Perovskite solar cell, liquid composition, and method for manufacturing a perovskite solar cell

Abstract

To provide a perovskite solar cell with high photoelectric conversion efficiency, a liquid composition suitably used for forming a hole transport layer in the manufacturing of the perovskite solar cell, and a method for manufacturing a perovskite solar cell using the liquid composition. [Solution] In a perovskite solar cell comprising a first electrode layer, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode layer in this order, A self-assembled monolayer containing a hole transport material having bonding groups that exert an attractive interaction with the first electrode layer or are capable of forming bonds with the first electrode layer is provided as the hole transport layer. The hole transport material contains a single-legged hole transport material having one binding group and a multi-legged hole transport material having two or more binding groups.

Description

[Technical Field]

[0001] The present invention relates to a perovskite solar cell, a liquid composition, and a method for producing a perovskite solar cell. [Background technology]

[0002] The use of solar cells is expanding as an energy source with a low environmental impact. When installing solar cells in various devices, vehicles, buildings, etc., the available installation area is limited, making the photoelectric conversion efficiency of the solar cells important. Perovskite solar cells, which use organic materials, are being researched as solar cells with high photoelectric conversion efficiency. A basic perovskite solar cell consists of a substrate on which a first electrode (anode or cathode), a hole transport layer (hole transport layer or electron transport layer), a photoelectric conversion layer (perovskite layer), an electron transport layer (electron transport layer or hole transport layer), and a first electrode (cathode or anode) are stacked in this order. Furthermore, it is known that the photoelectric conversion efficiency can be improved by providing a first buffer layer between the first electrode and the hole transport layer, or by providing a second buffer layer between the electron transport layer and the second electrode.

[0003] Furthermore, Patent Document 1 describes a solar cell in which a monolayer is formed on the surface of a first electrode laminated on a substrate, a photoelectric conversion layer is directly laminated on the monolayer, and an electron transport layer and a transparent electrode are further laminated. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-141165 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Patent Document 1 recommends adding a hole transport layer between the monolayer and the photoelectric conversion layer to enable more efficient charge extraction. The hole transport layer improves photoelectric conversion efficiency by increasing the selectivity of holes that reach the electrodes.

[0006] However, there is a need for further improvements in the photoelectric conversion efficiency of perovskite solar cells, and there is room to improve the hole transport layer in order to increase the photoelectric conversion efficiency.

[0007] The object of the present invention is to provide a perovskite solar cell with high photoelectric conversion efficiency, a liquid composition suitably used for forming a hole transport layer in the manufacture of the perovskite solar cell, and a method for manufacturing a perovskite solar cell using the liquid composition. [Means for solving the problem]

[0008] A perovskite solar cell according to one aspect of the present invention comprises a first electrode layer, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode layer in this order. The hole transport layer is a self-assembled monolayer containing a hole transport material having bonding groups that exert an attractive interaction with the first electrode layer or are capable of forming bonds with the first electrode layer. The hole transport material includes a single-legged hole transport material having one bonding group and a multi-legged hole transport material having two or more bonding groups. The bonding group is given by the following formula (A): -R 1 -R 2 ...(A) It is a base represented by, R 1 However, it is a divalent organic group with 1 to 12 carbon atoms. R 2 A perovskite solar cell in which the group is a phosphonic acid group, carboxyl group, sulfonic acid group, boric acid group, hydroxyl group, amino group, silyl group, or mercapto group.

[0009] In the perovskite solar cell described above, The single-legged positive hole transporting material is a compound in which one hydrogen atom is substituted with the bonding group in a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom. The multi-legged positive hole transporting material may be a compound in which two or more hydrogen atoms are substituted with the bonding group in a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom.

[0010] The above nitrogen-containing aromatic compound may be one or more compounds selected from the compounds represented by the following formulas (A1) to (A3).

Chemical formula

[0011] When the above nitrogen-containing aromatic compound is one or more compounds selected from the compounds represented by the following formulas (A1) to (A3), The single-legged positive hole transporting material is one or more compounds represented by the following formula (A1-1), and the multi-legged positive hole transporting material may be one or more compounds selected from the compound represented by the following formula (A2-1) and the compound represented by the following formula (A3-1).

Chemical formula

[0012] In the perovskite solar cell described above, R 1 However, it is an alkylene group with 1 to 6 carbon atoms, R 2 It may also be a phosphonic acid group.

[0013] In the perovskite solar cell described above, the ratio of the mass of the single-legged hole transport material to the sum of the mass of the single-legged hole transport material and the mass of the multi-legged hole transport material may be 5% by mass or more and 50% by mass or less.

[0014] A liquid composition according to one aspect of the present invention is a liquid composition for forming a hole layer transport layer in a perovskite solar cell, The material comprises a single-legged hole transport material having one bonding group and a multi-legged hole transport material having two or more bonding groups. The bonding group is given by the following formula (A): -R 1 -R 2 ...(A) It is a base represented by, R 1 However, it is a divalent organic group with 1 to 12 carbon atoms. R 2 The liquid composition is a phosphonic acid group, a carboxyl group, a sulfonic acid group, a boric acid group, a hydroxyl group, an amino group, a silyl group, or a mercapto group.

[0015] The liquid composition described above may further contain a perovskite precursor and / or a passivation material.

[0016] A method for manufacturing a perovskite solar cell according to one aspect of the present invention is: The above liquid composition is applied to a first electrode layer formed on one main surface of a plate-shaped or sheet-shaped substrate to form a hole transport layer. Forming a photoelectric conversion layer containing a perovskite compound on a hole transport layer, Forming an electron transport layer on the photoelectric conversion layer, The method includes forming a second electrode layer on an electron transport surface.

[0017] In the method for manufacturing a perovskite solar cell described above, the liquid composition comprises a perovskite precursor and a passivation material. A hole transport layer and a photoelectric conversion layer are formed in this order by coating the liquid composition onto the first electrode layer, and a passivation material may be present on the surface and / or inside the photoelectric conversion layer. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a perovskite solar cell with high photoelectric conversion efficiency, a liquid composition suitably used for forming a hole layer transport layer in the manufacture of the perovskite solar cell, and a method for manufacturing a perovskite solar cell using the liquid composition. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic cross-sectional view showing the configuration of an embodiment of the solar cell according to the present invention. [Figure 2] This flowchart shows the procedure for an embodiment of the solar cell manufacturing method according to the present invention. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions of various components in the drawings have been adjusted for ease of viewing. Furthermore, in embodiments described later, components similar to those described earlier are denoted by the same reference numerals, and redundant explanations may be omitted.

[0021] [Embodiment] Figure 1 is a schematic cross-sectional view showing the configuration of a perovskite solar cell 1 according to an embodiment of the present invention. The perovskite solar cell 1 comprises a plate-shaped or sheet-shaped substrate 10, a first electrode layer 20 laminated on one main surface of the substrate 10 (the lower side in Figure 1), a hole transport layer 30 laminated on one side of the first electrode layer 20, a photoelectric conversion layer 40 laminated on one side of the hole transport layer 30, an electron transport layer 50 laminated on one side of the photoelectric conversion layer 40, and a second electrode layer 60 (cathode) laminated on one side of the electron transport layer 50. A passivation material (not shown) may be present on the surface and / or inside the photoelectric conversion layer 40.

[0022] The substrate 10 is a structure that supports other layers and ensures the strength of the perovskite solar cell 1. When the perovskite solar cell 1 receives light from the side of the substrate 10, the substrate 10 is formed from a transparent material. Specifically, if the strength of the solar cell 1 is important, the substrate 10 is preferably made of glass, and if the lightness and flexibility of the solar cell 1 are important, the substrate 10 is preferably made of resin. As the resin material for the substrate 10, polyimide, polyamide, and polyethylene terephthalate are preferred. From the viewpoint of dimensional stability, polyimide is particularly preferred. When the cost of the product is important, polyethylene terephthalate is particularly preferred. Furthermore, when the perovskite solar cell 1 receives light from the side of the second electrode layer 60, the substrate 10 may be formed from a composite material including a metal layer or the like.

