Perovskite solar cell

Abstract

A perovskite solar cell 1 according to the present invention comprises a first electrode 20, an electron transport layer 30, a perovskite layer 40, a hole transport layer 50, and a second electrode 60, wherein the hole transport layer 50 includes a heteroaromatic compound represented by general formula (1). The perovskite solar cell 1 makes it possible to suppress a decrease in photoelectric conversion efficiency even when the perovskite solar cell is placed at a high environmental temperature.

Description

Perovskite solar cells Cross Reference

[0001] This application claims priority based on Japanese Patent Application No. 2024-116086 filed on July 19, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to perovskite solar cells.

[0003] In recent years, research and development of perovskite solar cells using perovskite crystals as photoelectric conversion materials has been progressing. Perovskite solar cells can be manufactured by applying, for example, spin coating, compounds having a perovskite crystal structure, and therefore may be able to be manufactured at a lower cost than existing silicon-based solar cells. Furthermore, because perovskite solar cells can be formed thinly, they are expected to realize flexible and lightweight solar cells. Meanwhile, various efforts are being made to improve the durability of perovskite solar cells.

[0004] Patent Document 1 describes a perovskite solar cell in which an organic solvent such as tert-butylpyridine (hereinafter, "tert-butylpyridine" may be abbreviated as "TBP") shown in the following formula (B1) is added to the hole transport layer in order to stabilize the solute (hole transport substance) contained in the hole transport layer.

[0005] Patent Document 2 describes a perovskite solar cell in which a pyridine derivative having a hydrocarbon group at the ortho position is added to the hole transport layer. It also describes that the photoelectric conversion efficiency of a perovskite solar cell having such a configuration does not decrease even after 1000 hours have passed since its fabrication.

[0006] JP 2023-101350 A JP 2018-056473 A

[0007] The perovskite solar cells described in Patent Documents 1 and 2 are recognized to be effective to a certain extent in suppressing a decrease in photoelectric conversion efficiency at room temperature. However, it is difficult to say that they are sufficiently effective in suppressing a decrease in photoelectric conversion efficiency when the perovskite solar cell is placed in a high environmental temperature, for example, 80°C or higher.

[0008] The present invention aims to solve these problems and to provide a perovskite solar cell that can suppress a decrease in photoelectric conversion efficiency even when the perovskite solar cell is placed in a high environmental temperature.

[0009] [1] The perovskite solar cell of this application example is a perovskite solar cell including a first electrode, a perovskite layer, a hole transport layer, and a second electrode, wherein the hole transport layer contains a heteroaromatic compound represented by the following general formula (1): (Ar １ is a heteroaryl group containing one or more nitrogen or sulfur atoms, and Y is —C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-, and Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group, and x is an integer of 1 to 3. １ is Y-Ar ２ may be substituted with a substituent different from

[0010] [2] In the perovskite solar cell of this application example, the heteroaromatic compound represented by the general formula (1) is １ It is preferable that the heteroaryl group represented by the formula (I) is a pyridine group.

[0011] [3] In the perovskite solar cell of this application example, the heteroaromatic compound represented by the general formula (1) is ｎ H ２ｎ -, n=0, and said Ar２ Preferably, the compound includes compounds in which is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group.

[0012] [4] In the perovskite solar cell of this application example, the heteroaromatic compound represented by general formula (1) preferably includes one or more compounds selected from 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine.

[0013] [5] In the perovskite solar cell of this application example, it is preferable that the hole transport layer further includes an additive, and the additive is LiTFSI and / or CoTFSI.

[0014] [6] In the perovskite solar cell of this application example, it is preferable that the hole transport layer includes a hole transport material, and that the hole transport material includes a hole transport material having a spirobifluorene skeleton.

[0015] In the perovskite solar cell of the present invention, the hole transport layer contains a heteroaromatic compound represented by the following general formula (1): (Ar １ is a heteroaryl group containing one or more nitrogen or sulfur atoms, and Y is —C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-, and Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group, and x is an integer of 1 to 3. １ is Y-Ar ２ may be substituted with a substituent different from

[0016] The mechanism by which the heteroaromatic compound represented by general formula (1) suppresses a decrease in photoelectric conversion efficiency when a perovskite solar cell is placed in a high environmental temperature has not been confirmed. However, for example, the following may be considered. That is, the heteroaromatic compound represented by general formula (1) may suppress a decrease in glass transition temperature when the hole transport material contained in the hole transport layer is placed in a high environmental temperature, thereby suppressing a decrease in photoelectric conversion efficiency.

