TW202428568A - Compound, hole transport material, and photoelectric conversion element using said compound - Google Patents

Abstract

The present invention relates to a compound represented by the following general formula, which is useful as a hole transport material for a photoelectric conversion device: ^R1 is an alkylene group or the like, and ^R2 to ^R9 are a hydrogen atom, an amine group, an aromatic hydrocarbon group or the like.

Description

Compound, hole transport material and photoelectric conversion element using the 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 attracted much attention as a clean energy source, and solar cells are being actively developed. Among them, as a low-cost next-generation solar cell that can be manufactured by a solution process, the development of a solar cell that uses calcium-titanium materials for the photoelectric conversion layer (hereinafter referred to as a "calcium-titanium type solar cell") has attracted attention (for example, patent document 1, non-patent documents 1-2). In calcium-titanium type solar cells, a layer formed of a hole transport material is often provided in the element. The purpose of using hole transport materials includes (1) improving the photoelectric conversion efficiency and (2) protecting calcium-titanium materials that are easily affected by moisture and oxygen (for example, non-patent literature 3-4). As is known, Spiro-OMeTAD is mostly used as a standard organic hole transport material, and there are few reports on organic hole transport materials that contribute more to photoelectric conversion properties than this material. [Chemistry 1]

[Prior technical literature] [Patent literature] [Patent literature 1] International Publication No. 2017/104792

[Non-patent document] [Non-patent document 1] Journal of the American Chemical Society, 2009, Vol. 131, pp. 6050-6051 [Non-patent document 2] Science, 2012, Vol. 388, pp. 643-647 [Non-patent document 3] Chem. Sci., 2019, 10, pp. 6748-6769 [Non-patent document 4] Adv. Funct. Mater., 2019, 1901296 [Non-patent document 5] J. Am. Chem. Soc., 2018, 140, 48, 16720-16730

(Invent the problem you want to solve)

When an organic compound is used as a hole transport material, it is known to add a dopant to the hole transport layer in order to reduce the 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, when a dopant is used, there are reports that moisture absorption by the dopant, corrosion of the photoelectric conversion layer, and degradation of the hole transport layer due to volatility may occur, which may lead to a decrease in the durability of the device (for example, non-patent document 5). Therefore, it is desired to develop a photoelectric conversion element that exhibits high photoelectric conversion characteristics and durability even when the hole transport layer does not contain a dopant and 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 to provide a photoelectric conversion element and a solar cell that exhibit excellent photoelectric conversion characteristics. (Technical means for solving the problem)

To solve the above problems, the inventors conducted intensive research and found that by using a compound having a structure in which a sulfonic acid base group is linked to a moiety skeleton as a hole transport material, a photoelectric conversion element or solar cell having good photoelectric conversion efficiency and high durability can be obtained. The present invention is proposed based on such a finding and specifically has the following structure.

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

In the formula, ^R1 is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, a cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, an arylene group having 6 to 36 carbon atoms which may have a substituent, or a divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent ^, and X represents a monovalent cation other than a hydrogen ion. ⁹ each independently represents a hydrogen atom, an optionally substituted linear or branched alkyl group having 1 to 18 carbon atoms, an optionally substituted linear or branched alkenyl group having 2 to 20 carbon atoms, an optionally substituted linear or branched alkynyl group having 2 to 20 carbon atoms, a optionally substituted cycloalkyl group having 3 to 12 carbon atoms, an optionally substituted linear or branched alkoxy group having 1 to 20 carbon atoms, a optionally substituted A cycloalkoxy group having 3 to 10 atoms, 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 thiol 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 as described in [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 as described in [1] or [2], wherein the atom of R ¹ bonded to SO ₃ X is a secondary carbon atom or a carbon atom constituting the skeleton of a benzene ring. [4] The compound as described in 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 as described in any one of [1] to [4], wherein at least one of R ² to R ⁹ is a group having a diaromatic amino group which may have a substituent. [6] The compound as described in [5], wherein the diaromatic amino group is substituted by a substituent bonded via a heteroatom. [7] The compound as described in [5], wherein the group having a diaromatic amino group which may have a substituent is a diaromatic amino group which may have a substituent, a diaromatic amino aryl group which may have a substituent, or a diaromatic amino carbazole-9-yl group which may have a substituent. [8] A hole transport material comprising a compound as described in any one of [1] to [7]. [9] A photoelectric conversion element using the hole transport material as described in [8]. [10] A solar cell having the photoelectric conversion element as described in [9]. (Compared with the effect of the prior art)

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 of a photoelectric conversion element, a photoelectric conversion element and a solar cell having good photoelectric conversion efficiency and high durability can be obtained.

The content of the present invention is described in detail below. The description of the constituent elements described below is sometimes based on representative embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments or specific examples. Furthermore, in this specification, the numerical range represented by "to" refers to a range that includes the numerical values recorded before and after "to" as the lower limit and upper limit. In addition, part or all of the hydrogen atoms present in the compound represented by the general formula (1) and the group represented by R ¹ to R ⁹ can be replaced by deuterium atoms. In this specification, "transparency" and "light transmittance" refer to a light transmittance of 50% or more for photoelectric conversion, for example, 80% or more, 90% or more, or 99% or more. The light transmittance can be measured by an ultraviolet-visible spectrophotometer.

<Compounds represented by the general formula (1)> The compounds of the present invention have the structure represented by the general formula (1) above. In the general formula (1), ^R1 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 "linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent" represented by ^R1 is an integer selected from 1 to 18, for example, it can be selected from the range of 1 to 12, for example, it can also be selected from the range of 1 to 6. Specifically, the "linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent" includes a divalent group obtained by removing one hydrogen atom from an alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, dibutyl, tertiary butyl, n-pentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, and decyl, 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 (preferably the former divalent group).

In the general formula (1), the number of carbon atoms in the "linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent" represented by ^R1 is an integer selected from 2 to 20, for example, it can be selected from the range of 2 to 12, for example, it can also be selected from the range of 2 to 6. Specific examples of the “linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent” include vinyl, 1-propenyl, allyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, isopropenyl, isobutenyl, or a divalent group obtained by removing one hydrogen atom from a linear or branched alkenyl group having 2 to 20 carbon atoms obtained by plural bonds among these alkenyl groups, 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 (preferably the first divalent group).

In the 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 ^R1 is selected from integers of 2 to 20, for example, can be selected from the range of 2 to 12, for example, can also be selected from the range of 2 to 6. Specific examples of the “linear or branched alkynyl 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 ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 1-methyl-2-propynyl, 1-pentynyl, 2-pentynyl, 1-methyl-n-butynyl, 2-methyl-n-butynyl, 3-methyl-n-butynyl, and 1-hexynyl, 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 (preferably the former divalent groups).

In the general formula (1), the number of carbon atoms in the "cyclolene alkyl group having 3 to 12 carbon atoms" in the "cyclolene alkyl group having 3 to 12 carbon atoms which may have a substituent" represented by ^R1 is selected from integers of 3 to 12, for example, can be selected from the range of 3 to 6. Specific examples of the "cyclolene alkyl group having 3 to 12 carbon atoms which may have a substituent" include a divalent group obtained by removing one hydrogen atom from a cycloalkyl group such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, and cyclododecyl, and a divalent group 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 (preferably the former divalent group).

