WO2024071042A1

WO2024071042A1 - Compound, hole transport material, and photoelectric conversion element using said compound

Info

Publication number: WO2024071042A1
Application number: PCT/JP2023/034740
Authority: WO
Inventors: 泰彰宮崎; 秀聡高橋; 敦史櫻井; 洋佐藤; 俊昭伊東
Original assignee: 保土谷化学工業株式会社
Priority date: 2022-09-30
Filing date: 2023-09-25
Publication date: 2024-04-04
Also published as: TW202428568A

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

The present invention relates to a compound useful as a hole transport material and a photoelectric conversion element using the compound.

In recent years, solar power generation has been attracting attention as a clean energy source, and the development of solar cells has been actively carried out. Among them, 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 by a solution process (for example, Patent Document 1, Non-Patent Documents 1 and 2).
In perovskite solar cells, a layer formed of a hole transport material is often provided in the element. The purpose of using a hole transport material is (1) to improve the photoelectric conversion efficiency, and (2) to protect the perovskite material that is easily affected by moisture and oxygen (for example, Non-Patent Documents 3-4). 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 to photoelectric conversion properties than this material.

International Publication No. 2017/104792

When an organic compound is used as a hole transport material, a dopant is conventionally 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 leads to an increase in manufacturing costs. In addition, it has been reported that the use of a dopant promotes the deterioration of the hole transport layer due to moisture absorption by the dopant, corrosion of the photoelectric conversion layer, and volatilization, which leads to a decrease in the durability of the element (for example, Non-Patent Document 5). Therefore, it is desired to develop a photoelectric conversion element that shows high photoelectric conversion characteristics and durability even when the hole transport layer does not contain a dopant or the dopant concentration of 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 element and a solar cell exhibiting excellent photoelectric conversion characteristics.

　In order to solve the above problems, the inventors conducted extensive research and discovered 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 solar cell with good photoelectric conversion efficiency and high durability. The present invention has been proposed based on this knowledge and specifically has the following configuration.

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

In the formula, 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, and X represents a monovalent cation other than a hydrogen ion. R ² to R ⁹ each independently represent 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 atoms which may have a substituent.

[2] The compound according to [1], wherein R ¹ is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent.
[3] The compound according to [1] or [2], wherein the atom of R ¹ bonded to SO ₃ X is a secondary carbon atom or a skeletal carbon atom of a benzene ring.
[4] The compound according to any one of [1] to [3], wherein at least one of R ² to R ⁹ 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.
[5] The compound according to any one of [1] to [4], wherein at least one of R ² to R ⁹ 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 to a heteroatom.
[7] The compound according to [5], wherein the group having an optionally substituted diarylamino group is an optionally substituted diarylamino group, an optionally substituted 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 comprising the photoelectric conversion element according to [9].

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, it is possible to obtain a photoelectric conversion element and a solar cell having good photoelectric conversion efficiency and high durability.

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

The contents of the present invention will be described in detail below. The following description of the constituent elements may be based on representative 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, some or all of the hydrogen atoms present in the compound represented by general formula (1) and the groups represented by R ¹ to R ⁹ 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 transmittance of light can be measured by an ultraviolet-visible spectrophotometer.

<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.

In the general formula ( 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 R 1 is selected from integers of 1 to 18, and may be selected from the range of, for example, 1 to 12, and 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, 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, and a divalent group obtained by removing one hydrogen atom from a substituted alkyl group in which at least one hydrogen atom of the alkyl group is substituted with a substituent (the former divalent group is preferred).

In the general formula ( ¹ ), the 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 R 1 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 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 divalent group obtained by removing one hydrogen atom from a straight-chain or branched alkenyl group having 2 to 20 carbon atoms to which a plurality of these alkenyl groups are bonded, and a divalent group obtained by removing one hydrogen atom from a substituted alkenyl group in which at least one hydrogen atom of the alkenyl group is substituted with a substituent (the first divalent group is preferred).

In general formula (1), the number of carbon atoms in the "linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent" represented by R ¹ 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 is substituted with a substituent (the former divalent group is preferred).

In general formula (1), the 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 R ¹ is selected from integers of 3 to 12, and may be selected from the range of, for example, 3 to 6. 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, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a 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 is substituted with a substituent (the former divalent group is preferred).

In the general formula (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 R ¹ may be a single ring, 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. In the case of a fused ring, the number of fused rings is, for example, 2 to 6, for example, 2 to 4. In the case of a linked ring, the number of linked rings is, for example, 2 to 6, for example, 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, a biphenyl group, a terphenyl group, a naphthyl group, a biphenyl group, an anthracenyl group (anthryl group), a phenanthryl group, a fluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, or a 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 is substituted with a substituent (the former divalent groups are preferred).

In the general formula (1), the 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 R ¹ may be a monocycle or a condensed ring in which two or more rings are condensed. In the case of a condensed ring, the number of condensed rings is, for example, 2 to 6, for example, 2 to 4. In addition, 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 divalent groups obtained by removing one hydrogen atom from a monovalent heterocyclic group such as a pyridyl group, a pyrimidinyl group, a triazinyl group, 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, 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 is substituted with a substituent (the former divalent group is preferred).

