Method for manufacturing perovskite solar cell

Abstract

The purpose of the present invention is to provide a method for manufacturing a perovskite solar cell capable of suppressing the occurrence of pinholes. The present invention relates to a method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound, the method comprising: a step for applying a precursor solution containing the perovskite compound as a solute to an application surface; and a step for applying a poor solvent, which has a lower solubility of the perovskite compound than the solvent of the precursor solution, to the application surface to which the precursor solution has been applied, wherein the gas concentration of the volatile organic compound in the vicinity of the application surface is less than 15000 ppm at the start of application of the poor solvent.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a perovskite solar cell. BACKGROUND

[0002] As one of solar cells, a perovskite solar cell in which a main component of a photoelectric conversion layer is a perovskite compound is known.

[0003] As a manufacturing method of a perovskite solar cell, for example, Patent Literature 1 describes a method in which, after a material film of a perovskite thin film is coated, a poor solvent in a gas or mist form is blown to the material film of the perovskite thin film, and the material film of the perovskite thin film is dried and crystallized.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2023-148126 SUMMARY

[0007] However, in the conventional manufacturing method of a perovskite solar cell, a pinhole can be generated in the photoelectric conversion layer. Therefore, an object of the present application is to provide a manufacturing method of a perovskite solar cell in which generation of a pinhole is suppressed.

[0008] The present inventors have found that by controlling the gas concentration at the timing of coating a poor solvent in the manufacturing of a perovskite solar cell, generation of a pinhole in the photoelectric conversion layer is suppressed, and thus the present application has been accomplished.

[0009] That is, the gist of the present application is as follows.

[0010] (1) A manufacturing method of a solar cell, which is a manufacturing method of a solar cell having a photoelectric conversion layer containing a perovskite compound, comprising:

[0011] a step of coating a precursor solution containing the perovskite compound as a solute on a coating surface, and

[0012] a step of coating a poor solvent, which has a solubility of the perovskite compound smaller than a solvent of the precursor solution, on the coating surface on which the precursor solution is coated, and is a step in which a gas concentration of a volatile organic compound in the vicinity of the coating surface at the timing of starting coating of the poor solvent is less than 15000 ppm.

[0013] (2) The manufacturing method of a solar cell according to the above (1), in which the gas concentration of the volatile organic compound in the vicinity of the coating surface at the timing of starting coating of the poor solvent is 1000 ppm or more.

[0014] (3) The method for manufacturing a solar cell according to any one of (1) or (2), wherein the gas concentration of volatile organic compounds in the vicinity of the coating surface at the time when the coating of the poor solvent is started is 4000 ppm or less.

[0015] (4) The method for manufacturing a solar cell according to any one of (1) to (3), wherein the gas concentration of volatile organic compounds in the vicinity of the coating surface during the period from the coating of the precursor solution to the coating of the poor solvent is less than 15000 ppm.

[0016] (5) The method for manufacturing a solar cell according to any one of (1) to (4), wherein the gas concentration of volatile organic compounds in the vicinity of the coating surface during the period from the coating of the precursor solution to the coating of the poor solvent is 7000 ppm or less.

[0017] According to the present application, it is possible to provide a method for manufacturing a perovskite solar cell in which pinholes are inhibited from being generated in a photoelectric conversion layer. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a cross-sectional schematic view showing an example of the structure of a solar cell of the present application.

[0019] Figure 2 is a schematic view showing a perovskite crystal structure.

[0020] Figure 3 is a flowchart showing a film formation process of the photoelectric conversion layer 4.

[0021] Figure 4 is a cross-sectional schematic view for explaining the process S1.

[0022] Figure 5 is a cross-sectional schematic view for explaining the process S2.

[0023] Figure 6 is a cross-sectional schematic view for explaining the process S3.

[0024] Figure 7 is a graph showing the change in the gas concentration over time in the case where the gas concentration of volatile organic compounds is changed by exhaust.

[0025] Figure 8 is a graph showing the change in the gas concentration over time in the case where the gas concentration of volatile organic compounds is changed by air supply. Figure 7 is a partial enlarged view of the graph of

[0026] Figure 9 is a graph showing the change in the gas concentration over time in the case where the gas concentration of volatile organic compounds is changed by air supply.

[0027] Figure 10 yes Figure 9 A magnified portion of the chart.

[0028] Explanation of symbols

[0029] 1: Substrate

[0030] 2a: 1st electrode layer

[0031] 2b: Second electrode layer

[0032] 3a: First carrier transport layer

[0033] 3b: Second carrier transport layer

[0034] 4: Photoelectric conversion layer

[0035] 4a: Liquid film of precursor solution

[0036] 4b: Liquid film mixed with precursor solution and poor solvent

[0037] C: Solar cell

[0038] C1, C2, C3, C4: Photoelectric conversion elements DETAILED DESCRIPTION

[0039] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0040] The present invention relates to a method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound.