[0017] According to the present invention, it is possible to provide a perovskite solar cell that can suppress a decrease in photoelectric conversion efficiency even when the perovskite solar cell is placed in a high environmental temperature.

[0018] FIG. 1 is a cross-sectional view schematically illustrating an example of a perovskite solar cell 1 according to an embodiment.

[0019] [Embodiments] A perovskite solar cell 1 according to the present invention will be described below. The embodiments described below do not limit the invention according to the claims. Furthermore, not all of the elements and combinations thereof described in the embodiments are necessarily essential to the present invention.

[0020] 1 is a cross-sectional schematic diagram shown to explain an example of a perovskite solar cell 1 according to an embodiment. The perovskite solar cell 1 includes a support substrate 10, a first electrode 20 stacked on the support substrate 10, an electron transport layer 30, a perovskite layer 40, a hole transport layer 50, and a second electrode 60.

[0021] The support substrate 10 supports the perovskite layer 40 and the like formed on the support substrate 10. There are no particular limitations on the material of the support substrate 10, and known materials can be used. Examples of materials for the support substrate 10 include glass and resin.

[0022] Other solar cells can also be used as the support substrate 10. An example of a solar cell using another solar cell as the support substrate is a perovskite / silicon tandem solar cell in which a perovskite solar cell is formed on a silicon solar cell as the support substrate.

[0023] The material of the first electrode 20 is not particularly limited, and known materials can be used. Examples of materials constituting the first electrode 20 include metals such as platinum, gold, silver, copper, molybdenum, aluminum, and chromium, carbon, and conductive metal oxides such as fluorine-doped tin oxide (FTO) and indium tin oxide (ITO). Among the above, it is preferable to use FTO and ITO, which are translucent, as the first electrode 20.

[0024] In addition, when the first electrode 20 is configured as a conductive substrate and serves the function of the support substrate 10, the support substrate 10 is not essential.

[0025] There are no particular limitations on the material of the electron transport layer 30, and known materials can be used. Examples of materials constituting the electron transport layer 30 include metal oxides (titanium dioxide, tin dioxide, zinc oxide), fullerene derivatives, and monomolecular films. The thickness of the electron transport layer 30 is preferably about 0.1 nm to 1000 nm, for example, from the viewpoint of effectively collecting electrons from the perovskite layer 40 thereon.

[0026] The electron transport layer 30 can be produced by a known film formation method depending on the type of material to be laminated. For example, when tin dioxide is used as the material for the electron transport layer 30, the layer can be produced by applying a colloidal solution of tin dioxide onto the first electrode 20, heating (100°C to 200°C), and drying. When titanium dioxide is used, the layer can be produced by sputtering, spray pyrolysis, or applying a titanium oxide paste. Known or commercially available tin dioxide colloidal solutions and titanium oxide pastes can be used.

[0027] A perovskite layer 40 is formed on the electron transport layer 30. The perovskite layer 40 functions as a photoelectric conversion layer. In the perovskite layer 40, electrons and holes are generated by light irradiation. The perovskite layer 40 is a compound represented by the general formula ABX ３(where A and B are cations, and X is an anion). Examples include RNH3PbX3, R(NH2)2PbX3, RNH3SnX3, R(NH2)2SnX3 (where R is an alkyl group having 1 to 10 carbon atoms), CsBX3, RbBX3, and KBX3. The perovskite layer contains a perovskite material represented by the general formula A ｎ B ｎ X ３ｎ＋１ , A ｎ－１ A'B ｎ X ３ｎ＋１ , A ｎ＋１ B ｎ X ３ｎ＋１ , A ｎ－１ A' ２ B ｎ X ３ｎ＋１ (where A, A', and B are cations, and X is an anion).

[0028] From the viewpoints of light absorption efficiency and exciton diffusion length, the film thickness of the perovskite layer 40 is preferably, for example, 100 nm to 2000 nm. The perovskite layer 40 can be formed by a known film formation method. For example, the perovskite layer 40 can be formed by dissolving the components that form the perovskite layer 40 in a solvent, applying the solution to a substrate, and drying the solution. The perovskite layer can also be formed in stages using a sequential deposition method. Alternatively, the perovskite layer 40 can be formed by using a vapor deposition method. Furthermore, the perovskite layer 40 can be formed by applying a precursor of the perovskite layer 40 and then applying a poor solvent such as chlorobenzene or toluene to precipitate perovskite crystals.

