TW202411207A - Photoelectric conversion element material, and photoelectric conversion element using same - Google Patents

Abstract

Provided are: a material that imparts increased sensitivity and resolution to photoelectric conversion elements for imaging; and a photoelectric conversion element for imaging using this material. A photoelectric conversion element material comprising a compound represented by general formula (1) is used. Ar1 to Ar3 each represent deuterium, a C1-20 alkyl group, a C12-36 aryl heteroaryl amino group, a C6-18 aromatic hydrocarbon group, or the like, with at least one of Ar1 to Ar3 being represented by general formulas (2) to (5); X is C(Ar4Ar5), O, S, or the like; and a and b are integers from 0 to 4. * represents the bonding site with general formula (1), and L1 and L2 each represent a direct bond, a C6-18 aromatic hydrocarbon group, a C3-18 aromatic heterocyclic group, or the like. Ar4 to Ar12 have the same definition as Ar1 to Ar3; c, e, and f represent integers from 0 to 3; and d represents an integer from 0 to 2.

Description

Photoelectric conversion element material and photoelectric conversion element using the same

The present invention relates to a photoelectric conversion element material and a photoelectric conversion element using the same, and in particular to a photoelectric conversion element material that is effectively used in an imaging device.

In recent years, the development of organic electronic devices using thin films formed of organic semiconductors has been promoted. For example, electroluminescent elements, solar cells, transistor elements, photoelectric conversion elements, etc. can be exemplified. In particular, among these, the development of organic electroluminescence (EL) elements, which are electroluminescent elements based on organic substances, is the most advanced, and while promoting applications in smartphones and televisions (TV), etc., development with the goal of higher functionality continues.

On the other hand, the development and practical application of P-N junction devices that previously used inorganic semiconductors such as silicon in photoelectric conversion elements for photography have been promoted, and research is being conducted on the high-performance digital cameras and smartphone cameras, and the application in surveillance cameras, automotive sensors, etc. As topics for responding to these various uses, high sensitivity and pixel miniaturization (high resolution) are listed. In the previous photoelectric conversion elements using inorganic semiconductors, in order to obtain color images, a method of configuring color filters corresponding to the three primary colors of light, red, green, and blue (RGB), on the light receiving part of the photoelectric conversion element is mainly adopted. In the above-mentioned method, since the RGB color filters are arranged on a plane, there are problems in terms of the utilization efficiency and resolution of incident light (Non-Patent Document 1, Non-Patent Document 2).

As one of the solutions to the problem of such photoelectric conversion elements, the development of photoelectric conversion elements using organic semiconductors instead of inorganic semiconductors is being carried out (Non-patent Document 1, Non-patent Document 2). This is to utilize the property of organic semiconductors that they can selectively absorb only light in a specific wavelength region with high sensitivity, and propose to solve the problem of high sensitivity and high resolution by laminating photoelectric conversion elements obtained by using organic semiconductors corresponding to the three primary colors of light. In addition, a device obtained by laminating a photoelectric conversion element including an organic semiconductor and a photoelectric conversion element including an inorganic semiconductor has also been proposed (Non-patent Document 3).

Here, the photoelectric conversion element using an organic semiconductor is an element constructed in the following manner, that is, a photoelectric conversion layer containing a thin film of an organic semiconductor is provided between two electrodes, and a hole blocking layer and/or an electron blocking layer is arranged between the photoelectric conversion layer and the two electrodes as needed. In the photoelectric conversion element, excitons are generated by absorbing light having a desired wavelength using the photoelectric conversion layer, and then holes and electrons are generated by charge separation of the excitons. Thereafter, the holes and electrons migrate to each electrode to convert the light into an electrical signal. In order to promote the above process, a method of applying a bias voltage between the two electrodes is generally used, but reducing the leakage current from the two electrodes generated by applying the bias voltage has become one of the issues. In this case, it can be said that controlling the migration of holes or electrons in a photoelectric conversion element is the key to the characteristics of the photoelectric conversion element.

Organic semiconductors used in each layer of a photoelectric conversion element can be roughly divided into P-type organic semiconductors and N-type organic semiconductors. P-type organic semiconductors are used as hole transport materials, and N-type organic semiconductors are used as electron transport materials. In order to control the migration of holes and electrons in a photoelectric conversion element, various organic semiconductors having appropriate physical properties such as hole mobility, electron mobility, energy value of the highest occupied molecular orbital (HOMO), and energy value of the lowest unoccupied molecular orbital (LUMO) have been developed, but it cannot be said that they have sufficient characteristics yet.

Furthermore, various compounds that are excellent as hole transport materials or electron blocking materials for organic electroluminescent elements or organic solar cells are disclosed, but these compounds are not necessarily excellent as hole transport materials or electron blocking materials for photography. Specifically, one of the important characteristics required of hole transport materials for photoelectric conversion elements for photography is that, for example, in order for a camera to take clear pictures in the dark, it is important to increase the difference between the current value in the state where the shutter is closed and the current value in the state where the shutter is open (brightness-darkness ratio). Therefore, the lower the current value in the dark, the better, and the higher the current value in the bright place, the better. In other words, "high brightness-darkness ratio" is important.

On the other hand, in organic electroluminescent elements, the voltage required to make a certain current flow, luminous efficiency, element life, etc. are the characteristics that are the target of improvement, which are very different from the characteristics required of photoelectric conversion elements for photography. In addition, it is important for organic solar cells to generate a large amount of current in both dark and bright places, which is different from the characteristics required of photoelectric conversion elements for photography, which prefer low current values in dark places.

As described above, the properties required of hole transport materials or electron blocking materials for organic electroluminescent devices or organic solar cells and hole transport materials or electron blocking materials for photoelectric conversion devices for imaging are different. Therefore, it is not clear whether a material that is excellent as a hole transport material or electron blocking material for an organic electroluminescent device or organic solar cell is excellent as a hole transport material or electron blocking material for a photoelectric conversion device for imaging until confirmation is performed through experiments.