[0041] The method for producing a solar cell of the present invention includes applying a precursor solution containing a perovskite compound as a solute to a coating surface (step S1), and applying a poor solvent to the coating surface coated with the precursor solution (step S2).

[0042] In the present invention, in step S2 , the gas concentration of volatile organic compounds near the coating surface at the start of coating of the poor solvent is controlled within a specific range, thereby suppressing the generation of pinholes in the photoelectric conversion layer.

[0043] <Structure of a solar cell>

[0044] First, the structure of a perovskite solar cell produced by the production method of the present invention (hereinafter also referred to as the solar cell of the present invention) will be described in detail. Figure 1 1 is a schematic cross-sectional view showing an example of the structure of the solar cell of the present invention.

[0045] like Figure 1As shown, in one embodiment, the solar cell C of the present application has: a substrate 1, a first electrode layer 2a, a first carrier transport layer 3a, a photoelectric conversion layer 4, a second carrier transport layer 3b, and a second electrode layer 2b.

[0046] (Photoelectric conversion layer 4)

[0047] The photoelectric conversion layer 4 is a layer located in the middle of the first carrier transport layer 3a and the second carrier transport layer 3b. The photoelectric conversion layer 4 generates charge carriers by receiving light.

[0048] The charge carriers generated in the photoelectric conversion layer 4 are transferred to either of the first carrier transport layer 3a and the second carrier transport layer 3b.

[0049] More specifically, the positive charge carriers, i.e., holes, generated in the photoelectric conversion layer 4 are transferred to the first electrode layer 2a or the second electrode layer 2b via one of the first carrier transport layer 3a and the second carrier transport layer 3b that corresponds to a hole transport layer.

[0050] In addition, the negative charge carriers, i.e., electrons, generated in the photoelectric conversion layer 4 are transferred to the first electrode layer 2a or the second electrode layer 2b via one of the first carrier transport layer 3a and the second carrier transport layer 3b that corresponds to an electron transport layer.

[0051] It should be noted that the manufacturing method of the present application suppresses the generation of pinholes in the photoelectric conversion layer 4, as will be described later in detail. The solar cell of the present application is excellent in power generation performance because the generation of pinholes in the photoelectric conversion layer is suppressed, and also prevents short circuit.

[0052] The photoelectric conversion layer 4 contains a perovskite compound, and preferably contains a perovskite compound as a main component. The content of the perovskite compound in the photoelectric conversion layer 4 is usually 60% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 100% by weight.

[0053] The thickness of the photoelectric conversion layer is usually 100 nm to 1000 nm.

[0054] The perovskite compound is a compound having a perovskite-type crystal structure. Figure 2 is a schematic diagram showing a perovskite-type crystal structure. As shown in Figure 2 The perovskite-type crystal structure has a cubic unit cell, A is arranged at each vertex of the cubic, B is arranged at the body center, and X is arranged at each face center of the cubic with B as the center. That a compound has a perovskite-type crystal structure can be confirmed, for example, by X-ray diffraction measurement.

[0055] The perovskite compound can be represented by the following formula (1), for example.

[0056] ABX3(1)

[0057] (In the formula, A is a monovalent cation, B is a divalent cation, and X is a monovalent anion.)

[0058] In one embodiment, in formula (1), A is at least one selected from the group consisting of a monovalent organic ammonium ion, a monovalent amidinium ion, and a monovalent metal ion.

[0059] As the monovalent organic ammonium ion, for example, CH3NH3 + (methylammonium ion: MA), C2H5NH3 + , C3H7NH3 + , and C4H9NH3 + may be given.

[0060] As the monovalent amidinium ion, for example, HC(NH2)2 + (amidinium ion: FA) may be given.

[0061] As the monovalent metal ion, for example, rubidium ion (Rb + ) and cesium ion (Cs + ) may be given.

[0062] In formula (1), A can be a combination of the monovalent organic ammonium ion, the monovalent amidinium ion, and the monovalent metal ion. In formula (1), A is preferably MA, FA, or Cs + , and a combination of two or three of them.

[0063] In one embodiment, in formula (1), B is a divalent metal ion, for example, a lead ion (Pb 2+ ), a tin ion (Sn 2+ ), and a combination thereof. From the viewpoint of durability, B is preferably Pb 2+ .

[0064] In one embodiment, in formula (1), X is a halogen ion, for example, at least one selected from the group consisting of a fluoride ion (F － ), a chloride ion (Cl － ), a bromide ion (Br － ), and an iodide ion (I － ), preferably Cl － , Br － , and I － .