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 ^R1 may be a monocyclic ring, a condensed ring formed by condensing two or more rings, or a linked ring formed by linking two or more rings via a single bond. In the case of a condensed ring, the number of condensed rings is, for example, 2 to 6, and another example is 2 to 4. In the case of a linked ring, the number of linked rings is, for example, 2 to 6, and another example is 2 to 4. The number of carbon atoms in the aromatic ring is an integer selected from 6 to 36, and may be, for example, selected from the range of 6 to 22, and another example is 6 to 18, and may also be, for example, selected from the range of 6 to 14, and 6 to 10. Specifically, the "aryl group having 6 to 36 carbon atoms which may have a substituent" includes a divalent group obtained by removing one hydrogen atom from a monovalent aromatic hydrocarbon group (aryl group) such as phenyl, biphenyl, terphenyl, naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl, and triphenyl, and a divalent group 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 (preferably the former divalent group).

In the general formula (1), the heterocyclic ring constituting the "divalent heterocyclic group having 5 to 36 ring-forming atoms" in the "divalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent" represented by ^R1 may be a monocyclic ring or a condensed ring formed by condensing two or more rings. In the case of a condensed ring, the number of condensed rings is, for example, 2 to 6, or 2 to 4. Furthermore, the heterocyclic ring may be an aromatic heterocyclic ring or an aliphatic heterocyclic ring. Examples of heteroatoms constituting the heterocyclic ring include nitrogen atoms, oxygen atoms, and sulfur atoms. The number of carbon atoms in the aromatic heterocyclic ring is selected from integers of 5 to 36, for example, can be selected from the range of 5 to 30 or 5 to 18. Specifically, the "divalent heterocyclic group having 5 to 36 ring atoms" includes pyridyl, pyrimidinyl, trioxazolyl, thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, quinolyl, isoquinolyl, naphthyridinyl, acridinyl, phenanthrinyl, benzofuranyl, benzothiophenyl, oxazolyl, indolyl, carbazolyl, benzoxazolyl, A divalent group obtained by removing one hydrogen atom from a monovalent heterocyclic group such as thiazolyl, benzothiazolyl, quinolinyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothiophenyl, and carbonyl, 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 (preferably the former divalent group).

In the general formula (1), R ^{The “substituent”} in the “straight or branched alkylene group having 1 to 18 carbon atoms which may have a substituent”, “straight or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent”, “straight 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 1 specifically includes halogen atoms such as fluorine, chlorine, bromine and iodine atoms; cyano; hydroxyl; nitro; nitroso; carboxyl; phosphate; carboxylate groups such as methyl ester and ethyl ester; methyl, ethyl, n-propyl, isopropyl , straight-chain or branched-chain alkyl groups having 1 to 18 carbon atoms, such as n-butyl, isobutyl, dibutyl, tertiary butyl, n-pentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, decyl, etc.; vinyl, 1-propenyl, allyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, isopropenyl, isobutenyl, etc. a linear or branched alkenyl group having 2 to 20 atoms; a linear or branched alkoxy group having 1 to 18 carbon atoms, such as methoxy, ethoxy, propoxy, tert-butyloxy, pentyloxy, hexyloxy, etc.; a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, such as phenyl, naphthyl, anthracenyl, phenanthrenyl, pyrenyl, etc.; a pyridyl, pyrimidyl, trithienyl, thienyl, furyl (furyl, furanyl), pyrrolyl, imidazolyl, pyrazolyl, triazolyl, quinolyl, isoquinolyl, naphthyridinyl, acridinyl, phenanthrinyl, benzofuranyl, benzothiophenyl, oxazolyl, indolyl, carbazolyl, benzoxazolyl, thiazolyl, benzothiazolyl, quinolinyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothiophenyl, carbonyl and the like; unsubstituted amino group (-NH ₂ ); a substituted amino group having 1 to 18 carbon atoms as a monosubstituted amino group such as an alkylamino group (e.g., ethylamino group), an acetylamino group, an aromatic amino group (e.g., an anilino group), or a disubstituted amino group such as a dialkylamino group (e.g., diethylamino group), a diaromaticamino group (e.g., diphenylamino group), an acetylanilino group; an unsubstituted thiol group (thiol group: -SH); a substituted thiol group having 1 to 18 carbon atoms such as a methylthiol group, an ethylthiol group, a propylthiol group, a hex-5-ene-3-thiol group, a benzenethiol group, a biphenylthiol group; etc. (hereinafter, such substituents are referred to as "substituent group A"). Each group represented by R ¹ may contain only one substituent selected from the substituent group A, or may contain a plurality of substituents, and when a plurality of substituents are contained, they may be the same or different from each other. Furthermore, the hydrogen atom of each substituent constituting the substituent group A may be further substituted with a substituent selected from the substituent group A.

^R1 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 by an alkenyl group, an alkynyl group, a cycloalkyl group or an aryl group. ^R1 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 ^R1 bonded to _SO3X is preferably a secondary carbon atom or a carbon atom constituting the skeleton of the benzene ring.

X in the sulfonic acid alkali group (-SO ₃ X) of the 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 thereto.

Specific examples of the alkaline metal ions include lithium ions, sodium ions, potassium ions, aluminum ions, cesium ions, and copper ions, and sodium ions, potassium ions, aluminum ions, and cesium ions are preferred.

Specific examples of the ammonium ion which 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, tertiary butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidine ion, formamidine ion, acetamidine ion, imidazole ion, tri-n-butylammonium ion, tetra-n-butylammonium ion, and the like.

Examples of the phosphonium ion which may have a substituent include ethylphosphonium ion, isopropylphosphonium ion, n-propylphosphonium ion, isobutylphosphonium ion, n-butylphosphonium ion, tertiary butylphosphonium ion, dimethylphosphonium ion, diethylphosphonium ion, phenylphosphonium ion, benzylphosphonium ion, and phosphonium ion in which the nitrogen atom of the above-mentioned ammonium ion is replaced by a phosphorus atom.

In the general formula (1), ^R2 to ^R9 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, an 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, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, or a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent. A cycloalkoxy group having 3 to 10 atoms, 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 thiol 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 the general formula (1), the carbon number of the "straight or branched alkyl group having 1 to 18 carbon atoms" in the "straight or branched alkyl group having 1 to ¹⁸ carbon atoms which may have a substituent" represented by R ² to R 9 is an integer selected from 1 to 18, for example, it can be selected from the range of 1 to 12, for example, it can also be selected from the range of 1 to 6. For specific examples of the "straight or branched alkyl group having 1 to 18 carbon atoms", the specific examples of the ^alkyl group (alkyl group before removing one hydrogen atom) listed in the description of the "straight or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R 1 above can be referred to.

In the general formula (1), the number of carbon atoms in the " ^straight or ^branched alkenyl group having 2 to 20 carbon atoms" in the "straight or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by R2 to R9 is an integer selected from 2 to 20, for example, it can be selected from the range of 2 to 12, for example, it can also be selected from the range of 2 to 6. For specific examples of the "straight or branched alkenyl group having 2 to 20 carbon atoms", the specific examples of the ^alkenyl group (alkenyl group before removing one hydrogen atom) listed in the description of the "straight or branched alkenylene group having 2 to 20 carbon atoms" represented by R1 above can be referred to.

In the general formula (1), the number of carbon atoms in the " ^straight or branched alkynyl group having 2 to 20 carbon atoms" in the "straight or branched alkynyl group having 2 to 20 carbon atoms ^which may have a substituent" represented by R2 to R9 is an integer selected from 2 to 20, for example, it can be selected from the range of 2 to 12, for example, it can also be selected from the range of 2 to 6. For specific examples of the "straight or branched alkynyl group having 2 to 20 carbon atoms", the specific examples of the alkynyl ^group (alkynyl group before removing one hydrogen atom) listed in the description of the "straight or branched alkynyl group having 2 to 20 carbon atoms" in R1 above can be referred to.

In the general formula (1), the carbon number of 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, for example, can be selected from the range of 3 to 6. Specific examples of the "cycloalkyl group having 3 to 10 carbon atoms" can refer to the specific examples of the cycloalkyl group (cycloalkyl group before removing one hydrogen atom) listed in the description of the "cycloalkyl group having 3 to 12 carbon atoms" in R ¹ above.