In the general formula (1), examples of the "substituent" in the "linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenylene group having ² to 20 carbon atoms which may have a substituent", "linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent", "cycloalkylene group having 3 to 12 carbon atoms which may have a substituent", "arylene group having 6 to 36 carbon atoms which may have a substituent" or "divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R 1 include, Specifically, halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; cyano groups; hydroxyl groups; nitro groups; nitroso groups; carboxyl groups; phosphoric acid groups; carboxylate groups such as methyl ester groups and ethyl ester groups; linear or branched alkyl groups having 1 to 18 carbon atoms such as methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, s-butyl groups, t-butyl groups, n-pentyl groups, isopentyl groups, n-hexyl groups, 2-ethylhexyl groups, heptyl groups, octyl groups, isooctyl groups, nonyl groups, and decyl groups; vinyl groups such as methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, s-butyl groups, t-butyl groups, n-pentyl groups, isopentyl groups, n-hexyl groups, 2-ethylhexyl groups, heptyl groups, octyl groups, isooctyl groups, nonyl groups, and decyl groups; linear or branched alkenyl groups having 2 to 20 carbon atoms, such as an allyl 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, or an isobutenyl group; linear or branched alkoxy groups having 1 to 18 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, a pentyloxy group, or a hexyloxy group; monovalent aromatic hydrocarbon groups having 6 to 30 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, or a pyrenyl group; a pyridyl group, a pyrimidinyl group, a triazine group, or a cyclic group; monovalent heterocyclic groups having 5 to 30 ring atoms, such as a phenyl group, 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; ₂ ); substituted amino groups having 1 to 18 carbon atoms, such as mono-substituted amino groups, such as alkylamino groups (e.g., ethylamino groups), acetylamino groups, and arylamino groups (e.g., phenylamino groups), or di-substituted 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").
Each group represented by ^R1 may contain only one or more substituents selected from the substituent group A, and when more than one is contained, the substituents may be the same or different. In addition, the hydrogen atom of each of the substituents constituting the substituent group A may be further substituted with a substituent selected from the substituent group A.

R ¹ in the general formula (1) is preferably a linear or branched alkylene group having 1 to 18 carbon atoms (preferably 1 to 12, for example 1 to 6) which 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. R ¹ in the general formula (1) is also preferably an arylene group having 6 to 36 carbon atoms (preferably 6 to 14, for example 6 to 10) which may have a substituent. The atom of R ¹ bonded to SO ₃ X is preferably a secondary carbon atom or a carbon atom constituting the backbone of a benzene ring.

X in the sulfonate group (-SO ₃ X) in general formula (1) represents a monovalent cation other than a hydrogen ion. Specifically, the monovalent cation is preferably an alkali metal ion, an ammonium ion which may have a substituent, or a phosphonium ion which may have a substituent, but is not limited to these.

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.

Specific examples of ammonium ions that may have a substituent include methylammonium ion, methylammonium monofluoride ion, methylammonium difluoride ion, methylammonium trifluoride ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, isobutylammonium ion, n-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidinium ion, formamidinium ion, acetamidinium ion, imidazolium ion, tri-n-butylammonium ion, and tetra-n-butylammonium ion.

Examples of phosphonium ions which may have a substituent include ethyl phosphonium ion, isopropyl phosphonium ion, n-propyl phosphonium ion, isobutyl phosphonium ion, n-butyl phosphonium ion, t-butyl phosphonium ion, dimethyl phosphonium ion, diethyl phosphonium ion, phenyl phosphonium ion, benzyl phosphonium ion, and the above ammonium ions in which the nitrogen atom is replaced with a phosphorus atom.

In general formula (1), R ² to R ⁹ each independently represent 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 10 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 atoms which may have a substituent.

In general formula (1), the number of carbon atoms in the "linear or branched alkyl group having 1 to 18 carbon atoms" in the "linear or branched alkyl group having 1 to ¹⁸ carbon atoms which may have a substituent" represented by ^R 2 to R 9 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. For specific examples of the "linear or branched alkyl group having 1 to 18 carbon atoms", reference may be made to the 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 R 1 above.

In general formula (1), the 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 R 2 to R 9 is selected from integers from 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. For specific examples of the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms", reference may be made to the specific examples of the alkenyl group (alkenyl group before removal of one hydrogen atom) given in the explanation of the "straight-chain or branched alkenylene group having 2 to 20 carbon atoms" represented by R 1 above.

In general formula (1), 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 R 2 to R 9 is selected from integers from 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. For specific examples of the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms", reference may be made to the specific examples of the alkynyl group (alkynyl group before removal of ^one hydrogen atom) given in the explanation of the "straight-chain or branched alkynylene group having 2 to 20 carbon atoms" in R 1 above.

In general formula (1), 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 R ² to R ⁹ is selected from integers of 3 to 10, and may be selected, for example, from the range of 3 to 6. For specific examples of the "cycloalkyl group having 3 to 10 carbon atoms", reference can be made to the specific examples of the cycloalkyl group (cycloalkyl group before removal of one hydrogen atom) given in the explanation of ^the "cycloalkylene group having 3 to 12 carbon atoms" in R 1 above.

In general formula (1), the 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 R 2 to R 9 is selected from an integer 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 a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group, a decyloxy group, an isopropoxy group, an isobutoxy group, an s-butoxy group, a t-butoxy group, an isooctyloxy group, a t-octyloxy group, and the like.

In general formula (1), 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 R 2 to R 9 is selected from integers of 3 to 10, and may be selected, for example, from the range of 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.

In general formula (1), for ^an ^explanation 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 R ² to R ⁹ , reference can be made to the description of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in R 2 to R 9 below. 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.

