JP7117696B2 - Photoelectric conversion element and solar cell module - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoelectric conversion element, and more preferably to a photoelectric conversion element containing a perovskite organic-inorganic hybrid semiconductor material as a photoelectric conversion substance in an active layer.

Conventionally, in a photoelectric conversion element such as a solar cell, a layer containing a photoelectric conversion substance is simply sandwiched between electrodes by laminating a charge transport layer adjacent to an active layer containing various photoelectric conversion substances and attaching electrodes to this layer. A high photoelectric conversion capability has been obtained for the photoelectric conversion element (see, for example, Patent Document 1).

WO2012/102390

However, lamination of the charge transport layer on the active layer increases the number of manufacturing processes, and when the number of layers increases, the heat resistance of each layer differs, so the manufacturing conditions are likely to be restricted. Become. An object of the present invention is to provide a photoelectric conversion element that has performance equal to or higher than that in the case of having a charge transport layer, even if it does not have a charge transport layer. Another object of the present invention is to provide a photoelectric conversion element in a short period of time with high productivity by simplifying the manufacturing process because it is not necessary to provide a charge transport layer.

The inventors of the present invention have conducted research to solve the above problems, and have found a structure with a simpler structure that can provide performance equivalent to that of a photoelectric conversion device having a charge transport layer, thereby completing the present invention.
At this stage, the details of the principle of the effect of the present invention are unknown. When the precursor is converted to a perovskite structure, a compound having at least one anionic substituent at the terminal is discharged from the perovskite crystal that is produced, and the terminal anionic substituent is formed on the surface of each perovskite crystal. It is presumed that it is deposited in a coordinated form, which facilitates the movement of charges in the active layer, and that even without a charge transport layer, it exhibits an effect equal to or greater than that of the presence of a charge transport layer. be. In addition, the coordination of terminal anionic substituents deactivates defects on the perovskite crystal surface and crystal interface, making it possible to maintain the crystal morphology in a stable manner. It is also thought that the effect of improving the sexuality is also considered.

（前記式（Ｉ）中、Ｘ^１とＸ^２の一方は置換基Ｒ^２を有する窒素原子であり、他方は置換基Ａｒ^３を有する炭素原子であり、Ｒ^１～Ｒ^４はそれぞれ独立して水素原子又は１価の有機基を表し、Ａｒ^１～Ａｒ^４はそれぞれ独立して置換基を有していてもよい芳香族基を表す。）
［７］前記式（Ｉ）において、Ｒ^１とＲ^２とのうちの少なくとも１つが置換基としてアニオン性の置換基を有する炭素数１～２０のアルキル基である［６］に記載の光電変換素子。
［８］前記式（Ｉ）において、Ａｒ^１～Ａｒ^４のうち少なくとも１つが置換基としてハロゲン原子を有する芳香族基である［６］または［７］に記載の光電変換素子。
［９］前記式（Ｉ）において、Ａｒ^１～Ａｒ^４のうち少なくとも１つが置換基としてフッ素原子を有する芳香族基である［６］から［８］のいずれかに記載の光電変換素子。
［１０］［１］から［９］のいずれかに記載の光電変換素子を有する太陽電池モジュール。 The present invention includes the following.
[1] A photoelectric conversion element having a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer containing an organic-inorganic hybrid semiconductor material positioned between the pair of electrodes,
The photoelectric conversion device, wherein the active layer contains a compound having at least one anionic substituent at the end thereof in an amount of 0.3% by weight or less relative to the content of the organic-inorganic hybrid semiconductor material.
[2] The photoelectric conversion device according to [1], wherein the organic-inorganic hybrid semiconductor material contains a compound having a perovskite structure.
[3] The photoelectric conversion device according to [1] or [2], wherein the compound having an anionic substituent has a HOMO level in the range of -5.20 eV to -5.90 eV.
[4] The photoelectric conversion device according to any one of [1] to [3], wherein the anionic substituent is a sulfonic acid group.
[5] any one of [1] to [4], wherein the HOMO level of the compound having an anionic substituent is within a range of ±0.3 eV with respect to the HOMO level of the organic-inorganic hybrid semiconductor; The photoelectric conversion device described.
[6] The photoelectric conversion device according to any one of [1] to [5], wherein the compound having an anionic substituent includes a compound represented by formula (I) below.

(In formula (I) above, one of X ¹ and X ² is a nitrogen atom having a substituent R ² , the other is a carbon atom having a substituent Ar ³ , and R ¹ to R ⁴ are each independently represents a hydrogen atom or a monovalent organic group, and Ar ¹ to Ar ⁴ each independently represents an optionally substituted aromatic group.)
[7] The photoelectric conversion according to [6], wherein at least one of R ¹ and R ² in formula (I) is an alkyl group having 1 to 20 carbon atoms and having an anionic substituent as a substituent. element.
[8] The photoelectric conversion device according to [6] or [7], wherein at least one of Ar ¹ to Ar ⁴ in formula (I) is an aromatic group having a halogen atom as a substituent.
[9] The photoelectric conversion device according to any one of [6] to [8], wherein at least one of Ar ¹ to Ar ⁴ in formula (I) is an aromatic group having a fluorine atom as a substituent.
[10] A solar cell module comprising the photoelectric conversion element according to any one of [1] to [9].

According to the present invention, it is possible to provide a photoelectric conversion element having performance equal to or higher than that of a photoelectric conversion element having a charge transport layer, even without the charge transport layer. Moreover, since there is no need to provide a charge transport layer, the manufacturing process can be simplified, and a photoelectric conversion element can be provided in a short time with good productivity.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which represents typically the photoelectric conversion element as one Embodiment. 1 is a cross-sectional view schematically showing a solar cell as one embodiment; FIG. 1 is a cross-sectional view schematically showing a solar cell module as one embodiment; FIG.

Embodiments of the present invention are described in detail below. The description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist of the present invention.

A photoelectric conversion element according to the present embodiment is a photoelectric conversion element having a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer containing an organic-inorganic hybrid semiconductor material positioned between the pair of electrodes. be. The active layer contains a specific amount of a compound having at least one anionic substituent at its terminal.

FIG. 1 is a cross-sectional view schematically showing one embodiment of a photoelectric conversion element according to the present invention. The photoelectric conversion element shown in FIG. 1 is a photoelectric conversion element used in a general thin-film solar cell, but the photoelectric conversion element according to the present invention is not limited to that shown in FIG. In the photoelectric conversion element 100 shown in FIG. 1, a lower electrode 101, an active layer 103, and an upper electrode 107 are arranged in this order, and the active layer 103 contains an organic-inorganic hybrid semiconductor material and has at least one including compounds with one anionic substituent. Further, the photoelectric conversion element 100 may have a buffer layer 102 between the lower electrode 101 and the active layer 103, and a buffer layer 105 between the upper electrode 107 and the active layer 103, respectively. Also, as shown in FIG. 1, the photoelectric conversion device 100 may have other layers such as a substrate 108, an insulator layer, and a work function tuning layer.

[1. active layer]
The active layer 103 is a layer in which photoelectric conversion is performed. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103 to generate carriers, which are extracted from the lower electrode 101 and the upper electrode 107 .

In this embodiment, the active layer 103 contains an organic-inorganic hybrid semiconductor material. An organic-inorganic hybrid semiconductor material is a material in which an organic component and an inorganic component are combined at the molecular level or the nano level, and indicates a material exhibiting semiconductor properties.

