetermined region (e.g., a pixel section1a). The second surface (the surface30S2) of the p well31is provided with the transfer transistors Tr2and Tr3described above, the amplifier transistor AMP, the reset transistor RST, a selection transistor SEL, and the like. In addition, a peripheral portion (a peripheral portion1b) of the semiconductor substrate30is provided, for example, with a pixel readout circuit110and a pixel drive circuit120each including a logic circuit and the like as illustrated inFIG.2.

The reset transistor RST (the reset transistor Tr1rst) is for resetting the electric charge transferred from the organic photoelectric conversion section20to the floating diffusion FD1and includes, for example, a MOS transistor. Specifically, the reset transistor Tr1rst includes the reset gate Grst, a channel formation region36A, and the source/drain regions36B and36C. The reset gate Grst is coupled to a reset line RST1. The one source/drain region36B of the reset transistor Tr1rst also serves as the floating diffusion FD1. The other source/drain region36C included in the reset transistor Tr1rst is coupled to a power supply line VDD.

The amplifier transistor AMP is a modulation element that modulates, into voltage, the amount of electric charge generated in the organic photoelectric conversion section20and includes, for example, a MOS transistor. Specifically, the amplifier transistor AMP includes the gate Gamp, a channel formation region35A, and the source/drain regions35B and35C. The gate Gamp is coupled to the readout electrode21A and the one source/drain region36B (the floating diffusion FD1) of the reset transistor Tr1rst through the lower first contact45, the coupling section41A, the lower second contact46, the through electrode34, and the like. In addition, the one source/drain region35B shares a region with the other source/drain region36C included in the reset transistor Tr1rst and is coupled to the power supply line VDD.

The selection transistor SEL (the selection transistor TR1sel) includes a gate Gsel, a channel formation region34A, and the source/drain regions34B and34C. The gate Gsel is coupled to a selection line SELL The one source/drain region34B shares a region with the other source/drain region35C included in the amplifier transistor AMP and the other source/drain region34C is coupled to a signal line (a data output line) VSL1.

The inorganic photoelectric conversion sections32B and32R each have a pn junction in a predetermined region of the semiconductor substrate30. The inorganic photoelectric conversion sections32B and32R each allow light to be dispersed in the vertical direction because the respective pieces of light having different wavelengths are absorbed in accordance with the light incidence depth in a silicon substrate. The inorganic photoelectric conversion section32B selectively detects blue light to accumulate the signal charge corresponding to blue and is installed at depth that allows the blue light to be photoelectrically converted efficiently. The inorganic photoelectric conversion section32R selectively detects red light to accumulate the signal charge corresponding to red and is installed at depth that allows the red light to be photoelectrically converted efficiently. It is to be noted that blue (B) is a color corresponding, for example, to a wavelength band of 430 nm to 480 nm and red (R) is a color corresponding, for example, to a wavelength band of 600 nm to 750 nm. It is sufficient if the inorganic photoelectric conversion sections32B and32R are able to detect pieces of light of a portion or all of the respective wavelength bands.

The inorganic photoelectric conversion section32B includes, for example, a p+ region serving as a hole accumulation layer and an n region serving as an electron accumulation layer. The inorganic photoelectric conversion section32R includes, for example, a p+ region serving as a hole accumulation layer and an n region serving as an electron accumulation layer (has a p-n-p stacked structure). The n region of the inorganic photoelectric conversion section32B is coupled to the vertical transfer transistor Tr2. The p+ region of the inorganic photoelectric conversion section32B is bent along the transfer transistor Tr2and leads to the p+ region of the inorganic photoelectric conversion section32R.

The transfer transistor Tr2(a transfer transistor TR2trs) is for transferring, to the floating diffusion FD2, the signal charge corresponding to blue and generated and accumulated in the inorganic photoelectric conversion section32B. The inorganic photoelectric conversion section32B is formed at a deep position from the second surface (the surface30S2) of the semiconductor substrate30and it is thus preferable that the transfer transistor TR2trs of the inorganic photoelectric conversion section32B include a vertical transistor. The transfer transistor TR2trs is coupled to a transfer gate line TG2. The floating diffusion FD2is provided in the region37C near a gate Gtrs2of the transfer transistor TR2trs. The electric charge accumulated in the inorganic photoelectric conversion section32B is read out to the floating diffusion FD2through a transfer channel formed along the gate Gtrs2.

The transfer transistor Tr3(a transfer transistor TR3trs) is for transferring, to the floating diffusion FD3, the signal charge corresponding to red and generated and accumulated in the inorganic photoelectric conversion section32R. The transfer transistor Tr3(the transfer transistor TR3trs) includes, for example, a MOS transistor. The transfer transistor TR3trs is coupled to a transfer gate line TG3. The floating diffusion FD3is provided in the region38C near a gate Gtrs3of the transfer transistor TR3trs. The electric charge accumulated in the inorganic photoelectric conversion section32R is read out to the floating diffusion FD3through a transfer channel formed along the gate Gtrs3.

There are further provided a reset transistor TR2rst, an amplifier transistor TR2amp, and a selection transistor TR2sel on the second surface (the surface30S2) side of the semiconductor substrate30. The reset transistor TR2rst, the amplifier transistor TR2amp, and the selection transistor TR2sel are included in the control section of the inorganic photoelectric conversion section32B. Further, there are provided a reset transistor TR3rst, an amplifier transistor TR3amp, and a selection transistor TR3sel. The reset transistor TR3rst, the amplifier transistor TR3amp, and the selection transistor TR3sel are included in the control section of the inorganic photoelectric conversion section32R.

The reset transistor TR2rst includes a gate, a channel formation region, and a source/drain region. The gate of the reset transistor TR2rst is coupled to a reset line RST2and the one source/drain region of the reset transistor TR2rst is coupled to the power supply line VDD. The other source/drain region of the reset transistor TR2rst also serves as the floating diffusion FD2.

The amplifier transistor TR2amp includes a gate, a channel formation region, and a source/drain region. The gate is coupled to the other source/drain region (the floating diffusion FD2) of the reset transistor TR2rst. The one source/drain region included in the amplifier transistor TR2amp shares a region with the one source/drain region included in the reset transistor Tr2rst and is coupled to the power supply line VDD.

The selection transistor TR2sel includes a gate, a channel formation region, and a source/drain region. The gate is coupled to a selection line SEL2. The one source/drain region included in the selection transistor TR2sel shares a region with the other source/drain region included in the amplifier transistor TR2amp. The other source/drain region included in the selection transistor TR2sel is coupled to a signal line (a data output line) VSL2.

The reset transistor TR3rst includes a gate, a channel formation region, and a source/drain region. The gate of the reset transistor TR3rst is coupled to a reset line RST3and the one source/drain region included in the reset transistor TR3rst is coupled to the power supply line VDD. The other source/drain region included in the reset transistor TR3rst also serves as the floating diffusion FD3.

The amplifier transistor TR3amp includes a gate, a channel formation region, and a source/drain region. The gate is coupled to the other source/drain region (the floating diffusion FD3) included in the reset transistor TR3rst. The one source/drain region included in the amplifier transistor TR3amp shares a region with the one source/drain region included in the reset transistor Tr3rst and is coupled to the power supply line VDD.

The selection transistor TR3sel includes a gate, a channel formation region, and a source/drain region. The gate is coupled to a selection line SEL3. The one source/drain region included in the selection transistor TR3sel shares a region with the other source/drain region included in the amplifier transistor TR3amp. The other source/drain region included in the selection transistor TR3sel is coupled to a signal line (a data output line) VSL3.

The reset lines RST1, RST2, and RST3, the selection lines SEL1, SEL2, and SEL3, and the transfer gate lines TG2and TG3are each coupled to a vertical drive circuit included in a drive circuit. The signal lines (the data output lines) VSL1, VSL2, and VSL3are coupled to a column signal processing circuit included in the drive circuit.

The lower first contact45, the lower second contact46, the upper first contact29A, the upper second contact29B, and an upper third contact29C each include, for example, a doped silicon material such as PDAS (Phosphorus Doped Amorphous Silicon) or a metal material such as aluminum (Al), tungsten (W), titanium (Ti), cobalt (Co), hafnium (Hf), or tantalum (Ta).

(1-2. Method of Manufacturing Imaging Element)

It is possible to manufacture the imaging element10A according to the present embodiment, for example, as follows.