Here, Patent Document 1 proposes the following element: quinacridone is used as a P-type organic semiconductor in a photoelectric conversion layer, subphthalocyanine chloride is used as an N-type organic semiconductor, and an indolecarbazole derivative is used in a first buffer layer disposed between the photoelectric conversion layer and an electrode.

In addition, Patent Document 2 proposes a device in which a chrysene dithiophene derivative is used as a P-type organic semiconductor in a photoelectric conversion layer, and a fullerene or subphthalocyanine derivative is used as an N-type organic semiconductor.

Furthermore, Patent Document 3 and Patent Document 4 propose the following element: a carbazole derivative is used in an electron blocking layer disposed between a photoelectric conversion layer and an electrode. Furthermore, Patent Document 5 proposes the following element: a pyrene derivative or a terphenyl derivative is used in an electron blocking layer disposed between a photoelectric conversion layer and an electrode. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2018-85427 [Patent Document 2] Japanese Patent Publication No. 2019-54228 [Patent Document 3] Japanese Patent Publication No. 2011-228614 [Patent Document 4] Japanese Patent Publication No. 2021-77888 [Patent Document 5] Japanese Patent Publication No. 2015-153910 [Non-Patent Document]

[Non-patent document 1] NHK R&D No.132, pp.4-11 (2012.3) [Non-patent document 2] NHK R&D No.174, pp.4-17 (2019.3) [Non-patent document 3] 2019 Institute of Electrical and Electronics Engineers (IEEE) International Electron Devices Meeting (IEDM), pp.16.6.1-16.6.4 (2019)

[The problem that the invention wants to solve]

For photoelectric conversion elements for photography, in order to promote the high functionality of digital cameras and smartphone cameras, or to apply them to surveillance cameras, automotive sensors, etc., higher sensitivity and higher resolution have become issues. In view of this situation, the present invention aims to provide a material for achieving high sensitivity and high resolution of photoelectric conversion elements for photography, and a photoelectric conversion element for photography using the material. [Means for solving the problem]

The inventors of the present invention have conducted intensive research and have found that the process of generating holes and electrons by charge separation of excitons in a photoelectric conversion layer and the process of migration of holes and electrons in a photoelectric conversion element can be efficiently promoted by using a specific compound, thereby completing the present invention.

The present invention is a photoelectric conversion element material, which is characterized by comprising a compound represented by the following general formula (1). In the general formula (1), Ar ¹ to Ar ³ each independently represent deuterium, cyano, halogen, nitro, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, a dialkylamino group having 2 to 20 carbon atoms, a substituted or unsubstituted alkylarylamino group having 7 to 28 carbon atoms, A substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aryl-heteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 10 aromatic groups of the aromatic alkyl group and the aromatic heterocyclic group are linked, at least one of Ar ¹ to Ar ³ is represented by any one of the following general formulae (2) to (8). When Ar ¹ to Ar ³ are groups having a hydrogen atom, the hydrogen atom may be substituted by deuterium or a halogen. X represents C(Ar ⁴ Ar ⁵ ), NAr ⁶ , O, or S. a and b represent the number of substitutions, and each independently represents an integer of 0 to 4.

[Chemistry 2]

In general formulae (2) to (8), * represents a bonding point with general formula (1). ^L1 and ^L2 each independently represent a direct bond, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking two to three of these aromatic rings. ^Ar4 to ^Ar12 each independently represent the same as those described in ^Ar1 to ^Ar3 , and when ^Ar4 to ^Ar12 represent a linked aromatic group, they represent a substituted or unsubstituted linked aromatic group formed by linking two to three aromatic rings. ^Ar4 and ^Ar5 may be linked to each other to form a ring structure. c to f represent substitution numbers, c, e, and f each independently represent an integer from 0 to 3, and d represents an integer from 0 to 2.

The general formula (1) is preferably represented by any one of the following general formulas (9) to (12). The general formula (1) is more preferably represented by any one of the following general formulas (9), (11), and (12), and is further preferably represented by any one of the following general formulas (11) and (12). In general formulae (9) to (12), Ar ¹ to Ar ⁶ , and a and b are the same as those described in general formula (1).

Preferably, at least one of Ar ¹ to Ar ³ in the general formula (1) is represented by any one of the general formulas (2) to (8), and more preferably, is represented by any one of the general formulas (2), (3), (5), (7), and (8).

In addition, ^L1 in the general formulae (2) to (8) is preferably a single bond.

In the photoelectric conversion element material, the energy level of the highest occupied molecular orbital (HOMO) obtained by structure optimization calculation based on density functional theory B3LYP/6-31G (d) is preferably -4.0 eV or less. In addition, the energy level of the lowest unoccupied molecular orbital (LUMO) is preferably -2.5 eV or more.

The photoelectric conversion element material preferably has a hole mobility of 1×10 ^-6 cm ² /Vs or more. In addition, the photoelectric conversion element material is preferably amorphous.

The photoelectric conversion element material can be used as a hole transport material.

In addition, the present invention is a photoelectric conversion element having a photoelectric conversion layer and an electron blocking layer between two electrodes. The photoelectric conversion element for imaging is characterized in that at least one of the photoelectric conversion layer and the electron blocking layer contains the photoelectric conversion element material.

The photoelectric conversion element of the present invention may include the photoelectric conversion element material in the electron blocking layer, and may include an electron-transmitting material such as a fullerene derivative in the photoelectric conversion layer. [Effect of the invention]

The photoelectric conversion element material of the present invention can be applied to photoelectric conversion elements for photography, and can also be applied to other sensors or solar cells that convert optical information into signals. It is believed that when the photoelectric conversion element material of the present invention is applied to a photoelectric conversion element for photography, appropriate migration of holes or electrons can be achieved, thereby reducing the leakage current generated by applying a bias voltage when converting light into electrical energy. As a result, a photoelectric conversion element with a low dark current value and a high light-dark ratio can be obtained. Therefore, the material of the present invention is effectively used as a photoelectric conversion element material for a photoelectric conversion film multilayer type photography device.