An example of an organic-inorganic hybrid semiconductor material is a compound having a perovskite structure (hereinafter sometimes referred to as a perovskite semiconductor compound). A perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. Although there are no particular restrictions on the perovskite semiconductor compound, for example, Galasso et al.
and Properties of Inorganic Solids, Chapter 7 - Perovskite type and related structures. For example, perovskite semiconductor compounds include those of the AMX ₃ type, represented by the general formula AMX ₃ , or those of the A ₂ MX ₄ type, represented by the general formula A ₂ MX ₄ . Here, M denotes a divalent cation, A denotes a monovalent cation, and X denotes a monovalent anion.

Although the monovalent cation A is not particularly limited, it is preferably an organic cation, and those described in the above-mentioned Galasso can be used. More specific examples include cations containing elements from Groups 1 and 13 to 16 of the long periodic table. Among these, cesium ions, rubidium ions, optionally substituted ammonium ions, and optionally substituted phosphonium ions are preferred. Examples of optionally substituted ammonium ions include primary ammonium ions and secondary ammonium ions. There are no particular restrictions on the substituents, either. Specific examples of optionally substituted ammonium ions include alkylammonium ions and arylammonium ions. In particular, in order to avoid steric hindrance, a monoalkylammonium ion having a three-dimensional crystal structure is preferable, and from the viewpoint of improving stability, it is preferable to use an alkylammonium ion substituted with one or more fluorine groups. A combination of two or more cations can also be used as the cation A.

Specific examples of the monovalent cation A include methylammonium ion, methylammonium monofluoride ion, methylammonium difluoride ion, methylammonium trifluoride ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, and isobutylammonium ion. , n-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidinium ion, formamidinium ion, acetamidinium ion or imidazolium ions and the like.

Although the divalent cation M is not particularly limited, it is preferably a divalent metal cation or metalloid cation. Specific examples include preferably long-period cations of Group 14 elements of the periodic table, and more specific examples include lead cations (Pb ²⁺ ), tin cations (Sn ²⁺ ), and germanium cations (Ge ²⁺ ). are mentioned. A combination of two or more cations can also be used as the cation M. From the viewpoint of obtaining a stable photoelectric conversion device, it is particularly preferable to use lead cations or two or more kinds of cations containing lead cations.

Examples of monovalent anions X include halide ions, acetate ions, nitrate ions, sulfate ions, borate ions, acetylacetonate ions, carbonate ions, citrate ions, sulfur ions, tellurium ions, thiocyanate ions, titanates. ions, zirconate ions, 2,4-pentanedionate ions, silicofluoride ions, and the like. In order to adjust the bandgap, X may be one type of anion or a combination of two or more types of anions. Among them, as X, it is preferable to use a halide ion or a combination of a halide ion and another anion. Examples of halide ions X include chloride ions, bromide ions, iodide ions, and the like. From the viewpoint of not widening the bandgap of the semiconductor too much, it is preferable to use iodide ions.

Preferred examples of perovskite semiconductor compounds include organic-inorganic perovskite semiconductor compounds, particularly halide-based organic-inorganic perovskite semiconductor compounds. _{Specific examples} of _{perovskite semiconductor compounds include CH3NH3PbI3 , CH3NH3PbBr3 , CH3NH3PbCl3 , CH3NH3SnI3 , CH3NH3SnBr3 , CH3NH3SnCl3 .} , CH ₃ NH ₃ PbI _(3-x) Cl _x , CH ₃ NH ₃ PbI _(3-x) Br _x , CH ₃ NH ₃ PbBr _(3-x) Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Br ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Cl ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y I _{(3 -x)} Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Br _x , and CH ₃ NH ₃ Pb _(1-y) Sn _y Br _(3-x) Cl _x , and , the above compounds in which CH ₃ NH ₃ is replaced with CFH ₂ NH ₃ , CF ₂ HNH ₃ , or CF ₃ NH ₃ , and the like. Note that x is 0 or more and 3 or less, and y is any value of 0 or more and 1 or less.

The active layer 103 may contain two or more perovskite semiconductor compounds. For example, the active layer 103 may contain two or more perovskite semiconductor compounds in which at least one of A, B and X is different. The active layer 103 may also have a laminated structure formed of multiple layers containing different materials or having different components.

The amount of the perovskite semiconductor compound contained in the active layer 103 is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more so as to obtain good semiconductor characteristics. be. There is no particular upper limit.

In this embodiment, the active layer 103 contains a compound having at least one anionic substituent at its end. By including a compound having at least one anionic substituent at the terminal in the active layer 103, it is possible to impart the same performance to the photoelectric conversion element as in the case of having a charge transport layer without having a charge transport layer. .
This anionic substituent is preferably a sulfonic acid group. The reason why sulfonic acid groups are preferred is that they have extremely high affinity for aprotic polar solvents such as DMF and DMSO, which are often used as solvents for active layer precursor solutions that give perovskite crystals such as MAPbI3. It is thought that it is due to the fact that it has ionization ability.
A compound having at least one terminal anionic substituent may be, for example, a compound represented by formula (I).

In formula (I), one of X ¹ and X ² is a nitrogen atom having a substituent R ² , the other is a carbon atom having a substituent Ar ³ , and R ¹ to R ⁴ are each independently hydrogen Each of Ar ¹ to Ar ⁴ independently represents an optionally substituted aromatic group. In formula (I), one of the two bonds indicated by dashed lines is a single bond and the other is a double bond.

At least ^one of R ¹ and R ² is preferably a group having an anionic substituent at its terminal, and is preferably an alkyl group having 1 to ²⁰ carbon atoms. and both are more preferably C 1-20 alkyl groups having an anionic substituent at the end. The number of carbon atoms in the alkyl group may be, for example, 2 or more, 3 or more, 4 or more, 16 or less, 12 or less, or 10 or less. good. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, and dodecanyl groups. Anionic substituents include, but are not limited to, sulfonic acid groups, carboxylic acid groups, carbonate groups, phosphoric acid groups, and the like.

On the other hand, R ¹ to R ⁴ each independently represent a hydrogen atom or a monovalent organic group. Examples of monovalent organic groups include acyl groups; hydrocarbon groups having 1 to 30 carbon atoms; and heterocyclic groups having 1 to 30 carbon atoms.

Examples of hydrocarbon groups having 1 to 30 carbon atoms include aliphatic hydrocarbon groups having 1 to 30 carbon atoms and aromatic hydrocarbon groups having 1 to 30 carbon atoms.

The aliphatic hydrocarbon group having 1 to 30 carbon atoms may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, it may be a linear hydrocarbon group, a branched hydrocarbon group, or a cyclic hydrocarbon group. The aliphatic hydrocarbon group having 1 to 30 carbon atoms includes an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, or an alkadienyl group having 4 to 30 carbon atoms. etc.

The alkyl group having 1 to 30 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, or dodecanyl groups. etc. can be mentioned. Another example of an alkyl group includes an aralkyl group such as a benzyl group.

The alkenyl group having 2 to 30 carbon atoms is preferably an alkenyl group having 2 to 10 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms. Examples of alkenyl groups include, but are not limited to, vinyl, allyl, propenyl, isopropenyl, 2-methyl-1-propenyl, 2-methylallyl, or 2-butenyl. can.

The alkynyl group having 2 to 30 carbon atoms is preferably an alkynyl group having 2 to 10 carbon atoms, more preferably an alkynyl group having 2 to 6 carbon atoms. Examples of alkynyl groups include, but are not limited to, ethynyl, propynyl, or butynyl groups.

