Compound, organic thin film, photoelectric conversion element, imaging element, optical sensor, and solid-state imaging device

Abstract

A compound represented by formula (1), which has an axis of symmetry in the molecular structure, and in which at least one of R3, R4, R5 and R6 is not a hydrogen atom. (R1 and R2 are hydrogen atoms, and R3 to R6 are each independently a hydrogen atom, a halogen atom, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, or the like. ). # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a compound, an organic thin film, a photoelectric conversion element, an imaging element, a photosensor, and a solid-state imaging device. Background Art

[0002] Conventionally, a technique for photoelectrically converting visible light into an electric signal has been known and is used, for example, in 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 a solid-state imaging device, as the pixel size has been reduced, 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 imide compounds.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-32754

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-512423

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2014-506736 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] For a solid-state imaging device, it is required to achieve both high spectral selectivity and a high S / N ratio. Therefore, it is desired that the solid-state imaging device has a high external quantum efficiency (EQE) and low dark current characteristics. In order to achieve both of these, a method of disposing an electron transport layer and a hole blocking layer, and / or disposing a hole transport layer and an electron blocking layer between a photoelectric conversion unit and an electrode unit is known. Here, in the field of organic electronic devices, an electron transport layer, a hole blocking layer, an electron blocking layer, etc., which are widely used, are disposed at the interface between an electrode or a conductive film and other films in the films constituting the device. These layers respectively function to control the reverse movement of holes or electrons and adjust unnecessary hole or electron leakage. As a material for such a layer, for example, Patent Document 3 discloses an example of using naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTCDA).

[0010] However, in the conventional hole blocking layers and electron blocking layers represented by the substances disclosed in Patent Document 3, there is room for further improvement in suppressing leakage current in the dark.

[0011] An object of the present invention is to provide a novel compound and a photoelectric conversion element material that can suppress leakage current in the dark, are particularly useful for photoelectric conversion element materials, an organic thin film containing the compound, a photoelectric conversion element, an imaging element, a photosensor, and a solid-state imaging device.

[0012] Means for Solving the Problems

[0013] The present invention is as follows. [1]

[0015] A compound represented by the following formula (1), which has a symmetry axis in its molecular structure and at least one of R3, R4, R5, and R6 is not a hydrogen atom.

[0016]

[0017] (R1 and R2 are hydrogen atoms; R3, R4, R5, and R6 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be optionally substituted, and any adjacent R3, R4, R5, and R6 may be optionally a part of a fused aliphatic ring or a fused aromatic ring. The aforementioned fused aliphatic ring and fused aromatic ring may optionally contain one or more atoms other than carbon.) [2]

[0019] The above compound, wherein in the aforementioned formula (1), at least one of R3, R4, R5, and R6 is selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group. [3]

[0021] The above compound, wherein the energy level of the lowest unoccupied orbital of the compound represented by the aforementioned formula (1) obtained by density functional theory is -6.00 eV or more and -3.80 eV or less. [4]

[0023] The above compound, which is a material for a photoelectric conversion element. [5]

[0025] An organic thin film containing the above compound. [6]

[0027] The above organic thin film has a maximum absorption wavelength of an optical absorption band below 450 nm. [7]

[0029] A photoelectric conversion element including a first electrode film, a second electrode film, and a photoelectric conversion film disposed between the first electrode film and the second electrode film,

[0030] The above photoelectric conversion film contains the above material for a photoelectric conversion element. [8]

[0032] A photoelectric conversion element including a first electrode film, a second electrode film, and a photoelectric conversion film disposed between the first electrode film and the second electrode film,

[0033] The above photoelectric conversion film contains the above organic thin film. [9]

[0035] In the above photoelectric conversion element, the above photoelectric conversion film contains a photoelectric conversion layer and an auxiliary layer,

[0036] The above auxiliary layer is formed only of the above organic thin film or is formed of a plurality of films including the above organic thin film.

[10]

[0038] An imaging element including the above photoelectric conversion element.

[11]

[0040] The above imaging element is formed by laminating two or more of the above photoelectric conversion elements.

[12]

[0042] An imaging element formed by arranging a plurality of the above photoelectric conversion elements in an array.

[13]

[0044] An optical sensor including the above imaging element.

[14]

[0046] A solid-state imaging device including the above imaging element.

[0047] Effects of the Invention

[0048] According to the present invention, there can be provided a novel compound and a material for a photoelectric conversion element that are particularly useful for a material for a photoelectric conversion element, an organic thin film containing the compound, a photoelectric conversion element, an imaging element, an optical sensor, and a solid-state imaging device. Brief Description of the Drawings

[0049] Figure 1 FIG. is a cross-sectional schematic view showing an example of the photoelectric conversion element of the present invention. Detailed Description of the Invention

[0050] Hereinafter, embodiments of the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail with reference to the accompanying drawings as needed. However, the present invention is not limited to the following embodiments. The present invention can be variously modified without departing from its gist. It should be noted that in the drawings, the same reference numerals are assigned to the same elements, and repeated descriptions are omitted. In addition, unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

[0051] (Compound)

[0052] The compound of the present embodiment has a symmetry axis in its molecular structure, and at least one of R3, R4, R5, and R6 is not a hydrogen atom. The compound is represented by the following formula (1) (hereinafter, this compound will also be referred to as "compound (1)").

[0053]

[0054] Here, R1 and R2 are hydrogen atoms; R3, R4, R5, and R6 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a thiol group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, and any adjacent R3, R4, R5, and R6 are optionally part of a fused aliphatic ring or a fused aromatic ring. The above-mentioned fused aliphatic ring and fused aromatic ring optionally contain one or more atoms other than carbon.

[0055] This compound (1) can suppress the leakage current in the dark and, in particular, exhibits excellent characteristics as a material for a photoelectric conversion element. Compound (1) tends to exhibit this effect even when compared with a compound having the same structure except for not having a symmetry axis in its molecular structure. The reason is not yet determined, but the present inventors consider it as follows. Here, the reason is not limited to the following content. That is, since compound (1) has two cyano groups in its molecular structure, the energy level of the lowest unoccupied orbital of compound (1) decreases, and the energy level of the highest occupied orbital also decreases. As a result, compound (1) maintains a low energy level of the lowest unoccupied orbital and has a high energy gap. Thereby, compound (1) can suppress the leakage current in the dark and can obtain excellent characteristics as a material for a photoelectric conversion element.

[0056] Here, the "symmetry axis" means: as an operation for comparison with respect to a molecule, a rotation axis that generates a molecule indistinguishable from the original molecule when rotated by 360° / n (n is an integer other than 1). Compound (1) of the present embodiment has such a symmetry axis in its molecular structure.

[0057] A compound having a symmetry axis will be described. The following compound (A) has one symmetry axis represented by a dotted line in its molecular structure. Compounds (B) and (C) have one symmetry axis extending from the front to the inside represented by a black circle in their molecular structures. Compound (D) has two symmetry axes each represented by a dotted line in its molecular structure.

[0058]

[0059] Examples of the halogen atom include a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I).

[0060] The linear alkyl group may be a linear alkyl group having 1 to 12 carbon atoms in the alkyl group, and examples thereof include a methyl group (Me), an ethyl group (Et), a n-propyl group (n-Pr), a n-butyl group (n-Bu), a n-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, a n-decyl group, and a n-dodecyl group.

[0061] The alkyl group as a side chain can be a branched alkyl group with 1 to 12 carbon atoms in the alkyl group. For example, it can be listed as: isopropyl (i-Pr), sec-butyl (s-Bu), tert-butyl (t-Bu), isoamyl, sec-amyl, 3-pentyl, neopentyl, isohexyl, isooctyl, isononyl, isodecyl, and isododecyl. In addition, the straight-chain or branched alkyl group can have substituents. As substituents, for example, it can be listed as: halogen atoms such as fluorine atoms, monovalent groups with aromatic rings such as benzyl, naphthyl, and phenoxy, alkoxy groups, monovalent groups with heteroatoms such as aminoalkyl and thioalkyl, monovalent groups with heterocycles such as pyridyl, hydroxyl group, carboxyl group, amino group, and mercapto group.

[0062] The cyclic alkyl group can be a cyclic alkyl group with 3 to 10 carbon atoms in the alkyl group. For example, it can be listed as: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. In addition, the cyclic alkyl group can have heteroatoms such as nitrogen atoms, oxygen atoms, and sulfur atoms in its ring. As such cyclic alkyl groups, for example, it can be listed as: pyrrolidinyl, oxazolidinyl, pyrazolidinyl, thiazolidinyl, imidazolidinyl, dioxofuranyl, tetrahydrofuranyl, tetrahydrothienyl, piperazinyl, dioxanyl, and morpholinyl. Furthermore, monovalent groups such as hydroxyl group, carboxyl group, amino group, and mercapto group can be bonded to the cyclic alkyl group.