FIGS.6to10illustrate a method of manufacturing the imaging element10A in the order of steps. First, as illustrated inFIG.6, for example, the p well31is formed as a well of a first electrical conduction type in the semiconductor substrate30. The inorganic photoelectric conversion sections32B and32R of a second electrical conduction type (e.g., an n type) are formed in this p well31. A p+ region is formed near the first surface (the surface30S1) of the semiconductor substrate30.

As also illustrated inFIG.6, for example, n+ regions that serve as the floating diffusions FD1to FD3are formed on the second surface (the surface30S2) of the semiconductor substrate30and a gate insulating layer33and a gate wiring layer47are then formed. The gate wiring layer47includes the respective gates of the transfer transistor Tr2, the transfer transistor Tr3, the selection transistor SEL, the amplifier transistor AMP, and the reset transistor RST. This forms the transfer transistor Tr2, the transfer transistor Tr3, the selection transistor SEL, the amplifier transistor AMP, and the reset transistor RST. Further, the multilayer wiring layer40is formed on the second surface (the surface30S2) of the semiconductor substrate30. The multilayer wiring layer40includes the wiring layers41to43and the insulating layer44. The wiring layers41to43include the lower first contact45, the lower second contact46, and the coupling section41A.

As the base of the semiconductor substrate30, for example, an SOI (Silicon on Insulator) substrate is used in which the semiconductor substrate30, a buried oxide film (not illustrated), and a holding substrate (not illustrated) are stacked. Although not illustrated inFIG.6, the buried oxide film and the holding substrate are joined to the first surface (the surface30S1) of the semiconductor substrate30. After ion implantation, annealing treatment is performed.

Next, a support substrate (not illustrated), another semiconductor base, or the like is joined to the second surface (the surface30S2) side (the multilayer wiring layer40side) of the semiconductor substrate30and flipped vertically. Subsequently, the semiconductor substrate30is separated from the buried oxide film and the holding substrate of the SOI substrate to expose the first surface (the surface30S1) of the semiconductor substrate30. It is possible to perform the steps described above with technology used in a normal CMOS process such as ion implantation and CVD (Chemical Vapor Deposition).

Next, as illustrated inFIG.7, the semiconductor substrate30is processed from the first surface (the surface30S1) side, for example, by dry etching to form, for example, the annular through hole30H. As illustrated inFIG.7, the depth of the through hole30H extends from the first surface (the surface30S1) to the second surface (the surface30S2) of the semiconductor substrate30and reaches, for example, the coupling section41A.

Subsequently, as illustrated inFIG.8, the dielectric film26is formed on the first surface (the surface30S1) of the semiconductor substrate30and the side surface of the through hole30H by using, for example, an atomic layer deposition (Atomic Layer Deposition; ALD) method. This forms the continuous dielectric film26on the first surface (the surface30S1) of the semiconductor substrate30and the side surface and the bottom surface of the through hole30H. Next, the insulating film27is formed on the first surface (the surface30S1) of the semiconductor substrate30and in the through hole30H. After that, the insulating film27and the dielectric film26formed on the bottom surface of the through hole30H are removed, for example, by dry etching to expose the coupling section41A. It is to be noted that the insulating film27on the first surface (the surface30S1) is also decreased in thickness in this case. Subsequently, an electrically conductive film is formed on the insulating film27and in the through hole30H. After that, a photoresist PR is formed at a predetermined position on the electrically conductive film. Next, the through electrode34that includes a protruding section on the first surface (the surface30S1) of the semiconductor substrate30is formed by etching and removing the photoresist PR.

Next, as illustrated inFIG.9, an insulating film included in the interlayer insulating layer28is formed on the insulating film27and the through electrode34. Subsequently, the upper first contact29A, the pad sections39A and39B, the upper second contact29B, and the upper third contact29C are formed on the through electrode34and the like and the front surface of the interlayer insulating layer28is then planarized by using a CMP (Chemical Mechanical Polishing) method. Next, an electrically conductive film21xis formed on the interlayer insulating layer28. After that, the photoresist PR is formed at a predetermined position of the electrically conductive film21x.

Subsequently, as illustrated inFIG.10, the readout electrode21A and the accumulation electrode21B are formed by etching and removing the photoresist PR.

After that, the insulating layer22is formed on the interlayer insulating layer28, the readout electrode21A, and the accumulation electrode21B and the opening22H is then provided on the readout electrode21A. Next, the semiconductor layer23, the photoelectric conversion layer24, and the upper electrode25are formed in order on the insulating layer22. Finally, the protective layer51, the light shielding film52, and the on-chip lens53are provided on the upper electrode25. As described above, the imaging element10A illustrated inFIG.1is completed.

It is to be noted that, in a case where the semiconductor layer23and another organic layer are formed by using organic materials, it is preferable that the semiconductor layer23and the other organic layer be formed continuously (in an in-situ vacuum process) in a vacuum step. In addition, the method of forming the photoelectric conversion layer24is not necessarily limited to a technique that uses a vacuum evaporation method. Another method, for example, spin coating technology, printing technology, or the like may be used. Further, a method of forming transparent electrodes (the lower electrode21and the upper electrode25) includes, depending on materials included in the transparent electrodes, a physical vapor deposition method (a PVD method) such as a vacuum evaporation method, a reactive evaporation method, a variety of sputtering methods, an electron beam evaporation method, and an ion plating method, a pyrosol method, a method of pyrolyzing an organic metal compound, a spraying method, a dip method, a variety of chemical vapor deposition methods (CVD methods) including a MOCVD method, an electroless plating method, and an electroplating method.

In a case where light enters the organic photoelectric conversion section20through the on-chip lens53in the imaging element10A, the light passes through the organic photoelectric conversion section20and the inorganic photoelectric conversion sections32B and32R in this order. While the light passes through the organic photoelectric conversion section20and the inorganic photoelectric conversion sections32B and32R, the light is photoelectrically converted for each of green light, blue light, and red light. The following describes operations of acquiring signals of the respective colors.

(Acquisition of Blue Color Signal by Organic Photoelectric Conversion Section20)

First, the green light of the pieces of light having entered the imaging element10A is selectively detected (absorbed) and photoelectrically converted by the organic photoelectric conversion section20.

The organic photoelectric conversion section20is coupled to the gate Gamp of the amplifier transistor AMP and the floating diffusion FD1through the through electrode34. The electrons of the electron-hole pairs generated in the organic photoelectric conversion section20are thus extracted from the lower electrode21side, transferred to the second surface (the surface30S2) side of the semiconductor substrate30through the through electrode34, and accumulated in the floating diffusion FD1. At the same time as this, the amplifier transistor AMP modulates the amount of electric charge generated in the organic photoelectric conversion section20to voltage.

In addition, the reset gate Grst of the reset transistor RST is disposed next to the floating diffusion FD1. This causes the reset transistor RST to reset the electric charge accumulated in the floating diffusion FD1.

Here, the organic photoelectric conversion section20is coupled to not only the amplifier transistor AMP, but also the floating diffusion FD1through the through electrode34, allowing the reset transistor RST to easily reset the electric charge accumulated in the floating diffusion FD1.

In contrast, in a case where the through electrode34and the floating diffusion FD1are not coupled, it is difficult to reset the electric charge accumulated in the floating diffusion FD1. Large voltage has to be applied to pull out the electric charge to the upper electrode25side. The photoelectric conversion layer24may be thus damaged. In addition, a structure that allows for resetting in a short period of time leads to increased dark-time noise and results in a trade-off. This structure is thus difficult.

FIG.11illustrates an operation example of the imaging element10A. (A) illustrates the potential at the accumulation electrode21B, (B) illustrates the potential at the floating diffusion FD1(the readout electrode21A), and (C) illustrates the potential at the gate (Gsel) of the reset transistor TR1rst. In the imaging element10A, voltage is individually applied to the readout electrode21A and the accumulation electrode21B.

In the imaging element10A, a drive circuit applies a potential V1to the readout electrode21A and applies a potential V2to the accumulation electrode21B in an accumulation period. Here, it is assumed that the potentials V1and V2satisfy V2>V1. This causes the electric charge (the signal charge; electrons) generated by photoelectric conversion to be drawn to the accumulation electrode21B and accumulated in the region of the semiconductor layer23opposed to the accumulation electrode21B (the accumulation period). Incidentally, the potential of the region of the semiconductor layer23opposed to the accumulation electrode21B has a value that is more negative with the passage of time of photoelectric conversion. It is to be noted that holes are sent from the upper electrode25to the drive circuit.

