JP7735108B2 - Compound, hole transport material for photoelectric conversion element, and photoelectric conversion element and solar cell using the same - Google Patents

Description

The present invention relates to a compound, a hole transport material for a photoelectric conversion element, and a photoelectric conversion element and a solar cell using the same.

In recent years, solar power generation has been attracting attention as a clean energy source, and active development is underway into solar cells, which are photoelectric conversion elements that convert solar energy into electrical energy. Among these, the development of solar cells that use perovskite materials in the photoelectric conversion layer (hereinafter referred to as perovskite solar cells) has attracted attention as a next-generation solar cell that can be manufactured at low cost using a solution process (see, for example, Patent Document 1 and Non-Patent Documents 1 and 2).

Perovskite solar cells often use a hole transport material for photoelectric conversion elements within the element. The purposes of using this material include (1) enhancing the ability to selectively transport holes and thereby improving photoelectric conversion efficiency, and (2) protecting the perovskite material, which is susceptible to the effects of moisture and oxygen, by bonding it to the perovskite photoelectric conversion layer (see, for example, Non-Patent Document 3). The spirobifluorene organic compound Spiro-OMeTAD is often used as a standard hole transport material for photoelectric conversion elements.

Although relatively high photoelectric conversion efficiency can be achieved by using Spiro-OMETAD, the synthesis process is complicated, posing cost challenges, and there are also usage challenges, such as the time required for the photoelectric conversion efficiency to stabilize and the fact that this time is not constant (Non-Patent Document 4). Therefore, there is a need for hole transport materials for photoelectric conversion elements that can solve these issues, but there are few reports of hole transport materials for photoelectric conversion elements that achieve photoelectric conversion efficiencies exceeding those of Spiro-OMETAD. Given these current circumstances, there is a need for hole transport materials for photoelectric conversion elements that exhibit excellent photoelectric conversion properties and photoelectric conversion efficiency that is stable over time.

International Publication No. 2017/104792

Journal of the American Chemical Society, 2009, Vol. 131, pp. 6050-6051 Science, 2012, Vol. 388, pp. 643-647 Chemical Science, 2019, 10, P. 6748-6769 Scientific Reports, 2012, Vol. 2, 591

The problem that the present invention aims to solve is to provide a novel hole transport material for photoelectric conversion elements that achieves excellent photoelectric conversion efficiency when used in photoelectric conversion elements and solar cells, and to provide photoelectric conversion elements and solar cells that use the same.

In order to solve the above problems, the inventors conducted extensive research and discovered that by using compounds having specific structures and combinations of such compounds as hole transport materials for photoelectric conversion elements, it is possible to obtain photoelectric conversion elements and solar cells that achieve highly efficient photoelectric conversion. In other words, the gist of the present invention is as follows:

1. A compound represented by the following general formula (1), in which ^X1 and ^X2 in general formula (1) are each independently represented by the following general formula (2):

[wherein R ¹ to R ²⁰ each independently represent a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent,
R ¹ to R ²⁰ each independently represent at least one of a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
or an acyl group having 1 to 20 carbon atoms which may have a substituent;
It shall have the following.
Adjacent groups of R ¹ to R ⁵ , R ⁶ to R ¹⁰ , R ¹¹ to R ¹⁵ , and R ¹⁶ to R ²⁰ may be bonded to each other to form a ring, and R ⁵ and R ⁶ , and R ¹⁵ and R ¹⁶ may be bonded to each other to form a ring.]

wherein R ²¹ to R ²⁶ each independently represent a hydrogen atom,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or an optionally substituted heterocyclic group having 5 to 36 ring atoms,
R ²¹ and R ²² , R ²³ and R ²⁴ , and R ²⁵ and R ²⁶ may be bonded to each other to form a ring.
^Y1 represents an oxygen atom, a sulfur atom, or a selenium atom, and m and n each represent an integer of 0 to 2, provided that either m or n is 1 or 2.

2. A compound in which m in the general formula (2) is 1.

3. A hole transport material for a photoelectric conversion element containing the compound described above.

4. The hole transport material for a photoelectric conversion element, characterized by containing a compound represented by the following general formula (3):

[In the formula, R ²⁷ and R ²⁸ each independently represent
nitrile groups,
a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms;
a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent;
a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
Alternatively, it represents a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ²⁹ to R ³² each independently represent
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent.
R ²⁹ and R ³⁰ , and R ³¹ and R ³² may be bonded to each other to form a ring.]

5. A hole transport material for a photoelectric conversion element, wherein the compound represented by general formula (3) is represented by the following general formulas (4) to (6):

In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent a hydrogen atom, a halogen atom, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or an optionally substituted heterocyclic group having 5 to 36 ring atoms,
Adjacent groups of R ³³ to R ³⁷ , R ³⁸ to R ⁴² , R ⁴³ to R ⁴⁷ , and R ⁴⁸ to R ⁵² may be bonded to each other to form a ring.]

In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent the same substituents as those described above,
Adjacent groups of R ³³ to R ³⁶ , R ³⁹ to R ⁴² , R ⁴³ to R ⁴⁶ , and R ⁴⁹ to R ⁵² may be bonded to each other to form a ring.]

In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent the same substituents as those described above,
Adjacent groups of R ³³ to R ³⁶ , R ³⁹ to R ⁴² , R ⁴³ to R ⁴⁶ , and R ⁴⁹ to R ⁵² may be bonded to each other to form a ring.
^Z1 and ^Z2 each independently represent an oxygen atom, a sulfur atom, or a selenium atom.

6. A hole transport material for a photoelectric conversion element, characterized in that the content of the compound represented by general formula (3) is 3 to 96 mass %.

7. A hole transport material for a photoelectric conversion element, characterized in that the content of the compound represented by general formula (3) is 50 to 94 mass %.

8. A photoelectric conversion element using the hole transport material for photoelectric conversion elements described above.

9. A solar cell using the photoelectric conversion element described in claim 7.

The hole transport material for photoelectric conversion devices according to the present invention can provide a hole transport material for photoelectric conversion devices that achieves excellent photoelectric conversion efficiency, as well as photoelectric conversion devices and solar cells that use the same.

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

Embodiments of the present invention are described in detail below. The hole transport layer material for a photoelectric conversion element of the present invention is used in a photoelectric conversion element.

<Photoelectric conversion element>
As shown in the schematic cross-sectional view of FIG. 1 , the photoelectric conversion element of the present invention typically includes a conductive support (electrode) 1, an electron transport layer 2, a photoelectric conversion layer 3, an intermediate layer 4, a hole transport layer 5, and a counter electrode 6.

The compounds represented by general formula (1) contained in the hole transport material for photoelectric conversion elements are specifically described below, but the present invention is not limited to these.

In the general formula (1), R ¹ to R ²⁰ each independently represent a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
Alternatively, it represents a heterocyclic group having 5 to 36 ring atoms which may have a substituent.

In the present invention, "halogen atoms" include fluorine, chlorine, bromine, and iodine.

In general formula (1), specific examples of the "straight-chain or branched alkyl group having ¹ to ²⁰ carbon atoms" in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, and a decyl group.

In general formula (1), specific examples of the "straight-chain or branched alkenyl group having ² to ²⁰ carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 include ethenyl group (vinyl group), 1-propenyl group, 2-propenyl group (allyl group), 1-methylethenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, and straight-chain or branched alkenyl groups having 2 to 20 carbon atoms in which a plurality of these alkenyl groups are bonded.

In general formula (1), specific examples of the "straight-chain or branched alkynyl group having ² to ²⁰ carbon atoms" in the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 1-methyl-2-propynyl group, a 1-pentynyl group, a 2-pentynyl group, a 1-methyl-n-butynyl group, a 2-methyl-n-butynyl group, a 3-methyl-n-butynyl group, and a 1-hexynyl group.

In general formula (1), specific examples 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 ¹ to R ²⁰ include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a 4-methylcyclohexyl group, and a 4-ethylcyclohexyl group.

In general formula (1), specific examples of the "straight-chain or branched alkoxy group having ¹ to ²⁰ carbon atoms" in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 include a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group, a decyloxy group, an isopropoxy group, an isobutoxy group, an s-butoxy group, a t-butoxy group, an isooctyloxy group, a t-octyloxy group, a phenoxy group, a tolyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthyloxy group, an anthryloxy group, a phenanthryloxy group, a fluorenyloxy group, and an indenyloxy group.

In general formula (1), specific examples of the "straight-chain or branched cycloalkoxy group having ³ to ¹⁰ carbon atoms" in the "straight-chain or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R 1 to R 20 include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and a 4-methylcyclohexyloxy group.

In general formula (1), specific examples of the "acyl group having 1 to 20 carbon atoms" in the "acyl group having 1 to 20 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a benzoylacetyl group, and a benzoyl group.

In the general formula (1), specific examples of the "thio group having 1 to 18 carbon atoms" in the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ include a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, and a biphenylthio group.

In general formula (1), the "amino group having 1 to 20 carbon atoms" in the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ specifically includes monosubstituted amino groups such as ethylamino, acetylamino, and phenylamino, and disubstituted amino groups such as diethylamino, diphenylamino, and acetylphenylamino.

In general formula (1), specific examples of the "aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a biphenyl group, an anthracenyl group (anthryl group), a phenanthryl group, a fluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, etc. In the present invention, the aromatic hydrocarbon group is considered to include a "condensed polycyclic aromatic group".

In general formula (1), specific examples of the "heterocyclic group having 5 to 36 ring atoms" in the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ¹ to R ²⁰ include a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group (furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and a carbonyl group.

In general formula (1), examples of the "substituent" in the "linear or branched alkyl group of 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group of ² to ²⁰ carbon atoms which may have a substituent", "linear or branched alkynyl group of 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group of 3 to 10 carbon atoms which may have a substituent", "alkoxy group of 1 to 20 carbon atoms which may have a substituent", "linear or branched cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent", "acyl group of 1 to 20 carbon atoms which may have a substituent", "thio group of 1 to 18 carbon atoms which may have a substituent", "amino group of 1 to 20 carbon atoms which may have a substituent", "aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent" or "heterocyclic group of 5 to 36 ring atoms which may have a substituent" represented by R 1 to R 20 specifically include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a cyano group; a hydroxyl group; a nitro group; a nitroso group; a carboxyl group; a phosphate group;
Carboxylic acid ester groups such as methyl ester groups and ethyl ester groups; thioxo groups (>C=S);
linear or branched alkyl groups having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, and decyl groups;
linear or branched alkenyl groups having 2 to 20 carbon atoms, such as ethenyl (vinyl), 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, and 1-ethylethenyl;
linear or branched alkoxy groups having 1 to 18 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, a pentyloxy group, or a hexyloxy group;
Aromatic hydrocarbon groups having 6 to 30 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, or a pyrenyl group;
heterocyclic groups having 5 to 30 ring atoms, such as a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group (a furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbonylyl group;
an amino group having 0 to 18 carbon atoms, which is an unsubstituted amino group (—NH ₂ ), a monosubstituted amino group such as an ethylamino group, an acetylamino group, or a phenylamino group, or a disubstituted amino group such as a diethylamino group, a diphenylamino group, or an acetylphenylamino group;
thio groups having 0 to 18 carbon atoms, such as an unsubstituted thio group (thiol group: —SH), a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, or a biphenylthio group;
These "substituents" may be contained in only one or more, and when more than one is contained, they may be the same or different. Furthermore, these "substituents" may further have the substituents exemplified above.

