Compound, hole transport material, and photoelectric conversion element using same

Abstract

This photoelectric conversion element using a compound represented by general formula (1) for a hole transport layer has excellent heat resistance. R1 is an aromatic hydrocarbon group, a heterocyclic group, or the like, and R2 to R29 are a hydrogen atom, an alkoxy group, or the like.

Description

Compound, hole transport material, and photoelectric conversion element using the same

[0001] The present invention relates to a compound, a hole transport material, and a photoelectric conversion element using the same.

[0002] In recent years, solar power generation has attracted attention as a clean energy source, and the development of solar cells has been actively pursued. Among these, the development of solar cells using perovskite materials in the photoelectric conversion layer (hereinafter referred to as perovskite solar cells) has attracted attention as a next-generation solar cell that can be manufactured at low cost using a solution process (for example, Patent Document 1, Non-Patent Documents 1 and 2).

[0003] Perovskite solar cells often use hole transport materials in their devices. The purposes of these materials include (1) enhancing the ability to selectively transport holes and thereby improving photoelectric conversion efficiency, and (2) protecting the perovskite material, which is susceptible to moisture and oxygen, by bonding with the perovskite photoelectric conversion layer (see, for example, Non-Patent Document 3). Spiro-OMeTAD, a spirobifluorene-based organic compound [comparison compound (B-1) listed below], is often used as a standard hole transport material, but there have been few reports of hole transport materials that contribute more significantly to photoelectric conversion characteristics than this material. Furthermore, since photoelectric conversion elements are expected to be used outdoors under sunlight irradiation, high heat resistance is required.

[0004] International Publication No. 2017 / 104792

[0005] J. Am. Chem. Soc., 2009, Vol. 131, pp. 6050-6051 Science, 2012, Vol. 388, pp. 643-647 Chem. Sci., 2019, 10, pp. 6748-6769

[0006] The problem to be solved by the present invention is to provide a compound useful as a hole transport material for a photoelectric conversion element that can extract current efficiently, and a photoelectric conversion element and a solar cell that use the compound in a hole transport layer and have high heat resistance.

[0007] In order to solve the above problems, the inventors conducted extensive research into improving photoelectric conversion characteristics, and as a result, they designed and developed a compound having a specific structure, and found that by using the compound as a hole transport layer in a photoelectric conversion element, it is possible to obtain a photoelectric conversion element and a perovskite solar cell that exhibit good photoelectric conversion characteristics and high heat resistance.

[0008] 1. A compound represented by the following general formula (1):

[0009]

[0010] [In the formula, R １ is a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted linear or branched alkyl group of 1 to 20 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 20 carbon atoms, an optionally substituted linear or branched alkoxy group of 1 to 20 carbon atoms, an optionally substituted aryloxy group of 6 to 30 carbon atoms, an optionally substituted amino group of 0 to 60 carbon atoms, an optionally substituted thio group of 0 to 20 carbon atoms, an optionally substituted monovalent aromatic hydrocarbon group of 6 to 30 carbon atoms, or an optionally substituted monovalent heterocyclic group of 5 to 30 ring atoms, ２ ~R ２９ each independently represents a hydrogen atom, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 12 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, an amino group of 0 to 20 carbon atoms which may have a substituent, or a thio group of 0 to 20 carbon atoms which may have a substituent; R １０ and R １１ , R ２４ and R ２５ may be bonded to each other to form a ring.

[0011] 2. In the general formula (1), R １is a halogen atom, an amino group having 0 to 60 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 20 carbon atoms which may have a substituent, or a monovalent heterocyclic group having 5 to 30 ring atoms which may have a substituent.

[0012] 3. In the general formula (1), R ６ ~R １５ and R ２０ ~R ２９ at least one of which is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent.

[0013] 4. In the general formula (1), R １０ and R １１ , R ２４ and R ２５ are compounds in which none of the compounds are bonded to each other to form a ring.

[0014] 5. A hole transport material comprising the compound described above.

[0015] 6. The hole transport material described above is used for a hole transport layer of a photoelectric conversion element.

[0016] 7. A photoelectric conversion element having a hole transport layer containing the compound described above.

[0017] 8. A solar cell using the photoelectric conversion element described above.

[0018] By using the compound according to the present invention and a hole transport layer using the compound, a photoelectric conversion element and a perovskite solar cell having high heat resistance can be obtained.

[0019] 1A and 1B are schematic cross-sectional views illustrating the configurations of photoelectric conversion elements according to examples of the present invention and comparative examples.

[0020] 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, compounds represented by general formula (1) and R １ ~R２９ Some or all of the hydrogen atoms present in the group represented by may be substituted with deuterium atoms. In this specification, "transparent" and "light-transmitting" refer to a transmittance of light to be used for photoelectric conversion of 50% or more, for example, 80% or more, for example, 90% or more, for example, 99% or more. The light transmittance can be measured using an ultraviolet-visible spectrophotometer.

[0021] The compound represented by the general formula (1) of the present invention will be specifically explained below, but the present invention should not be construed as being limited by these specific explanations.

[0022] In the general formula (1), R １ represents a hydrogen atom, a halogen atom, a hydroxyl group, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, an aryloxy group of 6 to 30 carbon atoms which may have a substituent, an amino group of 0 to 60 carbon atoms which may have a substituent, a thio group of 0 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group of 6 to 30 carbon atoms which may have a substituent, or a heterocyclic group of 5 to 30 ring atoms which may have a substituent.

[0023] In general formula (1), R １ The "halogen atom" represented by the formula (I) includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0024] In general formula (1), R １The number of carbon atoms in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms" in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from the range of 1 to 20, and may be selected from the range of 1 to 12, for example, or may be selected from the range of 1 to 6. Specific examples of the "straight-chain or branched alkyl group having 1 to 20 carbon atoms" include 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, and a decyl group.

[0025] In general formula (1), R 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 the formula (I) is selected from the range of 2 to 20, and may be selected from the range of 2 to 12, for example, or may be selected from the range of 2 to 6. Specific examples of the "straight-chain or branched alkynylene group having 2 to 20 carbon atoms" include ethenyl group (vinyl group), 1-propenyl group, 2-propenyl group (allyl group), 1-methylethenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, and straight-chain or branched alkenyl groups having 2 to 20 carbon atoms in which a plurality of these alkenyl groups are bonded.

[0026] In general formula (1), R １The number of carbon atoms in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms" in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (I) is selected from the range of 1 to 20, and may be selected from the range of 1 to 12, for example, or may be selected from the range of 1 to 6. Specific examples of the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms" include methoxy, ethoxy, propoxy, n-butoxy, n-pentyloxy, n-hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, isopropoxy, isobutoxy, s-butoxy, t-butoxy, isooctyloxy, and t-octyloxy.

[0027] In general formula (1), R １ For an explanation and specific examples of the aryl group bonded to the oxy group of the "aryloxy group having 6 to 30 carbon atoms" in the "aryloxy group having 6 to 30 carbon atoms which may have a substituent" represented by the formula (I), reference can be made to the description of the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms" below. Specific examples of the "aryloxy group having 6 to 30 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.