[0063] As thioalkyl (-SR; hereinafter, R represents an alkyl group) and thioaryl (-SAr; hereinafter, Ar represents an aryl group), it can 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. In addition, the thioalkyl group and thioaryl group can also have substituents such as amino group, hydroxyl group, halogen atom, alkoxy group, and thioalkyl group. As such thioalkyl groups and thioaryl groups, for example, it can be listed as: methylthio, ethylthio, phenylthio, tolylthio, aminophenylthio, hydroxyphenylthio, fluorophenylthio, dimethylphenylthio, and methylthiobenzylthio.

[0064] As arylsulfonyl (-SO2-Ar), it can be an arylsulfonyl group with 6 to 16 carbon atoms in the aryl group. For example, it can be listed as: benzenesulfonyl, toluenesulfonyl, dimethylbenzenesulfonyl, mesitylenesulfonyl, octylbenzenesulfonyl, and naphthalenesulfonyl.

[0065] As the aryloxy group (-O-Ar), it can be an aryloxy group in which the number of carbon atoms in the aryl group is 6 to 16. In addition, the aryloxy group may also 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 mercapto group, and an aryloxy group. Examples of such aryloxy groups include: phenoxy group, cyanophenoxy group, methyl cyanophenoxy group, dimethyl cyanophenoxy group, fluorocyanophenoxy group, dicyanophenoxy group, methoxy cyanophenoxy group, tricyanophenoxy group, cyanonaphthyloxy group, dicyanonaphthyloxy group, 2-methylphenoxy group, 3-methylphenoxy group, 4-methylphenoxy group, fluoromethylphenoxy group, dimethylphenoxy group, 3-hydroxyphenoxy group, 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, naphthyloxy group, methoxynaphthyloxy group, fluoronaphthyloxy group, and phenoxyphenoxy group.

[0066] As the alkylsulfonyl group (-SO2-R), it can be an alkylsulfonyl group in which the number of carbon atoms in the alkyl group is 1 to 12. Examples thereof include: methanesulfonyl group, ethanesulfonyl group, and n-butanesulfonyl group.

[0067] As the alkylamino group (here, the alkylamino group is -NHR or -NR2, and the two Rs may be the same or different from each other), it can be an alkylamino group in which the number of carbon atoms in the alkyl group is 1 to 12. Examples thereof 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 isopropyl ethylamino group.

[0068] As the arylamino group (here, the arylamino group is -NHAr or -NAr2, and the two Ars may be the same or different from each other), it can be an arylamino group in which the number of carbon atoms in the aryl group is 6 to 16. Examples thereof include: anilino group, toluidino group, dimethylanilino group, isopropylanilino group, tert-butylanilino group, fluoroanilino group, trifluoromethylanilino group, bis(trifluoromethyl)anilino group, pyridylamino group, methylpyridylamino group, fluoropyridylamino group, pyrimidinylamino group, and biphenylamino group.

[0069] As the alkoxy group (-OR), it can be an alkoxy group having 1 to 12 carbon atoms. For example, it includes: methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-dodecyloxy, isopropoxy, sec-butoxy, tert-butoxy, isopentyloxy, sec-pentyloxy, 3-pentyloxy, neopentyloxy, isohexyloxy, isooctyloxy, isononyloxy, isodecyloxy, and isododecyloxy.

[0070] As the acylamino group (-NH-COR or -NH-COAr), the number of carbon atoms in the alkyl group can be 1 to 12 or the number of carbon atoms in the aryl group can be 6 to 16, and it can also have substituents such as halogen atoms like fluorine atoms, alkoxy groups, and cyano groups. Examples of such acylamino groups include: acetylamino, propionylamino, benzoylamino, methylbenzoylamino, dimethylbenzoylamino, methoxybenzoylamino, cyanobenzoylamino, and bis(trifluoromethyl)benzoylamino.

[0071] As the acyloxy group (-O-COR or -O-COAr), the number of carbon atoms in the alkyl group can be 1 to 12 or the number of carbon atoms in the aryl group can be 6 to 16. The acyloxy group can also have substituents such as halogen atoms like fluorine atoms and cyano groups, and can also have heteroatoms such as nitrogen atoms in the aromatic ring. Examples of such acyloxy groups include: benzoyloxy, methylbenzoyloxy, dimethylbenzoyloxy, cyanobenzoyloxy, fluorobenzoyloxy, bis(trifluoromethyl)benzoyloxy, pyridinecarboxy, and methylpyridinecarboxy.

[0072] As the aryl group (-Ar), it may be an aryl group having 6 to 16 carbon atoms. The aryl group may also 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 have a heteroatom such as a nitrogen atom in the aromatic ring. Examples of such aryl groups include: phenyl, methylphenyl, ethylphenyl, dimethylphenyl, trimethylphenyl, methoxyphenyl, dimethoxyphenyl, trimethoxyphenyl, methoxymethylphenyl, aminophenyl, diaminophenyl, aminomethylphenyl, hydroxyphenyl, dihydroxyphenyl, hydroxymethylphenyl, hydroxyethylphenyl, thiophenyl, methylthiophenyl, dithiophenyl, fluorophenyl, fluoromethylphenyl, trifluoromethylphenyl, perfluorophenyl, fluoro(trifluoromethyl)phenyl, bis(trifluoromethyl)phenyl, cyanophenyl, methylcyanophenyl, dimethylcyanophenyl, dicyanophenyl, methoxycyanophenyl, tricyanophenyl, dicyanophenyl, methylcyanopyridyl, (trifluoromethyl)cyanopyridyl, dimethylcyanopyridyl, dicyanopyridyl, methoxycyanopyridyl, tricyanopyridyl, cyanopyridyl, naphthyl, nitrophenyl, dinitrophenyl, nitrofluorophenyl, methylnaphthyl, ethylnaphthyl, dimethylnaphthyl, trimethylnaphthyl, methoxynaphthyl, dimethoxynaphthyl, trimethoxynaphthyl, aminonaphthyl, diaminonaphthyl, aminomethylnaphthyl, hydroxynaphthyl, dihydroxynaphthyl, hydroxymethylnaphthyl, hydroxyethylnaphthyl, thionaphthyl, methylthionaphthyl, dithionaphthyl, fluoronaphthyl, trifluoromethylnaphthyl, perfluoronaphthyl, bis(trifluoromethyl)naphthyl, biphenyl, cyanobiphenyl.

[0073] As the carboxamido group (here, the carboxamido group is -CO-NH2, -CO-NHR, -CONR2, two Rs may be the same or different from each other, or may be -CONHAr or -CONAr2, and two Ars may be the same or different from each other), it may be a carboxamido group having 1 to 12 carbon atoms in the alkyl group or 6 to 16 carbon atoms in the aryl group. Examples include: dimethylcarboxamido group and diphenylcarboxamido group.

[0074] As the alkoxycarbonyl group or aryloxycarbonyl group (-COOR or -COOAr), it may be an alkoxycarbonyl group having 1 to 12 carbon atoms in the alkyl group or 6 to 16 carbon atoms in the aryl group. Examples include: methoxycarbonyl group and phenoxycarbonyl group.

[0075] The monovalent heterocyclic group may be a monovalent heterocyclic group having 3 to 14 carbon atoms, and examples thereof include: furyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, triazolyl, oxazolyl, dioxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, triazolyl, indolyl, indolinyl, indolizinyl, indazolyl, indoleninyl, benzofuryl, benzothienyl, carbazolyl, dibenzofuryl, dibenzothienyl, pyridyl, diazinyl, oxazinyl, thiazinyl, dioxazinyl, dithienyl, triazinyl, pyrimidinyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, cinnolinyl, phthalazinyl, quinazolinyl, naphthyridinyl, purinyl, pteridinyl, acridinyl, phenanthridinyl, phenanthrolinyl, xanthenyl, phenoxazinyl, thianthrenyl, morpholinyl and phenazinyl.

[0076] In the compound (1) of the present embodiment, at least one of R3, R4, R5 and R6 is not a hydrogen atom. From the viewpoint of more effectively and reliably exerting the effects of the present invention, in the compound (1), it is preferred that at least one of R3 and R4 is not a hydrogen atom, and more preferably R3 is not a hydrogen atom. Further, from the same viewpoint, when at least one of R3 and R4 is not a hydrogen atom, it is preferred that at least one of R5 and R6 is a hydrogen atom, and particularly preferably R5 and R6 are hydrogen atoms. From the same viewpoint, when at least one of R3 and R4 is not a hydrogen atom, it is more preferably that R5 or R6 is a hydrogen atom. From the same viewpoint, when R3 is not a hydrogen atom, it is preferred that at least one of R4, R5 and R6 is a hydrogen atom, and particularly preferably R4, R5 and R6 are hydrogen atoms. From the same viewpoint, when R3 is not a hydrogen atom, it is more preferably that R4 and R5 are hydrogen atoms and R6 is not a hydrogen atom. From the same viewpoint, it is preferred that at least one of R3, R4, R5 and R6 is a hydrogen atom, more preferably R3 is a hydrogen atom, and more preferably R4, R5 and R6 are not hydrogen atoms. Further, from the viewpoints of ease of production and cost, R5 and R6 are preferably the same.