[0065] (1st carrier transport layer 3a and 2nd carrier transport layer 3b)

[0066] Returning to the explanation of Figure 1 .

[0067] The first carrier transport layer 3a receives the charge carriers generated in the photoelectric conversion layer 4 and transports the charge carriers to the first electrode layer 2a.

[0068] In the case where the first carrier transport layer 3a is a hole transport layer (HTL), the first carrier transport layer 3a transports holes to the first electrode layer 2a.

[0069] In the case where the first carrier transport layer 3a is an electron transport layer (ETL), the first carrier transport layer 3a transports electrons to the first electrode layer 2a.

[0070] Note that detailed descriptions of the hole transport layer and the electron transport layer will be given later.

[0071] The second carrier transport layer 3b receives the charge carriers generated in the photoelectric conversion layer 4 and transports the charge carriers to the second electrode layer 2b.

[0072] In the case where the second carrier transport layer 3b is a hole transport layer, the second carrier transport layer 3b transports holes to the second electrode layer 2b.

[0073] In the case where the second carrier transport layer 3b is an electron transport layer, the second carrier transport layer 3b transports electrons to the second electrode layer 2b.

[0074] In the first embodiment, the first carrier transport layer 3a is an electron transport layer, and the second carrier transport layer 3b is a hole transport layer. That is, in the first embodiment, the solar cell C of the present application has, in the stated order, a substrate, a cathode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an anode.

[0075] In the second embodiment, the first carrier transport layer 3a is a hole transport layer, and the second carrier transport layer 3b is an electron transport layer. That is, in the second embodiment, the solar cell C of the present application has, in the stated order, a substrate, an anode, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a cathode.

[0076] The hole transport layer has a function of transporting holes generated by photoelectric conversion by the photoelectric conversion layer to the first electrode layer or the second electrode layer. As a material of the hole transport layer, a publicly known organic material or inorganic material that can be used in a hole transport layer can be used.

[0077] The organic material that can be used as the material of the hole transport layer is not particularly limited, and examples thereof include 2,2',7,7'-tetra-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), poly(ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 3PATAT-C3 (non-patent document: Journal of The American Chemistry Society 2023, No. 145, p. 7528), and the like.

[0078] The inorganic material that can be used as the material of the hole transport layer is not particularly limited, and examples thereof include nickel oxide, copper oxide, and the like.

[0079] In the above-described first embodiment of the solar cell of the present application, the material of the hole transport layer is preferably Spiro-OMeTAD, PTAA, and nickel oxide.

[0080] In the above-described second embodiment of the solar cell of the present application, the material of the hole transport layer is preferably PEDOT:PSS, PTAA, and nickel oxide.

[0081] The electron transport layer has a function of transporting the electron generated by the photoelectric conversion performed by the photoelectric conversion layer to the first electrode layer or the second electrode layer. As the material of the electron transport layer, a publicly known organic material or inorganic material that can be used in the electron transport layer can be used.

[0082] The organic material that can be used as the material of the electron transport layer is not particularly limited, and examples thereof include fullerene compounds, phenanthroline derivatives (for example, bathocuproine), polyethyleneimines, and the like. As the fullerene compound, for example, fullerene (for example, C60 fullerene, C70 fullerene), a derivative obtained by adding a substituent to the fullerene (for example, [6,6]-phenyl-C61-butyric acid methyl ester (also referred to as PCBM or

[60] PCBM), [6,6]-phenyl-C71-butyric acid methyl ester (also referred to as PCBM or

[70] PCBM)), and the like can be given. 61 [6,6]-phenyl-C71-butyric acid methyl ester (also referred to as PCBM or

[70] PCBM)), and the like can be given. 71 [6,6]-phenyl-C71-butyric acid methyl ester (also referred to as PCBM or

[70] PCBM)), and the like can be given.

[0083] As the inorganic material that can be used as the material of the electron transport layer, titanium oxide, tin oxide, zinc oxide, and the like can be given.

[0084] In the above-described first embodiment of the solar cell of the present application, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproine, polyethyleneimines, titanium oxide, and tin oxide.

[0085] In addition, in the above-described second embodiment of the solar cell of the present application, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproin, or polyethyleneimine.

[0086] (First electrode layer 2a and second electrode layer 2b)

[0087] The first electrode layer 2a is an electrode that is in contact with the first carrier transport layer 3a. In addition, the second electrode layer 2b is an electrode that is in contact with the second carrier transport layer 3b.

[0088] As the material of the first electrode layer and the second electrode layer, a metal material such as aluminum (Al), silver (Ag), gold (Au), a transparent conductive film such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), or a carbon nanotube, which is known as an electrode of a solar cell, can be used.