[0023] The first electrode layer 20 collects holes generated in the photoelectric conversion layer 40 through the hole transport layer 30 and outputs them to the outside. The first electrode layer 20 can be formed from a transparent conductive oxide (TCO) that is conductive and light-transmitting. Examples of transparent conductive oxides that can be used to form the first electrode layer 20 include indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof. Among these, indium-based composite oxides mainly composed of indium oxide, zinc oxide, tungsten oxide, molybdenum oxide, etc., or fluorine-doped tin oxide are preferred. Indium oxide is particularly preferred from the viewpoint of high conductivity and transparency. To improve the moldability of the hole transport layer 30, the first electrode layer 20 is preferably subjected to a surface treatment such as ozone treatment, and may have a multilayer structure on its surface having a layer of p-type oxide semiconductor mainly composed of, for example, nickel oxide, niobium oxide, etc.

[0024] The hole transport layer 30 effectively transfers holes generated in the photoelectric conversion layer 40 to the first electrode layer 20. The hole transport layer 30 is a self-assembled monolayer containing a hole transport material having bonding groups that exert an attractive interaction with the first electrode layer or are capable of forming bonds with the first electrode layer.

[0025] The hole transport material is preferably a compound with a small difference between the HOMO (Highest Occupied Molecular Orbital) of the hole transport material and the VB edge (Valence Band) of the perovskite compound constituting the photoelectric conversion layer 40. The above difference is preferably 0.00 to 1.00 eV, more preferably 0.00 to 0.50 eV, and even more preferably 0.00 to 0.30 eV. HOMO and LUMO can be determined from photoelectron spectroscopy or quantum chemical calculations based on density functional theory. As the exchange-correlation functional, B3LYP can be suitably used. For basis sets, 6-311G(d) can be suitably used for optimizing molecular structure, and 6-311++G(d,p) can be suitably used for energy calculation.

[0026] Hole transport materials are compounds having atomic groups involved in hole transport and the aforementioned bonding groups. Examples of atomic groups involved in hole transport include aromatic compounds containing a triphenylamine skeleton, such as Spiro-MeOTAD (CAS number: 207739-72-8), TOP-HTM-α1 (CAS number: 872466-50-7), and TOP-HTM-α2 (CAS number: 2411528-61-3); aromatic compounds containing a carbazole skeleton, such as 2PACz (CAS number: 20999-38-6), 4PACz (CAS number: 20999-36-4), MeO-2PACz (CAS number: 2922526-56-3), and Me-2PACz (CAS number: 2747959-96-0); compounds containing a phenothiazine skeleton; compounds containing a thiophene skeleton; and compounds containing a diarylamine skeleton.

[0027] The hole transport material includes a single-legged hole transport material (i) having one bonding group and a multi-legged hole transport material (ii) having two or more bonding groups. The hole transport material may include one single-legged hole transport material (i) or a combination of two or more types. The hole transport material may include one or more types of multi-legged hole transport material (ii).

[0028] The bonding group is the group represented by the following formula (A). -R 1 -R 2 ...(A) R 1 R is a divalent organic group having 1 to 12 carbon atoms. 2 However, these are phosphonic acid groups, carboxyl groups, sulfonic acid groups, boric acid groups, hydroxyl groups, amino groups, silyl groups, or mercapto groups.

[0029] R 1 A divalent organic group may contain heteroatoms in addition to carbon and hydrogen atoms. Examples of heteroatoms include O, N, S, halogen atoms, P, B, and Si.

[0030] R 1 The divalent organic group is preferably a hydrocarbon group. The number of carbon atoms in the hydrocarbon group is not particularly limited, but is preferably 1 to 12, and more preferably 1 to 6. R 1 The hydrocarbon group can be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group. If the hydrocarbon group is an aliphatic hydrocarbon group, the structure of the aliphatic hydrocarbon group may be linear, cyclic, or a combination of linear and cyclic.

[0031] R 1 Suitable examples of aliphatic hydrocarbon groups include methylene group, ethane-1,2-diyl group (ethylene group), ethane-1,1-diyl group, propane-1,3-diyl group (propylene group), propane-1,2-diyl group (butylene group), propane-2,2-diyl group, butane-1,4-diyl group, butane-1,3-diyl group, butane-1,2-diyl group, pentane-1,5-diyl group, and hexane-1,6-diyl group. Among these groups, methylene group, ethane-1,2-diyl group (ethylene group), propane-1,3-diyl group (propylene group), butane-1,4-diyl group, and butane-1,3-diyl group (butylene group) are preferred, and ethane-1,2-diyl group (ethylene group), propane-1,3-diyl group (propylene group), and butane-1,3-diyl group (butylene group) are more preferred.

[0032] R 1Suitable examples of aliphatic hydrocarbon groups include p-phenylene group, m-phenylene group, naphthalene-2,6-diyl group, naphthalene-2,7-diyl group, naphthalene-1,4-diyl group, naphthalene-1,5-diyl group, naphthalene-1,7-diyl group, biphenyl-4,4'-diyl group, biphenyl-3,4'-diyl group, and biphenyl-3,3'-diyl group.

[0033] R 2 These are phosphonic acid groups, carboxyl groups, sulfonic acid groups, boric acid groups, hydroxyl groups, amino groups, silyl groups, or mercapto groups. Silyl groups are typically reactive silicon groups that can produce silanol groups by hydrolysis. Such reactive silicon groups have hydrolyzable groups bonded to silicon atoms.

[0034] Specific examples of hydrolyzable groups include halogen atoms, alkoxy groups, acyloxy groups, ketoximate groups, amino groups, amide groups, acid amide groups, aminooxy groups, mercapto groups, and alkenyloxy groups. Among these, alkoxy groups, acyloxy groups, ketoximate groups, and alkenyloxy groups are preferred, and alkoxy groups such as methoxy groups and ethoxy groups are more preferred because they are mildly hydrolyzable and easy to handle.

[0035] Specific examples of reactive silicon groups include dimethoxymethylsilyl group, diethoxymethylsilyl group, trimethoxysilyl group, triethoxysilyl group, dimethoxyphenylsilyl group, methoxymethyldimethoxysilyl group, methoxymethyldiethoxysilyl group, triisopropenyloxysilyl group, and triacetoxysilyl group. Among these, dimethoxymethylsilyl group, trimethoxysilyl group, and methoxymethyldimethoxysilyl group are preferred.

[0036] Since hole transport materials are readily available and easy to prepare, and the hole transport layer 30 is easily formed, in formula (A), R 1 However, it is an alkylene group with 1 to 6 carbon atoms, R 2 It is preferable that the group is a phosphonic acid group.

[0037] As mentioned above, hole transport materials are compounds that have atomic groups involved in hole transport and the bonding groups described above. Therefore, the single-legged hole transport material (i) is a compound represented by the following formula (Ai). HTG-R 1 -R 2 ...(Ai) HTG is a group formed by removing one hydrogen atom from an atomic group involved in hole transport. 1 , and R 2 R in equation (A) 1 , and R 2 It is similar to that. The multi-legged hole transport material (ii) is a compound represented by the following formula (Aii). HTG(-R 1 -R 2 )n···(ii) HTG is a group obtained by removing n hydrogen atoms from an atomic group involved in hole transport. n is an integer greater than or equal to 2, preferably an integer between 2 and 10. 1 , and R 2 R in equation (A) 1 , and R 2 It is similar to that. -R 1 -R 2 The bonding group represented by may be bonded to carbon atoms constituting HTG, or to heteroatoms such as nitrogen atoms.