The photoelectric conversion element in the present invention is a photoelectric conversion element having at least one organic layer between two electrodes and converting light into electrical energy. The organic layer contains a photoelectric conversion element material containing a compound represented by the general formula (1). Specifically, in a photoelectric conversion element for photography having a photoelectric conversion layer and an electron blocking layer between two electrodes, at least one of the photoelectric conversion layer and the electron blocking layer contains a photoelectric conversion element material represented by the general formula (1). Hereinafter, the photoelectric conversion element material containing a compound represented by the general formula (1) will be referred to as the photoelectric conversion element material. In addition, it is sometimes referred to as the material of the present invention or the compound represented by the general formula (1).

The compound represented by the general formula (1) is described below.

Preferred embodiments of the general formula (1) are represented by the general formulas (9) to (12), and are preferably represented by the general formula (9), the general formula (11), or the general formula (12). Among them, the general formula (11) or the general formula (12) is more preferred.

In general formulae (9) to (12), Ar ¹ to Ar ⁶ , and a and b are the same as those described in general formula (1).

In the general formula (1), at least one of Ar ¹ to Ar ³ is represented by any one of the general formulas (2) to (8), and preferably Ar ¹ is represented by any one of the general formulas (2) to (8).

In the general formula (1), at least one of Ar ¹ to Ar ³ is represented by any one of the general formulas (2) to (8), preferably represented by any one of the general formulas (2), (3), (5), (7), or (8), and more preferably represented by any one of the general formulas (2), (5), or (8).

In general formulae (2) to (8), * represents a bonding point with general formula (1), and L ¹ , L ² , Ar ⁴ to Ar ¹² , and c to f are the same as those described in general formulae (2) to (8).

Ar ¹ to Ar ³ each independently represent deuterium, cyano, halogen, nitro, alkyl having 1 to 20 carbon atoms, aralkyl having 7 to 38 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkynyl having 2 to 20 carbon atoms, acyl having 2 to 20 carbon atoms, acyloxy having 2 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, alkoxycarbonyl having 2 to 20 carbon atoms, alkoxycarbonyloxy having 2 to 20 carbon atoms, alkylsulfonyl having 1 to 20 carbon atoms, dialkylamino having 2 to 20 carbon atoms, substituted or unsubstituted alkylarylamino having 7 to 28 carbon atoms, a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aryl-heteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 10 aromatic groups of the aromatic alkyl group and the aromatic heterocyclic group are linked. Among them, preferably, it is a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 6 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 10 aromatic groups in these aromatic alkyl groups and aromatic heterocyclic groups. In addition, when these groups in Ar ¹ to Ar ³ have hydrogen atoms, the hydrogen atoms may be substituted by deuterium or halogen. Furthermore, as described above, at least one of Ar ¹ to Ar ³ is represented by any one of the general formulae (2) to (8).

The alkyl group having 1 to 20 carbon atoms in Ar ¹ to Ar ³ may be any of a linear, branched, or cyclic alkyl group, and is preferably a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. Specific examples thereof include linear saturated alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-dodecyl, n-tetradecyl, and n-octadecyl, branched saturated alkyl groups such as isopropyl, isobutyl, neopentyl, 2-ethylhexyl, and 2-hexyloctyl, and saturated alicyclic alkyl groups such as cyclopentyl, cyclohexyl, cyclooctyl, and 4-butylcyclohexyl.

In addition, specific examples of aralkyl groups having 7 to 38 carbon atoms include benzyl, phenethyl, phenylpropyl, phenylbutyl, naphthylmethyl, triphenylenemethyl, etc. Specific examples of alkenyl groups having 2 to 20 carbon atoms include ethylene, propylene, butylene, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, octenyl, etc. Specific examples of alkynyl groups having 2 to 20 carbon atoms include ethynyl, propynyl, butynyl, pentynyl, etc. Specific examples of acyl groups having 2 to 20 carbon atoms include formyl, acetyl, propionyl, benzoyl, etc. Specific examples of the acyloxy group having 2 to 20 carbon atoms include methyl, acetyl, propionyl, butyryl, benzyl, acryl, butenyl, etc. Specific examples of the alkoxy group having 1 to 20 carbon atoms include methoxy, ethoxy, propoxy, butoxy, etc. Specific examples of the alkoxycarbonyl group having 2 to 20 carbon atoms include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, etc. Specific examples of the alkoxycarbonyloxy group having 2 to 20 carbon atoms include methoxycarbonyloxy, ethoxycarbonyloxy, propoxycarbonyloxy, butoxycarbonyloxy, pentyloxycarbonyl, etc. Specific examples of the alkylsulfonyl group having 1 to 20 carbon atoms include methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, butylsulfonyl group and pentylsulfonyl group.

