Photoelectric conversion element, image sensor, optical sensor, and solid-state imaging device

Abstract

To provide a photoelectric conversion element capable of suppressing leakage current in the dark.SOLUTION: The photoelectric conversion element includes: a first electrode film, a second electrode film a photoelectric conversion film located between the first electrode film and the second electrode film. The photoelectric conversion film includes a photoelectric conversion layer and two auxiliary layers located between that photoelectric conversion layer and the second electrode film. The auxiliary layer close to the second electrode film out of the two auxiliary layers includes a compound expressed by the following formula (1): (R1 to R6 are each independently a hydrogen atom, a halogen atom, a linear, branched, or cyclic alkyl group, etc.).SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a photoelectric conversion element, an imaging element, an optical sensor, and a solid-state imaging device.

Background Art

[0002] Conventionally, a technique for photoelectrically converting visible light into an electrical signal is known and is widely used, for example, as an imaging element. Such an imaging element is provided in a solid-state imaging device such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor. In recent years, in solid-state imaging devices, the pixel size has been reduced, and an organic photoelectric conversion film for coping with this has been studied. For example, Patent Document 1 and Patent Document 2 disclose an organic photoelectric conversion film composed of subphthalocyanine and imides.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Solid-state imaging devices are required to achieve both high spectral selectivity and a high signal-to-noise ratio. Therefore, it is desirable for solid-state imaging devices to have high external quantum efficiency (EQE) and low dark current characteristics. To achieve such a balance, a method is known in which an electron transport layer and a hole blocking layer, and / or a hole transport layer and an electron blocking layer, are placed between the photoelectric conversion unit and the electrode unit. Here, electron transport layers, hole blocking layers, and electron blocking layers, which are widely used in the field of organic electronic devices, are placed at the interface between the electrode or conductive film and other films in the film that constitutes the device. These layers play a role in controlling the reverse movement of holes or electrons, respectively, and adjusting unnecessary leakage of holes or electrons. As a material used for such layers, for example, Patent Document 3 shows an example using 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA).

[0005] However, conventional hole blocking layers and electron blocking layers, including those disclosed in Patent Document 3, still have room for improvement in suppressing leakage current in the dark.

[0006] The present invention aims to provide a photoelectric conversion element, an image sensor, a light sensor, and a solid-state imaging device that can suppress leakage current in the dark. [Means for solving the problem]

[0007] The present invention is as follows. [1] A photoelectric conversion element comprising a first electrode film, a second electrode film, and a photoelectric conversion film located between the first electrode film and the second electrode film, The photoelectric conversion film comprises a photoelectric conversion layer and two auxiliary layers located between the photoelectric conversion layer and the second electrode film. Of the two auxiliary layers mentioned above, the auxiliary layer closest to the second electrode film is given by the following formula (1): [ka] (Each of R1, R2, R3, R4, R5, and R6 is independently selected from the group consisting of hydrogen atoms, halogen atoms, hydroxyl groups, thiol groups, amino groups, cyano groups, carboxyl groups, nitro groups, and optionally substituted linear, branched, or cyclic alkyl groups, thioalkyl groups, thioaryl groups, arylsulfonyl groups, aryloxy groups, alkylsulfonyl groups, alkylamino groups, arylamino groups, alkoxy groups, acylamino groups, acyloxy groups, aryl groups, carboxyamide groups, carboalkoxy groups, carboaryloxy groups, acyl groups, and monovalent heterocyclic groups. Any adjacent R1, R2, R3, R4, R5, and R6 may be part of a condensed aliphatic ring or a condensed aromatic ring. The condensed aliphatic ring and condensed aromatic ring may contain one or more atoms other than carbon.) A photoelectric conversion element containing a compound represented by [formula]. [2] The photoelectric conversion element described above, wherein the compound does not have an axis of symmetry in its molecular structure. [3] The photoelectric conversion element described in formula (1), wherein at least one of R1, R2, R3, and R4 is not a hydrogen atom. [4] The photoelectric conversion element of formula (1), wherein R2, R3 and R4 are hydrogen atoms, and R1 is selected from the group consisting of halogen atoms, hydroxyl groups, thiol groups, amino groups, cyano groups, carboxyl groups, nitro groups, and optionally substituted linear, branched or cyclic alkyl groups, thioalkyl groups, thioaryl groups, arylsulfonyl groups, aryloxy groups, alkylsulfonyl groups, alkylamino groups, arylamino groups, alkoxy groups, acylamino groups, acyloxy groups, aryl groups, carboxyamide groups, carboalkoxy groups, carboaryloxy groups, acyl groups, and monovalent heterocyclic groups. [5] An image sensor comprising the above-mentioned photoelectric conversion element. [6] The image sensor comprising two or more of the photoelectric conversion elements stacked together. [7] An image sensor comprising a plurality of the above-mentioned photoelectric conversion elements arranged in an array. [8] An optical sensor comprising the above-mentioned image sensor. [9] A solid-state imaging device comprising the above-mentioned image sensor. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a photoelectric conversion element, an image sensor, a light sensor, and a solid-state imaging device that can suppress leakage current in the dark. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view partially illustrating an example of the photoelectric conversion element of the present invention. [Figure 2] This is a schematic cross-sectional view partially illustrating another example of the photoelectric conversion element of the present invention. [Modes for carrying out the invention]

[0010] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"), with reference to the drawings as necessary. However, the present invention is not limited to the embodiments described below. The present invention can be modified in various ways without departing from its essence. In the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0011] The photoelectric conversion element of this embodiment comprises a first electrode film, a second electrode film, and a photoelectric conversion film located between the first electrode film and the second electrode film, wherein the photoelectric conversion film comprises a photoelectric conversion layer and two auxiliary layers located between the photoelectric conversion layer and the second electrode film, and of the two auxiliary layers, the auxiliary layer closer to the second electrode film is given by the following formula (1): [ka] It contains a compound represented by the following (hereinafter also referred to as "compound (1)"). Here, R1, R2, R3, R4, R5 and R6 are each independently a hydrogen atom, a halogen atom, a hydroxy group, a thiol group, an amino group, a cyano group, a carboxy group, a nitro group, and a linear, branched or cyclic alkyl group, thioalkyl group, thioaryl group, arylsulfonyl group, aryloxy group, alkylsulfonyl group, alkylamino group, arylamino group, alkoxy group, acylamino group, acyloxy group, aryl group, carboxamide group, carboalkoxy group, carboaryloxy group, acyl group, and a monovalent heterocyclic group which may be substituted, and any adjacent R1, R2, R3, R4, R5 and R6 may be part of a condensed aliphatic ring or a condensed aromatic ring. The condensed aliphatic ring and the condensed aromatic ring may contain one or more atoms other than carbon.

[0012] Although the reason why such a photoelectric conversion device can suppress the leakage current in the dark is not clear, the inventors think as follows. The photoelectric conversion device of this embodiment includes two auxiliary layers between the photoelectric conversion layer and the second electrode film, and the auxiliary layer closer to the second electrode film contains the compound (1). Thereby, due to the relatively low HOMO level of the compound (1), a rectifying effect is obtained that suppresses the movement of electrons generated in the photoelectric conversion layer to the second electrode film. As a result, it is considered possible to suppress the leakage current (hereinafter also referred to as "dark current") in the dark. However, the reason is not limited to this. In addition, the photoelectric conversion device of this embodiment can also have high photoelectric conversion efficiency. This is considered to be because the auxiliary layer closer to the second electrode film contains the compound (1), which enhances the chemical affinity between the second electrode film and the photoelectric conversion film and makes the energy gradient for moving electrons to the second electrode film smoother. However, the reason is not limited to this. Furthermore, the photoelectric conversion device of this embodiment can further suppress the whitening of the auxiliary layer provided between the photoelectric conversion layer and the second electrode film and the light scattering that may occur thereby. This is because even if the compound (1) in the auxiliary layer closer to the second electrode film is relatively easy to whitening, by using it in combination with another auxiliary layer that is difficult to whiten, the thickness of the auxiliary layer closer to the second electrode film can be made thinner.

[0013] (Compound) The compound (1) of this embodiment is represented by the above formula (1). From the viewpoint of having more excellent characteristics as a photoelectric conversion device and from the viewpoint of more effectively and surely exhibiting the effects of the present invention, it is preferable that the compound (1) does not have a symmetry axis in its molecular structure.

[0014] Here, the "symmetry axis" refers to a rotation axis that produces a molecule that cannot be distinguished from the original molecule when rotated 360° / n (n is an integer other than 1) as a symmetry operation for the molecule. The compound (1) of this embodiment does not have such a symmetry axis in its molecular structure.