The alkadienyl group having 4 to 30 carbon atoms is preferably an alkadienyl group having 4 to 10 carbon atoms, more preferably an alkadienyl group having 4 to 6 carbon atoms. Examples of alkadienyl groups include, but are not limited to, 1,3-butadienyl groups and the like.

The aromatic hydrocarbon group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include monocyclic aromatic hydrocarbon groups such as phenyl group; ring-linked aromatic hydrocarbon groups such as 2-biphenylyl group, 3-biphenylyl group, or 4-biphenylyl group; naphthyl group (1-naphthyl group or 2-naphthyl group), anthryl group (2-anthryl group or 9-anthryl group, etc.), or aromatic condensed ring group such as fluorenyl group; or alkylaryl group such as methylphenyl group; be done.

The heterocyclic group having 1 to 30 carbon atoms includes an aliphatic heterocyclic group having 1 to 30 carbon atoms and an aromatic heterocyclic group having 1 to 30 carbon atoms.

The aliphatic heterocyclic group having 1 to 30 carbon atoms is preferably an aliphatic heterocyclic group having 2 to 30 carbon atoms, more preferably an aliphatic heterocyclic group having 2 to 20 carbon atoms. Examples include a tetrahydrothienyl group or a piperidinyl group, or those to which an alkyl group is further bonded.

The aromatic heterocyclic group having 1 to 30 carbon atoms includes monocyclic aromatic heterocyclic groups, ring-linked aromatic heterocyclic groups, and condensed aromatic heterocyclic groups.

The monocyclic aromatic heterocyclic group preferably has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms. Preferred examples of monocyclic aromatic heterocyclic groups include 5- to 14-membered rings, more preferably 5- to 10-membered rings, more preferably 5- to 10-membered rings having 1 to 4 heteroatoms in addition to carbon atoms as ring-constituting atoms. includes a 5- or 6-membered monocyclic aromatic heterocyclic group. Examples of heteroatoms include nitrogen, sulfur and oxygen atoms, and the monocyclic aromatic heterocyclic group preferably contains one or two heteroatoms as ring-constituting atoms.

Specific examples of monocyclic aromatic heterocyclic groups include thienyl group (2-thienyl group or 3-thienyl group), furyl group (2-furyl group or 3-furyl group), pyridyl group (2-pyridyl group , 3-pyridyl group or 4-pyridyl group), thiazolyl group (2-thiazolyl group, 4-thiazolyl group or 5-thiazolyl group), oxazolyl group (2-oxazolyl group, 4-oxazolyl group or 5-oxazolyl group), pyrazinyl group, pyrimidinyl group (2-pyrimidinyl group, 4-pyrimidinyl group, or 5-pyrimidinyl group), pyrrolyl group (1-pyrrolyl group, 2-pyrrolyl group, or 3-pyrrolyl group), imidazolyl group (1 -imidazolyl group, 2-imidazolyl group, 4-imidazolyl group, or 5-imidazolyl group), pyrazolyl group (1-pyrazolyl group, 3-pyrazolyl group, or 4-pyrazolyl group), pyridazinyl group (3-pyridazinyl group or 4 -pyridazinyl group), isothiazolyl group (3-isothiazolyl group, etc.), isoxazolyl group (3-isoxazolyl group, etc.), imidazolyl group, or those further bonded with an alkyl group.

The condensed aromatic heterocyclic group preferably has 4 to 30 carbon atoms, more preferably 4 to 20 carbon atoms. Preferable examples of the condensed aromatic heterocyclic group include an 8- to 20-membered ring, more preferably a 9- to 14-membered ring having 1 to 4 heteroatoms other than carbon atoms as ring-constituting atoms. Ring or tricyclic aromatic heterocyclic groups can be mentioned. Another preferred example of the condensed aromatic heterocyclic group is a 5- to 14-membered (preferably 5- to 10-membered) 7- to 10-membered aromatic heterocyclic bridged ring containing 1 to 4 heteroatoms other than carbon atoms. A monovalent group formed by removing any one hydrogen atom is used. Examples of heteroatoms include nitrogen, sulfur and oxygen atoms, and the condensed aromatic heterocyclic group preferably contains one or two heteroatoms as ring-constituting atoms.

Specific examples of the condensed aromatic heterocyclic group include a quinolyl group (2-quinolyl group, 3-quinolyl group, 4-quinolyl group, 5-quinolyl group, 8-quinolyl group, etc.), an isoquinolyl group (1- isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, or 5-isoquinolyl group, etc.), indolyl group (1-indolyl group, 2-indolyl group, or 3-indolyl group, etc.), 2-benzothiazolyl group, benzo[b ] thienyl group (2-benzo[b]thienyl group or 3-benzo[b]thienyl group, etc.), benzo[b]furanyl group (2-benzo[b]furanyl group, 3-benzo[b]furanyl group, etc.) , or those to which an alkyl group is further bonded, and the like.

The ring-connected aromatic heterocyclic group preferably has 4 to 30 carbon atoms, more preferably 4 to 20 carbon atoms. Examples of ring-linked aromatic heterocyclic groups include those in which at least one of the aforementioned monocyclic aromatic heterocyclic groups, condensed aromatic heterocyclic groups, and aromatic hydrocarbon groups are bonded to each other.

The monovalent organic groups exemplified above may have further substituents. Further substituents include a hydroxyl group; a halogen atom such as a fluorine atom or a chlorine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group; an alkenyl group such as a vinyl group; alkoxycarbonyl group having 1 to 6 carbon atoms; alkoxy group having 1 to 6 carbon atoms such as methoxy group or ethoxy group; aryloxy group such as phenoxy group; arylalkyloxy group such as benzyloxy group; dimethylamino group, diethylamino group , a diisopropylamino group, a dibenzylamino group, or a diphenethylamino group; a diarylamino group such as a diphenylamino group or a carbazolyl group; an acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; group; nitro group; alkylenedioxy group having 1 to 3 carbon atoms such as methylenedioxy group or ethylenedioxy; ionic substituent;

Ionic substituents include acidic substituents or salts thereof, or quaternary ammonium groups. Examples of acidic substituents include sulfuric acid groups, including sulfonic acid groups (sulfo groups) and sulfinic acid groups (sulfino groups); a phosphate group including an acid ester group; or a carboxyl group. The salt of an acidic substituent refers to a substituent obtained by replacing the hydrogen ion of the acidic substituent with another cation. Specifically, the hydrogen atom of the above-mentioned acidic substituent is sodium or potassium or those substituted with alkaline earth metals such as calcium or magnesium. The quaternary ammonium group is preferably an ammonium group having three alkyl groups of 1 to 6 carbon atoms.

R ³ and R ⁴ are preferably a hydrogen atom or an organic group having 1 to 25 carbon atoms, and are preferably a hydrogen atom or an organic group having 1 to 20 carbon atoms, since they tend to improve intermolecular interaction. It is more preferable to have
Among them, when R ³ and / or R ⁴ is a substituent having a π-conjugated electron such as an aromatic group, or a substituent capable of controlling intermolecular packing such as an alkyl group, the amorphous property of the thin film can be increased, and the ability to form a thin film can also be improved.

On the other hand, when R ³ and/or R ⁴ is a hydrogen atom, the steric hindrance of compound (I) is reduced and the planarity of the main skeleton is not impaired, so that the intermolecular π-π interaction becomes strong, Charge mobility can be improved.
Therefore, more preferred examples of R ³ and R ⁴ are a hydrogen atom, an optionally substituted C 2 to C 20 aromatic group, or an optionally substituted C 1 to Twenty alkyl groups are mentioned.