[0077] In addition, when R4, R5 and R6 are hydrogen atoms, R3 is preferably selected from the group consisting of a halogen atom, a hydroxyl group, a thiol group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group and a monovalent heterocyclic group, which are optionally substituted, and more preferably selected from the group consisting of a cyano group and a linear, branched or cyclic alkyl group, which are optionally substituted.

[0078] In the compound (1) of the present embodiment, at least one of R3, R4, R5, and R6 is not a hydrogen atom. From the viewpoint of more effectively and reliably exerting the effects based on the present invention, in the compound (1), it is preferred that at least one of R5 and R6 is not a hydrogen atom, and more preferably R5 is not a hydrogen atom. Further, from the same viewpoint, when at least one of R5 and R6 is not a hydrogen atom, it is preferred that at least one of R3 and R4 is a hydrogen atom, and particularly preferably R3 and R4 are hydrogen atoms. From the same viewpoint, when at least one of R5 and R6 is not a hydrogen atom, it is more preferred that R3 or R4 is a hydrogen atom. From the same viewpoint, when R5 is not a hydrogen atom, it is preferred that at least one of R3, R4, and R6 is a hydrogen atom, and particularly preferably R3, R4, and R6 are hydrogen atoms. From the same viewpoint, when R5 is not a hydrogen atom, it is more preferred that R3 and R6 are hydrogen atoms and R4 is not a hydrogen atom. From the same viewpoint, it is preferred that at least one of R3, R4, R5, and R6 is a hydrogen atom, more preferably R5 is a hydrogen atom, and more preferably none of R3, R4, and R6 is a hydrogen atom. Further, from the viewpoints of ease of manufacture and cost, R3 and R4 are preferably the same.

[0079] In addition, when R3, R4, and R6 are hydrogen atoms, R5 is preferably selected from the group consisting of a halogen atom, a hydroxyl group, a thiol group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which are optionally substituted, and more preferably selected from the group consisting of a cyano group and a linear, branched, or cyclic alkyl group, which are optionally substituted.

[0080] In the compound (1) of the present embodiment, at least one of R3, R4, R5, and R6 is not a hydrogen atom. From the viewpoint of more effectively and reliably exerting the effects described in the present invention, in the compound (1), it is preferred that at least one of R3 and R5 is not a hydrogen atom. Further, when at least one of R3 and R5 is not a hydrogen atom, it is preferred that at least one of R4 and R6 is a hydrogen atom, and more preferably R4 and R6 are hydrogen atoms. Further, from the viewpoints of ease of manufacture and cost, R4 and R6 are preferably the same.

[0081] In addition, when R4 and R6 are hydrogen atoms, at least one of R3 and R5 is preferably selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group and a monovalent heterocyclic group, which are optionally substituted, and more preferably selected from the group consisting of a cyano group and a linear, branched or cyclic alkyl group, which are optionally substituted.

[0082] In the compound (1) of the present embodiment, from the viewpoint of more effectively and reliably exerting the effects of the present invention, at least one of R3, R4, R5, and R6 is preferably selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be substituted. More preferably, at least one of R3 and R4 is selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be substituted. Further, from the same viewpoint, in the compound (1), at least one of R5 and R6 is more preferably selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be substituted. Additionally, from the same viewpoint, in the compound (1), at least one of R3 and R5 is more preferably selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be substituted. Moreover, from the same viewpoint, in the compound (1), R3 or R5 is particularly preferably selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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 carboxamide group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which may be substituted.

[0083] From the viewpoint of more effectively and reliably achieving the effects of the present invention, the energy level of the lowest unoccupied molecular orbital (LUMO: Lowest Unoccupied Molecular Orbital) of the compound (1) in this embodiment obtained by the density functional method is preferably -6.00 eV or more and -3.80 eV or less, more preferably -5.50 eV or more and -3.90 eV or less. For the compound (1) in this embodiment, structural optimization can be performed by molecular simulation using the density functional method (for example, molecular simulation using the quantum chemical calculation program Gaussian manufactured by Gaussian Inc.), and the energy level of the lowest unoccupied molecular orbital of the compound (1) can be obtained. In addition, the energy level of the lowest unoccupied molecular orbital of the compound (1) in this embodiment obtained by the density functional method can be adjusted by changing R3, R4, R5, and R6. From the viewpoint of setting the energy level of the lowest unoccupied molecular orbital within the above range, at least one of R3, R4, R5, and R6 is preferably an electron-withdrawing group.

[0084] The molecular weight of the compound (1) in this embodiment is preferably 300 or more, more preferably 350 or more, and further preferably 400 or more. If the molecular weight is 300 or more, physical property changes caused by molecular thermal motion that may occur during the heating operation or in a high-temperature use environment in the manufacturing process of the organic thin film using the compound (1) can be further suppressed. In addition, especially when forming the compound (1) by vacuum evaporation, the molecular weight of the compound (1) is preferably 1000 or less, more preferably 950 or less, and further preferably 900 or less. If the molecular weight is 1000 or less, the thermal energy required for sublimation when forming the organic thin film of the compound (1) by vacuum evaporation can be suppressed to a lower level. Thus, a good thin film can be formed without thermal degradation of the compound (1). However, when forming a thin film by solution coating, since such problems are less likely to occur, the molecular weight of the compound (1) can be greater than 1000.

[0085] The weight ratio of the weight reduction caused by heating of the compound (1) in this embodiment in an inert gas atmosphere to within 5% of that before heating (hereinafter, sometimes referred to as "5% weight reduction temperature") is preferably 200 °C or more, more preferably 250 °C or more. When the 5% weight reduction temperature is 200 °C or more, physical property changes caused by molecular thermal motion that may occur during the heating operation or in a high-temperature use environment in the manufacturing process of the organic thin film using the compound (1) can be further suppressed. The 5% weight reduction temperature can be measured by differential thermal analysis.

[0086] The compound (1) of the present embodiment can be obtained, for example, by synthesis as described below. In the product (100% by mass) obtained by synthesis, the content rate of the compound (1) is preferably 90% by mass or more, more preferably 93% by mass or more, and still more preferably 97% by mass or more. By making the content rate of the compound (1) 90% by mass or more, it is possible to more effectively and reliably avoid the capture of carriers by impurity levels due to unwanted impurities when the compound (1) is used in a photoelectric conversion element. As a result, the recombination of carriers can be suppressed, and a photoelectric conversion element with more excellent performance can be obtained. For the measurement of the content rate, examples include liquid chromatography, gas chromatography, and elemental analysis, as long as they are known methods.

[0087] Hereinafter, preferred combinations of R3, R4, R5, and R6 are shown. Among them, the compound (1) is not limited to them.

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] Hereinafter, specific examples of the compound (1) are shown. Among them, the compound (1) is not limited to them.

[0095]

[0096] The compound (1) can be synthesized, for example, by the following process.

[0097]

[0098] More specifically, for example, a commercially available compound (α) can be imidized to obtain the compound (1). For example, the imidization can be carried out by the method described in Organic Electronics, 63, 250 (2018). In addition, a compound into which R3 to R6 are introduced can be used for imidization, or R3 to R6 can be introduced after imidization.

[0099] (Material for photoelectric conversion element)

[0100] The compound (1) of the present embodiment can be used as a material for an optoelectronic conversion element. More specifically, it can be used as a material contained in each layer of the optoelectronic conversion element described below. Among them, from the viewpoint of more effectively and reliably exerting the effects of the present invention, the compound (1) is preferably contained in the auxiliary layer, and more preferably contained in at least one of the electron transport layer and the hole blocking layer.

[0101] In addition, the compound (1) of the present embodiment can be directly used as a photosensitive material, or can be mixed with other materials to be used as a photosensitive composition. The content of the compound (1) in the photosensitive composition can be 50% by mass or more based on the total amount of the composition. In addition, its content can be 95% by mass or less, can be 90% by mass or less, or can be 80% by mass or less. The materials other than the compound (1) in the above-mentioned photosensitive composition are not particularly limited as long as they are materials usually contained in photosensitive compositions. Examples of such materials include: the n-type semiconductor material, p-type semiconductor material, and light absorption material described below. These can be used alone or in combination of two or more.

[0102] (organic thin film)

[0103] The organic thin film of the present embodiment contains the compound (1) of the present embodiment or the above-mentioned material for an optoelectronic conversion element. Such an organic thin film can be manufactured by a usual dry film-forming method or wet film-forming method. Specifically, examples include: resistance heating evaporation, electron beam evaporation, sputtering, and molecular layer deposition as vacuum processes, casting, spin coating, dip coating, knife coating, wire bar coating, and spraying as solution processes, printing methods such as inkjet printing, screen printing, offset printing, and letterpress printing, and soft lithography methods such as microcontact printing. Generally, for materials for optoelectronic conversion elements, from the viewpoint of ease of processing, it is desirable to use them in a process of coating the compound in a solution state. However, in the case of an optoelectronic conversion element in which organic thin films are laminated, since there is a risk of the coating solution eroding the underlying film, a dry film-forming method such as resistance heating evaporation is preferred.