In the general formula (1), the carbon number of the "linear or branched alkoxy group having 1 to 20 carbon atoms" in the "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by ^{R2 to} R9 is an integer selected from 1 to 20, for example, it can be selected from the range of 1 to 12, for example, it can also be selected from the range of 1 to 6. Specific examples of the "linear 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, di-butoxy, tertiary butoxy, isooctyloxy, tertiary octyloxy and the like.

In the general formula ( ¹ ), the carbon number of the "linear or branched cycloalkoxy group having 3 to 10 carbon atoms" in the "linear or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by ^R2 to R9 is an integer selected from 3 to 10, for example, 3 to 6. Specific examples of the "linear or branched cycloalkoxy group having 3 to 10 carbon atoms" include cyclopropoxy, cyclobutoxy, cyclopentyloxy, cyclohexyloxy and the like.

In the general formula (1), for the explanation and specific examples of ^the aryl ^group bonded to the oxy group in 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 the following R 2 to R 9. Specific examples of the "aryloxy group having 6 to 36 carbon atoms" include phenoxy, tolyloxy, biphenyloxy, terphenyloxy, naphthoxy, anthryloxy, phenanthrenoxy, fluorenyloxy, and indenyloxy.

In the general formula (1), the carbon number of the "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms" in the "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent" represented by ^{R2 to} R9 is an integer selected from 1 to 18, for example, it can be selected from the range of 1 to 12, for example, it can also be selected from the range of 1 to 6. Specific examples of the "alkoxycarbonyl group having 1 to 18 carbon atoms" include methoxycarbonyl and ethoxycarbonyl.

In the general formula (1), the "thiol group having 0 to 18 carbon atoms and optionally having a substituent" represented by ^R2 to ^R9 may be an unsubstituted thiol group (thiol group: -SH) or a substituted thiol group in which the hydrogen atom of the thiol group is substituted by a substituent. Examples of the substituent of the substituted thiol group include alkyl groups and aryl groups, and the hydrogen atom of each of these groups may be substituted by a substituent selected from the substituent group A described above. For ^the description and specific examples of the alkyl group as a substituent of the thiol group, reference may be made to the description of the "linear or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms" in the above R ² to ^{R 9} , and for the description and specific examples of the aryl group, reference may be made to the description of the "monovalent aromatic alkyl group having 6 to 36 carbon atoms" in the following R 2 to R 9. The number of carbon atoms of the substituted thiol group is preferably in the range of 1 to 18, for example, in the range of 1 to 12, and for example, in the range of 1 to 6. Specific examples of the "substituted thiol group having 1 to 18 carbon atoms" include methylthio, ethylthio, propylthio, phenylthio, biphenylthio, and the like.

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 monosubstituted amino group, or a disubstituted amino group. Examples of the substituents of the substituted amino groups include alkyl groups, aryl groups, and acyl groups, and the hydrogen atom of each of these groups may be substituted with a substituent selected from the substituent group A. For the description and specific examples of the alkyl group and the alkyl group constituting the acyl group, reference may be made to the description of the "straight or branched alkyl group having 1 to 18 carbon atoms" and the "cycloalkyl group having 3 to 10 carbon atoms" in the above R ² to ^R 9, and for the description and specific examples of the aryl group, reference may be made to the description of the "monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms" in the following R ² to R ⁹ . The number of carbon atoms of the monosubstituted amine group and the disubstituted amine group is preferably 1 to 20, for example, in the range of 1 to 12. Specific examples of the monosubstituted amine group include alkylamine groups (e.g., ethylamine groups), acetylamine groups, aromatic amine groups (e.g., anilino groups), etc. Specific examples of the disubstituted amine group include dialkylamine groups (e.g., diethylamine groups), diaromatic amine groups (e.g., diphenylamine groups), acetylanilino groups, etc.

In the general formula (1), ^the description of the aromatic ring constituting the "monovalent aromatic alkyl group having 6 to 36 carbon atoms" in the "monovalent aromatic alkyl group having 6 to 36 carbon atoms which may have ^a substituent" represented by R 2 to R 9 can be referred to the description of the aromatic ring constituting the "arylene group having 6 to 36 carbon atoms" in R ¹ above, and the specific examples of the "monovalent aromatic alkyl group having 6 to 36 carbon atoms" can be referred to the specific examples of the monovalent aromatic alkyl group (monovalent aromatic alkyl group before removing one hydrogen atom) listed in the description of the "arylene group having 6 to 36 carbon atoms" in R ¹ above.

In the general formula (1), the description of ^{the heterocyclic} group constituting the "monovalent heterocyclic group having 5 to 36 ring-forming atoms" in the "monovalent heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent" represented by R 2 to R 9 can be referred to the description of the heterocyclic group constituting the "divalent heterocyclic group having 5 to 36 ring-forming atoms" in R ¹ above, and the specific examples of the "monovalent heterocyclic group having 5 to 36 ring-forming atoms" can be referred to the specific examples of the monovalent heterocyclic group (monovalent heterocyclic group before removing one hydrogen atom) listed in the description of the "divalent heterocyclic group having 5 to 36 ring-forming atoms" in R ¹ above.

In the general formula (1), with respect to "an 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", "an ^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", "an 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", represented by R 2 to R 9, For the description and specific examples of the “substituent” in the “aryloxy group having 6 to 36 carbon atoms which may have a substituent”, the “linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent”, the “thiol group having 0 to 18 carbon atoms which may have a substituent”, the “amino group having 0 to 20 carbon atoms which may have a substituent”, the “monovalent aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent” or the “monovalent heterocyclic group having 5 to 36 ring atoms which may have a substituent”, refer to the description and specific examples of the “substituent” in the above-mentioned “linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent” represented by ^R1 (substituent group A). Here, the substituent of the "optionally substituted monovalent aromatic alkyl group having 6 to 36 carbon atoms" is preferably an amine group substituted with a monovalent aromatic alkyl group (aryl group), and more preferably a diaromatic amine group. The monovalent aromatic alkyl group as a substituent of the amine group may be substituted with a substituent selected from the substituent group A above.

In the general formula (1), at least one of R ² to R ⁹ is preferably a monovalent aromatic alkyl group having 6 to 36 carbon atoms which may have a substituent or an amine group having 0 to 20 carbon atoms which may have a substituent. Among them, at least one of R ³ , R ⁴ , R ⁷ and R ⁸ is more preferably a monovalent aromatic alkyl group having 6 to 36 carbon atoms which may have a substituent or an amine group having 0 to 20 carbon atoms which may have a substituent, and at least one of R ⁴ and R ⁷ is further preferably a monovalent aromatic alkyl group having 6 to 36 carbon atoms which may have a substituent or an amine group having 0 to 20 carbon atoms which may have a substituent. Here, the amine group has 1 to 20 carbon atoms when it has a substituent. In the general formula (1), at least one of R ² to R ⁹ is preferably a group having a diaromatic amino group, and at least one of R ³ , R ⁴ , R ⁷ and R ⁸ is more preferably a group having a diaromatic amino group. In the general formula (1), at least one of R ² to R ⁵ and at least one of R ⁶ to R ⁹ are preferably a group having a diaromatic amino group, at least one of R ³ and R ⁴ and at least one of R ⁷ and R ⁸ are more preferably a group having a diaromatic amino group, and R ⁴ and R ⁷ are further preferably a group having a diaromatic amino group. Here, the group having a diaromatic amino group is, for example, a diaromatic amino group, a diaromatic amino aryl group, or a diaromatic amino carbazole-9-yl group. For the description of each aryl group constituting the diaromatic amino group, the diaromatic amino aryl group and the diaromatic amino carbazole-9-yl group, reference can be made to the description of the "monovalent aromatic alkyl group having 6 to 36 carbon atoms" in the above R ² to R ^9. At least one hydrogen atom in the diaromatic amino group, the diaromatic amino aryl group and the diaromatic amino carbazole-9-yl group may be substituted with a substituent selected from the above substituent group A. As preferred examples of the substituent, there can be listed substituents bonded via a heteroatom, for example, alkoxy groups (methoxy groups, etc.) and diaromatic amino groups (di(methoxyphenyl)amino groups, etc.). Furthermore, as preferred examples of the substituent, there can be listed heteroaryl groups containing nitrogen atoms as the constituent atoms of the ring skeleton (for example, pyridyl groups).