In the imaging element10A, a reset operation is performed in the second portion of the accumulation period. Specifically, at a timing t1, a scanning section changes the voltage of a reset signal RST from the low level to the high level. This turns on the reset transistor TR1rst in the unit pixel P. As a result, the voltage of the floating diffusion FD1is set at power supply voltage and the voltage of the floating diffusion FD1is reset (a reset period).

After the reset operation is completed, the electric charge is read out. Specifically, the drive circuit applies a potential V3to the readout electrode21A and applies a potential V4to the accumulation electrode21B at a timing t2. Here, it is assumed that the potentials V3and V4satisfy V3<V4. This causes the electric charge accumulated in the region corresponding to the accumulation electrode21B to be read out from the readout electrode21A to the floating diffusion FD1. In other words, the electric charge accumulated in the semiconductor layer23is read out to the control section (a transfer period).

After the readout operation is completed, the drive circuit applies the potential V1to the readout electrode21A and applies the potential V2to the accumulation electrode21B again. This causes the electric charge generated by photoelectric conversion to be drawn to the accumulation electrode21B and accumulated in the region of the photoelectric conversion layer24opposed to the accumulation electrode21B (the accumulation period).

(Acquisition of Blue Color Signal and Red Color Signal by Inorganic Photoelectric Conversion Sections32B and32R)

Subsequently, the blue light and the red light of the pieces of light having passed through the organic photoelectric conversion section20are respectively absorbed and photoelectrically converted in order by the inorganic photoelectric conversion section32B and the inorganic photoelectric conversion section32R. In the inorganic photoelectric conversion section32B, the electrons corresponding to the incident blue light are accumulated in an n region of the inorganic photoelectric conversion section32B and the accumulated electrons are transferred to the floating diffusion FD2by the transfer transistor Tr2. Similarly, in the inorganic photoelectric conversion section32R, the electrons corresponding to the incident red light are accumulated in an n region of the inorganic photoelectric conversion section32R and the accumulated electrons are transferred to the floating diffusion FD3by the transfer transistor Tr3.

In the imaging element10A according to the present embodiment, an organic layer (e.g., the photoelectric conversion layer24) included in the organic photoelectric conversion section20is formed by using the compound represented by the general formula (1) described above that includes hydrogen atoms at the first position (R1) and the seventh position (R4). This makes it possible to obtain an imaging element having high selectivity with respect to a desired wavelength band (e.g., a green band). The following describes this.

In recent years, image sensors have pixels miniaturized and have been requested to have higher sensitivity. For this, a photoelectric conversion element has been developed that includes an organic layer containing the compound represented by the general formula (2) which includes alkyl groups such as methyl groups at R1 and R4 as described above.

Although described in detail below, the photoelectric conversion element including an organic layer containing the compound represented by the general formula (2) described above has, however, insufficient selectivity (color selectivity) with respect to a desired wavelength band (e.g., a green band). The photoelectric conversion element is requested to have higher color selectivity.

In contrast, for example, the photoelectric conversion layer24is formed by using the compound represented by the general formula (1) including hydrogen atoms at R1 and R4 in the imaging element10A according to the present embodiment. Although described in detail in working examples described below, the compound represented by the general formula (1) has a greater difference for λ1−λ2than that of the compound represented by the general formula (2) described above. λ1represents the excitation wavelength for transition from a ground state S0to the oscillation state of a first excited state S1(S0→S1). λ2represents the excitation wavelength for transition from the ground state S0to the oscillation state of a second excited state (S0→S2). This causes the imaging element10A to have high selectivity with respect to a desired wavelength band (e.g., a green band).

As described above, it is possible in the present embodiment to provide the imaging element10A that has high color selectivity and excellent spectral characteristics and the imaging device1including this.

Next, second and third embodiments of the present disclosure are described. The following assigns the same signs to components similar to those of the first embodiment described above and omits descriptions thereof as appropriate.

2. Second Embodiment

FIG.12illustrates a cross-sectional configuration of an imaging element (an imaging element10C) according to a second embodiment of the present disclosure. The imaging element10C is included, for example, in one pixel (the unit pixel P) of an imaging device (the imaging device1) such as a CMOS image sensor used for an electronic apparatus such as a digital still camera or a video camera. The imaging element10C according to the present embodiment includes the two organic photoelectric conversion sections20and70and one inorganic photoelectric conversion section32that are stacked in the vertical direction.

The organic photoelectric conversion sections20and70and the inorganic photoelectric conversion section32each perform photoelectric conversion by selectively detecting light in a wavelength band. Specifically, for example, the organic photoelectric conversion section20acquires a color signal of green (G) as in the first embodiment described above. The organic photoelectric conversion section70acquires, for example, a color signal of blue (B). The inorganic photoelectric conversion section32acquires, for example, a color signal of red (R). This allows the imaging element10C to acquire a plurality of types of color signals in one pixel without using any color filters.

The organic photoelectric conversion section70is stacked, for example, above the organic photoelectric conversion section20. As with the organic photoelectric conversion section20, the organic photoelectric conversion section70has a configuration in which a lower electrode71, a semiconductor layer73, a photoelectric conversion layer74, and an upper electrode75are stacked in this order from the first surface (the surface30S1) side of the semiconductor substrate30. In addition, there is provided an insulating layer72between the lower electrode71and the semiconductor layer73. The lower electrodes71are separately formed, for example, for the respective imaging elements10C. Although described in detail below, each of the lower electrodes71includes a readout electrode71A and an accumulation electrode71B that are separated from each other with the insulating layer72interposed in between. The readout electrode71A of the lower electrode71is electrically coupled to the photoelectric conversion layer74through an opening72H provided in the insulating layer72.FIG.12illustrates an example in which the semiconductor layers73, the photoelectric conversion layers74, and the upper electrodes75are separately formed for the respective imaging elements10C. For example, the semiconductor layers73, the photoelectric conversion layers74, and the upper electrodes75may be, however, formed as continuous layers common to the plurality of imaging elements10C.

The photoelectric conversion layer74converts light energy to electric energy. As with the photoelectric conversion layer24, the photoelectric conversion layer74includes two or more types of organic materials that each function as a p-type semiconductor or an n-type semiconductor. The photoelectric conversion layer74further includes an organic material or a so-called dye material in addition to a p-type semiconductor and an n-type semiconductor. The organic material or the dye material photoelectrically converts light in a predetermined wavelength band and transmits light in another wavelength band. In a case where the photoelectric conversion layer74is formed by using three types of organic materials including a p-type semiconductor, an n-type semiconductor, and a dye material, the p-type semiconductor and the n-type semiconductor are preferably materials having light transmissivity in a visible region (e.g., 400 nm to 700 nm). The photoelectric conversion layer74has, for example, a thickness of 25 nm or more and 400 nm or less. Preferably, the photoelectric conversion layer74has a thickness of 50 nm or more and 350 nm or less. More preferably, the photoelectric conversion layer74has a thickness of 150 nm or more and 300 nm or less. Examples of the dye material used for the photoelectric conversion layer74include coumarin and a diazo compound, derivatives thereof, or the like.

There are provided two through electrodes34X and34Y between the first surface (the surface30S1) and the second surface (the surface30S2) of the semiconductor substrate30.

As in the first embodiment described above, the through electrode34X is electrically coupled to the readout electrode21A of the organic photoelectric conversion section20and the organic photoelectric conversion section20is coupled to the gate Gamp of the amplifier transistor AMP and one source/drain region36B1of the reset transistor RST (the reset transistor Tr1rst) through the through electrode34X. The one source/drain region36B1of the reset transistor RST (the reset transistor Tr1rst) also serves as the floating diffusion FD1. The upper end of the through electrode34X is coupled to the readout electrode21A, for example, through the upper first contact29A, the pad section39A, and the upper second contact29B.

The through electrode34Y is electrically coupled to the readout electrode71A of the organic photoelectric conversion section70and the organic photoelectric conversion section70is coupled to the gate Gamp of the amplifier transistor AMP and one source/drain region36B2of the reset transistor RST (the reset transistor Tr2rst) through the through electrode34Y. The one source/drain region36B2of the reset transistor RST (the reset transistor Tr2rst) also serves as the floating diffusion FD2. The upper end of the through electrode34Y is coupled to the readout electrode71A, for example, through an upper fourth contact79A, a pad section69A, an upper fifth contact79B, a pad section69B, and an upper sixth contact79C. In addition, a pad69C is coupled to the accumulation electrode71B of the lower electrode71through an upper seventh contact79D. The lower electrode71is included in the organic photoelectric conversion section70.