[0089] The material of the first electrode layer and the second electrode layer is preferably ITO, IZO, and FTO.

[0090] (Substrate 1)

[0091] The substrate 1 is a plate-shaped or film-shaped member that supports the first electrode layer 2a, the first carrier transport layer 3a, the photoelectric conversion layer 4, the second carrier transport layer 3b, and the second electrode layer 2b.

[0092] As the material of the substrate 1, there is no particular limitation, and for example, an inorganic material such as glass, an organic material such as polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, liquid crystal polymer, or cyclic olefin polymer, or a metal material such as stainless steel or silicon can be used.

[0093] The substrate 1 can be transparent or non-transparent. In the case where light is incident from the surface of the substrate, a transparent substrate is used. As the transparent substrate, a substrate composed of glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, or cyclic olefin polymer can be used. In addition, in the case where light is incident from the side opposite to the substrate, the substrate can be non-transparent.

[0094] <Method for manufacturing solar cell>

[0095] Next, the method for manufacturing a solar cell, that is, the manufacturing method of the present application will be described in more detail.

[0096] In the production method of the present embodiment, the solar cell is produced by sequentially forming the first electrode layer, the first carrier transport layer, the photoelectric conversion layer, the second carrier transport layer, and the second electrode layer on the substrate 1 in the order described. The production method of the present embodiment is characterized in the film formation process of the photoelectric conversion layer 4, and the film formation processes of the other parts can be performed by the same method as in the conventional photoelectric conversion element.

[0097] Hereinafter, the film formation process of the photoelectric conversion layer 4 will be described in detail. Figure 3 is a flowchart showing the film formation process of the photoelectric conversion layer 4.

[0098] In the film formation process of the photoelectric conversion layer 4, first, the precursor solution is applied to the application surface (process S1). Figure 4 is a cross-sectional schematic view for explaining the process S1.

[0099] More specifically, Figure 4 is a cross-sectional schematic view showing the cross section of the photoelectric conversion element C1 before the process S1 is performed and the photoelectric conversion element C2 in the production after the process S1 is performed.

[0100] As shown in Figure 4 , the photoelectric conversion element C1 before the process S1 is performed includes the substrate 1, the first electrode layer 2a, and the first carrier transport layer 3a. As described above, the photoelectric conversion element C1 before the process S1 is performed can be produced by forming the first electrode layer 2a and the first carrier transport layer 3a on the substrate 1 using a known method.

[0101] In the process S1 of the present embodiment, the precursor solution is applied to the surface of the first carrier transport layer 3a. That is, in the present embodiment, the surface of the first carrier transport layer 3a corresponds to the application surface. The precursor solution applied to the surface of the first carrier transport layer 3a forms a liquid film 4a as shown in the cross-sectional schematic view of the photoelectric conversion element C2.

[0102] The precursor solution refers to a solution containing a perovskite compound as a solute. The precursor solution can be prepared by dissolving a perovskite compound, a solvent adduct of a perovskite compound, or a plurality of raw materials of a perovskite compound in an appropriate solvent.

[0103] For example, in the case where the perovskite compound is represented by the above formula (1), the precursor solution can be prepared by dissolving one or more of the compounds represented by the following formula (2) and one or more of the compounds represented by the following formula (3) in an appropriate solvent.

[0104] AX (2)

[0105] BX2 (3)

[0106] From the viewpoint of the solubility of the perovskite compound, the solvent of the precursor solution is preferably a polar solvent. In addition, from the viewpoint of the stability of the perovskite compound in the solution, the solvent of the precursor solution is preferably an aprotic solvent.

[0107] Examples of the solvent which can be used as the solvent of the precursor solution include N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), γ-butyrolactone, and a mixed solvent containing one or more of these solvents.

[0108] Note that in the process S1 of this embodiment, the surface of the first carrier transport layer 3a corresponds to the application surface, but the application surface in the process S1 is not limited to the surface of the first carrier transport layer 3a.

[0109] For example, in the case where the solar cell C after production does not have the first carrier transport layer, the precursor solution is applied to the first electrode layer 2a, and the surface of the first electrode layer 2a corresponds to the application surface.

[0110] In addition, in the case where the solar cell C after production has another layer between the photoelectric conversion layer 4 and the first carrier transport layer 3a, the precursor solution is applied to the other layer, and the surface of the other layer corresponds to the application surface.

[0111] That is, the application surface in the process S1 is appropriately selected depending on the configuration of the solar cell C after production. More specifically, the application surface in the process S1 is the surface of the photoelectric conversion layer 4 on the substrate side in the solar cell C after production.