As a preferred compound group represented by the general formula (1), compound group 1 in which at least R ⁴ is not a hydrogen atom can be shown. Compound group 1 includes compound group 1a in which R ⁴ is a diaromatic amino group which may have a substituent, compound group 1b in which R ⁴ is a diaromatic amino aryl group which may have a substituent (preferably a diaromatic amino phenyl group which may have a substituent), compound group 1c in which R ⁴ is a diaromatic amino carbazole-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 a hydrogen atom. In compound groups 1a to 1d, ^R7 in each group may not be a hydrogen atom, for example, ^R4 and ^R7 may be the same group, for example, ^R2 , ^R3 , ^R5 , ^R6 , ^R8 , and ^R9 may be hydrogen atoms. Compound groups 1a to 1d may further satisfy at least one of the following additional conditions. One of the additional conditions is that the above-mentioned "diaromatic amino group" has an alkoxy group (for example, an alkoxy group with 1 to 6 carbon atoms) as a substituent. One of the additional conditions is that the above-mentioned "diaromatic amino group" has a heteroaryl group (for example, a pyridyl group) containing a nitrogen atom as a constituent atom of the ring skeleton as a substituent. One of the additional conditions is that ^R1 is 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 by an alkenyl group, an alkynyl group, a cycloalkyl group or an aryl group. One of the additional conditions is that ^R1 is an arylene group having 6 to 36 carbon atoms (preferably 6 to 14, for example 6 to 10) which may have a substituent. One of the additional conditions is that the atom of ^R1 bonded to _SO3X is a secondary carbon atom. One of the additional conditions is that X is Li, Na, K, Rb or Cs, for example, Li, for example, Na, for example, K, for example, Rb, for example, Cs.

As another preferred compound group represented by the general formula (1), there can be shown 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 diaromatic amino group which may have a substituent, compound group 2b in which R ³ is a diaromatic amino aryl group which may have a substituent (preferably a diaromatic amino phenyl group which may have a substituent), compound group 2c in which R ³ is a diaromatic amino carbazole-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 a hydrogen atom. In compound groups 2a to 2d, ^R8 in each group may not be a hydrogen atom, for example, ^R3 and ^R8 may be the same group, for example, ^R2 , ^R4 to ^R7 , and ^R9 may be a hydrogen atom. Compound groups 2a to 2d may satisfy at least one of the additional conditions described in compound group 1.

As another preferred compound group represented by the general formula (1), compound group 3 in which at least R ² is not a hydrogen atom can be shown. Compound group 3 includes compound group 3a in which R ² is a diaromatic amino group which may have a substituent, compound group 3b in which R ² is a diaromatic amino aryl group which may have a substituent (preferably a diaromatic amino phenyl group which may have a substituent), compound group 3c in which R ² is a diaromatic amino carbazole-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, for example, R ³ to R ⁸ may be a hydrogen atom. Compound groups 3a to 3d may respectively satisfy at least one of the additional conditions described in compound group 1.

As another preferred compound group represented by the general formula (1), compound group 4 in which at least R ⁵ is not a hydrogen atom can be shown. Compound group 4 includes compound group 4a in which R ⁵ is a diaromatic amino group which may have a substituent, compound group 4b in which R ⁵ is a diaromatic amino aryl group which may have a substituent (preferably a diaromatic amino phenyl group which may have a substituent), compound group 4c in which R ⁵ is a diaromatic amino carbazole-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 a hydrogen atom. In compound groups 4a to 4d, ^R6 in each group may not be a hydrogen atom, for example, ^R5 and ^R6 may be the same group, for example, ^R2 to ^R4 and ^R7 to ^R9 may be hydrogen atoms. Compound groups 4a to 4d may satisfy at least one of the additional conditions described in compound group 1.

Specific examples of the compounds represented by the general formula (1) of the present invention are shown below, but the compounds of the present invention should not be construed in a limiting sense by these specific examples. In addition, the exemplary compounds shown below omit some hydrogen atoms, carbon atoms, etc. In addition, the exemplary compounds shown in the chemical structural formula below show one example of possible isomers, and all other isomers and mixtures of two or more isomers are also listed as specific examples.

[Chemistry 3]

The compound represented by the general formula (1) of the present invention can be synthesized by a known method described in Japanese Patent Publication No. 2020-013898. When the synthesis of compound (A-1) is described as an example, compound (A-1) can be obtained by introducing a corresponding substituent in Suzuki-Miyaura coupling reaction or Buchwald reaction into 3,7-dibromophenanthridine and then reacting the corresponding sultone. Similarly, the compound represented by the general formula (1) can be obtained by a known method using a halogenated phenanthridine derivative as a precursor.

As the purification method of the compound represented by the general formula (1) of the present invention, there can be cited purification based on column chromatography, adsorption purification based on silica gel, activated carbon, activated clay, etc., recrystallization and crystallization based on solvents, etc. Alternatively, the above methods can be used in combination to use the compound with improved purity. In addition, the identification of these compounds can be carried out by nuclear magnetic resonance analysis (NMR).

[Usefulness of the compound represented by the general 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 an organic electronic element such as a photoelectric conversion element and an organic electroluminescent element as its hole transport layer. The "hole transport material" in the present invention refers to a material having the 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 be a hole transport material containing a compound other than the compound represented by the general formula (1).

<Photoelectric conversion element> Next, the photoelectric conversion element of the present invention is described. The photoelectric conversion element of the present invention is characterized by containing a hole transport material including a compound represented by the general formula (1). For the description of the compound represented by the general formula (1), reference can be made to the description of the above-mentioned <Compound represented by the general formula (1)> column. The compound represented by the general formula (1) has excellent hole transport properties and can therefore be effectively used as a material for the hole transport layer of the photoelectric conversion element. The following describes a preferred embodiment of the photoelectric conversion element, but the embodiment of the photoelectric conversion element of the present invention is not limited to the embodiment shown below. In one embodiment of the present invention, as shown in FIG1 , the photoelectric conversion element sequentially comprises a conductive support 1, an electron transport layer 2, a photoelectric conversion layer 3, a hole transport layer 4 and a counter electrode 5, and the hole transport layer 4 comprises a compound represented by the general formula (1). In one embodiment of the present invention, the photoelectric conversion element sequentially comprises a conductive support, a hole transport layer, a photoelectric conversion layer, an electron transport layer and a counter electrode, and the hole transport layer comprises a compound represented by the general formula (1). Here, the photoelectric conversion layer comprises, for example, a calcium titanite compound. In addition, the photoelectric conversion element is, for example, a photoelectric conversion element for a solar cell.

Hereinafter, the components and layers of the photoelectric conversion element will be described by taking the photoelectric conversion element shown in FIG. 1 as an example.

[Conductive Support] In the photoelectric conversion element shown in FIG1, the conductive support 1 functions as a cathode for extracting 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 light-transmitting conductive support that can transmit light used for photoelectric conversion, for example, a conductive substrate having a film of a conductive material formed on a light-transmitting 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 and aluminum oxide (AZO), fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), indium-tin composite oxide and other conductive transparent oxide semiconductors, and preferably tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO) and the like are used.