[0038] The self-assembled monolayer as the hole transport layer 30 is thought to be able to cover the surface of the first electrode layer 20 while reducing minute voids in the self-assembled monolayer by including both a single-legged hole transport material and a multi-legged hole transport material. If the minute voids in the self-assembled monolayer covering the surface of the first electrode layer 20 are reduced, the photoelectric conversion efficiency of the perovskite solar cell 1 will increase.

[0039] The single-legged hole transport material (i) is preferably a nitrogen-containing aromatic compound having a structure in which a benzene ring and a hydrocarbon ring having a π-conjugated system are bonded via a nitrogen atom, wherein one hydrogen atom is substituted with the above-mentioned bonding group, and more preferably a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom, wherein one hydrogen atom is substituted with the above-mentioned bonding group. For example, a structure in which two naphthalene rings are bonded via a nitrogen atom includes a structure in which two benzene rings are bonded via a nitrogen atom. The ring having a π-conjugated system may be a benzene ring, or it may be an unsaturated hydrocarbon ring having a π-conjugated system and not exhibiting aromaticity. Examples of unsaturated hydrocarbon rings having a π-conjugated system and not exhibiting aromaticity include cyclooctatetraene rings. The multi-legged hole transport material (ii) is preferably a nitrogen-containing aromatic compound having a structure in which a benzene ring and a hydrocarbon ring having a π-conjugated system are bonded via a nitrogen atom, wherein two or more hydrogen atoms are substituted with the above-mentioned bonding group, and more preferably a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom, wherein two or more hydrogen atoms are substituted with bonding group.

[0040] Typical examples of nitrogen-containing aromatic compounds having a structure in which two benzene rings are bonded via a nitrogen atom include diphenylamine, triphenylamine, and 9H-carbazole.

[0041] When the single-legged hole transport material (i) and the multi-legged hole transport material (ii) are the nitrogen-containing aromatic compounds substituted with the aforementioned bonding mechanism, the nitrogen-containing aromatic compounds are preferably one or more compounds selected from the compounds represented by the following formulas (A1) to (A7), and more preferably compounds represented by the following formulas (A1) to (A3). [ka]

[0042] In equations (A1) to (A7), R 3 Each of these groups is independently selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and halogen atoms. n1, n2, n4, n5, n6, n7, n8, n10, n11, n13, n14, n16, n17, n18, n19, n20, and n21 are independently integers between 0 and 4, and n3, n9, n12, and n15 are integers between 0 and 2.

[0043] R 3 Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl groups. R 3 Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propyloxy, isopropyloxy, n-butyloxy, isobutyloxy, sec-butyloxy, tert-butyloxy, n-pentyloxy, and n-hexyloxy groups. R 3 Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0044] The single-legged hole transport material is preferably one or more compounds represented by the following formula (A1-1). The multi-legged hole transport material is preferably one or more compounds selected from the compounds represented by the following formulas (A2-1) to (A7-1). [ka]

[0045] It is expressed by equation (A1-1), R 1 is a divalent aliphatic hydrocarbon group, R 2Suitable examples of monolegged hole transport materials whose base is a phosphonic acid group include N-(2-phosphonoethyl)carbazole (2PACz), N-(2-phosphonoethyl)-3,6-dimethoxycarbazole (MeO-2PACz), N-(2-phosphonoethyl)-3,6-dimethylcarbazole (Me-2PACz), N-(3-phosphonopropyl)carbazole (3PACz), N-(3-phosphonopropyl)-3,6-dimethoxycarbazole (MeO-3PACz), N-(3-phosphonopropyl)-3,6-dimethylcarbazole (Me-3PACz), N-(4-phosphonobutyl)carbazole (4PACz), N-(4-phosphonobutyl)-3,6-dimethoxycarbazole (MeO-4PACz), and N-(4-phosphonobutyl)-3,6-dimethylcarbazole (Me-4PACz). Among these, 2PACz, MeO-2PACz, Me-2PACz, MeO-4PACz, and Me-4PACz are more preferred.

[0046] It is expressed by equation (A1-1), R 1 is a divalent aromatic hydrocarbon group, R 2 A suitable specific example of a single-legged hole transport material in which the group is a phosphonic acid group is: N-(4-phosphonophenyl)-9H-carbazole, N-(3-phosphonophenyl)-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-9H-carbazole, N-(4-phosphonophenyl)-3-methyl-9H-carbazole, N-(4-phosphonophenyl)-3-ethyl-9H-carbazole, N-(4-phosphonophenyl)-3-fluoro-9H-carbazole, N-(4-phosphonophenyl)-3-chloro-9H-carbazole, N-(4-phosphonophenyl)-3-bromo-9H-carbazole, N-(4-phosphonophenyl)-3-iodo-9H-carbazole, N-(4-phosphonophenyl)-3,6-dimethyl-9H-carbazole, N-(4-phosphonophenyl)-3,6-diethyl-9H-carbazole, N-(4-phosphonophenyl)-3,6-difluoro-9H-carbazole, N-(4-phosphonophenyl)-3,6-dichloro-9H-carbazole, N-(4-phosphonophenyl)-3,6-dibromo-9H-carbazole, N-(4-phosphonophenyl)-3,6-diiodo-9H-carbazole, N-(4-phosphonophenyl)-2-methyl-9H-carbazole, N-(4-phosphonophenyl)-2-ethyl-9H-carbazole, N-(4-phosphonophenyl)-2-fluoro-9H-carbazole, N-(4-phosphonophenyl)-2-chloro-9H-carbazole, N-(4-phosphonophenyl)-2-bromo-9H-carbazole, N-(4-phosphonophenyl)-2,7-dimethyl-9H-carbazole, N-(4-phosphonophenyl)-2,7-diethyl-9H-carbazole, N-(4-phosphonophenyl)-2,7-difluoro-9H-carbazole, N-(4-phosphonophenyl)-2,7-dichloro-9H-carbazole, N-(4-phosphonophenyl)-2,7-dibromo-9H-carbazole, N-(4-phosphonophenyl)-2,7-diiodo-9H-carbazole, N-(3-phosphonophenyl)-3-methyl-9H-carbazole, N-(3-phosphonophenyl)-3-ethyl-9H-carbazole, N-(3-phosphonophenyl)-3-fluoro-9H-carbazole, N-(3-phosphonophenyl)-3-chloro-9H-carbazole, N-(3-phosphonophenyl)-3-bromo-9H-carbazole, N-(3-phosphonophenyl)-3-iodo-9H-carbazole, N-(3-phosphonophenyl)-3,6-dimethyl-9H-carbazole, N-(3-phosphonophenyl)-3,6-diethyl-9H-carbazole, N-(3-phosphonophenyl)-3,6-difluoro-9H-carbazole, N-(3-phosphonophenyl)-3,6-dichloro-9H-carbazole, N-(3-phosphonophenyl)-3,6-dibromo-9H-carbazole, N-(3-phosphonophenyl)-3,6-diiodo-9H-carbazole, N-(3-phosphonophenyl)-2-methyl-9H-carbazole, N-(3-phosphonophenyl)-2-ethyl-9H-carbazole, N-(3-phosphonophenyl)-2-fluoro-9H-carbazole, N-(3-phosphonophenyl)-2-chloro-9H-carbazole, N-(3-phosphonophenyl)-2-bromo-9H-carbazole, N-(3-phosphonophenyl)-2,7-dimethyl-9H-carbazole, N-(3-phosphonophenyl)-2,7-diethyl-9H-carbazole, N-(3-phosphonophenyl)-2,7-difluoro-9H-carbazole, N-(3-phosphonophenyl)-2,7-dichloro-9H-carbazole, N-(3-phosphonophenyl)-2,7-dibromo-9H-carbazole, N-(3-phosphonophenyl)-2,7-diiodo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-methyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-ethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-fluoro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-chloro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-bromo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3-iodo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-dimethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-diethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-difluoro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-dichloro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-dibromo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-3,6-diiodo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-methyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-ethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-fluoro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-chloro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-bromo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2-iodo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-dimethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-diethyl-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-difluoro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-dichloro-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-dibromo-9H-carbazole, N-[4-(4-phosphonophenyl)phenyl]-2,7-diiodo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-methyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-ethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-fluoro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-chloro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-bromo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3-iodo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-dimethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-diethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-difluoro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-dichloro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-dibromo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-3,6-diiodo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-methyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-ethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-fluoro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-chloro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-bromo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2-iodo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-dimethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-diethyl-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-difluoro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-dichloro-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-dibromo-9H-carbazole, N-[3-(4-phosphonophenyl)phenyl]-2,7-diiodo-9H-carbazole N-[4-(3-phosphonophenyl)phenyl]-3-methyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3-ethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3-fluoro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3-chloro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3-bromo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3-iodo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-dimethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-diethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-difluoro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-dichloro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-dibromo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-3,6-diiodo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-methyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-ethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-fluoro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-chloro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-bromo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2-iodo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-dimethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-diethyl-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-difluoro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-dichloro-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-dibromo-9H-carbazole, N-[4-(3-phosphonophenyl)phenyl]-2,7-diiodo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-methyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-ethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-fluoro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-chloro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-bromo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3-iodo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-dimethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-diethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-difluoro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-dichloro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-dibromo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-3,6-diiodo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-methyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-ethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-fluoro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-chloro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-bromo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2-iodo-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2,7-dimethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2,7-diethyl-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2,7-difluoro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2,7-dichloro-9H-carbazole, N-[3-(3-phosphonophenyl)phenyl]-2,7-dibromo-9H-carbazole, and N-[3-(3-phosphonophenyl)phenyl]-2,7-diiodo-9H-carbazole, These are some examples.