[0112] The application of the precursor solution can be performed by a publicly known method.

[0113] The method for applying the precursor solution is not particularly limited as long as the precursor solution can be applied to the application surface in a substantially uniform layer, and for example, a spin coating method, an inkjet method, a spray method, a blade coating method, and a die coating method can be given.

[0114] From the viewpoint of the stability of the perovskite compound, the process S1 is preferably performed in a dry gas atmosphere, and more preferably performed in an inactive gas atmosphere. As the inactive gas, any gas can be used as long as the gas does not react with the perovskite compound, and for example, nitrogen, argon, or the like can be given.

[0115] Returning to the description of Figure 3 In the film formation process of the photoelectric conversion layer 4, after the process S1, a poor solvent is applied to the application surface to which the precursor solution is applied (process S2).

[0116] Figure 5 is a cross-sectional schematic view for describing the process S2. More specifically, Figure 5is a cross-sectional view showing a cross section of the photoelectric conversion element C2 before the process S2 is performed and a photoelectric conversion element C3 in the manufacturing after the process S2 is performed.

[0117] As shown in Figure 5 by performing the process S2 of the present embodiment, the liquid film 4b in which the precursor solution and the poor solvent are mixed is formed on the surface of the first carrier transport layer 3a.

[0118] By performing the process S2 of the present embodiment, the generation of the crystal nucleus of the perovskite compound is promoted in the mixed liquid film 4b.

[0119] Here, the poor solvent refers to a solvent in which the solubility of the perovskite compound is smaller at least compared to the solvent of the precursor solution, and more preferably a solvent in which the perovskite compound is substantially not dissolved.

[0120] The poor solvent refers to, for example, a solvent in which the solubility (weight ratio of solute to solvent 100 g) of the perovskite compound at 25°C is generally less than 1% by weight, and preferably less than 0.5% by weight.

[0121] The solvent which can be used as the poor solvent is not particularly limited, and for example, substituted aliphatic hydrocarbons such as dichloromethane, chloroform, and the like; aromatic compounds such as toluene, benzene, chlorobenzene, tetralin, and the like; ethers such as diethyl ether, tetrahydrofuran (THF), and the like; alcohols having 3 or more carbon atoms; hydrocarbons having 4 to 10 carbon atoms; organic solvents such as acetic acid, and the like can be exemplified.

[0122] Note that, in the present application, the aromatic compound also includes a compound partially containing an aromatic ring. The poor solvent can be used alone or in combination with two or more of these solvents. In one embodiment, the poor solvent is chlorobenzene.

[0123] The process S2 of the present embodiment is performed while controlling the concentration of the volatile organic compound gas in the vicinity of the coating surface to be within a certain range.

[0124] More specifically, the process S2 of the present embodiment controls the concentration of the volatile organic compound gas in such a manner that the concentration of the volatile organic compound gas in the vicinity of the coating surface at the time of starting the coating of the poor solvent is less than 15,000 ppm.

[0125] Note that, the vicinity of the coating surface herein can be defined as a region in which the concentration of the volatile organic compound gas measured in the region is related to the evaporation speed of the solvent contained in the liquid film 4a or 4b on the coating surface. In one embodiment, the vicinity of the coating surface refers to, for example, a region within 25 mm in the vertical direction from the coating surface.

[0126] In the process S2, the gas concentration of the volatile organic compound at the timing at which the poor solvent is applied is controlled, whereby the volatilization speed of the solvent in the liquid film 4b is controlled to be within an appropriate range. As a result, a sufficient number of crystal nuclei of the perovskite compound are uniformly generated in the liquid film 4b.

[0127] The generated crystal nuclei of the perovskite compound grow into crystals through a process described later, and become the photoelectric conversion layer 4. Therefore, in the process S2, by uniformly generating a sufficient number of crystal nuclei, a photoelectric conversion layer 4 in which pinholes are suppressed and the perovskite compound is uniformly contained can be formed.

[0128] That is, the method for manufacturing a solar cell of the present embodiment, by having the process S2 configured as described above, can suppress the generation of pinholes in the photoelectric conversion layer 4.

[0129] In addition, the method for manufacturing a solar cell of the present embodiment, by having the process S2 configured as described above, can form a photoelectric conversion layer 4 in which the perovskite compound is uniformly contained.

[0130] Note that in the process S2 of the present embodiment, the gas concentration of the volatile organic compound in the vicinity of the application surface at the timing at which the poor solvent is started to be applied is less than 15000 ppm, preferably 10000 ppm or less, more preferably 7000 ppm or less, and particularly preferably 4000 ppm or less.

