Compound, hole transport material, and photoelectric conversion element using said compound

Abstract

A compound represented by the general formula is useful as a hole transport material for photoelectric conversion elements. In the general formula, R1 represents an alkylene group or the like; and R2 to R9 each represent a hydrogen atom, an amino group, an aromatic hydrocarbon group or the like.

Description

Compound, hole transport material, and photoelectric conversion element using said compound

[0001] The present invention relates to a compound useful as a hole transport material and a photoelectric conversion device using the compound.

[0002] In recent years, solar power generation has attracted attention as a clean energy source, and the development of solar cells has been actively pursued. Among these, the development of solar cells using perovskite materials in the photoelectric conversion layer (hereinafter referred to as "perovskite solar cells") has attracted attention as a next-generation solar cell that can be manufactured at low cost and by solution processing (e.g., Patent Document 1, Non-Patent Documents 1 and 2). Perovskite solar cells often include a layer formed of a hole transport material within the device. The purposes of using a hole transport material include (1) improving photoelectric conversion efficiency and (2) protecting perovskite materials, which are susceptible to the effects of moisture and oxygen (e.g., Non-Patent Documents 3 and 4). Conventionally, Spiro-OMeTAD has often been used as a standard organic hole transport material, and there have been few reports of organic hole transport materials that contribute more significantly to photoelectric conversion properties than Spiro-OMeTAD.

[0003] International Publication No. 2017 / 104792

[0004] Journal of the American Chemical Society, 2009, Vol. 131, pp. 6050-6051 Science, 2012, Vol. 388, pp. 643-647 Chem. Sci., 2019, 10, pp. 6748-6769 Adv. Funct. Mater., 2019, 1901296 J. Am. Chem. Soc., 2018, 140, 48, 16720-16730

[0005] When an organic compound is used as a hole transport material, a dopant has traditionally been added to the hole transport layer to reduce the electrical resistance of the hole transport material. However, the use of a dopant as an additive not only complicates the manufacturing process but also increases manufacturing costs. It has also been reported that the use of a dopant accelerates deterioration of the hole transport layer due to moisture absorption, corrosion of the photoelectric conversion layer, and volatilization by the dopant, which leads to reduced durability of the device (e.g., Non-Patent Document 5). Therefore, it is desirable to develop a photoelectric conversion device that exhibits high photoelectric conversion characteristics and durability even when the hole transport layer does not contain a dopant or when the dopant concentration in the hole transport layer is low. The problem to be solved by the present invention is to provide an organic compound useful as a hole transport material, and also to provide a photoelectric conversion device and a solar cell that exhibit excellent photoelectric conversion characteristics.

[0006] In order to solve the above problems, the inventors have conducted extensive research and found that by using a compound having a structure in which a sulfonate group is linked to a phenoxazine skeleton as a hole transport material, it is possible to obtain a photoelectric conversion element or a solar cell having good photoelectric conversion efficiency and high durability. The present invention has been proposed based on this finding and specifically has the following configuration.

[0007] [1] A compound represented by the following general formula (1):

[0008] In the formula, R 1 R represents a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, a cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, an arylene group having 6 to 36 carbon atoms which may have a substituent, or a divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent, and X represents a monovalent cation other than a hydrogen ion. 2 ~R 9each independently represent a hydrogen atom, a linear or branched alkyl group of 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 12 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent, an aryloxy group of 6 to 36 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent, a thio group of 0 to 18 carbon atoms which may have a substituent, an amino group of 0 to 20 carbon atoms which may have a substituent, a monovalent aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent, or a monovalent heterocyclic group of 5 to 36 ring atoms which may have a substituent.

[0009] [2] R 1 is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent. 1 The compound according to [1] or [2], wherein the atom R is a secondary carbon atom or a carbon atom constituting the skeleton of a benzene ring. 2 ~R 9 [5] The compound according to any one of [1] to [3], wherein at least one of R is a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent or an amino group having 0 to 20 carbon atoms which may have a substituent. 2 ~R 9The compound according to any one of [1] to [4], wherein at least one of the above is a group having an optionally substituted diarylamino group. [6] The compound according to [5], wherein the diarylamino group is substituted with a substituent bonded via a heteroatom. [7] The compound according to [5], wherein the group having an optionally substituted diarylamino group is an optionally substituted diarylamino group, a diarylaminoaryl group, or an optionally substituted diarylaminocarbazol-9-yl group. [8] A hole transport material comprising the compound according to any one of [1] to [7]. [9] A photoelectric conversion element using the hole transport material according to [8].

[10] A solar cell having the photoelectric conversion element according to [9].

[0010] The compound of the present invention is useful as a hole transport material. By using the compound of the present invention as a hole transport material in a photoelectric conversion element, a photoelectric conversion element and a solar cell having good photoelectric conversion efficiency and high durability can be obtained.

[0011] 1 is a schematic cross-sectional view showing an example of the configuration of a photoelectric conversion element of the present invention.

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In this specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In addition, the compound represented by general formula (1) and R 1 ~R 9 Some or all of the hydrogen atoms present in the group represented by may be substituted with deuterium atoms. In this specification, "transparent" and "light-transmitting" refer to a transmittance of light to be used for photoelectric conversion of 50% or more, for example, 80% or more, for example, 90% or more, for example, 99% or more. The light transmittance can be measured using an ultraviolet-visible spectrophotometer.

[0013] <Compound Represented by General Formula (1)> The compound of the present invention has a structure represented by the above general formula (1). In general formula (1), R 1 represents a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, a cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, an arylene group having 6 to 36 carbon atoms which may have a substituent, or a divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent.

[0014] In general formula (1), R 1 The number of carbon atoms in the "straight-chain or branched alkylene group having 1 to 18 carbon atoms" in the "straight-chain or branched alkylene group having 1 to 18 carbon atoms, which may have a substituent," represented by the formula (I) above, is selected from integers of 1 to 18, and may be selected from the range of, for example, 1 to 12, or may be selected from the range of, for example, 1 to 6. Specific examples of the "straight-chain or branched alkylene group having 1 to 18 carbon atoms, which may have a substituent," include divalent groups obtained by removing one hydrogen atom from an alkyl group such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group, heptyl group, octyl group, isooctyl group, nonyl group, and decyl group, and divalent groups obtained by removing one hydrogen atom from a substituted alkyl group in which at least one hydrogen atom of the alkyl group has been substituted with a substituent (the former divalent group is preferred).

[0015] In general formula (1), R 1The number of carbon atoms in the "straight-chain or branched alkenylene group having 2 to 20 carbon atoms" in the "straight-chain or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 2 to 20, and may be selected from the range of, for example, 2 to 12, or may be selected from the range of, for example, 2 to 6. Specific examples of the "straight-chain or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent" include divalent groups obtained by removing one hydrogen atom from a vinyl group, a 1-propenyl group, an allyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 1-hexenyl group, an isopropenyl group, an isobutenyl group, or a straight-chain or branched alkenyl group having 2 to 20 carbon atoms to which a plurality of these alkenyl groups are bonded, and divalent groups obtained by removing one hydrogen atom from a substituted alkenyl group in which at least one hydrogen atom of the alkenyl group has been substituted with a substituent (the initial divalent group is preferred).

[0016] In general formula (1), R 1 The number of carbon atoms in the "straight-chain or branched alkynylene group having 2 to 20 carbon atoms" in the "straight-chain or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent" represented by the following formula is selected from integers of 2 to 20, and may be selected from the range of, for example, 2 to 12, or may be selected from the range of, for example, 2 to 6. Specific examples of the "linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent" include divalent groups obtained by removing one hydrogen atom from an alkynyl group, such as an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 1-methyl-2-propynyl group, a 1-pentynyl group, a 2-pentynyl group, a 1-methyl-n-butynyl group, a 2-methyl-n-butynyl group, a 3-methyl-n-butynyl group, or a 1-hexynyl group, and divalent groups obtained by removing one hydrogen atom from a substituted alkynyl group in which at least one hydrogen atom of the alkynyl group has been substituted with a substituent (the former divalent group is preferred).

[0017] In general formula (1), R 1The number of carbon atoms in the "cycloalkylene group having 3 to 12 carbon atoms" in the "cycloalkylene group having 3 to 12 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 3 to 12, and may be selected from the range of 3 to 6, for example. Specific examples of the "cycloalkylene group having 3 to 12 carbon atoms which may have a substituent" include divalent groups obtained by removing one hydrogen atom from a cycloalkyl group such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecyl group, and cyclododecyl group, and divalent groups obtained by removing one hydrogen atom from a substituted cycloalkyl group in which at least one hydrogen atom of the cycloalkyl group has been substituted with a substituent (the former divalent groups are preferred).