In the general formula (1), R ¹ to R ²⁰ each represent at least one of a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
Alternatively, it has an acyl group having 1 to 20 carbon atoms which may have a substituent.

In general formula (1), R ¹ to R ²⁰ are preferably a hydrogen atom, a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an amino group having 1 to 20 carbon atoms which may have a substituent.

In general formula (1), R ¹ to R ²⁰ represent the substituents as described above, but adjacent groups among R ¹ to R ⁵ , R ⁶ to R ¹⁰ , R ¹¹ to R ¹⁵ , and R ¹⁶ to R ²⁰ may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring, and R ⁵ and R ⁶ , and R ¹⁵ and R ¹⁶ may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring, and a bond via a single bond, an oxygen atom, or a sulfur atom is preferred.

In general formula (1), ^X1 and ^X2 are preferably represented by general formula (2).

In the general formula (2), R ²¹ to R ²⁶ each independently represent a hydrogen atom,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent.

In general formula (2), examples of the "straight-chain or branched alkyl group having ¹ to 20 carbon atoms" in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent ^" represented by R ²¹ to R ²⁶ include the same as the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 in general formula (1).

In general formula (2), examples of the "straight-chain or branched alkenyl group having ² to ²⁰ carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R ²¹ to R ^{26, include the same as the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R 1 to R 20 in general formula (1)} .

In general formula (2), examples of the "straight-chain or branched alkynyl group having ² to ²⁰ carbon atoms" in the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R ²¹ to R ^{26, include the same as the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R 1 to R 20 in general formula (1)} .

In general formula (2), examples 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 ²¹ to R ²⁶ include the same as the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "straight-chain or branched alkoxy group having ¹ to 20 carbon atoms" in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent ^" represented by R ²¹ to R ^{26 include the same as the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20 in general formula (1} ).

In general formula (2), examples of the "cycloalkoxy group having 3 to 10 carbon atoms" in the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R ²¹ to R ²⁶ include the same as the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "thio group having 1 to 18 carbon atoms" in the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ²¹ to R ²⁶ include the same as the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "amino group having 1 to 20 carbon atoms" in the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ²¹ to R ²⁶ include the same as the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ²¹ to R ²⁶ include the same as the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "heterocyclic group having 5 to 36 ring atoms" in the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ²¹ to R ²⁶ include the same as the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (2), examples of the "substituent" in "a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "a linear or branched alkenyl group having ² to ²⁰ carbon atoms which may have a substituent", "a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent", "a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "an alkoxy group having 1 to 20 carbon atoms which may have a substituent", "a linear or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent", "an acyl group having 1 to 20 carbon atoms which may have a substituent", "a thio group having 1 to 18 carbon atoms which may have a substituent", "an amino group having 1 to 20 carbon atoms which may have a substituent", "an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" or "a heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ²¹ to R 26 in general formula (1) include the following: Examples of the "substituent" include the same as those in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by ²⁰ .

In general formula (2), R ²¹ and R ²² , R ²³ and R ²⁴ , and R ²⁵ and R ²⁶ may be bonded to each other via a single bond, a bond via an oxygen atom, a sulfur atom, a selenium atom, or a bond via a nitrogen atom to form a ring.

In the general formula (2), ^Y1 represents a bond via an oxygen atom, a sulfur atom, or a selenium atom.

In general formula (2), m and n each represent an integer from 0 to 2. When m is 0, n is 1 or 2. When n is 0, m is 1 or 2. When either m or n is 1 or 2, the case where both are 0 is excluded. Preferably, m is 1. Furthermore, the cyclopentadithiophene moiety, which is the central skeleton of general formula (1), may be bonded to either the phenyl group or the five-membered heterocyclic group represented by general formula (2).

In general formula (2), it is preferable that m is 1 and n is 0 or 1. When m is 1 and n is 1 in general formula (2), it is preferable that a five-membered heterocyclic group is bonded to the cyclopentadithiophene portion, which is the central skeleton of general formula (1).

Specific examples of the compound represented by general formula (1) of the present invention are shown below, but the present invention is not limited to these. Furthermore, the following example compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted, and are examples of possible isomers, but all other isomers are included. Furthermore, each may be a mixture of two or more isomers.

The compound represented by general formula (1) can be used as a hole transport material for a photoelectric conversion element.

In the present invention, the hole transport material for a photoelectric conversion element may be a combination of one or more compounds represented by general formula (1), or may be a combination of other hole transport materials not belonging to the present invention. In the present invention, when a compound represented by general formula (1) is used in combination with another material, it is preferable to use it in combination with a compound represented by general formula (3), and it is even more preferable to use it in combination with a compound represented by general formula (4), general formula (5), or general formula (6).

Specific examples of compounds represented by general formula (3) are described below, but the present invention is not limited to these.

In general formula (3), R ²⁷ and R ²⁸ each independently represent
nitrile groups,
a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms;
a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent;
a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
Alternatively, it represents a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent.

In general formula (3), specific examples of the "linear or branched perfluoroalkyl group having 1 to 4 carbon atoms" represented by R ²⁷ and R ²⁸ include linear or branched alkyl groups having 1 to 4 carbon atoms in which hydrogen atoms have been completely substituted with fluorine atoms (perfluorinated), such as methyl, ethyl, n-propyl, and n-butyl groups.

In general formula (3), examples of the "acyl group having 1 to 20 carbon atoms" in the "acyl group having 1 to 20 carbon atoms which may have a substituent" represented by R ²⁷ and R ²⁸ include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a benzoylacetyl group, a benzoyl group, etc., and when it contains an alkyl chain, it includes one in which all hydrogen atoms are substituted with fluorine atoms (perfluorinated). It may also be one bound to an amino group (-CO-N<).

In general formula (3), in the "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ²⁷ and R ²⁸ , specific examples of the "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms" include a methoxycarbonyl group, an ethoxycarbonyl group, etc., and when it contains an alkyl chain, it also includes those in which hydrogen atoms are completely substituted with fluorine atoms (perfluorinated).

In general formula (3), specific examples of the "thio group having 1 to 18 carbon atoms" in the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ²⁷ and R ²⁸ include a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, and a biphenylthio group.

In general formula (3), specific examples of the "amino group having 1 to 20 carbon atoms" in the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ²⁷ and R ²⁸ include monosubstituted amino groups such as ethylamino, acetylamino, and phenylamino, and disubstituted amino groups such as diethylamino, diphenylamino, and acetylphenylamino.

In general formula (3), the "linear or branched alkylsulfonyl group having 1 to 18 carbon atoms" in the "linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ²⁷ and R ²⁸ is specifically a group represented by -SO ₂ A ¹ (A ¹ represents the above-mentioned linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent), and examples of A ¹ include the methyl group, ethyl group, n-propyl group, n-butyl group, etc. which are given as examples of the above-mentioned linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent.

In general formula (3), examples of the "substituents" in the "optionally substituted acyl group of 1 to 20 carbon atoms,""optionally substituted ^linear or branched alkoxycarbonyl group of 1 to ¹⁸ carbon atoms,""optionally substituted linear or branched alkoxycarbonyl group,""optionally substituted linear or branched alkoxysulfonyl group of 1 to 18 carbon atoms,""optionally substituted thio group,""optionally substituted amino group of 1 to 20 carbon atoms," and "optionally substituted linear or branched alkylsulfonyl group of 1 to 18 carbon atoms," represented by R ²⁷ and R ²⁸ , can be the same as the "substituents" in the "optionally substituted linear or branched alkyl group of 1 to 18 carbon atoms," represented by R 1 to R 20 in general formula (1).

In general formula (3), it is preferable that R ²⁷ and R ²⁸ are each independently a nitrile group, a linear or branched acyl group of 1 to 18 carbon atoms which may have a substituent, or a linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent. R ²⁷ and R ²⁸ may also be a nitrile group. R ¹ may also be a nitrile group, and R ² may also be a linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent. R ²⁷ and R ²⁸ may also be a linear or branched alkoxycarbonyl group of 1 to 18 carbon atoms which may have a substituent. R ²⁷ and R ²⁸ may also be a linear or branched acyl group of 1 to 18 carbon atoms which may have a substituent, and may be bonded to each other to form a ring.

In general formula (3), ^R27 and ^R28 may be bonded to each other via a single bond, a bond via an oxygen atom, a sulfur atom, or a selenium atom, or a bond via a nitrogen atom to form a ring, and in this case, in the present invention, the ring is preferably formed via a single bond.More preferably, the ring is an acidic heterocycle such as a barbituric acid type, a thiobarbituric acid type, a rhodanine type, a thiohydantoin type, or an indandione type.

In the general formula (3), ^X1 and ^X2 each independently represent the same as those represented by the general formula (2).

In general formula (3), R ²⁹ to R ³² each independently represent
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent.

In general formula (3), examples of the "aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ²⁹ to R ³² include the same as the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (3), examples of the "heterocyclic group having 5 to 36 ring atoms" in the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ²⁹ to R ³² include the same as the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (3), examples of the "substituents" in the "optionally substituted aromatic hydrocarbon group having 6 to 36 carbon atoms" and the "optionally substituted heterocyclic group having 5 to 36 ring atoms" represented by R ²⁹ to R ³² include the same as the "substituents" in the "optionally substituted linear or branched alkyl group having 1 to 18 carbon atoms" represented by R ¹ to R ²⁰ in general formula (1).

In general formula (3), R ²⁹ and R ³⁰ , and R ³¹ and R ³² may be bonded to each other via a single bond, a bond via an oxygen atom, a sulfur atom or a selenium atom, or a bond via a nitrogen atom to form a ring.

The compound represented by general formula (3) is preferably represented by general formulas (4) to (6).

In the general formulae (4) to (6), R ²⁷ and R ²⁸ are each independently represented by the same groups as "R ²⁷ and R ²⁸ represented in the general formula (3)".

In the general formulae (4) to (6), X ¹ and X ² are each independently represented by the general formula (2) in the same manner as "X ¹ and X ² represented in the general formula (3)".