[0104] For example, in the dry film-forming method, an organic thin film can be obtained by mixing the material for an optoelectronic conversion element of the present embodiment and other materials corresponding to the use of the optoelectronic conversion element as needed to form a composition, and evaporating the composition onto a substrate or other film under vacuum. In addition, in the wet film-forming method, an organic thin film can be obtained by mixing the optoelectronic conversion film of the present embodiment and other materials corresponding to the use of the optoelectronic conversion element as needed with a solvent to form a liquid composition, coating and printing it on a substrate or other film, and then drying it.

[0105] The organic thin film of the present embodiment may also contain materials other than the compound (1), which is the material for the photoelectric conversion element of the present embodiment. The content of the compound (1) in the organic thin film of the present embodiment is not particularly limited as long as it exhibits the performance required as a material for the photoelectric conversion element. For example, the content of the compound (1) may be 50% by mass or more with respect to the total amount of the organic thin film. From the viewpoint of more effectively and reliably exerting the effects produced by the present invention, it is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. The upper limit of the content of the compound (1) may be 100% by mass. When the organic thin film of the present embodiment contains materials other than the compound (1), the material is not particularly limited as long as it is generally used as a material for the photoelectric conversion element. Examples of such materials include: the n-type semiconductor material, p-type semiconductor material, and light absorption material described later, and molybdenum oxide, alkali metals, and alkali metal compounds called doping materials. These can be used alone or in combination of two or more kinds.

[0106] The thickness of the organic thin film depends on the resistance value / charge mobility of each substance and is not particularly limited, but is usually 0.5 nm or more and 5000 nm or less, can be 1 nm or more and 1000 nm or less, or can be 5 nm or more and 500 nm or less.

[0107] From the viewpoint of more effectively and reliably exerting the effects described in the present invention, the organic thin film of the present embodiment preferably has a maximum absorption wavelength of the light absorption band at 450 nm or less.

[0108] (Photoelectric conversion element)

[0109] The photoelectric conversion element of the present embodiment refers to an element that generates charges corresponding to the incident light amount, passes through a capacitor (hereinafter also referred to as an "accumulation unit") for accumulating the generated charges, a transistor circuit for reading (hereinafter also referred to as a "reading unit"), and outputs to the outside of the photoelectric conversion element. Here, in the photoelectric conversion element, a photoelectric conversion film that absorbs at least a part of the incident light is disposed between a pair of opposing electrodes, and light is incident on the photoelectric conversion element from above the electrodes. In addition, the photoelectric conversion film is a photosensitive thin film containing a material that absorbs at least a part of the incident light in the infrared region, and holes and electrons are generated as a result of the incident light. In addition, the photoelectric conversion element of the present embodiment may also have a photoelectric conversion element (hereinafter also referred to as an "infrared photoelectric conversion element") that generates charges corresponding to the incident light amount in the infrared region. Here, in the infrared photoelectric conversion element, a photoelectric conversion film that absorbs infrared rays (hereinafter also referred to as an "infrared photoelectric conversion film") is disposed between a pair of opposing electrodes, and light is incident on the infrared photoelectric conversion element from above the electrodes. In addition, the infrared photoelectric conversion film is a photosensitive thin film containing a material (hereinafter referred to as an "infrared absorption material") that absorbs at least a part of the incident light in the infrared region, and holes and electrons are generated as a result of the incident light.

[0110] Appropriately refer to Figure 1 The photoelectric conversion element of the present embodiment will be described. The photoelectric conversion element 100 includes a lower electrode 102 as a first electrode film, an upper electrode 106 as a second electrode film, and a photoelectric conversion film 110 disposed between the lower electrode 102 and the upper electrode 106. The photoelectric conversion element 100 may include a substrate 101 that is generally insulating on the side opposite to the photoelectric conversion film 110 of the upper electrode 106.

[0111] When the photoelectric conversion film 110 has hole transportability or electron transportability, the lower electrode 102 and the upper electrode 106 function as follows: extracting holes from the photoelectric conversion film 110 and trapping them, or extracting electrons and discharging them. The material that can be used as these electrodes is not particularly limited as long as it has a certain degree of conductivity, and it is preferably selected considering the adhesion, electron affinity, ionization potential, and stability of the adjacent photoelectric conversion film 110. Examples of the material that can be used as an electrode include conductive metal oxides such as tin oxide (NESA), indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel, and tungsten; inorganic conductive substances such as copper iodide and copper sulfide; conductive polymers such as polythiophene, polypyrrole, and polyaniline; and carbon. These materials can be used alone or in combination of multiple kinds.

[0112] The lower electrode 102 serving as the first electrode film includes a conductive film having light transmissibility, for example, including ITO (indium tin oxide). The material constituting the lower electrode 102 is not limited to ITO. For example, it may include: tin oxide (SnO2) - based materials doped with dopants, and zinc oxide - based materials doped with dopants in zinc oxide (ZnO). As the zinc oxide - based materials, for example, it may include: aluminum - doped zinc oxide (AZO) with aluminum (Al) added as a dopant, gallium - doped zinc oxide (GZO) with gallium (Ga) added, and indium - doped zinc oxide (IZO) with indium (In) added. Or as the material constituting the lower electrode 102, for example, it may include: CuI, InSbO4, ZnMgO, CuInO2, MgIN2O4, CdO, and ZnSnO3. The thickness of the lower electrode 102 can be, for example, 5 nm or more and 3000 nm or less, can be 5 nm or more and 500 nm or less, or can be 10 nm or more and 300 nm or less.

[0113] The upper electrode 106 serving as the second electrode film can be composed of a conductive film having the same light transmissibility as the lower electrode 102. In addition, in a solid - state imaging device using a solid - state imaging element as a single pixel, the upper electrode 106 can be separated according to each pixel or can be formed as a common electrode for each pixel. The thickness of the upper electrode 106 is, for example, 5 nm or more and 3000 nm or less, can be 5 nm or more and 500 nm or less, or can be 10 nm or more and 300 nm or less.

[0114] The conductivity of the material for the electrodes such as the first electrode film and the second electrode film is not particularly limited as long as it does not overly interfere with the light reception of the photoelectric conversion element. However, from the viewpoints of the signal intensity and power consumption of the photoelectric conversion element, it is preferably as high as possible. For example, as a transparent electrode, if it is an ITO film having a conductivity with a sheet resistance value of 300 Ω / □ or less, it can fully function as an electrode. However, commercially available substrates with ITO films having a conductivity of about several Ω / □ (for example, 5 - 9 Ω / □) can also be obtained, and substrates with such high conductivity are desired.

[0115] When using an ITO film, the thickness of the electrode can be arbitrarily selected considering conductivity, but it is usually 5 nm or more and 3000 nm or less, preferably 10 nm or more and 300 nm or less. As methods for forming films such as ITO, there can be mentioned: conventionally known evaporation methods, electron beam methods, sputtering methods, chemical reaction methods, and coating methods. The ITO film provided on the substrate can be subjected to UV - ozone treatment or plasma treatment as needed.

[0116] In addition, when stacking a plurality of photoelectric conversion films with different detected wavelengths, the electrode film (which is the electrode film other than the above-mentioned pair of electrodes) used between the respective photoelectric conversion films must allow light with wavelengths other than the light detected by each photoelectric conversion film to pass through. From this viewpoint, it is preferable to use a material that allows 90% or more of the incident light to pass through for this electrode film, and more preferably a material that allows 95% or more of the light to pass through.

[0117] In addition, when a visible light photoelectric conversion unit that senses infrared light or light in a different visible light region is further provided below the photoelectric conversion element in the present embodiment, the electrodes used in the above-mentioned photoelectric conversion element preferably have a transmittance of 90% or more for the visible light and infrared light, and more preferably 95% or more.

[0118] As an electrode material that satisfies such conditions, a transparent conductive oxide (TCO; Transparent Conducting Oxide) with high transmittance and low resistance value for visible light and infrared light is preferable. Although a metal thin film such as Au can be used as an electrode, if the transmittance is set to 90% or more, the resistance value will increase extremely. Therefore, TCO is preferably used as the electrode. As TCO, ITO, IZO, AZO, FTO, SnO2, TiO2, and ZnO2 are particularly preferable.

[0119] The method for forming the electrode is not particularly limited, and it can be appropriately selected in consideration of the suitability with the electrode material. When using a transparent electrode, as its forming method, specific examples include wet methods such as printing methods and coating methods, physical methods such as vacuum evaporation, sputtering, and ion plating, and chemical methods such as CVD and plasma CVD methods. In addition, when the electrode material is a transparent conductive metal oxide such as ITO, as its forming method, for example, electron beam method, sputtering method, resistance heating evaporation method, chemical reaction method (such as sol-gel method, etc.), and a method of coating a dispersion of the metal oxide can be cited. Furthermore, UV-ozone treatment and plasma treatment can also be performed on a transparent conductive metal oxide film such as ITO.