[0018] In general formula (1), R 1 The aromatic ring constituting the "arylene group having 6 to 36 carbon atoms" in the "arylene group having 6 to 36 carbon atoms which may have a substituent" represented by the formula (I) may be a monocycle, a fused ring in which two or more rings are fused, or a linked ring in which two or more rings are linked by a single bond. When it is a fused ring, the number of fused rings is, for example, 2 to 6, such as 2 to 4. When it is a linked ring, the number of linked rings is, for example, 2 to 6, such as 2 to 4. The number of carbon atoms in the aromatic ring is selected from integers of 6 to 36, and may be selected from the range of, for example, 6 to 22 or 6 to 18, or may be selected from the range of, for example, 6 to 14 or 6 to 10. Specific examples of the "arylene group having 6 to 36 carbon atoms which may have a substituent" include divalent groups obtained by removing one hydrogen atom from a monovalent aromatic hydrocarbon group (aryl group) such as a phenyl group, biphenyl group, terphenyl group, naphthyl group, biphenyl group, anthracenyl group (anthryl group), phenanthryl group, fluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, and triphenylenyl group, and divalent groups obtained by removing one hydrogen atom from a substituted aryl group in which at least one hydrogen atom of the aryl group has been substituted with a substituent (the former divalent groups are preferred).

[0019] In general formula (1), R 1The heterocycle constituting the "divalent heterocyclic group having 5 to 36 ring atoms" in the "divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by the formula (I) may be a monocycle or a fused ring in which two or more rings are fused. In the case of a fused ring, the number of fused rings is, for example, 2 to 6, e.g., 2 to 4. The heterocycle may be an aromatic heterocycle or an aliphatic heterocycle. Examples of heteroatoms constituting the heterocycle include a nitrogen atom, an oxygen atom, and a sulfur atom. The number of carbon atoms in the aromatic heterocycle is selected from integers of 5 to 36, and may be selected from the range of, for example, 5 to 30 or 5 to 18. Specific examples of the "divalent heterocyclic group having 5 to 36 ring atoms" include a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group (furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzo Examples of such a divalent group include a divalent group obtained by removing one hydrogen atom from a monovalent heterocyclic group such as an oxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbonylyl group, and a divalent group obtained by removing one hydrogen atom from a substituted heterocyclic group in which at least one hydrogen atom of the monovalent heterocyclic group has been substituted with a substituent (the former divalent group is preferred).

[0020] In general formula (1), R 1Specific examples of the "substituent" in the "optionally substituted linear or branched alkylene group having 1 to 18 carbon atoms," "optionally substituted linear or branched alkenylene group having 2 to 20 carbon atoms," "optionally substituted linear or branched alkynylene group having 2 to 20 carbon atoms," "optionally substituted cycloalkylene group having 3 to 12 carbon atoms," "optionally substituted arylene group having 6 to 36 carbon atoms," or "optionally substituted divalent heterocyclic group having 5 to 36 ring atoms," represented by the formula (I) include: a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a cyano group; a hydroxyl group; a nitro group; a nitroso group; a carboxyl group; a phosphate group; a carboxylic acid ester group such as a methyl ester group or an ethyl ester group; a linear or branched alkyl group having 1 to 18 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, or a decyl group; or a vinyl group linear or branched alkenyl groups having 2 to 20 carbon atoms, such as 1-propenyl, allyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, isopropenyl, and isobutenyl; linear or branched alkoxy groups having 1 to 18 carbon atoms, such as methoxy, ethoxy, propoxy, t-butoxy, pentyloxy, and hexyloxy; monovalent aromatic hydrocarbon groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, anthryl, phenanthryl, and pyrenyl; pyridyl, pyrimidinyl, and triazinyl monovalent heterocyclic groups having 5 to 30 ring atoms, such as a thienyl group, a furyl group (a furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbonylyl group; unsubstituted amino groups (—NH);Examples of such substituents include substituted amino groups having 1 to 18 carbon atoms, such as monosubstituted amino groups such as alkylamino groups (e.g., ethylamino groups), acetylamino groups, and arylamino groups (e.g., phenylamino groups), or disubstituted amino groups such as dialkylamino groups (e.g., diethylamino groups), diarylamino groups (e.g., diphenylamino groups), and acetylphenylamino groups; unsubstituted thio groups (thiol groups: —SH); substituted thio groups having 1 to 18 carbon atoms, such as methylthio groups, ethylthio groups, propylthio groups, hex-5-ene-3-thio groups, phenylthio groups, and biphenylthio groups (hereinafter, these substituents will be referred to as “Substituent Group A”). R; 1 Each group represented by the formula (I) may contain only one or more substituents selected from Substituent Group A, and when more than one is contained, the substituents may be the same or different. In addition, a hydrogen atom of each of the substituents constituting Substituent Group A may be further substituted with a substituent selected from Substituent Group A.

[0021] R in general formula (1) 1 is preferably a linear or branched alkylene group having 1 to 18 carbon atoms (preferably 1 to 12, e.g., 1 to 6) which may have a substituent, and examples thereof include unsubstituted alkylene groups, and examples thereof include alkylene groups substituted with an alkenyl group, an alkynyl group, a cycloalkyl group, or an aryl group. 1 is also preferably an arylene group having 6 to 36 (preferably 6 to 14, e.g., 6 to 10) carbon atoms which may have a substituent. 1 The atom is preferably a secondary carbon atom or a carbon atom constituting the backbone of a benzene ring.

[0022] X in the sulfonate group (—SOX) of general formula (1) represents a monovalent cation other than a hydrogen ion. Specific examples of the monovalent cation include, but are not limited to, alkali metal ions, optionally substituted ammonium ions, and optionally substituted phosphonium ions.

[0023] Specific examples of alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, and francium ions, with sodium ions, potassium ions, rubidium ions, and cesium ions being preferred.

[0024] Specific examples of the ammonium ion which may have a substituent include a methylammonium ion, a methylammonium monofluoride ion, a methylammonium difluoride ion, a methylammonium trifluoride ion, an ethylammonium ion, an isopropylammonium ion, an n-propylammonium ion, an isobutylammonium ion, an n-butylammonium ion, a t-butylammonium ion, a dimethylammonium ion, a diethylammonium ion, a phenylammonium ion, a benzylammonium ion, a phenethylammonium ion, a guanidium ion, a formamidinium ion, an acetamidinium ion, an imidazolium ion, a tri-n-butylammonium ion, and a tetra-n-butylammonium ion.

[0025] Examples of the phosphonium ion which may have a substituent include an ethylphosphonium ion, an isopropylphosphonium ion, an n-propylphosphonium ion, an isobutylphosphonium ion, an n-butylphosphonium ion, a t-butylphosphonium ion, a dimethylphosphonium ion, a diethylphosphonium ion, a phenylphosphonium ion, and a benzylphosphonium ion, as well as ammonium ions in which the nitrogen atom is replaced with a phosphorus atom.

[0026] In general formula (1), R 2 ~R 9each independently represent a hydrogen atom, a linear or branched alkyl group of 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 10 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent, an aryloxy group of 6 to 36 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent, a thio group of 0 to 18 carbon atoms which may have a substituent, an amino group of 0 to 20 carbon atoms which may have a substituent, a monovalent aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent, or a monovalent heterocyclic group of 5 to 36 ring atoms which may have a substituent.

[0027] In general formula (1), R 2 ~R 9 The number of carbon atoms in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms" in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 1 to 18, and may be selected from the range of, for example, 1 to 12, or may be selected from the range of, for example, 1 to 6. Specific examples of the "straight-chain or branched alkyl group having 1 to 18 carbon atoms" are described in the above R 1 Reference can be made to specific examples of the alkyl group (the alkyl group before removal of one hydrogen atom) given in the explanation of the "linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent" represented by the following formula:

[0028] In general formula (1), R 2 ~R 9The number of carbon atoms in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 2 to 20, and may be selected from the range of, for example, 2 to 12, or may be selected from the range of, for example, 2 to 6. Specific examples of the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms" include those listed above under R 1 Reference can be made to the specific examples of the alkenyl group (the alkenyl group before removing one hydrogen atom) given in the explanation of the "straight-chain or branched alkenylene group having 2 to 20 carbon atoms" represented by the following formula:

[0029] In general formula (1), R 2 ~R 9 The number of carbon atoms in the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms" in the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 2 to 20, and may be selected from the range of, for example, 2 to 12, or may be selected from the range of, for example, 2 to 6. Specific examples of the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms" include those listed above under R 1 Reference can be made to the specific examples of the alkynyl group (alkynyl group before removing one hydrogen atom) given in the explanation of the "straight-chain or branched alkynylene group having 2 to 20 carbon atoms" in the above.