[0028] In general formula (1), R １The "amino group having 0 to 60 carbon atoms" in the "amino group having 0 to 60 carbon atoms which may have a substituent" represented by the formula (I) may be an unsubstituted amino group, a mono-substituted amino group, or a di-substituted amino group. Examples of the substituent in each substituted amino group include an alkyl group, an aryl group, and an acyl group. The hydrogen atom of each of these groups may be substituted with a substituent selected from the following substituent group A. For an explanation and specific examples of the alkyl group and the alkyl group constituting the acyl group, please refer to the above description of the "linear or branched alkyl group having 1 to 20 carbon atoms," and for an explanation and specific examples of the aryl group, please refer to the below description of the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms." Note that the two substituents bonded to the nitrogen atom of the di-substituted amino group do not bond together to form a cyclic structure, and groups having such a cyclic structure are considered to be included in the "heterocyclic group" described below in the present invention. The number of carbon atoms in the "amino group having 0 to 60 carbon atoms" is selected from the range of 0 to 60, and may be selected from the range of, for example, 0 to 30, for example, 2 to 11, or for example, 12 to 24. Specific examples of the "amino group having 0 to 60 carbon atoms" include an unsubstituted amino group (-NH ２ Examples of monosubstituted amino groups include methylamino, ethylamino, acetylamino, and phenylamino groups, and examples of disubstituted amino groups include dialkylamino groups such as dimethylamino and diethylamino groups, diarylamino groups such as diphenylamino groups, and acetylphenylamino groups. In one embodiment of the present invention, the "amino group having 0 to 60 carbon atoms which may be substituted" is an amino group having 0 to 60 carbon atoms which may be substituted with an alkyl group or an aryl group.

[0029] In general formula (1), R １The "thio group having 0 to 20 carbon atoms" in the "thio group having 0 to 20 carbon atoms, which may have a substituent" represented by the formula (I) may be an unsubstituted thio group (thiol group: -SH) or a substituted thio group in which the hydrogen atom of the thiol group has been substituted with a substituent. The number of carbon atoms in the substituted thio group is preferably in the range of 1 to 18, and may be, for example, in the range of 1 to 12, or may be, for example, in the range of 1 to 6. 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 following substituent group A. For an explanation and specific examples of the alkyl group that is a substituent of the thio group, please refer to the above description of the "linear or branched alkyl group having 1 to 20 carbon atoms," and for an explanation and specific examples of the aryl group, please refer to the below description of the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms." Typical examples of the substituted thio group include a linear or branched alkylthio group having 1 to 20 carbon atoms, which may have a substituent, and an arylthio group having 6 to 30 carbon atoms, which may have a substituent. Specific examples of the "thio group having 0 to 20 carbon atoms" include an unsubstituted thio group (thiol group: -SH), an alkylthio group (for example, a methylthio group, an ethylthio group, a propylthio group), and an arylthio group (for example, a phenylthio group, a biphenylthio group).

[0030] In general formula (1), R １The aromatic ring constituting the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms" in the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent" represented by the formula (I) may be a monocycle, a fused ring in which two or more rings are fused, or a linked ring in which two or more rings are linked by a single bond. When the aromatic ring is a fused ring, the number of fused rings is, for example, 2 to 6, e.g., 2 to 4. In one embodiment of the present invention, the aromatic ring contains two or more rings. When the aromatic ring is a fused ring, it becomes a "fused polycyclic aromatic group." When the aromatic ring is a linked ring, the number of linked rings is, for example, 2 to 6, e.g., 2 to 4. The number of carbon atoms forming the aromatic ring is selected from the range of 6 to 30, and may be selected from the range of 6 to 22 or 6 to 18, or may be selected from the range of 6 to 14 or 6 to 10. Specific examples of the "monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms" include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, an anthracenyl group (anthryl group), a phenanthryl group, a fluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, and a triphenylenyl group.

[0031] In general formula (1), R １The heterocycle constituting the "monovalent heterocyclic group having 5 to 30 ring atoms" in the "monovalent heterocyclic group having 5 to 30 ring atoms which may have a substituent" represented by the formula (I) may be a monocycle or a fused ring in which two or more rings are fused. In the case of a fused ring, the number of fused rings is, for example, 2 to 6, e.g., 2 to 4. Furthermore, the heterocycle may be an aromatic heterocycle or an aliphatic heterocycle. In one embodiment of the present invention, the heterocycle contains two or more rings. Examples of heteroatoms constituting the heterocycle include a nitrogen atom, an oxygen atom, and a sulfur atom. The number of ring atoms of the aromatic heterocycle is selected from the range of 5 to 30, and may be selected from the range of 5 to 18, for example. Specific examples of aromatic heterocyclic groups among "monovalent heterocyclic groups having 5 to 30 ring atoms" include pyridyl, pyrimidinyl, triazinyl, thienyl, furyl (furanyl), pyrrolyl, imidazolyl, pyrazolyl, triazolyl, quinolyl, isoquinolyl, naphthyldinyl, acridinyl, phenanthrolinyl, benzofuranyl, benzothienyl, oxazolyl, indolyl, carbazolyl, benzoxazolyl, thiazolyl, benzothiazolyl, quinoxalinyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothienyl, and carbonylyl groups. The bonding position of these groups is not particularly limited, and for example, pyridyl groups may be 2-pyridyl, 3-pyridyl, or 4-pyridyl (for example, 4-pyridyl can be selected). In one embodiment of the present invention, the aromatic heterocyclic group is bonded through a carbon atom. In another embodiment of the present invention, the aromatic heterocyclic group is bonded through a nitrogen atom. Specific examples of the aliphatic heterocyclic group among the "monovalent heterocyclic group having 5 to 30 ring atoms" include groups bonded through a nitrogen atom, such as a morpholino group, a pyrrolidino group, a piperidino group, and a piperazino group, and groups bonded through a carbon atom, such as a tetrahydrofuryl group and a tetrahydrothienyl group. In one embodiment of the present invention, R １ The "monovalent heterocyclic group having 5 to 30 ring atoms which may be substituted" is a monovalent aromatic heterocyclic group which is bonded via a nitrogen atom and has 5 to 30 ring atoms which may be substituted, or a monovalent aliphatic heterocyclic group which has 5 to 30 ring atoms which may be substituted. For example, R１ The "monovalent heterocyclic group having 5 to 30 ring atoms which may be substituted" which can be taken by R is a monovalent aromatic heterocyclic group which has 5 to 30 ring atoms which may be substituted and is bonded via a nitrogen atom, and can be divided into a group of substituted or unsubstituted carbazol-9-yl groups and other groups. For example, R １ The "monovalent heterocyclic group having 5 to 30 ring atoms which may have a substituent" which can be taken as the above is a monovalent aliphatic heterocyclic group having 5 to 30 ring atoms which may have a substituent, and in particular a monovalent aliphatic heterocyclic group having 5 to 30 ring atoms which may have a substituent and is bonded via a nitrogen atom.

