Self-organizing material and perovskite solar cell using same

Abstract

This self-organizing material is represented by one of general formulae (1)-(5). In formulae (1)-(5), X1 represents a carboxyl group or a phosphono group. Y1-Y8 may be the same or different from each other, each represent a hydrogen atom, an alkyl group having 4 or less carbon atoms, or an alkoxy group having 4 or less carbon atoms, and each include at least one alkoxy group having 4 or less carbon atoms. R1-R10 may be the same or different from each other, and each represent a hydrogen atom, an alkyl group having 4 or less carbon atoms, or an alkoxy group having 4 or less carbon atoms.

Description

Self-assembled materials and perovskite solar cells using the same

[0001] The present invention relates to a self-assembled material used as a material for the hole transport layer of a perovskite solar cell, and to a perovskite solar cell using the same.

[0002] In recent years, the driving power required for electronic circuits has become extremely low, allowing various electronic components such as sensors to be driven even with very little power. Furthermore, there is growing expectation for the application of self-sustaining power sources (energy harvesting elements) that can generate and consume electricity on the spot when using sensors, and among these, solar cells are attracting attention as elements that can generate electricity anywhere there is light.

[0003] Inorganic solar cells and organic solar cells are known types of solar cells. However, inorganic solar cells use inorganic semiconductor materials such as silicon as the p-type and n-type semiconductors, which limits their range of application due to high manufacturing costs and difficulty in scaling them up. Therefore, development is currently underway on organic solar cells, which are manufactured using organic semiconductors instead of inorganic semiconductors. Organic solar cells are classified into types such as dye-sensitized solar cells, organic thin-film solar cells, and organic-inorganic hybrid solar cells.

[0004] Organic solar cells contain p-type and n-type semiconductors, and often have a hole transport layer between the photoelectric conversion layer, which absorbs light and generates positive and negative charges, and the anode. The hole transport layer plays a role in improving the photoelectric conversion efficiency of the solar cell by enabling the positive charges (holes) and negative charges (electrons) generated by photoexcitation to move efficiently without rejoining.

[0005] Among organic solar cells, solar cells equipped with a photoelectric conversion layer containing a perovskite compound, as described in Patent Document 1 and Non-Patent Documents 1 and 2 (hereinafter also referred to as perovskite solar cells), have been reported to exhibit higher photoelectric conversion efficiency than amorphous silicon solar cells in weak indoor light environments, and reports on further improvements in photoelectric conversion efficiency have been successively published. The basic structure of a perovskite solar cell is generally a laminate in which a transparent electrode (cathode), electron transport layer, photoelectric conversion layer (perovskite layer), hole transport layer, and metal electrode (anode) are stacked in this order. In some cases, a mesoporous titania layer is included between the electron transport layer and the perovskite layer, and the photoelectric conversion layer is composed of the perovskite layer and the mesoporous titania layer. Of these layers, the hole transport layer is generally composed of a material containing an organic semiconductor.

[0006] Among the organic semiconductors included in hole transport layer materials reported to date, one example is 2,2′,7,7′-tetrakis-(N,N-dimethoxyphenylamine)-9,9′-spirobifluorene (hereinafter also referred to as Spiro-OMeTAD), which was developed as a hole transport layer material for dye-sensitized solar cells and is described in Non-Patent Document 3. It is also commonly used in the aforementioned perovskite solar cells.

[0007] Furthermore, Patent Documents 2 and 3 disclose organic solar cells using [2-(3,6--dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (hereinafter also referred to as MeO-2PACz) as a hole transport material. Patent Document 4 discloses dye-sensitized solar cells using (E)-2-cyano-(3-phenylamino-triphenylene)acrylic acid derivatives.

[0008] Japanese Patent Publication No. 2016-539914, Chinese Patent Publication No. 116782681, U.S. Patent Publication No. 2023-0345745, U.S. Patent Publication No. 2010-0076205

[0009] Michael M. Lee et al., "Efficient Hybrid Solar Cells Based on Meso-Super structured Organometal Halide Perovskites", Science (2012) 338, P643-647Nam Joong Jeon et al., "Solvent engineering for high-performance in organic-organic hybrid perovskite solar cells", Nature Materials (2014) 13, P897-903Nature volume (1998) 395, P583-585

[0010] However, when Spiro-OMeTAD is used as the material for the hole transport layer, it cannot be said that sufficiently good photoelectric conversion performance is achieved. Therefore, when using this material, it is generally necessary to add a large amount of dopant such as lithium bis(trifluoromethanesulfonyl)imide (hereinafter also called LiTFSI salt) to improve photoelectric conversion performance. However, the doping with a large amount of LiTFSI salt has the problem that the solar cell has poor durability at high temperatures and high humidity. Furthermore, this compound is very expensive, and the manufacturing cost becomes high when the area is increased in order to make it practical for use as a solar cell.

[0011] Furthermore, when MeO-2PACz described in Patent Documents 2 and 3 was used as a hole transport material, the photoelectric conversion performance was not sufficient. The (E)-2-cyano-(3-phenylamino-triphenylene)acrylic acid derivative described in Patent Document 4 is only used as a photosensitizing material for dye-sensitized solar cells, and its use as a hole transport material for perovskite-type solar cells is neither described nor suggested.

[0012] In view of the above problems, the present invention aims to provide a self-assembled material that has excellent high temperature and high humidity durability and excellent photoelectric conversion properties even in weak light such as indoor light, and a perovskite solar cell using the same.

[0013] To achieve the above objective, the first configuration of the present invention is a self-assembled material represented by any of the following general formulas (1) to (5). In formulas (1) to (5), X1 represents a carboxyl group or a phosphono group. Y1 to Y8 may be the same or different, and represent a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms, and contain at least one alkoxy group having 4 or fewer carbon atoms. R1 to R 10 These may be the same or different, and represent a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms.

[0014] According to the first configuration of the present invention, by using a compound represented by any of the above formulas (1) to (5) as the material for the hole transport layer of a perovskite solar cell and photoelectric conversion element, high temperature and high humidity durability and charge (hole) mobility can be improved, and the energy conversion efficiency of the perovskite solar cell is improved.