In general formula (1), the number of carbon atoms in the "straight-chain or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ² to R ⁹ 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, an ethoxycarbonyl group, etc.

In the general formula (1), the "thio group having 0 to 18 carbon atoms which may have a substituent" represented by R ² to R ⁹ 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, 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-mentioned R ² to R ⁹ can be referred to, and for an explanation and specific examples of the aryl group, the description of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in the below-mentioned R ² to R ⁹ can be referred to. The number of carbon atoms of 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 the "substituted thio group having 1 to 18 carbon atoms" include a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, and a biphenylthio group.

In the general formula (1), the "amino group having 0 to 20 carbon atoms which may have a substituent" represented by R ² to R ⁹ 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 the explanation and specific examples of the alkyl group and the alkyl group constituting the acyl group, the above 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 R ² to R ⁹ can be referred to, and for the explanation and specific examples of the aryl group, the description of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in R ² to R ⁹ can be referred to below. The number of carbon atoms of the mono-substituted amino group and the di-substituted amino group is preferably 1 to 20, and may be, for example, in the range of 1 to 12. Specific examples of the mono-substituted amino group include an alkylamino group (e.g., an ethylamino group), an acetylamino group, and an arylamino group (e.g., a phenylamino group). Specific examples of the disubstituted amino group include a dialkylamino group (eg, a diethylamino group), a diarylamino group (eg, a diphenylamino group), and an acetylphenylamino group.

In general formula (1), for an 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 ^R 2 to R 9, the explanation of the aromatic ring constituting the "arylene group having 6 to 36 carbon atoms" in R ¹ above can be referred to, and for specific examples of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms", the specific examples of the monovalent aromatic hydrocarbon group (monovalent aromatic hydrocarbon group before removal of one hydrogen atom) given in the explanation of the "arylene group having 6 to 36 carbon atoms" in R ¹ above can be referred to.

In general formula (1), for an 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 be substituted" represented by R ² to R ⁹ , the description of the heterocycle constituting the "divalent heterocyclic group having 5 to 36 ring atoms" in R ¹ above can be referred to, and for specific examples of the "monovalent heterocyclic group having 5 to 36 ring atoms", the 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 R ¹ above can be referred to.

In the general formula (1), the explanation and specific examples of the "substituents" in the "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group having ² to ²⁰ carbon atoms which may have a substituent", "linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent", "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent", "aryloxy group having 6 to 36 carbon atoms which may have a substituent", "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent", "thio group having 0 to 18 carbon atoms which may have a substituent", "amino group having 0 to 20 carbon atoms which may have a substituent", "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent", or "monovalent heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R 2 to R 9 are described above. 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 formula ( ¹⁾ can be referred to. 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), more preferably a diarylamino group. The monovalent aromatic hydrocarbon group which is the substituent of the amino group may be substituted with a substituent selected from the above substituent group A.

In general formula (1), it is preferable that at least one of R ² to R ⁹ 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. Of these, it is more preferable that at least one of R ³ , R ⁴ , R ⁷ and R ⁸ 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, and it is even more preferable that at least one of R ⁴ and R ⁷ 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. Here, when the amino group has a substituent, the number of carbon atoms is 1 to 20.
It is also preferable that at least one of R ² to R ⁹ in the general formula (1) is a group having a diarylamino group, and it is more preferable that at least one of R ³ , R ⁴ , R ⁷ and R ⁸ is a group having a diarylamino group. It is also preferable that at least one of R ² to R ⁵ and at least one of R ⁶ to R ⁹ in the general formula (1) is a group having a diarylamino group, it is more preferable that at least one of R ³ and R ⁴ and at least one of R ⁷ and R ⁸ are a group having a diarylamino group, and it is even more preferable that R ⁴ and R ⁷ are groups having a diarylamino group. Here, the group having a diarylamino group is, for example, a diarylamino group, for example, a diarylaminoaryl group, for example, a diarylaminocarbazol-9-yl group. For the explanation of each aryl group constituting the diarylamino group, diarylaminoaryl group, and diarylaminocarbazol-9-yl group, the description of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in R ² to R ⁹ above can be referred to. 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. Preferable examples of the substituent include a substituent bonded via a heteroatom, such as an alkoxy group (e.g., a methoxy group) or a diarylamino group (e.g., a di(methoxyphenyl)amino group). Preferable examples of the substituent also include a heteroaryl group containing a nitrogen atom as a ring skeleton-constituting atom (e.g., a pyridyl group).

As a preferred compound group represented by the general formula (1), at least compound group 1 in which R ⁴ is not a hydrogen atom can be mentioned. Compound group 1 includes compound group 1a in which R ⁴ is a diarylamino group which may have a substituent, compound group 1b in which R ⁴ is a diarylaminoaryl group which may have a substituent (preferably a diarylaminophenyl group which may have a substituent), compound group 1c in which R ⁴ is a diarylaminocarbazol-9-yl group which may have a substituent, and compound group 1d in which R ⁴ is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent. In compound groups 1a to 1d, R ² , R ³ , and R ⁵ to R ⁹ in each group may be hydrogen atoms. In compound groups 1a to 1d, R ⁷ in each group may not be a hydrogen atom, and for example, R ⁴ and R ⁷ may be the same group, and for example, R ² , R ³ , R ⁵ , R ⁶ , R ⁸ , and R ⁹ may be hydrogen atoms. Each of the compound groups 1a to 1d can further satisfy at least one of the following additional conditions.
One additional condition is when the "diarylamino" has an alkoxy group (e.g., an alkoxy group having 1 to 6 carbon atoms) as a substituent. One additional condition is when the "diarylamino" has a heteroaryl group (e.g., a pyridyl group) containing a nitrogen atom as a ring skeleton constituent atom as a substituent. One additional condition is when 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. One additional condition is when R ¹ is an arylene group having 6 to 36 carbon atoms (preferably 6 to 14, e.g., 6 to 10) that may have a substituent. One additional condition is when the atom of R ¹ bonded to SO ₃ X is a secondary carbon atom. One additional proviso is that X is Li, Na, K, Rb or Cs, such as Li, such as Na, such as K, such as Rb, such as Cs.