As described above, the imaging element10C according to the present embodiment has a configuration in which the two organic photoelectric conversion sections20and70and the one inorganic photoelectric conversion section32are stacked. As in the first embodiment described above, for example, the photoelectric conversion layer24included in the organic photoelectric conversion section20that acquires a color signal of green (G) is formed by using the compound represented by the general formula (1) described above. This makes it possible to obtain effects similar to those of the first embodiment described above.

FIG.13illustrates a cross-sectional configuration of an imaging element (an imaging element10D) according to a third embodiment of the present disclosure. The imaging element10D is included, for example, in one pixel (the unit pixel P) of the imaging device1such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor used for an electronic apparatus such as a digital still camera or a video camera. The imaging element10D according to the present embodiment has a configuration in which a red photoelectric conversion section90R, a green photoelectric conversion section90G, and a blue photoelectric conversion section90B are stacked above a semiconductor substrate80in this order with an insulating layer96interposed in between. The red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B are each formed by using an organic material.

The red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B respectively include organic photoelectric conversion layers92R,92G, and92B between pairs of electrodes. Specifically, the red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B respectively include the organic photoelectric conversion layers92R,92G, and92B between a first electrode91R and a second electrode93R, between a first electrode91G and a second electrode93G, and between a first electrode91B and a second electrode93B.

There is provided an on-chip lens98L above the blue photoelectric conversion section90B with a protective layer97and an on-chip lens layer98interposed in between. There are provided a red electricity storage layer810R, a green electricity storage layer810G, and a blue electricity storage layer810B in the semiconductor substrate80. Light having entered the on-chip lens98L is photoelectrically converted by the red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B and signal charge is transmitted from the red photoelectric conversion section90R to the red electricity storage layer810R, from the green photoelectric conversion section90G to the green electricity storage layer810G, and from the blue photoelectric conversion section90B to the blue electricity storage layer810B. Although the signal charge may be either electrons or holes generated by photoelectric conversion, the following gives description by exemplifying a case where electrons are read out as signal charge.

The semiconductor substrate80includes, for example, a p-type silicon substrate. The red electricity storage layer810R, the green electricity storage layer810G, and the blue electricity storage layer810B provided in this semiconductor substrate80each include an n-type semiconductor region. The signal charge (the electrons) supplied from the red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B are accumulated in these n-type semiconductor regions. The n-type semiconductor regions of the red electricity storage layer810R, the green electricity storage layer810G, and the blue electricity storage layer810B are formed, for example, by doping the semiconductor substrate80with n-type impurities such as phosphorus (P) or arsenic (As). It is to be noted that the semiconductor substrate80may be provided on a support substrate (not illustrated) including glass or the like.

The semiconductor substrate80is provided with pixel transistors. The respective pixel transistors are for reading out electrons from the red electricity storage layer810R, the green electricity storage layer810G, and the blue electricity storage layer810B and transferring the electrons, for example, to vertical signal lines (e.g., vertical signal lines Lsig inFIG.14described below). Floating diffusions of these pixel transistors are provided in the semiconductor substrate80. These floating diffusions are coupled to the red electricity storage layer810R, the green electricity storage layer810G, and the blue electricity storage layer810B. Each of the floating diffusions includes an n-type semiconductor region.

The insulating layer96includes, for example, a single layer film including one of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), hafnium oxide (HfOx), and the like or a stacked film including two or more of them. In addition, the insulating layer96may be formed by using an organic insulating material. Although not illustrated, the insulating layer96is provided with plugs and electrodes. The respective plugs are for coupling the red electricity storage layer810R and the red photoelectric conversion section90R, the green electricity storage layer810G and the green photoelectric conversion section90G, and the blue electricity storage layer810B and the blue photoelectric conversion section90B.

The red photoelectric conversion section90R includes the first electrode91R, the organic photoelectric conversion layer92R, and the second electrode93R in this order from positions closer to the semiconductor substrate80. The green photoelectric conversion section90G includes the first electrode91G, the organic photoelectric conversion layer92G, and the second electrode93G in this order from positions closer to the red photoelectric conversion section90R. The blue photoelectric conversion section90B includes the first electrode91B, the organic photoelectric conversion layer92B, and the second electrode93B in this order from positions closer to the green photoelectric conversion section90G. There is further provided an insulating layer94between the red photoelectric conversion section90R and the green photoelectric conversion section90G and there is further provided an insulating layer95between the green photoelectric conversion section90G and the blue photoelectric conversion section90B. The red photoelectric conversion section90R, the green photoelectric conversion section90G, and the blue photoelectric conversion section90B respectively absorb selectively red (e.g., a wavelength of 600 nm or more and less than 700 nm) light, green (e.g., a wavelength of 500 nm or more and less than 600 nm) light, and blue (e.g., a wavelength of 400 or more and less than 500 nm) light to generate electron-hole pairs.

The first electrode91R, the first electrode91G, and the first electrode91B respectively extract the signal charge generated in the organic photoelectric conversion layer92R, the signal charge generated in the organic photoelectric conversion layer92G, and the signal charge generated in the organic photoelectric conversion layer92B. The first electrodes91R,91G, and91B are provided, for example, for each pf the pixels.

Each of the first electrodes91R,91G, and91B includes, for example, an electrically conductive material having light transmissivity. Specifically, each of the first electrodes91R,91G, and91B includes ITO. Each of the first electrodes91R,91G, and91B may include, for example, a tin oxide-based material or a zinc oxide-based material. The tin oxide-based material is obtained by doping tin oxide with a dopant. Examples of the zinc oxide-based material include an aluminum zinc oxide in which aluminum is added to zinc oxide as a dopant, a gallium zinc oxide in which gallium is added to zinc oxide as a dopant, an indium zinc oxide in which indium is added to zinc oxide as a dopant, and the like. In addition, it is also possible to use IGZO, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, ZnSnO3, and the like. Each of the first electrodes91R,91G, and91B has, for example, a thickness of 50 nm to 500 nm.

For example, there may be provided electron transport layers between the first electrode91R and the organic photoelectric conversion layer92R, between the first electrode91G and the organic photoelectric conversion layer92G, and between the first electrode91B and the organic photoelectric conversion layer92B. The electron transport layers are for facilitating the electrons generated in the organic photoelectric conversion layers92R,92G, and92B to be supplied to the first electrodes91R,91G, and91B. Each of the electron transport layers includes, for example, titanium oxide, zinc oxide, or the like. Each of the electron transport layers may include a titanium oxide film and a zinc oxide film that are stacked. Each of the electron transport layers has, for example, a thickness of 0.1 nm to 1000 nm. It is preferable that each of the electron transport layers have a thickness of 0.5 nm to 300 nm.

Each of the organic photoelectric conversion layers92R,92G, and92B absorbs light in a selective wavelength band for photoelectric conversion and transmits light in another wavelength band. Here, the light in the selective wavelength band is, for example, light in a wavelength band having a wavelength of 600 nm or more and less than 700 nm for the organic photoelectric conversion layer92R. The light in the selective wavelength band is, for example, light in a wavelength band having a wavelength of 500 nm or more and less than 600 nm for the organic photoelectric conversion layer92G. The light in the selective wavelength band is, for example, light in a wavelength band having a wavelength of 400 nm or more and less than 500 nm for the organic photoelectric conversion layer92B. Each of the organic photoelectric conversion layers92R,92G, and92B has, for example, a thickness of 25 nm or more and 400 nm or less. Preferably, each of the organic photoelectric conversion layers92R,92G, and92B has a thickness of 50 nm or more and 350 nm or less. More preferably, each of the organic photoelectric conversion layers92R,92G, and92B has a thickness of 150 nm or more and 300 nm or less.