[0015] A partial cross-sectional view of a perovskite solar cell 100 according to one embodiment of the present invention, showing an example in which the first electrode 2 is a hole injection electrode and the second electrode 7 is an electron injection electrode.

[0016] [1. Structure of Organic Solar Cells] First, a perovskite solar cell using the self-assembled material of the present invention will be described. Figure 1 is a partial cross-sectional view of a perovskite solar cell 100 according to one embodiment of the present invention. The perovskite solar cell 100 (hereinafter simply referred to as solar cell 100) comprises a substrate 1, a first electrode (transparent electrode) 2, a hole transport layer 3, a photoelectric conversion layer 4, an electron transport layer 5, a hole blocking layer 6, and a second electrode (counter electrode) 7. The first electrode 2 is provided on the substrate 1. The photoelectric conversion layer 4 is laminated on the first electrode 2 via the hole transport layer 3. The second electrode 7 is laminated on the photoelectric conversion layer 4 via the electron transport layer 5 and the hole blocking layer 6.

[0017] Alternatively, the hole transport layer 3 may be omitted, and the photoelectric conversion layer 4 may be directly laminated on the first electrode 2. In this case, the hole transport layer 3 shown in Figure 1 is omitted. When the solar cell 100 is in use, for example, light (for example, sunlight or indoor light) is irradiated onto the substrate 1 side of the solar cell 100. Alternatively, when the solar cell 100 is in use, light L may be irradiated onto the second electrode 7 side of the solar cell 100.

[0018] When light is shone on the solar cell 100, the photoelectric conversion layer 4 absorbs the light, generating excited electrons and holes. The holes generated in the photoelectric conversion layer 4 move to the first electrode 2. Meanwhile, the excited electrons move to the second electrode 7. As a result, the solar cell 100 can extract current from the first electrode 2, which acts as the positive electrode, and the second electrode 7, which acts as the negative electrode. The following describes in detail each layer that makes up the solar cell 100.

[0019] <Substrate> The substrate 1 is not particularly limited as long as it can be used for the solar cell 100. The substrate 1 may be transparent or opaque. However, if the surface of the solar cell 100 that faces the substrate 1 is the light-receiving surface, it is preferable that the substrate 1 be transparent. Examples of transparent substrates include transparent rigid substrates such as glass like quartz glass or synthetic quartz plates, and transparent flexible substrates such as transparent resin films or optical resin plates. Transparent flexible substrates have advantages such as ease of processing, reduced manufacturing costs, lighter weight, resistance to breakage, and applicability to curved surfaces.

[0020] <First Electrode> The first electrode 2 is, for example, a hole injection electrode. The first electrode 2 is not limited to a conductive material. Examples of materials that can be used as the first electrode 2 include gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), carbon (C), indium tin oxide (ITO), tin oxide (SnO2), fluorine-doped tin oxide (FTO), zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium zinc oxide (IZO), and indium gallium zinc oxide (IGZO).

[0021] Furthermore, the material of the first electrode 2 is appropriately selected considering whether the light-receiving surface of the solar cell 100 is the surface on the substrate 1 side or the surface on the second electrode 7 side. When the light-receiving surface is the surface on the substrate 1 side, the first electrode 2 is preferably a transparent electrode. Examples of materials used when the first electrode 2 is a transparent electrode include aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), ITO, FTO, ZnO-Al, and Zn-Sn-O.

[0022] The total light transmittance of the first electrode 2 is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. When the total light transmittance of the first electrode 2 is 85% or more, when the light-receiving surface of the solar cell 100 is the surface facing the substrate 1, light can be sufficiently transmitted through the first electrode 2 on the substrate 1, and the photoelectric conversion layer 4 can efficiently absorb the light.

[0023] The sheet resistance of the first electrode 2 is preferably 20 [Ω / sq] or less, and more preferably 15 [Ω / sq] or less. When the sheet resistance of the first electrode 2 is 20 [Ω / sq] or less, the charge generated in the photoelectric conversion layer 4 is sufficiently transmitted to the external circuit. The sheet resistance can be measured, for example, using a resistivity meter (Loresta AXMCP-T370, manufactured by Nitto Seiko Analytech Co., Ltd., 4-probe type) in accordance with JIS (Japanese Industrial Standards) R1637 (Test method for resistivity of fine ceramic thin films - Measurement method by 4-probe method).

[0024] The film thickness of the first electrode 2 is preferably 0.1 nm or more and 500 nm or less, and more preferably 1 nm or more and 300 nm or less. When the film thickness of the first electrode 2 is 0.1 nm or more, the sheet resistance of the first electrode 2 does not become too large, and the charge (holes) generated in the photoelectric conversion layer 4 can be sufficiently transmitted to the external circuit. On the other hand, when the film thickness of the first electrode 2 is 500 nm or less, the total light transmittance of the first electrode 2 is high.

[0025] The first electrode 2 may be a single layer. Alternatively, the first electrode 2 may be composed of multiple layers having different work functions. When the first electrode 2 consists of multiple layers, the film thickness of the first electrode 2 as described above refers to the total film thickness of the multiple layers.

[0026] The first electrode 2 is formed by sputtering, thermal deposition, plating, or spray pyrolysis. The first electrode 2 may be formed in a sheet shape over the entire surface of the substrate 1, or it may be formed in a pattern shape on the substrate 1. The shape of the first electrode 2 may be flat or uneven. Examples of uneven shapes include textured structures, pyramidal structures, wave-shaped structures, comb-shaped structures, and nanopillow structures. When the first electrode 2 is uneven, the incident light is scattered by the unevenness of the first electrode 2, so that more light is taken up by the photoelectric conversion layer 4, and the energy conversion efficiency of the solar cell 100 is improved.

[0027] <Hole Transport Layer> The hole transport layer 3 is laminated between the first electrode 2 and the photoelectric conversion layer 4. The hole transport layer 3 is provided so that holes can be easily injected (moved) from the photoelectric conversion layer 4 to the first electrode 2 (hole injection electrode). By laminating the hole transport layer 3, the hole injection efficiency from the photoelectric conversion layer 4 to the first electrode 2 is increased, and the energy conversion efficiency of the solar cell 100 is improved.