Another preferred compound group represented by the general formula (1) is compound group 2 in which at least R ³ is not a hydrogen atom. Compound group 2 includes compound group 2a in which R ³ is a diarylamino group which may have a substituent, compound group 2b in which R ³ is a diarylaminoaryl group which may have a substituent (preferably a diarylaminophenyl group which may have a substituent), compound group 2c in which R ³ is a diarylaminocarbazol-9-yl group which may have a substituent, and compound group 2d in which R ³ is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent. In compound groups 2a to 2d, R ² and R ⁴ to R ⁹ in each group may be hydrogen atoms. In compound groups 2a to 2d, R ⁸ in each group may not be a hydrogen atom, for example, R ³ and R ⁸ may be the same group, for example, R ² , R ⁴ to R ⁷ , and R ⁹ may be hydrogen atoms. Compound groups 2a to 2d each can satisfy at least one of the additional conditions described in compound group 1.

Another preferred compound group represented by the general formula (1) is compound group 3 in which at least R ² is not a hydrogen atom. Compound group 3 includes compound group 3a in which R ² is a diarylamino group which may have a substituent, compound group 3b in which R ² is a diarylaminoaryl group which may have a substituent (preferably a diarylaminophenyl group which may have a substituent), compound group 3c in which R ² is a diarylaminocarbazol-9-yl group which may have a substituent, and compound group 3d in which R ² is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent. In compound groups 3a to 3d, R ³ to R ⁹ in each group may be a hydrogen atom. In compound groups 3a to 3d, R ⁹ in each group may not be a hydrogen atom, for example, R ² and R ⁹ may be the same group, and for example, R ³ to R ⁸ may be a hydrogen atom. Compound groups 3a to 3d each can satisfy at least one of the additional conditions described in compound group 1.

Another preferred compound group represented by the general formula (1) is compound group 4 in which at least R ⁵ is not a hydrogen atom. Compound group 4 includes compound group 4a in which R ⁵ is a diarylamino group which may have a substituent, compound group 4b in which R ⁵ is a diarylaminoaryl group which may have a substituent (preferably a diarylaminophenyl group which may have a substituent), compound group 4c in which R ⁵ is a diarylaminocarbazol-9-yl group which may have a substituent, and compound group 4d in which R ⁵ is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent. In compound groups 4a to 4d, R ² to R ⁴ and R ⁶ to R ⁹ in each group may be hydrogen atoms. In compound groups 4a to 4d, R ⁶ in each group may not be a hydrogen atom, for example, R ⁵ and R ⁶ may be the same group, for example, R ² to R ⁴ and R ⁷ to R ⁹ may be hydrogen atoms. Compound groups 4a to 4d each can satisfy at least one of the additional conditions described in compound group 1.

Specific examples of the compound represented by general formula (1) of the present invention are shown below, but the compounds of the present invention are not limited to these examples. Note that the following example compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted. Also, the example compound shown in the following chemical structure is one example of isomers that may exist, and all other isomers and mixtures of two or more isomers are also given as specific examples.

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, in the case of synthesizing compound (A-1), the corresponding substituent is introduced into 3,7-dibromophenoxazine by Suzuki-Miyaura coupling reaction or Buchwald reaction, and then the corresponding sultone is reacted to obtain compound (A-1). Similarly, the compound represented by the general formula (1) can be obtained by known methods using a halogenated phenothiazine derivative as a precursor.

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).

[Usefulness of the compound represented by formula (1)]
The compound represented by the 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 a hole transport layer of an organic electronics device such as a photoelectric conversion element or an organic electroluminescence element. In the present invention, the "hole transport material" means a material having a function of transporting holes. The hole transport material used in the present invention may be composed of a compound represented by the general formula (1), or may contain a hole transport material other than the compound represented by the general formula (1) in addition to the compound represented by the general formula (1).

<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 in that it contains a hole transport material containing a compound represented by general formula (1). For an explanation of the compound represented by general formula (1), the description in the above column "Compound represented by general formula (1)" can be referred to. The compound represented by general formula (1) has excellent hole transport properties, so it can be effectively used as a material for the hole transport layer of the 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 to the embodiments described below.
In one embodiment of the present invention, as shown in FIG. 1, the photoelectric conversion element has 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 a conductive support, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a counter electrode in this order, and the hole transport layer contains a compound represented by general formula (1). Here, the photoelectric conversion layer contains, for example, a perovskite compound. The photoelectric conversion element is, for example, a photoelectric conversion element used in a solar cell.

Below, each component and layer of the photoelectric conversion element will be explained using the photoelectric conversion element shown in Figure 1 as an example.