[0029] Examples of solvents that can be preferably used include esters such as γ-butyl lactone, methyl formate, and ethyl acetate; ketones such as acetone and dimethyl ketones; ethers such as diethyl ether and diisopropyl ether; alcohols such as methanol, ethanol, isopropanol, and 2-methoxyethanol; halogenated hydrocarbons such as ethylene chloride and chloroform; nitrile solvents such as acetonitrile and propionitrile; N,N-dimethylformamide, and dimethyl sulfoxide.

[0030] The hole transport layer 50 includes a known hole transport material, such as a p-type conductive polymer such as polyaniline, polythiophene, or polypyrrole, or a p-type small molecule organic semiconductor such as thiophene, thiadiazole, or spirobifluorene.

[0031] Of the above, it is preferable to use spirobifluorene as the hole transport material. For example, 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) can be suitably used as the spirobifluorene. By using spirobifluorene as the hole transport material, it is possible to suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature of 80°C or higher.

[0032] The thickness of the hole transport layer 50 is preferably about 10 nm to 800 nm. The thickness of the hole transport layer 50 is more preferably about 50 nm to 500 nm. When the thickness of the hole transport layer 50 is 50 nm or more, the coverage of the hole transport layer 50 is sufficient, and when the thickness of the hole transport layer 50 is 500 nm or less, the resistance of the hole transport layer 50 can be kept low.

[0033] The hole transport layer 50 contains a heteroaromatic compound represented by the following general formula (1). (Ar １ is a heteroaryl group containing one or more nitrogen or sulfur atoms, and Y is —C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-, and Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group, and x is an integer of 1 to 3. １ is Y-Ar ２ may be substituted with a substituent different from

[0034] Ar in the heteroaromatic compound represented by general formula (1) １ is a heteroaryl group containing one or more nitrogen or sulfur atoms. １ Examples of heteroaryl rings constituting Ar include 3-, 4-, 5-, 6-, 7-, 8-, and 9-membered heteroaryl rings. １ is preferably a 5- or 6-membered heteroaryl ring. １ The number of nitrogen atoms or sulfur atoms contained in is preferably 3 or less.

[0035] Ar １ Among the hydrogen atoms constituting the heteroaryl ring of Y-Ar, 1 to 3 hydrogen atoms are ２ Y is substituted by -C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-.

[0036] Y is -C ｎ H ２ｎ -, Ar １ and Ar ２ is directly bonded to or bonded to via an alkyl chain having 6 or less carbon atoms. The alkyl chain may be linear or branched. ｍ H ２ｍ－２ -or-C ｍ H ２ｍ－４ -, Ar １ and Ar ２ is bonded to the alkylene group via an alkene chain (a hydrocarbon chain having a double bond) or an alkyne chain (a hydrocarbon chain having a triple bond) having 2 to 6 carbon atoms.

[0037] Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group. ２When is an aryl group, the aromatic ring may be a 3-, 4-, 5-, 6-, 7-, 8-, or 9-membered ring. Among these, the aromatic ring is preferably a 5- or 6-membered aryl group. Furthermore, the hydrogen atoms of the aryl group may be substituted with any substituent.

[0038] Ar ２ When is a heteroaryl group, the heteroaryl ring can be a 3-, 4-, 5-, 6-, 7-, 8-, or 9-membered ring. Of these, the heteroaryl ring is preferably a 5- or 6-membered ring. In the heteroaryl group, a hydrogen atom may be substituted with an optional substituent.

[0039] Ar １ is Y-Ar ２ That is, Ar may be substituted with a substituent different from Ar １ is Y-Ar ２ where Y-Ar can be substituted by any substituent different from ２ The substituent different from Ar １ In addition to the case where the substituent substituted on Y-Ar is a substituent that does not have an aryl group or a heteroaryl group, ２ and the structure corresponding to Y or Ar ２ This includes cases where one or both of the structures corresponding to the following are different substituents.

[0040] Examples of the heteroaromatic compound represented by general formula (1) include compounds represented by the following formulae (A1) to (A10).

[0041] By including the heteroaromatic compound represented by general formula (1) in the hole transport layer 50, it is possible to suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature.