[0028] The hole transport layer 3 is preferably a self-assembled monolayer (SAM). SAM is a film obtained by adsorbing an organic compound, particularly an organic compound having an adsorption group, to an inorganic material through the adsorption group. In its adsorption mechanism, only a single molecular layer is self-assembled between the organic compound and the inorganic material.

[0029] The organic compound forming SAM generally comprises an adsorption group capable of binding to an inorganic material, a terminal group on the opposite side for controlling the surface energy of the inorganic material such as an electron-donating group or an electron-withdrawing group, and an aromatic group or a linear or branched carbon chain connecting the adsorption group and the terminal group.

[0030] Examples of the adsorption group include a phosphonyl group (-PO(OH)2), a carboxyl group (-COOH), a sulfhydryl group (-SH), a carbonyl chloride (-COCl), a carbonyl bromide (-COBr), a chlorosilane (-SiCl) and a bromosilane (-SiBr), and an alkoxysilane (-SiOR).

[0031] Examples of the terminal group include an electron-donating group such as a hydroxy group, an amino group, a (9H-carbazol-9-yl)methyl group, a methoxy group, a 4-(diphenylamino)phenyl group and a phenoxy group, and an electron-withdrawing group such as a trifluoromethyl group. Examples of the aromatic group include a phenylene group. Examples of the carbon chain include a linear or branched alkylene group.

[0032] The solar cell 100 of the present invention contains a compound represented by the following general formulas (1) to (5) in the hole transport layer 3.

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] In formulas (1) to (5), X1 represents a carboxyl group or a phosphono group. Y1 to Y8 may be the same or different and each represents a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms, and at least one of them contains an alkoxy group having 4 or fewer carbon atoms. R1 to R 10 may be the same or different and each represents a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms.

[0039] The hole transport layer 3 may contain only the compound represented by general formulas (1) to (5), or may further contain an additive. As the additive, conventionally known additives such as an interfacial treatment agent can be used.

[0040] In particular, it is preferable that X1 in formula (1) is a carboxyl group or a phosphono group, and at least one of Y1 to Y8 is a methoxy group. Specific examples of such compounds include compounds HTM-1 to HTM-3 represented by the following chemical formulas.

[0041]

[0042]

[0043]

[0044] Further, it is preferable that X1 in formula (2) is a carboxyl group or a phosphono group, and all of R1 to R8 are hydrogen atoms. Specific examples of such compounds include compound HTM-4 represented by the following chemical formula.

[0045]

[0046] Further, it is preferable that X1 in formula (3) is a carboxyl group or a phosphono group, all of R1 to R8 are hydrogen atoms, and R9, R 10Preferably, these are the same or different hydrogen atoms or methyl groups. A specific example of such a compound is the compound HTM-5, represented by the following chemical formula.

[0047]

[0048] Furthermore, it is preferable that X1 in formula (4) is a carboxyl group or a phosphono group, and that R1 to R8 are all hydrogen atoms. Specific examples of such compounds include the compounds HTM-6 and HTM-7, represented by the following chemical formulas.

[0049]

[0050]

[0051] HTM-6 is a compound described in Patent Document 4 as a photosensitizing material for dye-sensitized solar cells. In dye-sensitized solar cells, the photosensitizing material absorbs light and releases charge (electrons) after going into an excited state. On the other hand, in perovskite solar cells, the hole transport material moves charge (holes) without absorbing light. In other words, the required properties of the photosensitizing material in dye-sensitized solar cells and the hole transport material in perovskite solar cells are different. Therefore, it is difficult even for those skilled in the art to imagine using a photosensitizing material for dye-sensitized solar cells as a hole transport material in a perovskite solar cell. The fact that HTM-6 has high charge (hole) mobility when used as a hole transport material in a perovskite solar cell is a finding that was first obtained by the present inventors.

[0052] Furthermore, it is preferable that X1 in formula (5) is a carboxyl group or a phosphono group, and that R1 to R8 are all hydrogen atoms. A specific example of such a compound is the compound HTM-8, represented by the following chemical formula.

[0053]

[0054] By using a compound represented by any of the above formulas (1) to (5) as the self-assembling material constituting the hole transport layer 3, the mobility of charge (holes) can be improved, thereby increasing the energy conversion efficiency of the solar cell 100. Furthermore, the potential barrier at the material interface forming the hole transport layer 3 is reduced, making it easier to inject holes into the HOMO. As a result, even with continuous light irradiation, large level mismatches at the interface between the hole transport layer 3 and the photoelectric conversion layer 4 can be reduced. Consequently, the short-circuit current density (J) SC The attenuation of ) is suppressed, and the durability of the solar cell 100 is improved.

[0055] For the formation of the hole transport layer 3, dry processes such as vacuum deposition, sputtering, and molecular beam epitaxy, and wet processes such as spin coating, dip coating, and Langmuir-Bludget (LB) are used. From the viewpoint of ease of film formation, wet processes such as spin coating are preferred.

[0056] The thickness of the hole transport layer 3 is typically 1 to 2000 nm, preferably 1 to 1000 nm, and more preferably 1 to 500 nm. If the thickness of the hole transport layer 3 is within the above range, it will not create resistance during hole transport, and the photoelectric conversion efficiency will be high.

[0057] <Photoelectric Conversion Layer> The photoelectric conversion layer 4 converts light energy into electrical energy using photovoltaic power. When light is absorbed by the photoelectric conversion layer 4, excitons are generated, and charge separation occurs into holes and electrons. In the solar cell 100 of this embodiment, a perovskite layer is used as the photoelectric conversion layer 4.

[0058] The perovskite layer is made from a compound represented by the general formula (ABX3). This compound may be a perovskite crystal or a perovskite complex. A can be an organic amino compound such as methylamine, ethylamine, n-butylamine, di-n-butylamine, trimethylamine, triethylamine, methyl-n-hexylamine, methyldiethylamine, tri-n-hexylamine, imidazole, pyrrole, aziridine, formamidine, guanidine, pyridine, 4-t-butylpyridine, phenethylamine, 5-aminovaleric acid, or a monovalent cation formed from cesium, potassium, rubidium, etc., and may be used alone or as a mixture of two or more. B can be a divalent cation such as lead or tin, and may be used alone or in a mixture. In addition, a small amount of a trivalent cation such as indium or antimony may be mixed in. X can be a halogen atom or anion source such as chlorine, bromine, or iodine, and may be used alone or in a mixture of two or more.