In the general formulae (4) to (6), R ³³ to R ⁵² each independently represent
hydrogen atom, halogen atom, trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent.

In the general formulae (4) to (6), examples of the " ^{straight-chain} or ^branched alkyl group having 1 to 20 carbon atoms" in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by R ³³ to R ^{52 include the same as the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R 20} in the general formula (1).

In the general formulae (4) to (6), examples of the " ^{straight-chain} or branched alkenyl group having 2 to ²⁰ carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R ³³ to R ^{52, include the same as the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R 1 to R 20} in the general formula (1).

In the general formulae (4) to (6), examples of the " ^straight- chain or branched alkynyl group having 2 to ²⁰ carbon atoms" in the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R ³³ to R ^{52, include the same as the "straight-chain or branched alkynyl group having 2 to 20 carbon atoms, which may have a substituent," represented by R 1 to R 20} in the general formula (1).

In the general formulae (4) to (6), examples 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 ³³ to R ⁵² include the same as the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the " ^{straight-chain} or ^branched alkoxy group having 1 to 20 carbon atoms" in the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by R ³³ to R 52 include the same as the "straight-chain or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by R 1 to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the "cycloalkoxy group having 3 to 10 carbon atoms" in the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R ³³ to R ⁵² include the same as the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulas (4) to (6), examples of the "thio group having 1 to 18 carbon atoms" in the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ³³ to R ⁵² include the same as the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the "amino group having 1 to 20 carbon atoms" in the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ³³ to R ⁵² include the same as the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the "aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent ^" represented by R ³³ to R 52 include the same as the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the "heterocyclic group having 5 to 36 ring atoms" in the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ³³ to R ⁵² include the same as the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by R ¹ to R ²⁰ in the general formula (1).

In the general formulae (4) to (6), examples of the "substituent" in the "linear or branched alkyl group of 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group of ² to ²⁰ carbon atoms which may have a substituent", "linear or branched alkynyl group of 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group of 3 to 10 carbon atoms which may have a substituent", "alkoxy group of 1 to 20 carbon atoms which may have a substituent", "linear or branched cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent", "acyl group of 1 to 20 carbon atoms which may have a substituent", "thio group of 1 to 18 carbon atoms which may have a substituent", "amino group of 1 to 20 carbon atoms which may have a substituent", "aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent" or "heterocyclic group of 5 to 36 ring atoms which may have a substituent" represented by R 33 to R 52 in the general formula (1) include R ¹ to R Examples of the "substituent" include the same as those in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by ²⁰ .

"R ³³ to R ³⁷ , R ³⁸ to R ⁴² , R ⁴³ to R ⁴⁷ , R ⁴⁸ to R ⁵² " in general formula (4), and "R ³³ to R ³⁶ , R ³⁹ to R ⁴² , R ⁴³ to R ⁴⁶ , R 49 to R ⁵² " in general formulas ( ⁵ ) and (6) may be bonded to each other via a single bond, a bond via an oxygen atom, a sulfur atom or a selenium atom, or a bond via a nitrogen atom to form a ring.

Specific examples of the compound represented by general formula (3) of the present invention are shown below, but the present invention is not limited to these. Furthermore, the following example compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted, and are merely examples of possible isomers, encompassing all other isomers. Each compound may also be a mixture of two or more isomers.

The hole transport material for photoelectric conversion elements of the present invention, represented by the general formula (1), can be synthesized by known methods. A synthesis example for the case where m in general formula (2) is 1 and n is 0 in general formula (1) is shown below.

It can be synthesized by the Suzuki-Miyaura cross-coupling reaction between a dibromo compound represented by the following formula (7) and a boronic acid compound represented by general formulas (8) and (9) or a boronic acid ester compound represented by general formulas (10) and (11).

The hole transport material for photoelectric conversion elements of the present invention, represented by formula (7) above, can be synthesized by known methods. A synthesis example of general formula (3) where m in general formula (2) is 1 and n is 0 is shown below.

The dibromo compound represented by general formula (3) can be synthesized by subjecting it to a Suzuki-Miyaura cross-coupling reaction with a boronic acid compound represented by general formula (12) and general formula (13) or a boronic acid ester compound represented by general formula (14) and general formula (15), followed by a Knoevenagel condensation reaction with a compound represented by general formula (16).

The hole transport materials for photoelectric conversion elements represented by general formula (1) and general formula (3) of the present invention can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, etc. Alternatively, it is effective to use a combination of these methods to increase the purity of the compound. Furthermore, these compounds can be identified by nuclear magnetic resonance analysis (NMR).

The compound represented by general formula (3) is preferably mixed with the compound represented by general formula (1) and used as a hole transport material for a photoelectric conversion element. The content of the compound represented by general formula (3) is preferably 3 to 96% by mass, and more preferably 50 to 94% by mass. By using a mixture of the compound represented by general formula (1) and the compound represented by general formula (3), the advantages of the compound represented by general formula (1), which tends to have a high open-circuit voltage, and the advantage of the compound represented by general formula (3), which tends to have a high short-circuit current, are maintained, and better effects than when used alone can be expected.

Preferred embodiments of the photoelectric conversion element of the present invention are described below.

As shown in FIG. 1, the photoelectric conversion element of the present invention preferably comprises, but is not limited to, a conductive support (electrode) 1, an electron transport layer 2, a photoelectric conversion layer 3, an intermediate layer 4, a hole transport layer 5, and a counter electrode 6. Furthermore, the photoelectric conversion element of the present invention is preferably used as a solar cell, and is more preferably a perovskite-type photoelectric conversion element, but is not limited to this. In the present invention, the perovskite-type photoelectric conversion element preferably comprises, in this order, a conductive support (electrode) 1, an electron transport layer 2, a photoelectric conversion layer (perovskite layer) 3, an intermediate layer 4, a hole transport layer 5, and a counter electrode 6. Alternatively, the element may be configured in the order of a conductive support, a hole transport layer, a photoelectric conversion layer (perovskite layer), an electron transport layer, and a counter electrode.

<Conductive Support>
In the photoelectric conversion element of the present invention, the conductive support must be translucent enough to transmit light that contributes to photoelectric conversion. Furthermore, since the conductive support is a member that functions to extract current from the photoelectric conversion layer, it is preferably a conductive substrate. Specific examples of conductive materials include conductive transparent oxide semiconductors such as tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), zinc-aluminum oxide (AZO), fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), and indium-tin composite oxide. However, amorphous oxides such as tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), and tungsten-doped indium oxide (IWO) are preferably used.

Furthermore, the conductive support (transparent conductive layer) preferably has a sheet resistance of 100 Ω/□ or less, more preferably 50 Ω/□ or less, and preferably 0.1 Ω/□ or more.

<Electron transport layer>
In the photoelectric conversion element of the present invention, the electron transport layer 2 shown in FIG. 1 is a layer located between the conductive support (electrode) 1 and the photoelectric conversion layer 3, and it is preferable that the electron transport layer is formed on the conductive support (electrode) 1. The electron transport layer can be used to improve the efficiency of electron migration from the photoelectric conversion layer to the electrode while blocking the migration of holes. The form of the electron transport layer is not particularly limited, but it is preferably a thin film having a porous structure. The porous structure significantly increases the active surface area of the photoelectric conversion layer, improving photoelectric conversion efficiency and providing an electron transport layer with excellent electron collection.

In the present invention, specific examples of the semiconductor forming the electron transport layer include metal oxides such as 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 titanate (SrTiO3 _{, etc.} ), and tin oxide (SnO, _SnO2 , _SnO3 , etc.); metal sulfides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, and silver sulfide; metal selenides such as titanium selenide, zirconium selenide, indium selenide, and tungsten selenide; and elemental semiconductors such as silicon and germanium. It is preferable to use one or more of these semiconductors. In the present invention, it is preferable to use one or more semiconductors selected from titanium oxide, zinc oxide, and tin oxide.

In the present invention, the paste containing the semiconductor fine particles may be a commercially available product, or a paste (electron transport layer coating liquid) prepared by dispersing commercially available semiconductor fine powder in a solvent may be used. Specific examples of solvents used in preparing the paste include, but are not limited to, water; alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or in combination.

In the present invention, semiconductor fine powder can be dispersed in a solvent by grinding the powder in a mortar or the like, or by using a dispersing machine such as a ball mill, paint conditioner, vertical bead mill, horizontal bead mill, or attritor. When preparing the paste, it is preferable to add a surfactant or the like to prevent aggregation of the semiconductor fine particles, and it is also preferable to add a thickener such as polyethylene glycol to increase the viscosity.

In the present invention, the electron transport layer can be obtained using a known film-forming method depending on the material to be formed. The electron transport layer can be formed by any coating method using a coating liquid. Examples of methods include, but are not limited to, wet coating methods such as spin coating, inkjet printing, doctor blade printing, drop casting, squeegee printing, screen printing, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor printing, impregnation/coating, or curtain coating of a paste containing semiconductor particles onto a conductive substrate, followed by baking to remove solvents and additives; sputtering, vapor deposition, electrodeposition, electrodeposition, and microwave irradiation. In the present invention, spin coating using the electron transport layer coating liquid prepared by the above method is preferably used to form a film, but is not limited thereto. The atmosphere in which the film is formed is not particularly limited and may be air.

The film thickness of the electron transport layer is not particularly limited, but when a porous (mesoporous) metal oxide is used, it is usually preferably 20 to 200 nm or less, and more preferably 50 to 150 nm. In the present invention, when a dense electron transport layer is used instead of a mesoporous layer, the thickness of the electron transport layer is usually preferably 5 nm to 100 nm, and more preferably 10 nm to 50 nm. Furthermore, a non-crystalline (amorphous) thin film that does not have a crystalline structure may be partially formed.

In the present invention, the film thickness of each layer can be measured by observing the cross section of the photoelectric conversion element using a scanning electron microscope (SEM) or the like.

<Photoelectric conversion layer>
In the photoelectric conversion element of the present invention, it is preferable that a photoelectric conversion layer 3 is formed on the electron transport layer 2 shown in FIG.