[0042] In a preferred embodiment of the perovskite solar cell 1, the heteroaromatic ring compound represented by the general formula (1) is Ar １ In the present invention, it is preferable that the compound contains a compound in which the heteroaryl group represented by the following formula (I) is a pyridine group. By adopting such a form, it is possible to further suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature.

[0043] In a preferred embodiment of the perovskite solar cell 1, the heteroaromatic compound represented by the general formula (1) is ｎ H ２ｎ - and n=0. ２ is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group. By adopting the above-mentioned embodiment, it is possible to further suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature.

[0044] In a preferred embodiment of the perovskite solar cell of the present invention, the heteroaromatic compound represented by general formula (1) preferably contains one or more compounds selected from 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine. By adopting such a configuration, it is possible to further suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature.

[0045] The amount of the heteroaromatic compound represented by general formula (1) added is preferably 1% by weight to 200% by weight, and more preferably 20% by weight to 100% by weight, relative to the hole transport material. By adding the heteroaromatic compound represented by general formula (1) in an amount of 1% by weight or more relative to the hole transport material, it is possible to further suppress a decrease in photoelectric conversion efficiency when the perovskite solar cell 1 is placed in a high environmental temperature.

[0046] The additive contained in the hole transport layer 50 is not particularly limited, and known materials can be used. The hole transport layer 50 may contain a lithium salt or a cobalt complex as an additive. Examples of additives added to the hole transport layer 50 include lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and tris(1-(pyridin-2-yl)-1H-pyrazole)cobalt(III)tris(bis(trifluoromethanesulfonyl)imide) (Co-TFSI). Among these, Li-TFSI and / or Co-TFSI can be preferably used as the additive.

[0047] The concentration of the lithium salt and cobalt complex added to spiro-OMeTAD is preferably 1% by weight to 100% by weight.

[0048] The hole transport layer 50 can be formed by a known film formation method depending on the type of material to be laminated. For example, it can be formed by spin coating, coating, vapor deposition, or spraying. For example, a hole transport material such as spiro-OMeTAD is dissolved in an organic solvent such as chlorobenzene, and a heteroaromatic compound represented by general formula (1) is added in an amount of 1% by weight to 200% by weight based on the hole transport material, and an additive such as Li-TFSI is added in an amount of 1% by weight to 100% by weight based on the hole transport material, and the mixture is stirred. This solution is spin-coated onto the perovskite layer 40 at 4000 rpm for 20 to 40 seconds, and then dried.

[0049] There are no particular limitations on the material of the second electrode 60, and known materials can be used. Examples of materials that can be used for the second electrode 60 include metals such as gold, silver, copper, and aluminum, conductive transparent materials such as tin oxide, indium tin oxide (ITO), aluminum zinc oxide (AZO), indium zinc oxide (IZO), and gallium zinc oxide (GZO), and carbon electrodes.

[0050] The perovskite solar cell 1 may include other layers in addition to the layers described above. The other layers that the perovskite solar cell 1 may include can be produced by known methods. The positions of the hole transport layer 50 and the electron transport layer 30 may also be reversed. A plurality of solar cells may be included, such as in a tandem solar cell. An encapsulating material or an adsorbent material may also be included.

[0051] EXAMPLES The present invention will be described below with reference to examples, although the present invention is not limited to these examples.

[0052] Example 1-1 (1) Fabrication of Perovskite Solar Cell Glass with a transparent conductive layer (FTO glass) was used as the support substrate 10 and the first electrode 20. The FTO glass was subjected to UV / O ３ After cleaning (for 20 minutes), the electron transport layer 30 was laminated on the FTO glass by spin coating. Here, tin dioxide (SnO ２ ) was used. ２ The dispersion solution in which the nanoparticles were dispersed was spin-coated on an FTO glass substrate at 3000 rpm for 12 seconds, and then sintered on a hot plate (150° C.) for 30 minutes.

[0053] Thereafter, the perovskite layer 40 was deposited on the electron transport layer 30 by spin coating. The precursor solution for the perovskite layer was prepared by dissolving 17.6 mg of CsI, 7.3 mg of MACl, 197.8 mg of FAI, and PbI in a solvent (DMF: 750 μL, DMSO: 250 μL). ２ The sample was prepared by mixing 611.2 mg of the above. Spin coating was performed at 1000 rpm for 12 seconds, followed by 6000 rpm for 30 seconds. 10 seconds before the end of spin coating, 500 μL of diethyl ether was added dropwise. The sample was then sintered on a hot plate (150 °C, 10 minutes).