[0131] If the gas concentration of the volatile organic compound in the vicinity of the application surface is lowered, the generation of pinholes in the photoelectric conversion layer is further suppressed.

[0132] On the other hand, in a case where the gas concentration of the volatile organic compound in the vicinity of the application surface at the timing at which the poor solvent is started to be applied is too small, the surface roughness of the photoelectric conversion layer increases.

[0133] Therefore, in the process S2, the gas concentration of the volatile organic compound in the vicinity of the application surface at the timing at which the poor solvent is started to be applied is preferably 100 ppm or more, more preferably 1000 ppm or more, and particularly preferably 2000 ppm or more.

[0134] If the gas concentration of the volatile organic compound in the vicinity of the application surface is 1000 ppm or more, the surface roughness of the photoelectric conversion layer becomes sufficiently small.

[0135] If the surface roughness of the photoelectric conversion layer is sufficiently small, the film thickness of a layer adjacent to the photoelectric conversion layer can be made sufficiently small, and thus the increase in the resistance of the solar cell can be suppressed.

[0136] In summary, in step S2 , the gas concentration of volatile organic compounds near the coating surface at the start of application of the poor solvent is preferably 1000 ppm or more and less than 15000 ppm, more preferably 1000 ppm to 10000 ppm, and particularly preferably 1000 ppm to 4000 ppm.

[0137] When the gas concentration of the volatile organic compound near the coating surface is within this range, the generation of pinholes in the photoelectric conversion layer is suppressed, and the surface roughness of the photoelectric conversion layer becomes sufficiently small.

[0138] In addition, in the present invention, ppm used for gas concentration represents volume ppm.

[0139] In one embodiment, the timing of starting to apply the poor solvent may mean the timing immediately before starting to apply the poor solvent.

[0140] For example, the time when the application of the poor solvent starts may mean a time within 1 second from the start of the application of the poor solvent.

[0141] In another embodiment, when the precursor solution is applied by dripping in the form of droplets, the time of starting to apply the poor solvent may mean the time of starting to drip the poor solvent.

[0142] In step S2 , the gas concentration of the volatile organic compound near the coating surface can be adjusted by, for example, exhausting or blowing air.

[0143] When the gas concentration is adjusted by exhaust, for example, the gas concentration can be adjusted by removing the gas from the vicinity of the work area using an exhaust mechanism such as an exhaust pipe.

[0144] In addition, when adjusting by blowing air, the gas concentration can be adjusted by blowing air toward the workpiece using an air blowing mechanism such as a circulator.

[0145] From the perspective of the stability of the perovskite compound, step S2 is preferably performed in a dry gas atmosphere, more preferably in an inert gas atmosphere. As the inert gas, any gas that does not react with the perovskite compound can be used, for example, nitrogen, argon, etc.

[0146] In step S2 , the poor solvent can be applied in the same manner as the precursor solution in step S1 .

[0147] Return to Figure 3 In the film forming step of the photoelectric conversion layer 4, the film forming of the photoelectric conversion layer 4 is completed by performing an annealing treatment following step S2 (step S3).

[0148] Figure 6is a cross-sectional schematic view for explaining the process S3. More specifically, Figure 6 is a cross-sectional schematic view showing a cross section of the photoelectric conversion element C3 before the process S3 is performed and the photoelectric conversion element C4 in the manufacturing after the process S3 is performed.

[0149] As shown in Figure 6 by performing the process S3 of the present embodiment, the photoelectric conversion layer 4 is formed on the surface of the first carrier transport layer 3a.

[0150] The annealing treatment performed in the process S3 is generally a treatment of heating the liquid film 4b at a temperature of 70°C to 200°C.

[0151] Note that the manufacturing method of the present embodiment can include a drying process between the process S2 and the process S3. The drying process removes the solvent in the liquid film by using a known drying method such as a method of heating, a method of blowing dry gas, or a method of vacuuming.

[0152] In the case where the drying process is not included between the process S2 and the process S3, the process S3 can be understood as a treatment of performing the annealing treatment and the drying treatment in one step.

[0153] As explained above, the manufacturing method of the present embodiment is to make the gas concentration of the volatile organic compound near the coating surface less than 15000 ppm, and more preferably 4000 ppm or less, at the time when the application of the poor solvent is started.

[0154] According to such a configuration, the manufacturing method of the present embodiment can suppress the generation of pinholes in the photoelectric conversion layer.

[0155] In addition, the manufacturing method of the present embodiment can make the gas concentration of the volatile organic compound near the coating surface 1000 ppm or more at the time when the application of the poor solvent is started. According to such a configuration, the manufacturing method of the present embodiment can reduce the surface roughness of the photoelectric conversion layer.