[Electron transport layer] The electron transport layer 2 is a layer containing a material (electron transport material) having the function of transporting electrons, and is disposed between the conductive support 1 and the photoelectric conversion layer 3. It has the function of transporting electrons generated in the photoelectric conversion layer 3 to the conductive support 1 side. In this way, the efficiency of electron movement from the photoelectric conversion layer to the conductive support can be improved. In addition to these functions, the electron transport layer can also have the function of suppressing hole injection from the conductive support. The electron transport layer 2 can be formed adjacent to the conductive support 1, or other layers can 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 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.), _strontium titanium oxide (SrTiO ₃ , etc.); metal oxides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, silver sulfide, etc.; metal selenides such as titanium selenide, zirconium selenide, indium selenide, tungsten selenide, etc.; single semiconductors such as silicon and germanium. These semiconductor materials can be used alone or in combination of two or more. As a preferred example of a semiconductor material for an electron transport layer, a material composed of one or more selected from tin oxide, titanium oxide and zinc oxide can be cited.

As a material for forming the electron transport layer, a paste containing particles of the above-mentioned semiconductor material (semiconductor paste) can be cited. The semiconductor paste may be a commercially available product, or a prepared product prepared by dispersing fine powder of the above-mentioned semiconductor material in a solvent. Specific examples of the solvent used in preparing the semiconductor paste include water; alcohol solvents such as methanol, ethanol, and isopropanol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene, but are not limited to these. These solvents may be used alone or as a mixed solvent of two or more.

As a method for dispersing semiconductor fine powder in a solvent, there can be cited a method of pulverizing the powder with a mortar or the like as needed, and then dispersing the powder in a 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, in order to prevent the aggregation of semiconductor fine particles, it is preferred to add a surfactant or the like, and in order to increase the viscosity, it is preferred to add a thickener such as polyethylene glycol.

The electron transport layer can be formed by a known film forming method. That is, the electron transport layer can be formed by a coating method using a coating liquid containing a semiconductor material (e.g., a coating liquid for the electron transport layer such as a semiconductor paste) or a vapor phase process. Specifically, the electron transport layer can be formed by spin coating, inkjet coating, doctor blade coating, drop casting, squeegee coating, screen printing, reverse roll coating, gravure coating, casting, roll brush coating, spray coating, air knife coating, wire bar coating, pipe scraper coating, etc. Doctor method, immersion coating method or curtain coating method, a method of coating a coating liquid for an electron transport layer on a conductive substrate and then removing the solvent and additives by forging to form a film, a method of forming a film of a semiconductor material by a vapor phase film forming method such as sputtering method, evaporation method, electrodeposition method, electrocrystallization method, microwave irradiation method, etc. Among them, the coating method using the coating liquid for an electron transport layer prepared by spin coating is preferred, but it is not limited to this. Furthermore, the conditions of spin coating can be appropriately set. The film-making environment is not particularly limited and can be in the atmosphere or in an inert gas environment.

The film thickness of the electron transport layer is, for example, 5 nm to 200 nm, preferably 10 nm to 150 nm. Moreover, for example, from the viewpoint of further improving the photoelectric conversion efficiency, when a dense electron transport layer is used, the thickness of the electron transport layer is generally 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 film thickness is generally 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, and more specifically, a layer for generating holes and electrons by generating a charge separation state by light energy. In the photoelectric conversion element shown in FIG1 , the photoelectric conversion layer 3 is formed on the side of the electron transport layer 2 opposite to the conductive support 1.

As an example of a photoelectric conversion layer, a layer formed of a calcite material (calcite layer) can be cited. Here, "calcite material" refers to a material having a calcite type structure 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. As monovalent cations represented by A, K ⁺ , Rb ⁺ , Cs ⁺ , CH ₃ NH ₃ ⁺ (hereinafter, MA: methylammonium), NH=CHNH ₂ ⁺ (hereinafter, FA: formamidine), CH ₃ CH ₂ NH ₃ ⁺ (hereinafter, EA: ethylammonium) can be cited. 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 calcium-titanium 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 , and also mixed cation type and mixed anion type calcium-titanium materials such as (FAMA)Pb(IBr) ₃ , K(FAMA)Pb(IBr) ₃ , Rb(FAMA)Pb(IBr) ₃ , and Cs(FAMA)Pb(IBr) ₃ . The photoelectric conversion layer may contain only one material selected from the calcium-titanium materials, or may contain two or more materials. Furthermore, the photoelectric conversion layer may be composed of only the calcium-titanium material, or may contain the calcium-titanium material and other materials. As other materials, light absorbers may be listed.

The calcium titanate layer can be formed by coating a solution of a halide AX and a metal halide _BX2 (calcium titanate precursor solution) to form a precursor coating and drying the precursor coating. For specific examples of A, B, and X, reference can be made to the description of each ion constituting the above-mentioned _ABX3 . For example, as specific examples of the halide AX, methylammonium halide, formamidine halide, and cesium halide can be listed, and as specific examples of the metal halide _BX2 , lead halide and tin halide can be listed.

From the perspective of the solubility of the precursor, the solvent of the calcium-titanium ore precursor solution can be N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone, etc., but it is not limited to them. Moreover, these solvents can be used alone or in combination of two or more. As a preferred example of the solvent, a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide can be listed. Moreover, the solvent is preferably a dehydrated solvent with a water content of less than 10 ppm. The dehydration of the solvent can be carried out using a molecular sieve, etc.

The step of applying the calcium-titanium precursor solution is preferably carried out in a dry environment, more preferably in a dry inert gas environment such as a glove box. This prevents water from mixing into the calcium-titanium layer, and allows the manufacture of high-efficiency calcium-titanium solar cells with good reproducibility. For the coating method, refer to the description of the coating method for the electron transport layer described in the above column [Electron Transport Layer].

The calcium-titanium layer is formed by drying the precursor coating thus formed. The drying of the precursor coating may be natural drying or heating drying using a hot plate or the like. From the perspective of generating a calcium-titanium material from a precursor, the temperature when the precursor coating is heated using a hot plate or the like is preferably 50 to 200°C, more preferably 70 to 150°C. Furthermore, the heating time is preferably about 10 to 90 minutes, more preferably about 10 to 60 minutes.

The thickness of the photoelectric conversion layer (calcium-titanium layer) is preferably 50 to 1000 nm, more preferably 300 to 700 nm. This can suppress performance degradation caused by defects and peeling of the photoelectric conversion layer, prevent the device resistance from becoming too high, and allow the photoelectric conversion layer to have a sufficient light absorption rate.

[Hole transport layer] In the photoelectric conversion element shown in FIG1 , the hole transport layer 4 is a layer containing a material having the function of transporting holes (hole transport material), which is arranged between the photoelectric conversion layer 3 and the counter electrode 5, and has the function of transporting holes generated in the photoelectric conversion layer 3 to the counter electrode 5 side. In this way, the efficiency of moving holes from the photoelectric conversion layer to the electrode can be improved. In addition to these functions, the hole transport layer can also have the 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 the general formula (1) as a hole transport material. The compound represented by the general formula (1) contained in the hole transport layer may be one or more selected from the group of compounds represented by the general formula (1). In addition to the compound represented by the general formula (1), the hole transport layer may also contain a hole transport material that is not a compound represented by the general formula (1) (hereinafter referred to as "second hole transport material") and 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 transporting 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-methoxyphenylamino)-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. The second hole transporting material may be mixed in the hole transporting layer, or a hole transporting layer containing the second hole transporting material may be stacked on the hole transporting layer containing the compound represented by the general formula (1).