[0059] The thickness of the photoelectric conversion layer 4 is not particularly limited, as long as the desired energy conversion efficiency can be obtained. Preferably, the thickness of the photoelectric conversion layer 4 is 50 nm or more and 1000 nm or less, and more preferably 300 nm or more and 600 nm or less. When the thickness of the photoelectric conversion layer 4 is 1000 nm or less, the sheet resistance of the photoelectric conversion layer 4 is more likely to be the desired value. On the other hand, when the thickness of the photoelectric conversion layer 4 is 50 nm or more, a short circuit between the first electrode 2 and the second electrode 7 is less likely to occur. Also, if the thickness of the photoelectric conversion layer 4 is within the above range, it is less likely to become a resistance during hole transport, and the photoelectric conversion efficiency of the solar cell 100 is increased.

[0060] <Electron Transport Layer> The electron transport layer 5 is laminated between the photoelectric conversion layer 4 and the hole blocking layer 6. The electron transport layer 5 is provided to facilitate the injection (movement) of electrons from the photoelectric conversion layer 4 to the second electrode 7 (electron injection electrode). By laminating the electron transport layer 5, the electron injection efficiency from the photoelectric conversion layer 4 to the second electrode 7 is increased, and the energy conversion efficiency of the solar cell 100 is improved.

[0061] The material contained in the electron transport layer 5 (electron transport layer material) is not particularly limited as long as it is a material that can stably inject electrons from the photoelectric conversion layer 4 to the second electrode 7. Examples of electron transport layer materials include conductive organic compounds, charge transfer complexes, alkali metals, alkaline earth metals, and organic compounds and metal oxides doped with alkali metals or alkaline earth metals.

[0062] Examples of alkali metals that can be used as electron transport layer materials include lithium, sodium, potassium, rubidium, and cesium. Examples of alkaline earth metals that can be used as electron transport layer materials include beryllium, magnesium, calcium, strontium, and barium. Examples of alkali metal or alkaline earth metal-doped organic compounds that can be used as electron transport layer materials include bathocuproine (BCP) and batphenanthroline (Bphen) doped with alkali metals or alkaline earth metals. Preferred alkali metals and alkaline earth metals used for doping are lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, or barium, with lithium, cesium, barium, or strontium being more preferred. Examples of metal oxides that can be used as electron transport materials include titanium oxide, zinc oxide, and tin oxide.

[0063] When the electron transport layer material is a conductive organic compound, a charge transfer complex, or a metal oxide, the film thickness of the electron transport layer 3 is preferably 10 nm or more and 200 nm or less. When the electron transport layer material is an alkali metal, an alkaline earth metal, or an organic compound doped with an alkali metal or alkaline earth metal, the film thickness of the electron transport layer 5 is preferably 0.1 nm or more and 50 nm or less.

[0064] <Hole Blocking Layer> The hole blocking layer 6 improves the flow of electrons generated in the photoelectric conversion layer 4 to the second electrode 7, thereby improving the photoelectric conversion efficiency. Specifically, it prevents the movement of holes to the second electrode 7 and prevents a short circuit between the negative electrode, the second electrode 7, and the photoelectric conversion layer 4.

[0065] The materials used for the hole blocking layer 6 are the same as those used for the electron transport layer 5. For example, n-type semiconductor materials such as phenanthroline derivatives such as bathocproine (BCP), fullerene (C60), naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic diimide, perylenetetracarboxylic anhydride, and perylenetetracarboxylic diimide; amine compounds such as amine-based silane coupling agents; and n-type inorganic oxides such as titanium dioxide (TiOx), zinc oxide (ZnO), and gallium(III) oxide (Ga2O3).

[0066] The thickness of the hole blocking layer 6 is typically 5 to 50 nm. From the viewpoint of preventing leakage current, 5 to 1000 nm is preferred, and from the viewpoint of maintaining high transmittance and low resistance, 5 to 150 nm is more preferred.

[0067] <Second Electrode> The second electrode 7 is, for example, an electron injection electrode. The second electrode 7 is a counter electrode provided opposite the first electrode 2. The second electrode 7 is not particularly limited as long as it is conductive. The material of the second electrode 7 is appropriately selected, for example, taking into consideration the work function of the electron transport layer 5. If the material of the electron transport layer 5 is a material with a low work function, it is preferable that the material of the second electrode 7 is a material with a high work function.

[0068] Examples of materials that can be used as the material for the second electrode 7 include gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), carbon (C), indium tin oxide (ITO), tin oxide (SnO2), fluorine-doped tin oxide (FTO), and zinc oxide (ZnO).

[0069] Furthermore, the material of the second electrode 7 is appropriately selected, for example, by considering whether the light-receiving surface of the solar cell 100 is the surface on the substrate 1 side or the surface on the second electrode 7 side. If the light-receiving surface is the surface on the substrate 1 side, the first electrode 2 is preferably a transparent electrode, but the second electrode 7 does not have to be a transparent electrode.

[0070] The film thickness of the second electrode 7 is preferably 0.1 nm or more and 500 nm or less, and more preferably 1 nm or more and 300 nm or less. When the film thickness of the second electrode 7 is 0.1 nm or more, the sheet resistance of the second electrode 7 does not become too large, and the charge generated in the photoelectric conversion layer 4 can be sufficiently transmitted to the external circuit.

[0071] The second electrode 7 may be a single layer. Alternatively, the second electrode 7 may be composed of multiple layers having different work functions. When the second electrode 7 consists of multiple layers, the film thickness of the second electrode 7 as described above refers to the total film thickness of the multiple layers.

[0072] The second electrode 7 may be formed in a sheet shape over the entire surface of the electron transport layer 5, or it may be formed in a pattern shape on the electron transport layer 5.

[0073] <Other Components> In addition to the substrate 1, first electrode 2, hole transport layer 3, photoelectric conversion layer 4, electron transport layer 5, and second electrode 7 described above, the solar cell 100 may further include other components as needed. Examples of other components include a protective sheet layer, a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an anti-fouling layer, a high light reflectivity layer, a light containment layer, an ultraviolet blocking layer, an infrared blocking layer, and a sealing layer. Furthermore, adhesive layers may be laminated between each layer of the solar cell 100 as needed.