[0047] It is expressed by equation (A2-1), R 2 The following compounds are suitable examples of multi-legged hole transport materials in which the group is a phosphonic acid group. [ka]

[0048] It is expressed by equation (A3-1), R 2 The following compounds are suitable examples of multi-legged hole transport materials in which the group is a phosphonic acid group. [ka]

[0049] [ka]

[0050] The ratio of the mass of the single-legged hole transport material to the total mass of the multi-legged hole transport material is preferably 5% by mass or more and 50% by mass or less. The ratio of the mass of the single-legged hole transport material to the total mass of the multi-legged hole transport material may be 10% by mass or more and 45% by mass or less, and 15% by mass or more and 40% by mass or less.

[0051] The hole transport layer 30 may contain, in addition to the single-legged hole transport material and the multi-legged hole transport material, other phosphonic acid compounds such as n-butylphosphonic acid, n-pentylphosphonic acid, n-hexylphosphonic acid, n-octylphosphonic acid, n-decylphosphonic acid, n-octadecylphosphonic acid, 2-ethylhexylphosphonic acid, methoxymethylphosphonic acid, 3-acryloyloxypropylphosphonic acid, 11-hydroxyundecylphosphonic acid, 1H,1H,2H,2H-perfluorophosphonic acid, acetic acid, propionic acid, isobutyric acid, nonanoic acid, fluoroacetic acid, α-chloropropionic acid, and glyoxylic acid. These compounds are not considered hole transport materials. They may be used individually or in combination of two or more.

[0052] The hole transport layer 30 can be formed by coating and drying a liquid composition containing the aforementioned single-legged hole transport material and multi-legged hole transport material. The liquid composition may contain the aforementioned other compounds along with the single-legged hole transport material and multi-legged hole transport material represented by formula (1).

[0053] The liquid composition used to form the hole transport layer 30 typically contains an organic solvent. Examples of organic solvents include alcohols such as methanol, ethanol, 2-methoxyethanol, isopropanol, and butanol; ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, 4-methyltetrahydropyran, 2-methyltetrahydrofuran, and cyclopentyl methyl ether; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); esters such as ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isoamyl acetate, and γ-butyrolactone (GBL); nitriles such as acetonitrile, propionitrile, and 3-methoxypropionitrile; aromatic compounds such as benzene, toluene, chlorobenzene, and nitrobenzene; chlorinated hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; and fluorinated hydrocarbons such as chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons. These can be used individually or in combination of two or more.

[0054] The total concentration of the materials constituting the self-assembled monolayer contained in the liquid composition is preferably 5.0 mg / mL or less.

[0055] Furthermore, the above liquid composition may contain a perovskite precursor, described later, which is used to form the photoelectric conversion layer 40. When using a liquid composition containing a perovskite precursor, the hole transport layer 30 and the photoelectric conversion layer 40 can be formed simultaneously by coating the liquid composition onto the first electrode layer 20, drying it, and crystallizing the perovskite precursor. In this case, during the process of forming the photoelectric conversion layer 40, compounds such as hole transport materials contained in the liquid composition form a self-assembled monolayer on the first electrode layer 20.

[0056] It is also preferable that a passivation material be present between the hole transport layer 30 and the photoelectric conversion layer 40. The passivation material between the hole transport layer 30 and the photoelectric conversion layer 40 is not shown in Figure 1.

[0057] The passivation material is an organic compound that suppresses defects in the photoelectric conversion layer 40 by interacting with anionic and cationic species on the surface and / or inside the photoelectric conversion layer 40. By passivating the defects in the photoelectric conversion layer 40, the recombination of charge and holes is suppressed, and the photoelectric conversion efficiency is improved.

[0058] The passivation material may exist as a layer of a certain thickness on the surface of the photoelectric conversion layer 40, or it may exist as a single molecule or a composite of multiple molecules inside the photoelectric conversion layer 40 (for example, inside the perovskite crystal bulk or at the grain boundaries). The mode of presence of the passivation material in the photoelectric conversion layer 40 may be any of the above modes. In any of the above modes, the photoelectric conversion efficiency of the perovskite solar cell 1 is improved.

[0059] When the passivation material is present as a layer on the surface of the photoelectric conversion layer 40, the surface of the photoelectric conversion layer 40 is passivated by applying the passivation material to the interface between the hole transport layer 30 and the photoelectric conversion layer 40, and / or the interface between the electron transport layer 50 and the photoelectric conversion layer 40. In this case, the layer made of passivation material may be present in at least a part of the main surface of the photoelectric conversion layer 40, or it may be present throughout the entire surface, and it is preferable that it is present throughout the entire main surface of the photoelectric conversion layer 40.

[0060] When the passivation material exists within the photoelectric conversion layer 40 as a single molecule or a composite of multiple molecules, the interaction between the passivation material (as a single molecule or composite of multiple molecules) and the perovskite crystal causes the defects within the photoelectric conversion layer 40 to be passivated. In this case, typically, the passivation material acts on the crystal lattice of the perovskite compound within the photoelectric conversion layer 40, causing the grain boundaries and the like to be passivated.

[0061] The passivation material is not particularly limited as long as the desired effect is not impaired. The passivation material can be appropriately selected from various compounds that have been conventionally used to form the passivation layer in perovskite solar cells. Suitable examples of passivation materials include various amines or their hydrohalides. Examples of hydrohalides include hydrofluoric acid, hydrochloride, hydrobromide, and hydroiodide, with hydrobromide and hydroiodide being preferred, and hydroiodide being more preferred.

[0062] Suitable examples of passivation materials include n-butylamine hydrobromide, n-butylamine hydroiodide, n-hexylamine hydrobromide, n-hexylamine hydroiodide, n-decylamine hydrobromide, n-octadecylamine hydroiodide, pyridine hydrobromide, aniline hydroiodide, hydrazine dibromide, ethylenediamine hydroiodide, phenethylamine hydroiodide, 4-fluorinated phenethylamine hydroiodide, phenylenediamine dihydrochloride, diphenylamine hydrobromide, diphenylamine hydroiodide, benzylamine hydroiodide, and 4-diphenylaminophenethylamine hydroiodide.