[0054] Next, a hole transport layer 50 was prepared. The hole transport layer 50 was prepared by laminating a solution for the hole transport layer 50 on the perovskite layer 40 using a spin coating method (4000 rpm, 20 seconds) and then drying (85°C, 10 minutes). The solution for the hole transport layer 50 was prepared by mixing 120 mg of spiro-OMeTAD, 41.4 μL of a LiTFSI solution (LiTFSI:acetonitrile=99 mg:263 μL), and 0.5 M of the compound represented by formula (A1) above with chlorobenzene (1 mL).

[0055] Finally, a second electrode (gold, 70 nm) was laminated by vapor deposition, and then a moisture absorbent was attached and sealed to produce a perovskite solar cell.

[0056] (2) Evaluation of photoelectric conversion efficiency of perovskite solar cells The initial photoelectric conversion efficiency of the perovskite solar cells manufactured as described above was measured using a current-voltage method and a solar simulator (AM1.5), and was evaluated according to the following criteria.

[0057] A: The photoelectric conversion efficiency of the perovskite solar cell of the example was 60% or more of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 1. B: The photoelectric conversion efficiency of the perovskite solar cell of the example was 20% or more but less than 60% of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 1. C: The photoelectric conversion efficiency of the perovskite solar cell of the example was less than 20% of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 1.

[0058] (3) High-Temperature Durability Test of Perovskite Solar Cells The perovskite solar cells fabricated as described above were evaluated for the decrease in photoelectric conversion efficiency when placed in a high-temperature environment (hereinafter, sometimes simply referred to as "high-temperature durability test"). In the high-temperature durability test, the perovskite solar cells whose initial photoelectric conversion efficiency had been measured were exposed to an air atmosphere at 85°C for 300 hours, and then the photoelectric conversion efficiency was measured again. The photoelectric conversion efficiency was measured using the same method as for measuring the initial photoelectric conversion efficiency.

[0059] The change in photoelectric conversion efficiency of the perovskite solar cell after 300 hours of exposure at 85°C was evaluated according to the following criteria: A: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was 15 times or more that of the perovskite solar cell of Comparative Example 1. B: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was 1.5 times or more but less than 15 times that of the perovskite solar cell of Comparative Example 1. C: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was less than 1.5 times that of the perovskite solar cell of Comparative Example 1.

[0060] Examples 1-2 to 1-11, Comparative Example 1 (1) Fabrication and Evaluation of Perovskite Solar Cells In the perovskite solar cells according to Examples 1-2 to 1-11 and Comparative Example 1, compound (A2) to compound (A11) or compound (B1) was used instead of compound (A1) when fabricating the hole transport layer 50. Except for this, the perovskite solar cells according to Examples 1-2 to 1-11 and the perovskite solar cell according to Comparative Example 1 were fabricated in the same manner as in Example 1-1, and the initial photoelectric conversion efficiency of the perovskite solar cells and the photoelectric conversion efficiency after exposure to an air atmosphere at 85°C for 300 hours were evaluated.

[0061] Table 1 shows the results of the high-temperature durability test of the perovskite solar cells 1 according to Examples 1-1 to 1-11 and Comparative Example 1.

[0062]

[0063] The perovskite solar cells 1 of Examples 1-1 to 1-5 and 1-10 to 1-11, each containing a compound represented by chemical formulas (A1) to (A5) and (A10) to (A11) in the hole transport layer 50, showed a favorable result of being rated A in terms of the retention rate of photoelectric conversion efficiency after exposure to an air atmosphere at 85°C for 300 hours.

[0064] Furthermore, in the perovskite solar cells 1 of Examples 1-6 to 1-9, in which the hole transport layer 50 contained the compounds represented by chemical formulas (A6) to (A9), a decrease in photoelectric conversion efficiency was observed in an evaluation of the photoelectric conversion efficiency after 300 hours of exposure to an atmospheric atmosphere at 85°C. However, it was confirmed that the decrease in photoelectric conversion efficiency was suppressed compared to the perovskite solar cell of Comparative Example 1, in which the hole transport layer 50 contained TBP.