In the present invention, when used as a perovskite photoelectric conversion element, the perovskite material of the photoelectric conversion layer represents a series of materials having a structure represented by the general formula ABX _3. Here, A, B, and X represent an organic cation or a monovalent metal cation, a metal cation, and a halide anion, respectively, and examples thereof include A=Cs ⁺ , CH ₃ NH ₃ ⁺ (MA), CH ₃ CH ₂ NH ₃ ⁺ (EA), and NH=CHNH ₂ ⁺ (FA); B=Pb, Sn; and X=Br, I. _{More specifically , CH3NH3PbI3 , C2H5NH3PbI3 , CH3NH3PbBr3 , C2H5NH3PbBr3 , CH3NH3PbBr3 , C2H5NH3PbCl3 , CH3NH3PbCl3 , C2H5NH3PbCl3 , CsSnI3 , CH3NH3SnI3 , C2H5NH3SnI3 , CsSnBr3 , CH3NH3SnBr3 , C2H5NH3SnBr3 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​} Layers containing perovskite materials _such as, but _{not limited to, CsSnCl3, CH3NH3SnCl3, C2H5NH3SnCl3 , CsPbI2Br , and mixed} cations expressed by any composition of ( _FA ,MA)Pb(Br,I) ₃ (FA is formamide, MA is methylammonium) can be used. It is preferable to use one or more of these perovskite materials. Furthermore, a light absorber other than the perovskite material may also be included.

The photoelectric conversion layer (perovskite layer) of the photoelectric conversion element of the present invention can be coated with a coating liquid using any coating method, including the same methods as those used to form the electron transport layer.

Commercially available materials may be used as the perovskite precursor. In the present invention, it is preferable to use a precursor of lead iodide (PbI ₂ ), formamide iodide, methylammonium halide or ethylammonium halide, and cesium iodide (CsI), or a precursor of lead (II) iodide and cesium bromide in any composition, but the present invention is not limited to these.

From the viewpoint of precursor solubility, examples of solvents for the perovskite precursor solution of the present invention include, but are not limited to, dimethyl sulfoxide, dimethylformamide, and γ-butyrolactone. These solvents may be used alone or in combination of two or more, and it is preferable to use a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

In the present invention, the atmosphere during film formation of the perovskite material is preferably a dry atmosphere, more preferably a dry inert gas atmosphere such as a glove box, from the viewpoint of preventing moisture contamination and enabling the reproducible production of highly efficient perovskite solar cells. It is also preferable to perform dehydration and use a solvent with a low moisture content.

In the present invention, the temperature at which the photoelectric conversion layer (perovskite layer) is heated using a hot plate or the like is preferably 50 to 200°C, more preferably 70 to 190°C, from the viewpoint of generating a perovskite material from the precursor. Furthermore, the heating time is preferably approximately 10 to 90 minutes, more preferably approximately 10 to 60 minutes.

The thickness of the photoelectric conversion layer (perovskite layer) of the present invention is preferably 50 to 1,000 nm, more preferably 300 to 700 nm, from the viewpoint of further suppressing performance degradation due to defects and peeling, and in order to ensure that the photoelectric conversion layer has sufficient light absorption and physical properties that do not result in an excessively high resistance value.

<Middle class>
In the photoelectric conversion element of the present invention, the intermediate layer 4 shown in FIG. 1 is a layer having a function of making the interlayer junction structure continuous and increasing the efficiency of charge transfer, and is a layer located between the photoelectric conversion layer and the hole transport layer.

In the present invention, it is preferable to use a compound having a quaternary ammonium salt structure in the intermediate layer, but this is not limited to this, and multiple compounds may be used in combination. Specific examples include phenylethylammonium bromide and n-hexyltrimethylammonium bromide.

Any coating method can be used to coat the intermediate layer of the photoelectric conversion element of the present invention with a coating liquid, including the same methods as those used to form the electron transport layer. The film is preferably formed in a dry atmosphere. A reduced pressure method is preferred over a heating method for removing the solvent from the coating liquid.

There are no particular restrictions on the thickness of the intermediate layer as long as it is effective in increasing the efficiency of charge transfer, but a thickness of 10 nm or less is preferred, and 5 nm or less is more preferred.

<Hole transport layer>
In the photoelectric conversion element of the present invention, the hole transport layer 5 shown in FIG. 1 is a layer having a function of transporting holes and is located between the intermediate layer 4 and the counter electrode 6. The hole transport layer can be used to improve the efficiency of hole transfer from the photoelectric conversion layer to the electrode while blocking the transfer of electrons. For example, a conductor, a semiconductor, an organic hole transport material, etc. can be used for the hole transport layer, and it may contain a dopant (oxidizing agent) as an additive for the purpose of further improving the hole transport properties.

The hole transport layer of the present invention is a layer containing the compound represented by the general formula (1) as a hole transport material, or may be a layer containing the compound represented by the general formula (1) and the compound represented by the general formula (3).
By using a compound represented by general formula (1) in a hole transport layer, or by using a hole transport layer containing a compound represented by general formula (1) and a compound represented by general formula (3), it is possible to construct a photoelectric conversion element and a solar cell that achieve excellent photoelectric conversion efficiency. Furthermore, by using a compound represented by general formula (1) in a hole transport layer, or by using a hole transport layer containing a compound represented by general formula (1) and a compound represented by general formula (3), it is possible to construct a photoelectric conversion element and a solar cell that can achieve stable photoelectric conversion efficiency without undergoing a time-lapse process after element fabrication, and it is possible to construct a hole transport material for a photoelectric conversion element that achieves stable photoelectric conversion efficiency without undergoing a post-treatment process such as aging after element fabrication, and a photoelectric conversion element and a solar cell that use the same.
In the hole transport layer of the present invention, one or more of the compounds represented by the general formula (1) and the compounds represented by the general formula (3) may be used in combination, and they may also be used in combination with other hole transport materials not belonging to the present invention.

Specific examples of hole transport materials other than those of the present invention include compound semiconductors containing monovalent copper, such as CuI, CuInSe ₂ , and CuS; and compounds containing metals other than copper, such as GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , and Cr ₂ O _3. These metal oxides may be mixed in the hole transport layer or may be laminated on the hole transport material. Examples of organic hole transport materials include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA); diphenylamine derivatives; polysilane derivatives; and polyaniline derivatives.

The hole transport layer of the present invention is preferably formed by coating and drying on the intermediate layer. Specific film formation methods include spin coating, screen printing, roll coating, dip coating, spraying, knife coating, bar coating, die coating, and curtain coating, with spin coating being preferred in the present invention. The spin coating conditions can be set as appropriate.

In the present invention, the solvents used in the hole transport layer coating solution (or mixed hole transport layer coating solution) during film formation include aromatic organic solvents such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, and nitrobenzene; alkyl halide organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, and dichloromethane; nitrile solvents such as benzonitrile and acetonitrile; and tetrahydrofuran. Examples of suitable solvents include, but are not limited to, ether solvents such as furan, dioxane, diisopropyl ether, c-pentyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate and propylene glycol monomethyl ether acetate; and alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, and 2-n-butoxyethanol. These solvents may be used alone or in combination, and the solvent to be used can be selected based on the solvent's structure. Aromatic organic solvents and halogenated alkyl organic solvents are particularly preferred.

In the present invention, there are no particular restrictions on the conditions for drying the hole transport layer after it has been applied as described above, but it is desirable to dry it to the extent that the solvent can be removed. It is preferable to heat it at approximately 50 to 120°C using a hot plate or the like, and the heating time is preferably approximately 10 to 60 minutes.

In the present invention, the thickness of the hole transport layer is preferably 5 to 500 nm, more preferably 10 to 200 nm, and even more preferably 10 to 100 nm, from the viewpoint of further improving photoelectric conversion efficiency.

In the present invention, the hole transport layer is preferably formed in a dry atmosphere, from the viewpoint of preventing the incorporation of moisture and enabling the reproducible production of highly efficient perovskite solar cells. It is also preferable to perform dehydration and use a solvent with a low moisture content.

<Additives>
In the present invention, the hole transport layer may contain a dopant (or an oxidizing agent) or a basic compound (or a basic additive) as an additive. Incorporating an additive into the hole transport layer to increase the carrier concentration of the hole transport material in the hole transport layer (doping) leads to an improvement in the conversion efficiency of the photoelectric conversion element. In the present invention, when the hole transport layer contains a dopant and a basic additive as additives, the amount of the additive is preferably about 3.5 equivalents or less per equivalent of the hole transport material.

In the present invention, when a dopant is contained, specific examples of the dopant include tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, NOSbF ₆ , SbCl ₅ , SbF ₅ , and the like. In the present invention, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), but the dopant is not limited to this.

When a dopant is used in the present invention, it is preferably used in an amount of 2.0 equivalents or less, and more preferably 0.5 equivalents or less, per equivalent of the hole transport material contained in the hole transport layer.

In the present invention, a basic compound (basic additive) may be contained as an additive in the hole transport layer. Specific examples of basic compounds that can be contained in the present invention include 4-tert-butylpyridine (tBP), 2-picoline, and 2,6-lutidine. Basic compounds are often used in combination with dopants. In the present invention, it is also desirable to use a basic compound in combination with a dopant.

When a basic compound is used in the present invention, it is preferably used in an amount of 5 equivalents or less per equivalent of the hole transport material of the present invention.

Opposite
1 is disposed opposite the conductive support and formed on the hole transport layer 5, thereby enabling exchange of charges with the hole transport layer. In the photoelectric conversion element of the present invention, it is preferable to provide a metal electrode as a counter electrode on the hole transport layer 5, but it is also possible to add an electron blocking layer made of an organic material or an inorganic compound semiconductor between the hole transport layer 5 and the counter electrode 6.

Specific examples of materials used for the counter electrode in the present invention include metals such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, magnesium, chromium, cobalt, and copper, as well as alloys of these metals. Of these, it is preferable to use gold, silver, or a silver alloy, as these exhibit high electrical conductivity even in thin films. Examples of silver alloys include silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper-palladium alloys, and silver-platinum alloys, which are less susceptible to sulfidation or chlorination and improve the stability of thin films.

In the present invention, the counter electrode is preferably made of a material that can be formed by methods such as vapor deposition.

When a metal layer is used as the counter electrode, its thickness is preferably 10 nm or more, more preferably 50 nm or more, to ensure good conductivity. Furthermore, a metal layer with a visible light transmittance of 60% or more can be used as a transparent electrode. In this case, to maintain light transmittance, the thickness is preferably 15 nm or less, more preferably 10 nm or less.

In the photoelectric conversion element of the present invention, the conductive support serves as the cathode, and the counter electrode serves as the anode. It is preferable to irradiate light such as sunlight from the conductive support side. When irradiated with sunlight, the photoelectric conversion layer (perovskite layer) absorbs the light and enters an excited state, generating electrons and holes. These electrons travel through the electron transport layer, and the holes travel through the hole transport layer to the electrode, causing a current to flow, and the element functions as a photoelectric conversion element.

When evaluating the performance (characteristics) of the photoelectric conversion element of the present invention, the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency are measured. The short-circuit current density represents the current per ^cm2 that flows between the output terminals when the terminals are short-circuited, and the open-circuit voltage represents the voltage between the output terminals when the terminals are open. The fill factor is the maximum output (product of current and voltage) divided by the product of the short-circuit current density and the open-circuit voltage, and is mainly dependent on the internal resistance. The photoelectric conversion efficiency is calculated as a percentage by multiplying the maximum output (W) by the light intensity (W) ^per cm2 by 100.