[0030] In general formula (1), R 2 ~R 9 The number of carbon atoms in the "cycloalkyl group having 3 to 10 carbon atoms" in the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 3 to 10, and may be selected from the range of, for example, 3 to 6. Specific examples of the "cycloalkyl group having 3 to 10 carbon atoms" are described in the above R 1 Reference can be made to the specific examples of the cycloalkyl group (the cycloalkyl group before removing one hydrogen atom) given in the explanation of the "cycloalkylene group having 3 to 12 carbon atoms" in the above.

[0031] In general formula (1), R 2 ~R 9The number of carbon atoms in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms" in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 1 to 20, and may be selected from the range of, for example, 1 to 12, or may be selected from the range of, for example, 1 to 6. Specific examples of the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms" include methoxy, ethoxy, propoxy, n-butoxy, n-pentyloxy, n-hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, isopropoxy, isobutoxy, s-butoxy, t-butoxy, isooctyloxy, and t-octyloxy.

[0032] In general formula (1), R 2 ~R 9 The number of carbon atoms in the "straight-chain or branched cycloalkoxy group having 3 to 10 carbon atoms" in the "straight-chain or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 3 to 10, and may be selected from the range of, for example, 3 to 6. Specific examples of the "straight-chain or branched cycloalkoxy group having 3 to 10 carbon atoms" include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0033] In general formula (1), R 2 ~R 9 For details and specific examples of the aryl group bonded to the oxy group of the "aryloxy group having 6 to 36 carbon atoms" in the "aryloxy group having 6 to 36 carbon atoms which may have a substituent" represented by the formula: 2 ~R 9 The description of "monovalent aromatic hydrocarbon groups having 6 to 36 carbon atoms" in the above can be referred to. Specific examples of the "aryloxy group having 6 to 36 carbon atoms" include a phenoxy group, a tolyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthyloxy group, an anthryloxy group, a phenanthryloxy group, a fluorenyloxy group, and an indenyloxy group.

[0034] In general formula (1), R 2 ~R 9 The number of carbon atoms in the "straight-chain or branched alkoxycarbonyl group having 1 to 18 carbon atoms" in the "straight-chain or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent" represented by the formula (I) is selected from integers of 1 to 18, and may be selected from the range of, for example, 1 to 12, or may be selected from the range of, for example, 1 to 6. Specific examples of the "alkoxycarbonyl group having 1 to 18 carbon atoms" include a methoxycarbonyl group and an ethoxycarbonyl group.

[0035] In general formula (1), R 2 ~R 9 The "thio group having 0 to 18 carbon atoms which may have a substituent" represented by the formula (I) may be an unsubstituted thio group (thiol group: -SH) or a substituted thio group in which the hydrogen atom of the thiol group is substituted with a substituent. Examples of the substituent of the substituted thio group include an alkyl group and an aryl group, and the hydrogen atom of each of these groups may be substituted with a substituent selected from the above-mentioned substituent group A. For an explanation and specific examples of the alkyl group which is a substituent of the thio group, see the above-mentioned R 2 ~R 9 For details of the "linear or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms", please refer to the description of the "linear or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms" in the above. For details of the aryl group and specific examples, please refer to the description of the R 2 ~R 9 The description of "monovalent aromatic hydrocarbon groups having 6 to 36 carbon atoms" in the above can be referred to. The number of carbon atoms in the substituted thio group is preferably in the range of 1 to 18, and may be, for example, in the range of 1 to 12, or may be, for example, in the range of 1 to 6. Specific examples of "substituted thio groups having 1 to 18 carbon atoms" include a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, and a biphenylthio group.

[0036] In general formula (1), R 2 ~R 9The "amino group having 0 to 20 carbon atoms which may have a substituent" represented by the formula (I) may be an unsubstituted amino group, a mono-substituted amino group, or a di-substituted amino group. Examples of the substituent of each substituted amino group include an alkyl group, an aryl group, and an acyl group, and the hydrogen atom of each of these groups may be substituted with a substituent selected from the above-mentioned substituent group A. For explanations and specific examples of the alkyl group and the alkyl group constituting the acyl group, see the above-mentioned R 2 ~R 9 For details of the "linear or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms", please refer to the description of the "linear or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms" in the above. For details of the aryl group and specific examples, please refer to the description of the R 2 ~R 9 The description of "monovalent aromatic hydrocarbon groups having 6 to 36 carbon atoms" in the above can be referenced. The number of carbon atoms in the monosubstituted amino group and disubstituted amino group is preferably 1 to 20, and may be in the range of 1 to 12, for example. Specific examples of the monosubstituted amino group include alkylamino groups (e.g., ethylamino group), acetylamino groups, and arylamino groups (e.g., phenylamino group). Specific examples of the disubstituted amino group include dialkylamino groups (e.g., diethylamino group), diarylamino groups (e.g., diphenylamino group), and acetylphenylamino groups.

[0037] In general formula (1), R 2 ~R 9 For the explanation of the aromatic ring constituting the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by the formula 1 For specific examples of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms", see the above R 1 Reference can be made to the specific examples of the monovalent aromatic hydrocarbon group (monovalent aromatic hydrocarbon group before removal of one hydrogen atom) given in the description of the “arylene group having 6 to 36 carbon atoms” in the above.

[0038] In general formula (1), R 2 ~R 9 For the explanation of the heterocycle constituting the "monovalent heterocyclic group having 5 to 36 ring atoms" in the "monovalent heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by the formula 1 For specific examples of the "monovalent heterocyclic group having 5 to 36 ring atoms", see the above R 1 Reference can be made to specific examples of the monovalent heterocyclic group (monovalent heterocyclic group before removal of one hydrogen atom) given in the explanation of the "divalent heterocyclic group having 5 to 36 ring atoms" in

[0039] In general formula (1), R 2 ~R 9 For an explanation and specific examples of the "substituent" in the "linear or branched alkyl group of 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent", "linear or branched alkynyl group of 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group of 3 to 10 carbon atoms which may have a substituent", "linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent", "cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent", "aryloxy group of 6 to 36 carbon atoms which may have a substituent", "linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent", "thio group of 0 to 18 carbon atoms which may have a substituent", "amino group of 0 to 20 carbon atoms which may have a substituent", "monovalent aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent", or "monovalent heterocyclic group of 5 to 36 ring atoms which may have a substituent", see the above R 1Reference can be made to the explanation and specific examples (substituent group A) of "substituents" such as "a linear or branched alkylene group having 1 to 18 carbon atoms, which may have a substituent" represented by the following formula: wherein R is an integer from 1 to 10; R is an integer from 1 to 10; and R is an integer from 2 to 30. Here, the substituent of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms, which may have a substituent" is preferably an amino group substituted with a monovalent aromatic hydrocarbon group (aryl group), and more preferably a diarylamino group. The monovalent aromatic hydrocarbon group that is the substituent of the amino group may be substituted with a substituent selected from the above substituent group A.

[0040] In general formula (1), R 2 ~R 9 Among these, at least one is preferably a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or an amino group having 0 to 20 carbon atoms which may have a substituent. 3 , R 4 , R 7 and R 8 It is more preferable that at least one of R is a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent or an amino group having 0 to 20 carbon atoms which may have a substituent, 4 and R 7 It is more preferable that at least one of the R in the general formula (1) is a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or an amino group having 0 to 20 carbon atoms which may have a substituent. When the amino group has a substituent, the number of carbon atoms is 1 to 20. 2 ~R 9 It is also preferable that at least one of R is a group having a diarylamino group. 3 , R 4 , R 7 and R 8 It is also more preferable that at least one of R in general formula (1) is a group having a diarylamino group. 2 ~R 5 and at least one of R 6 ~R 9 It is also preferable that at least one of R is a group having a diarylamino group. 3 and R4 and at least one of R 7 and R 8 It is also more preferable that at least one of R is a group having a diarylamino group, 4 and R 7 is more preferably a group having a diarylamino group. Here, the group having a diarylamino group is, for example, a diarylamino aryl group, for example, a diarylaminocarbazol-9-yl group. For explanations of the aryl groups constituting the diarylamino group, diarylamino aryl group, and diarylaminocarbazol-9-yl group, see the above R 2 ~R 9 Reference can be made to the description of "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in the above. At least one hydrogen atom of the diarylamino group, diarylaminoaryl group, and diarylaminocarbazol-9-yl group may be substituted with a substituent selected from the above-mentioned Substituent Group A. Preferred examples of the substituent include substituents bonded via a heteroatom, such as an alkoxy group (e.g., a methoxy group) and a diarylamino group (e.g., a di(methoxyphenyl)amino group). Preferred examples of the substituent also include heteroaryl groups containing a nitrogen atom as a ring skeleton-constituting atom (e.g., a pyridyl group).