[0015] The reason why compound (1), which lacks a symmetry axis in its molecular structure, exhibits superior properties as a photoelectric conversion element is not yet clear, but the inventors believe it to be as follows. However, the reasons are not limited to those listed below. In other words, because compound (1) has a specific structure that lacks a symmetry axis in its molecular structure, it is easier to have multiple stable structures with similar energy levels, making it difficult to obtain a highly regular molecular arrangement as a solid. This suppresses the occurrence of film thickness disturbances and electrical short circuits (pinholes) that can occur due to partial aggregation in the solid thin film, resulting in superior properties as a photoelectric conversion element.

[0016] On the other hand, compound (A) below has one axis of symmetry in its molecular structure, indicated by a dashed line. Compounds (B) and (C) have one axis of symmetry in their molecular structure, indicated by black circles, extending from front to back. Compound (D) has two axes of symmetry in its molecular structure, each indicated by a dashed line.

[0017] [ka]

[0018] Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0019] The linear alkyl group may be any linear alkyl group having 1 to 12 carbon atoms in the alkyl group, such as methyl (Me), ethyl (Et), n-propyl (n-Pr), n-butyl (n-Bu), n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and n-dodecyl groups.

[0020] The branched alkyl group may be any branched alkyl group having 1 to 12 carbon atoms, such as isopropyl (i-Pr), sec-butyl (s-Bu), tert-butyl (t-Bu), isopentyl, sec-pentyl, 3-pentyl, neopentyl, isohexyl, isooctyl, isononyl, isodecyl, and isododecyl. The linear or branched alkyl group may also have substituents. Examples of substituents include halogen atoms such as fluorine, monovalent groups having aromatic rings such as benzyl, naphthyl, and phenoxy, alkoxy, monovalent groups having heteroatoms such as aminoalkyl and thioalkyl groups, monovalent groups having heterocycles such as pyridyl, hydroxyl, carboxyl, amino, and thiol groups.

[0021] The cyclic alkyl group may be a cyclic alkyl group having 3 to 10 carbon atoms in the alkyl group, such as the cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, and cyclooctyl group. Furthermore, the cyclic alkyl group may have heteroatoms such as nitrogen, oxygen, and sulfur atoms in its ring. Examples of such cyclic alkyl groups include the pyrrolidinyl group, oxazolidinyl group, pyrazolidinyl group, thiazolidinyl group, imidazolidinyl group, dioxofuranyl group, tetrahydrofuranyl group, tetrahydrothiophenyl group, piperazinyl group, dioxanyl group, and morphonyl group. In addition, a monovalent group such as a hydroxyl group, carboxyl group, amino group, and thiol group may be bonded to the cyclic alkyl group.

[0022] The thioalkyl group (-SR; R indicates an alkyl group (same applies hereinafter)) and the thioaryl group (-SAr; Ar indicates an aryl group (same applies hereinafter)) may be a thioalkyl group with 1 to 12 carbon atoms in the alkyl group and a thioaryl group with 6 to 16 carbon atoms in the aryl group. Furthermore, the thioalkyl group and thioaryl group may have substituents such as an amino group, a hydroxyl group, a halogen atom, an alkoxy group, or a thioalkyl group. Examples of such thioalkyl groups and thioaryl groups include a methylthio group, an ethylthio group, a phenylthio group, a toluylthio group, an aminophenylthio group, a hydroxyphenylthio group, a fluorophenylthio group, a dimethylphenylthio group, and a methylthiophenylthio group.

[0023] The arylsulfonyl group (-SO2-Ar) may be any arylsulfonyl group having 6 to 16 carbon atoms in the aryl group, such as phenylsulfonyl group, toluenesulfonyl group, dimethylbenzenesulfonyl group, mesitylenesulfonyl group, octylbenzenesulfonyl group, and naphthalenesulfonyl group.

[0024] The aryloxy group (-O-Ar) may be an aryloxy group having 6 to 16 carbon atoms in the aryl group. Furthermore, the aryloxy group may have substituents such as a cyano group, a halogen atom such as a fluorine atom, a hydroxyl group, an alkoxy group such as a methoxy group, an amino group, an alkylamino group, a thiol group, and an aryloxy group. Examples of such aryloxy groups include phenoxy group, cyanophenoxy group, methylcyanophenoxy group, dimethylcyanophenoxy group, fluorocyanophenoxy group, dicyanophenoxy group, methoxycyanophenoxy group, tricyanophenoxy group, cyanonaphthoxy group, dicyanonaphthoxy group, 2-methylphenoxy group, 3-methylphenoxy group, 4-methylphenoxy group, fluoromethylphenoxy group, dimethylphenoxy group, 3-hydroxyphenoxy group, Examples include fluoro-3-hydroxyphenoxy group, 2-hydroxyphenoxy group, fluoro-2-hydroxyphenoxy group, methoxyphenoxy group, ethoxyphenoxy group, fluorophenoxy group, perfluorophenoxy group, dimethoxyphenoxy group, aminophenoxy group, N,N-dimethylaminophenoxy group, thiophenoxy group, (trifluoromethyl)phenoxy group, naphthoxy group, methoxynaphthoxy group, fluoronaphthoxy group, and phenoxyphenoxy group.

[0025] The alkylsulfonyl group (-SO2-R) may be an alkylsulfonyl group having 1 to 12 carbon atoms in the alkyl group, such as a mesyl group, an ethylsulfonyl group, and an n-butylsulfonyl group.

[0026] The alkylamino group (-NHR or -NR2, where the two Rs may be the same or different) may be an alkylamino group having 1 to 12 carbon atoms in the alkyl group, and examples include methylamino group, ethylamino group, n-propylamino group, n-butylamino group, n-pentylamino group, n-hexylamino group, n-heptylamino group, n-octylamino group, n-nonylamino group, n-decylamino group, n-dodecylamino group, isopropylamino group, sec-butylamino group, tert-butylamino group, isopentylamino group, sec-pentylamino group, 3-pentylamino group, neopentylamino group, isohexylamino group, isoheptylamino group, isooctylamino group, isononylamino group, isodecylamino group and isododecylamino group, dimethylamino group, diethylamino group, diisopropylamino group and isopropylethylamino group.

[0027] The arylamino group (-NHAr or -NAr2, where the two Ar groups may be the same or different) may be an arylamino group having 6 to 16 carbon atoms, such as anilyl group, toluidinyl group, dimethylanilyl group, isopropylarilinyl group, t-butylanilyl group, fluoroanilyl group, trifluoromethylanilyl group, bis(trifluoromethyl)anilyl group, pyridylamino group, methylpyridylamino group, fluoropyridylamino group, pyrimidylamino group, and biphenylamino group.

[0028] The alkoxy group (-OR) may be an alkoxy group having 1 to 12 carbon atoms, and examples include methoxy, ethoxy, n-propoxy, n-butyroxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy and n-dodecoxy, isopropoxy, sec-butyroxy, tert-butyroxy, isopentoxy, sec-pentoxy, 3-pentoxy, neopentoxy, isohexoxy, isooctoxy, isononoxy, isodecoxoxy, and isododecoxy.

[0029] The acylamino group (-NH-COR or -NH-COAr) may have 1 to 12 carbon atoms in the alkyl group or 6 to 16 carbon atoms in the aryl group, and may have substituents such as a halogen atom like a fluorine atom, an alkoxy group, and a cyano group. Examples of such acylamino groups include acetylamino group, propionylamino group, benzoylamino group, methylbenzoylamino group, dimethylbenzoylamino group, methoxybenzoylamino group, cyanobenzoylamino group, and bis(trifluoromethyl)benzoylamino group.

[0030] The acyloxy group (-O-COR or -O-COAr) may have 1 to 12 carbon atoms in the alkyl group or 6 to 16 carbon atoms in the aryl group. The acyloxy group may further have a halogen atom such as a fluorine atom and a substituent such as a cyano group, and may have a heteroatom such as a nitrogen atom in the aromatic ring. Examples of such acyloxy groups include benzoyloxy group, toluyloxy group, dimethylbenzoyloxy group, cyanobenzoyloxy group, fluorobenzoyloxy group, bis(trifluoromethyl)benzoyloxy group, pyridinecarboxyl group, and methylpyridinecarboxyl group.