Regarding the method for forming the hole transport layer, reference may be made to the description of the method for forming the electron transport layer described above. In addition, the solvent of the coating liquid for the hole transport layer may also use the following solvents. That is, the solvent used in the coating liquid for the hole transport layer may include aromatic organic solvents such as benzene, toluene, xylene, mesitylene, tetrahydronaphthalene (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, nitrobenzene, etc.; halogenated alkyl organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, dichloromethane, etc.; nitrile solvents such as benzonitrile and acetonitrile; Ether solvents such as tetrahydrofuran, dioxane, diisopropyl ether, c-amyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether; ester solvents such as ethyl acetate and propylene glycol monomethyl ether acetate; alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, 2-n-butoxyethanol, etc., but not limited to them. These solvents can be used alone or in combination of two or more. Among them, the solvent of the coating liquid for forming the hole transport layer is preferably an aromatic organic solvent and a halogenated alkyl organic solvent.

The hole transport layer is preferably formed in a dry environment. In addition, it is preferred to use a solvent that has been dehydrated to a water content of 10 ppm or less in the coating solution. By preventing the incorporation of water, high-efficiency calcium-titanium-based solar cells can be manufactured with good reproducibility. The thickness of the hole transport layer is preferably 5 nm to 500 nm, and more preferably 10 nm to 250 nm, from the perspective of further improving the photoelectric conversion efficiency.

Additives As additives that can be added to the hole transport layer, oxidants (doping agents) and alkaline compounds (alkaline additives) can be listed. By adding these additives to the hole transport layer, the carrier concentration of the hole transport layer is increased, thereby improving the photoelectric conversion efficiency of the photoelectric conversion element.

Specific examples of the doping agent include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridinium)cobalt(III)tris[bis(trifluoromethane)sulfonylimide] (FK209), NOSbF ₆ , SbCl ₅ , SbF ₅ and the like. Among them, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is preferably used.

The concentration of the dopant in the hole transport layer is preferably 2.0 equivalents or less, and more preferably 0.5 equivalents or less, relative to 1 equivalent of the hole transport material. The inclusion of an additive in the hole transport layer improves the photoelectric conversion efficiency of the photoelectric conversion element. On the other hand, if the concentration of the dopant is too high, the durability of the photoelectric conversion element may be reduced. Specific examples of alkaline additives include 4-tert-butylpyridine (tBP), 2-picoline, 2,6-lutidine, etc. Among them, 4-tert-butylpyridine is preferably used. Furthermore, the alkaline additive and the dopant can be used simultaneously. The concentration of the alkaline additive in the hole transport layer is preferably less than 5 equivalents, and more preferably less than 3.5 equivalents, relative to 1 equivalent of the hole transport material.

[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 to the conductive support 1 with the electron transport layer 2, the photoelectric conversion layer 3 and the hole transport layer 4 interposed therebetween. The counter electrode functions as an anode for extracting holes transported from the photoelectric conversion layer via the hole transport layer. The counter electrode 5 may be disposed adjacent to the hole transport layer 4, or an electron blocking layer composed of an organic material or an inorganic compound semiconductor may be interposed between the hole transport layer 4 and the counter electrode 5.

Specifically, the counter electrode material includes platinum, titanium, stainless steel, aluminum, gold, silver, nickel, magnesium, chromium, cobalt, copper and other metals or alloys thereof. Among them, gold, silver or silver alloys are preferably used from the viewpoint of showing high conductivity even in thin films. As silver alloys, from the viewpoint of being less susceptible to sulfidation or chlorination and having high stability as thin films, silver and gold alloys, silver and copper alloys, silver and palladium alloys, silver, copper and palladium alloys, silver and platinum alloys, etc. can be listed. In addition, the counter electrode is preferably a material that can be formed in a vapor phase process such as evaporation. When a metal electrode is used as a counter electrode, in order to obtain good conductivity, its film thickness is preferably greater than 10nm, and more preferably greater than 50nm.

In the photoelectric conversion element shown in FIG1 , the conductive support 1 is a cathode and the counter electrode 5 is an anode. It is preferred that light such as sunlight (light used for photoelectric conversion) is irradiated from the side of the conductive support. When irradiated with sunlight or the like, the photoelectric conversion layer absorbs light and becomes excited, generating electrons and holes. The electrons move to the conductive support through the electron transport layer and the holes move to the counter electrode through the hole transport layer, causing current to flow and functioning as a photoelectric conversion element.

Furthermore, the photoelectric conversion element of the present invention may have a conductive support, a hole transport layer, a photoelectric conversion layer, an electron transport layer and a counter electrode in sequence. At this time, the conductive support acts as an anode, and the counter electrode acts as a cathode, and the electrons generated in the photoelectric conversion layer move to the counter electrode via the electron transport layer, and the holes generated in the photoelectric conversion layer move to the conductive support via the hole transport layer. In this way, electric current can be extracted to the outside. For the description and specific examples of the materials of each part and each layer used in this embodiment, reference can be made to the corresponding description of the photoelectric conversion element shown in FIG. 1 above.

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. Short-circuit current density refers to the current per 1 ^cm2 flowing between the two terminals when the output terminals are short-circuited, and open-circuit voltage refers to the voltage between the two terminals when the output terminals are open. In addition, the fill factor refers to the value obtained by dividing the maximum output (the product of current and voltage) by the product of short-circuit current density and open-circuit voltage, and is mainly affected by internal resistance. The photoelectric conversion efficiency is calculated as follows: the value obtained by dividing the maximum output (W) by the light intensity (W) per 1 ^cm2 is multiplied by 100 and expressed as a percentage.

The photoelectric conversion element of the present invention can be applied to solar cells, various photo sensors, etc. The solar cell to which the photoelectric conversion element of the present invention is applied is preferably a calcium titanate type solar cell. The solar cell is obtained by using a photoelectric conversion element containing a compound represented by the general formula (1) in a hole transport layer as a battery box, arranging a required number of the battery boxes, modularizing, and setting prescribed electrical wiring. [Example]

The following examples are given to further illustrate the features of the present invention. The materials, processing contents, processing procedures, etc. shown below can be appropriately changed as long as they do not deviate from the main purpose of the present invention. Therefore, the present invention is not limited to the following examples. In addition, the identification of the compounds obtained in the synthesis examples was carried out by ^1H -NMR (1H-NMR (JEOL Ltd. nuclear magnetic resonance device, JNM-ECZ400S/L1 model).

[Synthesis Example 1] Synthesis of compound (A-1) In a reaction vessel, bromine (2.0 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and acetic acid (100 mL) were added and stirred. Under stirring, a solution of bromine (3.8 g) in acetic acid (90 mL) was added dropwise over 1 hour. After stirring for 3 hours, the mixture was cooled with an ice-water bath and a 5% aqueous sodium thiosulfate solution (60 g) was added. The obtained solution was added to an aqueous solution prepared from tap water (400 mL) and a 48% aqueous potassium hydroxide solution (3.2 g), and the precipitated solid was obtained as a crude product. The crude product was purified by a silica gel column (hexane:ethyl acetate), thereby obtaining a compound represented by the following formula (2) (yield: 2.02 g, yield 54%). ¹ H-NMR (400MHz, DMSO-d ₆ ): δ (ppm) = 6.37-6.39 (2H), 6.80-6.81 (2H), 6.90-6.92 (2H), 8.54 (1H).