[0120] The photoelectric conversion film 110 may contain the material for the photoelectric conversion element of the present embodiment, or may contain the above-mentioned organic thin film. More specifically, for example, the photoelectric conversion film 110 includes a photoelectric conversion layer 104, a first auxiliary layer 103 on the lower electrode film 102 side of the photoelectric conversion layer 104, and a second auxiliary layer 105 on the upper electrode film 106 side of the photoelectric conversion layer 104. It should be noted that Figure 1The photoelectric conversion film 110 shown includes a first auxiliary layer 103 and a second auxiliary layer 105. However, the photoelectric conversion film may also include only any one of these auxiliary layers, or may not include any auxiliary layer and only include the photoelectric conversion layer 104. When the photoelectric conversion film does not include an auxiliary layer, the photoelectric conversion layer 104 is the above-mentioned organic thin film. When the photoelectric conversion film includes an auxiliary layer, at least one of the photoelectric conversion layer 104 and the auxiliary layer is the above-mentioned organic thin film. However, from the viewpoint of more effectively and reliably achieving the effects produced by the present invention, the auxiliary layer is preferably the above-mentioned organic thin film containing the material for the photoelectric conversion element of the present embodiment.

[0121] The photoelectric conversion layer 104 may be an organic semiconductor film commonly used as a photoelectric conversion layer, or may be the above-mentioned organic thin film. In addition, in the photoelectric conversion layer 110, these organic semiconductor films and organic thin films may be one layer or multiple layers. When it is one layer, a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film thereof (hereinafter may be "bulk heterojunction structure") is used. On the other hand, when it is multiple layers, the number of layers may be about 2 to 10 layers, and may be a structure formed by laminating any one of a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film thereof (hereinafter may be "bulk heterojunction structure"), and a buffer layer may be inserted between the layers.

[0122] The photoelectric conversion layer 104 of the present embodiment may contain the material for the photoelectric conversion element of the present embodiment, may not contain it, or may contain materials other than the material for the photoelectric conversion element of the present embodiment. Among them, when the photoelectric conversion layer 104 contains at least one of an organic p-type semiconductor, an organic n-type semiconductor, and a light absorption material, it is preferable because the incident light energy of a desired wavelength can be converted into an electrical signal more efficiently. Among them, for the light absorption material, if it is an organic p-type semiconductor, it is easy to supply electrons (that is, the ionization potential is small), or if it is an organic n-type semiconductor, it is easy to accept electrons (that is, the electron affinity is large), and it is preferable because the incident light energy can be converted into an electrical signal more efficiently. Here, the ionization potential (HOMO energy level) is a value measured by photoelectron yield spectroscopy or photoelectron spectroscopy. In addition, the electron affinity (LUMO energy level) is a value calculated from the longest wavelength absorption end of the near-infrared light absorption spectrum, subtracted from the above-mentioned HOMO energy level, or a value measured by inverse photoelectron spectroscopy.

[0123] When using an organic semiconductor film, the film can be a single layer or two or more layers. The organic semiconductor film can be an organic p-type semiconductor film, an organic n-type semiconductor film, a light absorption material film, or a mixed film thereof (bulk heterojunction structure). In particular, the organic semiconductor film preferably has a bulk heterojunction bonding structure layer. In such a case, by making the photoelectric conversion film contain a bulk heterojunction bonding structure, 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.

[0124] The thickness of the photoelectric conversion layer 104 can 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.

[0125] Hereinafter, the organic semiconductor will be described in detail.

[0126] The organic p-type semiconductor is a donor-type organic semiconductor (hereinafter also referred to as "donor-type organic compound"), and mainly refers to an organic compound having a property of easily supplying electrons, represented by a hole-transporting organic compound. More specifically, it is an organic compound having a smaller ionization potential when two organic materials are brought into contact and used. Therefore, as the donor-type organic compound, any organic compound can be used as long as it is an organic compound having an electron-donating property.

[0127] Examples of such donor-type 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 (such as naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, and fluoranthene derivatives), and metal complexes having a nitrogen-containing heterocyclic compound as a ligand. It should be noted that these are not limited, and as described above, any organic compound can be used as the donor-type organic semiconductor as long as its ionization potential is smaller than that of the organic compound used as the acceptor-type organic compound.

[0128] The organic n-type semiconductor refers to an acceptor-type organic semiconductor (hereinafter also referred to as "acceptor-type organic compound"), and mainly refers to an organic compound having a property of easily accepting electrons, represented by an electron-transporting organic compound. More specifically, it is an organic compound having a larger electron affinity when two organic compounds are brought into contact and used. Therefore, as the acceptor-type organic compound, any organic compound can be used as long as it is an organic compound having an electron-accepting property.

[0129] Examples of such acceptor organic compounds include: fused aromatic carbocyclic compounds (e.g., naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives, fullerene derivatives), 5- to 7-membered heterocyclic compounds containing a nitrogen atom, an oxygen atom, or a sulfur atom (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazopyridazine, triazopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyrrolidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, and tribenzazepine), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and metal complexes having a nitrogen-containing heterocyclic compound as a ligand. It should be noted that it is not limited to these. As described above, as long as it is an organic compound having a higher electron affinity than the organic compound used as the donor organic compound, it can be used as an acceptor organic semiconductor.

[0130] The light absorption material is a compound having a maximum light absorption wavelength in the visible light region, particularly in the range of 450 nm or more and 650 nm or less. It is desirable that the absorption intensity of the light absorption material at the maximum light absorption wavelength is greater than the absorption intensity of the donor organic compound or the acceptor organic compound at the maximum light absorption wavelength. By having such an absorption intensity, the incident light can be selectively absorbed at the maximum light absorption wavelength of the light absorption material. After the incident light is absorbed by the light absorption material and photons are converted into excitons, exciton separation occurs at the interface between the donor organic compound and the acceptor organic compound, whereby carriers of holes and electrons can be efficiently generated.

[0131] As such a light-absorbing material, compounds generally referred to as pigments 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, azamethine derivatives, arylene derivatives, azo derivatives, azomethine derivatives, metallocene derivatives, fulgide derivatives, phenazine derivatives, phenothiazine derivatives, polyene derivatives, acridine derivatives, acridone 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 derivatives, thiazine derivatives, quinone derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, indigo or thioindigo derivatives, pyrrole derivatives, pyridine derivatives, dipyrromethene derivatives, indole derivatives, diketopyrrolopyrrole derivatives, coumarin derivatives, fluorene derivatives, fluorenone derivatives, fluoranthene 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, thiazole derivatives, oxadiazole derivatives, thiophene derivatives, selenophene derivatives, silole derivatives, germole derivatives, stilbene derivatives, phenylene vinylene derivatives, pentacene derivatives, rubrene derivatives, thienothiophene derivatives, benzodithiophene derivatives, xanthene-xanthene derivatives, and fullerene derivatives can be cited. It should be noted that it is not limited to these. As described above, as long as it is a compound having an absorption intensity greater than the absorption intensity of the donor organic compound or the acceptor organic compound at the maximum absorption wavelength, it can be used as a light-absorbing material. In addition, the light-absorbing material may also serve as a donor organic compound or an acceptor organic compound.

[0132] The first auxiliary layer 103 includes at least one of, for example, a hole blocking layer and an electron transport layer. When the first auxiliary layer 103 includes both of them, the electron transport layer and the hole blocking layer are usually stacked in this order from the side of the photoelectric conversion layer 104. The electron transport layer functions to transport electrons generated by the photoelectric conversion layer 104 to the first electrode 102 and to block the movement of holes from the first electrode 102 at the electron transport end to the photoelectric conversion layer 104. The hole blocking layer functions to prevent the movement of holes from the first electrode 102 to the photoelectric conversion layer 104, prevent recombination in the photoelectric conversion layer 104, reduce dark current, reduce noise, and expand the dynamic range. In addition, one layer can have the functions of both a hole blocking layer and an electron transport layer.

[0133] The second auxiliary layer 105 includes at least one of, for example, an electron blocking layer and a hole transport layer. When the second auxiliary layer 105 includes both of them, the hole transport layer and the electron blocking layer are usually stacked in this order from the side of the photoelectric conversion layer 104. The hole transport layer functions to transport generated holes from the photoelectric conversion layer 104 to the second electrode 106 and to block the movement of electrons from the second electrode 106 at the hole transport end to the photoelectric conversion layer 104. The electron blocking layer functions to prevent the movement of electrons from the second electrode 106 to the photoelectric conversion layer 104, prevent recombination in the photoelectric conversion layer 104, reduce dark current, reduce noise, and expand the dynamic range. In addition, one layer can have the functions of both an electron blocking layer and a hole transport layer.