Each of the organic photoelectric conversion layers92R,92G, and92B converts light energy to electric energy. As with the photoelectric conversion layer24, each of the organic photoelectric conversion layers92R,92G, and92B includes two or more types of organic materials that each function as a p-type semiconductor or an n-type semiconductor. Each of the organic photoelectric conversion layers92R,92G, and92B further includes an organic material or a so-called dye material in addition to a p-type semiconductor and an n-type semiconductor. The organic material or the dye material photoelectrically converts light in the predetermined wavelength band described above and transmits light in another wavelength band. Examples of such a material include rhodamine, merocyanine, and derivatives thereof for the organic photoelectric conversion layer92R. For the organic photoelectric conversion layer92G, the compound (the BODIPY dye) represented by the general formula (1) described above is mentioned. For the organic photoelectric conversion layer92B, for example, coumarin, a diazo compound, and a cyanine dye, derivatives thereof, or the like are mentioned.

Examples of another organic material included in each of the organic photoelectric conversion layers92R,92G, and92B include fullerene or a fullerene derivative. Each of the organic photoelectric conversion layers92R,92G, and92B may further include an organic material other than the organic materials described above.

There may be provided other layers between the organic photoelectric conversion layer92R and the second electrode93R, between the organic photoelectric conversion layer92G and the second electrode93G, and between the organic photoelectric conversion layer92B and the second electrode93B as in the first embodiment described above.

The second electrode93R, the second electrode93G, and the second electrode93B are for respectively extracting the holes generated in the organic photoelectric conversion layer92R, the holes generated in the organic photoelectric conversion layer92G, and the holes generated in the organic photoelectric conversion layer92G. The holes extracted from the respective second electrodes93R,93G, and93B are discharged, for example, to p-type semiconductor regions (not illustrated) in the semiconductor substrate80through the respective transmission paths (not illustrated).

Each of the second electrodes93R,93G, and93B includes, for example, an electrically conductive material such as gold (Au), silver (Ag), copper (Cu), and aluminum (Al). As with the first electrodes91R,91G, and91B, each of the second electrodes93R,93G, and93B may include a transparent electrically conductive material. In the imaging element10D, the holes extracted from these second electrodes93R,93G, and93B are discharged. For example, in a case where the plurality of imaging elements10D is disposed in the imaging device1described below, the second electrodes93R,93G, and93B may be thus provided to be common to the respective imaging elements10D (the unit pixels P). Each of the second electrodes93R,93G, and93B has, for example, a thickness of 0.5 nm or more to 100 nm or less.

The insulating layer94is for insulating the second electrode93R and the first electrode91G. The insulating layer95is for insulating the second electrode93G and the first electrode91B. Each of the insulating layers94and95includes, for example, a metal oxide, a metal sulfide, or an organic substance. Examples of the metal oxide include silicon oxide (SiOx), aluminum oxide (AlOx), zirconium oxide (ZrOx), titanium oxide (TiOx), zinc oxide (ZnOx), tungsten oxide (WOx), magnesium oxide (MgOx), niobium oxide (NbOx), tin oxide (SnOx), gallium oxide (GaOx), and the like. Examples of the metal sulfide include zinc sulfide (ZnS), magnesium sulfide (MgS), and the like. It is preferable that the band gap of a material included in each of the insulating layers94and95be 3.0 eV or more. Each of the insulating layers94and95has, for example, a thickness of 2 nm or more and 100 nm or less.

As described above, it is possible to obtain effects similar to those of the first embodiment described above by forming, for example, the organic photoelectric conversion layer92G by using the compound represented by the general formula (1) described above.

4. Application Examples

Application Example 1

FIG.14illustrates an overall configuration of an imaging device (the imaging device1) in which the imaging element10A (or any of the imaging elements10B to10D) described in the first to third embodiments described above is used for each of the pixels. This imaging device1is a CMOS image sensor. The imaging device1includes the pixel section1aas an imaging area and a peripheral circuit portion130in a peripheral region of this pixel section1aon the semiconductor substrate30. The peripheral circuit portion130includes, for example, a row scanning section131, a horizontal selection section133, a column scanning section134, and a system control section132.

The pixel section1aincludes, for example, the plurality of unit pixels P (each corresponding to the imaging element10) that is two-dimensionally disposed in a matrix. These unit pixels P are provided with pixel drive lines Lread (specifically, row selection lines and reset control lines). Each of the pixel rows is provided, for example, with the pixel drive line Lread. Each of the pixel columns is provided with the vertical signal line Lsig. The pixel drive lines Lread are for transmitting drive signals for reading out signals from pixels. One end of each of the pixel drive lines Lread is coupled to the output end of the row scanning section131corresponding to each row.

The row scanning section131is a pixel drive section that includes a shift register, an address decoder, and the like and drives each of the unit pixels P of the pixel section1a, for example, row by row. Signals outputted from the respective unit pixels P in the pixel rows selectively scanned by the row scanning section131are supplied to the horizontal selection section133through the respective vertical signal lines Lsig. The horizontal selection section133includes an amplifier, a horizontal selection switch, and the like provided for each of the vertical signal lines Lsig.

The column scanning section134includes a shift register, an address decoder, and the like and drives the respective horizontal selection switches of the horizontal selection section133in order while scanning the horizontal selection switches. The selective scanning by this column scanning section134causes signals of the respective pixels transmitted through each of the vertical signal lines Lsig to be outputted to a horizontal signal line135in order and causes the signals to be transmitted to the outside of the semiconductor substrate30through the horizontal signal line135.

The circuit portion including the row scanning section131, the horizontal selection section133, the column scanning section134, and the horizontal signal line135may be formed directly on the semiconductor substrate30or may be provided on external control IC. In addition, the circuit portion thereof may be formed on another substrate coupled by a cable or the like.

The system control section132receives a clock supplied from the outside of the semiconductor substrate30, data for an instruction about an operation mode, and the like and outputs data such as internal information of the imaging device1. The system control section132further includes a timing generator that generates a variety of timing signals and controls the driving of the peripheral circuit such as the row scanning section131, the horizontal selection section133, and the column scanning section134on the basis of the variety of timing signals generated by the timing generator.

Application Example 2

The imaging device1described above is applicable, for example, to any type of electronic apparatus with an imaging function including a camera system such as a digital still camera and a video camera, a mobile phone having an imaging function, and the like.FIG.15illustrates a schematic configuration of an electronic apparatus2(a camera) as an example thereof. This electronic apparatus2is, for example, a video camera that is able to shoot a still image or a moving image. The electronic apparatus2includes the imaging device1, an optical system (an optical lens)210, a shutter device211, a drive section213that drives the imaging device1and the shutter device211, and a signal processing section212.

The optical system210guides image light (incident light) from a subject to the pixel section1aof the imaging device1. This optical system210may include a plurality of optical lenses. The shutter device211controls a period of time in which the imaging device1is irradiated with light and a period of time in which light is blocked. The drive section213controls a transfer operation of the imaging device1and a shutter operation of the shutter device211. The signal processing section212performs various kinds of signal processing on signals outputted from the imaging device1. An image signal Dout subjected to the signal processing is stored in a storage medium such as a memory or outputted to a monitor or the like.

5. Practical Application Examples

Further, the imaging device1described above is also applicable to the following electronic apparatuses (a capsule type endoscope10100and a mobile body such as a vehicle).

(Example of Practical Application to In-Vivo Information Acquisition System)

Further, the technology (the present technology) according to the present disclosure is applicable to a variety of products. For example, the technology according to the present disclosure may be applied to an endoscopic surgery system.

FIG.16is a block diagram depicting an example of a schematic configuration of an in-vivo information acquisition system of a patient using a capsule type endoscope, to which the technology according to an embodiment of the present disclosure (present technology) can be applied.

The in-vivo information acquisition system10001includes a capsule type endoscope10100and an external controlling apparatus10200.

The capsule type endoscope10100is swallowed by a patient at the time of inspection. The capsule type endoscope10100has an image pickup function and a wireless communication function and successively picks up an image of the inside of an organ such as the stomach or an intestine (hereinafter referred to as in-vivo image) at predetermined intervals while it moves inside of the organ by peristaltic motion for a period of time until it is naturally discharged from the patient. Then, the capsule type endoscope10100successively transmits information of the in-vivo image to the external controlling apparatus10200outside the body by wireless transmission.

The external controlling apparatus10200integrally controls operation of the in-vivo information acquisition system10001. Further, the external controlling apparatus10200receives information of an in-vivo image transmitted thereto from the capsule type endoscope10100and generates image data for displaying the in-vivo image on a display apparatus (not depicted) on the basis of the received information of the in-vivo image.

