Photoelectric conversion element and photoelectric conversion device

Abstract

The present invention addresses the problem of providing a photoelectric conversion element using, as a hole transport material, a compound that exhibits good photoelectric conversion efficiency even when being dopant-free. In order to solve this problem, the present invention pertains to a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer that is disposed between the first electrode and the second electrode and that includes a perovskite structure crystal. The photoelectric conversion element has a hole transport layer including a compound represented by formula (1) between the photoelectric conversion layer and the first electrode.

Description

Photoelectric conversion element and photoelectric conversion device

[0001] The present invention relates to a photoelectric conversion element and a photoelectric conversion device.

[0002] In order to solve the problems of fossil energy depletion and the global environmental problems caused by the use of fossil energy, active research is being conducted on renewable and clean alternative energy sources such as solar energy, wind power, and hydropower. Among these, interest is growing in solar cells that directly convert sunlight into electrical energy. Here, a solar cell refers to a cell that generates current and voltage by absorbing light energy from sunlight and utilizing the photovoltaic effect, in which electrons and holes are generated.

[0003] Currently, n-p diode-type silicon (Si) single crystal-based solar cells with a light energy conversion efficiency of over 20% are widely known and are actually used for solar power generation. However, these require high-temperature processing steps and the materials themselves are expensive, resulting in high costs per unit of power. Furthermore, there are also supply issues due to the limited silicon resources.

[0004] On the other hand, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing and can be produced using a sheet-like substrate in a so-called roll-to-roll manner, which is expected to reduce costs. However, further improvements in power generation efficiency and durability are desired for the practical application of organic solar cells. In particular, perovskite solar cells having crystals with a perovskite structure as a photoelectric conversion layer have excellent photoelectric conversion properties, and therefore development is being advanced toward the practical application of solar cells. In perovskite solar cells, a hole transport material is often used in the element, and the purpose of using the hole transport material is to enhance the function of selectively transporting holes and thereby improve photoelectric conversion efficiency.

[0005] The spirobifluorene-based organic compound Spiro-OMeTAD is often used as a standard hole-transporting material. However, pure Spiro-OMeTAD exhibits relatively low hole mobility and conductivity. Therefore, additives, or dopants, such as lithium bis(trifluoromethane)sulfonimide (LiTFSI) and 4-tert-butylpyridine (TBP) are added to improve the electronic properties. However, LiTFSI and TBP have drawbacks: they are hygroscopic and volatile, which accelerate battery degradation, and they are prone to diffusion because they are not covalently bonded to the hole-transporting material. Therefore, they are unsuitable for device fabrication and increase costs.

[0006] Therefore, in recent years, development of hole transport materials to replace Spiro-OMeTAD has been progressing. For example, Patent Document 1 discloses a technology for obtaining a photoelectric conversion element that exhibits higher photoelectric conversion efficiency and durability than Spiro-OMeTAD by using a compound represented by the following formula (B-1) as a hole transport material.

[0007] Furthermore, Non-Patent Document 1 also reports an example in which a compound represented by the following formula (B-2) is used as a hole transport material, although for dye-sensitized solar cells.

[0008] International Publication No. 2022 / 153962

[0009] P. M. Lahti, et al, RSC Adv. ,2013,3,15626-15629

[0010] According to the studies of the present inventors, the photoelectric conversion element described in Patent Document 1 does not exhibit high electronic properties in the absence of a dopant, and the photoelectric conversion element described in Non-Patent Document 1 also has room for improvement in conversion efficiency. Therefore, an object of the present invention is to provide a photoelectric conversion element using, as a hole transport material, a compound that exhibits good photoelectric conversion efficiency even in the absence of a dopant. Another object of the present invention is to provide a photoelectric conversion device using, as a hole transport material, a compound that exhibits good photoelectric conversion efficiency even in the absence of a dopant.

[0011] The above object can be achieved by the present invention, which provides a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure and disposed between the first electrode and the second electrode, characterized in that the photoelectric conversion element further comprises a hole transport layer between the photoelectric conversion layer and the first electrode, the hole transport layer containing a compound represented by the following formula (1): (In formula (1), A is and B is and C is and D is and R in A to D. １ ~R ２０ each independently represents a hydrogen atom, a trimethylsilyl group, an optionally substituted linear or branched alkyl group of 1 to 20 carbon atoms, a optionally substituted linear or branched alkenyl group of 2 to 20 carbon atoms, a optionally substituted cycloalkyl group of 3 to 10 carbon atoms, a optionally substituted alkoxy group of 1 to 20 carbon atoms, a optionally substituted cycloalkoxy group of 3 to 10 carbon atoms, a optionally substituted alkylthio group or arylthio group of 1 to 18 carbon atoms, a optionally substituted (di)alkylamino group or (di)arylamino group of 1 to 20 carbon atoms, a substituted aromatic hydrocarbon group of 6 to 36 carbon atoms, or a optionally substituted heterocyclic group of 5 to 36 ring atoms. In addition, * in the formula represents the bonding position with formula (1). However, A and B are different, and C and D are different.)

[0012] According to the present invention, it is possible to provide a photoelectric conversion element that exhibits good photoelectric conversion efficiency even without a dopant.

[0013] Fig. 1 is a schematic cross-sectional view in the thickness direction of a first embodiment of a photoelectric conversion element of the present invention. Fig. 2 is a schematic cross-sectional view in the thickness direction of a second embodiment of a photoelectric conversion element of the present invention. Fig. 3 is a perspective view schematically showing an embodiment of a moving body including a photoelectric conversion element of the present invention. Fig. 4 is a perspective view schematically showing an embodiment of a building material including a photoelectric conversion element of the present invention.

[0014] The present invention provides a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure and disposed between the first electrode and the second electrode, wherein the photoelectric conversion element further has a hole transport layer between the photoelectric conversion layer and the first electrode, the hole transport layer containing a compound represented by the following formula (1): In formula (1), A is And B is and C is and D is and R in A to D. １ ~R ２０ each independently represents a hydrogen atom, a trimethylsilyl group, an optionally substituted linear or branched alkyl group of 1 to 20 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 20 carbon atoms, an optionally substituted cycloalkyl group of 3 to 10 carbon atoms, an optionally substituted alkoxy group of 1 to 20 carbon atoms, an optionally substituted cycloalkoxy group of 3 to 10 carbon atoms, an optionally substituted alkylthio group or arylthio group of 1 to 18 carbon atoms, an optionally substituted (di)alkylamino group or (di)arylamino group of 1 to 20 carbon atoms, an optionally substituted aromatic hydrocarbon group of 6 to 36 carbon atoms, or an optionally substituted heterocyclic group of 5 to 36 ring atoms. In the formula, * indicates the bonding position with formula (1). However, A and B are different, and C and D are different.