Ar ¹ to Ar ⁴ in formula (I) each independently represent an optionally substituted aromatic group. Specific examples of Ar ¹ to Ar ⁴ include those given as examples of the aromatic hydrocarbon group or aromatic heterocyclic group for R ¹ to R ⁴ .

Selection of Ar ¹ to Ar ⁴ is expected to improve the heat resistance of the film by controlling the glass transition temperature, in addition to enhancing the amorphousness of the film. In order to increase amorphousness, substituents having π-conjugated electrons, specifically, aromatic groups such as benzene ring groups, biphenyl groups, and naphthyl groups are preferred. In order to increase the glass transition temperature, phenanthryl groups, carbazolyl groups and the like are preferred.

Among them, Ar ¹ to Ar ⁴ are each independently preferably an optionally substituted aromatic group having 5 to 20 carbon atoms, and may have an electron withdrawing group as a substituent. More preferably, it is an aromatic hydrocarbon group having 6 to 20 carbon atoms. In a particularly preferred example, at least one of Ar ¹ to Ar ⁴ is an aromatic hydrocarbon group having 6 to 20 carbon atoms having an electron withdrawing group as a substituent, or Ar ¹ to Ar ⁴ are each independently is an aromatic hydrocarbon group having 6 to 20 carbon atoms having an electron-withdrawing group as a substituent. It is preferable for Ar ¹ to Ar ⁴ to be an aromatic hydrocarbon group having 6 to 20 carbon atoms and having an electron withdrawing group as a substituent, since the carrier transport performance can be improved. Examples of electron withdrawing groups include halogen atoms such as fluorine atoms or chlorine atoms, cyano groups, acyl groups, nitro groups, haloalkyl groups, and the like. Among them, when the electron-withdrawing group is a halogen atom, the stability of the compound is improved, and thus the durability of the obtained photoelectric conversion device is also improved. Among them, the fluorine atom is particularly preferred.

Preferred groups for X ¹ , X ² , Ar ¹ to Ar ⁴ and R ¹ to R ⁴ may be arbitrarily selected from the groups listed above. The represented compound preferably has a point-symmetrical structure centered on the benzene ring. That is, it is preferred that X ¹ is a carbon atom having a substituent Ar ³ and X ² is a nitrogen atom having a substituent R ² . In this case, Ar ¹ is the same group as Ar ⁴ , Ar ² is the same group as Ar ³ , R ¹ is the same group as R ² , and R ³ is the same group as R ⁴ . preferable.

Examples of compounds having an anionic substituent represented by formula (I) are shown below.

Although the method for synthesizing the compound represented by formula (I) is not particularly limited, it can be synthesized, for example, according to the following reaction scheme. In addition, the starting compound can be synthesized according to a known method. For example, D. A. Kinsley, S.; G. P. Plants. J. Chem. Soc. , 1958, 1-7. Alternatively, the starting compound of the formula below can be synthesized by a coupling reaction between the corresponding diaminobenzene derivative and an alkynyl compound. In the reaction formula below, R ¹ to R ⁴ and Ar ¹ to Ar ⁴ have the same meanings as R ¹ to R ⁴ and Ar ¹ to Ar ⁴ in formula (I) above.

The molecular weight of the compound having at least one anionic substituent at the terminal is not particularly limited, but is usually 460 or more, preferably 500 or more, more preferably 600 or more, and usually 5000 or less, preferably 4000 or less, more preferably is 3000 or less.

A compound having at least one anionic substituent at its terminal preferably has a HOMO level in the range of -5.20 eV to -5.90 eV. Within this range, it is located in the vicinity of the HOMO level (MAPbI3: -5.40 eV) of the organic-inorganic hybrid semiconductor material, and is particularly preferable in that the energy barrier of the hole transport ability is small.
From another point of view, it is preferably within the range of ±0.3 eV, more preferably within the range of ±0.2 eV with respect to the HOMO level of the organic-inorganic hybrid semiconductor material. With such a range, the energy barrier becomes small when giving and receiving holes obtained by charge separation of light absorbed by the organic-inorganic hybrid semiconductor, and the loss of the open-circuit voltage Voc is reduced. is possible and preferable.

In addition, the compound having at least one anionic substituent at the end is contained in the active layer in an amount of 0.3% by weight or less with respect to the content of the organic-inorganic hybrid semiconductor material, thereby improving the photoelectric conversion efficiency. more preferably 0.2% by weight or less, and most preferably 0.1% by weight or less.

The active layer 103 may also contain an additive in addition to the perovskite semiconductor compound and the compound having at least one anionic substituent at the terminal. Examples of additives include inorganic or organic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts.

There is no particular limitation on the thickness of the active layer 103 . In that it can absorb more light, the active layer 10
The thickness of 3 is preferably 10 nm or more, more preferably 50 nm or more, more preferably 100 nm or more, and particularly preferably 120 nm or more. On the other hand, the thickness of the active layer 103 is preferably 1500 nm or less, more preferably 1000 nm or less, and still more preferably 600 nm or less in order to reduce the series resistance or improve the charge extraction efficiency.

A method for forming the active layer 103 is not particularly limited, and any method can be used. Specific examples include a coating method and a vapor deposition method (or a co-evaporation method). It is preferable to use the coating method because the active layer 103 can be easily formed. For example, the active layer 103 is formed by applying a coating liquid containing an organic-inorganic hybrid semiconductor material or a precursor thereof and a compound having at least one anionic substituent at the terminal, and drying by heating if necessary. method. Moreover, after applying such a coating liquid, the organic-inorganic hybrid semiconductor material can be precipitated by further applying a solvent in which the organic-inorganic hybrid semiconductor material has low solubility.

A precursor of an organic-inorganic hybrid semiconductor material refers to a material that can be converted into an organic-inorganic hybrid semiconductor material after application of a coating liquid. As an example, a perovskite semiconductor compound precursor that can be converted to a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general _formula MX2, and a solvent, followed by heating and stirring. The active layer 103 containing the perovskite semiconductor compound represented by the general formula AMX ₃ can be produced by applying this coating liquid and heat-drying it. The solvent is not particularly limited as long as it dissolves the perovskite semiconductor compound and the additive, and examples thereof include organic solvents such as N,N-dimethylformamide.

Any method can be used as a method for applying the coating liquid, and examples include spin coating, ink jet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, A spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation/coating method, a curtain coating method, or the like can be used.

[2. electrode]
The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 103 . The photoelectric conversion element 100 has a pair of electrodes, one of which is called an upper electrode and the other is called a lower electrode. When the photoelectric conversion element 100 has a substrate or is provided on a substrate, the electrode closer to the substrate can be called the lower electrode, and the electrode farther from the substrate can be called the upper electrode. Also, the transparent electrode can be called the lower electrode, and the electrode having lower transparency than the lower electrode can be called the upper electrode. A photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 107 .

As the pair of electrodes, an anode suitable for collecting holes and a cathode suitable for collecting electrons can be used. In this case, the photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 107 is the cathode, or a reverse configuration in which the lower electrode 101 is the cathode and the upper electrode 107 is the anode. It may have a mold configuration.

Either one of the pair of electrodes may be translucent, or both may be translucent. Having translucency refers to transmitting 40% or more of sunlight. In addition, it is preferable that the transparent electrode has a sunlight transmittance of 70% or more so that more light can pass through the transparent electrode and reach the active layer 103 . The light transmittance can be measured with a spectrophotometer (eg, U-4100 manufactured by Hitachi High-Tech).