[0041] A preferred group of compounds represented by general formula (1) includes at least R 4 is not a hydrogen atom. 4 Compound group 1a, where R is a diarylamino group which may have a substituent; 4 Compound group 1b, in which R is an optionally substituted diarylaminoaryl group (preferably an optionally substituted diarylaminophenyl group); 4 Compound group 1c, where R is an optionally substituted diarylaminocarbazol-9-yl group; 4 Compound group 1a to 1d includes compound group 1d, in which R2 , R 3 , R 5 ~R 9 may be a hydrogen atom. Compound groups 1a to 1d each contain R 7 does not have to be a hydrogen atom, for example, R 4 and R 7 may be the same group, for example, R 2 , R 3 , R 5 , R 6 , R 8 , R 9 may be a hydrogen atom. Compound groups 1a to 1d may each further satisfy at least one of the following additional conditions. One of the additional conditions is that the "diarylamino" has an alkoxy group (e.g., an alkoxy group having 1 to 6 carbon atoms) as a substituent. Another of the additional conditions is that the "diarylamino" has a heteroaryl group (e.g., a pyridyl group) containing a nitrogen atom as a ring skeleton-constituting atom as a substituent. Another of the additional conditions is that R 1 is a linear or branched alkylene group having 1 to 18 carbon atoms (preferably 1 to 12, e.g., 1 to 6) that may have a substituent, for example, an unsubstituted alkylene group, for example, an alkylene group substituted with an alkenyl group, an alkynyl group, a cycloalkyl group, or an aryl group. 1 is an arylene group having 6 to 36 (preferably 6 to 14, e.g., 6 to 10) carbon atoms which may have a substituent. 1 is a secondary carbon atom. One additional proviso is that X is Li, Na, K, Rb or Cs, such as Li, for example Na, for example K, for example Rb, for example Cs.

[0042] Another preferred group of compounds represented by general formula (1) includes compounds having at least R 3 is not a hydrogen atom. Compound group 2 can be shown as 3 Compound group 2a, where R is an optionally substituted diarylamino group; 3Compound group 2b, in which R is an optionally substituted diarylaminoaryl group (preferably an optionally substituted diarylaminophenyl group); 3 Compound group 2c, where R is an optionally substituted diarylaminocarbazol-9-yl group; 3 Compound group 2d includes compound group 2d, in which R 2 , R 4 ~R 9 may be a hydrogen atom. Compound groups 2a to 2d each contain R 8 does not have to be a hydrogen atom, for example, R 3 and R 8 may be the same group, for example, R 2 , R 4 ~R 7 , R 9 may be a hydrogen atom. Compounds of Groups 2a to 2d each satisfy at least one of the additional conditions described for Compound Group 1.

[0043] Another preferred group of compounds represented by general formula (1) includes compounds having at least R 2 is not a hydrogen atom. 2 Compound group 3a, where R is an optionally substituted diarylamino group; 2 Compound group 3b, in which R is an optionally substituted diarylaminoaryl group (preferably an optionally substituted diarylaminophenyl group); 2 Compound group 3c, where R is an optionally substituted diarylaminocarbazol-9-yl group; 2 Compound group 3d includes compound group 3d, in which R 3 ~R 9 may be a hydrogen atom. Compound groups 3a to 3d each contain R 9 does not have to be a hydrogen atom, for example, R 2 and R 9 may be the same group, for example, R 3~R 8 may be a hydrogen atom. Each of the compounds in the compound group 3a to 3d can satisfy at least one of the additional conditions described for the compound group 1.

[0044] Another preferred group of compounds represented by general formula (1) includes compounds having at least R 5 Compound group 4 can be shown in which R 5 Compound group 4a, in which R is a diarylamino group which may have a substituent; 5 Compound group 4b, in which R is an optionally substituted diarylaminoaryl group (preferably an optionally substituted diarylaminophenyl group); 5 Compound group 4c, in which R is an optionally substituted diarylaminocarbazol-9-yl group; 5 Compound groups 4a to 4d include compound group 4d, in which R 2 ~R 4 , R 6 ~R 9 may be a hydrogen atom. Compound groups 4a to 4d each contain R 6 does not have to be a hydrogen atom, for example, R 5 and R 6 may be the same group, for example, R 2 ~R 4 , R 7 ~R 9 may be a hydrogen atom. Compounds in Group 4a to 4d each satisfy at least one of the additional conditions described for Compound Group 1.

[0045] Specific examples of the compound represented by general formula (1) of the present invention are shown below, but the compounds of the present invention should not be construed as being limited by these specific examples. Note that the following exemplary compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted. Furthermore, the exemplary compounds shown by the following chemical structural formulas are examples of isomers that may exist, and all other isomers and mixtures of two or more isomers are also included as specific examples.

[0046]

[0047] The compound represented by the general formula (1) of the present invention can be synthesized by known methods such as those described in JP 2020-013898 A. As an example, when synthesizing compound (A-1), compound (A-1) can be obtained by introducing a corresponding substituent into 3,7-dibromophenoxazine by Suzuki-Miyaura coupling reaction or Buchwald reaction, and then reacting with the corresponding sultone. Similarly, the compound represented by the general formula (1) can be obtained by known methods using a halogenated phenothiazine derivative as a precursor.

[0048] Methods for purifying the compound represented by general formula (1) of the present invention include purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, etc. Alternatively, these methods may be used in combination to increase the purity of the compound. Furthermore, these compounds can be identified by nuclear magnetic resonance analysis (NMR).

[0049] [Usefulness of the Compound Represented by General Formula (1)] The compound represented by general formula (1) of the present invention is useful as a hole transport material, and can be effectively used as a hole transport material in the hole transport layer of organic electronics devices such as photoelectric conversion elements and organic electroluminescence elements. In the present invention, the term "hole transport material" refers to a material having the function of transporting holes. The hole transport material used in the present invention may consist of the compound represented by general formula (1), or may contain, in addition to the compound represented by general formula (1), a hole transport material other than the compound represented by general formula (1).

[0050] <Photoelectric Conversion Element> Next, the photoelectric conversion element of the present invention will be described. The photoelectric conversion element of the present invention is characterized by including a hole transport material containing a compound represented by general formula (1). For an explanation of the compound represented by general formula (1), please refer to the description in the above section <Compound represented by general formula (1)>. The compound represented by general formula (1) has excellent hole transport properties and can therefore be effectively used as a material for the hole transport layer of a photoelectric conversion element. Preferred embodiments of the photoelectric conversion element will be described below, but the embodiments of the photoelectric conversion element of the present invention should not be construed as being limited by the embodiments shown below. In one embodiment of the present invention, the photoelectric conversion element has, as shown in FIG. 1 , a conductive support 1, an electron transport layer 2, a photoelectric conversion layer 3, a hole transport layer 4, and a counter electrode 5 in this order, and the hole transport layer 4 contains a compound represented by general formula (1). In one embodiment of the present invention, the photoelectric conversion element has, in this order, a conductive support, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a counter electrode, and the hole transport layer contains a compound represented by general formula (1). Here, the photoelectric conversion layer contains, for example, a perovskite compound, and the photoelectric conversion element is, for example, a photoelectric conversion element used in a solar cell.

[0051] Hereinafter, each member and each layer of the photoelectric conversion element will be described using the photoelectric conversion element shown in FIG. 1 as an example.

[0052] [Conductive Support] In the photoelectric conversion element shown in FIG. 1 , the conductive support 1 functions as a cathode that extracts electrons transported from the photoelectric conversion layer 3 via the electron transport layer 2. In one embodiment of the present invention, the conductive support 1 is a conductive support having light-transmitting properties that allow light to pass through the conductive support, such as a conductive substrate having a film of a conductive material formed on a transparent substrate. Specific examples of conductive materials used for the conductive support include conductive transparent oxide semiconductors such as tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), zinc-aluminum oxide (AZO), fluorine-doped tin oxide (FTO), indium oxide (In2O3), and indium-tin composite oxide. It is preferable to use tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), or the like.

[0053] [Electron Transport Layer] The electron transport layer 2 is a layer containing a material (electron transport material) having a function of transporting electrons, and is disposed between the conductive support 1 and the photoelectric conversion layer 3 to transport electrons generated in the photoelectric conversion layer 3 to the conductive support 1 side. This improves the efficiency of electron migration from the photoelectric conversion layer to the conductive support. In addition to this function, the electron transport layer may also have a function of suppressing hole injection from the conductive support. The electron transport layer 2 may be formed adjacent to the conductive support 1, or another layer may be interposed between the conductive support 1 and the electron transport layer 2.