[0032] In general formula (1), R １Examples of the "substituent" in "an optionally substituted linear or branched alkyl group having 1 to 20 carbon atoms," "an optionally substituted linear or branched alkenyl group having 2 to 20 carbon atoms," "an optionally substituted linear or branched alkoxy group having 1 to 20 carbon atoms," "an optionally substituted aryloxy group having 6 to 30 carbon atoms," "an optionally substituted amino group having 1 to 60 carbon atoms," "an optionally substituted thio group having 0 to 20 carbon atoms," "an optionally substituted monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms," or "an optionally substituted monovalent heterocyclic group having 5 to 30 ring atoms," each of which is represented by the formula (I) include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; cyano groups; hydroxyl groups; nitro groups; nitroso groups; carboxyl groups; phosphate groups; thioxo groups (>C=S); trimethylsilyl groups; methyl ester groups, ethyl ester groups, etc. a carboxylic acid ester group of the formula (I) or (II); a linear or branched alkyl group having 1 to 18 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, or a decyl group; an ethenyl group (vinyl group), a 1-propenyl group, a 2-propenyl group (allyl group), a 1-butenyl group, or a 2-butenyl group linear or branched alkenyl groups having 2 to 18 carbon atoms, such as a 1-pentenyl group, a 1-hexenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, or a 1-ethylethenyl group; 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; 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;Heterocyclic groups having 5 to 20 ring atoms 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; an unsubstituted amino group (—NH; ２ ); substituted amino groups having 1 to 18 carbon atoms, such as monosubstituted amino groups such as alkylamino groups (e.g., methylamino groups), acetylamino groups, and arylamino groups (e.g., phenylamino groups), or disubstituted amino groups such as diethylamino groups, 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, phenylthio groups, and biphenylthio groups (herein, these substituents are referred to as “Substituent Group A”). Only one or more of these “substituents” may be contained, and when more than one is contained, they may be the same or different. Furthermore, the hydrogen atoms of each of the substituents constituting Substituent Group A may be further substituted with a substituent selected from Substituent Group A.

[0033] In one embodiment of the present invention, R in general formula (1) １is a hydrogen atom, a halogen atom (e.g., a chlorine atom), a hydroxyl group, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, an aryloxy group of 6 to 30 carbon atoms which may have a substituent, an amino group of 0 to 60 carbon atoms which may have a substituent (e.g., an alkyl group or an aryl group), a thiol group, an alkylthio group of 1 to 20 carbon atoms which may have a substituent, a monovalent aromatic hydrocarbon group of 6 to 30 carbon atoms which may have a substituent, or a monovalent heterocyclic group of 5 to 30 ring atoms which may have a substituent (preferably a monovalent aromatic heterocyclic group which is bonded via a nitrogen atom of 5 to 30 ring atoms which may have a substituent, or a monovalent aliphatic heterocyclic group which is bonded via a nitrogen atom of 5 to 30 ring atoms which may have a substituent). １ is a halogen atom (for example, a chlorine atom), an amino group having 0 to 60 carbon atoms which may have a substituent, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent. １ is a halogen atom (for example, a chlorine atom), a monovalent heterocyclic group having 5 to 30 ring atoms which may have a substituent, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent.

[0034] In general formula (1), R ２ ~R ２９ each independently represents a hydrogen atom, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 12 carbon atoms which may have a substituent, a linear or branched alkoxy group of 1 to 20 carbon atoms which may have a substituent, an amino group of 0 to 20 carbon atoms which may have a substituent, or a thio group of 0 to 20 carbon atoms which may have a substituent.

[0035] In general formula (1), R ２ ~R ２９In the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (1), the "straight-chain or branched alkyl group having 1 to 20 carbon atoms" is, for example, １ Examples of the alkyl group include the same as the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by the following formula:

[0036] In general formula (1), R ２ ~R ２９ The "straight-chain or branched alkenyl group having 2 to 20 carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by the general formula (1) includes R １ Examples of the alkyl group include the same as the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by the following formula:

[0037] In general formula (1), R ２ ~R ２９ Specific examples of the "cycloalkyl group having 3 to 12 carbon atoms" in the "cycloalkyl group having 3 to 12 carbon atoms which may have a substituent" represented by the formula (1) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a 4-methylcyclohexyl group, and a 4-ethylcyclohexyl group. The number of carbon atoms in the cycloalkyl group may be selected, for example, within the range of 3 to 10.

[0038] In general formula (1), R ２ ~R ２９ In the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by the general formula (1), the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms" is represented by the general formula (1), １ Examples of the alkoxy group include the same as the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by the following formula:

[0039] In general formula (1), R ２ ~R ２９The "amino group having 0 to 20 carbon atoms" in the "amino group having 0 to 20 carbon atoms which may have a substituent" represented by the formula (1) is specifically an amino group having 0 to 20 carbon atoms, represented by the formula (1), １ Among the "amino groups having 0 to 60 carbon atoms which may have a substituent" represented by the following formula, the same as the "amino groups having 0 to 20 carbon atoms" can be mentioned.

[0040] In general formula (1), R ２ ~R ２９ The "thio group having 1 to 20 carbon atoms" in the "thio group having 1 to 20 carbon atoms which may have a substituent" represented by the following general formula (1) is specifically a thio group having 1 to 20 carbon atoms represented by the following general formula (1): １ Examples of the thio group include an optionally substituted thio group having 1 to 20 carbon atoms represented by the following formula:

[0041] In general formula (1), R ２ ~R ２９ Examples of the "substituent" in the "linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent", "linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 12 carbon atoms which may have a substituent", "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent", "amino group having 0 to 20 carbon atoms which may have a substituent", or "thio group having 0 to 20 carbon atoms which may have a substituent" represented by the general formula (1) include R １ Examples of the "substituent" include the same as those in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by the following formula:

[0042] In general formula (1), R １０ and R １１ , R ２４ and R ２５ may be bonded to each other to form a ring. For example, R １０ and R １１ , R ２４ and R ２５may be bonded to each other via a single bond, a bond via an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring. １０ and R １１ , R ２４ and R ２５ At least one pair of R １０ and R １１ are bonded to each other by a single bond, and R ２４ and R ２５ In a preferred embodiment of the present invention, R １０ and R １１ , R ２４ and R ２５ are not bonded to each other to form a ring. １０ and R １１ , R ２４ and R ２５ Compounds in which the groups are not bonded to each other to form a ring are preferred in that they have higher solubility in commonly used solvents than compounds in which the groups are bonded to each other to form a ring.

[0043] In general formula (1), R ２ ~R ２９ At least one of (preferably R ６ ~R １５ , R ２０ ~R ２９ At least one of, more preferably R ７ ~R ９ , R １２ ~R １４ , R ２１ ~R ２３ , R ２６ ~R ２８ at least one of) is R ２ ~R ２９ R is preferably a substituent that can be ２ ~R ２９ The number of substituents among R is preferably in the range of 1 to 12, and may be, for example, in the range of 1 to 8, or may be in the range of 4 to 8. When two or more are substituents, the substituents may be the same or different. Preferably, they are the same. In the present invention, R ８ , R １３ , R２２ and R ２７ Preferably, one or more selected from the following are substituents, and for example, all of them may be substituents. ２ ~R ２９ The substituents that R may have include a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a linear or branched alkylthio group having 1 to 20 carbon atoms which may have a substituent, and an amino group having 0 to 60 carbon atoms which may have a substituent (preferably a disubstituted amino group). ２ ~R ２９ The substituent taken by R is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent. ２ ~R ５ , R １６ ~R １９ is a hydrogen atom. In one aspect of the present invention, R ６ , R １０ , R １１ , R １５ , R ２０ , R ２４ , R ２５ , R ２９ is a hydrogen atom.