[0074] Furthermore, the solar cell 100 is not limited to the structure shown in Figure 1. For example, the first electrode 2 may be an electron injection electrode and the second electrode 7 may be a hole injection electrode. In that case, the stacking order of the hole transport layer 3 and the electron transport layer 5 will be reversed from that in Figure 1, and the hole blocking layer 6 will not be necessary. Specifically, as shown in Figure 2, the electron transport layer 5 is stacked between the first electrode 2 and the photoelectric conversion element 4, and the hole transport layer 3 is stacked between the photoelectric conversion element 4 and the second electrode 7.

[0075] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, an example was given in which the self-assembled material of the present invention was used as a hole transport layer 3 of a solar cell 100, but it is not limited to a solar cell 100, and can also be used, for example, as a hole transport layer of a photoelectric conversion element.

[0076] As an example of a photoelectric conversion element, for instance, a semiconductor electrode (first electrode) is fabricated by laminating a hole-blocking layer and a porous electron transport layer on a glass substrate, and further supporting a photosensitizing material. A hole transport layer is formed on this semiconductor electrode (first electrode) by spin coating using a solution of the self-assembled material of the present invention dissolved in an organic solvent, and a second electrode is formed by laminating silver on the formed hole transport layer using a vacuum deposition method. The effects of the present invention will be further explained in detail below with reference to examples.

[0077] [Synthesis examples of HTM-1 to HTM-8] [1-1. [Synthesis of HTM-1] (1-1-1. Synthesis of Intermediate-1) A stirring bar was placed in a 500 mL two-necked flask equipped with a reflux condenser, and 2,4-dimethoxyaniline represented by chemical formula (A) (18.02 g, 0.12 mol), 4-bromoanisole represented by chemical formula (B) (20.00 g, 0.11 mol), tris(dibenzylideneacetone)dipalladium(0) (hereinafter referred to as Pd2(dba)3) (0.490 g, 0.0005 mol), 4,5-bis(diphenylphosphin)-9,9-dimethylxanthene (hereinafter referred to as Xantphos) (0.510 g, 0.0011 mol), and sodium-t-butoxide (11.29 g, 0.12 mol) were charged in, and the system was purged with nitrogen. Next, 350g of xylene was added, and the mixture was heated to 100°C while stirring with a magnetic stirrer, and the reaction was allowed to proceed for 3.5 hours.

[0078] After the reaction, the mixture was adsorbed twice with activated clay (SA-1, manufactured by Nippon Activated Clay Co., Ltd.). After concentrating the filtrate, isohexane / methanol was added to precipitate the solid. The solid was filtered and vacuum-dried to obtain the primary solid. The obtained primary solid was purified by silica gel column chromatography using toluene:isohexane = 1:1 as the developing solvent, concentrated, and vacuum-dried to obtain intermediate-1 (reddish-brown oily substance; yield 25.4 g, yield 84.9%, HPLC purity 99.7%). The synthesis scheme is shown below.

[0079]

[0080] (1-1-2. Synthesis of Intermediate-1') A stirring bar was placed in a 500 mL two-necked flask equipped with a reflux condenser, and intermediate-1 (9.076 g, 0.0350 mol), 1-bromo-4-iodobenzene (10.100 g, 0.0357 mol), Pd2(dba)3 (0.032 g, 0.00004 mol), Xantphos (0.041 g, 0.00007 mol), and sodium-t-butoxide (4.368 g, 0.0455 mol) were charged in, and the system was purged with nitrogen. Then, 59.455 g of xylene was added, and the temperature was raised to 130°C while stirring with a magnetic stirrer, and the reaction was carried out for 3.5 hours.

[0081] After the reaction, the mixture was adsorbed twice with activated clay (SA-1, manufactured by Nippon Activated Clay Co., Ltd.). The filtrate was concentrated and then vacuum-dried to obtain an oily primary solid. The obtained primary solid was purified by silica gel column chromatography using toluene:isohexane = 1:2 as the developing solvent, concentrated, and vacuum-dried to obtain intermediate-1' (oily; yield 12.20 g, yield 84.1%, HPLC purity 97.7%). The synthesis scheme is shown below.

[0082]

[0083] (1-1-3. Synthesis of Intermediate-1") A stirring bar was placed in a 500 mL three-necked flask equipped with a reflux condenser, and the following were charged: intermediate-1' (3.314 g, 0.0080 mol), 4-formylphenylboronic acid (1.699 g, 0.00113 mol), palladium acetate (hereinafter referred to as Pd(OAc)2) (0.180 g, 0.00080 mol), and triphenylphosphine (hereinafter referred to as PPh3) (0.839 g, 0.00320 mol). The system was then purged with nitrogen. A 2 mol / L aqueous solution of potassium carbonate, prepared by dissolving 7.371 g (0.0533 mol) of potassium carbonate in 26.667 g of deionized water, and 115.376 g of tetrahydrofuran (hereinafter referred to as THF; dehydrated, additive-free) were added. The mixture was heated to 80°C while stirring with a magnetic stirrer and allowed to react for 3 hours.

[0084] After the reaction, the reaction mixture was filtered while hot, and the organic layer was extracted by liquid-liquid treatment with deionized water. The organic layer was adsorbed with activated clay (SA-1, manufactured by Nippon Activated Clay Co., Ltd.). The filtrate was dehydrated with sodium sulfate, concentrated, and then vacuum-dried to obtain an oily primary solid. The obtained primary solid was purified by silica gel column chromatography using toluene:THF = 98:2 as the developing solvent, concentrated, and vacuum-dried to obtain intermediate-1'' (oily; yield 3.40 g, yield 96.7%, HPLC purity 98.1%). The synthesis scheme is shown below.

[0085]

[0086] (1-1-4. Synthesis of HTM-1) A stirring bar, intermediate-1" (2.285 g, 0.0052 mol), and cyanoacetic acid (4.423 g, 0.0520 mol) were charged into a 500 mL three-necked flask equipped with a reflux condenser, and the system was purged with nitrogen. Then, piperidine (1.399 g, 0.0164 mol) and 51.230 g of acetonitrile were added, and the mixture was heated to 100°C while stirring with a magnetic stirrer and reacted for 6 hours.