When Ar ¹ to Ar ³ represent an amino group, they represent a dialkylamino group having 2 to 20 carbon atoms, a substituted or unsubstituted alkylarylamino group having 7 to 28 carbon atoms, a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 36 carbon atoms, and the like. Specific examples of the alkyl group include straight-chain saturated alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and n-octyl, branched saturated alkyl groups such as isopropyl, isobutyl, neopentyl, and 2-ethylhexyl, and saturated alicyclic alkyl groups such as cyclopentyl, cyclohexyl, cyclooctyl, and 4-butylcyclohexyl. Specific examples of the aryl group include phenyl, biphenyl, terphenyl, quaterphenyl, naphthyl, phenanthryl, anthracenyl, triphenylene, pyrenyl, fluorenyl, spirobifluorenyl, etc. Specific examples of the heteroaryl group include pyrrole, pyrrolopyrrole, indole, pyrroloindole, benzindole, naphthopyrrole, isoindole, pyrroloisoindole, benzisoindole, naphthoisopyrrole, carbazole, phenoxazine, phenathiazine, acridine, phenazine, benzocarbazole, indoloindole, indolocarbazole, carbazolecarbazole, benzofuranocarbazole, benzothiophenocarbazole, carboline, thiophene, benzothiophene, naphthothiophene, dibenzothiophene, benzo Radicals derived from thienonaphthalene, benzothienobenzothiophene, benzothienodibenzothiophene, dinaphthothiophene, dinaphthothiophene, naphthobenzothiophene, furan, benzofuran, naphthofuran, dibenzofuran, benzofuranonaphthalene, benzofuranbenzofuran, benzofurandibenzofuran, dinaphthofuran, dinaphthofuranfuran, naphthobenzofuran, pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, and quinoxaline. Specific examples of the dialkylamino group include groups derived from dimethylamino, methylethylamino, diethylamino, dipropylamino, di-n-butylamino, di-tert-butylamino, dipentylamino, dihexylamino, dicyclohexylamino, diheptylamino, dioctylamino, dinonylamino, didecylamino, etc. Specific examples of the alkylarylamino group include groups derived from methylphenylamino, ethylphenylamino, propylphenylamino, butylphenylamino, cyclohexylphenylamino, cyclohexylnaphthylamino, cyclohexylfluorenylamino, cyclohexylphenanthrenylamino, cyclohexylfluorenanthrylamino, cyclohexyltriphenyleneamino, etc. Specific examples of the diarylamino group include groups derived from diphenylamino, phenylnaphthylamino, dinaphthylamino, phenylanthrylamino, phenylfluorenylamino, phenylphenanthrylamino, phenylfluorenanthrylamino, phenyltriphenyleneamino, difluorenylamino, naphthyltriphenyleneamino, di-triphenyleneamino, etc. Specific examples of the arylheteroarylamino group include groups derived from phenylpyridylamino, phenylindolyl, phenyldibenzofuranylamino, phenyldibenzophenylthioamino, etc. Specific examples of the diheteroarylamine group include groups derived from a bis-dibenzofuranylamine group, a bis-dibenzophenylthioamine group, a bis-carbazolylamine group, a dibenzofuranylcarbazolylamine group, a dibenzofuranyldibenzophenylthioamine group, a dibenzophenylthiocarbazolylamine group, and the like.

In Ar ¹ to Ar ³ , the unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms may be a group obtained by removing one hydrogen atom from a known aromatic hydrocarbon. Examples of such aromatic hydrocarbon groups include a group derived from a monocyclic aromatic hydrocarbon such as benzene, a bicyclic aromatic hydrocarbon such as naphthalene, a tricyclic aromatic hydrocarbon such as indacene, biphenyl, phenanthracene, anthracene, phenanthrene, and fluorene, anthracene, acephenanthrylene, aceanthrylene, terphenylene, pyrene, chrysene, tetraphene, tetraphenylene, and tetradene. Preferred are radicals derived from benzene, naphthalene, anthracene, phenanthrene, terphenyl, or pyrene.

In Ar ¹ to Ar ³ , the unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms includes groups obtained by removing one hydrogen atom from an aromatic heterocyclic group. Examples of such aromatic heterocyclic groups include pyrrole, pyrrolopyrrole, indole, pyrroloindole, benzindole, naphthopyrrole, isoindole, pyrroloisoindole, benzisoindole, naphthoisopyrrole, carbazole, benzocarbazole, indoloindole, carbazolecarbazole, indololocarbazole, and a nitrogen-containing aromatic compound having a pyrrole ring such as carboline; thiophene, benzothiophene, naphthothiophene, phenothiazine, dibenzothiophene, benzothiophene-naphthalene, benzothiophene-benzothiophene, benzothiophene-dibenzothiophene, dinaphthothiophene, dibenzo ... Examples include sulfur-containing aromatic compounds having a thiophene ring such as naphthothienothiophene, naphthobenzothiophene, and benzothienocarbazole, furan, benzofuran, naphthofuran, phenoxazine, dibenzofuran, benzofuranonaphthalene, benzofuranobenzofuran, benzofuranodibenzofuran, dinaphthofuran, dinaphthofuranofuran, naphthobenzofuran, and benzofuranocarbazole, oxygen-containing aromatic compounds having a furan ring such as pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, and quinoxaline. Preferred are groups derived from dibenzofuran, dibenzothiophene, carbazole, phenoxazine, phenoxathiazine, benzothienodibenzothiophene, benzofuranodibenzofuran, benzofuranocarbazole, or benzothienocarbazole.

Furthermore, in this specification, an unsubstituted linked aromatic group formed by linking aromatic groups of an aromatic alkyl group and an aromatic heterocyclic group refers to an aromatic group formed by linking two or more aromatic groups through a single bond. These linked aromatic groups may be straight chain-shaped or branched. The linking position when the benzene rings are linked to each other may be any of ortho, meta, and para, preferably para or meta. The aromatic group may be an aromatic alkyl group or an aromatic heterocyclic group, and a plurality of aromatic groups may be the same or different.

Here, when Ar ¹ to Ar ³ represent linked aromatic groups, the number of linkages is 2 to 10, preferably 2 to 8, and more preferably 2 to 6. When Ar ¹ to Ar ³ represent linked aromatic groups, the number of linkages is the total number of linkages of the two carbazole (CBZ) groups described in formulas (2) to (8), the aromatic hydrocarbon groups included in L ¹ , L ² , and Ar ⁶ to Ar ¹² , and the aromatic heterocyclic groups.

In general formula (1) and general formula (9) to general formula (12), a and b represent the number of substitutions and each independently represents an integer of 0 to 4, preferably 0 to 2, and more preferably 0.

In general formulae (2) to (8), ^L1 and ^L2 each independently represent a direct bond, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two to three of these aromatic rings are linked. ^L1 is preferably a direct bond, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, and more preferably a direct bond. ^L2 is preferably a direct bond, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, and more preferably a substituted or unsubstituted aromatic alkyl group having 6 to 12 carbon atoms. Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms and the unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms in ^L1 and ^L2 are the same as those described for ^Ar1 to ^Ar3 except that they are groups obtained by removing two hydrogen atoms from an aromatic hydrocarbon. When ^L1 and ^L2 are linking aromatic groups, the two carbazole (CBZ) groups described in formulas (2) to (8) and formula (1) may be bonded via any of the aromatic hydrocarbon group or the aromatic heterocyclic group included in the linking aromatic group, and may be bonded at both ends or in a branched form.

c to f represent substitution numbers, and c, e, and f each independently represent an integer from 0 to 3, preferably from 0 to 1. d represents an integer from 0 to 2, preferably 0.