[0044] In general formula (1), one triarylamino group is bonded to any one of the 1st to 4th positions of the carbazole, and one triarylamino group is bonded to any one of the 5th to 8th positions of the carbazole. For example, one triarylamino group is bonded to the 2nd or 3rd position of the carbazole, and one triarylamino group is bonded to the 6th or 7th position of the carbazole. It is preferable that the bonding positions of the two carbazoles in general formula (1) are the same. In the present invention, the compound represented by general formula (1) is preferably a compound represented by the following general formula (2) in which triarylamino groups are substituted at the 3rd and 6th positions of the carbazole, or a compound represented by the following general formula (3) in which triarylamino groups are substituted at the 2nd and 7th positions of the carbazole. R in general formulas (2) and (3) ２ ~R ２９ is R in the general formula (1). ２ ~R ２９ is the same definition as

[0045]

[0046]

[0047] As the compound group represented by the general formula (1), R １ is a monovalent heterocyclic group having 5 to 30 ring atoms which may have a substituent. １ Compound group 1a, R is a monovalent aromatic heterocyclic group bonded via a carbon atom having 5 to 30 ring atoms which may have a substituent; １ Compound group 1b: R is a diarylamino group having 5 to 30 ring atoms which may have a substituent (wherein the two aryl groups are linked to each other to form a cyclic structure); １ Compound group 1c, where R is a monovalent aromatic heterocyclic group bonded via a nitrogen atom having 5 to 30 ring atoms which may have a substituent (excluding those belonging to compound group 1b); １ Compound group 1d, R is a monovalent aliphatic heterocyclic group bonded via a carbon atom having 5 to 30 ring atoms which may have a substituent; １ is a monovalent aliphatic heterocyclic group bonded via a nitrogen atom having 5 to 30 ring atoms, which may have a substituent. For example, in compounds 1a to 1e, the heterocyclic group in each group has a substituent. For example, in compounds 1a to 1e, the heterocyclic group in each group does not have a substituent and is unsubstituted. Each of compounds 1a to 1e may further satisfy at least one additional condition below. One of the additional conditions is that R ２ ~R ２９ 4 to 8 of these are R ２ ~R ２９ are possible substituents. One additional condition is that R ８ , R １３ , R ２２ and R ２７ At least one (e.g., all) of ２ ~R ２９ are possible substituents. One additional condition is that R ２ ~R ２９ is a substituent, and R ２ ~R ２９The substituent taken by R is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent. ２ ~R ２９ is a substituent, and R ２ ~R ２９ The substituent taken by R is a linear or branched alkylthio group having 1 to 20 carbon atoms which may have a substituent. ２ ~R ２９ is a substituent, and R ２ ~R ２９ is a disubstituted amino group having 2 to 60 carbon atoms which may have a substituent. One additional condition is that the compound has a structure represented by the above general formula (2). One additional condition is that the compound has a structure represented by the above general formula (3).

[0048] As the compound group represented by the general formula (1), R １ is a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent. １ Compound group 2a, in which R is an unsubstituted phenyl group; １ Compound group 2b, in which R is a substituted phenyl group; １ Compound group 2c, where R is an unsubstituted condensed aromatic hydrocarbon group; １ is a substituted fused aromatic hydrocarbon group. For example, the substituents of compounds 2b and 2d are selected from the above-mentioned substituent group A. For example, the substituents of compounds 2b and 2d are alkyl groups or aryl groups. Compounds 2a to 2d may each further satisfy at least one additional condition described in the description of compound group 1.

[0049] As the compound group represented by the general formula (1), R １ is an amino group having 0 to 60 carbon atoms which may have a substituent. １ Compound group 3a, in which R is an unsubstituted amino group; １ Compound group 3b, in which R is a monosubstituted amino group; １ Compound group 3c, where R is an optionally substituted diarylamino group;１ is a dialkylamino group optionally having a substituent. For example, the substituents of compounds 3b to 3d are selected from the above-mentioned substituent group A. For example, the substituents of compounds 3b to 3d are alkyl groups or aryl groups. Compounds 3a to 3d may each further satisfy at least one additional condition described in the description of compound group 1.

[0050] As the compound group represented by the general formula (1), R １ Compound group 4 can be represented by a compound group 4 in which R １ Compound group 4a, in which R is a fluorine atom １ Compound group 4b, in which R is a chlorine atom １ Compound group 4c, in which R is a bromine atom １ is an iodine atom. Each of the compounds of the compound group 4a to 4d may further satisfy at least one additional condition described in the description of the compound group 1.

[0051] As the compound group represented by the general formula (1), R １ is a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent. １ is a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent. １ is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent. １ is an aryloxy group having 6 to 30 carbon atoms which may have a substituent. １ is a thio group having 0 to 20 carbon atoms which may have a substituent. １ is a hydrogen atom. １is a hydroxyl group. Compounds 5 to 11 can each further satisfy at least one additional condition described in the description of compound 1.

[0052] Specific examples of the compound represented by the general formula (1) of the present invention are shown below, but the compounds represented by the general formula (1) that can be used in the present invention should not be construed as being limited by these specific examples. Furthermore, the following exemplary compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted, and are merely examples of possible isomers, and all other isomers are included. Furthermore, each may be a mixture of two or more isomers.

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] The compound of the present invention represented by the general formula (1) can be synthesized by known methods. Among the compounds represented by the general formula (1), the compounds represented by the general formula (2) and the compounds represented by the general formula (3) can be synthesized by the methods described below, for example.

[0061] The compound of the general formula (2) can be synthesized by a nucleophilic substitution reaction between cyanuric chloride or a 2,4-dichloro-1,3,5-triazine derivative and a 3,6-triarylamino-substituted carbazole represented by the following general formula (4).

[0062]

[0063] R in the above general formula (4) ２ ~R ２９ is R in the general formula (1).２ ~R ２９ is the same definition as

[0064] The compound of the general formula (3) can be synthesized by a nucleophilic substitution reaction between cyanuric chloride or a 2,4-dichloro-1,3,5-triazine derivative and a 2,7-triarylamino-substituted carbazole represented by the following general formula (5).

[0065]

[0066] R in the above general formula (5) ２ ~R ２９ is R in the general formula (1). ２ ~R ２９ is the same definition as

[0067] The compound of the present invention represented by the general formula (1) can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, or the like, recrystallization or crystallization using a solvent, or the like. Alternatively, it is effective to use a compound with increased purity by combining these methods. Furthermore, these compounds can be identified by nuclear magnetic resonance analysis (NMR).

[0068] Preferred embodiments of the photoelectric conversion element of the present invention will be described below.

[0069] <Photoelectric conversion element> Next, the photoelectric conversion element of the present invention will be described. The photoelectric conversion element of the present invention is characterized by having a hole transport layer containing a compound represented by general formula (1). For an explanation of the compound represented by general formula (1), the description in the above section <Compound represented by general formula (1)> can be referred to. The compound represented by general formula (1) has excellent hole transport properties and electron blocking properties, and therefore can be effectively used as a material for the hole transport layer of a photoelectric conversion element.