[0065] The compounds represented by the chemical formulas (A1) to (A5) are compounds represented by the chemical formula (1) in which Ar １ The heteroaryl group represented by the formula (A1) to (A5) contains a pyridine skeleton. ｎ H ２ｎ -, n=0, Ar ２ is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group. On the other hand, it can be seen that the perovskite solar cells according to Examples 1-1 to 1-5 have a photoelectric conversion efficiency retention rate of 85% or more after exposure to an air atmosphere at 85°C for 300 hours, which is a favorable result, and is 15 times or more that of the perovskite solar cell according to Comparative Example 1.

[0066] That is, the perovskite solar cell has a hole transport layer 50 containing Ar in the chemical formula (1). １ The heteroaryl group represented by the formula (1) contains a substance having a pyridine skeleton, so that a decrease in photoelectric conversion efficiency can be suppressed when the perovskite solar cell is placed in a high-temperature environment. ｎ H ２ｎ -, n=0, Ar ２ By including a compound that is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group, a decrease in photoelectric conversion efficiency is suppressed when the perovskite solar cell is placed in a high-temperature environment.

[0067] Furthermore, the compounds represented by chemical formulas (A1) to (A3) contain one or more compounds selected from 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine, and are suitable for use in the heteroaromatic compounds of general formula (1). This allows for a more favorable result of a photoelectric conversion efficiency retention rate of 90% or more in evaluation of photoelectric conversion efficiency after 300 hours of exposure to an air atmosphere at 85°C.

[0068] That is, it has been confirmed that the heteroaromatic compound represented by general formula (1) contains one or more compounds selected from 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine, and therefore the decrease in photoelectric conversion efficiency of the perovskite solar cell is suppressed when the perovskite solar cell is placed in a high-temperature environment.

[0069] [Example 2] - Example 2-1 to Example 2-3, Comparative Example 2 (1) Fabrication of Perovskite Solar Cell In Examples 2-1 to 2-3 and Comparative Example 2, when fabricating the hole transport layer 50, a solution for the hole transport layer 50 containing CoTFLI was used instead of the solution for the hole transport layer 50 used in Example 1-1. The solution for the hole transport layer containing CoTFLI was prepared by mixing 120 mg of spiro-OMeTAD, 41.4 μL of a LiTiFSI solution (LiTFSI:acetonitrile=99 mg:263 μL), 32.4 μL of a CoTFSI solution (CoTFSI:acetonitrile=196 mg:379 μL), and 0.5 M of a pyridine derivative per 1 mL of chlorobenzene.

[0070] Furthermore, in the perovskite solar cells according to Examples 2-2 to 2-3, the compound (A6) and the compound (A12) were used instead of the compound (A1) in producing the hole transport layer 50 in the perovskite solar cell according to Example 2-1. Except for this, the perovskite solar cells according to Examples 2-2 to 2-3 were produced in the same manner as in Example 2-1.

[0071] (2) Evaluation of photoelectric conversion efficiency of perovskite solar cells The initial photoelectric conversion efficiency was measured for the perovskite solar cells according to Examples 2-1 to 2-3 and Comparative Example 2. The photoelectric conversion efficiency was measured using a current-voltage method and a solar simulator (AM1.5), and was evaluated according to the following criteria.

[0072] A: The photoelectric conversion efficiency of the perovskite solar cell of the example was 60% or more of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 2. B: The photoelectric conversion efficiency of the perovskite solar cell of the example was 20% or more but less than 60% of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 2. C: The photoelectric conversion efficiency of the perovskite solar cell of the example was less than 20% of the photoelectric conversion efficiency of the perovskite solar cell of comparative example 2.

[0073] (3) High-Temperature Durability Test of Perovskite Solar Cells A high-temperature durability test was conducted on the perovskite solar cells according to Examples 2-1 to 2-3 and Comparative Example 2. In the high-temperature durability test, the photoelectric conversion efficiency of the perovskite solar cell was measured, and the perovskite solar cell was exposed to an air atmosphere at 85°C for 300 hours, after which the photoelectric conversion efficiency was measured again. The photoelectric conversion efficiency was measured using the same method as in the measurement of the initial photoelectric conversion efficiency.

[0074] The change in photoelectric conversion efficiency of the perovskite solar cell after 300 hours of exposure at 85°C was evaluated according to the following criteria: A: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was 15 times or more that of the perovskite solar cell of Comparative Example 2. B: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was 1.5 times or more but less than 15 times that of the perovskite solar cell of Comparative Example 2. C: The photoelectric conversion efficiency retention rate of the perovskite solar cell of the example was less than 1.5 times that of the perovskite solar cell of Comparative Example 2.