Ar ⁴ to Ar ¹² are independently the same as those described for Ar ¹ to Ar ³ , but when Ar ⁴ to Ar ¹² represent a linked aromatic group, they represent a substituted or unsubstituted linked aromatic group consisting of 2 to 3 aromatic rings linked together. Ar ⁴ and Ar ⁵ may be linked to each other to form a ring structure.

When Ar ¹ to Ar ¹² are alkylarylamine groups having 7 to 28 carbon atoms, diarylamine groups having 12 to 36 carbon atoms, arylheteroarylamine groups having 12 to 36 carbon atoms, diheteroarylamine groups having 12 to 36 carbon atoms, aromatic alkyl groups, aromatic heterocyclic groups, or linked aromatic groups, these groups may have a substituent. Examples of the substituent include deuterium, an alkyl group having 1 to 20 carbon atoms, a cyano group, and an alkylsilane group. The alkyl group having 1 to 20 carbon atoms may be any of a linear, branched, or cyclic alkyl group. Among the substituents, deuterium, a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms, or a cyano group are preferred. Specific examples thereof include straight chain saturated alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-dodecyl, n-tetradecyl, and n-octadecyl, branched saturated alkyl groups such as isopropyl, isobutyl, neopentyl, 2-ethylhexyl, and 2-hexyloctyl, and saturated alicyclic alkyl groups such as cyclopentyl, cyclohexyl, cyclooctyl, 4-butylcyclohexyl, and 4-dodecylcyclohexyl. In the present invention, the substituent is substituted on an aromatic ring.

Preferred specific examples of the compound represented by the general formula (1) as the photoelectric conversion device material of the present invention are shown below, but the present invention is not limited to these.

[Chemistry 4] [Chemistry 5] [Chemistry 6] [Chemistry 7] [Chemistry 8] [Chemistry 9] [Chemistry 10] [Chemistry 11] [Chemistry 12] [Chemistry 13] [Chemistry 14] [Chemistry 15] [Chemistry 16] [Chemistry 17] [Chemistry 18] [Chemistry 19] [Chemistry 20] [Chemistry 21] [Chemistry 22] [Chemistry 23] [Chemistry 24] [Chemistry 25] [Chemistry 26] [Chemistry 27] [Chemistry 28] [Chemistry 29] [Chemistry 30] [Chemistry 31] [Chemistry 32] [Chemistry 33] [Chemistry 34] [Chemistry 35] [Chemistry 36] [Chemistry 37] [Chemistry 38] [Chemistry 39] [Chemistry 40] [Chemistry 41] [Chemistry 42] [Chemistry 43] [Chemistry 44] [Chemistry 45] [Chemistry 46] [Chemistry 47] [Chemistry 48] [Chemistry 49] [Chemistry 50] [Chemistry 51] [Chemistry 52] [Chemistry 53] [Chemistry 54]

The compound represented by the general formula (1) of the present invention can be obtained by synthesizing by a method based on various organic synthetic reactions established in the field of organic synthetic chemistry including coupling reactions such as Suzuki coupling, Stille coupling, Grignard coupling, Ulmann coupling, Buchwald-Hartwig reaction, and Heck reaction using commercially available reagents as raw materials, and then purifying by a known method such as recrystallization, column chromatography, and sublimation purification, but the method is not limited to the above methods.

Regarding the photoelectric conversion device material of the present invention, the energy level of the highest occupied molecular orbital (HOMO) obtained by structure optimization calculation based on density functional calculation B3LYP/6-31G (D) is preferably below -4.0 eV, more preferably in the range of -6.0 eV to -4.3 eV, and further preferably in the range of -4.9 eV to -4.4 eV.

Regarding the photoelectric conversion device material of the present invention, the energy level of the lowest unoccupied molecular orbital (LUMO) obtained by structure optimization calculation based on density functional theory B3LYP/6-31G (D) is preferably not less than -2.5 eV, more preferably in the range of -2.0 eV to -0.5 eV, and even more preferably in the range of -1.5 eV to -1.0 eV.

Regarding the photoelectric conversion device material of the present invention, the difference (absolute value) between the HOMO energy level and the LUMO energy level is preferably in the range of 2.0 eV to 5.0 eV, more preferably in the range of 2.5 eV to 4.5 eV, and even more preferably in the range of 3.5 eV to 4.5 eV.

The photoelectric conversion element material of the present invention may have a hole mobility of 1×10 ^-6 cm ² /Vs or more, preferably 1×10 ^-5 cm ² /Vs to 1 cm ² /Vs, and more preferably 1.0×10 ^-4 cm ² /Vs to 1×10 ^-2 cm ² /Vs. The hole mobility can be evaluated by a known method such as a method based on a field effect transistor (FET) type transistor element, a method based on a time-of-flight method, or a space charge limited current (SCLC) method.

The photoelectric conversion element material of the present invention is preferably amorphous. The amorphous state can be confirmed by various methods, for example, by not detecting a peak by X-ray diffraction (XRD) or by not detecting an endothermic peak by differential scanning calorimetry (DSC).

Next, a photoelectric conversion element for imaging using the photoelectric conversion element material of the present invention will be described, but the structure of the photoelectric conversion element for imaging of the present invention is not limited thereto. The description will be made with reference to the accompanying drawings.