[0070] Preferred embodiments of the photoelectric conversion element will be described below, but the embodiments of the photoelectric conversion element of the present invention should not be construed as being limited by the embodiments shown below. In one embodiment of the present invention, 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. Hereinafter, each component and each layer of the photoelectric conversion element will be described using the photoelectric conversion element shown in FIG. 1 as an example.

[0071] [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 it for photoelectric conversion, and is, for example, a conductive substrate in which a film of a conductive material is formed on a transparent substrate. Specific examples of the conductive material used for the conductive support include 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 conductive transparent oxide semiconductors such as indium-tin composite oxide, and it is preferable to use tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc.

[0072] [Electron Transport Layer] The electron transport layer 2 is a layer containing a material (electron transport material) having a function of transporting electrons, and is disposed between the conductive support 1 and the photoelectric conversion layer 3 to transport electrons generated in the photoelectric conversion layer 3 to the conductive support 1 side. This improves the efficiency of electron migration from the photoelectric conversion layer to the conductive support. In addition to this function, the electron transport layer may also have a function of suppressing hole injection from the conductive support. The electron transport layer 2 may be formed adjacent to the conductive support 1, or another layer may be interposed between the conductive support 1 and the electron transport layer 2.

[0073] Specific examples of semiconductor materials used in the electron transport layer include tin oxide (SnO, SnO ２ , SnO ３ etc.), titanium oxide (TiO ２ etc.), tungsten oxide (WO ２ , W.O. ３ , W ２ O ３ etc.), zinc oxide (ZnO), niobium oxide (Nb ２ O ５ etc.), tantalum oxide (Ta ２ O ５ etc.), yttrium oxide (Y ２ O ３ etc.), strontium titanate (SrTiO ３ Examples of suitable semiconductor materials include metal oxides 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 semiconductor materials used in the electron transport layer include materials selected from tin oxide, titanium oxide, and zinc oxide, or a combination of two or more thereof.

[0074] Examples of materials for forming the electron transport layer include pastes (semiconductor pastes) containing fine particles of the semiconductor material. The semiconductor pastes may be commercially available products or may be prepared by dispersing fine powders of the semiconductor material in a solvent. Specific examples of solvents used in preparing the semiconductor paste include, but are not limited to, water; alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or as a mixture of two or more solvents.

[0075] Methods for dispersing semiconductor fine powder in a solvent include grinding the powder in a mortar or the like as needed, and then dispersing it in the solvent using a dispersing machine such as a ball mill, a paint conditioner, a vertical bead mill, a horizontal bead mill, an attritor, etc. When preparing a paste, it is preferable to add a surfactant or the like to prevent aggregation of the semiconductor fine particles, and it is also preferable to add a thickener such as polyethylene glycol to increase the viscosity.

[0076] The electron transport layer can be formed using a known film-forming method. That is, the electron transport layer can be formed using a coating method or a gas-phase process using a coating liquid containing a semiconductor material (e.g., a coating liquid for an electron transport layer such as a semiconductor paste). Specific examples include wet coating methods such as spin coating, inkjet printing, doctor blade printing, drop casting, squeegee printing, screen printing, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor printing, impregnation / coating, and curtain coating, in which the coating liquid for an electron transport layer is applied to a conductive substrate and then baked to remove solvents and additives. Other examples include gas-phase film-forming methods such as sputtering, vapor deposition, electrodeposition, electrodeposition, and microwave irradiation, in which a semiconductor material is formed into a film. Among these, the use of a coating method in which the prepared coating liquid for an electron transport layer is applied by spin coating is preferred, but is not limited thereto. The spin-coating conditions can be set appropriately. The atmosphere in which the film is formed is not particularly limited, and may be air or an inert atmosphere.

[0077] The film thickness of the electron transport layer is, for example, 5 nm to 200 nm, preferably 10 nm to 150 nm. Furthermore, when a dense electron transport layer is used, for example, from the viewpoint of further improving photoelectric conversion efficiency, the thickness of the electron transport layer is preferably usually 5 nm to 100 nm, more preferably 10 nm to 50 nm. In the present invention, when a porous (mesoporous) metal oxide is used in addition to the dense layer, the film thickness is preferably usually 20 nm to 200 nm, more preferably 50 nm to 150 nm.

[0078] [Photoelectric Conversion Layer] The photoelectric conversion layer 3 is a layer for converting light energy into electricity, and more specifically, a layer in which a charge separation state occurs due to light energy, thereby generating holes and electrons. In the photoelectric conversion element shown in Figure 1, the photoelectric conversion layer 3 is formed on the opposite side of the electron transport layer 2 from the conductive support 1.

[0079] An example of the photoelectric conversion layer is a layer formed of a perovskite material (perovskite layer). Here, the "perovskite material" is a material represented by the general formula ABX ３ 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. ＋ , Rb ＋ , Cs ＋ , C.H. ３ NH ３ ＋ (hereinafter, MA: methylammonium), NH=CHNH ２ ＋ (hereinafter referred to as FA: Formamidinium), CH ３ CH ２ NH ３ ＋ (hereinafter, EA: ethylammonium). Examples of divalent metal cations represented by B include Pb ２＋ , Sn ２＋ Examples of halogen ions represented by X include I － ,Br － Specific examples of perovskite materials include MAPbI ３ , FAPbI ３ , EAPbI ３ , CsPbI ３ , MASnI ３ , FASnI ３ , EASnI ３ , MAPbBr ３ , FAPbBr ３ , EAPbBr ３ , MASnBr ３ , FASnBr ３ , EASnBr ３ and further, (FAMA)Pb(IBr) ３ , K(FAMA)Pb(IBr) ３ , Rb(FAMA)Pb(IBr) ３ , Cs(FAMA)Pb(IBr) ３Also included are mixed cation type and mixed anion type perovskite materials such as the following: The photoelectric conversion layer may contain only one type selected from these perovskite materials, or may contain two or more types selected from these perovskite materials.

[0080] The photoelectric conversion layer may be composed solely of a perovskite material, or may contain other materials in addition to the perovskite material. Examples of other materials include a light absorber.

[0081] The perovskite layer is composed of halide AX and metal halide BX. ２ The perovskite precursor solution is applied to form a precursor coating film, and the precursor coating film is dried. ３ For example, specific examples of the halide AX include methylammonium halide, formamidine halide, and cesium halide, and specific examples of the metal halide BX include methylammonium halide, formamidine halide, and cesium halide. ２ Specific examples of the above include lead halides and tin halides.

[0082] From the viewpoint of precursor solubility, examples of solvents for the perovskite precursor solution include, but are not limited to, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone, etc. Furthermore, these solvents may be used alone or in combination of two or more. A preferred example of the solvent is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide. Furthermore, it is preferable to use a dehydrated solvent with a water content of 10 ppm or less. The solvent can be dehydrated using a molecular sieve or the like.

[0083] The coating step of the perovskite precursor solution is preferably carried out in a dry atmosphere, more preferably in a dry inert gas atmosphere such as a glove box. This prevents moisture from being mixed into the perovskite layer, allowing high-efficiency perovskite solar cells to be produced with good reproducibility. For the coating method, please refer to the description of the coating method for the electron transport layer coating solution described in the above section [Electron Transport Layer].

[0084] 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.