[0156] In addition, the gas concentration of the volatile organic compound near the coating surface during the period from the application of the precursor solution to the application of the poor solvent can be made less than 15000 ppm, and more preferably 7000 ppm or less.

[0157] According to such a configuration, the manufacturing method of the present embodiment can further suppress the generation of pinholes in the photoelectric conversion layer.

[0158] Embodiments

[0159] Hereinafter, the present application will be described more specifically using embodiments. The scope of the technology of the present application is not limited to these embodiments.

[0160] A laminate in which a glass plate, a fluorine-doped tin oxide (FTO) film (transparent conductive film), and a titanium oxide (TiO2) layer (electron transport layer) are sequentially stacked was used as a substrate. In addition, as a precursor solution, a solution in which a ternary system CsFAMAPbI3 was dissolved in a solvent composed of DMF and DMSO was prepared.

[0161] The precursor solution was applied to the electron transport layer of the substrate under an argon atmosphere and at room temperature (25°C) while changing the gas concentration of the volatile organic compound in the application. The applied precursor solution was dropped with a poor solvent, and annealing treatment was performed to form a perovskite film containing a perovskite compound on the substrate.

[0162] The gas concentration of the volatile organic compound in the application was adjusted by exhaust and air supply. The gas concentration of the volatile organic compound was measured by a PID-type gas concentration meter in which the front end portion of a VOC (volatile organic compound) sensor was located at a position about 25 mm in the vertical direction from the application surface.

[0163] Gas concentration change based on exhaust (Examples 1 to 6 and Comparative Examples 1 and 2)

[0164] An exhaust pipe was provided in a spin coater, and the opening degree of a valve provided in the exhaust pipe was set to three levels of large, medium, and small, and the gas in the spin coater was exhausted. Each exhaust condition was subjected to two experiments, respectively.

[0165] The perovskite film was formed in the following order.

[0166] 1. Start exhaust

[0167] 2. Set the substrate on the spin coater stage

[0168] 3. Drop the precursor solution onto the substrate

[0169] 4. Start rotating the spin coater

[0170] 5. Drop chlorobenzene (poor solvent) with a pipette during rotation

[0171] 6. Stop rotating the spin coater

[0172] 7. Take out the substrate, place it on a hot plate, and perform annealing treatment (120°C)

[0173] Gas concentration change based on air supply (Examples 7 and 8)

[0174] A circulator was placed at a position about 15 cm in the horizontal direction from the work site, and air was supplied to the work site with the circulator. The air volume of the circulator was set to two levels of large and small.

[0175] The perovskite film was formed in the following order.

[0176] 1. Start air supply

[0177] 2. Set the substrate on the spin coater stage

[0178] 3. Drop the precursor solution onto the substrate

[0179] 4. Start rotating the spin coater

[0180] 5. Drop chlorobenzene (a poor solvent) with a pipette during rotation

[0181] 6. Stop rotating the spin coater

[0182] 7. Take out the substrate, place it on a hot plate, and perform annealing treatment (120°C)

[0183] The perovskite film formed on the substrate was subjected to the following analysis.

[0184] Measurement of pinholes

[0185] A transmission illumination type digital microscope was used to obtain an image of the perovskite film. The obtained image was observed from the side opposite the lens, and the pinhole portion that was visualized was subjected to image analysis to measure the area (total area) and number of pinhole portions.

[0186] Surface roughness Sa

[0187] The surface of the perovskite film was observed using a white light interference microscope, and the surface roughness Sa was calculated.

[0188] The results of analysis of the perovskite film in the case where the gas concentration of the volatile organic compound was changed by exhaust are shown in Table 1. In addition, a graph showing the change in gas concentration over time in the case where the gas concentration of the volatile organic compound was changed by exhaust is shown in Figure 7 Figure 8 A partial enlarged view of the graph of Figure 7 is shown in

[0189] [Table 1]

[0190]

[0191] As shown in Figure 7 , in the case where there was no exhaust (Comparative Examples 1 and 2), the gas concentration reached the upper limit of measurement by the gas concentration meter (15000 ppm) before the poor solvent was dropped. Thus, in Comparative Examples 1 and 2, the gas concentration before the poor solvent was dropped exceeded 15000 ppm.

[0192] In addition, as shown in Figure 7 and 8 ​As shown in Table 1, in Examples 1 to 6, the gas concentration of the volatile organic compound greatly increased after the poor solvent was dropped. From this, it was found that the gas concentration of the volatile organic compound before the poor solvent was dropped corresponds to the concentration of the gas volatilized from the solvent of the precursor solution, and the gas concentration of the volatile organic compound after the poor solvent was dropped corresponds to the concentration of the total of the gas volatilized from the solvent of the precursor solution and the poor solvent gas volatilized from the poor solvent.