[0054] Specific examples of semiconductor materials used in the electron transport layer include metal oxides such as tin oxide (SnO, SnO, SnO, etc.), titanium oxide (TiO, etc.), tungsten oxide (WO, WO, WO, etc.), zinc oxide (ZnO), niobium oxide (NbO, etc.), tantalum oxide (TaO, etc.), yttrium oxide (YO, etc.), and strontium titanate (SrTiO, etc.); metal sulfides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, and silver sulfide; metal selenides such as titanium selenide, zirconium selenide, indium selenide, and tungsten selenide; and elemental semiconductors such as silicon and germanium. These semiconductor materials may be used alone or in combination of two or more. Preferred examples of the semiconductor material used in the electron transport layer include one or a combination of two or more selected from tin oxide, titanium oxide, and zinc oxide.

[0055] Examples of materials for forming the electron transport layer include pastes (semiconductor pastes) containing fine particles of the semiconductor material. The semiconductor pastes may be commercially available products or may be prepared by dispersing fine powders of the semiconductor material in a solvent. Specific examples of solvents used in preparing the semiconductor paste include, but are not limited to, water; alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or as a mixture of two or more solvents.

[0056] Methods for dispersing semiconductor fine powder in a solvent include grinding the powder in a mortar or the like as needed, and then dispersing it in the solvent using a dispersing machine such as a ball mill, a paint conditioner, a vertical bead mill, a horizontal bead mill, an attritor, etc. When preparing a paste, it is preferable to add a surfactant or the like to prevent aggregation of the semiconductor fine particles, and it is also preferable to add a thickener such as polyethylene glycol to increase the viscosity.

[0057] The electron transport layer can be formed using a known film-forming method. That is, the electron transport layer can be formed using a coating method or a gas-phase process using a coating liquid containing a semiconductor material (e.g., a coating liquid for an electron transport layer such as a semiconductor paste). Specific examples include wet coating methods such as spin coating, inkjet printing, doctor blade printing, drop casting, squeegee printing, screen printing, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor printing, impregnation / coating, and curtain coating, in which the coating liquid for an electron transport layer is applied to a conductive substrate and then baked to remove solvents and additives. Other examples include gas-phase film-forming methods such as sputtering, vapor deposition, electrodeposition, electrodeposition, and microwave irradiation, in which a semiconductor material is formed into a film. Among these, the use of a coating method in which the prepared coating liquid for an electron transport layer is applied by spin coating is preferred, but is not limited thereto. The spin-coating conditions can be set appropriately. The atmosphere in which the film is formed is not particularly limited, and may be air or an inert atmosphere.

[0058] The film thickness of the electron transport layer is, for example, 5 nm to 200 nm, preferably 10 nm to 150 nm. Furthermore, when a dense electron transport layer is used, for example, from the viewpoint of further improving photoelectric conversion efficiency, the thickness of the electron transport layer is preferably usually 5 nm to 100 nm, more preferably 10 nm to 50 nm. In the present invention, when a porous (mesoporous) metal oxide is used in addition to the dense layer, the film thickness is preferably usually 20 nm to 200 nm, more preferably 50 nm to 150 nm.

[0059] [Photoelectric Conversion Layer] The photoelectric conversion layer 3 is a layer for converting light energy into electricity, and more specifically, a layer in which a charge separation state occurs due to light energy, thereby generating holes and electrons. In the photoelectric conversion element shown in Figure 1, the photoelectric conversion layer 3 is formed on the opposite side of the electron transport layer 2 from the conductive support 1.

[0060] An example of the photoelectric conversion layer is a layer formed of a perovskite material (perovskite layer). Here, "perovskite material" means a material having a perovskite structure represented by the general formula ABX3. In the general formula, A represents a monovalent organic cation or a monovalent metal cation, B represents a divalent metal cation, and X represents a halogen ion. Examples of the monovalent cation represented by A include K, + , Rb + , Cs + , CH3NH3 + (hereinafter, MA: methylammonium), NH=CHNH2 + (hereinafter, FA: formamidinium), CH3CH2NH3 + (hereinafter, EA: ethylammonium). Examples of divalent metal cations represented by B include Pb 2+ , Sn 2+ Examples of halogen ions represented by X include I - ,Br -Specific examples of perovskite materials include MAPbI3, FAPbI3, EAPbI3, CsPbI3, MASnI3, FASnI3, EASnI3, MAPbBr3, FAPbBr3, EAPbBr3, MASnBr3, FASnBr3, and EASnBr3. Also included are mixed cation and mixed anion perovskite materials such as (FAMA)Pb(IBr)3, K(FAMA)Pb(IBr)3, Rb(FAMA)Pb(IBr)3, and Cs(FAMA)Pb(IBr)3. The photoelectric conversion layer may contain only one or more of these perovskite materials. The photoelectric conversion layer may be composed solely of a perovskite material, or may contain other materials in addition to the perovskite material. Examples of other materials include a light absorber.

[0061] The perovskite layer can be formed by applying a solution of halide AX and metal halide BX2 (perovskite precursor solution) to form a precursor coating film, and then drying this precursor coating film. Specific examples of A, B, and X can be found in the descriptions of the ions constituting ABX3 above. Specific examples of halide AX include methylammonium halide, formamidine halide, and cesium halide, and specific examples of metal halide BX2 include lead halide and tin halide.

[0062] From the viewpoint of precursor solubility, examples of solvents for the perovskite precursor solution include, but are not limited to, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone, etc. Furthermore, these solvents may be used alone or in combination of two or more. A preferred example of the solvent is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide. Furthermore, it is preferable to use a dehydrated solvent with a water content of 10 ppm or less. The solvent can be dehydrated using a molecular sieve or the like.

[0063] The coating step of the perovskite precursor solution is preferably carried out in a dry atmosphere, more preferably in a dry inert gas atmosphere such as a glove box. This prevents moisture from being mixed into the perovskite layer, allowing high-efficiency perovskite solar cells to be produced with good reproducibility. For the coating method, please refer to the description of the coating method for the electron transport layer coating solution described in the above section [Electron Transport Layer].

[0064] The perovskite layer is formed by drying the precursor coating film thus formed. The precursor coating film may be dried naturally or by heating using a hot plate or the like. The temperature at which the precursor coating film is heated using a hot plate or the like is preferably 50 to 200°C, more preferably 70 to 150°C, from the viewpoint of producing a perovskite material from the precursor. The heating time is preferably about 10 to 90 minutes, more preferably about 10 to 60 minutes.

[0065] The thickness of the photoelectric conversion layer (perovskite layer) is preferably 50 to 1000 nm, more preferably 300 to 700 nm, which suppresses performance degradation due to defects or peeling of the photoelectric conversion layer, prevents the device resistance from becoming excessively high, and allows the photoelectric conversion layer to have sufficient light absorptivity.

[0066] [Hole Transport Layer] In the photoelectric conversion element shown in Fig. 1 , the hole transport layer 4 is a layer containing a material (hole transport material) having a function of transporting holes, and is disposed between the photoelectric conversion layer 3 and the counter electrode 5 to transport holes generated in the photoelectric conversion layer 3 toward the counter electrode 5. This can improve the efficiency of hole transfer from the photoelectric conversion layer to the electrode. In addition to this function, the hole transport layer may also have a function of suppressing electron injection from the counter electrode.

[0067] In the photoelectric conversion element of the present invention, the hole transport layer contains a compound represented by general formula (1) as a hole transport material. The compound represented by general formula (1) contained in the hole transport layer may be one type or two or more types selected from the group of compounds represented by general formula (1). Furthermore, the hole transport layer may contain, in addition to the compound represented by general formula (1), a hole transport material other than the compound represented by general formula (1) (hereinafter referred to as a "second hole transport material") or an additive.

[0068] The second hole transport material may be either an inorganic hole transport material or an organic hole transport material. Specific examples of inorganic hole transport materials include compound semiconductors containing monovalent copper, such as CuI, CuInSe, and CuS, and compounds containing metals other than copper, such as GaP, NiO, CoO, FeO, BiO, MoO, and CrO. Examples of organic hole transport materials include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA); diphenylamine derivatives; polysilane derivatives; polyaniline derivatives; etc. These second hole transport materials may be mixed in the hole transport layer, or a hole transport layer containing the second hole transport material may be laminated on a hole transport layer containing the compound represented by general formula (1).

[0069] For the method of forming the hole transport layer, the description of the method of forming the electron transport layer can be referred to. Furthermore, the following solvents can also be used for the coating solution for the hole transport layer. Specifically, examples of the solvent used for the coating solution for the hole transport layer include aromatic organic solvents such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, and nitrobenzene; alkyl halide organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, and dichloromethane; nitrile solvents such as benzonitrile and acetonitrile; tetrahydrofuran, dioxane, and diisopropyl ether solvents. Examples of suitable organic solvents include, but are not limited to, ether solvents such as isopropyl ether, c-pentyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate and propylene glycol monomethyl ether acetate; and alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, and 2-n-butoxyethanol. These solvents may be used alone or in combination of two or more. Among these, aromatic organic solvents and halogenated alkyl organic solvents are preferably used as the solvent for the hole transport layer-forming coating liquid.