[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 translucency that allows light to pass through the conductive support, and is, for example, a conductive substrate in which a film of a conductive material is formed on a translucent 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 (In ₂ O ₃ ), and indium-tin composite oxide, and it is preferable to use tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc.

[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, and has a function of transporting electrons generated in the photoelectric conversion layer 3 to the conductive support 1 side. This can improve the efficiency of electron migration from the photoelectric conversion layer to the conductive support. In addition to this function, the electron transport layer may 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.

Specific examples of semiconductor materials used in the electron transport layer include metal oxides such as tin oxide (SnO, _SnO2 , _SnO3 , etc.), titanium oxide ( _TiO2 , etc.), tungsten oxide ( _WO2 , _WO3 , _W2O3 _, etc.), zinc oxide (ZnO), niobium oxide ( _Nb2O5 _, etc.), tantalum oxide ( _Ta2O5 , etc.), _yttrium oxide ( _Y2O3 , etc.), and _strontium titanate ( _SrTiO3 , etc.); 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.

As a material for forming the electron transport layer, a paste containing fine particles of the semiconductor material (semiconductor paste) can be mentioned. The semiconductor paste may be a commercially available product, or may be a preparation prepared by dispersing fine powder 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-based solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or as a mixed solvent of two or more types.

Methods for dispersing semiconductor fine powder in a solvent include grinding the powder in a mortar or the like as necessary, and then dispersing it in the solvent using a dispersing machine such as a ball mill, paint conditioner, vertical bead mill, horizontal bead mill, or attritor. When preparing the paste, it is preferable to add a surfactant or the like to prevent the semiconductor fine particles from agglomerating, and it is preferable to add a thickener such as polyethylene glycol to thicken the paste.

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 (for example, a coating liquid for the electron transport layer such as a semiconductor paste). Specifically, a method of forming a film by applying a coating liquid for the electron transport layer to a conductive substrate by a wet coating method such as a spin coating method, an inkjet method, a doctor blade method, a drop casting method, a squeegee method, a screen printing method, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brush method, a spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation/coating method, or a curtain coating method, and then removing the solvent or additives by baking, or a method of forming a film of a semiconductor material by a gas-phase film-forming method such as a sputtering method, a vapor deposition method, an electrodeposition method, an electrodeposition method, or a microwave irradiation method. Among them, it is preferable to use a coating method in which the prepared coating liquid for the electron transport layer is applied by a spin coating method, but this is not limited to this. The conditions for spin coating can be set appropriately. The atmosphere in which the film is formed is not particularly limited, and may be air or an inert atmosphere.

The thickness of the electron transport layer is, for example, 5 nm to 200 nm, and 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 usually preferably 5 nm to 100 nm, and 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 thickness is usually preferably 20 nm to 200 nm, and more preferably 50 nm to 150 nm.

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

An example of the photoelectric conversion layer is a layer (perovskite layer) formed of a perovskite material. Here, the "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 ⁺ , CH ₃ NH ₃ ⁺ (hereinafter, MA: methylammonium), NH=CHNH ₂ ⁺ (hereinafter, FA: formamidinium), and CH ₃ CH ₂ NH ₃ ⁺ (hereinafter, EA: ethylammonium). Examples of the divalent metal cation represented by B include Pb ²⁺ and Sn ²⁺ . Examples of the halogen ion represented by X include I ^- and Br ^- .
Specific examples of perovskite materials include MAPbI ₃ , FAPbI ₃ , EAPbI ₃ , CsPbI ₃ , MASnI ₃ , FASnI ₃ , EASnI ₃ , MAPbBr ₃ , FAPbBr ₃ , EAPbBr ₃ , MASnBr ₃ , FASnBr ₃ , and EASnBr ₃ . In addition, mixed cation type and mixed anion type perovskite materials such as (FAMA)Pb(IBr) ₃ , K(FAMA)Pb(IBr) ₃ , Rb(FAMA)Pb(IBr) ₃ , and Cs(FAMA)Pb(IBr) ₃ can also be mentioned. The photoelectric conversion layer may contain only one type selected from these perovskite materials, or may contain two or more types.
The photoelectric conversion layer may be composed of only the perovskite material, or may contain other materials in addition to the perovskite material. Examples of the other materials include a light absorbing agent.

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 drying the precursor coating film. For specific examples of A, B, and X, the description of each ion constituting _ABX3 above can be referred to. For example, specific examples of the halide AX include methylammonium halide, formamidine halide, and cesium halide, and specific examples of the metal halide _BX2 include lead halide and tin halide.

From the viewpoint of solubility of the precursor, examples of the solvent 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, etc.

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

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.

The thickness of the photoelectric conversion layer (perovskite layer) is preferably 50 to 1000 nm, and more preferably 300 to 700 nm. This suppresses performance degradation due to defects or peeling in the photoelectric conversion layer, prevents the element resistance from becoming excessively high, and provides the photoelectric conversion layer with sufficient light absorption.

[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, and has a function of transporting holes generated in the photoelectric conversion layer 3 to the counter electrode 5. This can improve the efficiency of hole movement from the photoelectric conversion layer to the electrode. In addition to this function, the hole transport layer may have a function of suppressing electron injection from the counter electrode.

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.

The second hole transport material may be 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, _CuInSe2 , and CuS, and compounds containing metals other than copper, such as GaP, NiO, CoO, FeO, _Bi2O3 , _MoO2 , and _Cr2O3 _. Examples of the organic hole transport material 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).