[0193] As shown in Table 1, in Comparative Examples 1 and 2, many pinholes were generated in the perovskite film. It is presumed that this is because the gas concentration in the environment was high, and thus the volatilization of the solvent in the liquid film was slow, and became mottled, and thus the generation of the crystal nucleus became uneven in the plane, and as a result, became a state in which a part did not form a perovskite crystal.

[0194] As shown in Table 1, in Examples 1 to 4, the formation of pinholes was suppressed by the appropriate occurrence of the volatilization of the solvent in the liquid film. Figure 7 8 As shown in Table 1, in Examples 1 to 4, the formation of pinholes was suppressed by the appropriate occurrence of the volatilization of the solvent in the liquid film.

[0195] As shown in Table 1, in Examples 5 and 6, the formation of pinholes was greatly suppressed, and pinholes were not at all observed in the microscopic observation, on the other hand, the value of the surface roughness Sa became large. It is presumed that this is because the gas concentration in the environment was low, and thus the volatilization of the solvent in the liquid film became fast, and the generation of the crystal nucleus, the crystal growth became mottled and uneven in the plane, and a part of the crystal was raised, and it is presumed that this caused the increase in the surface unevenness. Figure 7 8 As shown in Table 1, in Examples 5 and 6, the formation of pinholes was greatly suppressed, and pinholes were not at all observed in the microscopic observation, on the other hand, the value of the surface roughness Sa became large. It is presumed that this is because the gas concentration in the environment was low, and thus the volatilization of the solvent in the liquid film became fast, and the generation of the crystal nucleus, the crystal growth became mottled and uneven in the plane, and a part of the crystal was raised, and it is presumed that this caused the increase in the surface unevenness.

[0196] From the above results, it was found that by maintaining the gas concentration of the volatile organic compound at the time of dropping the poor solvent to be appropriate in the formation of the perovskite film, the quality of the perovskite crystal was improved.

[0197] In Table 2, the analysis results of the perovskite film in the case where the gas concentration of the volatile organic compound was changed by air supply are shown. In addition, in Table 2, the gas concentration of the volatile organic compound at the time of dropping the poor solvent is shown as the initial value. Figure 9 In Table 2, the analysis results of the perovskite film in the case where the gas concentration of the volatile organic compound was changed by air supply are shown. In addition, in Table 2, the gas concentration of the volatile organic compound at the time of dropping the poor solvent is shown as the initial value. Figure 10 In Table 2, the analysis results of the perovskite film in the case where the gas concentration of the volatile organic compound was changed by air supply are shown. In addition, in Table 2, the gas concentration of the volatile organic compound at the time of dropping the poor solvent is shown as the initial value. Figure 9 In Table 2, the analysis results of the perovskite film in the case where the gas concentration of the volatile organic compound was changed by air supply are shown. In addition, in Table 2, the gas concentration of the volatile organic compound at the time of dropping the poor solvent is shown as the initial value.

[0198] [Table 2]

[0199]

[0200] As shown in Table 1, in Examples 1 to 4, the formation of pinholes was suppressed by the appropriate occurrence of the volatilization of the solvent in the liquid film.​​Figure 9 , 10 and Table 2, by keeping the gas concentration of the volatile organic compound at the time of application of the poor solvent to be appropriate, the formation of pinholes was suppressed, and furthermore, the value of the surface roughness Sa was sufficiently small.

Claims

1. A method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound, the method comprising: a step of applying a precursor solution containing the perovskite compound as a solute to an application surface, and a step of applying, to the application surface to which the precursor solution is applied, a poor solvent in which the solubility of the perovskite compound is lower than that of a solvent of the precursor solution, and a gas concentration of a volatile organic compound in the vicinity of the application surface at the time of starting application of the poor solvent is less than 15000 ppm. The gas concentration of the volatile organic compound in the vicinity of the application surface at the time of starting application of the poor solvent is 1000 ppm or more. The gas concentration of the volatile organic compound in the vicinity of the application surface at the time of starting application of the poor solvent is 4000 ppm or less. The gas concentration of the volatile organic compound in the vicinity of the application surface during a period from application of the precursor solution to application of the poor solvent is less than 15000 ppm.

2. The method for manufacturing a solar cell according to claim 1, wherein The gas concentration of the volatile organic compound in the vicinity of the application surface during a period from application of the precursor solution to application of the poor solvent is 7000 ppm or less.

3. The method for manufacturing a solar cell according to claim 1 or 2, wherein ​ 4. The method for manufacturing a solar cell according to claim 1, wherein ​ 5. The method for manufacturing a solar cell according to claim 4, wherein ​

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