[0134] The material for the photoelectric conversion element of the present embodiment may also be included in any one of these first auxiliary layer 103 and second auxiliary layer 105, and is preferably included in the first auxiliary layer 103. In the photoelectric conversion element of the present embodiment, among these first auxiliary layer 103 and second auxiliary layer 105, it is preferable that the first auxiliary layer 103 contains the above-mentioned organic thin film. In addition, the material for the photoelectric conversion element of the present embodiment is more preferably included in at least one of the hole blocking layer and the electron transport layer in the first auxiliary layer 103. In the photoelectric conversion element of the present embodiment, it is preferable that at least one of the hole blocking layer and the electron transport layer is the above-mentioned organic thin film. Thereby, the effects produced by the present invention can be exerted more effectively and reliably.

[0135] Hereinafter, materials other than the material for the photoelectric conversion element of the present embodiment that can be included in each layer of the auxiliary layer will be described.

[0136] As the material for the hole transport layer, there is no particular limitation as long as it is known as a hole transport layer in a photoelectric conversion element such as a solid-state imaging element. For example, polyaniline and its doping materials, and cyanide compounds described in International Publication No. 2006 / 019270 can be cited.

[0137] As materials constituting the hole transport layer, more specifically, for example, the following can be cited: selenium, iodides such as copper iodide (CuI), cobalt complexes such as layered cobalt oxides, CuSCN, molybdenum oxides (such as MoO3, etc.), nickel oxides (such as NiO, etc.), 4CuBr·3S(C4H9), and organic hole transport materials. Among them, as iodides, for example, copper iodide (CuI) can be cited. As layered cobalt oxides, for example, A x CoO2 (where A represents Li, Na, K, Ca, Sr, or Ba, and 0 ≤ X ≤ 1). In addition, as organic hole transport materials, for example, the following can be cited: polythiophene derivatives such as poly-3-hexylthiophene (P3HT), poly(3,4-ethylenedioxythiophene) (PEDOT; for example, the trade name "Baytron P" manufactured by Starck V-tec), fluorene derivatives such as 2,2',7,7'-tetra-(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, as materials for the hole transport layer, for example, the following can be cited: 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).

[0138] In addition, if the hole transport layer has a LUMO energy level higher than that of the photoelectric conversion film, it can be given an electron blocking function with a rectifying effect that suppresses the movement of electrons generated in the photoelectric conversion film toward the electrode side, and thus is preferred. Such a hole transport layer is also called an electron blocking layer.

[0139] Among the materials constituting the electron blocking layer, as low-molecular organic compounds, for example, there can be cited: aromatic diamine compounds such as N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) and 4,4'-bis[N-(naphthyl)-N-phenylamino]biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivatives, pyrazoline derivatives, tetrahydroimidazole, polyarylalkane, butadiene, 4,4',4''-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA), porphyrin, copper tetraphenylporphyrin, phthalocyanine, copper phthalocyanine, and porphyrin compounds such as titanium phthalocyanine oxide, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, and silazane derivatives. In addition, as high-molecular organic compounds, for example, there can be cited: polymers of phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, methylpyridine, thiophene, acetylene, diacetylene, etc. and their derivatives. Even if it is not an electron-donating compound, as long as it is a compound having sufficient hole-transporting properties, it can be used as a material for constituting the electron blocking layer. Further, among the materials constituting the electron blocking layer, as inorganic compounds, for example, there can be cited: metal oxides such as calcium oxide, chromium oxide, copper chromium oxide, manganese oxide, cobalt oxide, nickel oxide, copper oxide, copper gallium oxide, copper strontium oxide, niobium oxide, molybdenum oxide, indium copper oxide, indium silver oxide, and indium oxide, selenium, tellurium, and antimony sulfide. These can be used alone or in combination of two or more.

[0140] From the viewpoint of suppressing dark current and preventing a decrease in photoelectric conversion efficiency, the thickness of the hole-transporting layer is preferably 10 nm or more and 300 nm or less, more preferably 30 nm or more and 250 nm or less, and further preferably 50 nm or more and 200 nm or less.

[0141] As a method for forming the hole-transporting layer, it can be a conventionally known method, and can be either a dry film-forming method such as a vacuum evaporation method or a wet film-forming method such as a solution coating method. However, from the viewpoint of leveling the coating surface, a wet film-forming method is preferred. As the dry film-forming method, for example, there can be cited: evaporation methods such as a vacuum evaporation method and a sputtering method. Evaporation can be either physical vapor deposition (PVD) or chemical vapor deposition (CVD), but physical vapor deposition such as vacuum evaporation is preferred. As the wet film-forming method, for example, there can be cited: an inkjet method, a spray method, a nozzle printing method, a spin coating method, a dip coating method, a casting method, a die coating method, a roll coating method, a bar coating method, and an intaglio coating method.

[0142] As a material constituting the electron transport layer, there is no particular limitation as long as it is known as an electron transport layer in a photoelectric conversion element such as a solid-state imaging device. For example, it can be exemplified by: octaazaporphyrin, and perfluorinated bodies of p-type semiconductors (such as perfluoropentacene, perfluorophthalocyanine, etc.), fullerenes, fullerene derivatives (such as [6,6]-phenyl-C61-butyric acid methyl ester; PCBM, etc.), perylene, indenoindene and indenoindene derivatives and other organic compounds, titanium oxide (TiO2, etc.), nickel oxide (NiO), tin oxide (SnO2), tungsten oxides (WO2, WO3, W2O3, etc.), zinc oxide (ZnO), niobium oxide (Nb2O5, etc.), tantalum oxide (Ta2O5, etc.), yttrium oxide (Y2O3, etc.) and strontium titanate (SrTiO3, etc.) and other inorganic oxides. The electron transport layer can be porous or dense. When they are laminated, it is preferable to laminate and dispose a porous electron transport layer and a dense electron transport layer in this order from the side of the photoelectric conversion film.

[0143] In addition, if the electron transport layer has a HOMO energy level lower than that of the photoelectric conversion film, a hole blocking function having a rectifying effect of suppressing the movement of holes generated in the photoelectric conversion film toward the counter electrode side can be imparted, and thus it is preferable. Such an electron transport layer is also called a hole blocking layer.

[0144] As a material constituting the hole blocking layer, for example, it can be exemplified by: oxadiazole derivatives such as 1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)benzene (OXD-7), anthraquinone dimethane derivatives, diphenylquinone derivatives, bathocuproine, bathophenanthroline and their derivatives, triazine compounds, triazole compounds, tris(8-hydroxyquinoline)aluminum complex, bis(4-methyl-8-quinoline)aluminum complex, silafluorene compounds, porphyrin-based compounds, styrene-based compounds such as DCM (4-dicyanomethylene-2-methyl-6-(4-(dimethylaminostyryl))-4H-pyran), naphthalene tetracarboxylic dianhydride (NTCDA), naphthalene tetracarboxylic diimide, perylene tetracarboxylic dianhydride (PTCDA), perylene tetracarboxylic diimide and other n-type semiconductor materials, n-type inorganic oxides such as titanium oxide, zinc oxide and gallium oxide, and alkali metal fluorides such as lithium fluoride, sodium fluoride and cesium fluoride. Furthermore, those obtained by doping an alkali metal compound into an organic semiconductor molecule have a function of improving the electrical junction with the counter electrode, and thus are preferable. These can be used alone or in combination of two or more.

[0145] From the viewpoint of suppressing dark current and preventing a decrease in photoelectric conversion efficiency, the thickness of the electron transport layer is preferably 10 nm or more and 300 nm or less, more preferably 30 nm or more and 250 nm or less, and still more preferably 50 nm or more and 200 nm or less.

[0146] As a method for forming the electron transport layer, any of the conventionally known methods, such as a dry film-forming method like vacuum evaporation and a wet film-forming method like solution coating, can be used. However, from the viewpoint of leveling the coating surface, a wet film-forming method is preferred. As the dry film-forming method, for example, evaporation methods such as vacuum evaporation and sputtering can be cited. Evaporation can be either physical vapor deposition (PVD) or chemical vapor deposition (CVD), but physical vapor deposition such as vacuum evaporation is preferred. As the wet film-forming method, for example, inkjet method, spray method, nozzle printing method, spin coating method, dip coating method, casting method, die coating method, roll coating method, bar coating method, and gravure coating method can be cited.

[0147] In addition to the above-described layers, the photoelectric conversion element of the present embodiment may include at least one of an interlayer contact improvement layer and a crystallization prevention layer located between these layers.

[0148] The interlayer contact improvement layer functions to reduce the damage caused to the closest lower film, such as the photoelectric conversion film 110, during the film formation of the upper electrode 106. In particular, high-energy particles present in the apparatus used for the film formation of the upper electrode 106, for example, in the case of sputtering, sputtering particles, secondary electrons, Ar particles, oxygen anions, etc. collide with the closest lower film and deteriorate, sometimes resulting in performance degradation such as an increase in leakage current and a decrease in sensitivity. As one method of preventing this, it is preferable to provide an interlayer contact improvement layer on the upper layer of the closest lower film. As the material of the interlayer contact improvement layer, organic materials such as copper phthalocyanine, NTCDA, PTCDA, [dipyrazino[2,3-f:2’,3’-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile] (HATCN), acetylacetonate complex, BCP, organic-metal compounds, or inorganic materials such as MgAg and MgO are preferably used. The thickness of the interlayer contact improvement layer varies within an appropriate range depending on the composition of the photoelectric conversion film, the thickness of the electrode film, etc. However, particularly from the viewpoint of selecting a material that does not have absorption in the visible light region or using it with a relatively thin thickness, it is preferably 2 nm or more and 500 nm or less.