In the in-vivo information acquisition system10001, an in-vivo image imaged a state of the inside of the body of a patient can be acquired at any time in this manner for a period of time until the capsule type endoscope10100is discharged after it is swallowed.

A configuration and functions of the capsule type endoscope10100and the external controlling apparatus10200are described in more detail below.

The capsule type endoscope10100includes a housing10101of the capsule type, in which a light source unit10111, an image pickup unit10112, an image processing unit10113, a wireless communication unit10114, a power feeding unit10115, a power supply unit10116and a control unit10117are accommodated.

The light source unit10111includes a light source such as, for example, a light emitting diode (LED) and irradiates light on an image pickup field-of-view of the image pickup unit10112.

The image pickup unit10112includes an image pickup element and an optical system including a plurality of lenses provided at a preceding stage to the image pickup element. Reflected light (hereinafter referred to as observation light) of light irradiated on a body tissue which is an observation target is condensed by the optical system and introduced into the image pickup element. In the image pickup unit10112, the incident observation light is photoelectrically converted by the image pickup element, by which an image signal corresponding to the observation light is generated. The image signal generated by the image pickup unit10112is provided to the image processing unit10113.

The image processing unit10113includes a processor such as a central processing unit (CPU) or a graphics processing unit (GPU) and performs various signal processes for an image signal generated by the image pickup unit10112. The image processing unit10113provides the image signal for which the signal processes have been performed thereby as RAW data to the wireless communication unit10114.

The wireless communication unit10114performs a predetermined process such as a modulation process for the image signal for which the signal processes have been performed by the image processing unit10113and transmits the resulting image signal to the external controlling apparatus10200through an antenna10114A. Further, the wireless communication unit10114receives a control signal relating to driving control of the capsule type endoscope10100from the external controlling apparatus10200through the antenna10114A. The wireless communication unit10114provides the control signal received from the external controlling apparatus10200to the control unit10117.

The power feeding unit10115includes an antenna coil for power reception, a power regeneration circuit for regenerating electric power from current generated in the antenna coil, a voltage booster circuit and so forth. The power feeding unit10115generates electric power using the principle of non-contact charging.

The power supply unit10116includes a secondary battery and stores electric power generated by the power feeding unit10115. InFIG.16, in order to avoid complicated illustration, an arrow mark indicative of a supply destination of electric power from the power supply unit10116and so forth are omitted. However, electric power stored in the power supply unit10116is supplied to and can be used to drive the light source unit10111, the image pickup unit10112, the image processing unit10113, the wireless communication unit10114and the control unit10117.

The control unit10117includes a processor such as a CPU and suitably controls driving of the light source unit10111, the image pickup unit10112, the image processing unit10113, the wireless communication unit10114and the power feeding unit10115in accordance with a control signal transmitted thereto from the external controlling apparatus10200.

The external controlling apparatus10200includes a processor such as a CPU or a GPU, a microcomputer, a control board or the like in which a processor and a storage element such as a memory are mixedly incorporated. The external controlling apparatus10200transmits a control signal to the control unit10117of the capsule type endoscope10100through an antenna10200A to control operation of the capsule type endoscope10100. In the capsule type endoscope10100, an irradiation condition of light upon an observation target of the light source unit10111can be changed, for example, in accordance with a control signal from the external controlling apparatus10200. Further, an image pickup condition (for example, a frame rate, an exposure value or the like of the image pickup unit10112) can be changed in accordance with a control signal from the external controlling apparatus10200. Further, the substance of processing by the image processing unit10113or a condition for transmitting an image signal from the wireless communication unit10114(for example, a transmission interval, a transmission image number or the like) may be changed in accordance with a control signal from the external controlling apparatus10200.

Further, the external controlling apparatus10200performs various image processes for an image signal transmitted thereto from the capsule type endoscope10100to generate image data for displaying a picked up in-vivo image on the display apparatus. As the image processes, various signal processes can be performed such as, for example, a development process (demosaic process), an image quality improving process (bandwidth enhancement process, a super-resolution process, a noise reduction (NR) process and/or image stabilization process) and/or an enlargement process (electronic zooming process). The external controlling apparatus10200controls driving of the display apparatus to cause the display apparatus to display a picked up in-vivo image on the basis of generated image data. Alternatively, the external controlling apparatus10200may also control a recording apparatus (not depicted) to record generated image data or control a printing apparatus (not depicted) to output generated image data by printing.

The example of the in-vivo information acquisition system to which the technology according to the present disclosure may be applied has been described above. The technology according to the present disclosure may be applied, for example, to the image pickup unit10112among the components described above. This increases the detection accuracy.

(Example of Practical Application to Endoscopic Surgery System)

The technology (the present technology) according to the present disclosure is applicable to a variety of products. For example, the technology according to the present disclosure may be applied to an endoscopic surgery system.

FIG.18is a block diagram depicting an example of a functional configuration of the camera head11102and the CCU11201depicted inFIG.17.

The example of the endoscopic surgery system to which the technology according to the present disclosure may be applied has been described above. The technology according to the present disclosure may be applied to the image pickup unit11402among the components described above. The application of the technology according to the present disclosure to the image pickup unit11402increases the detection accuracy.

It is to be noted that the endoscopic surgery system has been described here as an example, but the technology according to the present disclosure may be additionally applied, for example, to a microscopic surgery system or the like.

(Example of Practical Application to Mobile Body)

The technology according to the present disclosure is applicable to a variety of products. For example, the technology according to the present disclosure may be achieved as a device mounted on any type of mobile body such as a vehicle, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a vessel, a robot, a construction machine, or an agricultural machine (a tractor).

FIG.20is a diagram depicting an example of the installation position of the imaging section12031.

6. Working Examples

Next, working examples of the present disclosure are described in detail. In an experiment 1, a quantum chemical calculation of a BODIPY dye was made. In an experiment 2, the spectral characteristics of a BODIPY dye were evaluated. In an experiment 3, a photoelectric conversion element containing a BODIPY dye was fabricated and the electric characteristics thereof were evaluated.

As the compound (the BODIPY dye) represented by the general formula (1) described above, quantum chemical calculations of the compounds represented by a formula (1-2) to a formula (1-5) were made. In addition, as a comparative example, quantum chemical calculations of the compounds represented by the following formula (2-1) to the formula (2-3) were made. First, the structure optimization for the ground state S0was performed by using a quantum chemical calculation program (Gaussian). Subsequently, the resultant structure in the ground state S0was used to make a TD-DFT (Time-Dependent Density Function Theory) calculation. The structure optimization calculation for the ground state S0was made by using B3LYP/6-31G** and the TD-DFT was made by using M062X/6-31+G**. The transition state was defined as X. The excitation wavelength λ1and oscillator strength f1for transition from the ground state S0to the oscillation state of the first excited state S1(S0→S1) and the excitation wavelength λ2and oscillator strength f2thereof for transition of the ground state S0to the oscillation state of the second excited state S2(S0→S2) were obtained. The second excited state S2was set as an excited state in which the oscillator strength f2was 0.01 or more and the excitation wavelength λ2was the closest to an excitation wavelength r1.

Table 1 tabulates the excitation wavelength λ1and the oscillator strength f1of each of the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) for S0→S1, the excitation wavelength λ2and the oscillator strength f2thereof for S0→S2, and the difference (λ1−λ2) between the excitation wavelength λ1and the excitation wavelength λ2.FIG.21is a characteristic diagram illustrating the absorption spectrum of the compound represented by the formula (1-5) that is obtained from a quantum scientific calculation.FIG.22is a characteristic diagram illustrating the absorption spectrum of the compound represented by the formula (2-1) that is obtained from a quantum scientific calculation.FIG.23is a characteristic diagram illustrating the absorption spectrum of the compound represented by the formula (2-2) that is obtained from a quantum scientific calculation.FIG.24is a characteristic diagram illustrating the absorption spectrum of the compound represented by the formula (1-2) that is obtained from a quantum scientific calculation.FIG.25is a characteristic diagram illustrating the absorption spectrum of the compound represented by a formula (1-3) that is obtained from a quantum scientific calculation.FIG.26is a characteristic diagram illustrating the absorption spectrum of the compound represented by a formula (1-4) that is obtained from a quantum scientific calculation.FIG.27is a characteristic diagram illustrating the absorption spectrum of the compound represented by the formula (2-3) that is obtained from a quantum scientific calculation. The vertical axis indicates oscillator strength (Oscillator Strength) and the horizontal axis indicates wavelength (nm).