For the method of forming the hole transport layer, the description of the method of forming the electron transport layer can be referred to. In addition, the following can also be used as a solvent for the coating solution for the hole transport layer.
That is, the solvent used in the coating solution for the hole transport layer may be an aromatic organic solvent such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, or nitrobenzene; an alkyl halide organic solvent such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, or dichloromethane; a nitrile solvent such as benzonitrile or acetonitrile; or a tetrahydrofuran, dioxane, or diisopropyl ether solvent. Examples of the solvent 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 them, it is preferable to use an aromatic organic solvent and an alkyl halide organic solvent as the solvent for the hole transport layer forming coating liquid.

The atmosphere during film formation of the hole transport layer is preferably a dry atmosphere. In addition, it is preferable to use a solvent that has been dehydrated so that the moisture content is 10 ppm or less in the coating solution. By preventing the inclusion of moisture, a highly efficient perovskite solar cell can be produced with good reproducibility.
From the viewpoint of further improving the 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.

Additives The additives that may be added to the hole transport layer include an oxidizing agent (dopant) and a basic compound (basic additive). By adding these additives to the hole transport layer, the carrier concentration of the hole transport layer is improved, and the photoelectric conversion efficiency of the photoelectric conversion element can be improved.

Specific examples of dopants 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 ₆ , SbCl ₅ , SbF ₅ , and the like. Of these, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

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 the inclusion of an additive in the hole transport layer leads to an improvement in the photoelectric conversion efficiency of the photoelectric conversion element, if the concentration of the dopant is too high, the durability of the photoelectric conversion element may be reduced.
Specific examples of the basic additive include 4-tert-butylpyridine (tBP), 2-picoline, and 2,6-lutidine, and among these, it is preferable to use 4-tert-butylpyridine. The basic additive may be used in combination with a 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.

[Opposite]
The counter electrode 5 is an electrode formed on the opposite side of the hole transport layer 4 to the photoelectric conversion layer 3, and is disposed opposite the conductive support 1 with the above-mentioned 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.

Specific examples of 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, it is preferable to use gold, silver, or a silver alloy, since 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, since they are less susceptible to sulfurization or chlorination and have high stability as a thin film. In addition, it is preferable that the counter electrode is a material that can be formed by a gas phase process such as deposition.
When a metal electrode is used as the counter electrode, the thickness thereof is preferably 10 nm or more, and more preferably 50 nm or more, in order to obtain good electrical conductivity.

In the photoelectric conversion element shown in Figure 1, the conductive support 1 serves as the cathode, and the counter electrode 5 serves as the anode. It is preferable to irradiate light such as sunlight (light used for photoelectric conversion) 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 via the electron transport layer to the conductive support, and the holes move via the hole transport layer to the counter electrode, causing a current to flow and functioning as a photoelectric conversion element.

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 that 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 an explanation and specific examples of the materials of each part and layer used in this embodiment, the corresponding description of the photoelectric conversion element shown in Figure 1 above can be referenced.

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 represents the current per ^cm2 flowing between the output terminals when the terminals are shorted, and the open circuit voltage represents the voltage between the output terminals when the terminals 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 dependent on the internal resistance. The photoelectric conversion efficiency is calculated as a percentage by multiplying the maximum output (W) divided by the light intensity (W) per ^cm2 by 100.

The photoelectric conversion element of the present invention can be applied to solar cells, various optical sensors, and the like. 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 the required number of photoelectric conversion elements, each of which contains a compound represented by general formula (1) in the hole transport layer, into a module and providing the required electrical wiring.

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 appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples. The compounds obtained in the synthesis examples were identified by ¹ H-NMR (1H-NMR (JNM-ECZ400S/L1 nuclear magnetic resonance apparatus manufactured by JEOL Ltd.).

[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 added to 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 city 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 (400 MHz, DMSO-d ₆ ): δ (ppm) = 6.37-6.39 (2H), 6.80-6.81 (2H), 6.90-6.92 (2H), 8.54 (1H).

A compound (0.5 g) of the following formula (2), [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) were charged into a reaction vessel, and degassed under reduced pressure. Tetrakistriphenylphosphinepalladium (0.08 g, manufactured by Kanto Chemical Co., Ltd.) was charged, and degassed under reduced pressure, and the mixture was stirred for 7 hours by heating and refluxing. After the aqueous layer of the reaction solution was separated and removed, the organic layer was distilled off the solvent under reduced pressure. Further, toluene was added to the obtained crude product, and after separation, the organic layer was distilled off the solvent under reduced pressure. The obtained crude product was purified using a silica gel column (toluene:ethyl acetate) to obtain a compound represented by the following formula (3) (yield: 0.6 g, yield: 52%).
^1H -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)

The compound of formula (3) (0.30 g), 55% sodium hydride (0.04 g, manufactured by Kanto Chemical Co., Ltd.), and DMF (10 mL) were added to 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 added thereto and stirred at 90°C for 4 hours. The solvent was distilled off from the reaction liquid under reduced pressure, and the obtained crude product was purified using a silica gel column (ethyl acetate:methanol). Further, purification was carried out by recrystallization (ethyl acetate:ethanol) to obtain a compound represented by the following formula (A-1) (yield: 0.22 g, yield: 62%).
^1H -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).