There is no particular limitation on the lower electrode 101 and upper electrode 107, or the constituent members of the anode and cathode, and the manufacturing method thereof, and well-known techniques can be used. For example, members described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, or Japanese Patent Application Laid-Open No. 2012-191194 and manufacturing methods thereof can be used.

[3. buffer layer]
The buffer layer is a layer located between the active layer 103 and at least one of the pair of electrodes 101 and 107 . A buffer layer can be used, for example, to improve carrier transfer efficiency from the active layer 103 to the lower electrode 101 or the upper electrode 107 .

As described above, the photoelectric conversion device 100 can have the buffer layer 102 between the lower electrode 101 and the active layer 103, or have the buffer layer 105 between the upper electrode 107 and the active layer 103. can be done. Also, the photoelectric conversion element 100 can have both the buffer layer 102 and the buffer layer 105 . Here, the buffer layer 102 provided between the lower electrode 101 and the active layer 103 and the buffer layer 105 provided between the upper electrode 107 and the active layer 103 may be made of different materials.

A buffer layer provided between the anode and the active layer is sometimes called a charge transport layer (hole extraction layer, hole transport layer), and a buffer layer provided between the cathode and the active layer is an electron transport layer. It is sometimes called a layer (electron extraction layer). In the present embodiment, the active layer 103 contains a compound having at least one anionic substituent at the terminal, so that the photoelectric conversion element is high even without providing a charge transport layer between the anode and the active layer. performance can be demonstrated. Therefore, the charge transport layer may not be present, but of course the charge transport layer may be present.

There is no particular limitation on the material that constitutes the buffer layer. For example, for the hole extraction layer, any material that can improve the efficiency of hole extraction from the active layer to the anode can be used. Specific examples include inorganic compounds, organic compounds, or organic-inorganic perovskite compounds described in known documents such as WO 2013/171517, WO 2013/180230, and JP-A-2012-191194. For example, inorganic compounds include metal oxides such as copper oxide, nickel oxide, manganese oxide, iron oxide, molybdenum oxide, vanadium oxide, and tungsten oxide. Examples of organic compounds include conductive polymers obtained by doping polythiophene, polypyrrole, polyacetylene, triphenylenediamine or polyaniline with dopants, polythiophene derivatives having sulfonyl groups as substituents, conductive organic compounds such as arylamines, Nafion, or Lithium-doped spiro-OMeTAD is mentioned.

Similarly, for the electron extraction layer, any material that can improve the efficiency of electron extraction from the active layer to the cathode can be used. Specifically, the inorganic compounds, organic compounds, or organic-inorganic perovskite compounds according to the present invention are described in known documents such as WO 2013/171517, WO 2013/180230, or JP-A-2012-191194. are mentioned. For example, inorganic compounds include salts of alkali metals such as lithium, sodium, potassium, or cesium, and metal oxides such as zinc oxide, titanium oxide, aluminum oxide, or indium oxide. Examples of organic compounds include bathocuproine (BCP), bathophenanthrene (Bphen), (8-hydroxyquinolinato)aluminum (Alq3), boron compounds, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic anhydride (NTCDA), Examples include perylenetetracarboxylic anhydride (PTCDA), fullerene compounds, and phosphine compounds having a Group 16 element of the periodic table and a double bond, such as phosphine oxide compounds or phosphine sulfide compounds.

The thickness of the buffer layer is not particularly limited, but is preferably 0.5 nm or more, more preferably 1 nm or more, and more preferably 5 nm or more, while it is preferably 1 μm or less, further preferably 500 nm or less, and more preferably 200 nm. Below, it is particularly preferably 100 nm or less. When the film thickness of the buffer layer is within the above range, the carrier transfer efficiency can be easily improved, and the photoelectric conversion efficiency can be improved.

The method for forming the buffer layer is not limited, and the method can be selected according to the properties of the material. For example, the buffer layer can be formed by preparing a coating liquid containing a material and a solvent and using a wet film formation method such as a spin coating method or an inkjet method. In this case, as the solvent, the solvents mentioned in the description of the method for forming the active layer 103 can be used. The buffer layer can also be formed by a dry film-forming method such as a vacuum deposition method.

[4. Base material]
The photoelectric conversion element 100 usually has a base material 108 that serves as a support. However, the photoelectric conversion element 100 does not have to have the substrate 108 . The material of the base material 108 is not particularly limited as long as it does not significantly impair the effects of the present invention. can be used.

[5. Other layers]
The photoelectric conversion element 100 may have other layers. For example, the photoelectric conversion element 100 may have a work function tuning layer that adjusts the work function of the electrode between the lower electrode 101 and the buffer layer 102 or between the upper electrode 107 and the buffer layer 105. . In addition, the photoelectric conversion element 100 includes a thin insulator layer between the lower electrode 101 and the active layer 103 or between the upper electrode 107 and the active layer 103 to suppress moisture or the like from reaching the active layer 103. may have.

[6. Method for producing a photoelectric conversion element]
By forming each layer constituting the photoelectric conversion element 100 according to the method described above, the photoelectric conversion element 100 can be manufactured. There is no particular limitation on the method of forming each layer constituting the photoelectric conversion element 100, and the layers can be formed by a sheet-to-sheet (Manyo) method or a roll-to-roll method.

In addition, the roll-to-roll method is a method in which a flexible base material wound in a roll is unwound and processed while being transported intermittently or continuously until it is wound up by a winding roll. be. According to the roll-to-roll method, long substrates on the order of km can be collectively processed, so the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method. On the other hand, when each layer is formed by a roll-to-roll method, the film may be damaged or partially peeled off due to the contact between the film-forming surface and the roll due to its structure.

The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by a roll-to-roll manufacturing apparatus, but the upper limit of the outer diameter is preferably 5 m or less, more preferably 3 m or less, more preferably 3 m or less. 1 m or less. On the other hand, the lower limit is preferably 10 cm or more, more preferably 20 cm or more, and still more preferably 30 cm or more. The upper limit of the outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and even more preferably 0.5 m or less. On the other hand, the lower limit is preferably 1 cm or more, more preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, and particularly preferably 20 cm or more. It is preferable that these diameters are equal to or less than the above upper limit because the handleability of the roll is high. . The lower limit of the width of the roll is preferably 5 cm or more, more preferably 10 cm or more, and still more preferably 20 cm or more. On the other hand, the upper limit is preferably 5 m or less, more preferably 3 m or less, and more preferably 2 m or less. It is preferable that the width is equal to or less than the upper limit because the roll is easy to handle.

After laminating the upper electrode 107, the photoelectric conversion element 100 is preferably heated to 50° C. or higher, more preferably 80° C. or higher, and preferably 300° C. or lower, more preferably 280° C. or lower, and more preferably 250° C. or lower. Heating is preferred within the temperature range (this step may be referred to as an annealing treatment step). Performing the annealing process at a temperature of 50° C. or higher has the effect of improving the adhesion between the layers of the photoelectric conversion element 100, for example, the adhesion between the buffer layer 102 and the lower electrode 101, the buffer layer 102 active layer 103, and the like. is obtained, it is preferable. By improving the adhesion between each layer, the thermal stability, durability, etc. of the photoelectric conversion element can be improved. Setting the temperature of the annealing process to 300° C. or less is preferable because the possibility of thermal decomposition of the organic compound contained in the photoelectric conversion element 100 is reduced. In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time is preferably 1 minute or longer, more preferably 3 minutes or longer, and preferably 180 minutes or shorter, more preferably 60 minutes or shorter, in order to improve adhesion while suppressing thermal decomposition. The annealing process is preferably terminated when the open-circuit voltage, short-circuit current, and fill factor, which are parameters of solar cell performance, reach constant values. In order to prevent thermal oxidation of the constituent materials, the annealing process is preferably carried out under normal pressure and in an inert gas atmosphere. As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. Moreover, heating may be performed in a batch system or in a continuous system.