Table 1 indicates that the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) each exhibits a great oscillator strength f1of 0.45 to 0.59 in transition from the ground state S0to the first excited state S1(S0→S1). The absorption band of the excitation wavelength λ1determines the wavelength of which of blue, green, and red bands is absorbed by the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3).

It is to be noted that the excitation wavelength λ1of each of the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) ranges from 430 to 462 nm. This corresponds to the wavelength of blue and it seems thus that each of the compounds is a dye that absorbs blue light. However, in a case where a result of the experiment 2 described below is taken into consideration, it seems reasonable that each of the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) is a dye that absorbs green light.

For example, the excitation wavelength λ1of the compound represented by the formula (1-5) is 444 nm, but the maximum absorption wavelength of a thin film of the compound represented by the formula (1-5) that was obtained from the experiment 2 was 548 nm. As can be seen from this result, the excitation wavelength λ1obtained from a quantum chemical calculation and the value of the maximum absorption wavelength of a thin film that was actually fabricated seem to have an offset of about 100 nm. In a case where this offset of about 100 nm is taken into consideration, the maximum absorption wavelength of a thin film of each of the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) ranges from 534 to 566 nm. Each of these compounds therefore seems to be a dye that absorbs green light in fact.

Table 1 andFIG.21indicate that the excitation wavelength λ1for transition from the ground state S0to the oscillation state of the first excited state S1(S0→S1) is the main absorption band of each of the compounds represented by the formula (1-2) to the formula (1-5) and the formula (2-1) to the formula (2-3) and this absorption band is an absorption band that absorbs green light on a thin film which was actually fabricated as described above. The excitation wavelength λ2for transition from the ground state S0to the oscillation state of the second excited state S2(S0→S2) was observed in the compounds represented by the formula (2-1) to the formula (2-3) on a short wavelength side of 92 to 106 nm as compared with transition from the ground state S0to the first excited state S1(S0→S1). This indicates that the excitation wavelength λ2for transition from the ground state S0to the oscillation state of the second excited state S2(S0→S2) seems to have absorption in a blue wavelength band. It thus seems that the excitation wavelength λ2for transition from the ground state S0to the oscillation state of the second excited state S2(S0→S2) causes color selectivity to decrease.

In contrast, the excitation wavelength λ2for transition from the ground state S0to the oscillation state of the second excited state S2(S0→S2) was observed in the compounds represented by the formula (1-2) to the formula (1-5) each including hydrogen atoms at the first position and the seventh position on a short wavelength side of 113 to 127 nm as compared with the excitation wavelength λ1for transition from the ground state S0to the oscillation state of the first excited state S1(S0→S1). In this way, a compound whose excitation wavelength λ2for transition from the ground state S0to the oscillation state of the second excited state S2(S0→S2) is considerably shorter than the excitation wavelength λ1for transition from the ground state S0to the oscillation state of the first excited state S1(S0→S1) allows the absorption wavelength from the ground state S0to the second excited state S2(S0→S2) to be closer to a short wavelength side than that of a blue band even in a case where the maximum absorption wavelength of a thin film is carried by a green wavelength band. In other words, as in the compounds represented by the formula (1-2) to the formula (1-5), the compound represented by the general formula (1) including hydrogen atoms at the first position and the seventh position clearly has a greater difference (λ1−λ2) between the excitation wavelength λ1and the excitation wavelength λ2and makes it possible to decrease the absorption of a blue band. A comparison betweenFIGS.21to27indicates that the compounds represented by the formula (1-2) to the formula (1-5) have less absorption of a blue region than the compounds represented by the formula (2-1) to the formula (2-3).

The spectral characteristics of the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) were evaluated by using the following method. First, the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) were each evaporated on a glass substrate by using an organic evaporation machine in a resistive heating method under a vacuum condition of 1×10−5Pa or less while rotating a substrate holder. The glass substrate was cleaned by UV/ozone treatment. Evaporation was performed with an evaporation speed of 0.1 nm/second to offer a film thickness of 50 nm. This was used as a sample for the spectral characteristics of a single film of a BODIPY dye.

The spectral characteristics were obtained from the absorptivity (%) of light absorbed each single film by measuring the transmittance and the reflectance of a wavelength band of 350 to 700 nm for each of the wavelengths with an ultraviolet and visible spectrophotometer. A linear absorption coefficient (cm−1) for the wavelength of each single film was evaluated on the basis of the Lambert-Beer law by using this absorptivity of light and the film thickness of the single film as parameters.

FIG.28illustrates the absorption spectra of the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2). Table 2 tabulates the maximum absorption wavelengths (nm), the maximum linear absorption coefficients (cm−1), and the linear absorption coefficients (cm−1) of the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) on wavelengths of 400 nm, 420 nm, 440 nm, 450 nm, 460 nm, 600 nm, and 650 nm and the ratios between the linear absorption coefficients and the maximum linear absorption coefficients on these wavelengths.

FIG.28and Table 2 indicate that the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) are materials that have high maximum linear absorption coefficients of 1×104cm-1 or more and are suitable to efficiently absorb visible light. In particular, it is clear that the compounds represented by the formula (1-5) and the formula (2-2) are materials that have high maximum linear absorption coefficients of 2×104cm-1 or more and are suitable to considerably efficiently absorb visible light. Further, it was found that the compound represented by the formula (1-5) had low linear absorption coefficients on wavelengths of 350 to 460 nm and 600 to 650 nm and was able to selectively absorb the wavelength of a predetermined band.

In addition, the compound represented by the formula (1-5) had a maximum absorption wavelength of 548 nm, the compound represented by the formula (2-1) had a maximum absorption wavelength of 584 nm, and the compound represented by the formula (2-2) had a maximum absorption wavelength of 564 nm. This indicates that these compounds absorb green light.

Further, any of the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) had a linear absorption coefficient that is a half or less of the maximum linear absorption coefficients on wavelengths of 400 nm, 420 nm, 440 nm, 450 nm, and 460 nm each of which is a visible light wavelength on a short wavelength side as compared with a green wavelength band. Among them, the linear absorption coefficient of the compound represented by the formula (1-5) was ten percent or less. In addition, any of the compounds represented by the formula (1-5), the formula (2-1), and the formula (2-2) had a linear absorption coefficient that is a half or less of the maximum linear absorption coefficients on wavelengths of 600 nm and 650 nm each of which is a visible light wavelength on a long wavelength side as compared with a green wavelength band. Among them, the linear absorption coefficient of the compound represented by the formula (1-5) was one percent or less. This indicates that the compound represented by the formula (1-5) selectively absorbs the wavelength of a predetermined band more than the compounds represented by the formula (2-1) and the formula (2-2).

It is possible to explain from a result obtained from the experiment 1 why the linear absorption coefficient of the compound represented by the formula (1-5) for a blue band is lower than those of the compounds represented by the formula (2-1) and the formula (2-2). In other words, this seems to be because the compound represented by the general formula (1) including hydrogen atoms at the first position and the seventh position has a great difference (S1-S2) between the first excited state S1and the second excited state S2and has less absorption of a blue band.

The linear absorption coefficient of the compound represented by the formula (1-5) for a red band is lower than those of the compounds represented by the formula (2-1) and the formula (2-2) apparently because of lower cohesiveness.

Experimental Example 1

First, a glass substrate provided with an ITO electrode (a lower electrode) having a film thickness of 50 nm was cleaned by UV/ozone treatment. Subsequently, the glass substrate was moved to a vacuum evaporation machine. An organic layer was formed on the glass substrate by using a resistive heating method in a reduced pressure condition of 1×10−5Pa or less while a substrate holder is rotated. First, a film of the compound represented by the following formula (4) was formed at an evaporation speed of 1 Å/sec to have a thickness of 5 nm. Subsequently, a C60fullerene (formula (5)), the compound represented by the formula (1-5), and BP-rBDT (formula (6)) were co-evaporated to form a photoelectric conversion layer. These were evaporated at speeds of 0.025 nm/second (formula (5)), 0.050 nm/second (formula (1-5)), and 0.050 nm/second (formula (6)) to form a layer having a total thickness of 230 nm. This offered a photoelectric conversion layer having a composition ratio of 20 vol % (formula (5)):40 vol % (formula (1-5)):40 vol % (formula (6)). Next, a layer of the compound represented by the following formula (7) was formed as a hole blocking layer at an evaporation speed of 0.3 Å/sec to have a thickness of 5 nm. Subsequently, an AlSiCu film was formed on the hole blocking layer in an evaporation method to have a film thickness of 100 nm and this was used as an upper electrode. As described above, a photoelectric conversion element was fabricated including a photoelectric conversion region of 1 mm×1 mm.