[0149] As described above, on the photoelectric conversion element of the present embodiment, a capacitor for accumulating the generated charges, i.e., an accumulation part, and a transistor circuit for reading out, i.e., a readout part, are connected via a connection part formed of a conductive material. In addition, as needed, the photoelectric conversion element includes a protective structure such as a protective film to avoid external air, a substrate for maintaining strength, and a microlens for condensing light.

[0150] A readout unit is provided to read out a signal corresponding to the charge generated in the photoelectric conversion film. The readout unit is constituted by, for example, a CCD, a CMOS circuit, a TFT circuit, etc., and is preferably shielded from light by a light-shielding layer disposed in the insulating layer. The readout circuit is electrically connected to the corresponding electrode via a connection portion. It should be noted that, in order to ensure the amount of charge required during readout, an accumulation portion constituted by a capacitor or the like may be interposed between the electrode and the connection portion. The connection portion is buried in the insulating layer and is a plug or the like for electrically connecting an electrode (for example, a transparent electrode or a counter electrode) to the readout unit. When the component configured in this way is a solid-state imaging device, if light is incident, the light is incident on the photoelectric conversion film, and charge is generated there. Electrons among the generated charges are trapped (and accumulated) by one electrode, and holes are trapped by the other electrode. A voltage signal corresponding to this amount is output to the outside of the solid-state imaging device through the readout unit.

[0151] (Imaging element)

[0152] If the imaging element of the present embodiment includes the photoelectric conversion element of the present embodiment, the other configurations may be the same as those of conventional imaging elements. For example, a plurality of the photoelectric conversion elements of the present embodiment are arranged in an array in the imaging element of the present embodiment. That is, by arranging a plurality of photoelectric conversion elements in an array, a solid-state imaging device that also shows the incident position information in addition to the incident light amount is constituted.

[0153] The imaging element of the present embodiment may include one photoelectric conversion element of the present embodiment, or two or more may be stacked. In the case where two or more photoelectric conversion elements of the present embodiment are stacked, each photoelectric conversion element may selectively detect light in mutually different wavelength bands and perform photoelectric conversion. For example, in the case where three or more photoelectric conversion elements of the present embodiment are stacked, at least one may obtain a green signal, at least one of the others may obtain a blue signal, at least one of the others may obtain a red signal, and at least one of the others may obtain a color signal of infrared light. Thus, the imaging element can obtain a variety of color signals in one pixel without using a color filter. In addition, color signals other than the color signals detected by the photoelectric conversion element of the present embodiment may also be sensed by a device having a conventionally known silicon photodiode.

[0154] In the imaging element, when the photoelectric conversion element disposed closer to the light source does not shield (i.e., transmits) the absorption wavelength of another photoelectric conversion element disposed behind it when viewed from the light source side, a device having a plurality of photoelectric conversion elements and silicon photodiodes may also be stacked.

[0155] In the imaging element, from the viewpoint of ease of molding, a part of the photoelectric conversion element may be configured as a thin film on the same plane without structural partitioning between adjacent photoelectric conversion elements.

[0156] The imaging element of this embodiment may further include a substrate. The substrate is used to stack various layers thereon to manufacture the imaging element, or to improve the mechanical strength of the imaging element. There is no particular limitation on the type of the substrate. For example, a semiconductor substrate, a glass substrate, and a plastic substrate can be cited.

[0157] (Optical sensor)

[0158] The optical sensor of this embodiment only needs to include the imaging element of this embodiment, and the other components can be the same as those of the conventional optical sensor. This optical sensor can receive light in the imaging element of this embodiment and output an electrical signal corresponding to the amount of received light of the light.

[0159] (Solid-state imaging device)

[0160] The solid-state imaging device of this embodiment only needs to include the imaging element of this embodiment, and the other components can be the same as those of the conventional solid-state imaging device. The solid-state imaging device of this embodiment can be, for example, a CMOS image sensor, and can also have a pixel portion as an imaging area on a semiconductor substrate. Further, a peripheral circuit portion can be provided in a peripheral area or directly below the pixel portion. The peripheral circuit portion has a row scanning portion, a horizontal selection portion, a column scanning portion, and a system control portion. The above pixel portion includes the imaging element of this embodiment.

[0161] The photoelectric conversion element of this embodiment has the following advantages by using the material for the photoelectric conversion element of this embodiment. That is, it is difficult for the photoelectric conversion element of this embodiment to have a short circuit or generate pinholes, so the dark current value is reduced. As a result, the photoelectric conversion element of this embodiment has excellent leakage prevention performance (especially in the dark). Further, the photoelectric conversion element of this embodiment tends to easily exhibit a high contrast ratio, and in this case, it has more excellent leakage prevention performance. In addition, although the material for the photoelectric conversion element is not likely to aggregate in the photoelectric conversion element of this embodiment, its hole and electron transport properties are still excellent, so the photoelectric conversion efficiency becomes high. Further, the photoelectric conversion element of this embodiment has good heat resistance by using the material for the photoelectric conversion element of this embodiment, and the durability in the manufacturing process and practical environment is improved.

[0162] Examples

[0163] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. It should be noted that the synthesized compound can be further purified by sublimation as needed.

[0164] (Synthesis Example 1)

[0165]

[0166] To 90 mL of m-cresol (manufactured by Tokyo Chemical Industry Co., Ltd.), 6.0 g of 1,4,5,8-naphthalenetetracarboxylic dianhydride (1) (manufactured by Tokyo Chemical Industry Co., Ltd.), 6.1 g of isoquinoline (manufactured by Tokyo Chemical Industry Co., Ltd.) (2.1 molar equivalents relative to 1,4,5,8-naphthalenetetracarboxylic dianhydride (1)), and 8.0 g of 4-aminophthalonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) (2.5 molar equivalents relative to 1,4,5,8-naphthalenetetracarboxylic dianhydride (1)) were added, and the resulting mixture was stirred at 180 °C for 8 hours. Thereafter, it was cooled to room temperature, methanol was added thereto, and the precipitate was filtered. Further, after washing with methanol, an aqueous potassium carbonate solution was added and stirred for 5 minutes. Then, after filtration, it was washed with water and methanol, and purified by sublimation to obtain a compound (2) presenting a white solid. The results of its NMR measurement are shown below.

[0167] 1 HNMR(500MHz,DMSO-d6): 8.78(s,4H),8.40(d,2H),8.35(d,2H),8.13(dd,1H)

[0168] <Synthesis Example 2>

[0169]

[0170] Using 4-cyano-3-trifluoromethylaniline (manufactured by Tokyo Chemical Industry Co., Ltd.) in place of 4-aminophthalonitrile, and otherwise operating in the same manner as in Synthesis Example 1, a compound (3) was obtained. The results of its NMR measurement are shown below.

[0171] 1 HNMR(500MHz,DMSO-d6): 8.77(s,4H),8.45(d,2H),8.31(d,2H),8.11(dd,2H)

[0172] <Synthesis Example 3>

[0173]

[0174] Using 4-aminoisophthalonitrile (manufactured by Ambeed, Inc.) in place of 4-aminophthalonitrile, and otherwise operating in the same manner as in Synthesis Example 1, a compound (4) was obtained. The results of its NMR measurement are shown below.

[0175] 1 HNMR(500MHz,DMSO-d6): 8.87(s,4H),8.81(t,2H),8.50(dd,2H),8.08(dd,2H)

[0176] <Synthesis Example 4>

[0177]

[0178] 4-Amino-3-(trifluoromethyl)benzonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was used in place of 4-aminophthalonitrile, and otherwise the same operations as in Synthesis Example 1 were carried out to obtain Compound (5). The results of its NMR measurement are shown below.

[0179] 1 HNMR(500MHz,TFA-d): 8.98(s,4H), 8.30(s,2H), 8.17(dd,2H), 7.76(d,2H)

[0180] <Synthesis Example 5>

[0181]

[0182] 4-Amino-3-fluorobenzonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was used in place of 4-aminophthalonitrile, and otherwise the same operations as in Synthesis Example 1 were carried out to obtain Compound (6). The results of its NMR measurement are shown below.

[0183] 1 HNMR(500MHz,DMSO-d6): 8.80(s,4H), 8.21(d,2H), 7.98(d,2H), 7.76(t,2H)

[0184] <Synthesis Example 6>

[0185]

[0186] 4-Amino-2,5-difluorobenzonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was used in place of 4-aminophthalonitrile, and otherwise the same operations as in Synthesis Example 1 were carried out to obtain Compound (7). The results of its NMR measurement are shown below.