[0031] The aryl group (-Ar) may be an aryl group having 6 to 16 carbon atoms. The aryl group may further have substituents such as an amino group, a hydroxyl group, a thiol group, a halogen atom such as a fluorine atom, a nitro group, and a cyano group, and may also have a heteroatom such as a nitrogen atom in the aromatic ring. Examples of such aryl groups include phenyl group, methylphenyl group, ethylphenyl group, dimethylphenyl group, trimethylphenyl group, methoxyphenyl group, dimethoxyphenyl group, trimethoxyphenyl group, methoxymethylphenyl group, aminophenyl group, diaminophenyl group, aminomethylphenyl group, hydroxyphenyl group, dihydroxyphenyl group, hydroxymethylphenyl group, hydroxyethylphenyl group, thiophenyl group, methylthiophenyl group, dithiophenyl group, fluorophenyl group, fluoromethylphenyl group, trifluoromethylphenyl group, perfluorophenyl group, fluoro(trifluoromethyl)phenyl group, bis(trifluoromethyl)phenyl group, cyanophenyl group, methylcyanophenyl group, dimethylcyanophenyl group, dicyanophenyl group, methoxycyanophenyl group, tricyanophenyl group, and dicyanophenyl group. Examples include methylcyanopyridyl group, (trifluoromethyl)cyanopyridyl group, dimethylcyanopyridyl group, dicyanopyridyl group, methoxycyanopyridyl group, tricyanopyridyl group, cyanopyridyl group, naphthyl group, nitrophenyl group, dinitrophenyl group, nitrofluorophenyl group, methylnaphthyl group, ethylnaphthyl group, dimethylnaphthyl group, trimethylnaphthyl group, methoxynaphthyl group, dimethoxynaphthyl group, trimethoxynaphthyl group, aminonaphthyl group, diaminonaphthyl group, aminomethylnaphthyl group, hydroxynaphthyl group, dihydroxynaphthyl group, hydroxymethylnaphthyl group, hydroxyethylnaphthyl group, thionaphthyl group, methylthionaphthyl group, dithionaphthyl group, fluoronaphthyl group, trifluoromethylnaphthyl group, perfluoronaphthyl group, di(trifluoromethyl)naphthyl group, biphenyl group, and cyanobiphenyl group.

[0032] The carboxyamide group (-CO-NH2, -CO-NHR, -CONR2, where the two Rs may be the same or different, and -CONHAr, or -CONAr2, where the two Ars may be the same or different) may be a carboxyamide group in which the alkyl group has 1 to 12 carbon atoms or the aryl group has 6 to 16 carbon atoms, for example, the dimethylcarboxyamide group and the diphenylcarboxyamide group.

[0033] The carboalkoxy group and carboaryloxy group (-COOR or -COOAr) may be a carboalkoxy group having 1 to 12 carbon atoms in the alkyl group or 6 to 16 carbon atoms in the aryl group, for example, a carbomethoxy group and a carbophenoxy group.

[0034] The monovalent heterocyclic group may be any monovalent heterocyclic group having 3 to 14 carbon atoms, for example, furanyl group, thienyl group, pyrrolyl group, pyrazolyl group, imidazolyl group, triazolyl group, oxazolyl group, dioxazolyl group, isoxazolyl group, oxadiazolyl group, thiazolyl group, isothiazolyl group, thiadiazolyl group, triazolyl group, indolyl group, indolinyl group, indolidinyl group, indazolinyl group, indoleninyl group, benzofuranyl group, benzothienyl group, carbazolyl group, dibenzofuranyl group, Examples include dibenzothienyl group, pyridinyl group, diazinyl group, oxazinyl group, thiadinyl group, dioxynyl group, dithienyl group, triazinyl group, pyrimidinyl group, pyrazinyl group, pyridadinyl group, quinolinyl group, isoquinolinyl group, cinnonyl group, phthalazinyl group, quinazolinyl group, naphthilidinyl group, prinyl group, pteridinyl group, acridinyl group, phenanthridine group, phenanthrolinyl group, xanthenyl group, phenoxadinyl group, thianthrenyl group, morpholinyl group, and phenadinyl group.

[0035] From the viewpoint of more effectively and reliably achieving the effects of the present invention, it is preferable that at least one of R1, R2, R3, and R4 in compound (1) is not a hydrogen atom, more preferably that R1 is not a hydrogen atom, and more preferably that R2, R3, and R4 are hydrogen atoms. From a similar viewpoint, it is preferable that at least one of R1, R2, R3, and R4 is a hydrogen atom, more preferably that R1 is a hydrogen atom, and more preferably that none of R2, R3, and R4 are hydrogen atoms. Furthermore, from the viewpoint of ease of manufacture and cost, it is preferable that R5 and R6 are the same. Furthermore, if R2, R3, and R4 are hydrogen atoms, it is preferable that R1 is selected from the group consisting of halogen atoms, hydroxyl groups, thiol groups, amino groups, cyano groups, carboxyl groups, nitro groups, and optionally substituted linear, branched, or cyclic alkyl groups, thioalkyl groups, thioaryl groups, arylsulfonyl groups, aryloxy groups, alkylsulfonyl groups, alkylamino groups, arylamino groups, alkoxy groups, acylamino groups, acyloxy groups, aryl groups, carboxyamide groups, carboalkoxy groups, acyl groups, and monovalent heterocyclic groups.

[0036] The compound (1) in this embodiment preferably has a molecular weight of 300 or more, more preferably 350 or more, and even more preferably 400 or more. A molecular weight of 300 or more can further suppress changes in physical properties caused by thermal motion of molecules that may occur during heating operations in the manufacturing process of organic thin films using compound (1) or in high-temperature operating environments. In particular, when compound (1) is formed by vacuum deposition, the molecular weight of compound (1) is preferably 1000 or less, more preferably 950 or less, and even more preferably 900 or less. A molecular weight of 1000 or less allows for lower thermal energy required for sublimation when forming an organic thin film of compound (1) by vacuum deposition, enabling the formation of a good thin film without thermal degradation of compound (1). However, when forming a thin film by solution coating, such problems are less likely to occur, so the molecular weight of compound (1) may be greater than 1000.

[0037] The compound (1) of this embodiment preferably has a temperature at which the weight loss due to heating in an inert gas atmosphere becomes 5% or less of the weight before heating (hereinafter sometimes referred to as the "5% weight loss temperature") of 200°C or higher, and more preferably 250°C or higher. When the 5% weight loss temperature is 200°C or higher, changes in physical properties caused by thermal motion of molecules that may occur during heating operations in the manufacturing process of organic thin films using compound (1) or in high-temperature operating environments can be further suppressed. The 5% weight loss temperature can be measured by differential thermal analysis.

[0038] Compound (1) of this embodiment is obtained, for example, by synthesis as described later. In the product obtained by synthesis (100% by mass), the content of compound (1) is preferably 90% by mass or more, more preferably 93% by mass, and even more preferably 97% by mass or more. By having a content of 90% by mass or more, it is possible to more effectively and reliably avoid the trapping of carriers to impurity levels caused by unintended impurities when used in a photoelectric conversion element. As a result, carrier recombination is suppressed, and a photoelectric conversion element with superior performance can be obtained. The content can be measured by liquid chromatography, gas chromatography, elemental analysis, etc., but any known method is acceptable.

[0039] The following shows preferred combinations of R1, R2, R3, R4, R5, and R6. In the table, "Ph" represents a phenyl group, "Me" represents a methyl group, "Et" represents an ethyl group, "Hx" represents an n-hexyl group, "Th" represents a thiophenyl group, "Fu" represents a furanyl group, "Po" represents a pyrrolyl group, and "Py" represents a pyridinyl group. Furthermore, "m-" indicates that the two bonding sites to the phenyl group are in the meta position, "p-" indicates that the two bonding sites to the phenyl group are in the para position, and "1,3,5" indicates that the three bonding sites to the phenyl group are in the 1,3,5 positions. However, compound (1) is not limited to these.

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] Specific examples of compound (1) are shown below. However, compound (1) is not limited to these examples. [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] Compound (1) can be synthesized, for example, by the following scheme. [ka]

[0057] More specifically, intermediate (α) is first obtained by a halogenation reaction described in Tetrahedron Letters, 546314 (2013).

[0058] Compound (1) can be obtained by proceeding with a side-chain addition reaction via an imidized intermediate (α) obtained from the acquired intermediate. Alternatively, compound (1) can also be obtained by further imidation reactions via the intermediate obtained from the side-chain addition reaction of intermediate (α). Imidation can be carried out, for example, by the method described in Organic Electronics, 63, 250 (2018). The side-chain addition reaction can be carried out by a coupling reaction or by the method described in Asian Journal of Organic Chemistry, 2, 779 (2013).

[0059] [ka] Alternatively, compound (1) can be obtained by the following schemes utilizing halogenation reactions, imide reactions, and side-chain addition reactions.