[0085] The thickness of the photoelectric conversion layer (perovskite layer) is preferably 50 to 1000 nm, more preferably 300 to 700 nm, which suppresses performance degradation due to defects or peeling of the photoelectric conversion layer, prevents the device resistance from becoming excessively high, and allows the photoelectric conversion layer to have sufficient light absorptivity.

[0086] [Hole Transport Layer] In the photoelectric conversion element shown in Fig. 1 , the hole transport layer 4 is a layer containing a material (hole transport material) having a function of transporting holes, and is disposed between the photoelectric conversion layer 3 and the counter electrode 5 to transport holes generated in the photoelectric conversion layer 3 to the counter electrode 5. This can improve the efficiency of hole transfer from the photoelectric conversion layer to the electrode. In addition to this function, the hole transport layer may also have a function of suppressing electron injection from the counter electrode.

[0087] 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 or more types selected from the group of compounds represented by general formula (1). By containing the compound represented by general formula (1), the hole transport layer can be made into a layer with high hole transport ability and excellent function of blocking electron migration from the counter electrode. Furthermore, in addition to the compound represented by general formula (1), the hole transport layer may contain 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.

[0088] 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 CuI and CuInSe. ２ Compound semiconductors containing monovalent copper such as CuS; GaP, NiO, CoO, FeO, Bi ２ O ３ , MoO ２ , Cr ２ O ３ Examples of organic hole transport materials include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA); diphenylamine derivatives; polysilane derivatives; and polyaniline derivatives. These second hole transport materials may be mixed into the hole transport layer, or a hole transport layer containing the second hole transport material may be laminated on top of a hole transport layer containing the compound represented by general formula (1). In one embodiment of the present invention, the hole transport layer is a single layer and contains only the compound represented by general formula (1) as the hole transport material.

[0089] For the method of forming the hole transport layer, the description of the method of forming the electron transport layer can be referred to. Furthermore, the following solvents can also be used for the coating solution for the hole transport layer. Specifically, examples of the solvent used for the coating solution for the hole transport layer include aromatic organic solvents such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, and nitrobenzene; alkyl halide organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, and dichloromethane; nitrile solvents such as benzonitrile and acetonitrile; tetrahydrofuran, dioxane, and diisopropyl ether solvents. Examples of suitable organic solvents include, but are not limited to, ether solvents such as isopropyl ether, c-pentyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate and propylene glycol monomethyl ether acetate; and alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, and 2-n-butoxyethanol. These solvents may be used alone or in combination of two or more. Among these, aromatic organic solvents and halogenated alkyl organic solvents are preferably used as the solvent for the hole transport layer-forming coating liquid.

[0090] The atmosphere during film formation of the hole transport layer is preferably a dry atmosphere. Furthermore, it is preferable to use a solvent that has been dehydrated so that the water content is 10 ppm or less in the coating solution. By preventing water contamination, highly efficient perovskite solar cells can be produced with good reproducibility. From the viewpoint of further improving photoelectric conversion efficiency, the thickness of the hole transport layer is preferably 5 nm to 500 nm, and more preferably 10 nm to 250 nm.

[0091] Additives that may be added to the hole transport layer include oxidizing agents (dopants) and basic compounds (basic additives). By adding these additives to the hole transport layer, the carrier concentration of the hole transport layer can be increased, thereby improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0092] Specific examples of dopants include lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, zinc bis(trifluoromethanesulfonyl)imide (II), copper bis(trifluoromethanesulfonyl)imide (II), magnesium bis(trifluoromethanesulfonyl)imide (II), calcium bis(trifluoromethanesulfonyl)imide (II), tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209), and NOSbF. ６ , SbCl ５ , SbF ５ Among these, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0093] The concentration of the dopant in the hole transport layer is preferably 2.0 equivalents or less, more preferably 0.5 equivalents or less, relative to 1 equivalent of the hole transport material. While incorporating an additive into the hole transport layer leads to improved photoelectric conversion efficiency of the photoelectric conversion element, if the dopant concentration is too high, the durability of the photoelectric conversion element may be reduced. Specific examples of basic additives include 4-tert-butylpyridine (tBP), 2-picoline, and 2,6-lutidine, and among these, 4-tert-butylpyridine is preferred. The basic additive may be used in combination with the dopant. The concentration of the basic additive in the hole transport layer is preferably 5 equivalents or less, more preferably 3.5 equivalents or less, relative to 1 equivalent of the hole transport material.

[0094] [Counter Electrode] The counter electrode 5 is an electrode formed on the side of the hole transport layer 4 opposite to the photoelectric conversion layer 3, and is disposed opposite the conductive support 1 with the electron transport layer 2, photoelectric conversion layer 3, and hole transport layer 4 sandwiched therebetween. The counter electrode functions as an anode that extracts holes transported from the photoelectric conversion layer via the hole transport layer. The counter electrode 5 may be provided adjacent to the hole transport layer 4, or an electron blocking layer made of an organic material or an inorganic compound semiconductor may be interposed between the hole transport layer 4 and the counter electrode 5.

[0095] Specific examples of materials constituting the counter electrode include metals such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, magnesium, chromium, cobalt, and copper, or alloys thereof. Among these, gold, silver, or a silver alloy is preferably used because it exhibits high electrical conductivity even in a thin film. Examples of silver alloys include silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper-palladium alloys, and silver-platinum alloys, because they are less susceptible to sulfurization or chlorination and have high stability as a thin film. In addition, the counter electrode is preferably made of a material that can be formed by a gas-phase process such as vapor deposition. When a metal electrode is used as the counter electrode, its film thickness is preferably 10 nm or more, more preferably 50 nm or more, to obtain good conductivity.

[0096] In the photoelectric conversion element shown in FIG. 1 , the conductive support 1 serves as the cathode, and the counter electrode 5 serves as the anode. 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 light and enters an excited state, generating electrons and holes. These electrons migrate to the conductive support via the electron transport layer, and the holes migrate to the counter electrode via the hole transport layer, thereby 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 the anode, and the counter electrode functions as the cathode. Electrons generated in the photoelectric conversion layer migrate to the counter electrode via the electron transport layer, and holes generated in the photoelectric conversion layer migrate to the conductive support via the hole transport layer. This allows current to be extracted to the outside. For descriptions and specific examples of the materials of each part and layer used in this embodiment, please refer to the corresponding descriptions of the photoelectric conversion element shown in FIG. 1 above.

[0097] When evaluating the performance (characteristics) of the photoelectric conversion element of the present invention, the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency are measured. The short-circuit current density is the current flowing between the output terminals when the output terminals are short-circuited. ２ The open-circuit voltage is the voltage between the output terminals when they are open. The fill factor is the maximum output (product of current and voltage) divided by the product of the short-circuit current density and the open-circuit voltage, and is mainly affected by the internal resistance. The photoelectric conversion efficiency is the ratio of maximum output (W) to 1 cm ２ The initial photoelectric conversion efficiency is calculated by dividing the efficiency by the light intensity (W) per unit area and multiplying the result by 100. If the initial photoelectric conversion efficiency of the photoelectric conversion element having the element configuration of the present invention is 10% or more, it can be determined that the photoelectric conversion efficiency is good.