[0063] Fluorine-containing amine compounds and their salts are also preferred as passivation materials. Suitable specific examples of fluorine-containing amine compounds include, for example, compounds having a fluorinated aromatic group and an amino acid group, such as pentafluorophenylethylalanine hydroiodide, and their salts; fluoroalkylamines such as 6,6,6,5,5,4,4,3,3,2,2-undekafluoropentylamine hydroiodide and 5,5,5,4,4,3,3,2,2-nonafluoropentylamine hydroiodide, and their salts; and compounds having a fluorinated aromatic group and an amino group, such as 4-fluorophenylethylamine hydroiodide, and their salts.

[0064] As a passivation material, hydrohalides represented by the following formula (01) are also preferred. R 01 R 022 NC(=NH)-NH-C(=NH)-NH 2 ·HX···(01) (In formula (01), R 01 , and R 02 Each of these is independently a hydrogen atom or a monovalent organic group, and X is a halogen atom.

[0065] In formula (01), R 01 , and R 02 Each of these is independently either a hydrogen atom or a monovalent organic group. Examples of monovalent organic groups include optionally substituted alkyl groups, optionally substituted aromatic hydrocarbon groups, optionally substituted heterocyclic groups, aliphatic acyl groups, and aromatic acyl groups. Examples of substituents that the alkyl group may have include alkoxy groups having 1 to 6 carbon atoms, halogen atoms, nitro groups, and cyano groups. Examples of substituents that aromatic hydrocarbon groups and heterocyclic groups may have include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, aliphatic acyl groups having 2 to 6 carbon atoms, aliphatic acyloxy groups having 2 to 6 carbon atoms, halogen atoms, nitro groups, and cyano groups.

[0066] Specific examples of substituents include alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl; alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, n-propyloxy, isopropyloxy, n-butyloxy, isobutyloxy, sec-butyloxy, tert-butyloxy, n-pentyloxy, and n-hexyloxy; aliphatic acyl groups having 2 to 6 carbon atoms, such as acetyl, propionyl, butanoyl, pentanoyl, and hexanoyl; aliphatic acyloxy groups having 2 to 6 carbon atoms, such as acetyloxy, propionyloxy, butanoyloxy, pentanoyloxy, and hexanoyloxy; halogen atoms such as fluorine, chlorine, bromine, and iodine; nitro; cyano; and the like.

[0067] R 01 , and R 02 Preferably, the monovalent organic group is an alkyl group which may have substituents, and preferably an aromatic hydrocarbon group which may have substituents, with preferably an aromatic hydrocarbon group which may have substituents.

[0068] Preferred examples of aromatic hydrocarbon groups that may have substituents include: phenyl groups; naphthyl groups such as naphthalen-1-yl and naphthalen-2-yl; methylphenyl groups such as 2-methylphenyl, 3-methylphenyl, and 4-methylphenyl; dimethylphenyl groups such as 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl, and 3,5-dimethylphenyl; methoxyphenyl groups such as 2-methoxyphenyl, 3-methoxyphenyl, and 4-methoxyphenyl; 2,3-dimethoxyphenyl, 2,4-dimethoxyphenyl, 2,5-dimethoxyphenyl, 2,6-dimethoxyphenyl, and 3,4-dimethoxyphenyl. Examples include dimethoxyphenyl groups such as xyphenyl groups and 3,5-dimethoxyphenyl groups; chlorophenyl groups such as 2-chlorophenyl groups, 3-chlorophenyl groups, and 4-chlorophenyl groups; dichlorophenyl groups such as 2,3-dichlorophenyl groups, 2,4-dichlorophenyl groups, 2,5-dichlorophenyl groups, 2,6-dichlorophenyl groups, 3,4-dichlorophenyl groups, and 3,5-dichlorophenyl groups; bromophenyl groups such as 2-bromophenyl groups, 3-bromophenyl groups, and 4-bromophenyl groups; and subbromophenyl groups such as 2,3-dibromophenyl groups, 2,4-dibromophenyl groups, 2,5-dibromophenyl groups, 2,6-dibromophenyl groups, 3,4-dibromophenyl groups, and 3,5-dibromophenyl groups.

[0069] Among these groups, phenyl groups; naphthyl groups such as naphthalen-1-yl and naphthalen-2-yl groups; and methylphenyl groups such as 2-methylphenyl, 3-methylphenyl, and 4-methylphenyl groups are preferred, with phenyl groups, 2-methylphenyl groups, 3-methylphenyl groups, and 4-methylphenyl groups being more preferred.

[0070] In equation (01), R 01 , and R 02 Preferably, one of these is an aromatic hydrocarbon group which may have substituents, and the other is a hydrogen atom.

[0071] Hydrohalides represented by formula (01) are given by the following formula (01-1): R 01 R 02 NC(=NH)-NH-C(=NH)-NH 2 ...(01-1) (In formula (01-1), R 1 , and R 2 R in equation (1) 01 , and R 02 It is similar to this. It is a salt of a biguanide compound represented by and a hydrohalic acid represented by HX.

[0072] Examples of hydrohalides represented by HX include hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid, with hydrobromic acid and hydroiodic acid being preferred, and hydroiodic acid being more preferred.

[0073] A suitable example of a hydrohalide salt represented by formula (01) is H2N-C(=NH)-NH-C(=NH)-NH 2 ·HI, Me-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, Et-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, Ph-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, o-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, m-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, p-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, (Me)2N-C(=NH)-NH-C(=NH)-NH 2 ·HI, (Et)2N-C(=NH)-NH-C(=NH)-NH 2 ·HI, (Ph)2N-C(=NH)-NH-C(=NH)-NH 2 ·HI, (o-Tol)2N-C(=NH)-NH-C(=NH)-NH 2 ·HI, (m-Tol)2N-C(=NH)-NH-C(=NH)-NH 2·HI, and (p-Tol)2N-C(=NH)-NH-C(=NH)-NH 2 ·HI is included.

[0074] In the above formula, Ph is a phenyl group. Me is a methyl group. Et is an ethyl group. o-Tol is an o-tolyl group (2-methylphenyl group). m-Tol is an m-tolyl group (3-methylphenyl group). p-Tol is a p-tolyl group (4-methylphenyl group).

[0075] Among these compounds, Me-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, Et-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, Ph-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, o-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, m-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, and p-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI is preferred, and Ph-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, o-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, m-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, and p-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI is more preferred, and Ph-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI, and o-Tol-NH-C(=NH)-NH-C(=NH)-NH 2 ·HI is particularly preferred.

[0076] The method for producing the hydrohalide represented by formula (01) is not particularly limited. The hydrohalide represented by formula (1) can be obtained, for example, by mixing a solution or suspension containing the aforementioned biguanide compound with a solution of a hydrohalic acid represented by HX. The solvent or dispersion medium used to dissolve or suspend the biguanide compound is not particularly limited as long as it is a liquid that does not react with hydrohalic acid. As the solvent or dispersion medium, in addition to organic solvents similar to those that may be contained in the liquid composition used to form the hole transport layer 30, pure water can also be used. The hydrohalic acid solution may be an aqueous solution or an organic solvent solution.

[0077] Among these, from the viewpoint of availability and the balance between cost and performance, amine compounds containing an alkyl fluoride moiety and / or salts thereof, or compounds having a fluorinated aromatic group and an amino group are preferred, and salts of amine compounds containing an alkyl fluoride moiety are more preferred.

[0078] When a passivation material is present between the hole transport layer 30 and the photoelectric conversion layer 40, a thin film of the passivation material is formed by coating the hole transport layer 30 with a passivation material solution containing the passivation material and an organic solvent, and then drying it. The same solvent used for forming the hole transport layer 30 described above is preferably used as the organic solvent. The coating method is not particularly limited. Coating can be performed using, for example, a spin coater, die coater, or bar coater. The temperature during application is not particularly limited, but -20°C to 200°C is preferred, and 0°C to 150°C is more preferred. The application time is not particularly limited, but 1 second to 24 hours is preferred, and 5 seconds to 1 hour is more preferred.