[0075] Table 2 shows the evaluation results of the perovskite solar cells according to Examples 2-1 to 2-3 and Comparative Example 2.

[0076]

[0077] The perovskite solar cells of Examples 2-1 to 2-3, which contain the compounds represented by chemical formulas (A1), (A6), and (A12) in the hole transport layer 50, showed a decrease in photoelectric conversion efficiency in an evaluation of photoelectric conversion efficiency after exposure to an atmospheric atmosphere at 85°C for 300 hours. However, it was confirmed that the decrease in photoelectric conversion efficiency was suppressed compared to the perovskite solar cell of Comparative Example 2, which contains TBP in the hole transport layer 50.

[0078] Examples 3-4, Comparative Examples 3-4 (1) Fabrication and Evaluation of Perovskite Solar Cells In Example 3 and Comparative Example 3, spiro-TTB (2,2',7,7'-Tetrakis(di-p-tolyamino)-9,9'-spirobi[fluoren]) was used instead of spiro-OMeTAD when fabricating the hole transport layer 50. The solution for the hole transport layer containing spiro-TTB was prepared by mixing 60 mg of spiro-TTB, 20.7 μL of LiTiFSI solution (LiTFSI:acetonitrile = 99 mg:263 μL), and 0.25 M of a pyridine derivative per mL of chlorobenzene. In Example 4 and Comparative Example 4, poly(3-hexylthiophene) (P3HT) was used as the hole transport material contained in the hole transport layer 50. The solution for the hole transport layer containing P3HT was prepared by mixing 10 mg of P3HT, 20.7 μL of a LiTiFSI solution (LiTFSI:acetonitrile=99 mg:263 μL), and 0.25 M of a pyridine derivative in 1 mL of chlorobenzene. Except for this, perovskite solar cells according to Examples 3 and 4 and Comparative Examples 3 and 4 were produced in the same manner as in Example 1-1, and the initial photoelectric conversion efficiency of the perovskite solar cells and the photoelectric conversion efficiency after exposure to an air atmosphere at 85°C for 300 hours were evaluated.

[0079] Table 3 shows the evaluation results of the perovskite solar cells according to Example 3 and Comparative Example 3.

[0080]

[0081] Table 4 shows the evaluation results of the perovskite solar cells according to Example 4 and Comparative Example 4.

[0082]

[0083] Comparisons between Example 3 and Comparative Example 3, and between Example 4 and Comparative Example 4, confirmed that perovskite solar cells in which the hole transport layer 50 contains the heteroaromatic compound represented by general formula (1) have the effect of suppressing a decrease in photoelectric conversion efficiency when placed in a high-temperature environment, even when the hole transport material is spiro-TTB or P3HT.

[0084] In Example 4 and Comparative Example 4, P3HT, which was used as the hole transport material, is known to have excellent thermal durability. The perovskite solar cell (Comparative Example 4) whose hole transport layer contains TBP exhibited a 15% decrease in photoelectric conversion efficiency after 300 hours of exposure to an 85°C environment. However, the perovskite solar cell (Example 4) whose hole transport layer contains 4-phenylpyridine exhibited no decrease in photoelectric conversion efficiency even after 300 hours of exposure to an 85°C environment, demonstrating extremely favorable results. This is thought to be due to the effect of combining P3HT, a hole transport material with excellent thermal durability, with 4-phenylpyridine, which improves the thermal durability of the hole transport material.

[0085] Example 5 and Comparative Example 5 (1) Fabrication and Evaluation of Perovskite Solar Cells In Example 5 and Comparative Example 5, the additive added to the hole transport layer 50 was NaTFSI (Bis(trifluoromethanesulfonyl)imide Sodium Salt), instead of LiTFSI used in Example 1-1. A solution for the hole transport layer containing NaTFSI was prepared by mixing 1120 mg of spiro-OMeTAD, 72.2 mg of NaTFSI, and 0.5 M of a pyridine derivative with 1 mL of chlorobenzene. Except for this, perovskite solar cells according to Example 5 and Comparative Example 5 were fabricated in the same manner as in Example 1-1, and the initial photoelectric conversion efficiency of the perovskite solar cells and the photoelectric conversion efficiency after exposure to an air atmosphere at 85°C for 300 hours were evaluated.

[0086] Table 5 shows the evaluation results of the perovskite solar cells according to Example 5 and Comparative Example 5.