[0087] After the reaction, the reaction mixture was filtered while hot, the filtrate was concentrated, and then vacuum-dried to obtain a brown-black primary solid. The obtained primary solid was purified by silica gel column chromatography using toluene:THF = 1:1 as the developing solvent, concentrated, and then precipitated by adding toluene and isohexane. Compound HTM-1 was obtained by filtering the solid (reddish-brown solid; yield 0.98 g, yield 37.2%, HPLC purity 99.1%). The synthesis scheme is shown below.

[0088]

[0089] [1-2. Synthesis of HTM-2] (1-2-1. Synthesis of Intermediate-2) Intermediate-2 was synthesized by the same method as in "1-1-1. Synthesis of Intermediate-1" above, except that 4-bromoanisole (20.00 g, 0.11 mol) was replaced with 2,4-dimethoxy-1-bromobenzene (23.88 g, 0.11 mol) (yield 75.0%, HPLC purity 97.7%).

[0090]

[0091] (1-2-2. Synthesis of Intermediate-2') Intermediate-2' was synthesized by the same method as in "1-1-2. Synthesis of Intermediate-1'" above, except that intermediate-1 (9.076 g, 0.0350 mol) was replaced with intermediate-2 (10.13 g, 0.0350 mol) (yield 14.6%, HPLC purity 98.3%).

[0092]

[0093] (1-2-3. Synthesis of Intermediate-2") Intermediate-2" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-2' (3.55 g, 0.0080 mol) (yield 42.6%, HPLC purity 97.2%).

[0094]

[0095] (1-2-4. Synthesis of HTM-2) Compound HTM-2 was synthesized by the same method as in "1-1-4. Synthesis of HTM-1" above, except that intermediate-1" (2.285 g, 0.0052 mol) was replaced with intermediate-2" (2.442 g, 0.0052 mol) (yield 96.73%, HPLC purity 98.7%).

[0096] [1-3. Synthesis of HTM-3] (1-3-1. Synthesis of Intermediate-3') Intermediate-3' was synthesized by the same method as in "1-1-2. Synthesis of Intermediate-1'" above, except that intermediate-1 (9.076 g, 0.0350 mol) was replaced with bis(3,4,5-trimethoxyphenyl)amine (12.23 g, 0.0350 mol) (yield 74.6%, HPLC purity 97.5%).

[0097]

[0098] (1-3-2. Synthesis of Intermediate-3") Intermediate-3" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-3' (4.035 g, 0.0080 mol) (yield 37.2%, HPLC purity 97.8%).

[0099]

[0100] (1-3-3. Synthesis of HTM-3) Compound HTM-3 was synthesized by the same method as in "1-1-4. Synthesis of HTM-1" above, except that intermediate -1" (2.285 g, 0.0052 mol) was replaced with intermediate -3" (2.754 g, 0.0052 mol) (yield 75.3%, HPLC purity 98.4%).

[0101] [1-4. Synthesis of HTM-4] (1-4-1. Synthesis of Intermediate-4') Intermediate-4' was synthesized in the same manner as in "1-1-2. Synthesis of Intermediate-1'" above, except that intermediate-1 (9.076 g, 0.0350 mol) was replaced with bis(4-methoxyphenyl)amine (8.025 g, 0.0350 mol) and 1-bromo-4-iodobenzene (10.100 g, 0.0357 mol) was replaced with 4-iodobromonaphthalene (11.89 g, 0.0357 mol) (yield 87.5%, HPLC purity 96.5%).

[0102]

[0103] (1-4-2. Synthesis of Intermediate-4") Intermediate-4" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-5' (3.475 g, 0.0080 mol) (yield 87.0%, HPLC purity 98.9%).

[0104]

[0105] (1-4-3. Synthesis of HTM-4) Compound HTM-4 was synthesized by the same method as in "1-1-4. Synthesis of HTM-1" above, except that intermediate -1" (2.285 g, 0.0052 mol) was replaced with intermediate -4" (2.390 g, 0.0052 mol) (yield 43.0%, HPLC purity 91.0%).

[0106] [1-5. Synthesis of HTM-5] (1-5-1. Synthesis of Intermediate-5') Intermediate-5' was synthesized by the same method as in "1-4-2. Synthesis of Intermediate-4'" above, except that 4-iodobromonaphthalene (11.89 g, 0.0357 mol) was replaced with 2-bromo-7-iodo-9,9-dimethyl-9H-fluorene (14.25 g, 0.0357 mol) (yield 50.0%, HPLC purity 93.5%).

[0107]

[0108] (1-5-2. Synthesis of Intermediate-5") Intermediate-5" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-5' (4.003 g, 0.0080 mol) (yield 56.8%, HPLC purity 98.3%).

[0109]

[0110] (1-5-3. Synthesis of HTM-5) Compound HTM-5 was synthesized by the same method as in "1-1-4. Synthesis of HTM-1" above, except that intermediate -1" (2.285 g, 0.0052 mol) was replaced with intermediate -5" (2.733 g, 0.0052 mol) (yield 71.6%, HPLC purity 98.3%).

[0111] [1-6. Synthesis of HTM-6'] (1-6-1. Synthesis of Intermediate-6) Intermediate-6' was synthesized by the same method as in "1-4-2. Synthesis of Intermediate-4'" above, except that 4-iodobromonaphthalene (11.89 g, 0.0357 mol) was replaced with 4-(4-bromophenyl)iodobenzene (12.82 g, 0.0357 mol) (yield 40.1%, HPLC purity 99.9%).

[0112]

[0113] (1-6-2. Synthesis of Intermediate-6") Intermediate-6" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-6' (3.683 g, 0.0080 mol) (yield 61.3%, HPLC purity 99.9%).

[0114]

[0115] (1-6-3. Synthesis of HTM-6) Compound HTM-5 was synthesized in the same manner as described in "1-1-4. Synthesis of HTM-1" above, except that intermediate -1" (2.285 g, 0.0052 mol) was replaced with intermediate -6" (2.525 g, 0.0052 mol) (yield 39.0%, HPLC purity 98.8%).