[0060] [ka] [ka] [ka]

[0061] (Photoelectric conversion element) The photoelectric conversion element of this embodiment generates an electric charge corresponding to the amount of incident light and outputs the generated charge to the outside of the photoelectric conversion element via a capacitor for storing the generated charge (also called a "storage unit") and a transistor circuit for reading it out (also called a "readout unit"). Here, the photoelectric conversion element is defined as having a photoelectric conversion film that absorbs at least a portion of the incident light placed between a pair of opposing electrodes, and light is incident on the photoelectric conversion element from above the electrodes. The photoelectric conversion film is a photosensitive thin film containing a material that absorbs at least a portion of the incident light in the infrared region, and generates holes and electrons as a result of the incidence of light. Furthermore, the photoelectric conversion element of this embodiment may also have a photoelectric conversion element that generates an electric charge corresponding to the amount of incident light in the infrared region (hereinafter also referred to as an "infrared photoelectric conversion element"), where the infrared photoelectric conversion element is defined as having a photoelectric conversion film that absorbs infrared light (infrared photoelectric conversion film) placed between a pair of opposing electrodes, and light is incident on the infrared photoelectric conversion element from above the electrodes. Furthermore, the infrared photoelectric conversion film is a photosensitive thin film containing a material that absorbs at least a portion of incident light in the infrared region (hereinafter referred to as "infrared absorbing material"), and generates holes and electrons as a result of the incidence of light.

[0062] The photoelectric conversion element of this embodiment will be described with reference to the figures as appropriate. The photoelectric conversion element 100 shown in Figure 1 comprises a lower electrode 102 which is a first electrode film, an upper electrode 106 which is a second electrode film, and a photoelectric conversion film 110 located between the lower electrode 102 and the upper electrode 106. The photoelectric conversion element 100 may also have a substrate 101, which is normally insulating, on the side of the upper electrode 106 opposite to the photoelectric conversion film 110.

[0063] The lower electrode 102, which is the first electrode film, is made of a light-transmitting conductive film, for example, ITO (indium tin oxide). The material constituting the lower electrode 102 is not limited to ITO, and examples include tin oxide (SnO2)-based materials with dopants, and zinc oxide-based materials with dopants added to zinc oxide (ZnO). Examples of zinc oxide-based materials include aluminum zinc oxide (AZO) with aluminum (Al) dopant added, gallium zinc oxide (GZO) with gallium (Ga) dopant added, and indium zinc oxide (IZO) with indium (In) dopant added. Alternatively, examples of materials constituting the lower electrode 102 include CuI, InSbO4, ZnMgO, CuInO2, MgIN2O4, CdO, and ZnSnO3. The thickness of the lower electrode 102 is, for example, 5 nm to 3000 nm, and may be 5 nm to 500 nm, or 10 nm to 300 nm.

[0064] The upper electrode 106, which is the second electrode film, may be made of a conductive film having the same light transmittance as the lower electrode 102. In a solid-state imaging device that uses a solid-state image sensor as a single pixel, this upper electrode 106 may be separated for each pixel, or it may be formed as a common electrode for each pixel. The thickness of the upper electrode 106 may be, for example, 5 nm to 3000 nm, 5 nm to 500 nm, or 10 nm to 300 nm.

[0065] The conductivity of the materials used for electrodes, such as the first and second electrode films, is not particularly limited as long as it does not unnecessarily hinder the photoelectric element's light reception. However, from the viewpoint of the photoelectric element's signal strength and power consumption, it is preferable that the conductivity be as high as possible. For example, as a transparent electrode, an ITO film with a sheet resistance of 300 Ω / □ or less is sufficient for functioning as an electrode. However, commercially available substrates equipped with ITO films having a conductivity of several Ω / □ (e.g., 5-9 Ω / □) are also available, and such substrates with high conductivity are desirable.

[0066] When using an ITO film, the electrode thickness can be arbitrarily selected considering conductivity, but is usually between 5 nm and 3000 nm, preferably between 10 nm and 300 nm. Methods for forming films such as ITO include conventionally known methods such as vapor deposition, electron beam method, sputtering, chemical reaction method, and coating method. The ITO film provided on the substrate may be subjected to UV-ozone treatment or plasma treatment as needed.

[0067] Furthermore, when stacking multiple photoelectric conversion films with different wavelengths to be detected, the electrode films used between each photoelectric conversion film (these are electrode films other than the pair of electrodes mentioned above) need to transmit light of wavelengths other than those detected by each photoelectric conversion film. From this viewpoint, it is preferable to use a material that transmits 90% or more of the incident light for the electrode films, and more preferable to use a material that transmits 95% or more of the light.

[0068] Furthermore, if a visible photoelectric conversion unit that senses infrared light or light in a different visible light range is provided below the photoelectric conversion element in this embodiment, the electrodes used in the photoelectric conversion element preferably have a transmittance of 90% or more for visible light and infrared light, and more preferably 95% or more.

[0069] As electrode materials that satisfy these conditions, transparent conductive oxides (TCOs) with high transmittance to visible and infrared light and low resistance are preferred. Although thin metal films such as Au can also be used as electrodes, the resistance increases drastically when trying to achieve a transmittance of 90% or more. Therefore, TCOs are preferred as electrodes. Among TCOs, ITO, IZO, AZO, FTO, SnO2, TiO2, and ZnO2 are particularly preferred.

[0070] The method for forming electrodes is not particularly limited and can be appropriately selected considering its suitability with the electrode material. When transparent electrodes are used, specific methods for forming them include wet methods such as printing and coating, physical methods such as vacuum deposition, sputtering, and ion plating, and chemical methods such as CVD and plasma CVD. Furthermore, when the electrode material is a transparent conductive metal oxide such as ITO, methods for forming it include, for example, electron beam methods, sputtering, resistance heating deposition, chemical reaction methods (sol-gel methods, etc.), and methods of coating a dispersion of the metal oxide. In addition, UV-ozone treatment and plasma treatment can be applied to films of transparent conductive metal oxides such as ITO.

[0071] The photoelectric conversion film 110 comprises a photoelectric conversion layer 104 and a second auxiliary layer 105 and a third auxiliary layer 107 located between the photoelectric conversion layer 104 and the upper electrode 106. Of these auxiliary layers 105 and 107, the third auxiliary layer 107, which is closer to the upper electrode 106, is adjacent to the upper electrode 106, while the second auxiliary layer 105 is located on the photoelectric conversion layer 104 side of the third auxiliary layer 107. Although the photoelectric conversion film 110 shown in Figure 1 comprises a first auxiliary layer 103, a second auxiliary layer 105, and a third auxiliary layer 107, the photoelectric conversion film does not necessarily have to have an auxiliary layer between the lower electrode 102 and the photoelectric conversion layer 104.

[0072] The photoelectric conversion layer 104 may be an organic semiconductor film commonly used as a photoelectric conversion layer. Furthermore, in the photoelectric conversion layer 110, these organic semiconductor films and organic thin films may be one or more layers. If there is one layer, a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film thereof (bulk heterostructure) may be used. On the other hand, if there are multiple layers, the number of layers may be approximately 2 to 10, and the structure may consist of stacked p-type organic semiconductor films, n-type organic semiconductor films, or mixed films thereof (bulk heterostructure), with buffer layers inserted between the layers.

[0073] The photoelectric conversion layer 104 in this embodiment may or may not contain compound (1), and may contain materials other than compound (1). Among these, it is preferable that the photoelectric conversion layer 104 contains at least one of organic p-type semiconductors, organic n-type semiconductors, and light-absorbing materials, as this allows for more efficient conversion of incident light energy of a desired wavelength into an electrical signal. Among these, it is preferable that the light-absorbing material is either an organic p-type semiconductor that readily donates electrons (has a small ionization potential) or an organic n-type semiconductor that readily accepts electrons (has a high electron affinity), as this allows for even more efficient conversion of incident light energy into an electrical signal. Here, the ionization potential (HOMO level) refers to the value measured by photoelectron yield spectroscopy or photoelectron spectroscopy. The electron affinity (LUMO level) refers to the value obtained by calculating the energy band gap value from the longest wavelength absorption edge of the near-infrared spectral spectrum and subtracting it from the HOMO level, or the value measured by inverse photoelectron spectroscopy.

[0074] When using an organic semiconductor film, the film may consist of one layer or two or more layers. The organic semiconductor film may be an organic p-type semiconductor film, an organic n-type semiconductor film, a light-absorbing material film, or a mixed film (bulk heterostructure) thereof. In particular, it is preferable that the organic semiconductor film has a bulk heterojunction structure layer. In such a case, by incorporating a bulk heterojunction structure into the photoelectric conversion film, the disadvantage of the short carrier diffusion length of the photoelectric conversion film can be compensated for, and the photoelectric conversion efficiency can be improved.