The photoelectric conversion element of the present invention can be applied to perovskite solar cells, various optical sensors, and the like. The perovskite solar cell of the present invention is obtained by arranging the required number of cells into a module and providing the required electrical wiring, and using a photoelectric conversion element that contains, as a hole transport layer, a hole transport material for photoelectric conversion elements containing a compound represented by general formula (1) above, or a hole transport material for photoelectric conversion elements containing a compound represented by general formula (1) above and a compound represented by general formula (3).

The above describes a preferred embodiment, but the present invention is not limited to this and may be modified as appropriate without departing from the scope of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The compounds obtained in the synthesis examples were identified by ^1H -NMR (1H-NMR (JNM-ECZ400S/L1 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd.)).

Synthesis Example 1 Synthesis of Compound (A-1) 3,3'-Dibromo-5,5'-bis(trimethylsilyl)-2,2'-bithiophene (10.0 g, manufactured by TCI) was added to a reaction vessel and the atmosphere was replaced with argon. Dehydrated tetrahydrofuran (106 mL) was added, and the mixture was cooled to -78°C in a dry ice-acetone bath. A hexane solution of n-butyllithium (1.55 mol/L, 29.0 mL, manufactured by Kanto Chemical Co., Inc.) was added dropwise. The mixture was then heated to -30°C over 4 hours, and dimethylcarbamoyl chloride (1.2 mL, manufactured by TCI) was added. After stirring at -30°C for 20 minutes, the mixture was gradually heated to 0°C over 3 hours. The mixture was then heated to room temperature. Water (150 mL) was added, and the mixture was separated. The organic layer was washed with water (150 mL) and saturated brine (100 mL). The aqueous layer was extracted three times with chloroform (40 mL). The organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off to obtain a red solid as a crude product. This crude product was purified using a silica gel column (hexane/ethyl acetate = 97/3 (volume ratio)) to obtain the compound represented by the following formula (17) as a red solid (yield: 5.76 g, 80%).

A reaction vessel was charged with the compound represented by the following formula (17) (3.5 g) and tetrahydrofuran (hereafter referred to as THF, 21 mL) and cooled to below 5°C in an ice bath. N-bromosuccinimide (4.9 g, manufactured by TCI) and N,N-dimethylformamide (hereafter referred to as DMF, 7 mL) were added in several portions. The mixture was then returned to room temperature and stirred for 2 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (400 mL). After stirring for 30 minutes, the solution was filtered. The resulting solid was dried under reduced pressure at 70°C to obtain the compound represented by the following formula (18) as a purple solid (yield: 3.53 g, 97%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 7.00 (2H).

A reaction vessel was charged with the compound of formula (18) (0.88 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (2.10 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.12 g, manufactured by Kanto Chemical), potassium carbonate (0.90 g, manufactured by Kanto Chemical), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL), followed by degassing under reduced pressure. The mixture was heated under reflux for 6 hours under an argon atmosphere. After the reaction was completed, toluene (10 mL) and water (10 mL) were added. The mixture was separated, and the aqueous layer was extracted twice with toluene (20 mL). The organic layer was concentrated, and the crude product was purified using a silica gel column (toluene/acetone = 100/1 (volume ratio)). Purification again using a silica gel column (toluene) yielded the compound represented by formula (A-1) below as a dark green powder (yield: 1.86 g, 93%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 3.80 (12H), 6.84 (8H), 6.90 (4H), 7.05 (2H), 7.08 (8H), 7.31 (4H).

[Synthesis Example 2] Synthesis of Compound (A-8)

4-Bromoanisole (10.60 g, manufactured by TCI), diphenylamine (8.72 g, manufactured by TCI), palladium acetate (0.015 g), sodium t-butoxide (11.90 g, manufactured by Kanto Chemical), tri-t-butylphosphine (0.017 g, manufactured by Kanto Chemical), and toluene (110 mL) were placed in a reaction vessel and degassed under reduced pressure. The mixture was heated under reflux for 3 hours under an argon atmosphere. After the reaction was complete, the mixture was cooled and subjected to suction filtration. The residue was washed with toluene (50 mL), and the filtrate was concentrated. The resulting crude product was purified using an amino silica gel column (toluene/hexane = 1/1 (volume ratio)) and then recrystallized (toluene/methanol) to obtain the compound represented by formula (19) below as a white solid (yield: 11.02 g, 78%).

A reaction vessel was charged with the compound of formula (19) below (10.50 g) and THF (71 mL) and cooled to below 5°C. N-bromosuccinimide (14.30 g, manufactured by TCI) was then added and stirred at below 5°C for 2 hours. After the reaction was complete, the reaction solution was poured into a beaker containing 300 mL of water. Toluene (100 mL) was then added. The mixture was separated, and the aqueous layer was extracted twice with toluene (40 mL). The organic layer was dried over sodium sulfate and concentrated. The crude product was purified using a silica gel column (toluene/hexane = 1:1 (volume ratio)), yielding the compound represented by formula (20) below as a yellow oil (yield: 16.50 g, 100%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 3.80 (3H), 6.84 (2H), 6.89 (4H), 7.02 (2H), 7.30 (4H).

A reaction vessel was charged with the compound of formula (20) (16.40 g), 4,4'-dimethoxydiphenylamine (2.90 g, manufactured by TCI), tris(dibenzylideneacetone)dipalladium(0) (0.68 g, manufactured by Kanto Chemical), sodium t-butoxide (3.67 g, manufactured by Kanto Chemical), 1,1'-bis(diphenylphosphino)ferrocene (0.56 g, manufactured by Kanto Chemical), and toluene (25 mL), and the mixture was degassed under reduced pressure. The mixture was heated to reflux under an argon atmosphere for 4 hours. After the reaction was completed, the mixture was cooled to below 40°C and subjected to suction filtration. The residue was washed with toluene (50 mL), and the filtrate was concentrated. The crude product was purified using a silica gel column (toluene/hexane = 1/1 (volume ratio)), yielding the compound represented by formula (21) below as a yellow solid (yield: 2.76 g, 38%).

A reaction vessel was charged with the compound of formula (21) (10.0 g) and anhydrous THF (130 mL) and degassed under reduced pressure. Under an argon atmosphere, the mixture was cooled to below -70°C in an acetone-dry ice bath. A solution of n-butyllithium in hexane (1.55 M, 17.0 mL, manufactured by Kanto Chemical Co., Inc.) was added dropwise in small amounts. After the addition was complete, the mixture was stirred at below -70°C for 1 hour, and then triisopropyl borate (6.0 mL, manufactured by TCI) was added dropwise. After the addition was complete, the mixture was gradually warmed to room temperature and stirred at room temperature for 1 hour. Water (55 mL) was added to the reaction mixture to terminate the reaction. The reaction mixture was separated, and the aqueous layer was extracted twice with toluene (40 mL). The organic layer was dried over sodium sulfate and concentrated. The crude product was purified using a silica gel column (toluene → THF) to obtain the compound represented by formula (22) as a yellow powder (yield: 5.75 g, 62%).

¹ H-NMR (400 MHz, DMSO-d ₆ ): δ (ppm) = 3.67 (6H), 3.73 (3H), 6.75 (4H), 6.8-6.9 (8H), 6.98-7.02 (6H), 7.59 (2H), 7.75 (2H).

A reaction vessel was charged with the compound of formula (18) (1.00 g), the compound of formula (22) (4.59 g), potassium carbonate (19.0 g, manufactured by Kanto Chemical), tetrakis(triphenylphosphine)palladium(0) (0.15 mg, manufactured by Kanto Chemical), and toluene (150 mL) and degassed. The mixture was then heated under reflux for 68 hours under an argon atmosphere. After the reaction was completed, the mixture was cooled to below 50°C and filtered through Celite. The residue was washed with toluene (100 mL), and the filtrate was concentrated. The crude product was subjected to silica gel column purification (toluene → toluene/acetone = 100/1 (volume ratio)). It was then purified again using a silica gel column (toluene/acetone = 100/1 (volume ratio)) to obtain the compound represented by formula (A-8) below as a dark green powder (yield: 1.34 g, 40%).

^1H -NMR (400MHz, DMSO- _d6 ): δ (ppm) = 3.72 (12H), 3.75 (6H), 6.7-6.8 (8H), 6.91 (8H), 6.95 (8H), 7.01 (8H), 7.05 (4H), 7.29 (2H), 7.46 (4H).

Synthesis Example 3 Synthesis of Compound (A-10) 3,6-Dibromocarbazole (5.0 g, manufactured by TCI), 1-chloro-4-fluorobenzene (7.83 g, manufactured by TCI), cesium carbonate (19.5 g, manufactured by Kanto Chemical), and DMF (15 mL) were placed in a reaction vessel. The mixture was stirred at 130°C for 38 hours under an argon atmosphere. After completion of the reaction, the reaction solution was poured into a beaker containing saturated saline (250 mL). This was filtered, and the residue was washed with water (50 mL) and methanol (10 mL). The crude product was purified using a silica gel column (toluene) to obtain a compound represented by the following formula (23) as a white powder (yield: 6.04 g, 92%).

¹ H-NMR (400 MHz, DMSO-d ₆ ): δ (ppm) = 7.34 (2H), 7.60 (2H), 7.69 (2H), 7.74 (2H), 8.60 (2H).

A reaction vessel was charged with the compound represented by formula (23) (5.0 g), 4,4'-dimethoxydiphenylamine (5.27 g, manufactured by TCI), palladium acetate (0.11 g, manufactured by Kanto Chemical), sodium t-butoxide (5.19 g, manufactured by Kanto Chemical), tri-t-butylphosphine (33% xylene solution) (0.67 g, manufactured by Kanto Chemical), and toluene (30 mL), and the mixture was degassed under reduced pressure under an argon atmosphere. The mixture was heated and refluxed for 4 hours, and after the reaction was completed, the reaction solution was filtered through Celite. The residue was washed with toluene (30 mL), and the filtrate was concentrated. The crude product was purified using a silica gel column (toluene → toluene/acetone = 100/1 (volume ratio)), yielding the compound represented by formula (24) below as a yellow powder (yield: 3.10 g, 39%).

A reaction vessel was charged with the compound represented by formula (24) below (3.10 g), bispinacolatodiboron (2.13 g, manufactured by TCI), potassium acetate (2.06 g, manufactured by Kanto Chemical), 1,1'-bis(diphenylphosphino)ferrocenedichloropalladium (0.343 g, manufactured by Kanto Chemical), and 1,4-dioxane (27 mL), and the mixture was degassed under reduced pressure under an argon atmosphere. The mixture was heated to reflux for 37 hours, and after the reaction was complete, the mixture was cooled to below 40°C and filtered through Celite. The filtrate was concentrated, and the crude product was purified using a silica gel column (toluene/acetone = 200/1 (volume ratio)). It was then purified again using a silica gel column (toluene), yielding the compound represented by formula (25) below as a yellow powder (yield: 2.56 g, 74%).