[7. Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element 100 can be obtained as follows. A solar simulator is used to irradiate the photoelectric conversion element 100 with light under AM1.5G conditions at an irradiation intensity of 100 mW/cm ² to measure current-voltage characteristics. From the resulting current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

The photoelectric conversion efficiency of the photoelectric conversion element 100 is not particularly limited, but is preferably 1% or higher, more preferably 1.5% or higher, and more preferably 2% or higher. On the other hand, there is no particular upper limit, and the higher the better. The fill factor of the photoelectric conversion element 100 is not particularly limited, but is preferably 0.6 or more, more preferably 0.7 or more, and still more preferably 0.8 or more. On the other hand, there is no particular upper limit, and the higher the better.

Moreover, in order to put a photoelectric conversion element into practical use, it is important to have high photoelectric conversion efficiency and high durability in addition to being easy to manufacture and inexpensive. From this point of view, the durability of the photoelectric conversion efficiency before and after the photoelectric conversion element 100 is exposed to the atmosphere for one week is preferably 60% or more, more preferably 80% or more, and the higher the better. The durability of the photoelectric conversion efficiency can be calculated as follows based on the photoelectric conversion efficiency before and after the photoelectric conversion element 100 is exposed to the atmosphere.
Durability (%) = ((photoelectric conversion efficiency after exposure to air for a predetermined time)/(photoelectric conversion efficiency immediately before exposure to air)) x 100

From a similar point of view, in a state where the active layer 103 of the photoelectric conversion element 100 is not sealed against the atmosphere or the sealing against the atmosphere is broken, the photoelectric conversion element 100 is placed in the atmosphere in a dark place for one week. Durability of photoelectric conversion efficiency before and after exposure is preferably 50% or higher, more preferably 80% or higher, still more preferably 90% or higher, and particularly preferably 95% or higher.

[8. solar cell]
The photoelectric conversion element 100 is preferably used as a solar cell element of a solar cell, especially a thin-film solar cell. FIG. 2 is a cross-sectional view schematically showing the configuration of a solar cell according to one embodiment of the present invention, and FIG. 2 shows an organic thin-film solar cell, which is the solar cell according to one embodiment of the present invention. . As shown in FIG. 2, the thin film solar cell 14 according to the present embodiment includes a weather resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a photoelectric conversion film. An element 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. The thin-film solar cell 14 according to this embodiment has the above-described photoelectric conversion element 100 as the photoelectric conversion element 6 . Light is irradiated from the side (lower side in FIG. 2) on which the weather-resistant protective film 1 is formed, and the photoelectric conversion element 6 generates electric power. It should be noted that the thin-film solar cell 14 does not need to have all of these constituent members, and necessary constituent members can be arbitrarily selected.

There are no particular restrictions on these constituent members that constitute the thin-film solar cell and the method of manufacturing the same, and well-known techniques can be used. For example, techniques described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194 can be used.

There are no restrictions on the application of the thin-film solar cell 14, and it can be used for any application. For example, the solar cell according to one embodiment includes solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railroads, solar cells for ships, solar cells for airplanes, solar cells for spacecraft, solar cells for home appliances, and so on. It can be used as a battery, a solar cell for mobile phones or a solar cell for toys.

The thin-film solar cell 14 may be used as it is, or may be used as a component of a solar cell module. For example, as shown in FIG. 3, a solar cell module 13 having a solar cell according to the present invention, particularly the thin-film solar cell 14 described above, on a substrate 12 is produced, and this solar cell module 13 is installed at a place of use. can be used A well-known technique can be used for the base material 12. For example, the material for the base material 12 is the material described in International Publication No. 2013/171517, International Publication No. 2013/180230, or Japanese Patent Application Laid-Open No. 2012-191194. can be used. For example, when a building board is used as the base material 12, a solar cell panel for the outer wall of a building can be produced as the solar cell module 13 by providing the thin-film solar cell 14 on the surface of this board.

The embodiments of the present invention are described below by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[Synthesis Example 1: Synthesis of 3F-BDP]

Li, G.; Lu, B.Z.; Hossain, A.; Roschangar, F.; Farina, V.; 2004, 6, 4129-4132.), 2,5-dichloro-1,4-phenylenediamine (1.77 g, 10 mmol), Park, K.; Bae, G.; Moon, J.; Choe, J.; Song, K.; H. Lee, S.; J. Org. Chem. 2010, 75, 6244-6251. Bis (3-fluorophenyl) acetylene (4.95 g, 23 mmol), palladium (II) acetate (229 mg, 0.10 mmol), tricyclohexylphosphine (570 mg, 0.20 mmol), potassium carbonate synthesized according to the method described in (6.98 g, 5.0 mmol) was reacted in N-methylpyrrolidone (100 mL) at 130° C. for 19 hours. Thereafter, N-methylpyrrolidone was removed under reduced pressure, and the residue was passed through a silica gel (developing solvent: ethyl acetate) short column and further treated with a silica gel column (developing solvent: hexane/dichloromethane = 1/1) to obtain a yellow solid. 3F-BDP was obtained (580 mg, 11%).

3F-BDP:
¹ H NMR (500 MHz, DMSO-d ₆ ) δ: 11.31 (s, 2H, NH), 7.51-7.49 (m, 2H, ArH), 7.42 (q, J = 7.3 Hz , 6H, ArH), 7.14-7.28 (m, 12H, ArH).
¹³ C NMR (125 MHz, DMSO-d ₆ ) δ: 163.46, 163.06, 161.52, 161.13, 138.07, 138.01, 134.68, 134.61, 133.95, 133 .73, 130.77, 130.70, 130.62, 126.78, 125.96, 124.21, 116.21, 116.05, 114.59, 114.46, 114.42, 114.29 , 113.10, 112.94, 111.71, 98.40.
¹⁹ F NMR (470 MHz, DMSO-d ₆ ) δ: -115.32, -115.69.
HRMS (APCI+) m/z Calcd. for _{C42H21F4N2 (} [M ₊ H] ^<+ >): _533.1641 ; Found: 533.1619.

[Synthesis Example 2: Synthesis of 3F-BDPSO-BNa (E1)]
Based on 3F-BDP obtained by the above method, 3F-BDPSO-BNa (E1) was synthesized by the following method.

A mixture of 3F-BDP (534 mg, 1.0 mmol) and sodium hydride (60% dispersion, 173 mg, 4.3 mmol) in tetrahydrofuran (20 mL) was stirred at room temperature for 3 hours to give 2,4-butanesulfonate. (435 mg, 3.2 mmol) was added and the reaction mixture was stirred at 75° C. for 13 hours. After allowing to cool to room temperature, methanol was added to deactivate unreacted sodium hydride. Solids were filtered and washed with tetrahydrofuran. The residue was ultrasonically washed in methanol to obtain compound 3F-BDPSO-BNa (E1) (600 mg, 70%) as a pale yellow solid.