[0075] The thickness of the photoelectric conversion layer 104 may be, for example, 0.5 nm or more and 5000 nm or less, 1 nm or more and 1000 nm or less, or 5 nm or more and 500 nm or less.

[0076] The following provides a detailed explanation of organic semiconductors.

[0077] Organic p-type semiconductors are donor organic semiconductors (hereinafter also called "donor organic compounds"), mainly represented by hole-transporting organic compounds, which are organic compounds that readily donate electrons. More specifically, they refer to the organic compound with the lower ionization potential when two organic materials are brought into contact. Therefore, any organic compound with electron-donating properties can be used as a donor organic compound.

[0078] Examples of such donor organic compounds include triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluorantene derivatives), and metal complexes having nitrogen-containing heterocyclic compounds as ligands. However, as mentioned above, any organic compound with a lower ionization potential than the organic compound used as the acceptor organic compound can be used as a donor organic semiconductor.

[0079] Organic n-type semiconductors are acceptor organic semiconductors (hereinafter also referred to as "acceptor organic compounds"), mainly represented by electron-transporting organic compounds, and refer to organic compounds that have a property of readily accepting electrons. More specifically, they refer to the organic compound with the greater electron affinity when two organic compounds are used in contact. Therefore, any organic compound that has electron-accepting properties can be used as an acceptor organic compound.

[0080] Examples of such acceptor organic compounds include condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluorantene derivatives, fullerene derivatives), and 5-7 membered heterocyclic compounds containing nitrogen, oxygen, and sulfur atoms (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazine Examples include metal complexes having ligands such as zole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaidene, oxadiazole, imidazopyridine, pyrridine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, and tripenzazepine), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and nitrogen-containing heterocyclic compounds. However, as mentioned above, any organic compound with a greater electron affinity than the organic compound used as the donor organic compound can be used as an acceptor organic semiconductor.

[0081] Light-absorbing materials are compounds that have a maximum light absorption wavelength in the visible light range, particularly in the range of 450 nm to 650 nm. It is desirable that the absorption intensity of the light-absorbing material at its maximum light absorption wavelength is greater than the absorption intensity of the donor organic compound or the acceptor organic compound at its maximum light absorption wavelength. Having such an absorption intensity allows for the selective absorption of incident light at the light-absorbing material's maximum light absorption wavelength. After the incident light is absorbed by the light-absorbing material and the photons become excitons, exciton separation occurs at the interface between the donor organic compound and the acceptor organic compound, efficiently generating hole and electron carriers.

[0082] As such light-absorbing materials, compounds generally called dyes can be used. For example, phthalocyanine derivatives, subphthalocyanine derivatives, quinacridone derivatives, porphyrin derivatives, naphthalene or perylene derivatives, phthaloperylene derivatives, styryl derivatives, cyanine derivatives, hemicyanine derivatives, merocyanine derivatives, rhodacyanine derivatives, oxonol derivatives, hemioxonol derivatives, croconium derivatives, squarylium derivatives, azametine derivatives, allylidene derivatives, azo derivatives, azomethine derivatives, metallocene derivatives, fulgide derivatives, phenazine derivatives, phenothiazine derivatives, polyene derivatives, acridine derivatives, acridinone derivatives, diphenylamine derivatives, triarylamine derivatives such as triphenylamine, naphthylamine and styrylamine, quinophthalone derivatives, phenoxazine derivatives, chlorophyll derivatives, rhodamine derivatives, diphenylmethane or triphenylmethane derivatives, xanthene derivatives, acridine derivatives, phenoxazine derivatives, quinoline derivatives, oxazine Examples of derivatives include thiazine derivatives, quinone derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, indigo or thioindigo derivatives, pyrrole derivatives, pyridine derivatives, dipyrine derivatives, indole derivatives, diketopyrrolopyrrole derivatives, coumarin derivatives, fluorene derivatives, fluorenone derivatives, fluorantene derivatives, anthracene derivatives, pyrene derivatives, carbazole derivatives, phenylenediamine derivatives, benzidine derivatives, phenanthroline derivatives, imidazole derivatives, oxazoline derivatives, thiazoline derivatives, triazole derivatives, thiadiazole derivatives, oxazole derivatives, thiazoline derivatives, oxazole derivatives, thiazoline derivatives, oxadiazole derivatives, thiophene derivatives, selenofen derivatives, silole derivatives, germole derivatives, stilbene derivatives, phenylenevinylene derivatives, pentacene derivatives, rubrene derivatives, thienothiophene derivatives, benzodithiophene derivatives, xanthenoxanthene derivatives, and fullerene derivatives. Furthermore, as mentioned above, any compound with an absorption intensity greater than that of the donor organic compound or acceptor organic compound at its maximum light absorption wavelength can be used as a light-absorbing material.Furthermore, light-absorbing materials can also function as either donor or acceptor organic compounds.

[0083] The first auxiliary layer 103 may be a single layer or two or more layers. The first auxiliary layer 103 may comprise at least one of an electron blocking layer and a hole transport layer. If the first auxiliary layer 103 comprises two of these, it is usually stacked in the order of a hole transport layer and an electron blocking layer, starting from the photoelectric conversion layer 104 side. The hole transport layer plays the role of transporting holes generated in the photoelectric conversion layer 104 to the first electrode 102 and blocking the movement of electrons from the first electrode 102 to the photoelectric conversion layer 104. The electron blocking layer prevents the movement of electrons from the first electrode 102 to the photoelectric conversion layer 104, prevents recombination within the photoelectric conversion layer 104, reduces dark current, reduces noise, and expands the dynamic range. Alternatively, one layer may have both the functions of an electron blocking layer and a hole transport layer. The thickness of the first auxiliary layer 103 is preferably 10 nm to 300 nm, more preferably 30 nm to 250 nm, and even more preferably 50 nm to 200 nm, from the viewpoint of suppressing dark current and preventing a decrease in photoelectric conversion efficiency.

[0084] The second auxiliary layer 105 may be a single layer or two or more layers. The second auxiliary layer 105 may be, for example, an electron transport layer. The electron transport layer plays the role of transporting generated electrons from the photoelectric conversion layer 104 to the second electrode 106 and blocking the movement of holes from the second electrode 106 to the photoelectric conversion layer 104. From the viewpoint of suppressing dark current and preventing a decrease in photoelectric conversion efficiency, the thickness of the second auxiliary layer 105 is preferably 5 nm to 200 nm, more preferably 15 nm to 130 nm, and even more preferably 25 nm to 100 nm.

[0085] The third auxiliary layer 107 is an auxiliary layer closer to the upper electrode 106 than the second auxiliary layer 105, and may be, for example, a hole blocking layer. The hole blocking layer prevents the movement of holes from the second electrode 106 to the photoelectric conversion layer 104, prevents recombination within the photoelectric conversion layer 104, reduces dark current, reduces noise, and expands the dynamic range. At least one of the layers located between the photoelectric conversion layer 104 and the upper electrode 106 may have the functions of both a hole blocking layer and an electron transport layer. From the viewpoint of suppressing dark current and preventing a decrease in photoelectric conversion efficiency, the thickness of the third auxiliary layer 107 is preferably 5 nm to 200 nm, more preferably 15 nm to 130 nm, and even more preferably 25 nm to 100 nm.

[0086] The compound (1), which is a material for the photoelectric conversion element according to this embodiment, is included in at least the third auxiliary layer 107 of these auxiliary layers. The third auxiliary layer 107 may contain materials other than compound (1). The content of compound (1) in the third auxiliary layer 107 is not particularly limited as long as it exhibits the performance necessary for use as an auxiliary layer close to the upper electrode 106. For example, its content may be 50% by mass or more of the total amount of the third auxiliary layer 107, but from the viewpoint of more effectively and reliably achieving the effects of the present invention, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The upper limit of its content may be 100% by mass.

[0087] The following describes materials other than compound (1) according to this embodiment that may be included in each layer of the auxiliary layer.

[0088] The material for the hole transport layer is not particularly limited as long as it is known as a hole transport layer in photoelectric conversion elements such as solid-state image sensors. Examples include polyaniline and its doping materials, and cyanide compounds described in International Publication No. 2006 / 019270.