[0079] Furthermore, by including a passivation material in the aforementioned liquid composition, a layer made of the passivation material can be formed on the surface of the hole transport layer 30.

[0080] The photoelectric conversion layer 40 contains a perovskite compound that performs photoelectric conversion and absorbs incident light to generate photocarriers. The perovskite compound contained in the photoelectric conversion layer 40 is not particularly limited as long as the desired effect is not impaired, and can be appropriately selected from well-known compounds. As a preferred example, the perovskite compound can be a compound represented by ABX3, which contains an organic atomic group A containing at least one of a monovalent organic ammonium ion and an amidinium-based ion, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of iodide ion I, bromide ion Br, chloride ion Cl, and fluoride ion F. The organic atomic group A is not particularly limited as long as the desired effect is not impaired, and can be appropriately selected from well-known organic compounds. Examples of organic atomic group A include methylammonium MA (CH3NH3) and formamidinium FA (CH3N2).

[0081] The metal atom B is not particularly limited as long as it is a metal atom that has been conventionally used in the formation of perovskite compounds. Preferred metal atoms B include lead (Pb) and tin (Sn). When prioritizing the power generation efficiency of the perovskite solar cell 1, it is preferable that the metal atom B is mainly lead. The lower limit of the lead content in metal atom B is preferably 50% by weight, more preferably 80% by weight, and even more preferably 90% by weight, in order to achieve the desired performance. On the other hand, when prioritizing the environmental impact of lead, it is preferable that the metal atom B is mainly tin (Sn). The lower limit of the tin content in metal atom B is preferably 50% by weight, more preferably 80% by weight, and especially preferably 90% by weight, in order to achieve the desired performance.

[0082] The halogen atom is not particularly limited. As the halogen atom X, at least one of iodide I, bromide Br, and chloride Cl is preferable. Also, substituting part or all of the organic atomic group A with an alkali metal Am has been considered, and such a perovskite compound can also be used. The alkali metal Am is not particularly limited. Preferred alkali metals Am include potassium K, cesium Cs, rubidium Rb, etc. Among them, as the alkali metal Am, cesium Cs and rubidium Rb are preferable when emphasizing the durability and water resistance of the perovskite solar cell 1, and cesium Cs is particularly preferable from the viewpoints of cost and availability.

[0083] Specifically, preferred perovskite compounds include, for example, methylammonium lead halides (MAPbX3) such as MAPbI3, MAPbBr3, MAPbCl3, and formamidinium lead halides (FAPbX3) such as FAPbI3, FAPbBr3, FAPbCl3. Note that the halogen atom X may include multiple types, and FA containing both methylammonium and formamidinium as the organic atomic group A y MA 1-y PbX3 may also be used. Also, when an alkali metal Am is included, Am y FA z MA 1-y-z PbIX, Am y FA 1-y PbIX, etc. may be mentioned. Am may be a single type of Cs, Rb, K, or may include multiple types (where y and z are arbitrary positive integers).

[0084] When a passivation material is present between the photoelectric conversion layer 40 and the electron transport layer 50, recombination of optical carriers at the interface between the photoelectric conversion layer 40 and the electron transport layer 50 is prevented, and the arrival of electrons at the electron transport layer 50 is promoted.

[0085] As the passivation material present between the photoelectric conversion layer 40 and the electron transport layer 50, the same materials as those used for the passivation material present between the hole transport layer 30 and the photoelectric conversion layer 40 can be used. As the passivation material to be placed between the photoelectric conversion layer 40 and the electron transport layer 50, the above-mentioned amine hydrohalides, amines having alkyl fluoride, or hydrohalides thereof are preferred.

[0086] As mentioned above, the passivation material can be an amine compound rather than a hydrohalide, but it will still produce the desired effect. In this case, the amine compound interacts with lead ions and other elements that form the perovskite crystal through the lone pair of electrons on the nitrogen atom, thereby preventing charge recombination.

[0087] When a passivation material is present between the photoelectric conversion layer 40 and the electron transport layer 50, it can be formed by coating the photoelectric conversion layer 40 with a passivation material solution containing the passivation material and an organic solvent, and then drying it, similar to the passivation material present between the hole transport layer 30 and the photoelectric conversion layer 40.

[0088] When a passivation material is included in the perovskite precursor solution used to form the photoelectric conversion layer 40, the passivation material can be present on the surface and / or inside the photoelectric conversion layer 40 by coating the perovskite precursor solution onto the hole transport layer 30, drying it, and crystallizing the perovskite precursor.

[0089] Furthermore, the aforementioned liquid composition containing the material constituting the self-assembled monolayer may also contain a perovskite precursor for forming the photoelectric conversion layer 40 and a passivation material. In this case, by coating and drying the liquid composition on the first electrode layer 20 and crystallizing the perovskite precursor, the hole transport layer 30 and the photoelectric conversion layer 40 can be formed simultaneously, while the passivation material can be present on the surface and / or inside the photoelectric conversion layer 40.

[0090] When the perovskite precursor solution contains a passivation material and a perovskite precursor, fluorine-containing amine compounds and their salts are preferred as passivation materials because they are easily precipitated at the interface and surface of the perovskite polycrystal by utilizing the hydrophobic interaction of fluorine atoms. The fluorine content in the fluorine-containing amine compound is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, as the mass of fluorine atoms relative to the molecular weight of each compound. When the fluorine-containing amine compound and its salt contain fluorine atoms in the above ratios, the fluorine-containing amine compound is easily precipitated on the perovskite crystal surface by sufficient hydrophobic interaction.

[0091] The electron transport layer 50 effectively transmits electrons to the second electrode layer 60. The material constituting the electron transport layer 50 is not particularly limited as long as the desired effect is not impaired. The material constituting the electron transport layer 50 can be appropriately selected from various compounds that have been conventionally used to form electron transport layers in perovskite solar cells. The electron transport layer 50 is preferably formed from a material mainly composed of, for example, fullerene or naphthalenediimide. Examples of fullerenes include C60, C70, their hydrides, oxides, metal complexes, alkyl groups, etc., derivatives to which such as PCBM ([6,6]-Phenyl-C61-Butyric Acid Methyl Ester) can be found. Furthermore, a hole-blocking layer made of pasocuproine (BCP), lithium fluoride (LiF), magnesium fluoride (MgF2), tin oxide (SnO2), aluminum-doped zinc oxide (ZnO), or titanium oxide (TiO2) may be included between the electron transport layer 50 and the second electrode layer 60. The inorganic oxide layer may be doped with another metallic material. The material of the hole-blocking layer is not limited to these.

[0092] The second electrode layer 60 preferably includes a metal layer, such as copper, to reduce electrical resistance when the perovskite solar cell 1 receives light from the substrate 10 side. However, the metal constituting the metal layer is not limited to copper. Furthermore, when the perovskite solar cell 1 receives light from the second electrode layer 60 side, the second electrode layer 60 may be formed from a transparent conductive oxide.

[0093] The perovskite solar cell 1 having the above configuration is The aforementioned liquid composition is applied to a first electrode layer 20 formed on one main surface of a plate-shaped or sheet-shaped substrate 10 to form a hole transport layer 30. A photoelectric conversion layer 40 containing a perovskite compound is formed on the hole transport layer 30, Forming an electron transport layer 50 on the photoelectric conversion layer 40, It can be manufactured by a method that includes forming a second electrode layer 60 on the electron transport.