[0098] The photoelectric conversion element of the present invention can be applied to solar cells, various optical sensors, etc. The solar cell to which the photoelectric conversion element of the present invention is applied is preferably a perovskite solar cell. A solar cell can be obtained by arranging a required number of photoelectric conversion elements containing a compound represented by general formula (1) in a hole transport layer as cells, modularizing the cells, and providing predetermined electrical wiring.

[0099] The features of the present invention will be specifically explained 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. Note that the identification of the compounds obtained in the synthesis examples is １ H-NMR ( １ H-NMR (Nuclear magnetic resonance spectrometer, JNM-ECZ400S / L1 model, manufactured by JEOL Ltd.) was used.

[0100] Synthesis Example 1 Synthesis of Compound (A-1) 3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (336 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (10 mL), and sodium hydride (19 mg, purity 55%, manufactured by Kanto Chemical Co., Inc.) were placed in a reaction vessel and stirred in an ice bath for 30 minutes. Furthermore, cyanuric chloride (25 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the reaction vessel and stirred at room temperature for 1 hour. After completion of the reaction, water (20 mL) was placed in the reaction vessel and the precipitated solid was collected by suction filtration. The crude product collected by filtration was purified using a silica gel column (toluene:ethyl acetate=20:1) to obtain compound (A-1) as a pale yellow powder (yield: 263 mg, 81%). １ H-NMR (400 MHz, DMSO-d6): δ (ppm) = 8.71 (6H), 8.34 (6H), 7.48 (12H), 7.38 (6H), 6.95 (24H), 6.83 (24H), 3.71 (36H).

[0101] Synthesis Example 2 Synthesis of Compound (A-2) 2,7-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (168 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (3 mL), and sodium hydride (10 mg, purity 55%, manufactured by Kanto Chemical Co., Inc.) were placed in a reaction vessel and stirred for 30 minutes in an ice bath. Furthermore, cyanuric chloride (15 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the reaction vessel and stirred at room temperature for 1 hour. After completion of the reaction, water (20 mL) was added, and the precipitated solid was collected by suction filtration. The crude product collected by filtration was purified using a silica gel column (toluene:ethyl acetate=20:1) to obtain compound (A-2) as a pale yellow powder (yield: 74 mg, 47%). １ H-NMR (400MHz, DMSO-d6): δ (ppm) = 9.15 (6H), 8.13 (6H), 7.58 (6H), 7.13 (12H), 6.84 (48H), 3.72 (36H).

[0102] Synthesis Example 3 Synthesis of Compound (A-3) 3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (143 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (3 mL), and sodium hydride (9 mg, purity 55%, manufactured by Kanto Chemical Co., Inc.) were placed in a reaction vessel and stirred for 30 minutes in an ice bath. Furthermore, 2,4-dichloro-6-phenyl-1,3,5-triazine (20 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the reaction vessel and stirred for 30 minutes at room temperature. After completion of the reaction, water (20 mL) was added, and the precipitated solid was collected by suction filtration. The collected crude product was purified using a silica gel column (toluene:ethyl acetate=6:1) to obtain compound (A-3) as a yellow powder (yield: 104 mg, 69%). １ H-NMR (400MHz, DMSO-d6): δ (ppm) = 8.82 (4H), 8.58 (2H), 8.46 (4H), 7.68 ( 3H), 7.63 (4H), 7.55 (8H), 6.95 (16H), 6.84 (16H), 6.78 (8H), 3.69 (24H).

[0103] Synthesis Example 4 Synthesis of Compound (A-4) 2,7-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (143 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (3 mL), and sodium hydride (10 mg, purity 55%, manufactured by Kanto Chemical Co., Inc.) were placed in a reaction vessel and stirred for 30 minutes in an ice bath. Furthermore, 2,4-dichloro-6-phenyl-1,3,5-triazine (20 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the reaction vessel and stirred at room temperature for 1.5 hours. After completion of the reaction, water (20 mL) was placed in the reaction vessel and the precipitated solid was collected by suction filtration. The crude product collected by filtration was washed with methanol and ethyl acetate to obtain compound (A-4) as a yellow powder (yield: 96 mg, 64%). １ H-NMR (400MHz, DMSO-d6): δ (ppm) = 9.15 (4H), 8.61 (2H), 8.05 (4H), 7.65 (1H), 7.57 (4H), 7.49 (2H), 7.34 (8H), 6.93 (16H), 6.85 (16H), 6.65 (8H), 3.72 (24H).

[0104] Synthesis Example 5 Synthesis of Compound (A-5) 3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (600 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (12 mL), and sodium hydride (34 mg, manufactured by Kanto Chemical Industry Co., Ltd.) were added to a reaction vessel and stirred for 30 minutes in an ice bath. The reaction system was cooled to −10° C., and then cyanuric chloride (23 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at −10° C. for 2 hours and at 0° C. for 90 minutes. After completion of the reaction, water (50 mL) was added, and the precipitated solid was collected by suction filtration. The collected crude product was purified using a silica gel column (toluene:ethyl acetate=50:1→30:1→10:1) to obtain compound (A-5) as a yellow powder (yield: 200 mg, 30%). １ H-NMR (400MHz, DMSO-d ６ ): δ (ppm) = 8.53 (4H), 8.22 (4H), 7.46 (12H), 6.77-6.93 (40H), 3.72 (24H)

[0105] Synthesis Example 6 Synthesis of Compound (A-16) 3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-carbazole (280 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), DMF (5 mL), and sodium hydride (16 mg, manufactured by Kanto Chemical Co., Inc.) were placed in a reaction vessel and stirred in an ice bath for 30 minutes. Furthermore, 2,4-dichloro-6-morpholino-1,3,5-triazine (40 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the reaction vessel and stirred at room temperature for 90 minutes. After completion of the reaction, water (50 mL) was added, and the precipitated solid was collected by suction filtration. The collected crude product was purified using a silica gel column (toluene:ethyl acetate=10:1) to obtain compound (A-16) as a pale yellow powder (yield: 99 mg, 33%). １ H-NMR (400MHz, DMSO-d ６ ): δ (ppm) = 8.65 (4H), 8.47 (4H), 7.53 (12H), 6.94 (16H), 6.84 (16H), 6.76 (8H), 3.99 (4H), 3.81-3.87 (4H), 3.70 (24H).

[0106] Example 1: Preparation of a photoelectric conversion element using compound (A-1) An ITO-coated glass (conductive support 1, manufactured by Geomatec Co., Ltd.) was ultrasonically cleaned with isopropyl alcohol and subjected to UV ozone treatment. Thereafter, in a dry atmosphere with a relative humidity of 10% or less, the following electron transport layer 2, photoelectric conversion layer 3, and hole transport layer 4 were formed by coating. A tin oxide colloidal solution (tin(IV) oxide, 15% in H ２ A tin oxide dispersion (electron transport layer coating solution) prepared by mixing tin oxide colloidal dispersion (manufactured by Alfa Aesar) and purified water in a 1:1 (volume ratio) was spin-coated onto the ITO film, followed by heating on a hot plate at 150°C for 30 minutes to form a tin oxide layer (electron transport layer 2) with a thickness of approximately 20 nm.