[0089] More specifically, materials that constitute the hole transport layer include selenium, iodides such as copper iodide (CuI), cobalt complexes such as layered cobalt oxide, CuSCN, molybdenum oxide (MoO3, etc.), nickel oxide (NiO, etc.), 4CuBr·3S(C4H9), and organic hole transporters. Among these, copper iodide (CuI) is an example of an iodide. An example of a layered cobalt oxide is AxCoO2 (where A represents Li, Na, K, Ca, Sr, or Ba, and 0≦X≦1). Examples of organic hole transporters include polythiophene derivatives such as poly-3-hexylthiophene (P3HT), poly(3,4-ethylenedioxythiophene), (PEDOT; for example, the trade name "BaytronP" from Starck Vitek), fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeO-TAD), carbazole derivatives such as polyvinylcarbazole, triphenylamine derivatives, diphenylamine derivatives, polysilane derivatives, and polyaniline derivatives. Furthermore, examples of materials for the hole transport layer include compound semiconductors having monovalent copper such as CuInSe2 and copper sulfide (CuS), gallium phosphide (GaP), nickel oxide (NiO), cobalt oxide (CoO), iron oxide (FeO), bismuth oxide (Bi2O3), molybdenum oxide (MoO2), and chromium oxide (Cr2O3).

[0090] Furthermore, it is preferable that the hole transport layer has a LUMO level shallower than the LUMO level of the photoelectric conversion film, as this provides an electron blocking function that has a rectifying effect that suppresses the movement of electrons generated in the photoelectric conversion film toward the electrode side. Such a hole transport layer is also called an electron blocking layer.

[0091] Among the materials that constitute the electron blocking layer, low molecular weight organic compounds include, for example, aromatic diamine compounds such as N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) and 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD), oxazoles, oxadiazoles, triazoles, imidazoles, imidazolons, stilbene derivatives, pyrazoline derivatives, tetrahydroimidazoles, polyarylalkanes, and porcine. Dienes, 4,4',4” Tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA), porphyrins, copper tetraphenylporphyrins, phthalocyanines, copper phthalocyanines and titanium phthalocyanine oxides, and other porphyrin compounds, triazole derivatives, oxadizasol derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino substitutions Examples of materials include chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, and silazane derivatives. Examples of polymeric organic compounds include polymers such as phenylenevinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, and diacetylene, as well as their derivatives. Even if a compound is not electron-donating, any compound with sufficient hole transport properties can be used as a material for the electron-blocking layer. Furthermore, examples of inorganic compounds among the materials for the electron-blocking layer include metal oxides such as calcium oxide, chromium oxide, chromium copper oxide, manganese oxide, cobalt oxide, nickel oxide, copper oxide, gallium copper oxide, strontium copper oxide, niobium oxide, molybdenum oxide, indium copper oxide, indium silver oxide, and iridium oxide, as well as selenium, tellurium, and antimony sulfide. These can be used individually or in combination of two or more.

[0092] The method for forming the hole transport layer and electron blocking layer may be any conventionally known method, and may be either a dry film formation method such as vacuum deposition or a wet film formation method such as solution coating. However, from the viewpoint of being able to level the coated surface, a wet film formation method is preferred. Examples of dry film formation methods include vapor deposition methods such as vacuum deposition and sputtering. Vacuum deposition may be either physical vapor deposition (PVD) or chemical vapor deposition (CVD), but physical vapor deposition such as vacuum deposition is preferred. Examples of wet film formation methods include inkjet, spray, nozzle print, spin coat, dip coat, cast, die coat, roll coat, bar coat, and gravure coat.

[0093] The materials constituting the electron transport layer are not particularly limited as long as they are known as electron transport layers in photoelectric conversion elements such as solid-state image sensors. Examples include octa-azaporphyrin, perfluoro derivatives of p-type semiconductors (such as perfluoropentacene and perfluorophthalocyanine), fullerenes, fullerene derivatives (e.g., [6,6]-Phenyl-C61-Butyric Acid Methyl Ester; PCBM), perylene, indenoindene and indenoindene derivatives, and other organic compounds, as well as inorganic oxides such as titanium dioxide (TiO2, etc.), nickel oxide (NiO), tin oxide (SnO2), tungsten oxide (WO2, WO3, W2O3, etc.), zinc oxide (ZnO), niobium oxide (Nb2O5, etc.), tantalum oxide (Ta2O5, etc.), yttrium oxide (Y2O3, etc.), and strontium titanate (SrTiO3, etc.). The electron transport layer may be porous or dense, and when stacking them, it is preferable to stack the porous electron transport layer and the dense electron transport layer in that order from the photoelectric conversion film side.

[0094] Furthermore, it is preferable that the electron transport layer has a HOMO level deeper than the HOMO level of the photoelectric conversion film, as this provides a hole-blocking function that suppresses the movement of holes generated in the photoelectric conversion film toward the opposing electrode. Such an electron transport layer is also called a hole-blocking layer.

[0095] Materials that constitute the hole blocking layer include, for example, oxadiazole derivatives such as 1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene (OXD-7), anthraquinodimethane derivatives, diphenylquinone derivatives, vasocuproin, vasophenanthroline, and their derivatives, triazine compounds, triazole compounds, tris(8-hydroxyquinolinate)aluminum complexes, bis(4-methyl-8-quinolinate)aluminum complexes, silole compounds, and porphyrins. Examples include styryl compounds such as DCM (4-dicyanomethylene-2-methyl-6-(4-(dimethylaminostyryl))-4Hpyran), n-type semiconductor materials such as naphthalenetetracarboxylic anhydride (NTCDA), naphthalenetetracarboxylic diimide, perylenetetracarboxylic anhydride (PTCDA), and perylenetetracarboxylic diimide, n-type inorganic oxides such as titanium dioxide, zinc oxide, and gallium oxide, and alkali metal fluorides such as lithium fluoride, sodium fluoride, and cesium fluoride. Furthermore, alkali metal compounds doped into organic semiconductor molecules are also preferred because they have the function of improving the electrical junction with the counter electrode. These can be used individually or in combination of two or more.

[0096] The method for forming the electron transport layer and hole blocking layer may be any conventionally known method, and may be either a dry deposition method such as vacuum deposition or a wet deposition method such as solution coating. However, from the viewpoint of being able to level the coated surface, a wet deposition method is preferred. Examples of dry deposition methods include evaporation methods such as vacuum deposition and sputtering. Evaporation may be either physical evaporation (PVD) or chemical evaporation (CVD), but physical evaporation such as vacuum deposition is preferred. Examples of wet deposition methods include inkjet, spray, nozzle printing, spin coating, dip coating, casting, die coating, roll coating, bar coating, and gravure coating.

[0097] The photoelectric conversion element of this embodiment may include a single or two or more auxiliary layers between the first auxiliary layer 103 and the lower electrode 102, separate from the first auxiliary layer 103. Examples of such auxiliary layers include hole injection layers that improve hole injection from the lower electrode 102 to the first auxiliary layer 103. Examples of materials constituting the hole injection layer include phthalocyanine derivatives, starburst amines such as m-MTDATA (4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine), polythiophenes such as PEDOT (poly(3,4-ethylenedioxythiophene)), and polymeric materials such as polyvinylcarbazole derivatives. The thickness of this auxiliary layer may be the same as that of the first auxiliary layer 103.

[0098] In this embodiment, the photoelectric conversion element may include a single or multi-layer auxiliary layer between the third auxiliary layer 107 and the upper electrode 106, separate from the second auxiliary layer 105 and the third auxiliary layer 107. Examples of such auxiliary layers include an electron injection layer that improves electron injection from the upper electrode 106 to the third auxiliary layer 107, and an electron transport layer. Examples of materials constituting the electron injection layer include metals such as cesium, lithium, and strontium, as well as lithium fluoride. The material constituting the electron transport layer may be the same as described above. Furthermore, the thickness of this auxiliary layer may be the same as that of the second auxiliary layer 105.

[0099] In addition to the layers described above, the photoelectric conversion element of this embodiment may also include at least one of the interlayer contact improvement layer and crystallization prevention layer located between those layers.

[0100] The interlayer contact improvement layer serves to reduce damage to the immediately below the upper electrode 106, such as the photoelectric conversion film 110, during film formation of the upper electrode 106. In particular, high-energy particles present in the equipment used for film formation of the upper electrode 106, such as sputtered particles, secondary electrons, Ar particles, and oxygen negative ions in the sputtering method, can collide with the immediately below film, causing alteration and potentially leading to performance degradation such as increased leakage current and decreased sensitivity. One way to prevent this is to provide an interlayer contact improvement layer on top of the immediately below film. Preferably, the interlayer contact improvement layer is made of organic materials such as copper phthalocyanine, NTCDA, PTCDA, [dipyradino[2,3-F:2',3'-H]quinoxaline-2,3,6,7,10,11-hexacarbonitric acid] (HATCN), acetylacetonate complexes, BCP, organometallic compounds, or inorganic materials such as MgAg and MgO. The appropriate thickness of the interlayer contact improvement layer varies depending on the composition of the photoelectric conversion film and the thickness of the electrodes, but it is preferable that it be between 2 nm and 500 nm, particularly from the viewpoint of selecting a material that does not absorb in the visible range or using a thin thickness.