[0116] [1-7. Synthesis of HTM-7] (1-7-1. Synthesis of Intermediate-7) A stirring bar was placed in a 500 mL triple flask equipped with a reflux condenser, along with 4-(4-bromophenyl)-N,N-bis(4-methoxyphenyl)aniline represented by chemical formula (A) (8.517 g, 0.0185 mol), 4-formylphenylboronic acid represented by chemical formula (B) (3.295 g, 0.02618 mol), Pd(OAc)2 (0.415 g, 0.00185 mol), and PPh3 (1.939 g, 0.00739 mol), and the system was purged with nitrogen. A 2 mol / L potassium carbonate aqueous solution was prepared by dissolving 17.027 g (0.1232 mol) of potassium carbonate in 61.6 g of deionized water. 266.519 g of THF (dehydrated, additive-free) was added, and the mixture was heated to 90°C while stirring with a magnetic stirrer, and the reaction was allowed to proceed for 8 hours.

[0117] After the reaction, the reaction mixture was filtered while hot, and the organic layer was extracted by liquid-liquid extraction with deionized water. The organic layer was dehydrated with sodium sulfate, and after adsorption treatment with activated clay (SA-1, manufactured by Nippon Activated Clay Co., Ltd.), it was concentrated. Furthermore, it was purified by silica gel column chromatography using toluene:isohexane = 1:1 as the developing solvent, concentrated, and then precipitated by adding isohexane. The solid was filtered and vacuum-dried to obtain intermediate-7 (yield 5.51 g, yield 61.3%, HPLC purity 99.9%). The synthesis scheme is shown below.

[0118]

[0119] (1-7-2. Synthesis of Intermediate-7') A stirring bar and intermediate-7 (2.427 g, 0.0050 mol) were placed in a 500 mL tri-flask equipped with a reflux condenser, and the system was purged with nitrogen. Diethyl cyanomethylphosphonate (2.037 g, 0.0115 mol), piperidine (1.618 g, 0.0190 mol), and 64.243 g of toluene were added sequentially, and the temperature was raised to 115°C while stirring with a magnetic stirrer, and the reaction was carried out for 4 hours. After the reaction, the reaction mixture was concentrated.

[0120] The concentrated reaction solution was purified by silica gel column chromatography using chloroform:methanol = 97:3 as the developing solvent, and then concentrated to obtain intermediate-7' (yield 1.05 g, yield 32.6%, HPLC purity 97.8%). The synthesis scheme is shown below.

[0121]

[0122] (1-7-3. Synthesis of HTM-7) A stirring bar and intermediate-7' (1.154 g, 0.00203 mol) were placed in a 500 mL triple flask equipped with a reflux condenser. After purging the system with nitrogen, chloroform (146.035 g, 1.22308 mol) was added. Bromotrimethylsilane (3.108 g, 0.0203 mol) was placed in a dropping funnel and added dropwise. The mixture was stirred at 60°C for 7 hours using a magnetic stirrer, then 39.675 g of methanol was added and the mixture was stirred for 4 hours.

[0123] After the reaction, the mixture was adsorbed using activated clay (SA-1, manufactured by Nippon Activated Clay Co., Ltd.), and the filtrate was concentrated. Further purification was performed by silica gel column chromatography using chloroform / methanol as the developing solvent, followed by concentration and crystallization to precipitate the solid. The solid was filtered and vacuum-dried to obtain compound HTM-7 (yield 0.191 g, yield 16.0%, HPLC purity 96.9%). The synthesis scheme is shown below.

[0124]

[0125] [1-8. Synthesis of HTM-8] (1-8-1. Synthesis of Intermediate-8') Intermediate-8' was synthesized by the same method as in "1-4-2. Synthesis of Intermediate-4'" above, except that 4-iodobromonaphthalene (11.89 g, 0.0357 mol) was replaced with 1-bromo-3,5-diiodobenzene (14.59 g, 0.0357 mol) (yield 65.4%, HPLC purity 97.9%).

[0126]

[0127] (1-8-2. Synthesis of Intermediate-8") Intermediate-8" was synthesized by the same method as in "1-1-3. Synthesis of Intermediate-1" above, except that intermediate-1' (3.314 g, 0.0080 mol) was replaced with intermediate-8' (4.892 g, 0.0080 mol) (yield 77.5%, HPLC purity 99.5%).

[0128]

[0129] (1-8-3. Synthesis of HTM-8) Compound HTM-8 was synthesized by the same method as in "1-1-4. Synthesis of HTM-1" above, except that intermediate -1" (2.285 g, 0.0052 mol) was replaced with intermediate -8" (3.311 g, 0.0052 mol) (yield 33.2%, HPLC purity 99.2%).

[0130] [Manufacturing of Perovskite Solar Cells] As a substrate, an ITO (film thickness: 130 nm, sheet resistance: 10 Ω / sq) / glass substrate was ultrasonically cleaned for 20 minutes each in the following order: 10% neutral detergent aqueous solution (Clean Ace S, manufactured by AS ONE Corporation), deionized water, isopropyl alcohol, and acetone. After nitrogen blowing, it was dried in a clean oven at 60°C for 12 hours. Immediately before film deposition, the ITO / glass substrate was removed from the clean oven and cleaned for 30 minutes using a UV-ozone device (UV-ozone treatment).

[0131] Next, compound HTM-1 (0.67 mg) synthesized in Example 1 was dissolved in 1 mL of tetrahydrofuran (THF), and the mixture was spin-coated onto an ITO / glass substrate at 3000 rpm for 30 seconds, followed by heating at 100°C for 10 minutes.

[0132] Furthermore, 2130 mg of lead(II) iodide (PbI2) and 722 mg of formamidine hydroiodide (HC(=NH)NH2・HI) were dissolved in a mixed solvent of 2.8 mL of N,N-dimethylformamide (DMF) and 0.7 mL of dimethyl sulfoxide (DMSO) to prepare a 1.2 M FAPbI3 solution (containing 10 mol% excess PbI2). 1696 mg of lead(II) bromide (PbBr2) and 470 mg of methylamine hydrobromide (CH3NH2・HBr) were dissolved in a mixed solvent of 2.8 mL of DMF and 0.7 mL of DMSO to prepare a 1.2 M MAPbBr3 solution (containing 10 mol% excess PbBr2).