¹ H-NMR (400 MHz, DMSO-d ₆ ): δ (ppm) = 1.33 (12H), 3.69 (12H) 6.80-6.89 (16H), 7.07 (2H), 7.35 (2H), 7.63 (2H), 7.71 (2H), 7.93 (2H).

The compound of formula (18) (0.43 g), the compound of formula (25) (2.56 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical), potassium carbonate (0.44 g, manufactured by Kanto Chemical), toluene (7 mL), ethanol (2 mL), and water (2 mL) were added to a reaction vessel and degassed under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After the reaction was completed, toluene (20 mL) and water (10 mL) were added. The mixture was separated, and the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified using a silica gel column (toluene/acetone = 100/1 (volume ratio)), yielding the compound represented by formula (A-10) below as a dark blue powder (yield: 1.65 g, 84%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.68 (24H) 6.72 (16H), 6.91 (16H), 7.08 (4H), 7.31 (4H), 7.53 (2H), 7.63-7.66 (8H), 7.90 (4H).

Synthesis Example 4 Synthesis of Compound (A-12) A reaction vessel was charged with the compound of formula (18) (0.43 g), the compound of formula (26) (2.04 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL), and the mixture was degassed under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. The mixture was separated, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified using a silica gel column (toluene) and a silica gel column (toluene:hexane = 2/1 (volume ratio)), and a compound represented by formula (A-12) was obtained as a black-purple powder (yield: 1.42 g, 86%).

^1H -NMR (400MHz, THF- _d8 ): δ (ppm) = 6.84 (8H), 7.00 (16H), 7.13 (16H), 7.19 (4H), 7.39 (4H), 7.55 (2H), 7.68 (4H), 7.86 (4H), 7.93 (4H).

Synthesis Example 5 Synthesis of Compound (A-13) A reaction vessel was charged with the compound of formula (18) (0.43 g), the compound of formula (27) (2.52 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL), and the mixture was degassed under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. The mixture was separated, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified using a silica gel column (toluene/ethyl acetate = 50/1 (volume ratio)), and a compound represented by formula (A-13) was obtained as a black powder (yield: 1.52 g, 75%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.67 (24H) 6.65 (16H), 6.84 (16H), 6.96 (4H), 7.11 (4H), 7.35 (2H), 7.55-7.58 (8H), 7.80 (4H).

Synthesis Example 6 Synthesis of Compound (A-14) The compound of formula (10) (0.43 g), the compound of formula (28) (2.48 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL) were placed in a reaction vessel and degassed under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. The mixture was separated, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified using a silica gel column (toluene/ethyl acetate = 50/1 (volume ratio)), and the compound represented by formula (A-14) was obtained as a black powder (yield: 1.52 g, 77%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.68 (24H) 6.68 (16H), 6.88 (16H), 7.00 (4H), 7.15 (4H), 7.39 (2H), 7.60-7.63 (8H), 7.85 (4H).

Synthesis Example 7 Synthesis of Compound (A-25) A reaction vessel was charged with the compound of the following formula (29) (0.32 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (0.49 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical), potassium carbonate (0.22 g, manufactured by Kanto Chemical), toluene (4 mL), ethanol (1.3 mL), and water (1.3 mL), and the mixture was degassed under reduced pressure. The mixture was stirred under reflux for 6 hours under an argon atmosphere. After completion of the reaction, the reaction solution was poured into water (100 mL). 20 mL of toluene was added thereto, and the mixture was separated. The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified using a silica gel column (toluene) to obtain a compound represented by the following formula (A-25) as a dark green powder (yield: 0.40 g, 69%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.73 (12H), 6.81-6.88 (12H), 7.02 (8H), 7.13 (2H), 7.16 (4H), 7.38 (4H).

Synthesis Example 8 Synthesis of Compound (A-26) A reaction vessel was charged with the compound of formula (29) (0.32 g), the compound of formula (30) (1.15 g), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.22 g, manufactured by Kanto Chemical Co., Inc.), toluene (4 mL), ethanol (1.3 mL), and water (1.3 mL), followed by degassing under reduced pressure. The mixture was stirred under reflux for 6 hours under an argon atmosphere. After completion of the reaction, the reaction solution was poured into water (100 mL). Toluene (20 mL) was added, followed by separation. The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified using a silica gel column (toluene/ethyl acetate = 40/1 (volume ratio)), yielding a compound represented by formula (A-26) as a dark green powder (yield: 0.64 g, 61%).

^1H -NMR (400MHz, THF- _d8 ): δ (ppm) = 3.61 (24H), 6.62-6.65 (16H), 6.80-6.84 (16H), 7.00 (4H), 7.17 (2H), 7.23 (6H), 7.38 (2H), 7.53-7.58 (8H), 7.80 (4H).

Synthesis Example 9 Synthesis of Compound (B-1) Compound (A-1) (0.20 g), malononitrile (0.07 g, manufactured by TCI), and THF (30 mL) were placed in a reaction vessel. The mixture was stirred under an argon atmosphere. 1.6 mL of an acetic acid-pyridine (1:1 (volume ratio)) solution was added thereto. The mixture was stirred for 20 hours under reflux with heating. After completion of the reaction, the reaction solution was placed in a beaker containing water (50 mL). The mixture was separated, and the organic layer was washed twice with water (50 mL). The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified using a silica gel column (toluene) to obtain a compound represented by the following formula (B-1) as a black-purple powder (yield: 0.17 g, 81%).

Synthesis Example 10 Synthesis of Compound (B-13) The compound of formula (18) (0.88 g), 4-(diphenylamino)phenylboronic acid (1.73 g, Sigma-Aldrich), tetrakis(triphenylphosphine)palladium(0) (0.12 g, Kanto Chemical), potassium carbonate (0.90 g, Kanto Chemical), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL) were placed in a reaction vessel, and the mixture was degassed under reduced pressure. The mixture was heated under reflux for 13 hours under an argon atmosphere. After completion of the reaction, the reaction solution was placed in a beaker containing ethanol (50 mL). The mixture was filtered and washed twice with water (50 mL) and then with ethanol (20 mL). The crude product was purified using a silica gel column (toluene → chloroform). The crystals were then dispersed and washed with toluene, yielding the compound represented by the following formula (31) as a dark blue powder (yield: 1.14 g, 67%).

1H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 7.01 (8H), 7.06 (8H), 7.23 (8H), 7.25 (2H), 7.47 (4H).

The compound of formula (31) (0.60 g), malononitrile (0.23 g, manufactured by TCI), and THF (50 mL) were placed in a reaction vessel and stirred under an argon atmosphere. An acetic acid-pyridine (1:1) solution (5.6 mL) was then added. The mixture was stirred for 32 hours under reflux. After the reaction was complete, the reaction solution was placed in a beaker containing water (300 mL). This was filtered and washed with water (20 mL) and methanol (20 mL). The crude product was dispersed and washed with acetone and recrystallized (chloroform), yielding the compound represented by formula (B-13) below as a black powder (yield: 0.44 g, 69%).

1H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 7.01 (8H), 7.06 (8H), 7.23 (8H), 7.45 (4H), 7.49 (2H).

[Synthesis Example 11] Synthesis of Compound (B-14)

The compound of formula (A-8) (0.57 g), malononitrile (0.13 g, manufactured by TCI), and THF (15 mL) were placed in a reaction vessel and stirred under an argon atmosphere. An acetic acid-pyridine (volume ratio 1:1) solution (3.6 mL) was then added. The mixture was stirred for 6 hours under reflux. After the reaction was complete, water (30 mL) and toluene (20 mL) were added. The mixture was separated, and the aqueous layer was extracted twice with toluene (30 mL). The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified using a toluene column to obtain the compound represented by formula (B-14) below as a dark green powder (yield: 0.493 g, 83%).

^1H -NMR (400MHz, DMSO- _d6 ): δ (ppm) = 3.72 (12H), 3.73 (6H), 6.7-6.8 (8H), 6.89 (8H), 6.92 (8H), 7.00 (8H), 7.05 (4H), 7.23 (2H), 7.33 (4H).

Synthesis Example 12 Synthesis of Compound (B-15) The compound of formula (A-10) (0.56 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were placed in a reaction vessel and stirred under an argon atmosphere. To this was added an acetic acid-pyridine (1:1) solution (2.6 mL). The mixture was stirred for 16 hours under reflux with heating. After completion of the reaction, water (30 mL) was added. The mixture was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform/acetone) to obtain a compound represented by formula (B-14) below as a green powder (yield: 0.52 g, 91%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.68 (24H) 6.72 (16H), 6.91 (16H), 7.08 (4H), 7.3 (4H), 7.66 (8H), 7.76 (2H), 7.90 (4H).

Synthesis Example 13 Synthesis of Compound (B-16) The compound of formula (A-12) (0.60 g), malononitrile (0.12 g, manufactured by TCI), and THF (19 mL) were placed in a reaction vessel and stirred under an argon atmosphere. To this was added an acetic acid-pyridine (1:1) solution (3.2 mL). The mixture was stirred for 54 hours under reflux with heating. After completion of the reaction, the reaction solution was poured into water (200 mL). This was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was washed with toluene and then recrystallized (chloroform/acetone) to obtain the compound represented by formula (B-16) below as a green powder (yield: 0.30 g, 48%).

^1H -NMR (400MHz, THF- _d8 ): δ (ppm) = 6.84 (8H), 7.00 (16H), 7.13 (16H), 7.19 (4H), 7.39 (4H), 7.55 (2H), 7.68 (4H), 7.86 (4H), 7.93 (4H).

Synthesis Example 14 Synthesis of Compound (B-17) The compound of formula (A-13) (0.56 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were placed in a reaction vessel and stirred under an argon atmosphere. To this was added an acetic acid-pyridine (1:1) solution (2.6 mL). The mixture was stirred for 16 hours under reflux with heating. After completion of the reaction, water (30 mL) was added. The mixture was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform/acetone) to obtain the compound represented by formula (B-17) below as a green powder (yield: 0.51 g, 88%).

¹ H-NMR (400 MHz, THF-d ₈ ): δ (ppm) = 3.67 (24H) 6.65 (16H), 6.84 (16H), 6.96 (4H), 7.11 (4H), 7.57 (8H), 7.59 (2H), 7.80 (4H).