[0070] The atmosphere during film formation of the hole transport layer is preferably a dry atmosphere. Furthermore, it is preferable to use a solvent that has been dehydrated so that the water content is 10 ppm or less in the coating solution. By preventing water contamination, highly efficient perovskite solar cells can be produced with good reproducibility. From the viewpoint of further improving photoelectric conversion efficiency, the thickness of the hole transport layer is preferably 5 nm to 500 nm, and more preferably 10 nm to 250 nm.

[0071] Additives that may be added to the hole transport layer include oxidizing agents (dopants) and basic compounds (basic additives). By adding these additives to the hole transport layer, the carrier concentration of the hole transport layer can be increased, thereby improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0072] Specific examples of the dopant include lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tri[bis(trifluoromethane)sulfonimide] (FK209), NOSbF, SbCl, and SbF. Of these, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0073] The concentration of the dopant in the hole transport layer is preferably 2.0 equivalents or less, more preferably 0.5 equivalents or less, relative to 1 equivalent of the hole transport material. While incorporating an additive into the hole transport layer leads to improved photoelectric conversion efficiency of the photoelectric conversion element, if the dopant concentration is too high, the durability of the photoelectric conversion element may be reduced. Specific examples of basic additives include 4-tert-butylpyridine (tBP), 2-picoline, and 2,6-lutidine, and among these, 4-tert-butylpyridine is preferred. The basic additive may be used in combination with the dopant. The concentration of the basic additive in the hole transport layer is preferably 5 equivalents or less, more preferably 3.5 equivalents or less, relative to 1 equivalent of the hole transport material.

[0074] [Counter Electrode] The counter electrode 5 is an electrode formed on the side of the hole transport layer 4 opposite to the photoelectric conversion layer 3, and is disposed opposite the conductive support 1 with the electron transport layer 2, photoelectric conversion layer 3, and hole transport layer 4 sandwiched therebetween. The counter electrode functions as an anode that extracts holes transported from the photoelectric conversion layer via the hole transport layer. The counter electrode 5 may be provided adjacent to the hole transport layer 4, or an electron blocking layer made of an organic material or an inorganic compound semiconductor may be interposed between the hole transport layer 4 and the counter electrode 5.

[0075] Specific examples of materials constituting the counter electrode include metals such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, magnesium, chromium, cobalt, and copper, or alloys thereof. Among these, gold, silver, or a silver alloy is preferably used because it exhibits high electrical conductivity even in a thin film. Examples of silver alloys include silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper-palladium alloys, and silver-platinum alloys, because they are less susceptible to sulfurization or chlorination and have high stability as a thin film. In addition, the counter electrode is preferably made of a material that can be formed by a gas-phase process such as vapor deposition. When a metal electrode is used as the counter electrode, its film thickness is preferably 10 nm or more, more preferably 50 nm or more, to obtain good conductivity.

[0076] In the photoelectric conversion element shown in FIG. 1 , the conductive support 1 serves as the cathode, and the counter electrode 5 serves as the anode. Light such as sunlight (light used for photoelectric conversion) is preferably irradiated from the conductive support side. When irradiated with sunlight or the like, the photoelectric conversion layer absorbs the light and enters an excited state, generating electrons and holes. These electrons move to the conductive support via the electron transport layer, and the holes move to the counter electrode via the hole transport layer, causing a current to flow, and the element functions as a photoelectric conversion element.

[0077] The photoelectric conversion element of the present invention may also have a conductive support, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a counter electrode in this order. In this case, the conductive support functions as an anode, and the counter electrode functions as a cathode, with electrons generated in the photoelectric conversion layer moving to the counter electrode via the electron transport layer, and holes generated in the photoelectric conversion layer moving to the conductive support via the hole transport layer. This allows current to be extracted to the outside. For descriptions and specific examples of the materials of each part and layer used in this embodiment, please refer to the corresponding descriptions of the photoelectric conversion element shown in Figure 1 above.

[0078] When evaluating the performance (characteristics) of the photoelectric conversion element of the present invention, the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency are measured. The short-circuit current density is the current flowing between the output terminals when the output terminals are short-circuited. 2 The open-circuit voltage is the voltage between the output terminals when they are open. The fill factor is the maximum output (product of current and voltage) divided by the product of the short-circuit current density and the open-circuit voltage, and is mainly affected by the internal resistance. The photoelectric conversion efficiency is the ratio of maximum output (W) to 1 cm 2 The value is divided by the light intensity (W) per unit area and multiplied by 100 to obtain a percentage value.

[0079] The photoelectric conversion element of the present invention can be applied to solar cells, various optical sensors, etc. The solar cell to which the photoelectric conversion element of the present invention is applied is preferably a perovskite solar cell. A solar cell can be obtained by arranging a required number of photoelectric conversion elements containing a compound represented by general formula (1) in a hole transport layer as cells, modularizing the cells, and providing predetermined electrical wiring.

[0080] The features of the present invention will be explained in more detail below by showing examples. The materials, processing contents, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples. Note that the identification of the compounds obtained in the synthesis examples is 1 H-NMR (H-NMR (JEOL Ltd., nuclear magnetic resonance spectrometer, JNM-ECZ400S / L1 model)) was used.

[0081] Synthesis Example 1 Synthesis of Compound (A-1) Phenoxazine (2.0 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and acetic acid (100 mL) were placed in a reaction vessel and stirred. A solution of bromine (3.8 g) in acetic acid (90 mL) was added dropwise over 1 hour while stirring. After stirring for 3 hours, the mixture was cooled in an ice-water bath, and a 5% aqueous solution of sodium thiosulfate (60 g) was added. The resulting solution was added to an aqueous solution prepared from tap water (400 mL) and a 48% aqueous solution of potassium hydroxide (3.2 g), and the precipitated solid was obtained as a crude product. The crude product was purified using a silica gel column (hexane:ethyl acetate) to obtain a compound represented by the following formula (2) (yield: 2.02 g, 54%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 6.37-6.39 (2H), 6.80-6.81 (2H), 6.90-6.92 (2H), 8.54 (1H).

[0082] A reaction vessel was charged with the compound of formula (2) below (0.5 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (1.13 g, manufactured by Tokyo Chemical Industry Co., Ltd.), sodium carbonate (0.34 g), tetrahydrofuran (50 mL), and purified water (25 mL), and the mixture was degassed under reduced pressure. Tetrakistriphenylphosphinepalladium (0.08 g, manufactured by Kanto Chemical Co., Inc.) was then charged, and the mixture was degassed under reduced pressure and stirred for 7 hours under reflux. The aqueous layer of the reaction mixture was separated and removed, and the organic layer was evaporated under reduced pressure. Toluene was then added to the resulting crude product, and the organic layer was evaporated under reduced pressure. The crude product was purified using a silica gel column (toluene:ethyl acetate) to obtain the compound represented by formula (3) below (yield: 0.6 g, 52%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 3.74 (12H), 6.48-6.50 (2H), 6.76-6.79 ( 4H), 6.87 (2H), 6.90-6.93 (8H), 6.98-7.03 (10H), 7.38-7.40 (4H), 8.39 (1H)

[0083] The compound of formula (3) (0.30 g), 55% sodium hydride (0.04 g, manufactured by Kanto Chemical Co., Inc.), and DMF (10 mL) were placed in a reaction vessel and stirred at room temperature for 1 hour. 2,4-butanesultone (0.063 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was then added, and the mixture was stirred at 90°C for 4 hours. The solvent was removed from the reaction solution by distillation under reduced pressure, and the resulting crude product was purified using a silica gel column (ethyl acetate:methanol). Further purification was carried out by recrystallization (ethyl acetate:ethanol), yielding a compound represented by the following formula (A-1) (yield: 0.22 g, 62%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 1.19-1.21 (3H), 1.57-1.66 (1H), 1.92-2.01 (1H), 2.54-2.62 (1H), 3.65-3.74 (13H), 3.86-3.96 (1H), 6.76-6.82 (6H), 6.89-6.93 (10H), 7.01-7.09 (10H), 7.42-7.44 (4H)

[0084] Synthesis Example 2 Synthesis of Compound (A-70) The compound of formula (2) (1.50 g), 4-dimethylaminopyridine (0.107 g, manufactured by Kanto Chemical Co., Inc.), di-tert-butyl dicarbonate (1.49 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and tetrahydrofuran (30 mL) were placed in a reaction vessel and stirred at room temperature for 1 hour. The reaction solution was concentrated under reduced pressure, and the residue was dissolved in ethyl acetate (50 mL) and then washed with tap water (100 mL). The resulting organic layer was dehydrated over magnesium sulfate and then filtered, and the filtrate obtained was concentrated under reduced pressure. The concentrate was purified by reprecipitation (tetrahydrofuran:methanol), and the resulting solid was dried under reduced pressure to obtain a compound represented by the following formula (4) (yield: 1.58 g, 83%). 1 H-NMR (400 MHz, DMSO-d6): δ (ppm) = 7.42-7.49 (2H), 7.31-7.47 (4H), 1.42 (9H).