[0087]

[0088] A comparison between Example 5 and Comparative Example 5 confirmed that a perovskite solar cell containing a heteroaromatic compound represented by general formula (1) in the hole transport layer 50 is effective in suppressing a decrease in photoelectric conversion efficiency when placed in a high-temperature environment, even when the hole transport layer 50 contains NaTFSI, which is different from LiTFSI and CoTFSI, as an additive.

[0089] The effects achieved by the perovskite solar cell 1 according to the embodiment will be described below.

[0090] (1) In the perovskite solar cell 1 according to the embodiment, the hole transport layer 50 contains a heteroaromatic compound represented by the following general formula (1): (Ar １ is a heteroaryl group containing one or more nitrogen or sulfur atoms, and Y is —C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-, and Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group, and x is an integer of 1 to 3. １ is Y-Ar ２ The heteroaromatic compound represented by general formula (1) can suppress a decrease in the photoelectric conversion efficiency of the perovskite solar cell even when the hole transport material contained in the hole transport layer 50 is placed in a high environmental temperature.

[0091] (2) In the perovskite solar cell according to the embodiment, the heteroaromatic compound represented by the general formula (1) is Ar １ The compound includes a compound in which the heteroaryl group represented by the formula (I) is a pyridine group. This makes it possible to further suppress a decrease in the photoelectric conversion efficiency of the perovskite solar cell 1 even when the perovskite solar cell 1 is placed in a high environmental temperature.

[0092] (3) The heteroaromatic compound represented by the general formula (1) is a compound in which Y is —C ｎ H ２ｎ-, n=0, Ar ２ is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group. This makes it possible to further suppress a decrease in the photoelectric conversion efficiency of the perovskite solar cell 1 even when the perovskite solar cell 1 is placed in a high environmental temperature.

[0093] (4) The heteroaromatic compound represented by general formula (1) contains one or more compounds selected from 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine, thereby further suppressing a decrease in the photoelectric conversion efficiency of the perovskite solar cell 1 even when the perovskite solar cell is placed in a high environmental temperature.

[0094] (5) The hole transport layer 50 further includes an additive, and the additive is LiTFSI and / or CoTFSI. This makes it possible to further suppress a decrease in the photoelectric conversion efficiency of the perovskite solar cell 1.

[0095] (6) The hole transport layer 50 includes a hole transport material having a spirobifluorene skeleton, which prevents a decrease in the photoelectric conversion efficiency of the perovskite solar cell.

[0096] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0097] REFERENCE SIGNS LIST 1... perovskite solar cell, 10... supporting substrate, 20... first electrode, 30... electron transport layer, 40... perovskite layer, 50... hole transport layer, 60... second electrode

Claims

1. A perovskite solar cell comprising a first electrode, a perovskite layer, a hole transport layer, and a second electrode, wherein the hole transport layer contains a heteroaromatic compound represented by the following general formula (1): (Ar １ is a heteroaryl group containing one or more nitrogen or sulfur atoms, and Y is —C ｎ H ２ｎ - (where n is an integer of 0 to 6), -C ｍ H ２ｍ－２ - (where m is an integer of 2 or more and 6 or less), -C ｍ H ２ｍ－４ -, -CO-, and Ar ２ is an optionally substituted aryl group or an optionally substituted heteroaryl group, and x is an integer of 1 to 3. １ is Y-Ar ２ may be substituted with a substituent different from 2. In the perovskite solar cell according to claim 1, the heteroaromatic compound represented by the general formula (1) is １ The perovskite solar cell is characterized by comprising a compound represented by the formula (I) wherein the heteroaryl group is a pyridine group.

3. In the perovskite solar cell according to claim 2, the heteroaromatic compound represented by the general formula (1) is such that the Y is -C ｎ H ２ｎ -, n=0, and said Ar ２ is a phenyl group, a p-tolyl group, or a 1-pyrazolyl group.

4. A perovskite solar cell according to claim 3, characterized in that the heteroaromatic compound represented by general formula (1) contains one or more compounds selected from the group consisting of 4-phenylpyridine, 3-phenylpyridine, and 2-phenylpyridine.

5. A perovskite solar cell according to claim 1, wherein the hole transport layer further comprises an additive, and the additive is LiTFSI and / or CoTFSI.

6. A perovskite solar cell according to claim 1, characterized in that the hole transport layer comprises a hole transport material, and the hole transport material includes a hole transport material having a spirobifluorene skeleton.

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