[0015] As a result of investigations, the present inventors have found that by including the hole transport layer, a photoelectric conversion element having excellent conversion efficiency can be obtained even without a dopant. Although the details of why the present invention can achieve a higher conversion efficiency than when a known compound is used are not clear, the following is thought to be the reason.

[0016] When a DAD (donor-acceptor-donor) type organic small molecule having a fluorenone structure in the acceptor portion is used as a hole transport material, it is presumed that high photoelectric conversion efficiency can be achieved even without dopants, from the viewpoints of increased carrier density, energy matching with the lower layer, and passivation with the perovskite structure crystal contained in the photoelectric conversion layer. Furthermore, an intermediate layer containing phthalocyanine particles may be provided between the photoelectric conversion layer and the hole transport layer containing the organic small molecule as a hole transport material. It is presumed that the DAD type organic small molecule having a fluorenone structure in the acceptor portion has excellent compatibility with the phthalocyanine particles, and that the improved adhesion of the film improves hysteresis.

[0017] According to the investigations of the present inventors, in the compound represented by the formula (B-1), which is a DAD-type organic small molecule having a fluorenone structure in the acceptor moiety, the nitrogen atom of the diphenylamine in the donor moiety is not adjacent to the acceptor moiety, and the HOMO distribution is biased toward the donor moiety. This is thought to result in low hole transport ability in the dopant-free state. Similarly, in the compound represented by the formula (B-2), which is a DAD-type organic small molecule having a fluorenone structure in the acceptor moiety, the donor moiety's substituents are all methoxy groups, and this has been found to leave room for further bias in electron density.

[0018] Therefore, in the present invention, by using a compound represented by the formula (1) in which A and B are different and C and D are different as a hole transport material, it is possible to improve photoelectric conversion efficiency. The inventors speculate that the HOMO is broadened and hole transport ability is improved when the nitrogen atom of diphenylamine in the donor moiety is adjacent to the acceptor moiety. In addition, the HOMO level of the entire molecule becomes shallower, improving donor properties. Furthermore, they speculate that introducing different substituents into two phenyl groups bonded to the same nitrogen atom strengthens the bias in electron density in the donor moiety and promotes an increase in carrier density in the entire molecule.

[0019] In the formula (1), it is preferable that A and B are different, C and D are different, A and C are the same, and B and D are the same, in order to spread the HOMO distribution evenly to the left and right and improve the carrier transport efficiency.

[0020] In the present invention, R in A to D １ ~R ２０ is expected to increase the carrier density due to the substituent having strong donor property, and therefore each of them is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent, or a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

[0021] In particular, since the electron density tends to be biased in the donor portion, when the compound is used as a hole transport material in a photoelectric conversion element, the photoelectric conversion efficiency is good. 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 is a hydrogen atom, and R ３ , R ８ , R １３ and R １８ It is more preferable that the following conditions are satisfied:

[0022] R ３ and R １３ is a hydrogen atom, R ８ and R １８is preferably a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

[0023] R ３ and R １３ is a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, R ８ and R １８ is preferably an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

[0024] R ３ and R １３ is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, R ８ and R １８ is preferably a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

[0025] R ３ and R １３ is an alkylthio group or arylthio group having 1 to 20 carbon atoms which may have a substituent, when R ８ and R １８ is preferably a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

[0026] In the formula (1), in order to further increase the photoelectric conversion efficiency, when the phenyl group in A does not contain a substituent, the phenyl group in B preferably contains a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

[0027] In the formula (1), from the viewpoint of further increasing the photoelectric conversion efficiency, when the phenyl group in A has a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, it is preferable that the phenyl group in B has an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

[0028] In the formula (1), in order to further increase the photoelectric conversion efficiency, when the phenyl group in A has a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, the phenyl group in B preferably has a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

[0029] In the formula (1), in order to further increase the photoelectric conversion efficiency, when the phenyl group in A has an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent, the phenyl group in B preferably has a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

[0030] The compound represented by the formula (1) as the hole transport material used in the hole transport layer of the photoelectric conversion element of the present invention will be specifically described below, but the present invention is not limited thereto.

[0031] R in A to D in the formula (1) １ ~R ２０ each independently represent a hydrogen atom, a trimethylsilyl group, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 10 carbon atoms which may have a substituent, an alkoxy group of 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent, an alkylthio group or arylthio group of 1 to 18 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group of 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group of 5 to 36 ring atoms which may have a substituent.

[0032] R １ ~R ２０ 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 the formula (1) 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.

[0033] R １ ~R ２０ 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 the formula (1) include a vinyl group, a 1-propenyl group, an allyl group, a 1-methylethenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 1-hexenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, and a 1-ethylethenyl group, as well as straight-chain or branched alkenyl groups having 2 to 20 carbon atoms in which a plurality of these alkenyl groups are bonded.

[0034] R １ ~R ２０ 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 the formula (1) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a 4-methylcyclohexyl group, and a 4-ethylcyclohexyl group.

[0035] R １ ~R ２０ Examples of the "alkoxy group having 1 to 20 carbon atoms" in the "alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (I) 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.

[0036] R １ ~R ２０ Examples of the "linear or branched 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 the following formula include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and a 4-methylcyclohexyloxy group.

[0037] R １ ~R ２０ Examples of the "alkylthio group or arylthio group having 1 to 18 carbon atoms" in the "alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent" represented by the formula (1) include a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, and a biphenylthio group.

[0038] R １ ~R ２０ Examples of the "(di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms" in the "(di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (1) include an ethylamino group and a phenylamino group as monosubstituted amino groups, and a diethylamino group and a diphenylamino group as disubstituted amino groups. In addition to the above amino groups, an acetylamino group and an acetylphenylamino group may also be selected.

[0039] R １ ~R ２０ 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 the formula (1) 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, and a triphenylenyl group. In the present invention, the aromatic hydrocarbon group includes a "condensed polycyclic aromatic group."

[0040] R １ ~R ２０ 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 the formula (1) include a pyridyl group, a pyrimidinyl group, a triazinyl group, a morpholino 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 naphthyridinyl 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, and a dibenzothienyl group.

[0041] R １ ~R ２０Examples of the "substituent" in the "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "alkoxy group having 1 to 20 carbon atoms which may have a substituent", "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent", "acyl group having 1 to 20 carbon atoms which may have a substituent", "alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent", "(di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent", "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent", or "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by the formula (I) above include a trimethylsilyl group; a methyl group, an ethyl group linear or branched alkyl groups having 1 to 18 carbon atoms such as n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, and decyl groups; ethenyl (vinyl group), 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 1-pentenyl, 1 linear or branched alkenyl groups having 2 to 18 carbon atoms, such as 2-hexenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, and 1-ethylethenyl; alkoxy groups having 1 to 18 carbon atoms, such as methoxy, ethoxy, propoxy, t-butoxy, pentyloxy, and hexyloxy; aromatic hydrocarbon groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, anthryl, phenanthryl, and pyrenyl;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, or a dibenzothienyl group; an amino group (—NH; ２ Examples of such substituents include mono-substituted amino groups such as ethylamino, acetylamino, and phenylamino, and di-substituted amino groups such as diethylamino, diphenylamino, and acetylphenylamino; and thiol groups such as -SH, methylthio, ethylthio, propylthio, phenylthio, and biphenylthio. A plurality of these "substituents" may be included, and when a plurality of such "substituents" are included, they may be the same or different. Furthermore, these "substituents" may further have the substituents exemplified above.