FIG1 is a cross-sectional view schematically showing an example of the structure of the imaging photoelectric conversion element of the present invention, wherein 1 represents an electrode, 2 represents a hole blocking layer, 3 represents a photoelectric conversion layer, 4 represents an electron blocking layer, 5 represents an electrode, and 6 represents a substrate. In addition, the structure other than the substrate may be a structure reversed from FIG1 , that is, 1 represents an electrode, 2 represents an electron blocking layer, 3 represents a photoelectric conversion layer, 4 represents a hole blocking layer, 5 represents an electrode, and 6 represents a substrate. The structure is not limited to FIG1 , and layers may be added or omitted as needed.

-Electrode- The electrode used in the imaging photoelectric conversion element using the imaging photoelectric conversion element material of the present invention has the function of capturing holes and electrons generated in the photoelectric conversion layer. In addition, it is also necessary to allow light to enter the photoelectric conversion layer. Therefore, it is ideal that at least one of the two electrodes is transparent or translucent. In addition, the material used as the electrode is not particularly limited as long as it is a conductive material, and examples thereof include: indium tin oxide (ITO), indium zinc oxide (IZO), _SnO2 , antimony doped tin oxide (ATO), ZnO, aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), _TiO2 , and fluorine doped tin oxide (FZO). Conductive transparent materials such as quartz oxide (FTO), metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel and tungsten, inorganic conductive materials such as copper iodide and copper sulfide, conductive polymers such as polythiophene, polypyrrole and polyaniline, etc. These materials can be mixed and used as needed. In addition, two or more layers can be stacked.

-Photoelectric conversion layer- The photoelectric conversion layer is a layer that generates holes and electrons by charge separation of excitons generated by incident light. It can be formed by a single photoelectric conversion material, or it can be formed by combining with a P-type organic semiconductor material as a hole transport material, or an N-type organic semiconductor material as an electron transport material. In addition, two or more P-type organic semiconductors can be used, and two or more N-type organic semiconductors can also be used. It is ideal that one or more of these P-type organic semiconductors and/or N-type organic semiconductors use a pigment material that has the function of absorbing light of a desired wavelength in the visible region. As the P-type organic semiconductor material as a hole transport material, the compound represented by the general formula (1) of the present invention can be used.

As the P-type organic semiconductor material, any material having hole transport properties may be used, and preferably the material represented by the general formula (1) is used, but other P-type organic semiconductor materials may also be used. In addition, two or more materials represented by the general formula (1) may be used in combination. Furthermore, the compound represented by the general formula (1) and other P-type organic semiconductor materials may also be used in combination.

As other P-type organic semiconductor materials, any material with hole transport properties can be used, for example: compounds having condensed polycyclic aromatic groups such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, tetraphenylene, terphenylene, perylene, anthracene, fluorene, indene, etc., compounds having π-excess aromatic groups such as cyclopentadiene derivatives, furan derivatives, thiophene derivatives, pyrrole derivatives, benzofuran derivatives, benzothiophene derivatives, dinaphthothiophene-thiophene derivatives, indole derivatives, pyrazoline derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolecarbazole derivatives, aromatic amine derivatives, styrylamine derivatives, benzidine derivatives, porphyrin derivatives, phthalocyanine derivatives, and quinacridone derivatives.

In addition, examples of polymeric P-type organic semiconductor materials include polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. In addition, two or more selected from the compounds represented by the general formula (1), P-type organic semiconductor materials, or polymeric P-type organic semiconductor materials may be used in combination.

As the N-type organic semiconductor material, any material having electron transport properties may be used, and examples thereof include naphthalenetetracarboxylic acid diimide or perylenetetracarboxylic acid diimide, fullerenes, azole derivatives such as imidazole, thiazole, thiadiazole, oxazole, oxadiazole, and triazole, etc. In addition, two or more selected from the N-type organic semiconductor materials may be used in combination.

-Electron blocking layer- The electron blocking layer is provided to suppress the dark current generated by the injection of electrons from one of the electrodes into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. In addition, it also has the function of hole transport, which is to transfer holes generated by charge separation in the photoelectric conversion layer to the electrode, and can be configured as a single layer or multiple layers as needed. A P-type organic semiconductor material as a hole transport material can be used in the electron blocking layer. As a P-type organic semiconductor material, any material having hole transport properties can be used, and preferably a compound represented by general formula (1) is used, but other P-type organic semiconductor materials can also be used. In addition, a compound represented by general formula (1) and other P-type organic semiconductor materials can also be used in combination. As other P-type organic semiconductor materials, any material having hole transport properties may be used, for example, compounds having condensed polycyclic aromatic groups such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, tetraphenylene, terphenylene, perylene, anthracene, fluorene, indene, cyclopentadiene derivatives, furan derivatives, thiophene derivatives, pyrrole derivatives, benzofuran derivatives, benzothiophene derivatives, dinaphthothiophene derivatives, indole derivatives, pyrazoline derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, compounds having π excess aromatic groups, aromatic amine derivatives, styrylamine derivatives, benzidine derivatives, porphyrin derivatives, phthalocyanine derivatives, and quinacridone derivatives.

In addition, examples of polymeric P-type organic semiconductor materials include polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. In addition, two or more selected from the compounds represented by the general formula (1) of the present invention, P-type organic semiconductor materials, or polymeric P-type organic semiconductor materials may be used in combination.

-Hole blocking layer- The hole blocking layer is provided to suppress the dark current generated by the injection of holes from one of the electrodes into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. In addition, it also has the function of transmitting electrons generated by charge separation in the photoelectric conversion layer to the electrode, and can be configured as a single layer or multiple layers as needed. N-type organic semiconductors with electron transport properties can be used in the hole blocking layer. As N-type organic semiconductor materials, any material having electron transport properties may be used, for example: polycyclic aromatic polycarboxylic anhydrides such as naphthalenetetracarboxylic acid diimide or perylenetetracarboxylic acid diimide or imides thereof, fullerenes such as C60 or C70, azole derivatives such as imidazole, thiazole, thiadiazole, oxazole, oxadiazole, triazole, tris(8-hydroxyquinoline)aluminum(III) derivatives, phosphine oxide derivatives, nitrosubstituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide derivatives, fluorenylmethane derivatives, anthraquinone dimethane derivatives and anthrone derivatives, bipyridine derivatives, quinoline derivatives, indolecarbazole derivatives, etc. In addition, two or more of these N-type organic semiconductor materials may be used in combination.

