Manufacturing method for perovskite solar cells

Abstract

An object of the present invention is to provide a method for manufacturing a solar cell which is improved in manufacturing cost and ease. The present invention relates to a method for producing a solar cell having a photoelectric conversion layer containing a perovskite compound, the method comprising the steps of: + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + the perovskite compound is a compound selected from the group consisting of cations of methyl cations, methyl cations of ...

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a perovskite solar cell. [Background technology]

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

[0003] As a method for manufacturing a perovskite solar cell, for example, Non-Patent Document 1 discloses a technique that utilizes lead halide template crystallization. The method disclosed in Non-Patent Document 1 includes a step of applying a precursor solution of a perovskite compound to a substrate and a step of drying the applied precursor solution by two-stage heat treatment at different temperatures and in different atmospheres. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Bu et al., Science, 2021, volume 372, pages 1327-1332 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is room for improvement in terms of manufacturing cost and simplicity in the method including two heat treatment steps as disclosed in Non-Patent Document 1. Therefore, an object of the present invention is to provide a method for manufacturing a solar cell with improved manufacturing cost and simplicity. [Means for solving the problem]

[0006] The present inventors discovered that solar cells can be manufactured in a single heat treatment step by controlling the temperature at which the applied precursor solution of a perovskite compound is dried within a specific range, and thus completed the present invention.

[0007] That is, the gist of the present invention is as follows. (1) A method for producing a solar cell having a photoelectric conversion layer containing a perovskite compound, comprising: Formamidinium ion and potassium ion (K + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + applying a precursor solution of a perovskite compound containing at least one metal ion selected from the group consisting of: applying a poor solvent, which has a lower solubility for the perovskite compound than the solvent of the precursor solution, to the surface onto which the precursor solution has been applied; drying the applied precursor solution at a temperature of 100°C or higher and 120°C or lower; A method for manufacturing a solar cell, comprising: (2) The method for producing a solar cell according to (1) above, wherein the solvent of the precursor solution contains N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP). (3) The precursor solution contains a perovskite compound represented by the following formula (1): ABX3(1) (Wherein, A represents a combination of a formamidinium ion and a potassium ion (K + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + ) and at least one metal ion selected from the group consisting of lead ions (Pb 2+ ), tin ions (Sn 2+ ) and combinations thereof, and X is a halogen ion. The method for producing a solar cell according to (1) or (2) above, comprising: (4) The method for producing a solar cell according to any one of (1) to (3) above, wherein the drying step is carried out in an inert gas atmosphere. (5) The method for producing a solar cell according to any one of (1) to (4) above, wherein in the drying step, the heat treatment time is 10 minutes or more and 20 minutes or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for manufacturing a solar cell with improved manufacturing cost and ease. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an example of the structure of a solar cell of the present invention. [Figure 2] 1 is a SEM image of the surface of a perovskite layer obtained by applying the annealing conditions of Non-Patent Document 1. [Figure 3] This is an SEM image of the surface of a perovskite layer obtained by applying the poor solvent method. [Figure 4] 1 is a graph showing the relationship between the annealing temperature and PbI2 / ITO (intensity ratio) for a perovskite layer obtained by applying a poor solvent method. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will now be described in detail.

[0011] The present invention relates to a method for producing a solar cell having a photoelectric conversion layer containing a perovskite compound.

[0012] <Solar cell configuration> First, the structure of the perovskite solar cell (hereinafter also referred to as the solar cell of the present invention) produced by the production method of the present invention will be described in detail. Fig. 1 is a schematic cross-sectional view showing an example of the structure of the solar cell of the present invention.

[0013] As shown in FIG. 1, in one embodiment, a solar cell C of the present invention 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.

[0014] (Photoelectric conversion layer 4) The photoelectric conversion layer 4 is a layer located between the first carrier transport layer 3a and the second carrier transport layer 3b. The photoelectric conversion layer 4 generates charge carriers by receiving light. The charge carriers generated in the photoelectric conversion layer 4 move to either the first carrier transport layer 3a or the second carrier transport layer 3b.