[0042] Furthermore, in the formula (1), it is preferable that A to D each have one of the following at one ortho- or para-position: a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

[0043] Specific examples of the compound represented by the formula (1) of the present invention are shown in Table 1, but the present invention is not limited to these. In Table 1, A to D represent A to D in the formula (1), and the substituent description item represents a substituent on the phenyl group. In Table 1, "no substituent" and "R １ ~R ２０ Among these, those not listed in the table are hydrogen atoms.

[0044]

[0045] In the present invention, it is more preferable that the compound represented by formula (1) is any one selected from the group consisting of compounds represented by the following formulas (A-8), (A-12), (A-14), (A-16), and (A-23).

[0046] The compound represented by formula (1) can be synthesized by a known method, for example, by a Buchwald-Hartwig cross-coupling reaction between 2,7-dibromofluorenone represented by formula (2) below and amine compounds represented by general formulas (3) and (4) below. R in formulas (3) and (4) １ ~R ２０ is R in the formula (1). １ ~R ２０ is the same as

[0047] Examples of methods for purifying the compound represented by formula (1) include purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., and purification by recrystallization or crystallization using a solvent. Alternatively, it is effective to use a compound with increased purity by using these methods in combination. Furthermore, these compounds can be identified by nuclear magnetic resonance analysis (NMR).

[0048] The present invention will be described in detail below with reference to preferred embodiments. The present invention is not limited to the following embodiments, and any modifications or improvements to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention are also included in the scope of the present invention.

[0049] In this specification, the term "layer" refers not only to a layer having a clear boundary or a flat thin-film layer, but also to a layer having a concentration gradient in which the contained elements gradually change, or a layer that can form a complex and intricate structure together with other layers. Elemental analysis of a layer can be performed, for example, by performing TOF-SIMS / FE-TEM / EDS line analysis measurement of a cross section of a photoelectric conversion element to confirm the element distribution of a specific element.

[0050] 1 is a cross-sectional view schematically illustrating the configuration of one embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element has a second electrode 3, an electron transport layer 4, a photoelectric conversion layer 5, a hole transport layer 6, and a first electrode 7 on a substrate 2. An intermediate layer 8 (not shown in the figure) may be formed between the photoelectric conversion layer 5 and the hole transport layer 6. One of the first electrode 7 and the second electrode 3 is an anode, and the other is a cathode. Current can be extracted by connecting the first electrode 7 and the second electrode 3 to an external circuit.

[0051] The photoelectric conversion layer 5 is excited by light incident through the substrate 2, the second electrode 3, and the electron transport layer 4, or through the first electrode 7, the hole transport layer 6, or through the first electrode 7, the hole transport layer 6, and an intermediate layer 8 (not shown in the figure), to generate electrons or holes. That is, the photoelectric conversion layer 5 generates a current between the first electrode 7 and the second electrode 3. The electron transport layer 4 is a layer disposed between the photoelectric conversion layer 5 and the two electrodes 3 and 7, and may not be formed in some cases. A structure in which multiple electron transport layers 4 and photoelectric conversion layers 5 are stacked may be used. This structure may also be called a tandem structure. Each component is described below. Alternatively, as shown in FIG. 2 , a photoelectric conversion element may be fabricated on the substrate 2 in the following order: the first electrode 7, the hole transport layer 6, the photoelectric conversion layer 5, the electron transport layer 4, and the second electrode 3. An intermediate layer 8 (not shown in the figure) may be formed between the hole transport layer 6 and the photoelectric conversion layer 5.

[0052] [Photoelectric Conversion Element] The photoelectric conversion element of the present invention is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a perovskite structure crystal disposed between the first electrode and the second electrode, characterized in that a hole transport layer containing the compound represented by formula (1) is disposed between the photoelectric conversion layer and the first electrode. Furthermore, in order to improve photoelectric conversion efficiency, the photoelectric conversion elements may be stacked in a tandem configuration. The photoelectric conversion elements to be stacked are not limited to a specific type of photoelectric conversion element, and may include perovskite solar cells that use a perovskite structure crystal in the photoelectric conversion layer, silicon solar cells, CIGS solar cells, and the like.

[0053] Methods for forming each layer including the photoelectric conversion layer of the photoelectric conversion element of the present invention include coating methods and vapor deposition methods. Examples of coating methods include dip coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, die coating, blade coating, curtain coating, and wire bar coating. The coating method involves preparing a coating solution for each layer described below, applying the solution in the desired layer order, and drying the solution. A desired method can be selected from these film formation methods depending on each layer.

[0054] The substrate and each layer will be described below. [Substrate] The photoelectric conversion element 1 of the present invention may include a substrate 2, for example, a transparent glass substrate such as soda lime glass or alkali-free glass, a ceramic substrate, or a transparent plastic substrate. When light is taken in from the first electrode 7 side, an opaque material can be used for the substrate 2, and when light is taken in from the second electrode 3 side, the substrate 2 is made of a transparent material.

[0055] [Electrodes] There are no particular limitations on the materials for the first electrode 7 and the second electrode 3, and conventionally known materials can be used. For example, metals such as gold, silver, titanium, and copper, sodium, sodium-potassium alloy, lithium, magnesium, carbon, carbon nanotubes, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, and Al / Al ２ O ３ Examples of suitable materials include Al / LiF mixtures and Al / LiF mixtures.

[0056] Transparent electrode materials include, for example, CuI, ITO (indium tin oxide), and SnO ２ Examples of the conductive transparent material include AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), FTO (fluorine-doped tin oxide), and ATO (antimony-doped tin oxide), as well as conductive transparent polymers. These materials may be used alone or in combination of two or more.

[0057] At least one of the first electrode 7 and the second electrode 3 on the light incident side is a transparent electrode, and the other may be a transparent electrode or may double as a reflective layer made of a light-reflective material, or may be a transparent electrode with a reflective layer on the side opposite to the light incident side. When the first electrode 7 is on the light incident side, the second electrode 3 may be a transparent electrode and the substrate 2 may be a reflective layer. The transparent electrode may be a patterned electrode.