As described above, the hydrogen in the material of the present invention may be deuterium. That is, in addition to the hydrogen on the aromatic ring in general formula (1) or general formula (2) to general formula (8), part or all of the hydrogen in the substituent may be deuterium. Furthermore, part or all of the hydrogen in the compound used as the N-type organic semiconductor material and the P-type organic semiconductor material may be deuterium.

The film-forming method of each layer when making the photoelectric conversion element for photography of the present invention is not particularly limited, and it can be made by any of dry processes and wet processes. The organic layer containing the material for the photoelectric conversion element of the present invention can also be set as multiple layers as needed. [Example]

The present invention is described in more detail below by way of embodiments, but the present invention is not limited to these embodiments.

Calculation Example Calculation of HOMO and LUMO The HOMO, LUMO, and energy difference between HOMO and LUMO of the compound A4, compound C13, compound D61, compound E42, compound E45, compound E58, compound E126, compound F42, and compound F125 were calculated. The calculation was performed using density functional theory (DFT)-based calculations, using Gaussian as the calculation program, and by structure optimization calculations based on density functional theory B3LYP/6-31G (d). The results are shown in Table 1. It can be said that the photoelectric conversion element materials of the present invention all have better HOMO and LUMO values.

The HOMO, LUMO, and energy difference between HOMO and LUMO of H1, H2, and H3 as comparison compounds were calculated using the same method. The results are shown in Table 1.

[Table 1] Compound HOMO[eV] LUMO[eV] Energy difference [eV] A4 -4.9 -0.7 4.2 C13 -4.8 -1.1 3.7 D61 -4.2 -1.0 3.2 E42 -4.4 -1.1 3.3 E45 -4.5 -1.0 3.5 E58 -4.6 -1.2 3.3 E126 -4.5 -1.2 3.3 F42 -4.7 -1.1 3.7 F125 -4.9 -1.2 3.7 H1 -5.3 -1.9 3.4 H2 -5.0 -0.9 4.1 H3 -5.1 -0.8 4.2

The following is a synthesis example of compound E42 as a representative example. Other compounds were synthesized by similar methods.

Synthesis Example 1 (Synthesis of Intermediate R3) R1 (19.0 mmol), R2 (19.9 mmol), copper iodide (0.4 mmol), tripotassium phosphate (56.9 mmol) were placed in a 500 ml three-necked flask that had been denitrogenated, and 70 ml of dehydrated dioxane was added thereto, followed by stirring at 120°C for 3 hours. After cooling to room temperature, inorganic matter was removed by filtration, and 200 ml of water and 200 ml of dichloromethane were added to the filtrate, which was then transferred to a separatory funnel to separate into an organic layer and an aqueous layer. The organic layer was washed three times with 200 ml of water, and the obtained organic layer was dehydrated with magnesium sulfate and then concentrated under reduced pressure. The obtained residue was purified by column chromatography to obtain R3 (light yellow solid). Yield: 7.5 g, yield: 81.3%.

Synthesis Example 2 (Synthesis of E42) R3 (10.3 mmol), R4 (13.3 mmol), tri-dibenzylideneacetone dipalladium (0.5 mmol), tri-tert-butylphosphine (2.1 mmol), sodium tert-butoxide (30.8 mmol), and 50 ml of dehydrated xylene synthesized in Synthesis Example 1 were placed in a 300 ml three-necked flask that had been denitrogenated and stirred at 120°C for 2 hours. After cooling to room temperature, inorganic matter was removed by filtration, and 200 ml of water and 200 ml of dichloromethane were added to the filtrate, and the filtrate was transferred to a separatory funnel to separate into an organic layer and an aqueous layer. The organic layer was washed three times with 200 ml of water, and the obtained organic layer was dehydrated with magnesium sulfate and then concentrated under reduced pressure. The obtained residue was purified by column chromatography to obtain E42 (light yellow solid). Yield: 4.2 g, yield: 69.4%. The obtained solid was evaluated by XRD method, but no peak was detected, indicating that this compound was amorphous.

Physical property evaluation example Compound E42 was deposited as an organic layer by vacuum evaporation to a thickness of about 3 μm on a glass substrate on which a transparent electrode made of ITO with a thickness of 110 nm was formed. Then, a device formed of aluminum (Al) with a thickness of 70 nm was used as an electrode, and the charge mobility was measured by the time-of-flight method. The result showed that the hole mobility was 1.4×10 ^-4 cm ² /Vs.

The hole mobility was evaluated in the same manner except that compound E42 was replaced by A04, C13, E45, E126, F125, H1, H2, or H3. The results are shown in Table 2.

[Table 2] Compound Hole mobility [cm ² /Vs] A04 5.9×10 ^-4 C13 7.7×10 ^-5 E42 1.4×10 ^-4 E45 1.0×10 ^-4 E126 1.9×10 ^-4 F125 2.3×10 ^-4 H1 4.0×10 ^-5 H2 3.0×10 ^-5 H3 1.0×10 ^-4

Example 1 On an electrode including 70 nm thick ITO formed on a glass substrate, compound E42 was deposited at a vacuum degree of 4.0×10 ^-5 Pa to form a film with a thickness of 10 nm as an electron blocking layer. Then, as a photoelectric conversion layer, 2Ph-BTBT, F6-SubPc-OC6F5, and fullerene (C60) were co-evaporated at a deposition rate ratio of 4:4:2 to form a film of 200 nm. Next, dpy-NDI was evaporated to 10 nm to form a hole blocking layer. Finally, aluminum was deposited at a thickness of 70 nm as an electrode to produce a photoelectric conversion element. When a voltage of 2.6 V was applied using ITO and aluminum as electrodes, the current in the dark (dark current) was 5.1×10 ^-10 A/cm ² . When a voltage of 2.6 V was applied and the ITO electrode side was irradiated from a height of 10 cm with a 1.6 μW LED with a wavelength of 500 nm, the current (bright current) was 3.7×10 ^-7 A/cm ² . The light-dark ratio when a voltage of 2.6 V was applied was 7.3×10 ² . These results are shown in Table 3.