Synthesis Example 15 Synthesis of Compound (B-18) The compound of formula (A-13) (0.55 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were placed in a reaction vessel and stirred under an argon atmosphere. To this was added an acetic acid-pyridine (1:1) solution (2.6 mL). The mixture was stirred for 16 hours under reflux with heating. After completion of the reaction, water (30 mL) was added. The mixture was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform/acetone) to obtain the compound represented by formula (B-18) below as a green powder (yield: 0.51 g, 90%).

1H-NMR (400MHz, THF-d ₈ ): δ (ppm) = 3.68 (24H) 6.68 (16H), 6.88 (16H), 7.00 (4H), 7.15 (4H), 7.62 (8H), 7.64 (2H), 7.85 (4H).

Synthesis Example 16 Synthesis of Compound (B-19) The compound (1.33 g) of the following formula (32), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (2.10 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.12 g, manufactured by Kanto Chemical), potassium carbonate (0.90 g, manufactured by Kanto Chemical), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL) were placed in a reaction vessel, and the mixture was degassed under reduced pressure. The mixture was heated under reflux for 6 hours under an argon atmosphere. After completion of the reaction, toluene (10 mL) and water (10 mL) were added. The mixture was separated, and the aqueous layer was extracted twice with toluene (20 mL). The organic layer was concentrated, and the crude product was purified using a silica gel column (toluene) to obtain the compound represented by the following formula (B-19) as a dark green powder (yield: 2.11 g, 86%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 1.32 (6H), 3.81 (12H), 4.59 (4H), 6.84 (8H), 6.90 (4H), 7.08 (8H), 7.33 (4H) 7.69 (2H).

Synthesis Example 17 Synthesis of Compound (B-20) The compound of formula (A-1) (0.6 g), diethyl malonate (0.37 g, manufactured by TCI), and THF (14 mL) were placed in a reaction vessel and stirred under an argon atmosphere. The mixture was cooled to 5°C or below in an ice bath, and carbon tetrachloride (0.9 mL, manufactured by Junsei Chemical Co., Ltd.), titanium tetrachloride (0.5 mL, manufactured by Wako Pure Chemical Industries, Ltd.), and THF (8 mL) were added. The mixture was cooled again to 5°C or below, and pyridine (1 mL) and THF (1 mL) were added. The mixture was then warmed to room temperature and stirred at room temperature for 17 hours. After completion of the reaction, the reaction solution was poured into a beaker containing 50 mL of water, and toluene (30 mL) was added thereto. The mixture was separated, and the organic layer was washed twice with 10% aqueous sodium carbonate solution (50 mL). The organic layer was dried over magnesium sulfate and then concentrated. The crude was purified using a silica gel column (toluene) to obtain a compound represented by the following formula (B-20) as a dark green powder (amount: 0.56 g, yield: 79%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 1.38 (6H), 3.81 (12H), 4.40 (4H), 6.84 (8H), 6.90 (4H), 7.07 (8H), 7.31 (4H), 7.36 (2H).

Synthesis Example 18 Synthesis of Compound (B-21) The compound of formula (A-1) (0.6 g), methyl cyanoacetate (0.23 g, manufactured by TCI), and THF (14 mL) were charged into a reaction vessel and stirred under an argon atmosphere. The mixture was cooled to below 5°C in an ice bath, and carbon tetrachloride (0.9 mL, manufactured by Junsei Chemical Co., Ltd.), titanium tetrachloride (0.5 mL, manufactured by Wako Pure Chemical Industries, Ltd.), and THF (8 mL) were charged. The mixture was cooled again to below 5°C, and pyridine (1 mL) and THF (1 mL) were charged. The mixture was then warmed to room temperature and stirred for 18 hours at room temperature and 14 hours at 60°C. After completion of the reaction, the reaction solution was poured into a beaker containing (50 mL) water, and toluene (30 mL) was added thereto. The mixture was separated, and the organic layer was washed twice with 10% aqueous sodium carbonate solution (50 mL). The organic layer was dried over magnesium sulfate and then concentrated. The crude was purified using a silica gel column (toluene) to obtain a compound represented by the following formula (B-21) as a dark green powder (amount: 0.51 g, yield: 77%).

¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 3.81 (12H), 3.95 (3H), 6.84 (8H), 6.90 (4H), 7.07 (8H), 7.34 (4H), 7.68 (1H), 7.82 (1H).

Synthesis Example 19 Synthesis of Compound (B-22) Formula (A-25) (0.35 g), diethyl malonate (0.27 mL, manufactured by TCI), and THF (11 mL) were placed in a reaction vessel and stirred under an argon atmosphere. Pyridine (0.48 mL, manufactured by Nacalai Tesque) was then added. Titanium tetrachloride (0.24 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was then added. The mixture was stirred at room temperature for 9 hours. After completion of the reaction, the reaction solution was placed in a beaker containing water (150 mL). This was filtered, washed with water (30 mL) and methanol (20 mL), and dried. The crude product was purified using a silica gel column (toluene/ethyl acetate = 50/1 (volume ratio)) to obtain a compound represented by the following formula (B-22) as a dark green powder (yield: 0.32 g, 82%).

^1H -NMR (400MHz, THF- _d8 ): δ (ppm) = 1.35 (6H), 3.73 (12H), 4.39 (4H), 6.81-6.88 (12H), 7.02 (8H), 7.12 (2H), 7.15 (2H), 7.39-7.42 (6H).

Synthesis Example 20 Synthesis of Compound (B-23) The compound of formula (A-26) (0.32 g), malononitrile (0.05 g, manufactured by TCI), and THF (8 mL) were placed in a reaction vessel and stirred under an argon atmosphere. A mixed solution of acetic acid and pyridine (volume ratio = 1:1) (1.4 mL) was added thereto, and the mixture was heated under reflux for 20 hours. After completion of the reaction, the reaction solution was poured into a beaker containing 150 mL of water. The mixture was filtered, washed with water (20 mL) and methanol (20 mL), and then dried. The crude product was purified using a silica gel column (toluene/ethyl acetate = 40/1 (volume ratio)), and the compound represented by the following formula (B-23) was obtained as a dark green powder (yield: 0.26 g, 81%).

^1H -NMR (400MHz, THF- _d8 ): δ (ppm) = 3.67 (24H), 6.69-6.71 (16H), 6.88-6.90 (16H), 7.07 (4H), 7.28-7.31 (6H), 7.47 (4H), 7.61 (4H), 7.64 (4H), 7.89 (4H).

[Example 1]
<Formation of Electron Transport Layer>
A coating liquid for the electron transport layer was prepared by adding ultrapure water to an aqueous colloidal dispersion of tin oxide (manufactured by Alfa Aesar, 1.75 wt %) to dilute it to 1/10.

An ITO substrate was used as the conductive support, and was ultrasonically cleaned in an aqueous solution containing a 2% volume concentration of alkaline detergent. The substrate was then washed with water and then ultrasonically cleaned in ethanol. The ITO substrate was then subjected to a 10-minute UV ozone treatment. The electron transport layer coating solution was then dropped onto the ITO substrate and spin-coated at 5,000 rpm for 30 seconds using a spin coater. The resulting thin film was then heated on a hot plate at 150°C for 40 minutes.

In the fabricated photoelectric conversion element, the electron transport layer made of tin oxide formed on the ITO substrate was a porous _SnO2 film with a thickness of approximately 20 nm. Furthermore, the crystallinity of the electron transport layer was examined by X-ray diffraction, and it was found that a thin film of non-crystalline (amorphous) tin oxide (SnOx) without a crystalline structure was partially formed on the surface of the _SnO2 .

<Photoelectric conversion layer (perovskite layer) deposition>
Lead iodide (1.2 M, PbI ₂ ), formamide iodide (1 M, FAI), methylammonium bromide (0.2 M, MABr), and cesium iodide (0.06 M, CsI) were weighed into a vial and dissolved in a 4:1 (volume ratio) solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). This solution was stirred at room temperature for 1 hour to prepare a 1.0 mol/L perovskite precursor solution. The perovskite precursor solution was stirred for an additional 30 minutes and then filtered through a PTFE filter with a pore size of 0.45 μm to obtain a coating solution for the photoelectric conversion layer.

In an atmosphere of 20% relative humidity, the photoelectric conversion layer coating solution was dropped onto an ITO substrate on which an electron transport layer had been formed, and then spin-coated at 1000 rpm for 10 seconds and 3000 rpm for 30 seconds. The thin film was then stored in the atmosphere for 10 minutes, and then heated on a hot plate at 180°C for 10 minutes to form a photoelectric conversion layer (perovskite layer) composed of mixed cations (FA, MA) and mixed halogens (I, Br) with the composition FA _0.83 MA _0.17 Pb(I _0.9 Br _0.05 ) _3. FA stands for formamide, and MA stands for methylammonium. The thickness of the photoelectric conversion layer was approximately 450-600 nm when examined using a scanning electron microscope (SEM).

<Formation of the intermediate layer>
4 mg of 2-phenylethylammonium bromide (PEABr) was dissolved in 2-propanol (1 mL) and stirred at 50°C for 2 hours. The PEABr solution was applied onto the photoelectric conversion layer (perovskite layer) by spin coating at 5000 rpm for 30 seconds. The applied film was left in a reduced pressure atmosphere of 0.05 kPa for 10 minutes to remove the solvent.

<Formation of Hole Transport Layer>
16 mg of compound (A-10) was weighed into a vial, 0.5 mL of dehydrated chlorobenzene was added, and the mixture was dissolved by ultrasonication for 60 minutes. 9.1 μL of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI, 340 mg/1 mL acetonitrile solution) and 9.8 μL of 4-tert-butylpyridine (tBP) were added, and the mixture was filtered through a PTFE filter with a pore size of 0.45 μm to prepare a coating solution for a hole transport layer.

The hole transport layer coating solution was applied onto the intermediate layer (PEABr film) by spin coating at 3000 rpm for 30 seconds to form a hole transport layer, which was then dried by heating at 110°C for 1 hour using a hot plate. The thickness of the hole transport layer was determined to be approximately 100 nm using a scanning electron microscope (SEM).

Gold was deposited onto the hole transport layer of the fabricated element using a resistance heating vacuum deposition method to form a metal counter electrode approximately 100 nm thick. Then, UV-curable epoxy resin was applied to the periphery of the element using a dispenser, and the element was sealed with resin by irradiating it with UV light.

<Evaluation of photoelectric conversion elements>
The resulting photoelectric conversion element was irradiated with simulated sunlight using a solar simulator at an air mass (AM) of 1.5 G and an irradiance of 100 mW/ ^cm² , and the current-voltage characteristics between the negative electrode (ITO) and the positive electrode were measured. A source meter (Keithley, Model 2400) was used for the measurements, and the short-circuit photocurrent (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency (PCE) (%) were calculated from the measurement results. These values, calculated based on the measurement results immediately after the photoelectric conversion element was fabricated, are shown in Table 1.