[Synthesis Example 2] Synthesis of Compound (A-70) The compound of the above formula (2) (1.50 g), 4-dimethylaminopyridine (0.107 g, manufactured by Kanto Chemical Co., Ltd.), di-tert-butyl dicarbonate (1.49 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and tetrahydrofuran (30 mL) were added to a reaction vessel and stirred at room temperature for 1 hour. The reaction solution was concentrated under reduced pressure as it was, and the residue was dissolved in ethyl acetate (50 mL), and then separated and washed with city water (100 mL). The obtained organic layer was dehydrated with magnesium sulfate, and the filtrate obtained by filtration was concentrated under reduced pressure. The concentrate was purified by reprecipitation (tetrahydrofuran:methanol), and the obtained solid was dried under reduced pressure to obtain a compound represented by the following formula (4) (yield: 1.58 g, yield: 83%).
¹ H-NMR (400 MHz, DMSO-d ₆ ): δ (ppm) = 7.42-7.49 (2H), 7.31-7.47 (4H), 1.42 (9H).

3,6-bis[N,N-bis(4-methoxyphenyl)amino]-9H-carbazole (0.930 g, manufactured by Tokyo Chemical Industry Co., Ltd.), the compound of the above formula (4) (0.930 g), cesium carbonate (0.668 g, manufactured by Kanto Chemical Industry Co., Ltd.), 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 liquid in two portions every 4 hours, and the mixture was stirred for 8 hours under heating and reflux. After cooling, the reaction liquid was filtered through Celite, and the obtained filtrate was concentrated under reduced pressure. The crude product was purified with 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 (400 MHz, DMSO-d ₆ ): 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).

A compound (0.450 g) of the following formula (5), 36% hydrochloric acid (6.5 mL), and ethyl acetate (10 mL) were added to a reaction vessel, and the mixture was stirred for 8 hours under heating and reflux. After the reaction solution was allowed to cool, a saturated aqueous sodium bicarbonate solution (100 mL) was added, followed by extraction and separation using tetrahydrofuran (50 mL). The obtained 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: ethyl acetate = 50: 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 (6) as a yellow solid (yield: 0.325 g, yield: 77%).
¹ H-NMR (400 MHz, DMSO-d ₆ ): 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).

The compound of formula (6) (0.251 g), 55% sodium hydride (0.03 g, manufactured by Kanto Chemical Co., Ltd.), and dimethylformamide (10 mL) were added to 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 added thereto and stirred at 80° C. for 3 hours. The solvent was distilled off from the reaction solution under reduced pressure, and the obtained 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 a compound represented by the following formula (A-70) as a yellow solid (yield: 0.230 g, yield: 83%).
^1H -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).

Synthesis Example 3 Synthesis of Compound (A-71) The compound (0.251 g) of the above formula (6), potassium tert-butoxide (0.017 g, manufactured by Kanto Chemical Co., Ltd.), and dimethylformamide (10 mL) were added to 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 added thereto and stirred at 80° C. for 6 hours. The reaction solution was distilled under reduced pressure to remove the solvent, and the obtained 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 a compound represented by the following formula (A-71) as a yellow solid (yield: 0.021 g, yield: 17%).
¹ H-NMR (400 MHz, DMSO-d ₆ ): 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).

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 Fuji Film Wako Pure Chemical Industries, Ltd.), toluene (5 mL), and tetrahydrofuran (5 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 Fuji Film Wako Pure Chemical Industries, Ltd.) were added to the reaction liquid in two portions every 4 hours, and the mixture was stirred for 12 hours under heating and reflux. After cooling, the reaction liquid was filtered through Celite, and the obtained filtrate was concentrated under reduced pressure. The crude product was purified with 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, 61%).
^1H -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).

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 the mixture was stirred for 2 hours under heating and reflux. After the reaction solution was allowed to cool, a saturated aqueous sodium bicarbonate solution (50 mL) was added, followed by extraction and separation using tetrahydrofuran (50 mL) and toluene (50 mL). The organic layer obtained 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 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 (9) as a yellow solid (yield: 0.233 g, yield: 58%).
¹ H-NMR (400 MHz, DMSO-d ₆ ): 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).

The compound of formula (9) (0.233 g), 55% sodium hydride (0.05 g, manufactured by Kanto Chemical Co., Ltd.), and dimethylformamide (10 mL) were added to 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 added thereto and stirred at 80° C. for 2 hours. The solvent was distilled off from the reaction solution under reduced pressure, and the obtained 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 a compound represented by the following formula (A-72) as a yellow solid (yield: 0.140 g, yield: 49%).
^1H -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).