[0085] 3,6-bis[N,N-bis(4-methoxyphenyl)amino]-9H-carbazole (0.930 g, manufactured by Tokyo Chemical Industry Co., Ltd.), the compound of formula (4) (0.930 g), cesium carbonate (0.668 g, manufactured by Kanto Chemical Co., Inc.), toluene (15 mL), and tert-butanol (3 mL) were added to a reaction vessel, and the mixture was degassed by bubbling with argon for 20 minutes. Tris(dibenzylideneacetone)dipalladium(0) (0.040 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and tri-tert-butylphosphine (0.020 g, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the reaction solution in two portions every four hours, and the mixture was stirred under reflux for eight hours. After allowing the reaction solution to cool, it was filtered through Celite, and the resulting filtrate was concentrated under reduced pressure. The crude product was purified using a silica gel column (toluene:ethyl acetate=50:1). The obtained purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain a compound represented by the following formula (5) as a yellow solid (yield: 0.831 g, 80%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 7.79 (2H), 7.63 (4H), 7.27-7,40 (8H), 7.03 (4H), 6.75-6.84 (32H), 3.67 (24H), 1.56 (9H).

[0086] A compound of formula (5) (0.450 g), 36% hydrochloric acid (6.5 mL), and ethyl acetate (10 mL) were added to a reaction vessel and stirred under reflux for 8 hours. After allowing the reaction solution to cool, saturated aqueous sodium bicarbonate solution (100 mL) was added, followed by extraction and separation using tetrahydrofuran (50 mL). The resulting organic layer was dehydrated using magnesium sulfate and then filtered, and the filtrate was concentrated under reduced pressure. The crude product was purified using a silica gel column (toluene:ethyl acetate = 50:1 to 20:1). The resulting purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain a compound of formula (6) (0.325 g, yield: 77%) as a yellow solid. 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 8.66 (1H), 7.62-7.66 (4H), 7.21-7.27 (4H), 7.03-7.10 (4H), 6.92-6.98 (2H), 6.76-6.89 (34H), 6.71 (2H), 3.62-3.71 (24H).

[0087] The compound of formula (6) (0.251 g), 55% sodium hydride (0.03 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were placed in a reaction vessel and stirred at room temperature for 1 hour. 2,4-butanesultone (0.03 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was then added, and the mixture was stirred at 80°C for 3 hours. The solvent was removed from the reaction mixture by distillation under reduced pressure, and the resulting crude product was purified using a silica gel column (ethyl acetate:methanol = 9:1 to 4:1). The purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain the compound represented by formula (A-70) below as a yellow solid (yield: 0.230 g, 83%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 7.63 (4H), 7.27 (4H), 7.02-7.07 (8H), 6.77-6.92 (34H), 4.01-4 .08 (1H), 3.77-3.85 (1H), 3.64-3.72 (24H), 2.61 (1H), 2.07 (1H), 1.73-1,79 (1H), 1.15-1.26 (3H).

[0088] Synthesis Example 3 Synthesis of Compound (A-71) The compound of formula (6) (0.251 g), potassium tert-butoxide (0.017 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were placed in a reaction vessel and stirred at room temperature for 1 hour. 2,4-butanesultone (0.02 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was then added, and the mixture was stirred at 80°C for 6 hours. The solvent was removed from the reaction solution by distillation under reduced pressure, and the resulting crude product was purified using a silica gel column (ethyl acetate:methanol = 9:1 to 4:1). The purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain the compound represented by formula (A-71) below as a yellow solid (yield: 0.021 g, 17%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 7.62 (4H), 7.51 (4H), 7.08 (4H), 6.75-6.85 (38H), 4.44 (2H), 3.65 (24H), 2.43 (1H), 2.14 (1H), 1.63-1,70 (1H), 1.14 (3H).

[0089] Synthesis Example 4 Synthesis of Compound (A-72) A compound (0.401 g) represented by the following formula (7), a compound (0.930 g) represented by the above formula (4), sodium tert-butoxide (0.200 g, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), toluene (5 mL), and tetrahydrofuran (5 mL) were placed in a reaction vessel, and the mixture was degassed by bubbling with argon for 20 minutes. Tris(dibenzylideneacetone)dipalladium(0) (0.040 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and tri-tert-butylphosphine (0.020 g, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the reaction solution in two portions every four hours, and the mixture was stirred under reflux for 12 hours. The reaction solution was allowed to cool, then filtered through Celite, and the obtained filtrate was concentrated under reduced pressure. The crude product was purified using a silica gel column (toluene:methanol = 100:1 to 20:1). The obtained purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain a compound represented by the following formula (8) as a yellow solid (yield: 0.559 g, yield: 61%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 8.49-8.54 (4H), 7.66-7.68 (4H), 7.55-7.61 (4H), 7 .41 (2H), 7.08 (4H), 6.92-6.98 (8H), 6.74 (2H), 6.57 (2H), 3.72 (6H), 1.40-1.48 (9H).

[0090] The compound of formula (8) (0.500 g), 36% hydrochloric acid (7 mL), and ethyl acetate (20 mL) were added to a reaction vessel and stirred under reflux for 2 hours. After allowing the reaction mixture to cool, saturated aqueous sodium bicarbonate solution (50 mL) was added, followed by extraction with tetrahydrofuran (50 mL) and toluene (50 mL) and separation. The resulting organic layer was dehydrated using magnesium sulfate, and the filtrate obtained by filtration was concentrated under reduced pressure. The crude product was purified using a silica gel column (toluene:methanol = 80:1 to 20:1). The resulting purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain the compound represented by formula (9) below as a yellow solid (yield: 0.233 g, 58%). 1H-NMR (400MHz, DMSO-d6): δ (ppm) = 8.50 (4H), 8.30 (1H), 7.56-7,62 (8H), 7.06 (4H), 6.91 (4H), 6.80 (4H), 6.32-6.53 (6H), 3.72 (6H).

[0091] The compound of formula (9) (0.233 g), 55% sodium hydride (0.05 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were placed in a reaction vessel and stirred at room temperature for 1 hour. 2,4-butanesultone (0.055 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was then added, and the mixture was stirred at 80°C for 2 hours. The solvent was removed from the reaction mixture by distillation under reduced pressure, and the resulting crude product was purified using a silica gel column (ethyl acetate:methanol = 9:1 to 4:1). The purified fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain the compound represented by formula (A-72) below as a yellow solid (yield: 0.140 g, 49%). 1 H-NMR (400MHz, DMSO-d6): δ (ppm) = 8.50 (4H), 7.57-7.67 (8H), 7.07 (4H), 6.74-6.92 (10H), 6.54-6.56 (2H), 6.31-6 .35 (2H), 3.79-3.90 (1H), 3.73 (6H), 3.54-3.60 (1H), 2.35-2.42 (1H), 1.87-1.96 (1H), 1.56 (1H), 1.10-1.14 (3H).

[0092] Example 1 Preparation of Photoelectric Conversion Element Using Compound (A-1) 1 Glass with an ITO film (conductive support 1, manufactured by Geomatec Co., Ltd.) was ultrasonically cleaned with isopropyl alcohol and subjected to UV ozone treatment. Thereafter, the following layers were formed by coating in a dry atmosphere with a relative humidity of 10% or less. First, a tin oxide dispersion (electron transport layer coating liquid) prepared by mixing a tin oxide colloidal solution (tin(IV) oxide, 15% in HO colloidal dispersion: manufactured by Alfa Aesar) and purified water at a volume ratio of 1:9 was spin-coated onto the ITO film. The resulting mixture was then heated on a hot plate at 150°C for 30 minutes to form a tin oxide layer (electron transport layer 2) with a thickness of approximately 20 nm. Next, formamidine hydroiodide (1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), lead(II) iodide (1.1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), methylamine hydrobromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.), and lead(II) bromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in a mixed solvent of dimethylformamide and dimethyl sulfoxide (volume ratio) at a ratio of 4:1. A perovskite precursor solution was then prepared by adding a dimethyl sulfoxide solution of cesium iodide (1.5 M, manufactured by Tokyo Chemical Industry Co., Ltd.). The cesium iodide solution was added in an amount such that the cesium content was 5% by composition. This perovskite precursor solution was then added dropwise onto the tin oxide layer, followed by spin coating while adding chlorobenzene (0.3 mL) dropwise, to form a perovskite precursor coating. Subsequently, the substrate was heated on a hot plate at 100°C for 1 hour to form a Cs(MAFA)Pb(IBr) perovskite layer (photoelectric conversion layer 3) with a film thickness of approximately 500 nm. Next, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine as dopants were dissolved in chlorobenzene to prepare a solution, and compound (A-1) was dissolved in this solution at a concentration of 50 mM to prepare a hole transport layer coating solution. Here, the concentrations of lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine in the hole transport coating solution were 0.5 equivalents and 3 equivalents, respectively, relative to compound (A-1).The hole transport layer coating solution was spin-coated on the Cs(MAFA)Pb(IBr) layer and then dried to form a hole transport layer 4 with a thickness of approximately 200 nm. Next, a layer was deposited on the hole transport layer 4 by vacuum deposition at a vacuum degree of 1×10. -4 Gold was evaporated to a thickness of 80 nm at 1000 kJ / cm 2 Pa to form a gold electrode (counter electrode 5), thereby preparing a photoelectric conversion element.