Example 2 to Example 6 Except that the compounds shown in Table 3 are used as electron blocking layers, photoelectric conversion elements are prepared in the same manner as in Example 1.

Comparative Examples 1 to 3 A photoelectric conversion element was prepared in the same manner as in Example 1 except that the compound shown in Table 3 was used as the electron blocking layer. The results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 3.

The compounds used in the Examples and Comparative Examples are shown below.

[table 3] Compound Dark current value [A/cm ² ] Current value when irradiated with light [A/cm ² ] Light-Dark Ratio Embodiment 1 E42 5.1× ^10-10 3.7× ^10-7 7.3×10 ² Embodiment 2 A04 4.8× ^10-10 3.2×10 ^-7 6.7×10 ² Embodiment 3 C13 3.3× ^10-10 3.0×10 ^-7 9.1×10 ² Embodiment 4 E45 3.2× ^10-10 3.5× ^10-7 1.1×10 ³ Embodiment 5 E126 2.9× ^10-10 3.6× ^10-7 1.2×10 ³ Embodiment 6 F125 4.6× ^10-10 3.8×10 ^-7 8.3×10 ² Comparison Example 1 H1 7.5× ^10-10 2.5× ^10-7 3.3×10 ² Comparison Example 2 H2 6.3× ^10-10 3.0×10 ^-7 4.8×10 ² Comparison Example 3 H3 5.5× ^10-10 3.2×10 ^-7 5.8×10 ²

1: Electrode 2: Hole blocking layer 3: Photoelectric conversion layer 4: Electron blocking layer 5: Electrode 6: Substrate

FIG. 1 is a schematic cross-sectional view showing a structural example of a photoelectric conversion element used in the present invention.

1: Electrode

2: Hole blocking layer

3: Photoelectric conversion layer

4:Electron blocking layer

5: Electrode

6: Substrate

Claims (15)

A photoelectric conversion element material, characterized in that it comprises a compound represented by the following general formula (1): In the general formula (1), Ar ¹ to Ar ³ each independently represent deuterium, cyano, halogen, nitro, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, a dialkylamino group having 2 to 20 carbon atoms, a substituted or unsubstituted alkylarylamino group having 7 to 28 carbon atoms, a substituted a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aryl-heteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 10 aromatic groups of the aromatic alkyl groups and the aromatic heterocyclic groups are linked, Ar At least one of ^{Ar 1} to Ar ³ is represented by any one of the following general formulas (2) to (8); further, when Ar ¹ to Ar ³ are groups having hydrogen atoms, the hydrogen atoms may be substituted by deuterium or halogen; X represents C (Ar ⁴ Ar ⁵ ), NAr ⁶ , O, or S; a and b represent the number of substitutions, and each independently represents an integer of 0 to 4; [Chem. 2] [Chemistry 3] In general formulae (2) to (8), * represents the bonding point with general formula (1); ^L1 and ^L2 each independently represent a direct bond, a substituted or unsubstituted aromatic alkyl group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking two to three of these aromatic rings; ^Ar4 to ^Ar12 each independently represent the same as those described in ^Ar1 to ^Ar3 , and when ^Ar4 to ^Ar12 represent a linked aromatic group, they represent a substituted or unsubstituted linked aromatic group formed by linking two to three aromatic rings; ^Ar4 and ^Ar5 may be linked to each other to form a ring structure; c to f represent substitution numbers, c, e, and f each independently represent an integer from 0 to 3, and d represents an integer from 0 to 2. The photoelectric conversion element material according to claim 1, wherein the general formula (1) is represented by any one of the following general formulas (9) to (12): In general formulae (9) to (12), Ar ¹ to Ar ⁶ , and a and b are the same as those described in general formula (1). The photoelectric conversion element material according to claim 2, wherein the general formula (1) is represented by any one of the general formula (11) and the general formula (12). The photoelectric conversion element material according to claim 1, wherein at least one of Ar ¹ to Ar ³ in the general formula (1) is represented by any one of the general formulas (2), (3), (5), (7), and (8). The photoelectric conversion element material according to claim 1, wherein Ar ¹ in the general formula (1) is represented by any one of the general formulas (2), (3), (5), (7), and (8). The photoelectric conversion element material for photography as described in claim 1, wherein ^L1 is a single bond. The material for a photographic photoelectric conversion element as claimed in claim 1, wherein the energy level of the highest occupied molecular orbital (HOMO) obtained by structure optimization calculation based on density functional theory B3LYP/6-31G(d) is -4.0 eV or less. The material for a photographic photoelectric conversion element as claimed in claim 1, wherein the energy level of the lowest unoccupied molecular orbital (LUMO) obtained by the structural optimization calculation is not less than -2.5 eV. The material for a photographic photoelectric conversion element according to claim 1 has a hole mobility of 1×10 ^-6 cm ² /Vs or more. The material for a photoelectric conversion element for imaging as claimed in claim 1 is amorphous. The material for a photographic photoelectric conversion element according to claim 1 is used as a hole transporting material of a photographic photoelectric conversion element. A photoelectric conversion element for photography has a photoelectric conversion layer and an electron blocking layer between two electrodes. The photoelectric conversion element for photography is characterized in that at least one of the photoelectric conversion layer and the electron blocking layer contains the material for the photoelectric conversion element for photography as described in any one of claims 1 to 11. The photoelectric conversion element for imaging as described in claim 12, wherein the electron blocking layer contains the material for the photoelectric conversion element for imaging as described in claim 1. The photoelectric conversion element for photography as described in claim 12, wherein the photoelectric conversion layer contains an electron-transmitting material. The photoelectric conversion element for imaging as described in claim 12, wherein the electron blocking layer contains the photoelectric conversion element material as described in claim 1, and the photoelectric conversion layer contains a fullerene derivative.