3F-BDPSO-BNa (E1):
¹ H NMR (500 MHz, DMSO-d ₆ ) δ: 7.81 (s, 2H, ArH), 7.52 (q, J=7.4 Hz, 2H, ArH), 7.37 (q, J=7 .4Hz, 2H, ArH), 7.32-7.23 (m, 8H, ArH), 7.01-6.97 (m, 4H, ArH), 4.26-4.20 (m, 4H, NCH ₂ ), 2.24-2.22 (m, 2H, CH ₂ CH), 2.10-2.08 (m, 2H, CH ₂ CH), 1.50-1.47 (m, 2H, CH), 0.90 (d, J=6.9 Hz, 6H, _CH3 ).
¹³ C NMR (125 MHz, DMSO-d ₆ ) δ: 163.10, 162.90, 161.17, 160.96, 137.47, 137.41, 137.25, 134.01, 133.90, 130 .75, 130.68, 130.37, 130.29, 127.26, 125.52, 124.50, 117.72, 117.55, 115.56, 115.39, 112.52, 112.22 , 112.06, 98.30, 51.55, 41.65, 32.15, 15.47, 15.45.
¹⁹ F NMR (470 MHz, DMSO-d ₆ ) δ: -115.07, -115.94.
HRMS (ESI-) m/z Calcd. for _{C42H34F4N2NaO6S2 (} [M _{- Na} ] ^- ): _825.1692 ; Found: _825.1681 .

[Example 1]
(Preparation of active layer coating solution)
Lead (II) iodide (507.1 mg) and methylammonium iodide (CH ₃ NH ₃ I, 174.9 mg) were weighed into a vial in a molar ratio of 1:1, and N,N-dimethylformamide ( 1 mL) was added to prepare solution (A). Separately, N,N-dimethylformamide (1 mL) was added to 3F-BDPSO-BNa synthesized above (hereinafter referred to as BDPSO1-Na) to prepare solution (B).
Next, 200 μL of solution (B) was added dropwise to solution (A), and the resulting mixed solution was heated and stirred at 70° C. for 1 hour. The resulting solution was then filtered through a polytetrafluoroethylene (PTFE) filter (pore size 0.2 μm). Then, the obtained mixed solution was heated and stirred at 70° C. for 1 hour. Thereafter, the resulting solution was filtered through a polytetrafluoroethylene (PTFE) filter (pore size 0.2 μm) to prepare an active layer coating liquid. (Amount of BDPSO1-Na added: 0.03% by weight)

(Production of photoelectric conversion element)
A cleaning agent (precision glass substrate cleaning agent Semi-Clean M-LO, manufactured by Yokohama Yushi Kogyo Co., Ltd., 15 mL) was applied to a glass substrate (manufactured by Geomatec) provided with a patterned indium tin oxide (ITO) transparent conductive film. Ultrasonic cleaning, ultrasonic cleaning using ultrapure water, drying by nitrogen blow, and UV-ozone treatment were performed.

The active layer coating liquid (160 μL) prepared as described above was spin-coated onto the substrate at a speed of 4000 rpm, and after about 10 seconds, chlorobenzene (120 μL) was further spin-coated to change the solvent composition in the coating liquid film. As a result, crystals of perovskite composition were deposited. Further, by heating on a hot plate at 100° C. for 10 minutes to grow crystals, an active layer (perovskite crystal layer) having a thickness of about 350 nm was formed. The HOMO level of CH ₃ NH ₃ PbI ₃ contained in the active layer was separately measured to be (−5.40) eV, and the HOMO level of BDPSO1-Na was (−5.37) eV. .

Next, on the active layer, 30 nm of fullerene C60 (manufactured by Frontier Carbon) and then 15 nm of bathocuproine (BCP) (manufactured by Sigma-Aldrich) were formed by a resistance heating vacuum deposition method, forming an electron extraction layer. formed.
Next, a silver film having a thickness of about 100 nm was deposited on the electron extraction layer by a resistance heating vacuum deposition method using a patterning mask to form an electrode. A photoelectric conversion element was produced as described above.

[Example 2]
An active layer coating solution was prepared in the same manner as in Example 1 except that 68 μL of the solution (B) was dropped into the solution (A) (addition amount of BDPSO1-Na: 0.01% by weight). Then, a photoelectric conversion device was produced.

[Example 3]
An active layer coating solution was prepared in the same manner as in Example 1 except that 34 μL of the solution (B) was used (addition amount of BDPSO1-Na: 0.005% by weight). was made.

[Example 4]
An active layer coating solution was prepared in the same manner as in Example 1 except that 6.8 μL of the solution (B) was used (addition amount of BDPSO1-Na: 0.001% by weight). A conversion element was produced.

[Example 5]
An active layer coating solution was prepared in the same manner as in Example 1 except that 680 μL of the solution (B) was used (addition amount of BDPSO1-Na: 0.1% by weight). was made.

[Example 6]
An active layer coating solution was prepared in the same manner as in Example 1, except that a solution prepared by adding N,N-dimethylformamide (1 mL) to the benzodipyrrole compound BDPSO1-Na (1.3 mg) was used ( A photoelectric conversion device was produced in the same manner as in Example 1 except that the amount of BDPSO1-Na added was 0.2% by weight.

[Example 7]
An active layer coating solution was prepared in the same manner as in Example 1, except that a solution prepared by adding N,N-dimethylformamide (1 mL) to the benzodipyrrole compound BDPSO1-Na (2.0 mg) was used ( A photoelectric conversion device was produced in the same manner as in Example 1 except that the amount of BDPSO1-Na salt added: 0.3% by weight.

[Example 8]
An active layer coating solution was prepared in the same manner as in Example 1 except that BDPSO1-Cs in which Na was substituted with Cs was used instead of the benzodipyrrole compound BDPSO1-Na, and photoelectric conversion was performed in the same manner as in Example 1. A device was produced.

[Example 9]
An active layer coating solution was prepared in the same manner as in Example 1 except that BDPSO1-Rb in which Na was substituted with Rb was used instead of the benzodipyrrole compound BDPSO1-Na, and photoelectric conversion was performed in the same manner as in Example 1. A device was produced.

[Example 10]
An active layer coating solution was prepared in the same manner as in Example 1 except that the benzodipyrrole compound BDPSO1-H represented below was used instead of the benzodipyrrole compound BDPSO1-Na. A photoelectric conversion device was produced.

[Example 11]
An active layer coating solution was prepared in the same manner as in Example 1 except that the benzodipyrrole compound BDPSO1-MA represented below was used instead of the benzodipyrrole compound BDPSO1-Na. A photoelectric conversion element was produced by

[Example 12]
N,N to the benzodipyrrole compound BDPSO2-Na (1.0 mg) represented below
An active layer coating solution was prepared in the same manner as in Example 1 except that 680 μL of the solution to which dimethylformamide (1 mL) was added (addition amount of BDPSO2-Na: 0.1% by weight). A photoelectric conversion element was produced in the same manner.

[Example 13]
To the benzodipyrrole compound BDPSO3-Na (1.0 mg) represented below, N,N
An active layer coating solution was prepared in the same manner as in Example 1 (the amount of BDPSO3-Na added: 0.1% by weight), except that 680 μL of the solution to which dimethylformamide (1 mL) was added was used. A photoelectric conversion element was produced in the same manner.

[Example 14]
To the benzodipyrrole compound BDPSO4-Na (1.0 mg) represented below, N,N
An active layer coating solution was prepared in the same manner as in Example 1 except that 680 μL of the solution to which -dimethylformamide (1 mL) was added (addition amount of BDPSO4-Na: 0.1% by weight). A photoelectric conversion element was produced in the same manner.