[0093] Example 2 Preparation of Photoelectric Conversion Element Using Compound (A-1) 2 A photoelectric conversion element was prepared in the same manner as in Example 1, except that lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine were not added when preparing the hole transport layer coating solution, and the prepared hole transport coating solution was spin-coated at room temperature.

[0094] Example 3 Preparation of Photoelectric Conversion Element Using Compound (A-70) 1 A photoelectric conversion element was prepared in the same manner as in Example 1, except that a solution prepared by the following procedure was used as the hole transport layer coating solution. A dopant solution was prepared by dissolving lithium bis(trifluoromethanesulfonyl)imide in acetonitrile to a concentration of 1.8 M in a dry atmosphere with a relative humidity of 10% or less. A chlorobenzene solution was prepared in which compound (A-70) was dissolved to a concentration of 28 mM, and the dopant solution was added so that the amount of lithium bis(trifluoromethanesulfonyl)imide was 0.5 equivalents relative to compound (A-70). Furthermore, 4-tert-butylpyridine was added so that the amount was 3.3 equivalents relative to compound (A-70) to prepare a hole transport layer coating solution.

[0095] Example 4 Preparation of Photoelectric Conversion Element Using Compound (A-70) 2 A photoelectric conversion element was prepared in the same manner as in Example 3, except that the dopant solution and 4-tert-butylpyridine were not added when preparing the hole transport layer coating solution.

[0096] Example 5 Preparation 1 of photoelectric conversion element using compound (A-71) A photoelectric conversion element was prepared in the same manner as in Example 3, except that compound (A-71) was used instead of compound (A-70).

[0097] Example 6 Preparation of Photoelectric Conversion Element Using Compound (A-71) 2 A photoelectric conversion element was prepared in the same manner as in Example 5, except that the dopant solution and 4-tert-butylpyridine were not added when preparing the hole transport layer coating solution.

[0098] Comparative Example 1 Preparation of Photoelectric Conversion Element Using Compound (B-1) A photoelectric conversion element was prepared in the same manner as in Example 1, except that the above-mentioned Spiro-OMeTAD (manufactured by Sigma-Aldrich), a standard hole transport material, was used as compound (B-1) instead of compound (A-1).

[0099] [Evaluation of Characteristics 1] The fabricated photoelectric conversion element was subjected to a white light irradiation test using a simulated sunlight (AM 1.5, 1000 W / m) generated by a white light irradiation device (OTENTO-SUN SH type, manufactured by Bunkoukeiki Co., Ltd.). 2 ) was irradiated from the conductive support side, and the initial photoelectric conversion efficiency (PCE) measured with a source meter (Model 2400 Series Source Meter, manufactured by Keithley Corporation) is shown in Table 1. Table 1 also shows the short-circuit current, open-circuit voltage, and fill factor of each photoelectric conversion element.

[0100] As shown in Table 1, the photoelectric conversion elements of the Examples, which used a compound corresponding to general formula (1) as a hole transport material, exhibited superior photoelectric conversion efficiency compared to the photoelectric conversion element of Comparative Example 1, which used compound (B-1), a conventional standard hole transport material. Furthermore, when a compound corresponding to general formula (1) was used as a hole transport material, higher photoelectric conversion characteristics were obtained than when compound (B-1) was used, even without the use of a dopant. From these results, it was found that the photoelectric conversion efficiency was improved by using a compound represented by general formula (1) as a hole transport material. It was also found that it became possible to eliminate the need for dopants and basic additives, thereby reducing manufacturing costs and simplifying the manufacturing process.

[0101] [Characteristic Evaluation 2] The initial photoelectric conversion efficiency of the prepared photoelectric conversion element was measured using the same method as above, and then the photoelectric conversion element was sealed in a resealable laminate bag (AL-8, Seisan Nippon Co., Ltd.) in a glove box under a nitrogen atmosphere. The sealed photoelectric conversion element was placed in a vacuum constant temperature dryer (VOS-310C, Tokyo Rikakikai Co., Ltd.) and stored at 85°C for 1000 hours. The photoelectric conversion efficiency (PCE) after 1000 hours of heating was measured again using the same method as above under simulated solar light irradiation. The retention rate (%) calculated using the obtained initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 1000 hours of heating according to the following formula (a-1) is shown in Table 2.

[0102]

[0103] The results in Table 2 show that the photoelectric conversion elements of the Examples, which used the compounds corresponding to general formula (1) as hole transport materials, maintained high photoelectric conversion efficiencies even after 1000 hours of heating, compared with the photoelectric conversion element of Comparative Example 1, which used compound (B-1), a conventional standard hole transport material, and exhibited excellent heat resistance.

[0104] By using the compound of the present invention as a hole transport material, a photoelectric conversion element and a solar cell having good photoelectric conversion efficiency can be realized. As a result, electrical energy converted from solar energy can be efficiently provided as clean energy. Furthermore, hole transport materials containing the compound of the present invention can be applied to organic EL elements, image sensors, and the like. Therefore, the present invention has high industrial applicability.

[0105] REFERENCE SIGNS LIST 1 conductive support 2 electron transport layer 3 photoelectric conversion layer 4 hole transport layer 5 counter electrode

Claims

1. A compound represented by the following general formula (1). 【Chemical 1】 [wherein, R １ is A linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, A linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, A linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, A cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, An arylene group having 6 to 36 carbon atoms which may have a substituent, or A divalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, X represents a monovalent cation excluding a hydrogen ion. R ２ ~R ９ are each independently A hydrogen atom, A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent, A linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent, A linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent, A cycloalkyl group having 3 to 12 carbon atoms which may have a substituent, A linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, A cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, An aryloxy group having 6 to 36 carbon atoms which may have a substituent, A linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, A thio group having 0 to 18 carbon atoms which may have a substituent, An amino group having 0 to 20 carbon atoms which may have a substituent, A monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or A monovalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent. However, at least one of the following conditions 1 to 5 is satisfied. Condition 1: When R1 is the alkylene group, the atom bonded to SO3X is a secondary carbon atom. Condition 2: R2 is not a hydrogen atom. Condition 3: R3 is not a hydrogen atom. Condition 4: R4 is not a hydrogen atom. Condition 5: R5 is not a hydrogen atom. ]

2. R １ The compound according to claim 1, wherein R is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent.

3. SO ３ R bonded to X １ The compound according to claim 1, wherein the atom of R is a secondary carbon atom or a skeletal constituent carbon atom of a benzene ring.

4. R ２ to R ９ Among them, at least one is a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent or an amino group having 0 to 20 carbon atoms which may have a substituent. The compound according to claim 1.

5. R ２ ~R ９ The compound according to claim 1, wherein at least one of

6. The compound according to claim 5, wherein the diarylamino group is substituted with a substituent bonded by a hetero atom.

7. The compound according to claim 5, wherein the group having a diarylamino group which may have a substituent is a diarylamino group which may have a substituent, a diarylaminoaryl group which may have a substituent, or a diarylaminocarbazol-9-yl group which may have a substituent.

8. A hole transport material containing a compound represented by the following general formula (1). 【Chemical 2】 [In the formula, R1 is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, a cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, an arylene group having 6 to 36 carbon atoms which may have a substituent, or a divalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, X represents a monovalent cation excluding a hydrogen ion. R2 to R9 are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 3 to 12 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, an aryloxy group having 6 to 36 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, a thio group having 0 to 18 carbon atoms which may have a substituent, an amino group having 0 to 20 carbon atoms which may have a substituent, a monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or a monovalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent. ]

9. A photoelectric conversion element using the hole transport material according to claim 8.

10. A solar cell having the photoelectric conversion element according to claim 9.

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