[0058] [Photoelectric Conversion Layer] The photoelectric conversion element of the present invention has a photoelectric conversion layer that is disposed between a first electrode and a second electrode and contains a crystal having a perovskite structure. The photoelectric conversion layer 5 has a crystal having a perovskite structure. The crystal having a perovskite structure used in the present invention is preferably represented by the following general formula [5]: ABX ３ [5]

[0059] In the general formula [5], A is a monovalent cation of an organic molecule or a metal atom, B is a divalent metal cation, and X is a monovalent halide anion. For example, in the case of an organic molecule, A in the general formula [5] is preferably represented by CpNqHr (p, q, and r are all positive integers). Specific examples include methylammonium and formamidium. Furthermore, the metal atom is not particularly limited, but lithium, cesium, sodium, potassium, and rubidium are preferred. These organic molecules or metal atoms may be used alone or in combination of two or more.

[0060] If the constituent cation A is too large to fit within a crystal with a three-dimensional perovskite structure, the resulting crystal will be a two-dimensional perovskite structure, a 2.5-dimensional perovskite structure crystal having both two-dimensional and three-dimensional properties, a bilayer crystal of a three-dimensional and two-dimensional perovskite structure, or a crystal with a mixed three-dimensional and two-dimensional perovskite structure, all of which function as a photoelectric conversion layer. A bilayer crystal of a three-dimensional and two-dimensional perovskite structure refers to a crystal in which crystals with a three-dimensional and two-dimensional perovskite structure are stacked as independent, separate layers, while a mixed three-dimensional and two-dimensional perovskite refers to a crystal with a structure in which regions or domains of both two-dimensional or 2.5-dimensional layered and three-dimensional perovskite structure crystals are mixed.

[0061] The crystal of the two-dimensional perovskite or 2.5-dimensional perovskite structure is preferably represented by the following general formulas [6] to [8]: R' (n is a positive integer). ２ A ｎ－１ B ｎ X ３ｎ＋１ [6] R''A ｎ－１ B ｎ X ３ｎ＋１ [7] R'''A ｎ B ｎ X ３ｎ＋１ [8]

[0062] The general formulas [6] and [8] form an RP (Ruddlesden-Popper) type perovskite structure, a DJ (Dion-Jacobson) type perovskite structure, and an ACI (Alternating cations in the interlayer) type perovskite structure, respectively.

[0063] R', R'', and R''' in the above general formulas [6] to [8] are organic molecules or metal cations which may have a substituent, and specific examples thereof include ethylammonium, propylammonium, n-butylammonium, n-hexylammonium, n-octylammonium, 1,6-hexadiammonium, isobutylammonium, 3-(nonafluoro-tert-butyloxy)propylamine, 1,3-propanediammonium, 1,5-pentamethylenediamine, octyldiammonium, 2,2-(ethylenedioxy)bis(ethylammonium), 5-aminovaleric acid, 4-tert-butylammonium, N,N'-dimethylethylene-1,2-diammonium, 2,2,3,3,3-pentafluoropropylammonium, guanidium, propylammonium, propargylamine, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, 4-tert-butylammonium, N,N'-dimethylethylene-1,2-diammonium, 2,2,3,3,3-pentafluoropropylammonium, guanidium, propylammonium, propargylamine, alkylammonium ... Cylammonium, 4-fluorophenethylammonium, 4-fluorophenethylammonium, trifluoromethylbenzylammonium, pentafluorobenzylammonium, pentafluorophenylethylammonium, 4-methoxyphenethylammonium, imidazolium, pyridinium, 3-thiophenemethylammonium, 2-thiopheneethylammonium, 2-thiopheneformamidium, 2-thiophenemethylammonium, 1-naphthylmethylammonium, 2-naphthylmethylammonium, phenethylammonium, phenylammonium, benzylammonium, 2,5-thiophenedimethylammonium, phenylpropylammonium, 1,4-phenylenedimethanamine, 3-phenyl-2-propene-1-ammonium, phenylbutylammonium, 4-tert-butyl - benzylammonium, 3- (aminomethyl) piperidinium, 4- (aminomethyl) piperidinium is preferred.

[0064] In the above general formulas [5] to [8], B is a metal atom, such as lead, tin, bismuth, zinc, titanium, antimony, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. Among these, lead, tin, and bismuth are preferred from the viewpoint of electron orbital overlap. These metal atoms may be used alone or in combination of two or more.

[0065] X in the above general formulas [5] to [8] is a halogen atom, such as chlorine, bromine, or iodine. These halogen atoms may be used alone or in combination of two or more. Among these, halogen atoms are preferred because the inclusion of halogen in the structure makes the perovskite structure crystal more soluble in organic solvents, enabling application to inexpensive printing methods, etc. Furthermore, iodine is more preferred because it narrows the energy band gap of the perovskite structure crystal.

[0066] Specifically, 3D perovskite, 2D perovskite, and mixed 3D / 2D perovskite are MAPbI ３ and FAPbCl ３ , FAPbI ３ , MAPbIxBr ３－ｘ , MAPbIxCl ３－ｘ , Cs ０．０５ (MA ０．１７ FA ０．８３ ) ０．９５ Pb(I ０．８３ Br ０．１７ ) ３ , {Cs ｘ１ (FA ｘ２ MA １－ｘ２ ) １－ｘ１} ｘ３ Pb(I ｘ４ Br １－ｘ４ ) ｘ５ , Cs ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４ , (FAPbI ３ ) ０．９５ (MAPbBr ３ ) ０．０５、(FAPbI ３ ) ０．８５ (MAPbBr ３ ) ０．１５ 、CsPbI ３ 、CsPbBr ３ 、Csx(MA) １－ｘ PbI ３ 、Csx(FA) １－ｘ PbI ３ 、MAx(FA) １－ｘ PbI ３ 、MA ０．１７ FA ０．８３ Pb(I ０．８３ Br ０．１７ ) ３ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、Cs ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、(PEA) ２ (MA) ２ Pb ３ I １０ 、(PTA) ２ (MA) ４ Pb ５ I １６ 、(PEA) ２ (MA) ４ Pb ５ I １６ 、(ThMA) ２ (MA) ２ Pb ３ I １０ 、(3BBA) ２ (MA) ２ Pb ３ I １０ 、(ThMA) ２ (FA) ４ Pb ５ I １６ 、(4FPEA) ２ (FA ０．３ MA ０．７ ) ４ Pb ５ I １６ 、(PDMA)FA２ Pb ３ I １０ 、(3AAMPY)(MA) ３ Pb ４ I １３ 、(PDMA)MA ５ Pb ６ I １９ 、(PDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ４ Pb ５ I １６ 、 (BA ０．９ PEA ０．１ ) ２ MA ４ Pb ５ I １６ 、 (BA ０．９ PEA ０．１ ) ２ MA ３ Pb ４ I １３ 、(4FFEA) ２ MA ３ Pb ４ I １３ 、(4FFEA) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ３ Pb ４ I １３ 、(TEA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ３ Pb ４ I １３ 、Cs.Br ３ 、CsSﾎI ３ 、FA ０．７５ MA ０．２５ Se０．９５ Ge ０．０５ I ３ , FAMASnGeI ３ , FASnBr ３ , FASnI ３ , M.A. ２ Sn ３ I ８ , MASnBr ３ , MASnGeI ３ , MASnI ３ is preferred.