[Example 15]
To the benzodipyrrole compound BDPSO5-Na (1.0 mg) represented below, N,N
An active layer coating solution was prepared in the same manner as in Example 1 except that 200 μL of the solution to which dimethylformamide (1 mL) was added (addition amount of BDPSO5-Na: 0.03% by weight). A photoelectric conversion element was produced in the same manner.

[Comparative Example 1]
A photoelectric conversion device was produced in the same manner as in Example 1, except that the solution (B) was not added dropwise to (A).

[Comparative Example 2]
Benzodipyrrole compound BDP1 (1.0 mg) having no anionic group represented below
An active layer coating solution was prepared in the same manner as in Example 1 except that 200 μL of a solution prepared by adding N,N-dimethylformamide (1 mL) was used (addition amount of BDP1: 0.03% by weight). A photoelectric conversion device was produced in the same manner as in Example 1.

[Comparative Example 3]
An active layer coating solution was prepared in the same manner as in Example 1, except that a solution prepared by adding N,N-dimethylformamide (1 mL) to the benzodipyrrole compound BDPSO1-Na (2.6 mg) was used ( A photoelectric conversion device was produced in the same manner as in Example 1 except that the amount of BDPSO1-Na added was 0.4% by weight.

[Evaluation of photoelectric conversion element]
A metal mask of 1 mm square was attached to the photoelectric conversion element obtained in each example and each comparative example, and the current-voltage characteristics between the ITO electrode and the silver electrode were measured. A source meter (2400 model, manufactured by Keithley) was used for the measurement, and a solar simulator with an air mass (AM) of 1.5 G and an irradiance of 100 mW/cm ² was used as the irradiation light source. From these measurement results, the open-circuit voltage Voc (V), the short-circuit current density Jsc (mA/cm ² ), the form factor FF, and the photoelectric conversion efficiency PCE (%) were calculated.
Here, the open-circuit voltage Voc is the voltage value when the current value is 0 (mA/cm ² ), and the short-circuit current density Jsc is the current density when the voltage value is 0 (V). The form factor FF is a factor representing internal resistance, and is expressed by the following equation, where Pmax is the maximum output.
FF = Pmax/(Voc x Jsc)
Also, the photoelectric conversion efficiency PCE is given by the following equation, where Pin is the incident energy.
PCE = (Pmax/Pin) x 100
= (Voc x Jsc x FF/Pin) x 100

[Measurement evaluation of HOMO level]
The HOMO level of the compound having an anionic substituent was determined by measuring the ionization energy using an ionization potential measuring device (PYS-201-J manufactured by Sumitomo Heavy Industries). The HOMO level of the perovskite (MAPbI ₃ ) used as the active layer was determined by the same method to be −5.40 eV. Table 1 summarizes the HOMO level values of the obtained compounds having an anionic substituent. Table 1 shows these values calculated based on the measurement results immediately after the photoelectric conversion element was produced.

[Evaluation of stability of photoelectric conversion element]
From Table 1, it is confirmed that the addition of a specific compound to the active layer improves the power generation characteristics PCE of the photoelectric conversion element compared to the case of no addition, particularly by improving the open-circuit voltage Voc and the short-circuit current Jsc. rice field. In addition, the addition amount of this compound contributes to the improvement of characteristics in the range of 0.3% by weight or less, and the HOMO level of this compound is ±0.3 eV or less compared to the HOMO level of the organic-inorganic hybrid type compound. It was also confirmed that there must be These are considered to be the effects of the added compound reducing energy attenuation (loss) in the transfer of charges generated from the active layer.

[Evaluation of stability of photoelectric conversion element]
In addition, the obtained photoelectric conversion element was sealed and continuously irradiated with simulated sunlight (air mass AM 1.5 G, irradiance 100 mW/cm ² ) at 30° C. to evaluate the stability of the photoelectric conversion element. For each photoelectric conversion element, Table 2 shows the PCE value after each time normalized so that the PCE value immediately after measurement is 1.00.

As shown in Table 2, the photoelectric conversion device according to Example 1 to which the compound having an anionic substituent containing the benzodipyrrole compound represented by formula (I) was added under continuous simulated sunlight irradiation had a It was found that the initial performance was maintained even after a long period of time, and the decrease in the photoelectric conversion efficiency PCE over time was extremely small. Thus, the addition of the compound having an anionic substituent containing the benzodipyrrole compound represented by the formula (I) suppresses deterioration over time of the photoelectric conversion element and provides a photoelectric conversion element having excellent durability. found to be useful for
Further, the photoelectric conversion element according to Example 1 obtained a higher photoelectric conversion efficiency than the photoelectric conversion element according to Comparative Example 1.

On the other hand, in the photoelectric conversion device according to Comparative Example 1, the photoelectric conversion efficiency PCE rapidly decreased with time. One possible reason for this is that the active layer has deteriorated. That is, the organic-inorganic hybrid semiconductor compound contains many defects on the crystal surface, and it is considered that the deterioration of the active layer is likely to proceed.

In contrast, the benzodipyrrole compound represented by formula (I) has an anionic substituent and deactivates defects on the crystal surface and crystal interface of the active layer containing the organic-inorganic hybrid semiconductor compound. , can act to protect against degradation of the active layer.

Reference Signs List 1 Weather resistant protective film 2 Ultraviolet cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealing material 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell 100 Photoelectric conversion element 101 Bottom Electrode 102 Buffer layer 103 Active layer 105 Buffer layer 107 Upper electrode 108 Base material

Claims (9)

A photoelectric conversion element having a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer containing an organic-inorganic hybrid semiconductor material positioned between the pair of electrodes,
The active layer contains a compound having at least one anionic substituent at its end in an amount of 0.3% by weight or less relative to the content of the organic-inorganic hybrid semiconductor material ,
A photoelectric conversion device , wherein the HOMO level of the compound having an anionic substituent is within a range of ±0.3 eV with respect to the HOMO level of the organic-inorganic hybrid semiconductor . 2. The photoelectric conversion device according to claim 1, wherein the organic-inorganic hybrid semiconductor material contains a compound having a perovskite structure. 3. The photoelectric conversion device according to claim 1, wherein the compound having an anionic substituent has a HOMO level in the range of -5.20 eV to -5.90 eV. 4. The photoelectric conversion device according to claim 1, wherein said anionic substituent is a sulfonic acid group. The photoelectric conversion device according to any one of claims 1 to 4 , wherein the compound having an anionic substituent includes a compound represented by formula (I) below.

(In formula (I), one of X ¹ and X ² is a nitrogen atom having a substituent R ² , the other is a carbon atom having a substituent Ar ³ , and R ¹ to R ⁴ are each independently represents a hydrogen atom or a monovalent organic group, and Ar ¹ to Ar ⁴ each independently represents an optionally substituted aromatic group.) 6. The photoelectric conversion device according to claim 5 , wherein at least one of R ¹ and R ² in formula (I) is an alkyl group having 1 to 20 carbon atoms having an anionic substituent as a substituent. 7. The photoelectric conversion device according to claim 5 , wherein at least one of Ar ¹ to Ar ⁴ in formula (I) is an aromatic group having a halogen atom as a substituent. 8. The photoelectric conversion device according to claim 5 , wherein at least one of Ar ¹ to Ar ⁴ in formula (I) is an aromatic group having a fluorine atom as a substituent. A solar cell module comprising the photoelectric conversion element according to claim 1 .

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