[0101] Figure 2 shows another example of the photoelectric conversion element of this embodiment. The photoelectric conversion element 200 shown in Figure 2 comprises a lower electrode 102 which is a first electrode film, an upper electrode 106 which is a second electrode film, and a photoelectric conversion film 110 located between the lower electrode 102 and the upper electrode 106. The photoelectric conversion element 200 differs from the photoelectric conversion element 100 shown in Figure 1 in that it has a substrate 101 which is normally insulating on the side of the lower electrode 102 opposite to the photoelectric conversion film 110, but otherwise it may be the same as the photoelectric conversion element 100.

[0102] As described above, the photoelectric conversion element of this embodiment is connected to a storage unit, which is a capacitor for storing the generated charge, and a readout unit, which is a transistor circuit for reading the charge, via a connection part made of a conductive material. In addition, the photoelectric conversion element may include a protective structure from the outside air, such as a protective film, a substrate for maintaining strength, and microlenses for focusing light, if necessary.

[0103] The readout unit is provided to read out a signal corresponding to the charge generated in the photoelectric conversion film. The readout unit is composed of, for example, a CCD, CMOS circuit, or TFT circuit, and is preferably shielded from light by a light-shielding layer placed within the insulating layer. The readout circuit is electrically connected to the corresponding electrode via a connector. In addition, to secure the amount of charge necessary for reading, a storage unit composed of a capacitor or the like may be interposed between the electrode and the connector. The connector is embedded in the insulating layer and is a plug or the like for electrically connecting the electrode (for example, a transparent electrode or a counter electrode) and the readout unit. When the component configured in this way is a solid-state image sensor, when light is incident, this light is incident on the photoelectric conversion film, and charge is generated there. Electrons of the generated charge are collected (and stored) by one electrode, and holes are collected by the other electrode. A voltage signal corresponding to the amount is output to the outside of the solid-state image sensor by the readout unit.

[0104] (Image sensor) The image sensor of this embodiment may have the same configuration as a conventional image sensor, as long as it is equipped with the photoelectric conversion elements of this embodiment. For example, the image sensor of this embodiment is equipped with a large number of photoelectric conversion elements of this embodiment arranged in an array. That is, by arranging a large number of photoelectric conversion elements in an array, a solid-state image sensor is constructed that indicates not only the amount of incident light but also the incident position information.

[0105] The image sensor of this embodiment may consist of one photoelectric conversion element of this embodiment, or it may consist of two or more stacked elements. When two or more photoelectric conversion elements of this embodiment are stacked, each photoelectric conversion element may selectively detect light in different wavelength bands and perform photoelectric conversion. For example, when three or more photoelectric conversion elements of this embodiment are stacked, at least one may acquire a green color signal, another at least one may acquire a blue color signal, another at least one may acquire a red color signal, and yet another at least one may acquire an infrared color signal. As a result, the image sensor can acquire multiple types of color signals in a single pixel without using a color filter. In addition, color signals other than those detected by the photoelectric conversion elements of this embodiment may be sensed by a conventionally known device having a silicon photodiode.

[0106] In an image sensor, if a photoelectric conversion element positioned closer to the light source does not block (transmits) the absorption wavelength of another photoelectric conversion element positioned behind it as viewed from the light source, then a device having multiple photoelectric conversion elements or silicon photodiodes may be stacked.

[0107] In an image sensor, from the viewpoint of ease of molding, some of the photoelectric conversion elements may be configured as thin films on the same plane without structural separations between adjacent photoelectric conversion elements.

[0108] The image sensor of this embodiment may further include a substrate. The substrate may be used to manufacture the image sensor by laminating each layer thereon, or to increase the mechanical strength of the image sensor. The type of substrate is not particularly limited, and examples include semiconductor substrates, glass substrates, and plastic substrates.

[0109] (Light sensor) The light sensor of this embodiment only needs to be equipped with the image sensor of this embodiment, and other configurations may be the same as those of a conventional light sensor. This light sensor can receive light with the image sensor of this embodiment and output an electrical signal corresponding to the amount of light received.

[0110] (Solid-state imaging device) The solid-state imaging device of this embodiment may be any device equipped with the image sensor of this embodiment, and other configurations may be the same as those of a conventional solid-state imaging device. The solid-state imaging device of this embodiment may be, for example, a CMOS image sensor, and may be equipped with a pixel section as an imaging area on a semiconductor substrate, and further equipped with a peripheral circuit section having a row scanning section, a horizontal selection section, a column scanning section, and a system control section in the peripheral region or vertically below the pixel section. The pixel section has the image sensor of this embodiment.

[0111] The photoelectric conversion element of this embodiment has the following advantages in addition to those mentioned above, due to the inclusion of compound (1) in the auxiliary layer near the second electrode film. Specifically, the photoelectric conversion element is less prone to aggregation of compound (1), resulting in higher transparency, which in turn reduces visible light scattering (i.e., it exhibits excellent visible light transparency). Furthermore, the photoelectric conversion element of this embodiment is less prone to short circuits and pinhole formation. Moreover, the photoelectric conversion element of this embodiment tends to exhibit a high light-dark ratio, in which case dark current can be further suppressed. In addition, despite the low aggregation of compound (1), the photoelectric conversion element of this embodiment also exhibits excellent hole and electron transport properties, resulting in high photoelectric conversion efficiency. Furthermore, by using compound (1), the photoelectric conversion element of this embodiment also exhibits good heat resistance, improving durability in the manufacturing process and under practical operating conditions. [Examples]

[0112] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The synthesized compounds were further purified by sublimation as needed.

[0113] <Synthesis Example 1> [ka]

[0114] 2.5 g of 1-bromo-2,3,6,7-naphthalenedicarboxylic acid anhydride (1-1-1) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2.0 g of aniline (manufactured by Tokyo Chemical Industry Co., Ltd.) (3 molar equivalents relative to anhydride (1-1-1)) were added to 15 mL of acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and the resulting mixture was stirred at 125°C for 8 hours. After cooling to room temperature, methanol was added, and the precipitated mixture was filtered. After further washing with methanol, pyridine was added and the mixture was stirred for 5 minutes. After stirring, the mixture was filtered and further washed with methanol to obtain compound (1-1-2), which is a white solid.

[0115] [ka]

[0116] Under an argon atmosphere, a mixture of 1.5 g of compound (1-1-2), 0.55 g of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) (1.5 molar equivalents relative to compound (1-1-2)), 11 mL of 2 M aqueous solution of sodium carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.) (7.0 molar equivalents relative to compound (1-1-2)), 20 mL of deoxygenated toluene (manufactured by Tokyo Chemical Industry Co., Ltd.), and 3 mL of deoxygenated dimethylformamide was prepared. Tetrakis(triphenylphosphine)palladium(0) (manufactured by Tokyo Chemical Industry Co., Ltd.) (3 mol%) relative to compound (1-1-2) was added, and the mixture was heated at 100°C for 6 hours. After cooling, the solvent was removed by vacuum distillation, chloroform and water were added, and the organic layer was separated from the aqueous layer. The organic layer was then washed with saturated brine, dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum distillation. Next, the dried material was washed with methanol, and then purified by silica gel chromatography using chloroform / methanol = 50 / 1 as the eluent to obtain compound (1-1). The results of its NMR measurement (measuring instrument product name: JTM-ECS400, manufactured by JEOL Ltd.; the same applies hereafter) are shown below. 1HNMR (500MHz, CDCl3): δ8.90(d,1H),8.84(d,1H),8.65(s,1H),8.97(d,1H),7.59~7.25(m,15H)

[0117] <Synthesis Example 2> [ka]

[0118] A mixture of 1.5 g of compound (1-1-1), 1.0 g of m-cresol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 7 mL of isoquinoline (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred at 180°C for 5 hours. After cooling to room temperature, methanol was added, and the precipitated mixture was filtered. Further washing with methanol yielded compound (1-2-1).