[0067] Depending on the purpose, the A site, B site, or X site in the above general formulas [5] to [8] may be adjusted to be insufficient or excessive, and the combinations of x1 to x5 may be changed depending on the purpose. Combinations of x1 to x5 are, for example, as shown in Table 2. Particularly preferred ranges of the combinations of x1 to x5 are 0.03≦x1≦0.10, 0.80≦x2≦0.96, 0.95≦x3≦1.05, 0.80≦x4≦0.96, and 2.95≦x5≦3.05. MACl may also be included as a material for forming perovskite crystals.

[0068]

[0069] In the above specific examples, "MA" represents methylammonium, "FA" represents formamidinium, "PEA" represents phenethylammonium, "PTA" represents phenyltriethylammonium, "ThMA" represents 2-thiophenemethylammonium, "3BBA" represents 3-bromobenzylammonium, "3AMPY" represents 3-(aminomethyl)pyridine, "PDMA" represents 1,4-phenylenedimethaneammonium, "TTDMA" represents thieno[3,2-b]thiophene-2.5-diyldimethaneammonium, "4FPEA" represents 4-fluorophenethylammonium, "BA" represents butylammonium, and "TEA" represents 2-thiophenethylammonium.

[0070] The perovskite crystal preferably has a cubic structure in which a metal atom M is located at the body center, an organic molecule R is located at each vertex, and a halogen atom or chalcogen atom X is located at the face center. Although the details are not clear, it is presumed that the presence of such a structure allows the orientation of octahedra in the crystal lattice to be easily changed, thereby increasing the mobility of electrons in the perovskite crystal and improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0071] The perovskite crystal used in the present invention is preferably a crystalline semiconductor. A crystalline semiconductor refers to a semiconductor in which a scattering peak can be detected by measuring an X-ray scattering intensity distribution. When the perovskite crystal is a crystalline semiconductor, the mobility of electrons in the perovskite crystal increases, improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0072] The thickness of the photoelectric conversion layer according to the present invention is preferably 5 nm or more and 2000 nm or less. A thickness of 5 nm or more allows sufficient absorption of light, and a thickness of 2000 nm or less allows generated charges to be transported to each electrode. A more preferred lower limit is 50 nm, a more preferred upper limit is 1200 nm, an even more preferred lower limit is 100 nm, and an even more preferred upper limit is 1000 nm.

[0073] [Hole transport layer] The photoelectric conversion element of the present invention has a hole transport layer 6 between the photoelectric conversion layer and the first electrode 7. The hole transport layer 6 is a layer containing the compound represented by formula (1) as a hole transport material. The hole transport layer may contain two or more types of hole transport materials in combination, and may also contain other hole transport materials not belonging to the present invention in combination. In this case, it is preferable that the compound represented by formula (1) is contained in an amount of 50 wt % or more as the hole transport material.

[0074] Examples of other hole transport substances not belonging to the present invention include spirofluorene compounds, triphenylamine compounds, chrysene compounds, pyrene compounds, phthalocyanine compounds, carbazole compounds, fluorene compounds, phenylcyclohexane compounds, benzidine compounds, phenoxazine compounds, phenylenediamine compounds, thiocyanate compounds, and thiophene compounds.

[0075] [Electron Transport Layer] In the photoelectric conversion element of the present invention, an electron transport layer 4 may be disposed between the second electrode 3 and the photoelectric conversion layer 5, as shown in Fig. 1. The material of the electron transport layer 4 is not particularly limited, and examples thereof include N-type conductive polymers, N-type low-molecular-weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, and surfactants. Specific examples thereof include cyano group-containing polyphenylene vinylene, boron-containing polymers, bathocuproine, bathophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalene tetracarboxylic acid compounds, fullerene compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

[0076] The thickness of the electron transport layer 4 is preferably 1 nm or more at the lower limit and 2000 nm or more at the upper limit. A thickness of 1 nm or more sufficiently blocks holes, while a thickness of 2000 nm or less prevents electron transport and increases photoelectric conversion efficiency. The thickness is more preferably 3 nm or less at the lower limit and 1000 nm or less at the upper limit, and even more preferably 5 nm or less at the lower limit and 500 nm or less at the upper limit.

[0077] [Intermediate Layer] The photoelectric conversion element 1 may have one or more intermediate layers 8 for the purpose of reducing an energy gap that may hinder charge transfer or suppressing migration between layers. The intermediate layer 8 contains either an inorganic compound or an organic compound. Examples of inorganic compounds include Al compounds, Mo compounds, Ni compounds, Ti compounds, Sn compounds, and Zn compounds. In addition, as the organic compound, fullerene compound, phthalocyanine compound, spirofluorene compound, triphenylamine compound, chrysene compound, pyrene compound, phthalocyanine compound, carbazole compound, fluorene compound, phenylcyclohexane compound, benzidine compound, phenoxazine compound, phenylenediamine compound, thiocyanate compound, butyral resin, acrylic resin, polycarbonate resin, polyester resin, polyvinyl acetal resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, cellulose resin can be enumerated.Among them, phthalocyanine compound is preferred because of its compatibility with the compound represented by the general formula (1) of the present invention.

[0078] The thickness of the intermediate layer is preferably 5 nm or more and 800 nm or less. If the thickness is 5 nm or more, an effect of suppressing interlayer migration can be expected, and if the thickness is 800 nm or less, charge can be easily transported to each electrode. More preferably, it is 40 nm or more and 600 nm or less, and even more preferably, it is 40 nm or more and 400 nm or less. In addition, the intermediate layer can be expected to have the effect of reducing the energy gap that hinders charge transfer between layers.

[0079] <Application Examples> Application examples of the present invention relate to photoelectric conversion devices, mobile objects, and building materials. [Photoelectric Conversion Device] The photoelectric conversion device of the present invention has the photoelectric conversion element of the present invention. A photoelectric conversion device can be configured by using a plurality of photoelectric conversion elements of the present invention. When a plurality of photoelectric conversion elements are connected, such a photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. The photoelectric conversion element may be stacked with elements having different absorption wavelengths to increase the output voltage. Furthermore, the photoelectric conversion device has the photoelectric conversion element of the present invention and an inverter. The inverter may be a converter that converts direct current to alternating current.

[0080] The photoelectric conversion device may have a power storage unit connected to the photoelectric conversion element. The power storage unit is not limited as long as it can store electricity. Examples include a lithium-ion secondary battery, an all-solid-state battery, and an electric double layer capacitor. In order to provide a function such as maintaining or increasing the amount of incident light, a surface layer that is resistant to water and dirt, or a function to collect or guide light may be added.