[Example 2]
Except for not using the intermediate layer, a photoelectric conversion element was produced in the same manner as in Example 1. Table 1 shows values calculated based on the measurement results immediately after the production of the photoelectric conversion element.

[Example 3]
16 mg of compound (A-1) was weighed into a vial, 1 mL of dehydrated chlorobenzene was added, and the solution was dissolved by ultrasonication for 60 minutes. 9.1 μL of bis(trifluoromethanesulfonyl)imide lithium (LiTFSI, 340 mg/1 mL acetonitrile solution) and 9.8 μL of 4-tert-butylpyridine (tBP) were added, and the solution was filtered through a PTFE filter with a pore size of 0.45 μm to prepare a compound (A-1) solution. 17 mg of compound (B-1) was weighed into a vial, 0.5 mL of dehydrated chlorobenzene was added, and the solution was dissolved by ultrasonication for 60 minutes. Similarly to compound (A-1), Li-TFSI solution and tBP were added, and the solution was filtered through a PTFE filter to obtain a compound (B-1) solution. The compound (A-1) solution and the compound (B-1) solution were mixed at a volume ratio of 1:3 to obtain a mixed hole transport layer coating solution. In this case, the molar ratio of compound (A-1) to compound (B-1) was 1:6. A photoelectric conversion element was prepared in the same manner as in Example 1, except for using this mixed hole transport layer coating liquid. Values calculated based on the measurement results immediately after preparing the photoelectric conversion element are shown in Table 1.

[Example 4]
A mixed hole transport layer coating liquid was prepared in the same manner as in Example 2, except that the mixing ratio of compound (A-1) and compound (B-1) was adjusted to a molar ratio of 1:8, and a photoelectric conversion element was produced in the same manner as in Example 1, except that this mixed hole transport layer coating liquid was used. Values calculated based on the measurement results immediately after the production of the photoelectric conversion element are shown in Table 1. Table 2 also shows the results of tracking the change in photoelectric conversion efficiency over time, with the time immediately after the production of the element set as 0 hours and 6 hours and 24 hours later.

[Example 5]
A mixed hole transport layer coating liquid was prepared in the same manner as in Example 2, except that the mixing ratio of compound (A-1) and compound (B-1) was adjusted to a molar ratio of 1:10, and a photoelectric conversion element was produced in the same manner as in Example 1, except that this mixed hole transport layer coating liquid was used. Table 1 shows values calculated based on the measurement results immediately after the production of the photoelectric conversion element.

[Comparative Example 1]
A photoelectric conversion element was prepared in the same manner as in Example 1, except that Spiro-OMeTAD (36.15 mg), a commercially available hole-transporting compound represented by the following formula (C-1), which is most widely used in perovskite solar cells, was used as the hole-transporting material. Table 1 shows the values calculated based on the measurement results 24 hours after preparation. Table 2 also shows the results of tracking the changes in photoelectric conversion efficiency over time, with the time immediately after preparation of the element set as 0 hours and 6 and 24 hours later.

The results in Table 1 show that the device using the hole transport material for photoelectric conversion device of the present invention provides a higher conversion efficiency than the device using a commercially available hole transport material for photoelectric conversion device.
It can be seen that the compound represented by general formula (1) exhibits sufficient photoelectric conversion efficiency even when used alone, and furthermore, by mixing it with the compound represented by general formula (3), it exhibits higher photoelectric conversion efficiency than the comparative example while maintaining the advantage of the compound of general formula (1), which tends to have a high open circuit voltage.

The results in Table 2 show that devices using the hole transport material for photoelectric conversion devices of the present invention do not require a holding time (time until device efficiency stabilizes) to stabilize device efficiency compared to devices using commercially available hole transport materials for photoelectric conversion devices, and achieve high efficiency immediately after device fabrication, making them advantageous for industrial production. It is said that the commercially available hole transport material for photoelectric conversion devices used in the comparative example requires time for device efficiency to stabilize. This is presumably because commercially available materials are relatively resistant to oxidation to oxidants that function as hole transport materials for photoelectric conversion devices. Because the compound of the present invention is easily oxidized to oxidants, it is believed that device efficiency stabilizes immediately after device fabrication.

[Example 6]
Lead (II) iodide and cesium bromide were weighed in a vial at a molar ratio of 1:1, and DMF and DMSO were added as solvents at a volume ratio of 6:4. The mixture was stirred at room temperature for 1 hour to prepare a 1.0 mol/L perovskite precursor solution whose entire composition was composed of inorganic elements. A photoelectric conversion layer coating solution was prepared using this solution, and a photoelectric conversion layer (perovskite layer) composed of CsPbI ₂ Br was formed. Except for this, compound (A-1) and compound (B-1) were mixed (volume ratio 1:4, molar ratio 1:8) and dissolved in the same manner as in Example 1 to prepare a hole transport layer coating solution. A photoelectric conversion element was fabricated using this hole transport layer coating solution, and measurements were performed. The results are shown in Table 3.

[Comparative Example 2]
A photoelectric conversion element was prepared in the same manner as in Example 6 except that Spiro-OMeTAD was used as the hole transport material, and measurements were carried out. The results are shown in Table 3.

The results in Table 2 show that elements using the hole transport material for photoelectric conversion elements of the present invention are superior to elements using commercially available hole transport materials for photoelectric conversion elements in that they have a higher open-circuit voltage and provide sufficient photoelectric conversion efficiency.

The use of the hole transport material for photoelectric conversion devices according to the present invention is useful for high-efficiency photoelectric conversion devices and perovskite solar cells, and can provide clean energy as solar cells that can efficiently convert solar energy into electrical energy.

1 Conductive support (electrode)
2 electron transport layer 3 photoelectric conversion layer 4 intermediate layer 5 hole transport layer 6 counter electrode

Claims (8)

A compound represented by the following general formula (1), in which ^X1 and ^X2 in general formula (1) are each independently represented by the following general formula (2).
[wherein R ³ , R ⁸ , R ¹³ and R ¹⁸ each independently represent a diphenylamino group which may have a substituent;
The "substituent" of the optionally substituted diphenylamino group is a linear or branched alkoxy group having 1 to 18 carbon atoms,
R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁹ and R ²⁰ represent a hydrogen atom.
.
^R5 and ^R6 , and ^R15 and ^R16 may be bonded to each other to form a ring.
wherein R ²¹ to R ²⁶ each independently represent a hydrogen atom,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or an optionally substituted heterocyclic group having 5 to 36 ring atoms,
R ²¹ and R ²² , R ²³ and R ²⁴ , and R ²⁵ and R ²⁶ may be bonded to each other to form a ring.
^Y1 represents an oxygen atom, a sulfur atom, or a selenium atom, and m and n each represent an integer of 0 to 2, provided that m is 1 and n is 0 . A hole transport material for a photoelectric conversion element containing the compound described in claim 1. A hole transport material for a photoelectric conversion element, which is a compound represented by the following general formula (1), wherein X1 and X2 in general formula (1) ^each independently ^contain a compound represented by the following general formula (2), and contains a compound represented by the following general formula (3):
[In the general formula (1) , R ¹ to R ²⁰ each independently represent a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent,
R ¹ to R ²⁰ each independently represent at least one of a halogen atom, a carboxyl group, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
or an acyl group having 1 to 20 carbon atoms which may have a substituent;
It shall have the following.
Adjacent groups of R ¹ to R ⁵ , R ⁶ to R ¹⁰ , R ¹¹ to R ¹⁵ , and R ¹⁶ to R ²⁰ may be bonded to each other to form a ring, and R ⁵ and R ⁶ , and R ¹⁵ and R ¹⁶ may be bonded to each other to form a ring.]
[In the general formula (2) , R ²¹ to R ²⁶ each independently represent a hydrogen atom,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or an optionally substituted heterocyclic group having 5 to 36 ring atoms,
R ²¹ and R ²² , R ²³ and R ²⁴ , and R ²⁵ and R ²⁶ may be bonded to each other to form a ring.
^Y1 represents an oxygen atom, a sulfur atom, or a selenium atom, and m and n each represent an integer of 0 to 2, provided that either m or n is 1 or 2.
In the general formula (3) , R ²⁷ and R ²⁸ each independently represent
nitrile groups,
a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms;
a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent;
a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
Alternatively, it represents a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ²⁹ to R ³² each independently represent
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or a heterocyclic group having 5 to 36 ring atoms which may have a substituent.
R ²⁹ and R ³⁰ , and R ³¹ and R ³² may be bonded to each other to form a ring.] 4. The hole transport material for a photoelectric conversion element according to claim 3 , wherein the compound represented by the general formula (3) is represented by the following general formulas (4) to (6):
In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent a hydrogen atom, a halogen atom, a trimethylsilyl group,
a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent;
a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent;
a linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent;
a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent;
a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent;
a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent;
an acyl group having 1 to 20 carbon atoms which may have a substituent;
a thio group having 1 to 18 carbon atoms which may have a substituent;
an amino group having 1 to 20 carbon atoms which may have a substituent;
an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
or an optionally substituted heterocyclic group having 5 to 36 ring atoms,
Adjacent groups of R ³³ to R ³⁷ , R ³⁸ to R ⁴² , R ⁴³ to R ⁴⁷ , and R ⁴⁸ to R ⁵² may be bonded to each other to form a ring.]
In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent the same groups as above,
Adjacent groups of R ³³ to R ³⁶ , R ³⁹ to R ⁴² , R ⁴³ to R ⁴⁶ , and R ⁴⁹ to R ⁵² may be bonded to each other to form a ring.]
In the formula, R ²⁷ and R ²⁸ each independently represent the same as defined above, and R ²⁷ and R ²⁸ may be bonded to each other to form a ring.
^X1 and ^X2 are each independently represented by the general formula (2),
R ³³ to R ⁵² each independently represent the same groups as above,
Adjacent groups of R ³³ to R ³⁶ , R ³⁹ to R ⁴² , R ⁴³ to R ⁴⁶ , and R ⁴⁹ to R ⁵² may be bonded to each other to form a ring.
^Z1 and ^Z2 each independently represent an oxygen atom, a sulfur atom, or a selenium atom. 5. The hole transport material for a photoelectric conversion element according to claim 3 , wherein the content of the compound represented by the general formula (3) is 3 to 96% by mass. The hole transport material for a photoelectric conversion element according to any one of claims 3 to 5 , wherein the content of the compound represented by general formula (3) is 50 to 94 mass %. A photoelectric conversion element using the hole transport material for photoelectric conversion elements according to any one of claims 2 to 6 . A solar cell using the photoelectric conversion element according to claim 7 .