[0094] Specifically, the perovskite solar cell 1 can be manufactured by the embodiment of the solar cell manufacturing method shown in Figure 2. The solar cell manufacturing method of this embodiment comprises a first electrode layer formation step (step S11), a hole transport layer formation step (step S12), a precursor liquid coating step (step S13), a crystallization step (step S14), an electron transport layer formation step (step S15), and a second electrode layer formation step (step S16). The embodiment of the solar cell manufacturing method shown in Figure 2 may include a first passivation material coating step (step S01, not shown in Figure 2) between the hole transport layer formation step (step S12) and the precursor liquid coating step (step S13). Furthermore, if a precursor liquid that does not contain passivation material is used in the precursor liquid coating step (step S13), the embodiment of the solar cell manufacturing method shown in Figure 2 may include a second passivation material coating step (step S02, not shown in Figure 2).

[0095] In the first electrode layer formation step S11, a first electrode layer 20 is formed on the main surface of one side of the substrate 10. The first electrode layer 20 can be laminated using a vacuum deposition technique such as sputtering. In the first electrode layer step, it is preferable to modify the surface of the deposited first electrode layer 20 in order to promote the formation of the hole transport layer 30 in the next step. Specific methods for modifying the surface of the first electrode layer 20 include, for example, surface hydroxylation by ultraviolet-ozone treatment or ozonated water washing, deposition of oxides such as nickel oxide that facilitate the growth of self-assembled films using a vacuum deposition technique such as sputtering, deposition of oxide nanoparticles using a coating technique, and heat treatment to activate the surface and remove impurities to facilitate the growth of self-assembled films.

[0096] In step S12, the hole transport layer formation step, the hole transport layer 30 is laminated onto the first electrode layer 20. The hole transport layer 30 can be formed by coating a solution containing the material constituting the hole transport layer 30 and an organic solvent, and then drying. The drying temperature is preferably 50°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher. The drying time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. When drying is performed under the above conditions, the organic solvent is sufficiently removed from the coated film, making it easier to obtain the desired crystals in the subsequent step of forming the perovskite polycrystal.

[0097] After forming the hole transport layer 30 in step S12, a first passivation material coating step (step S01) may be performed as needed to coat the hole transport layer 30 with passivation material. In the first passivation material coating step (step S01), a passivation material solution containing passivation material and an organic solvent is coated onto the hole transport layer 30, and then the coated film is dried. In this case, the passivation material can be present on the hole transport layer 30.

[0098] The passivation material solution can be applied using, for example, a spin coater, die coater, and bar coater.

[0099] Furthermore, in step S12, the passivation material can also be present on the hole transport layer 30 by coating it with a liquid composition containing the material constituting the hole transport layer 30 and the passivation material to form the hole transport layer 30.

[0100] In step S13, the precursor liquid coating process, the perovskite precursor liquid is coated onto the laminate of the substrate 10, the first electrode layer 20, and the hole transport layer 30. If step S01 is performed, the perovskite precursor liquid is coated onto the passivation material that has been applied to the hole transport layer 30. The perovskite precursor liquid can be applied using, for example, a spin coater, die coater, and bar coater.

[0101] The perovskite precursor solution comprises an organic solvent and a perovskite precursor that forms a perovskite compound that performs photoelectric conversion. The perovskite precursor solution may also further contain a hydrochloride salt that promotes the growth of crystals of the perovskite compound.

[0102] The photoelectric conversion layer 40 may be formed using a liquid composition containing the material constituting the hole transport layer 30 and a perovskite precursor. In this case, step S12, in which the hole transport layer 30 is formed, can be omitted. This is because the hole transport layer 30 is formed during the process of forming the photoelectric conversion layer 40 in steps S13 and S14.

[0103] A passivation material may be further added to the liquid composition containing the material constituting the hole transport layer 30 and a perovskite precursor. When using a liquid composition containing the material constituting the hole transport layer 30, a perovskite precursor, and a passivation material, the photoelectric conversion layer 40 can be formed while the hole transport layer 30 is formed by steps S13 and S14, and the passivation material can be present on the surface and / or inside the photoelectric conversion layer 40.

[0104] The perovskite precursor liquid may contain a passivation material. In this case, during the process of forming the photoelectric conversion layer 40 by steps S13 and S14, the passivation material may be present on the surface and / or inside the photoelectric conversion layer 40.

[0105] The perovskite precursor contained in the perovskite precursor solution is as described above.

[0106] As organic solvents, for example, alcohols such as methanol, ethanol, and 2-methoxyethanol; amide solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); sulfoxides such as dimethyl sulfoxide (DMSO), diethyl sulfoxide, and dibutyl sulfoxide; esters such as ethyl acetate, butyl acetate, propyl acetate, isopropyl acetate, amyl acetate, and γ-valerolactone (GBL); and aprotic polar solvents such as acetonitrile and propionitrile can be used individually or as a mixture of several types, and other types of organic solvents may also be included. The boiling points of these organic solvents are preferably as low as possible because they need to be removed by distillation during the formation of perovskite crystals. Specifically, the boiling points at atmospheric pressure are preferably 300°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower. When using an organic solvent with such a boiling point, less of the organic solvent remains in the perovskite crystal, making it easier to manufacture a perovskite solar cell 1 with the desired performance. The concentration of the perovskite precursor solution is related to the conditions of the crystallization process. The solid content concentration of the perovskite precursor solution is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by weight or more. When the solid content concentration of the perovskite precursor solution is such that the organic solvent can be volatilized with less energy when forming the photoelectric conversion layer 40, the perovskite solar cell 1 can be manufactured at low cost while reducing the environmental impact.

[0107] As the perovskite precursor, a metal halide BX, a halogenated organic compound AX, and at least one alkali metal halide AmX are used in predetermined proportions. Lead halide is preferably used as the metal halide BX. Formamidine hydrohalide and methylamine hydrohalide are preferably used as the halogenated organic compound AX, and cesium iodide is preferably used as the alkali metal halide AmX. The molar concentration of metal atom B is preferably in excess of 0.5 mol% to 10 mol% relative to the sum of the molar concentration of the organic compound and the molar concentration of alkali metal Am. This makes it possible to expel other materials to the front and back interfaces of the perovskite precursor solution during the crystallization process, thereby suppressing a decrease in photoelectric conversion efficiency due to the retention of other materials within the perovskite crystal.

[0108] When the perovskite precursor solution contains a passivation material, the recombination of photocarriers (holes and electrons) at the interface of the photoelectric conversion layer 40 is suppressed by the action of the passivation material present on and / or inside the photoelectric conversion layer 40.

[0109] Hydrochloride salts promote the crystallization of perovskite compounds and increase the grain size of the perovskite crystals. This reduces the area of ​​grain boundaries in the photoelectric conversion layer 40, suppressing the decrease in photoelectric conversion efficiency due to impurities between the perovskite crystals. Examples of hydrochloride salts used include methylammonium hydrochloride (MACl), formamidinium hydrochloride (FACl), and methylenediaminium hydrochloride (MDACl2). The parts other than the hydrochloride salts are preferably smaller than the crystal lattice of the perovskite crystals and have amino groups. The concentration of hydrochloride salt in the perovskite precursor solution can be 1 mol% to 40 mol% relative to the molar concentration of the metal atom B ion of the perovskite compound.

[0110] In the crystallization step S14, the film of the perovskite precursor solution is dried (the solvent is evaporated) to generate crystals of the perovskite compound. This forms a photoelectric conversion layer 40 mainly composed of the perovskite compound. If the perovskite precursor solution contains a passivation material, a photoelectric conversion layer 40 is formed, and the passivation material can be present on and / or inside the photoelectric conversion layer 40. Methods to promote the formation of crystals of the perovskite compound in the film of the perovskite precursor solution include, for example, poor solvent quenching, vacuum quenching, gas quenching, and laser treatment. In the crystallization step S14, the dried film of the perovskite precursor solution may be further heated.

[0111] After forming the photoelectric conversion layer 40 in steps S13 and S14, a second passivation material coating step (step S02) may be performed as needed to provide the passivation material on the main surface of the photoelectric conversion layer 40 opposite to the hole transport layer 30. In the second passivation material coating step (step S02), a passivation material solution containing the passivation material and an organic solvent is coated onto the photoelectric conversion layer 40, and then the coating film is dried to provide the passivation material on the photoelectric conversion layer 40.