[0081] [Mobile Object] A mobile object of the present invention has the photoelectric conversion element of the present invention. FIG. 3 is a perspective view schematically showing one embodiment of a mobile object equipped with the photoelectric conversion element of the present invention. The mobile object 30 has a photoelectric conversion element 31 and a body 32 equipped with the photoelectric conversion element 31. The photoelectric conversion element of the present invention can be applied to the photoelectric conversion element 31. The photoelectric conversion element 31 is disposed in a position on the body 32 where it can receive external light. If the mobile object 30 is an automobile, the photoelectric conversion element 31 may be disposed on the roof. The electrical energy obtained by the photoelectric conversion element 31 may power the mobile object 30 or may power other electrical equipment. Electrical energy generated from the power of the mobile object 30 may be used to power the photoelectric conversion element 31. If the mobile object 30 is an automobile, frictional energy generated by braking may be converted into electrical energy and used to control the photoelectric conversion element 31.

[0082] The mobile object 30 may be, for example, an automobile, a motorcycle, a railroad vehicle, a ship, an artificial satellite, an airplane, or a flying object including a drone. The configuration of the body 32 of the mobile object 30 is not particularly limited, but it is preferably made of a high-strength material.

[0083] [Building Material] The building material of the present invention has the photoelectric conversion element of the present invention. FIG. 4 is a perspective view schematically showing one embodiment of a building material including the photoelectric conversion element of the present invention. The building material 40 may be the roof of a building. The building material 40 of this embodiment has a photoelectric conversion element 41, a protective member 42 that protects the photoelectric conversion element 41, a heat dissipation member 43, and exterior coverings 44a and 44b. The photoelectric conversion element of the present invention can be applied to the photoelectric conversion element 41.

[0084] The building material 40 of the present invention may have a heat dissipation member 43 having a higher thermal conductivity than the photoelectric conversion element 41. When used on a roof or the like, sunlight may increase the temperature of the photoelectric conversion element 41, potentially reducing the photoelectric conversion efficiency. The use of the heat dissipation member 43 can reduce the reduction in photoelectric conversion efficiency. Examples of the heat dissipation member 43 include a metal, an alloy, a liquid metal, and a liquid resin.

[0085] The building material 40 of the present invention may also have exterior coatings 44a and 44b. The exterior coatings 44a and 44b may emit different colors or may be the same. 44a and 44b may be made of the same material or different materials. Paint or a transparent substrate may be used as the exterior coating. A material with low light absorption and high heat insulation properties is preferred.

[0086] In addition to the above application examples, other examples include the following: Portable devices such as calculators, sensors, and small solar panels; Wearable devices such as eyeglasses, wristwatches, and portable medical equipment; Sheet structures supported by multiple frames such as tents, greenhouses, and truck beds; Fixed structures such as road panels, floating panels, building materials that take advantage of the flexibility of the substrate, wall-mounted building materials, glass-mounted building materials, and mega solar panels.

[0087] [Method for manufacturing photoelectric conversion element] The method for manufacturing the photoelectric conversion element of the present invention includes the steps of forming a first electrode, forming a second electrode, and forming a photoelectric conversion layer containing crystals with a perovskite structure between the first electrode and the second electrode. Each step of the manufacturing method will be described below.

[0088] [Step of Forming a First Electrode and Step of Forming a Second Electrode] The method for manufacturing a photoelectric conversion element of the present invention includes a step of forming a first electrode and a step of forming a second electrode. For the step of forming the first electrode and the step of forming the second electrode, appropriate methods can be selected depending on the materials of the first electrode and the second electrode, respectively. Examples of such methods include, but are not limited to, sputtering, vacuum deposition, CVD (chemical vapor deposition), and SPD (spray pyrolysis deposition). The materials for the first electrode and the second electrode are as described above. When either or both of the first electrode and the second electrode are transparent electrodes, the thickness of the transparent electrode is preferably 0.03 μm or more and 3 μm or less. When manufacturing a solar cell, cutting may be performed between each step to form a circuit. Examples of cutting include mechanical patterning and laser patterning.

[0089] [Modularization Process] The elements having electrodes formed thereon may be sealed. Examples of sealing methods include sealing with a resin or sealing with a film. Examples of materials used for sealing include silazane, silicone rubber, resins having a siloxane skeleton, and glass. In addition, from the viewpoint of suppressing adhesion between elements that occurs when winding in a roll-to-roll manner, the surfaces of the sealed elements may be subjected to a hairline treatment.

[0090] [Step of forming photoelectric conversion layer] The step of forming the photoelectric conversion layer may include a step of applying a liquid containing the material for the photoelectric conversion layer described above. Examples of application methods include spin coating, blade coating, slit die coating, screen printing, bar coating, casting, print transfer, immersion and lifting, inkjet printing, spraying, and vacuum deposition. Among these, an appropriate method is selected depending on the properties of the photoelectric conversion layer to be produced, such as thickness control and orientation control.

[0091] In order to remove the solvent or dispersion medium from the liquid containing the material of the applied photoelectric conversion layer, annealing may be performed under reduced pressure or in an inert atmosphere (nitrogen or argon atmosphere). The temperature of the annealing is preferably 40° C. or higher and 300° C. or lower, more preferably 50° C. or higher and 150° C. or lower. Note that annealing is preferable because it may increase the contact area at the interface between the stacked layers due to the penetration of the materials constituting each layer into each other, thereby increasing the short-circuit current.

[0092] [Step of Forming an Intermediate Layer] The method for producing the photoelectric conversion element of the present invention may include a step of forming an intermediate layer between the photoelectric conversion layer and the first electrode. Examples of the step of forming the intermediate layer include the following: a method in which charge transport particles are disposed on the surface of the photoelectric conversion layer, and then a resin solution in which an insulating resin is dissolved is applied and dried; a method in which a resin solution in which an insulating resin is dissolved is applied on the surface of the photoelectric conversion layer, and then charge transport particles are disposed, and then the resin solution is dried; or a method in which a solution in which charge transport particles are dispersed in a resin solution in which an insulating resin is dissolved is applied on the surface of the photoelectric conversion layer and then dried.

[0093] The present invention will be specifically described below by way of examples with reference to the drawings, but the present invention is not limited to the following examples. １ This was measured by H-NMR (apparatus: AVANCE3-500, manufactured by BRUKER).

[0094] Synthesis Example 1 Synthesis of Compound (A-8) 2,7-Dibromofluorenone (1.69 g, manufactured by Tokyo Chemical Industry Co., Ltd.), 4-methoxy-4'-methyldiphenylamine (2.16 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and toluene (100 mL) were placed in a reaction vessel and degassed for 30 minutes. Xphos (0.21 g, manufactured by Sigma-Aldrich), tris(dibenzylideneacetone)dipalladium(0) (0.28 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and sodium t-butoxide (1.40 g, manufactured by Tokyo Chemical Industry Co., Ltd.) were then placed in a nitrogen atmosphere and stirred under reflux for 24 hours. After completion of the reaction, the mixture was filtered with ethyl acetate using activated clay. The filtrate was concentrated, and the crude product was purified by silica gel column chromatography (hexane:ethyl acetate = 7:1) to obtain the compound represented by the following formula (A-8) as a black-purple powder (yield: 1.79 g, 59%). The compound represented by the following formula (A-8) obtained １ The results of identification by H-NMR measurement are shown below. １ H-NMR (500MHz, CDCl ３ ): δ (ppm) = 7.14 (2H), 7.08 (2H), 6.98 (4H), 6.96 (4H), 6.93 (2H), 6.88 (8H), 6.76 (8H), 3.73 (6H), 2.24 (6H).