[0187] 1 HNMR(500MHz,DMSO-d6): 8.83(s,4H), 8.37(dd,2H), 7.98(t,2H)

[0188] <Synthesis Example 7>

[0189]

[0190] A mixture obtained by adding 2.0 g of 1,4,5,8-naphthalenetetracarboxylic dianhydride (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 (1)) to 15 mL of acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred under reflux at 125 °C for 8 hours. Thereafter, it was cooled to room temperature, methanol was added thereto, and the precipitated mixture was filtered. Further, after washing with methanol, pyridine was added and stirred for 5 minutes. Then, after filtration, it was washed with methanol and purified by sublimation to obtain a compound (8) presenting a white solid. The results of its NMR measurement are shown below.

[0191] 1 HNMR(500MHz,DMSO-d6): 8.73(s,4H),7.58~7.45(m,10H)

[0192] <Synthesis Example 8>

[0193]

[0194] 4-Aminobenzonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 4-aminophthalonitrile, and otherwise, the same operation as in Synthesis Example 1 was carried out to obtain a compound (9). The results of its NMR measurement are shown below.

[0195] 1 HNMR(500MHz,HFIP-d2): 8.93(s,4H),8.77(d,4H),7.55(dm,4H)

[0196] <Synthesis Example 9>

[0197]

[0198] p-Anisidine (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 4-aminophthalonitrile, and otherwise, the same operation as in Synthesis Example 1 was carried out to obtain a compound (10). It should be noted that in the structural formula of compound (10), "Me" represents a methyl group. The results of its NMR measurement are shown below.

[0199] 1 HNMR(500MHz,DMSO-d6): 8.72(s,4H),7.37(d,2H),7.11(d,2H),3.85(s,6H)

[0200] [Fabrication and Evaluation of Organic Thin Films and Photoelectric Conversion Elements]

[0201] In the following Examples and Comparative Examples, an organic thin film and a photoelectric conversion element were fabricated using an evaporation apparatus, and current-voltage application measurements were performed under atmospheric conditions. The fabricated photoelectric conversion element was placed in a measurement chamber, and current-voltage application measurements were carried out. During the current-voltage application measurements, an automatic IV measurement machine (manufactured by System Engineers CO., LTD) was used. For the irradiation of light, a light source device (manufactured by Asahi Spectra Co., Ltd., product name (PVL-3300)) was used, and the measurements were conducted under the conditions of an irradiation light wavelength of 550 nm and an irradiation light half-value width of 20 nm. The light-dark ratio is the value obtained by dividing the current value during light irradiation by the current value in the dark.

[0202] In addition, Compound (11) was used after being sublimation-purified from N,N'-bis(4-pyridyl)-1,4,5,8-naphthalenetetracarboxylic diimide (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0203]

[0204] (Example 1)

[0205] On ITO transparent conductive glass (ITO manufactured by GEOMATEC Co., Ltd., thickness 100 nm), phthalocyanine boron chloride (purified product manufactured by Sigma Aldrich, purity > 99%) as a photoelectric conversion layer was vacuum-deposited with a thickness of 100 nm. On top of it, a sublimation-purified product of tris(8-hydroxyquinoline) aluminum (Alq3) (manufactured by Tokyo Chemical Industry Co., Ltd.) as Auxiliary Layer 1 was deposited with a thickness of 25 nm by resistance-heated vacuum evaporation. Subsequently, Compound (2) as Auxiliary Layer 2 was deposited with a thickness of 25 nm by resistance-heated vacuum evaporation. Then, aluminum as an electrode was deposited with a thickness of 100 nm by vacuum deposition on Auxiliary Layer 2, thereby obtaining a photoelectric conversion element.

[0206] For the obtained photoelectric conversion element, with ITO and aluminum as electrodes, a voltage of 5 V was applied, and the current value in the dark and the current value during light irradiation were measured. The light-dark ratio was calculated based on the measurement results. The results are shown in Table 1. It should be noted that the dark current value and the light-dark ratio are represented by relative values with the value of Comparative Example 1 described later set to 1.

[0207] (Example 2)

[0208] Compound (3) was used in place of Compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and an electric conversion element. For the obtained photoelectric conversion element, the same evaluation as in Example 1 was carried out. The results are shown in Table 1.

[0209] (Example 3)

[0210] Compound (4) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0211] (Example 4)

[0212] Compound (5) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0213] (Example 5)

[0214] Compound (6) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0215] (Example 6)

[0216] Compound (7) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0217] (Comparative Example 1)

[0218] Compound (8) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0219] (Comparative Example 2)

[0220] Compound (9) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0221] (Comparative Example 3)

[0222] Compound (10) was used in place of compound (2), and otherwise, the same operations as in Example 1 were performed to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0223] (Comparative Example 4)

[0224] Compound (11) was used in place of compound (2), and otherwise, the same operations as in Example 1 were carried out to fabricate a single-layer organic thin film and a photoelectric conversion element. The obtained photoelectric conversion element was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0225] [Table 1]

[0226]

[0227] From the results shown in Table 1, it can be seen that: the dark current value of the photoelectric conversion element of the present invention shows a low value, and thus, it has an excellent effect of preventing leakage current in the dark. Furthermore, it can be seen that: it has a high contrast ratio and an even more excellent effect of preventing leakage current. In summary, it can be seen that: the compound of the present invention is suitable as a material for a photoelectric conversion element, particularly a material contained in the electron transport layer and the hole blocking layer of a photoelectric conversion element.

[0228] Industrial Applicability

[0229] By using a material for a photoelectric conversion element containing the compound (1) of the present invention, a photoelectric conversion element excellent in required characteristics such as prevention of leakage and transport of holes or electrons, and further heat resistance and visible light transparency can be provided. Therefore, the compound (1), the material for a photoelectric conversion element, the organic thin film, and the photoelectric conversion element of the present invention have industrial applicability in fields requiring such characteristics. Specifically, as a solid-state imaging element, it also has industrial applicability in imaging elements in security cameras, in-vehicle cameras, unmanned aerial vehicle cameras, agricultural cameras, industrial cameras, medical cameras such as endoscope cameras, gaming cameras, digital still cameras, digital video cameras, mobile phone cameras, and cameras for other mobile devices; image reading elements in facsimiles, scanners, copiers, etc.; and light sensors in biological and chemical sensors, etc. In addition, as a display using electroluminescence, it has industrial applicability in television displays, touch displays, digital signage, wearable displays, electronic paper, head-up displays for mobile applications, etc.

[0230] Explanation of Reference Numerals

[0231] 100... Photoelectric conversion element, 101... Substrate, 102... Lower electrode, 103... First auxiliary layer, 104... Photoelectric conversion layer, 105... Second auxiliary layer, 106... Upper electrode, 110... Photoelectric conversion film.

Claims

1. A compound represented by the following formula (1), which has a symmetry axis in its molecular structure and at least one of R3, R4, R5, and R6 is not a hydrogen atom, R1 and R2 are hydrogen atoms; R3, R4, R5, and R6 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which are optionally substituted, and any adjacent R3, R4, R5, and R6 are optionally part of a fused aliphatic ring or a fused aromatic ring, and the fused aliphatic ring and the fused aromatic ring optionally contain one or more atoms other than carbon.

2. The compound according to claim 1, wherein In the formula (1), at least one of R3, R4, R5, and R6 is selected from the group consisting of a halogen atom, a hydroxyl group, a mercapto group, an amino group, a cyano group, a carboxyl group, a nitro group, and a 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, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and a monovalent heterocyclic group, which are optionally substituted.

3. The compound according to claim 1, wherein, The energy level of the lowest unoccupied orbital of the compound represented by the formula (1) obtained by density functional method is -6.00 eV or more and -3.80 eV or less.

4. The compound according to claim 1, which is a material for a photoelectric conversion element.

5. An organic thin film comprising the compound according to claim 1.

6. The organic thin film according to claim 5, which has a maximum absorption wavelength of a light absorption band at 450 nm or less.

7. A photoelectric conversion element comprising a first electrode film, a second electrode film, and a photoelectric conversion film disposed between the first electrode film and the second electrode film, wherein the photoelectric conversion film comprises the material for a photoelectric conversion element according to claim 4.

8. A photoelectric conversion element comprising a first electrode film, a second electrode film, and a photoelectric conversion film disposed between the first electrode film and the second electrode film, wherein the photoelectric conversion film comprises the organic thin film according to claim 5.

9. The photoelectric conversion element according to claim 7 or 8, wherein, The photoelectric conversion film comprises a photoelectric conversion layer and an auxiliary layer, and the auxiliary layer is formed only of the organic thin film or is formed of a plurality of films including the organic thin film.

10. An imaging element comprising the photoelectric conversion element according to claim 7 or 8.

11. The imaging element according to claim 10, which is formed by laminating two or more of the photoelectric conversion elements.

12. An imaging element formed by arranging a plurality of the photoelectric conversion elements according to claim 7 or 8 in an array.

13. An optical sensor comprising the imaging element according to claim 10.

14. A solid-state imaging device comprising the imaging element according to claim 10.

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