[0015] More specifically, positive charge carriers, i.e., holes, generated in the photoelectric conversion layer 4 are transported to the first electrode layer 2a or the second electrode layer 2b via the layer that corresponds to the hole transport layer, either the first carrier transport layer 3a or the second carrier transport layer 3b. Furthermore, the negative charge carriers, i.e., electrons, generated in the photoelectric conversion layer 4 are transported to the first electrode layer 2a or the second electrode layer 2b via the layer that corresponds to the electron transport layer, either the first carrier transport layer 3a or the second carrier transport layer 3b.

[0016] The photoelectric conversion layer 4 contains a perovskite compound, preferably 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.

[0017] The thickness of the photoelectric conversion layer is usually 100 nm or more and 1000 nm or less.

[0018] A perovskite compound is a compound having a perovskite-type crystal structure. Whether a compound has a perovskite-type crystal structure can be confirmed by, for example, X-ray diffraction measurement.

[0019] The perovskite compound used in the present invention is a formamidinium ion (HC(NH2)2 + :FA) and potassium ions (K + ), rubidium ion (Rb +), cesium ions (Cs + ) and francium ion (Fr + and at least one metal ion selected from the group consisting of:

[0020] The perovskite compound used in the present invention can be represented by, for example, the following formula (1). ABX3(1) (Wherein, A represents a combination of a formamidinium ion and a potassium ion (K + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + ) and at least one metal ion selected from B, B is a divalent cation, and X is a monovalent anion.

[0021] In formula (1), A may further contain another monovalent cation other than the formamidinium ion and the metal ion. The other monovalent cation is, for example, a monovalent organic ammonium ion. Examples of the monovalent organic ammonium ion include CH3NH3 + (Methylammonium ion: MA), C2H5NH3 + , C3H7NH3 + and C4H9NH3 + In one embodiment, A in formula (1) is not a methylammonium ion (MA) in view of the durability of the perovskite compound against high temperatures and light.

[0022] In one embodiment, the at least one metal ion as A in formula (1) is preferably Rb + and Cs + and more preferably Cs + is.

[0023] In one embodiment, in formula (1), B is a divalent metal ion, for example, a lead ion (Pb 2+ ), tin ions (Sn 2+ ) and their combinations. From the viewpoint of durability, B is Pb2+ It is preferable that:

[0024] In one embodiment, in formula (1), X is a halogen ion, for example, a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ) and iodide ion (I - ) and at least one selected from Cl - , Br - and I - is preferred.

[0025] In one embodiment, in formula (1), A is selected from FA and K + , Rb + , Cs + and Fr + and at least one metal ion selected from the group consisting of FA and K. + , Rb + , Cs + and Fr + and B is a monovalent cation consisting of at least one metal ion selected from Pb 2+ , Sn 2+ and combinations thereof, wherein X is a halogen ion.

[0026] In the solar cell obtained by the manufacturing method of the present invention, the crystal grain size of the perovskite compound in the photoelectric conversion layer 4 is controlled within an appropriate range. The crystal grain size of the perovskite compound in the photoelectric conversion layer 4 is usually 300 nm or more and less than 1000 nm, preferably 300 nm or more and 700 nm or less, and more preferably 300 nm or more and 500 nm or less. In the present invention, the crystal grain size of the perovskite compound refers to the average value obtained by measuring the diameters of five crystals randomly selected from three SEM images taken at different locations.

[0027] (First carrier transport layer 3a and second carrier transport layer 3b) The first carrier transport layer 3a receives charge carriers generated in the photoelectric conversion layer 4 and transports the charge carriers to the first electrode layer 2a. When 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. When 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.

[0028] The second carrier transport layer 3b receives charge carriers generated in the photoelectric conversion layer 4 and transports the charge carriers to the second electrode layer 2b. When 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. When 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.

[0029] 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 invention has, in the stated order, a substrate, a cathode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an anode.

[0030] 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 invention has a substrate, an anode, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a cathode, in the stated order.

[0031] The hole transport layer has a function of transporting holes generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As a material for the hole transport layer, known organic or inorganic materials usable for hole transport layers can be used.

[0032] The organic material that can be used as the material for the hole transport layer is not particularly limited, and examples thereof include 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), polyethylenedioxythiophene:polystyrenesulfonic acid (PEDOT:PSS), and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA).

[0033] The inorganic material that can be used as the material for the hole transport layer is not particularly limited, and examples thereof include nickel oxide and copper oxide.