[0095] Synthesis Example 2: Synthesis of Compound (B-1) Used in Comparative Example 2,7-Dibromofluorenone (1.69 g, manufactured by Tokyo Chemical Industry Co., Ltd.), bis-(4-methoxyphenyl)-[4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-amine (3.34 g, manufactured by Tokyo Chemical Industry Co., Ltd.), toluene (28 mL), ethanol (9.5 mL), and water (9.0 mL) were added to a reaction vessel and degassed for 30 minutes. Tetrakis(triphenylphosphine)palladium(0) (0.24 g, manufactured by Tokyo Chemical Industry Co., Ltd.) and potassium carbonate (1.83 g, manufactured by Nippon Soda Co., Ltd.) were added, and the mixture was stirred at 100°C for 24 hours under a nitrogen atmosphere. After completion of the reaction, the mixture was extracted with ethyl acetate, washed with saturated aqueous sodium chloride solution, and then dried over sodium sulfate. After concentration, the crude product was purified by silica gel column chromatography (hexane:ethyl acetate=7:1) to obtain a compound represented by the following formula (B-1) as a black purple powder (yield: 1.97 g, 50%). １ The results of identification by H-NMR measurement are shown below. １ H-NMR (500MHz, CDCl ３ ): δ (ppm) = 7.79 (2H), 7.60 (2H), 7.45 (2H), 7.37 (4H), 7.03 (8H), 6.91 (4H), 6.79 (8H), 3.74 (12H).

[0096] Synthesis Example 3: Synthesis of Compound (B-2) Used in Comparative Example. 2,7-Dibromofluorenone (1.70 g, manufactured by Tokyo Chemical Industry Co., Ltd.), 4,4'-dimethoxydiphenylamine (2.35 g, manufactured by Nard Laboratory Co., Ltd.), and toluene (100 mL) were added to a reaction vessel and degassed for 30 minutes. 1,1'-Bis(diphenylphosphino)ferrocene (0.17 g, manufactured by Sigma-Aldrich Co., Ltd.), palladium(0) acetate (0.048 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and cesium carbonate (4.90 g, manufactured by Tokyo Chemical Industry Co., Ltd.) were added and stirred under reflux for 24 hours under a nitrogen atmosphere. After completion of the reaction, the mixture was filtered with ethyl acetate using activated clay. The filtrate was concentrated, and the crude product was purified by silica gel column chromatography (hexane:ethyl acetate = 4:1) to obtain the compound represented by the following formula (B-2) as a black-purple powder (yield: 1.44 g, 45%). The compound represented by the following formula (B-2) obtained １ The results of identification by H-NMR measurement are shown below. １ H-NMR (500MHz, CDCl ３ ): δ (ppm) = 7.17 (2H), 7.13 (2H), 7.02 (8H), 6.94 (2H), 6.83 (8H), 3.80 (12H).

[0097] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples without departing from the gist of the present invention. In the following description of the examples, "parts" are by mass unless otherwise specified.

[0098] <Preparation of Particles 1> Step (1) Under a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were added to a reaction vessel, which was then heated to 30°C and maintained at that temperature. Next, 3.75 parts of gallium trichloride was added at this temperature (30°C). The water concentration of the mixed solution at the time of addition was 150 ppm. The temperature was then increased to 200°C. Next, under a nitrogen flow atmosphere, the mixture was reacted at 200°C for 4.5 hours, cooled, and when the temperature reached 150°C, the product was filtered. The resulting filtrate was dispersed and washed using N,N-dimethylformamide at 140°C for 2 hours, followed by filtration. The resulting filtrate was washed with methanol and dried to obtain chlorogallium phthalocyanine particles in a yield of 71%.

[0099] Step (2) 4.65 parts of the chlorogallium phthalocyanine particles were dissolved in 139.5 parts of concentrated sulfuric acid at a temperature of 10°C, and the solution was dropped into 620 parts of ice water under stirring to reprecipitate, followed by vacuum filtration using a filter press. No. 5C (manufactured by Advantec Co., Ltd.) was used as the filter. The obtained wet cake (filtrate) was dispersed and washed with 2% aqueous ammonia for 30 minutes, and then filtered using a filter press. Next, the obtained wet cake (filtrate) was dispersed and washed with ion-exchanged water, and then filtered three times using a filter press. Finally, freeze-drying was performed to obtain hydroxygallium phthalocyanine particles (hydrated hydroxygallium phthalocyanine particles) with a solids content of 23% by mass in a yield of 71%. The hydroxygallium phthalocyanine particles were dried in a Hyper Dry dryer (product name: HD-06R, frequency (oscillation frequency): 2455 MHz±15 MHz, manufactured by Nippon Biocon) to obtain hydroxygallium phthalocyanine particles (crystals) with a water content of 1.0 mass % or less.

[0100] Step (3) Five parts of the hydroxygallium phthalocyanine particles were dispersed for six hours using a sand mill (TSG-1 / 4G-4U, manufactured by Igarashi Machinery Mfg. Co., Ltd. (now Imex Co., Ltd.), disk diameter 70 mm, number of disks 5) containing five parts of N-methylformamide solvent and five parts of glass beads enclosed therein, followed by filtration and drying to obtain particles 1.

[0101] <Preparation of Resin Solution 1> Resin solution 1 was obtained by dissolving 1.0 g of polyvinyl butyral (product name: BM-2, manufactured by Sekisui Chemical Co., Ltd.) in 19 g of 2-propanol with stirring for 24 hours.

[0102] Example 1 Formation of Electron Transport Layer A glass substrate with an ITO film was cleaned, and tin oxide (2) adjusted to 3% by mass was applied thereon by spin coating, followed by heating at 150°C for 30 minutes to form a thin-film electron transport layer having a thickness of 15 nm.

[0103] [Formation of Photoelectric Conversion Layer] 0.41 g of formamidinium iodide, 1.2 g of lead iodide, 0.05 g of methylammonium bromide, and 0.17 g of lead bromide were dissolved in 1.67 g of N,N-dimethylformamide and 0.49 g of dimethyl sulfoxide, and the solution was stirred at 70°C for 24 hours. Then, a cesium iodide solution prepared by dissolving 0.035 g of cesium iodide in 0.1 g of dimethyl sulfoxide was added to prepare a photoelectric conversion layer coating solution. This coating solution was spin-coated on the electron transport layer to form a Cs ５ (MA ０．１７ FA ０．８３ ) ９５ Pb(I ０．８３ Br ０．１７ ) ３ A photoelectric conversion layer having a thickness of 500 nm was formed.