[0112] In step S15, the electron transport layer formation step, the electron transport layer 50 is formed by methods such as coating or vacuum deposition. A hole block layer may also be formed on the electron transport layer 50 by vacuum deposition or atomic deposition.

[0113] In the second electrode layer formation step S16, the second electrode layer 60 is formed by methods such as sputtering, vacuum deposition, plating, or coating, depending on the material being formed.

[0114] As described above, perovskite solar cells exhibit high photoelectric conversion efficiency.

[0115] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. The solar cell according to the present invention may have further functional layers, for example, in a perovskite solar cell, the electron transport layer may be omitted. Furthermore, the perovskite solar cell may be a tandem solar cell using a photoelectric converter such as a crystalline silicon solar cell as a substrate. [Examples]

[0116] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples.

[0117] [Examples 1, 2, and Comparative Examples 1-3] In Examples 1-3 and Comparative Example 1, N-(4-phosphonobutyl)-3,6-dimethoxycarbazole (MeO-4PACz) was used as the single-legged hole transport material (HTM1).

[0118] In Example 1 and Comparative Example 2, a compound with the following structure was used as the multi-legged hole transport material (HTM2). [ka]

[0119] In Example 2 and Comparative Example 3, a compound with the following structure was used as the multi-legged hole transport material (HTM3). [ka]

[0120] First, NiOx was deposited on the FTO layer of a commercially available glass / FTO substrate. The glass / FTO substrate is a substrate in which FTO, which constitutes the first electrode layer, is pre-laminated on a glass substrate. Next, a solution of the hole transport layer formation material, dissolved in ethanol at a concentration of 1.0 mg / mL, was spin-coated onto the NiOx layer. The materials used for hole transport layer formation were those listed in Table 1. The coated film formed by spin-coating was dried at 100°C for 10 minutes to form the hole transport layer. A solution of 4-fluorophenylethylamine hydroiodide dissolved in DMF at a concentration of 80 mM was spin-coated onto the hole transport layer. The coated film formed by spin-coating was dried at 100°C for 5 minutes to deposit the passivation material onto the hole transport layer. A perovskite precursor solution, prepared by dissolving a perovskite precursor in a mixed solvent of DMSO and DMF in a volume ratio of 1:4 at a total solids content of 3.2 M, was spin-coated onto a hole transport layer to which a passivation material was attached. As the perovskite precursor, a mixture of PbI2 (metal halide), FAI, and MABr (organic halogenated compound) in a molar ratio of 1:0.83:0.17 was used. A poor solvent was dropped onto a coating film formed by spin coating, and then heated at 120°C for 30 minutes to form a photoelectric conversion layer. Furthermore, a perovskite solar cell was obtained by depositing a 20 nm thick fullerene as an electron transport layer, then forming a 20 nm thick SnO2 thin film as a buffer layer by atomic deposition, and finally depositing copper to a thickness of 100 nm, thereby stacking a second electrode layer on top of the electron transport layer to which the passivation material was attached.

[0121] Table 1 shows the results of measuring the IV characteristics of the perovskite solar cells obtained in Example 1, Example 2, and Comparative Examples 1-3.

[0122] [Table 1]

[0123] Table 1 shows that the perovskite solar cells of claims 1 and 2, each comprising a hole transport layer containing a combination of the aforementioned single-legged hole transport material and multi-legged hole transport material, have superior photoelectric conversion efficiency compared to the perovskite solar cells of Comparative Examples 1 to 3, which contain only a single-legged hole transport material or only a multi-legged hole transport material. [Explanation of Symbols]

[0124] 1. Perovskite solar cells 10 Base material 20 1st electrode layer 30 Hole transport layer 40 Photoelectric conversion layer 50 Electron transport layer 60 Second electrode layer

Claims

1. The device comprises a first electrode layer, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode layer in this order. The hole transport layer is a self-assembled monolayer containing a hole transport material having bonding groups that exert an attractive interaction with the first electrode layer or that can form bonds with the first electrode layer. The hole transport material includes a single-legged hole transport material having one of the bonding groups and a multi-legged hole transport material having two or more of the bonding groups. The aforementioned bonding group is of the following formula (A): -R １ -R ２ ・・・(A) It is a base represented by, The aforementioned R １ However, it is a divalent organic group with 1 to 12 carbon atoms. The aforementioned R ２ A perovskite solar cell in which the group is a phosphonic acid group, carboxyl group, sulfonic acid group, boric acid group, hydroxyl group, amino group, silyl group, or mercapto group.

2. The single-legged hole transport material is a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom, wherein one hydrogen atom is substituted with the bonding group. The perovskite solar cell according to claim 1, wherein the multi-legged hole transport material is a nitrogen-containing aromatic compound having a structure in which two benzene rings are bonded via a nitrogen atom, and in which two or more hydrogen atoms are substituted with the bonding group.

3. The perovskite solar cell according to claim 2, wherein the nitrogen-containing aromatic compound is one or more compounds selected from the compounds represented by the following formulas (A1) to (A3). 【Chemistry 1】 (In equations (A1) to (A3), R ３ Each of these is independently an alkyl group having 1 to 6 carbon atoms, and / or an alkoxy group having 1 to 6 carbon atoms, and each of n1, n2, n4, n5, n6, n7, and n8 is independently an integer between 0 and 4, and n3 is an integer between 0 and 2.

4. The perovskite solar cell according to claim 3, wherein the single-legged hole transport material is one or more compounds represented by the following formula (A1-1), and the multi-legged hole transport material is one or more compounds selected from the compounds represented by the following formula (A2-1) and the compounds represented by the following formula (A3-1). 【Chemistry 2】 (In Formula (A1-1) to Formula (A3-1), R ３ , and n1 to n8 are the same as R ３ , and n1 to n8 in Formula (A1) to Formula (A3), and R １ , and R ２ are the same as R １ , and R ２ in Formula (A).)

5. The aforementioned R １ However, it is an alkylene group having 1 to 6 carbon atoms, and the R ２ A perovskite solar cell according to any one of claims 1 to 4, wherein is a phosphonic acid group.

6. The perovskite solar cell according to claim 5, wherein the ratio of the mass of the single-legged hole transport material to the sum of the mass of the single-legged hole transport material and the mass of the multi-legged hole transport material is 5% by mass or more and 50% by mass or less.

7. A liquid composition for forming a hole transport layer in perovskite solar cell formation, The material comprises a single-legged hole transport material having one of the aforementioned bonding groups, and a multi-legged hole transport material having two or more of the aforementioned bonding groups. The aforementioned bonding group is of the following formula (A): -R １ -R ２ ・・・(A) It is a base represented by, The aforementioned R １ However, it is a divalent organic group with 1 to 12 carbon atoms. The aforementioned R ２ A liquid composition in which the group is a phosphonic acid group, a carboxyl group, a sulfonic acid group, a boric acid group, a hydroxyl group, an amino group, a silyl group, or a mercapto group.

8. Furthermore, the liquid composition according to claim 7 comprises a perovskite precursor and / or a passivation material.

9. A hole transport layer is formed by coating a first electrode layer formed on one main surface of a plate-shaped or sheet-shaped substrate with the liquid composition described in claim 7, A photoelectric conversion layer containing a perovskite compound is formed on the hole transport layer, Forming an electron transport layer on the aforementioned photoelectric conversion layer, This includes forming a second electrode layer on the electron transport, A method for manufacturing perovskite solar cells.

10. The liquid composition comprises a perovskite precursor and a passivation material. A method for producing a perovskite sun according to claim 9, wherein the hole transport layer and the photoelectric conversion layer are formed in this order by coating the liquid composition onto the first electrode layer, and a passivation material is present on the surface and / or inside the photoelectric conversion layer.

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