In a reaction vessel, the compound of the following formula (2) (0.5 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boric 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 added, and deaerated under reduced pressure. Tetrakistriphenylphosphine palladium (0.08 g, manufactured by Kanto Chemical Co., Inc.) was added, and deaerated under reduced pressure, and stirred for 7 hours by heating and reflux. After the aqueous layer of the reaction solution was removed by separation, the organic layer was distilled under reduced pressure to remove the solvent. Toluene was further added to the obtained crude product, and after separation, the organic layer was distilled under reduced pressure to remove the solvent. The obtained crude product was purified by a silica gel column (toluene:ethyl acetate) to obtain a compound represented by the following formula (3) (yield: 0.6 g, yield: 52%). ¹ H-NMR (400 MHz, DMSO-d ₆ ): 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) [Chemical 4]

In a reaction vessel, the compound of the above formula (3) (0.30 g), 55% sodium hydride (0.04 g, manufactured by Kanto Chemical Co., Inc.), and DMF (10 mL) were added and stirred at room temperature for 1 hour. 2,4-Butanesulfonate (0.063 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 90°C for 4 hours. The reaction solution was distilled under reduced pressure to remove the solvent, and the obtained crude product was purified by a silica gel column (ethyl acetate: methanol). Further purification was performed by recrystallization (ethyl acetate: ethanol), and a compound represented by the following formula (A-1) was obtained (yield: 0.22 g, yield: 62%). ¹ H-NMR (400MHz, DMSO-d ₆ ): 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) [Chemical 5]

[Synthesis Example 2] Synthesis of Compound (A-70) In a reaction vessel, the compound of the above formula (2) (1.50 g), 4-dimethylaminopyridine (0.107 g, manufactured by Kanto Chemical Co., Inc.), di-tert-butyl dicarbonate (1.49 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and tetrahydrofuran (30 mL) were added and stirred at room temperature for 1 hour. The reaction solution was directly concentrated under reduced pressure, and the residue was dissolved in ethyl acetate (50 mL), and then washed with tap 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 solid obtained 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). [Chemical 6]

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 Co., Inc.), toluene (15 mL), and tert-butyl alcohol (3 mL) were placed in a reaction container, and deaerated by bubbling with hydrogen 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 Corporation) were added to the reaction solution twice every 4 hours, and stirred for 8 hours under heating and reflux. After the reaction solution was cooled naturally, it was filtered through diatomaceous earth, and the obtained filtrate was concentrated under reduced pressure. The crude product was purified by a silica gel column (toluene:ethyl acetate = 50:1). The obtained purified product 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, yield: 80%). ¹ H-NMR (400MHz, 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).

In a reaction vessel, the compound of the following formula (5) (0.450 g), 36% hydrochloric acid (6.5 mL), and ethyl acetate (10 mL) were added and stirred under heating and reflux for 8 hours. After the reaction solution was cooled naturally, a saturated sodium bicarbonate aqueous solution (100 mL) was added, and then extracted with tetrahydrofuran (50 mL) and separated. The obtained organic layer was dehydrated with magnesium sulfate, and the filtrate obtained by filtration was concentrated under reduced pressure. The crude product was purified by a silica gel column (toluene:ethyl acetate = 50:1 to 20:1). The obtained purified product 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). [Chemical 7]

The compound of the above formula (6) (0.251 g), 55% sodium hydroxide (0.03 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were added to a reaction vessel and stirred at room temperature for 1 hour. 2,4-Butanesulfone (0.03 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was added thereto and stirred at 80°C for 3 hours. The reaction solution was distilled under reduced pressure to remove the solvent, and the obtained crude product was purified by a silica gel column (ethyl acetate: methanol = 9:1 to 4:1). The purified product 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%). ¹ H-NMR (400 MHz, DMSO-d ₆ ): 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). [Chemistry 8]

[Synthesis Example 3] Synthesis of Compound (A-71) In a reaction vessel, the compound of formula (6) (0.251 g), tri-butoxypotassium (0.017 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were added and stirred at room temperature for 1 hour. 2,4-Butanesulfone (0.02 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was added 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 by a silica gel column (ethyl acetate: methanol = 9:1 to 4:1). The purified product was concentrated and 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). [Chem. 9]

[Synthesis Example 4] Synthesis of Compound (A-72) A compound represented by the following formula (7) (0.401 g), a compound of the above formula (4) (0.930 g), tri-butyloxysodium (0.200 g, manufactured by FUJIFILM Wako Pure Chemical Corporation), toluene (5 mL), and tetrahydrofuran (5 mL) were placed in a reaction vessel, and deaerated by bubbling with hydrogen for 20 minutes. Tris(dibenzylideneacetone)dipalladium(0) (0.040 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and tri-tri-butylphosphine (0.020 g, manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to the reaction solution in two portions every 4 hours, and the mixture was stirred for 12 hours under heating and reflux. After the reaction solution was cooled naturally, it was filtered through diatomaceous earth, and the obtained filtrate was concentrated under reduced pressure. The crude product was purified by a silica gel column (toluene:methanol=100:1 to 20:1). The obtained purified product fraction was concentrated under reduced pressure, and the concentrate was dried under reduced pressure to obtain a compound represented by the following formula (8) as a yellow solid (yield: 0.559 g, yield: 61%). ¹ H-NMR (400MHz, DMSO-d ₆ ): 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). [Chemical 10]

In a reaction vessel, the compound of formula (8) (0.500 g), 36% hydrochloric acid (7 mL), and ethyl acetate (20 mL) were added and stirred for 2 hours under heating and reflux. After the reaction solution was cooled naturally, a saturated sodium bicarbonate aqueous solution (50 mL) was added, and then extracted with tetrahydrofuran (50 mL) and toluene (50 mL) and separated. The obtained organic layer was dehydrated with magnesium sulfate, and the filtrate obtained by filtration was concentrated under reduced pressure. The crude product was purified by a silica gel column (toluene: methanol = 80:1 to 20:1). The obtained purified product 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). [Chemical 11]

The compound of formula (9) (0.233 g), 55% sodium hydroxide (0.05 g, manufactured by Kanto Chemical Co., Inc.), and dimethylformamide (10 mL) were added to a reaction vessel and stirred at room temperature for 1 hour. 2,4-Butanesulfone (0.055 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 80°C for 2 hours. The reaction solution was distilled under reduced pressure to remove the solvent, and the obtained crude product was purified by a silica gel column (ethyl acetate: methanol = 9:1 to 4:1). The purified product distillate was concentrated under reduced pressure, and the concentrate was dried under reduced pressure, thereby obtaining a compound represented by the following formula (A-72) as a yellow solid (yield: 0.140 g, yield: 49%). ¹ H-NMR (400MHz, DMSO-d ₆ ): 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 (6 H), 3.54-3.60(1H), 2.35-2.42(1H), 1.87-1.96(1H), 1.56(1H), 1.10-1.14(3H). [Chemical 12]

[Example 1] Preparation of a photoelectric conversion element using compound (A-1) 1 Glass with an ITO film (conductive support 1, manufactured by GEOMATEC Co., Ltd.) was ultrasonically cleaned with isopropyl alcohol and subjected to UV ozone treatment. Thereafter, the following layers were formed by coating in a dry environment with a relative humidity of less than 10%. First, a tin oxide dispersion (electron transport layer coating solution) in which a tin oxide colloid solution (tin oxide (IV), 15% in _H2O colloid dispersion: manufactured by Alfa Aesar) and purified water were mixed at a ratio of 1:9 (volume ratio) was spin-coated on the ITO film. Thereafter, the film was heated on a hot plate at 150° C. for 30 minutes to form a tin oxide layer (electron transport layer 2) having 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 csiolide (1.5M, manufactured by Tokyo Chemical Industry Co., Ltd.) was further added to prepare a calcium-titanium ore precursor solution. Here, the solution to which csiolide was added was added in an amount such that the amount of csiolide added was 5% in terms of the composition ratio. The tantalum precursor solution was dripped onto the tin oxide layer, and chlorobenzene (0.3 mL) was dripped and spun to form a tantalum precursor coating. Then, it was heated on a hot plate at 100°C for 1 hour to form a tantalum layer (photoelectric conversion layer 3) of Cs(MAFA)Pb(IBr) ₃ with a film thickness of about 500 nm. Next, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine were dissolved in chlorobenzene to prepare a solution, and compound (A-1) was dissolved in the solution at a concentration of 50 mM to prepare a coating solution for a hole transport layer. Here, the concentrations of lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine in the hole transport coating solution were set to 0.5 equivalents and 3 equivalents, respectively, relative to compound (A-1). The hole transport layer coating solution was spin-coated on the Cs(MAFA)Pb(IBr) ₃ layer and then dried to form a hole transport layer 4 with a film thickness of about 200 nm. Next, on the hole transport layer 4, gold was deposited by vacuum evaporation at a vacuum degree of 1×10 ^-4 Pa to a thickness of 80 nm to form a gold electrode (counter electrode 5), thereby forming a photoelectric conversion element.