[0107] Formamidine hydroiodide (1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), lead(II) iodide (1.1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), methylamine hydrobromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.), and lead(II) bromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in a mixed solvent of dimethylformamide and dimethyl sulfoxide at a volume ratio of 4:1. A dimethyl sulfoxide solution of cesium iodide (1.5 M, manufactured by Tokyo Chemical Industry Co., Ltd.) was then added to prepare a perovskite precursor solution. The cesium iodide solution was added in an amount such that the cesium content was 5% by composition ratio. In a dry atmosphere with a relative humidity of 10% or less, the prepared perovskite precursor solution was added dropwise onto a tin oxide layer, and spin-coated while adding chlorobenzene (0.35 mL) dropwise to form a perovskite precursor coating. Then, by heating on a hot plate at 100°C for 1 hour, a Cs(MAFA)Pb(IBr) film with a thickness of approximately 500 nm was obtained. ３ A perovskite layer (photoelectric conversion layer 3) was formed.

[0108] As a dopant, lithium bis(trifluoromethanesulfonyl)imide was dissolved in acetonitrile at a concentration of 1.8 M to prepare a dopant solution. Compound (A-1), the hole transport material obtained in Synthesis Example 1, was dissolved in chlorobenzene at 70°C at a concentration of 30 mM. 4-tert-butylpyridine was added thereto so that the amount was 3.3 equivalents relative to compound (A-1). Furthermore, the dopant solution was added so that lithium bis(trifluoromethanesulfonyl)imide was added so that the amount was 0.5 equivalents relative to compound (A-1), to prepare a hole transport layer coating solution. Cs(MAFA)Pb(IBr) ３ The hole transport layer coating solution was spin-coated onto the layer (photoelectric conversion layer 3) to form a hole transport layer 4 having a thickness of about 200 nm.

[0109] On the hole transport layer, a vacuum of 1×10 was applied by vacuum deposition. －４ A gold electrode (counter electrode 5) was formed by depositing a gold film of about 80 nm at about Pa, and a photoelectric conversion element was fabricated.

[0110] Example 2 Preparation of Photoelectric Conversion Element Using Compound (A-3) A photoelectric conversion element was prepared in the same manner as in Example 1, except that instead of compound (A-1), compound (A-3) was dissolved in chlorobenzene at room temperature to a concentration of 50 mM and the solution was spin-coated.

[0111] Example 3 Preparation of Photoelectric Conversion Element Using Compound (A-4) A photoelectric conversion element was prepared in the same manner as in Example 1, except that instead of compound (A-1), compound (A-4) was dissolved in chlorobenzene at room temperature to a concentration of 50 mM and the solution was spin-coated.

[0112] Example 4 Preparation of Photoelectric Conversion Element Using Compound (A-5) A photoelectric conversion element was prepared in the same manner as in Example 1, except that instead of compound (A-1), compound (A-5) was dissolved in chlorobenzene at room temperature to a concentration of 27 mM and the solution was spin-coated.

[0113] Example 5 Preparation of Photoelectric Conversion Element Using Compound (A-16) A photoelectric conversion element was prepared in the same manner as in Example 1, except that instead of compound (A-1), compound (A-16) was dissolved in chlorobenzene at room temperature to a concentration of 26 mM and the solution was spin-coated.

[0114] Comparative Example 1 Preparation of Photoelectric Conversion Element Using Comparative Compound (B-1) A photoelectric conversion element was prepared in the same manner as in Example 1, except that Spiro-OMeTAD (manufactured by Sigma-Aldrich), a standard hole transport material represented by the following formula (B-1), was used in place of compound (A-1), dissolved in chlorobenzene at room temperature to a concentration of 70 mM.

[0115]

[0116] [Evaluation of Characteristics] Each of the photoelectric conversion elements fabricated in Examples 1 to 5 and Comparative Example 1 was irradiated with simulated sunlight (AM 1.5, 1000 W / m) generated by a white light irradiation device (OTENTO-SUN SH model, manufactured by Bunkoukeiki Co., Ltd.). ２) was irradiated from the conductive support side of the photoelectric conversion element, and the current-voltage characteristics were measured using a source meter (KEITHLEY Corporation, Model 2400 Series Source Meter) to obtain the initial photoelectric conversion efficiency. After measuring the current-voltage characteristics, the photoelectric conversion element was sealed in a resealable laminate bag (Seisan Nippon Co., Ltd., AL-8) in a glove box under a nitrogen atmosphere. The sealed photoelectric conversion element was placed in a vacuum constant temperature dryer (Tokyo Rikakikai Co., Ltd., VOS-310C) and stored at 85 ° C. for 1,000 hours, and the current-voltage characteristics were measured again under simulated sunlight irradiation to obtain the photoelectric conversion efficiency after 1,000 hours of heating. Using the obtained initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 1,000 hours of heating, the retention rate (%) calculated from the following formula (a-1) is shown in Table 1.

[0117]

[0118] From the results in Table 1, it was found that the photoelectric conversion elements using the compounds (A-1), (A-3), (A-4), (A-5), and (A-16) corresponding to general formula (1) as hole transport materials exhibited a higher retention rate in photoelectric conversion efficiency after 1,000 hours of heating compared to the photoelectric conversion element using the standard hole transport material (B-1), and therefore had excellent heat resistance. Furthermore, the photoelectric conversion element using compound (A-2) as the hole transport material showed no decrease in photoelectric conversion efficiency after 1,000 hours of heating, maintained a high photoelectric conversion efficiency compared to the photoelectric conversion element using the standard hole transport material, and exhibited excellent heat resistance.

[0119] By using the compound represented by general formula (1) as a hole transport material, a photoelectric conversion element having good photoelectric conversion efficiency and excellent heat resistance can be formed, which can efficiently convert solar energy into electrical energy, and can provide clean energy as a solar cell. Therefore, the present invention has high industrial applicability.

[0120] REFERENCE SIGNS LIST 1 conductive support 2 electron transport layer 3 photoelectric conversion layer 4 hole transport layer 5 counter electrode

Claims

1. A compound represented by the following general formula (1): 【Chemistry 1】 [In the formula, R １ represents a hydrogen atom, a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 20 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 alkoxy group having 1 to 20 carbon atoms which may have a substituent; an aryloxy group having 6 to 30 carbon atoms which may have a substituent; an amino group having 0 to 60 carbon atoms which may have a substituent; a thio group having 0 to 20 carbon atoms which may have a substituent; a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent, or an optionally substituted monovalent heterocyclic group having 5 to 30 ring atoms, R ２ ~R ２９ are each independently hydrogen atoms, a linear or branched alkyl group having 1 to 20 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 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; an amino group having 0 to 20 carbon atoms which may have a substituent, or It represents a thio group having 0 to 20 carbon atoms which may have a substituent.]

2. In the general formula (1), R １ is a halogen atom, an optionally substituted amino group having 0 to 60 carbon atoms, an optionally substituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or an optionally substituted monovalent heterocyclic group having 5 to 30 ring atoms.

3. In the general formula (1), R ６ ~R １５ and R ２０ ~R ２９ 2. The compound according to claim 1, wherein at least one of the groups is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent.

4. A hole transport material comprising the compound according to any one of claims 1 to 3.

5. The hole transport material according to claim 4, which is used for a hole transport layer of a photoelectric conversion element.

6. A photoelectric conversion element having a hole transport layer containing the compound according to any one of claims 1 to 3.

7. A solar cell using the photoelectric conversion element according to claim 6.

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