[0133] A perovskite solution was prepared by mixing 1.2 M FAPbI3 solution and MAPbBr3 solution in a volume ratio of 76:24 (vol / vol). To 960 μL of this mixed solution, 40 μL of DMSO solution containing 386 mg of cesium iodide (CsI) was added. This perovskite solution was spin-coated onto HTM-1 at 5000 rpm for 35 seconds. Ten seconds after the start of spin-coating, ethyl acetate was added dropwise, and then the mixture was heated at 100°C for 1 hour to deposit a perovskite layer (photoelectric conversion layer).

[0134] Next, 20 nm fullerene (C 60), 8 nm of bathocuproine (BCP), and 70 nm of Ag electrode were sequentially deposited under high vacuum to fabricate the perovskite solar cell of Invention 1 as shown in FIG. 1.

[0135] The device structure of the obtained perovskite organic solar cell (substrate 1 / first electrode (transparent electrode) 2 / hole transport layer 3 / photoelectric conversion layer (perovskite layer) 4 / electron transport layer 5 / hole blocking layer 6 / second electrode (counter electrode) 7) is as follows. (Glass / ITO) / HTM-1 / Cs 0.05 (FA 0.76 MA 0.24 ) 0.95 Pb(I 0.76 Br 0.24 )3 / C 60 (20 nm) / BCP(8 nm) / Ag(70 nm)

[0136] Perovskite solar cells of Inventions 2 to 8 were fabricated in the same manner as above, except that compounds HTM-2 to HTM-8 were used instead of the compound HTM-1.

[0137] A perovskite solar cell of Comparative Example 1 was fabricated in the same manner as above, except that MeO-2PACz was used instead of the compound HTM-1.

[0138] [Evaluation of Photovoltaic Conversion Characteristics of Perovskite Solar Cells] The photovoltaic conversion efficiencies of the perovskite solar cells of Inventions 1 to 8 and Comparative Example 1 fabricated in Example 2 were evaluated. A solar simulator (HAL-320, manufactured by Asahi Spectroscopic Instruments Co., Ltd.) was used as the measuring device, and the light quantity of the measuring light source was adjusted to 100 mW / cm 2 using a reference solar cell. In actual measurement, the J-V curve characteristics were measured using a source meter (Model 6242, manufactured by Agilent Technologies) while irradiating the solar cell element masked so that the measurement area became 0.1 cm 2 . The measurement was performed once each under the conditions of Forward (forward scan, scanning in the direction of increasing voltage) and Reverse (reverse scan, scanning in the direction of decreasing voltage) (a total of 2 times), and the conversion efficiency was used.

[0139] From the measurement results, the short-circuit current of Reverse (Jsc [mA / cm2 ]), open-circuit voltage (Voc [V]), curve factor (FF [mW / cm 2 The following was derived: Furthermore, the photoelectric conversion efficiency (PCE [%]) was calculated using the following formula: PCE = (Jsc × Voc × FF / 100) × 100 The PCE of the perovskite solar cells of Inventions 1 to 8 and Comparative Example 1 are shown in Table 1, along with the types of Jsc, Voc, FF, and self-assembled materials.

[0140]

[0141] As shown in Table 1, the perovskite solar cells of Invention 1 to 8, which used compounds HTM-1 to HTM-8 as hole transport layers, all had a PCE of 16.1% or higher, showing a photoelectric conversion efficiency higher than that of the organic solar cell of Comparative Example 1, which used Spiro-OMeTAD as the hole transport material. In particular, the organic solar cells of Invention 1 to 4, which used HTM-1 to 4 as hole transport materials, all had a PCE of 17% or higher, showing an extremely high photoelectric conversion efficiency.

[0142] Based on these results, it was confirmed that using compounds HTM-1 to HTM-8 as the hole transport layer in a perovskite solar cell can effectively improve the photoelectric conversion efficiency of the perovskite solar cell.

[0143] The present invention is applicable to self-assembled materials and perovskite solar cells using the same. By utilizing the present invention, it is possible to provide self-assembled materials and perovskite solar cells using the same that have excellent resistance to high temperatures and high humidity and excellent photoelectric conversion even under weak light such as indoor light.

Claims

1. A self-assembling material represented by any of the following general formulas (1) to (5). (In formulas (1) to (5), X1 represents a carboxyl group or a phosphono group. Y1 to Y8 may be the same or different, and represent a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms, and contain at least one alkoxy group having 4 or fewer carbon atoms. R1 to R 10 These may be the same or different, and represent a hydrogen atom, an alkyl group having 4 or fewer carbon atoms, or an alkoxy group having 4 or fewer carbon atoms.

2. In the self-assembled material according to claim 1, X1 of the general formula (1) is a carboxyl group or a phosphono group, and at least one of Y1 to Y8 is a methoxy group.

3. In the self-assembled material according to claim 1, X1 in the general formula (2) is a carboxyl group or a phosphono group, and R1 to R8 are all hydrogen atoms.

4. In the self-assembled material according to claim 1, X1 of the general formula (3) is a carboxyl group or a phosphono group, R1 to R8 are all hydrogen atoms, and R9, R 10 They are the same or different hydrogen atoms or methyl groups.

5. In the self-assembled material according to claim 1, X1 in the general formula (4) is a carboxyl group or a phosphono group, and R1 to R8 are all hydrogen atoms.

6. In the self-assembled material according to claim 1, X1 in the general formula (5) is a carboxyl group or a phosphono group, and R1 to R8 are all hydrogen atoms.

7. A perovskite solar cell comprising: a substrate; a first electrode which is a hole injection electrode laminated on the substrate; a hole transport layer laminated on the first electrode; a photoelectric conversion layer laminated on the hole transport layer; an electron transport layer laminated on the photoelectric conversion layer; a hole blocking layer laminated on the electron transport layer; and a second electrode which is an electron injection electrode laminated on the hole blocking layer, wherein the hole transport layer comprises the self-assembled material described in claim 1.

8. A perovskite solar cell comprising: a substrate; a first electrode which is an electron injection electrode laminated on the substrate; an electron transport layer laminated on the first electrode; a photoelectric conversion layer laminated on the electron transport layer; a hole transport layer laminated on the photoelectric conversion layer; and a second electrode which is a hole injection electrode laminated on the hole transport layer, wherein the hole transport layer comprises the self-assembled material described in claim 1.

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