[Example 2] Preparation of a photoelectric conversion element using compound (A-1) 2 When preparing a coating solution for a hole transport layer, lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine were not added, and the prepared coating solution for hole transport was spin-coated at room temperature. A photoelectric conversion element was prepared in the same manner as in Example 1.

[Example 3] Preparation of a photoelectric conversion element using compound (A-70) 1 A photoelectric conversion element was prepared in the same manner as in Example 1 except that a solution prepared in the following order was used as a coating solution for the hole transport layer. A dopant solution was prepared by dissolving lithium bis(trifluoromethanesulfonyl)imide in acetonitrile at a concentration of 1.8 M in a dry environment with a relative humidity of less than 10%. A chlorobenzene solution in which compound (A-70) was dissolved at a concentration of 28 mM was prepared, and the dopant solution was added to compound (A-70) so that lithium bis(trifluoromethanesulfonyl)imide became 0.5 equivalents. Furthermore, 3.3 equivalents of 4-tert-butylpyridine were added to compound (A-70) to prepare a coating solution for a hole transport layer.

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

[Example 5] Preparation of a 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 a photoelectric conversion element using compound (A-71) 2 A photoelectric conversion element was prepared in the same manner as in Example 5 except that a doping agent solution and 4-tert-butylpyridine were not added when preparing a coating solution for a hole transport layer.

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

[Evaluation of characteristics 1] The photoelectric conversion element produced was irradiated with pseudo-solar light (AM1.5, 1000 W/m ² ) from the side of the conductive support body by a white light irradiation device (manufactured by Bunkoukeiki Co., Ltd., OTENTO-SUNSH model), and the initial photoelectric conversion efficiency (PCE) measured by SourceMeter (manufactured by KEITHLEY, Model 2400 Series SourceMeter) is shown in Table 1. In addition, the short-circuit current, open-circuit voltage and fill factor of each photoelectric conversion element are also shown in Table 1. [Table 1] Hole transport materials Doping agent (LiTFSI) Addition amount [equivalent] Short circuit current Jsc [mA/cm ² ] Open circuit voltage Voc [V] Fill Factor FF Initial photoelectric conversion efficiency PCE [%] Embodiment 1 A-1 0.5 22.33 1.13 0.63 15.93 Embodiment 2 A-1 0 20.94 1.08 0.56 12.80 Embodiment 3 A-70 0.5 22.22 1.10 0.74 16.54 Embodiment 4 A-70 0 21.50 1.01 0.64 14.02 Embodiment 6 A-71 0 21.44 1.04 0.57 12.85 Comparison Example 1 B-1 0.5 20.82 0.97 0.57 11.60

As shown in Table 1, the photoelectric conversion element of the embodiment in which the compound of the general formula (1) is used as the hole transport material shows excellent photoelectric conversion efficiency compared with the photoelectric conversion element of the comparative example 1 using the conventional standard hole transport material, that is, the compound (B-1). In addition, when the compound of the general formula (1) is used as the hole transport material, even without using a dopant, a higher photoelectric conversion characteristic than when the compound (B-1) is used can be obtained. From the above results, it can be seen that the photoelectric conversion efficiency can be improved by using the compound represented by the general formula (1) as the hole transport material. In addition, it can be seen that it is possible to reduce the manufacturing cost and simplify the manufacturing process without adding a dopant and an alkaline additive.

[Evaluation of characteristics 2] After measuring the initial photoelectric conversion efficiency of the prepared photoelectric conversion element by the same method as above, the photoelectric conversion element was sealed in a zippered laminate bag (SEISANNIPPONSHA LTD., AL-8) in a glove box under a nitrogen environment. 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 1000 hours. Under pseudo-solar light irradiation, the photoelectric conversion efficiency (PCE) after heating for 1000 hours was measured again by the same method as above. The retention rate (%) calculated by the following formula (a-1) using the obtained initial photoelectric conversion efficiency and the photoelectric conversion efficiency after heating for 1000 hours is shown in Table 2. [Formula 1] (a-1)

[Table 2] Hole transport materials Doping agent (LiTFSI) Addition amount [equivalent] Retention rate [%] Embodiment 2 A-1 0 94.26 Embodiment 5 A-71 0.5 97.73 Embodiment 6 A-71 0 82.19 Comparison Example 1 B-1 0.5 51.25

From the results in Table 2, it can be seen that the photoelectric conversion efficiency of the embodiment using the compound of general formula (1) as the hole transport material is higher than that of the photoelectric conversion element of comparative example 1 using the conventional standard hole transport material, namely compound (B-1), even after heating for 1000 hours, and shows excellent heat resistance. (Industrial applicability)

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. In this way, electric energy converted from solar energy can be efficiently provided as a clean energy source. In addition, the hole transport material containing the compound of the present invention can also be applied to organic EL elements, image sensors, etc. Therefore, the present invention has high industrial applicability.

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

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

1: Conductive support

2: Electron transport layer

3: Photoelectric conversion layer

4: Hole transport layer

5: Opposite electrode

Claims (10)

A compound represented by the following general formula (1): [wherein, ^R1 is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkenylene group having 2 to 20 carbon atoms which may have a substituent, a linear or branched alkynylene group having 2 to 20 carbon atoms which may have a substituent, a cycloalkylene group having 3 to 12 carbon atoms which may have a substituent, an arylene group having 6 to 36 carbon atoms which may have a substituent, or a divalent heterocyclic group having 5 to 36 ring atoms which may have a substituent, X represents a monovalent cation other than a hydrogen ion, ^R2 to ^R9 each independently represent a hydrogen atom, a linear or branched alkylene 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 thiol group having 0 to 18 carbon atoms which may have a substituent, an amine group having 0 to 20 carbon atoms which may have a substituent, a monovalent aromatic alkyl 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]. The compound of claim 1, wherein R ¹ is a linear or branched alkylene group having 1 to 18 carbon atoms which may have a substituent. The compound of claim 1, wherein the atom of R ¹ bonded to SO ₃ X is a secondary carbon atom or a carbon atom constituting the skeleton of the benzene ring. The compound of any one of claims 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 amine group having 0 to 20 carbon atoms which may have a substituent. The compound of any one of claims 1 to 3, wherein at least one of R ² to R ⁹ is a group having a diaromatic amine group which may have a substituent. The compound of claim 5, wherein the diaromatic amine group is substituted by a substituent bonded via a heteroatom. The compound of claim 5, wherein the group having a diaromatic amino group which may have a substituent is a diaromatic amino group which may have a substituent, a diaromatic amino aryl group which may have a substituent, or a diaromatic amino carbazole-9-yl group which may have a substituent. A hole transporting material comprising the compound of any one of claims 1 to 7. A photoelectric conversion element using the hole transport material of claim 8. A solar cell having the photoelectric conversion element of claim 9.