Experimental Example 2

Except for the use of the compound represented by the formula (2-1) described above in place of the compound represented by the formula (1-5) used in the experimental example 1, a method similar to that of the experimental example 1 was used to fabricate a photoelectric conversion element (experimental example 2).

Experimental Example 3

Except for the use of the compound represented by the formula (2-2) described above in place of the compound represented by the formula (1-5) used in the experimental example 1, a method similar to that of the experimental example 1 was used to fabricate a photoelectric conversion element (experimental example 3).

The external quantum efficiency (EQE) and the dark current characteristics of each of the photoelectric conversion elements fabricated in the experimental examples 1 to 3 were evaluated by using the following method.

The EQE and the dark current characteristics were evaluated by using a semiconductor parameter analyzer. Specifically, a current value (a bright current value) obtained in a case where the photoelectric conversion element was irradiated with a light amount of 1.62 μW/cm2from a light source through a filter and a bias voltage of −2.6 V was applied between electrodes and a current value (a dark current value) obtained in a case where the photoelectric conversion element was irradiated with a light amount of 0 μW/cm2were each measured. The EQE and the dark current characteristics were calculated from these values. As the wavelength of the light with which the element was irradiated, the wavelength corresponding to the maximum absorption wavelength of each organic photoelectric conversion layer in the visible range was selected. As the irradiation wavelength of light, 530 nm, 560 nm, and 560 nm were selected in the order of the experimental example 1, the experimental example 2, and the experimental example 3.

Table 3 tabulates the configurations, the EQE, and the dark current characteristics of the photoelectric conversion layers in the experimental example 1 to the experimental example 3. It is to be noted that the EQE described in Table 3 is a relative value in a case where the experimental example 2 is used as a reference (1.0).

Table 3 indicates that the experimental example 1 in which the compound represented by the formula (1-5) was used has higher EQE and more excellent dark current characteristics than those of the experimental example 2 and the experimental example 3. This indicates that the use of the compound represented by the general formula (1) including hydrogen atoms at the first position and the seventh position makes it possible to obtain favorable EQE and dark current characteristics. In addition, a result of the experiment 2 obviously indicates that the photoelectric conversion layer used in the experimental example 1 is able to selectively absorb the wavelength of a predetermined band. As described above, it was found that a photoelectric conversion layer including the compound represented by the general formula (1) including hydrogen atoms at the first position and the seventh position made it possible to fabricate an imaging element that had more favorable electric characteristics and more excellent color selectivity than those of a general imaging element.

Although the description has been given with reference to the first to third embodiments, the working examples, and the application examples, the contents of the present disclosure are not limited to the embodiment or the like described above. A variety of modifications are possible. In addition, the number of these organic photoelectric conversion sections and inorganic photoelectric conversion sections or the proportion between them are not also limited. Color signals of a plurality of colors may be obtained with an organic photoelectric conversion section alone.

Further, in the embodiments or the like described above, the examples have been described in which a plurality of electrodes included in the lower electrode21includes the two electrodes of the readout electrode21A and the accumulation electrode21B. There may be, however, provided additionally three or four or more electrodes including a transfer electrode, a discharge electrode, or the like.

It is to be noted that the effects described herein are merely examples, but are not limitative. In addition, there may be other effects.

It is to be noted that the present technology may also have configurations as follows. According to the present technology having the following configurations, an organic layer is formed by using the compound represented by the general formula (1) described above. This makes it possible to increase the selectivity for a wavelength detected by the organic layer and increase the spectral characteristics.

An Imaging Element Including:

A First Electrode;

a second electrode that is disposed to be opposed to the first electrode; and

an organic layer that is provided between the first electrode and the second electrode, the organic layer including a compound represented by the following general formula (1):

(where R1 and R4 each independently represent a hydrogen atom or a deuterium atom; R2 and R3 each independently represent an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group; R5 and R6 each independently represent a halogen atom, a hydrogen atom, or a alkyl group; R7 represents an aryl group, a heteroaryl group, or an alkenyl group; M represents boron or an m-valent metal atom and includes at least one of germanium, beryllium, magnesium, aluminum, chromium, iron, nickel, copper, zinc, or platinum; L represents a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; and n represents an integer greater than or equal to 1 and less than or equal to 6 and L's each independently represent a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group in a case where n−1 is 2 or more.)
[2]

The imaging element according to [1], in which the organic layer detects a wavelength of a band of any of an infrared region and a visible region.

The imaging element according to [1] or [2], in which the organic layer detects a wavelength of any band of a red band, a green band, and a blue band.

The imaging element according to any one of [1] to [3], in which the organic layer detects a wavelength of a green band.

The imaging element according to any one of [1] to [4], in which the organic layer includes a photoelectric conversion layer, and the photoelectric conversion layer includes the compound represented by the general formula (1).

The imaging element according to [5], in which the photoelectric conversion layer includes two or more types of organic semiconductor materials.

The imaging element according to any one of [1] to [6], in which the compound represented by the general formula (1) includes an organic semiconductor material having electron acceptability.

The imaging element according to any one of [1] to [7], in which M of the compound represented by the general formula (1) represents boron and L represents a fluorine atom or a fluorine-containing aryl group.

The imaging element according to any one of [1] to [8], in which R7 of the compound represented by the general formula (1) represents an aryl group or a heteroaryl group.

The imaging element according to any one of [1] to [8], in which R7 of the compound represented by the general formula (1) represents a heteroaryl group and includes a fluorine atom.

the organic layer includes a plurality of layers, and

at least one layer of the plurality of layers includes the compound represented by the general formula (1).

An Imaging Device Including

pixels each including one or more organic photoelectric conversion sections, in which

the organic photoelectric conversion sections each includea first electrode,a second electrode that is disposed to be opposed to the first electrode, andan organic layer that is provided between the first electrode and the second electrode, the organic layer including a compound represented by the following general formula (1):

(where R1 and R4 each independently represent a hydrogen atom or a deuterium atom; R2 and R3 each independently represent an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group; R5 and R6 each independently represent a halogen atom, a hydrogen atom, or a alkyl group; R7 represents an aryl group, a heteroaryl group, or an alkenyl group; M represents boron or an m-valent metal atom and includes at least one of germanium, beryllium, magnesium, aluminum, chromium, iron, nickel, copper, zinc, or platinum; L represents a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; and n represents an integer greater than or equal to 1 and less than or equal to 6 and L's each independently represent a halogen atom, a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group in a case where n−1 is 2 or more.)
[13]

The imaging device according to [12], in which the one or more organic photoelectric conversion sections and one or more inorganic photoelectric conversion sections are stacked in each of the pixels, the one or more inorganic photoelectric conversion sections each performing photoelectric conversion in a wavelength band different from wavelength bands of the organic photoelectric conversion sections.

The imaging device according to [13], in which the organic photoelectric conversion section including an organic layer including the compound represented by the general formula (1) is provided at a position closer to incident light than the other organic photoelectric conversion section and the inorganic photoelectric conversion sections.

The imaging device according to [13] or [14], in which

the one or more inorganic photoelectric conversion sections are formed to be buried in a semiconductor substrate, and

the one or more organic photoelectric conversion sections are formed on a first surface side of the semiconductor substrate.

The imaging device according to [15], in which a multilayer wiring layer is formed on a second surface side of the semiconductor substrate.

The imaging device according to any one of [13] to [16], in which each of the organic photoelectric conversion sections performs photoelectric conversion in a green band, and

an inorganic photoelectric conversion section that performs photoelectric conversion in a blue band and an inorganic photoelectric conversion section that performs photoelectric conversion in a red band are stacked in the semiconductor substrate.

The imaging device according to any one of [12] to [17], in which a plurality of the organic photoelectric conversion sections is stacked in each of the pixels, the plurality of the organic photoelectric conversion sections performing photoelectric conversion in respective wavelength ranges different from each other.

This application claims the priority on the basis of Japanese Patent Application No. 2019-139917 filed with Japan Patent Office on Jul. 30, 2019, the entire contents of which are incorporated in this application by reference.