[0104] [Introduction of Hole Transport Layer] A hole transport material solution was prepared by dissolving 0.075 g of compound (A-8), which is the hole transport material obtained in Synthesis Example 1, in 1.1 g of chlorobenzene. This solution was applied to the photoelectric conversion layer by spin coating to form a hole transport layer with a thickness of 300 nm.

[0105] [Formation of First Electrode] A first electrode having a thickness of 80 nm and an area of ​​0.09 cm was formed on the hole transport layer. ２ A gold electrode was formed by vacuum deposition to form a first electrode, thereby obtaining a photoelectric conversion element.

[0106] [Film Thickness Analysis] The film thickness was confirmed by cutting the photoelectric conversion element, fixing it on an inclined sample stage, and then using a cross-sectional SEM (apparatus: Carl Zeiss, Smart SEM).

[0107] Example 2 A photoelectric conversion element is obtained in the same manner as in Example 1, except that the compound (A-12) is used in the hole transport layer.

[0108] Example 3 A photoelectric conversion element is obtained in the same manner as in Example 1, except that the compound (A-14) is used in the hole transport layer.

[0109] Example 4 A photoelectric conversion element is obtained in the same manner as in Example 1, except that the compound (A-16) is used in the hole transport layer.

[0110] Example 5 A photoelectric conversion element is obtained in the same manner as in Example 1, except that the compound (A-23) is used in the hole transport layer.

[0111] Example 6 A photoelectric conversion element was obtained in the same manner as in Example 1, except that an intermediate layer described below was provided between the photoelectric conversion layer and the hole transport layer. [Formation of Intermediate Layer] 0.1 g of the particles 1, 0.01 g of a calixarene compound (JP 2003-207913 A), 10.6 g of 2-propanol, and 11 g of zirconia beads were encapsulated and dispersed in a paint shaker (manufactured by Toyo Seiki Seisaku-sho) for 6 hours. Then, 0.2 g of resin solution 1 was added, and dispersion was again carried out in a paint shaker for 6 hours to prepare a charge transport solution. The charge transport solution was spin-coated onto the photoelectric conversion layer to form an intermediate layer with a thickness of 150 nm.

[0112] [Analysis of Compound Amount] The electrode surface of the photoelectric conversion element was peeled off to expose the intermediate layer surface. This intermediate layer surface was wiped with a cotton swab soaked in a solvent, dissolved in heavy water sulfuric acid, and subjected to 1H-NMR measurement (apparatus: AVANCE3-500, manufactured by BRUKER). In addition, the peeled component was subjected to mass and structural analysis using GPC, MALDI-TOF-MS, IR, and gas chromatography to confirm the presence of the compound.

[0113] Comparative Example 1 A photoelectric conversion element was obtained in the same manner as in Example 1, except that the compound (B-1) obtained in Synthesis Example 2 was used for the hole transport layer.

[0114] Comparative Example 2 A photoelectric conversion element was obtained in the same manner as in Example 1, except that the compound (B-2) obtained in Synthesis Example 3 was used for the hole transport layer.

[0115] [Evaluation] The photoelectric conversion elements obtained in each of the examples and comparative examples were evaluated as follows: (Evaluation of power generation efficiency) A power source (manufactured by Keithley, Model 236) was connected between the electrodes of the photoelectric conversion element, and a power source having an intensity of 100 mW / cm ２ The photoelectric conversion efficiency was evaluated by irradiating the device with a constant amount of light using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) and measuring the generated current and voltage (hysteresis evaluation).

[0116] The photoelectric conversion efficiency (PCE) obtained by the above measurement is evaluated for each voltage application direction. ｆｏｒ． and PCE ｒｅｖ． The hysteresis index (HI) was calculated using the following formula (9): The smaller the HI, the smaller the hysteresis. The results are shown in Table 3.

[0117]

[0118] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0119] This application claims priority based on Japanese Patent Application No. 2023-216293 filed on December 21, 2023, and Japanese Patent Application No. 2024-086008 filed on May 28, 2024, the entire contents of which are incorporated herein by reference.

[0120] REFERENCE SIGNS LIST 1 Photoelectric conversion element 2 Substrate 3 Second electrode 4 Electron transport layer 5 Photoelectric conversion layer 6 Hole transport layer 7 First electrode

Claims

1. A photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure disposed between the first electrode and the second electrode, the photoelectric conversion element having a hole transport layer between the photoelectric conversion layer and the first electrode, the hole transport layer containing a compound represented by the following formula (1): (In formula (1), A is And B is And C is And D is R in A to D １ ~R ２０ each independently represents a hydrogen 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 cycloalkyl group having 3 to 10 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, an alkylthio group or an arylthio group having 1 to 18 carbon atoms which may have a substituent, a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms which has a substituent, or a heterocyclic group having 5 to 36 ring atoms which may have a substituent. In addition, * in the formula represents the bonding position with formula (1). However, A and B are different, and C and D are different.) 2. The photoelectric conversion element according to claim 1, wherein the hole transport layer contains a compound in which, in formula (1), A is different from B, C is different from D, A is the same as C, and B is the same as D.

3. In A to D of the above formula (1), R １ ~R ２０ wherein each of the groups independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or an arylthio group having 1 to 18 carbon atoms which may have a substituent in the hole transport layer.

4. The photoelectric conversion element according to any one of claims 1 to 3, wherein in the hole transport layer, a compound in which A to D in formula (1) have one of the following at an ortho position or para position: a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent.

5. In the formula (1), when the phenyl group in A does not contain a substituent, the phenyl group in B has a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent; when the phenyl group in A has a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, the phenyl group in B has an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a (di)alkylamino group or (di)arylamino group having 1 to 20 carbon atoms which may have a substituent, or an alkylthio group or arylthio group having 1 to 18 carbon atoms which may have a substituent; The photoelectric conversion element according to any one of claims 1 to 4, wherein when the phenyl group in A has a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, the phenyl group in B has a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent; and when the phenyl group in A has an alkylthio group or an arylthio group having 1 to 18 carbon atoms which may have a substituent, the phenyl group in B has a (di)alkylamino group or a (di)arylamino group having 1 to 20 carbon atoms which may have a substituent.

6. The photoelectric conversion element according to any one of claims 1 to 5, wherein the compound represented by formula (1) is any one selected from the group consisting of a compound represented by the following formulas (A-8), (A-12), (A-14), (A-16), and (A-23).

7. The photoelectric conversion element according to any one of claims 1 to 6, further comprising an intermediate layer containing phthalocyanine particles between the hole transport layer and the photoelectric conversion layer.

8. A photoelectric conversion device comprising the photoelectric conversion element according to any one of claims 1 to 7.

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