[Example 1] Preparation of photoelectric conversion element using compound (A-1) 1
A glass plate with an ITO film (conductive support 1, manufactured by Geomatec Co., Ltd.) was ultrasonically cleaned with isopropyl alcohol and subjected to UV ozone treatment. After that, in a dry atmosphere with a relative humidity of 10% or less, the following layers were formed by a coating method.
First, a tin oxide colloidal solution (tin(IV) oxide, 15% in _H2O colloidal dispersion: manufactured by Alfa Aesar) and purified water were mixed at a volume ratio of 1:9 to form a tin oxide dispersion (electron transport layer coating solution) on the ITO film. Then, the film was 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 about 20 nm.
Next, formamidine hydroiodide (1M, manufactured by Tokyo Chemical Industry Co., Ltd.), lead (II) iodide (1.1M, manufactured by Tokyo Chemical Industry Co., Ltd.), methylamine hydrobromide (0.2M, manufactured by Tokyo Chemical Industry Co., Ltd.), and lead (II) bromide (0.2M, manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in a mixed solvent of dimethylformamide: dimethyl sulfoxide = 4: 1 (volume ratio), and a dimethyl sulfoxide solution of cesium iodide (1.5M, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to prepare a perovskite precursor solution. Here, the cesium iodide solution was added in an amount such that the amount of cesium charged was 5% in composition ratio. This perovskite precursor solution was dropped onto the tin oxide layer, and spin-coated while dropping chlorobenzene (0.3 mL) to form a perovskite precursor coating film. Subsequently, the resultant was heated on a hot plate at 100° C. for 1 hour to form a perovskite layer (photoelectric conversion layer 3) of Cs(MAFA)Pb(IBr) ₃ having a thickness of about 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 relative to compound (A-1), respectively. This hole transport layer coating solution was spin-coated on the Cs(MAFA)Pb(IBr) ₃ layer and then dried to form a hole transport layer 4 with a film thickness of about 200 nm.
Next, gold was evaporated to a thickness of 80 nm on the hole transport layer 4 by vacuum evaporation at a degree of vacuum of 1×10 ⁻⁴ Pa to form a gold electrode (counter electrode 5 ), thereby completing a photoelectric conversion element.

[Example 2] Preparation of photoelectric conversion element using compound (A-1) 2
A photoelectric conversion element was produced 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.

[Example 3] Preparation of photoelectric conversion element using compound (A-70) 1
A photoelectric conversion element was produced 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 at 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 at a concentration of 28 mM, and the dopant solution was added to compound (A-70) so that the amount of lithium bis(trifluoromethanesulfonyl)imide was 0.5 equivalents. Furthermore, 4-tert-butylpyridine was added to compound (A-70) so that the amount of lithium bis(trifluoromethanesulfonyl)imide was 3.3 equivalents to prepare a hole transport layer coating solution.

[Example 4] Preparation of photoelectric conversion element using compound (A-70) 2
A photoelectric conversion element was produced in the same manner as in Example 3, except that the dopant solution and 4-tert-butylpyridine were not added when preparing the coating solution for the hole transport layer.

[Example 5] Preparation of photoelectric conversion element using compound (A-71) 1
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).

[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 coating solution for the hole transport layer.

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), which is a standard hole transport material, was used as compound (B-1) instead of compound (A-1).

[Characteristics Evaluation 1]
The prepared photoelectric conversion elements were irradiated from the conductive support side with simulated sunlight (AM1.5, 1000 W/ ^m2 ) generated by a white light irradiation device (OTENTO-SUN SH model, manufactured by Bunkoukeiki Co., Ltd.), and the initial photoelectric conversion efficiency (PCE) measured with a source meter (Model 2400 Series Source Meter, manufactured by Keithley Co., Ltd.) is shown in Table 1. The short-circuit current, open-circuit voltage, and fill factor of each photoelectric conversion element are also shown in Table 1.

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

[Characteristics Evaluation 2]
The initial photoelectric conversion efficiency of the prepared photoelectric conversion element was measured by the same method as above, and then the photoelectric conversion element was sealed in a laminated bag with a zipper (AL-8, Seizo 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, and the photoelectric conversion efficiency (PCE) after 1000 hours of heating was measured again by the same method as above under irradiation with pseudo solar light. The retention rate (%) calculated from the following formula (a-1) using the obtained initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 1000 hours of heating is shown in Table 2.

The results in Table 2 show that the photoelectric conversion element of the example using the compound corresponding to general formula (1) as the hole transport material maintained a high photoelectric conversion efficiency even after 1000 hours of heating, compared to the photoelectric conversion element of Comparative Example 1 using compound (B-1), a conventional standard hole transport material, and exhibited excellent heat resistance.

By using the compound of the present invention as a hole transport material, a photoelectric conversion element and a solar cell with good photoelectric conversion efficiency can be realized. This makes it possible to efficiently provide electrical energy converted from solar energy as clean energy. In addition, hole transport materials containing the compound of the present invention can also be used in organic EL elements, image sensors, and the like. Therefore, the present invention has a high industrial applicability.

1 Conductive support 2 Electron transport layer 3 Photoelectric conversion layer 4 Hole transport layer 5 Counter electrode

Claims

A compound represented by the following general formula (1):
[In the formula, 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 atoms which may have a substituent,
X represents a monovalent cation other than a hydrogen ion.
R 2 to R 9 each independently represent
Hydrogen atoms,
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;
represents 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 atoms which may have a substituent.]
2. The compound according to claim 1, wherein R 1 is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent.
2. The compound according to claim 1, wherein the atom of R1 which is bonded to SO3X is a secondary carbon atom or a skeletal carbon atom of a benzene ring.
The compound according to claim 1, wherein at least one of R 2 to R 9 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. The compound according to claim 1, wherein at least one of R 2 to R 9 is a group having an optionally substituted diarylamino group.
The compound of claim 5, wherein the diarylamino group is substituted with a substituent bonded to a heteroatom.
The compound according to claim 5, wherein the group having an optionally substituted diarylamino group is an optionally substituted diarylamino group, an optionally substituted diarylaminoaryl group, or an optionally substituted diarylaminocarbazol-9-yl group.
A hole transport material comprising the compound according to any one of claims 1 to 7.
A photoelectric conversion element using the hole transport material according to claim 8.
A solar cell having the photoelectric conversion element according to claim 9.