[0119] [ka]

[0120] The mixture obtained by adding 1.0 g of compound (1-2-1) and 0.7 g of 4-aminobenzonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) (2.1 molar equivalents relative to compound (1-2-1)) to 10 mL of acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred at 125°C for 8 hours. After cooling to room temperature, methanol was added and the precipitated mixture was filtered. After further washing with methanol, pyridine was added and the mixture was stirred for 5 minutes. Subsequently, the mixture was filtered and washed with methanol to obtain compound (1-2). The results of FD-MS measurement (measurement instrument product name: JMS-700, manufactured by JEOL Ltd.; the same applies hereafter) and NMR measurement are shown below. FD-MS(m / z):574[M]+ 1 HNMR(500MHz,DMSO-d6):8.78(d,1H),8.65(d,1H),8.05(dm,4H),7.99(s,1H), 7.70(dd,4H),7.39(t,1H),7.14(d,1H),7.02(s,1H),7.00(dm,1H),2.33(s,3H)

[0121] <Synthesis Example 3> 2.0 g of 2,3,6,7-naphthalenedicarboxylic acid anhydride (2-1-1) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1.5 g of aniline (manufactured by Tokyo Chemical Industry Co., Ltd.) (2.2 molar equivalents relative to anhydride (2-1-1)) were added to 15 mL of acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and the resulting mixture was stirred at 125°C for 8 hours. After cooling to room temperature, methanol was added, and the precipitated mixture was filtered. Further washing with methanol, pyridine was added, and the mixture was stirred for 5 minutes. Next, after filtration and washing with methanol, a white solid compound (2-1) was obtained with a content of 98% by mass. The results of its NMR measurement are shown below. 1 HNMR(500MHz,DMSO-d6):8.73(s,4H),7.58~7.45(m,10H) [ka]

[0122] [Fabrication and evaluation of photoelectric conversion elements] In the following examples and comparative examples, photoelectric conversion elements were fabricated using a vapor deposition machine, and current and voltage measurements were performed under atmospheric conditions. The fabricated photoelectric conversion elements were placed in a measurement chamber, and current and voltage measurements were performed. An automatic IV measuring instrument (manufactured by System Giken Co., Ltd.) was used for current and voltage measurements. Light irradiation was performed using a light source device (manufactured by Asahi Spectroscopic Co., Ltd., product name (PVL-3300)) under conditions of an irradiation wavelength of 550 nm and an irradiation full width at half maximum of 20 nm. The light-dark ratio is the value obtained by dividing the current value under light irradiation by the current value in the dark. In addition, the UV-Vis spectrum of the organic thin film was measured using an ultraviolet-visible spectrophotometer (manufactured by Hitachi High-Tech Science Corporation, product name "U-4100").

[0123] (Example 1) A 100nm thick quinacridone (sublimation-refined product from Tokyo Chemical Industry Co., Ltd.) was vacuum-deposited as a photoelectric conversion layer on a transparent conductive ITO glass (ITO manufactured by Geomatec Co., Ltd.). A 100nm thick quinacridone was then vacuum-deposited as a photoelectric conversion layer, and a 25nm thick tris(8-quinolinolato)aluminum (Alq3) was deposited on top of it by resistance heating vacuum deposition as a second auxiliary layer. Next, a 25nm thick compound (2-1) was deposited as a third auxiliary layer by resistance heating vacuum deposition. Then, an aluminum electrode was fabricated on top of the third auxiliary layer by vacuum deposition to a thickness of 100nm to obtain a photoelectric conversion element. For the obtained photoelectric conversion element, a voltage of 4V was applied using ITO and aluminum as electrodes, and the current values ​​in the dark and under light irradiation were measured. The light-dark ratio was calculated from the measurement results. The results are shown in Table 1. Note that the dark current value is shown as a relative value with the value in Comparative Example 1 described later set to 1.

[0124] (Example 2) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that compound (1-1) was used instead of compound (2-1), and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0125] (Example 3) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that compound (1-2) was used instead of compound (2-1), and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0126] (Comparative Example 1) A 100 nm thick layer of quinacridone (sublimation-refined product from Tokyo Chemical Industry Co., Ltd.) was vacuum-deposited as a photoelectric conversion layer on a transparent conductive ITO glass (ITO manufactured by Geomatec Co., Ltd.). A 50 nm thick layer of tris(8-quinolinolato)aluminum (Alq3) was then deposited on top of this layer by resistance heating vacuum deposition. Next, an electrode made of aluminum was fabricated on the auxiliary layer by vacuum deposition to a thickness of 100 nm to obtain a photoelectric conversion element. The obtained crude photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0127] (Comparative Example 2) An attempt was made to fabricate a photoelectric conversion element in the same manner as in Comparative Example 1, except that compound (2-1) was used instead of tris(8-quinolinolato)aluminum. However, the auxiliary layer turned white, so the fabrication of the photoelectric conversion element was stopped. The results are shown in Table 1.

[0128] (Comparative Example 3) A photoelectric conversion element was fabricated in the same manner as in Comparative Example 1, except that compound (1-2) was used instead of tris(8-quinolinolato)aluminum, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0129] [Table 1]

[0130] As shown in Table 1, the photoelectric conversion element of the present invention exhibits a low dark current value and can suppress leakage current in the dark. In particular, some embodiments also showed a high light-dark ratio, indicating that leakage current can be further suppressed. Furthermore, the photoelectric conversion element of the present invention can also prevent whitening of the auxiliary layer. [Industrial applicability]

[0131] The present invention can provide a photoelectric conversion element that can suppress hole or electron leakage, and furthermore, a photoelectric conversion element that excels in required characteristics such as transportability, heat resistance, and visible light transparency. Therefore, the photoelectric conversion element of the present invention has industrial applicability in fields where such characteristics are required. Specifically, it has industrial applicability as a solid-state image sensor in security cameras, in-vehicle cameras, unmanned aerial vehicle cameras, agricultural cameras, industrial cameras, medical cameras such as endoscope cameras, game console cameras, digital still cameras, digital video cameras, mobile phone cameras, and other mobile device cameras; image reading elements in facsimile machines, scanners, and copiers; and light sensors in bio and chemical sensors. Furthermore, it has industrial applicability as an electroluminescent display in television monitors, touch monitors, digital signage, wearable displays, electronic paper, and head-up displays for mobility applications. [Explanation of symbols]

[0132] 100, 200... Photoelectric conversion element, 101... Substrate, 102... Lower electrode, 103... First auxiliary layer, 104... Photoelectric conversion layer, 105... Second auxiliary layer, 106... Upper electrode, 107... Third auxiliary layer, 110... Photoelectric conversion film.

Claims

1. A photoelectric conversion element including a first electrode film, a second electrode film, and a photoelectric conversion film located between the first electrode film and the second electrode film, the photoelectric conversion film includes a photoelectric conversion layer and two auxiliary layers located between the photoelectric conversion layer and the second electrode film, Of the two auxiliary layers, the auxiliary layer closer to the second electrode film has a structure represented by the following formula (1): 【Chemistry 1】 (R １ , R ２ , R ３ , R ４ , R ５ and R ６ are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxy group, a thiol group, an amino group, a cyano group, a carboxy group, a nitro group, and an optionally substituted linear, branched, or cyclic alkyl group, a thioalkyl group, a thioaryl group, an arylsulfonyl group, an aryloxy group, an alkylsulfonyl group, an alkylamino group, an arylamino group, an alkoxy group, an acylamino group, an acyloxy group, an aryl group, a carboxamido group, a carboalkoxy group, a carboaryloxy group, an acyl group, and a monovalent heterocyclic group, and any adjacent R １ , R ２ , R ３ , R ４ , R ５ and R ６ may be part of a fused aliphatic ring or a fused aromatic ring. The fused aliphatic ring and the fused aromatic ring may contain one or more atoms other than carbon. A photoelectric conversion element comprising a compound represented by the formula:

2. 2. The photoelectric conversion element according to claim 1, wherein the compound has no axis of symmetry in its molecular structure.

3. In the formula (1), R １ , R ２ , R ３ and R ４ The photoelectric conversion element according to claim 1 or 2, wherein at least one of the groups is not a hydrogen atom.

4. In the formula (1), R ２ , R ３ and R ４ is a hydrogen atom, and R １ is selected from the group consisting of a halogen atom, a hydroxy group, a thiol group, an amino group, a cyano group, a carboxy group, a nitro group, and an optionally substituted linear, branched, or cyclic alkyl group, a thioalkyl group, a thioaryl group, an arylsulfonyl group, an aryloxy group, an alkylsulfonyl group, an alkylamino group, an arylamino group, an alkoxy group, an acylamino group, an acyloxy group, an aryl group, a carboxamido group, a carboalkoxy group, a carboaryloxy group, an acyl group, and a monovalent heterocyclic group.

5. An imaging device comprising the photoelectric conversion element according to any one of claims 1 to 4.

6. 6. The imaging device according to claim 5, wherein two or more photoelectric conversion elements are stacked.

7. An imaging device comprising a plurality of photoelectric conversion elements according to any one of claims 1 to 4 arranged in an array.

8. An optical sensor comprising the imaging element according to any one of claims 5 to 7.

9. A solid-state imaging device comprising the imaging element according to any one of claims 5 to 7.

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