[0034] In the first embodiment of the solar cell of the present invention described above, the materials of the hole transport layer are preferably Spiro-OMeTAD, PTAA, and nickel oxide. In the second embodiment of the solar cell of the present invention, the material of the hole transport layer is preferably PEDOT:PSS, PTAA, and nickel oxide.

[0035] The electron transport layer has a function of transporting electrons generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As a material for the electron transport layer, known organic or inorganic materials usable for electron transport layers can be used.

[0036] The organic material that can be used as the material for the electron transport layer is not particularly limited, and examples thereof include fullerene compounds, phenanthroline derivatives (e.g., bathocuproine), polyethyleneimines, etc. Examples of fullerene compounds include fullerenes (e.g., C60 fullerene, C70 fullerene), derivatives in which a substituent is added to fullerene (e.g., [6,6]-phenyl-C 61 -methyl butyrate (also known as PCBM or

[60] PCBM), [6,6]-phenyl-C 71 -methyl butyrate (also known as PCBM or

[70] PCBM).

[0037] Inorganic materials that can be used as the material for the electron transport layer include titanium oxide, tin oxide, and zinc oxide.

[0038] In the first embodiment of the solar cell of the present invention, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproine, polyethyleneimines, titanium oxide, and tin oxide. In the second embodiment of the solar cell of the present invention, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproine, or polyethyleneimines.

[0039] (First electrode layer 2a and second electrode layer 2b) The first electrode layer 2a is an electrode in contact with the first carrier transport layer 3a, and the second electrode layer 2b is an electrode in contact with the second carrier transport layer 3b.

[0040] The first electrode layer and the second electrode layer can be made of metal materials such as aluminum (Al), silver (Ag), gold (Au), etc., transparent conductive films such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), carbon nanotubes, and other materials known as electrodes for solar cells. The materials for the first electrode layer and the second electrode layer are preferably ITO, IZO, FTO, and Ag.

[0041] (Substrate 1) The substrate 1 is a plate-like or film-like member, and 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.

[0042] The material of the substrate 1 is not particularly limited, and examples thereof include inorganic materials such as glass, organic materials such as polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamideimide, liquid crystal polymer, and cycloolefin polymer, and metal materials such as stainless steel and silicon.

[0043] The substrate 1 may be transparent or opaque. When light is incident from the surface of the substrate, a transparent substrate is used. As a transparent substrate, a substrate made of glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamideimide, or cycloolefin polymer can be used. When light is incident from the opposite side of the substrate, the substrate can be opaque.

[0044] <Solar cell manufacturing method> Next, the method for manufacturing a solar cell of the present invention, i.e., the manufacturing method of the present invention, will be described in more detail. In the method for manufacturing a solar cell of the present invention, for example, a solar cell is manufactured by forming 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 on a substrate 1 in the order listed. The manufacturing method of the present invention is characterized by the film formation step of the photoelectric conversion layer 4, and the film formation steps for the other parts can be performed using methods similar to those used for conventional photoelectric conversion elements.

[0045] Hereinafter, a detailed description will be given of the film-forming step of the photoelectric conversion layer 4. The film-forming step of the photoelectric conversion layer 4 of the present invention includes a step of applying a precursor solution of a perovskite compound to a coating surface (step S1), a step of applying a poor solvent to the coating surface to which the precursor solution has been applied (step S2), and a step of drying the applied precursor solution at a temperature of 100°C or higher and 120°C or lower (step S3).

[0046] In the film formation process of the photoelectric conversion layer 4, first, a precursor solution is applied to a coating surface (step S1). In one embodiment, the surface of the first carrier transport layer 3a corresponds to the coating surface. As described above, the photoelectric conversion element to which the precursor solution is applied can be manufactured by forming the first electrode layer 2a and the first carrier transport layer 3a on the substrate 1 using a known method.

[0047] In step S1 according to this embodiment, the precursor solution is applied to the surface of the first carrier transport layer 3a. The precursor solution applied to the surface of the first carrier transport layer 3a forms a liquid film on the first carrier transport layer.

[0048] The precursor solution refers to a solution containing a perovskite compound as a solute, and can be prepared by dissolving the perovskite compound, a solvent adduct of the perovskite compound, or raw materials for multiple perovskite compounds in a suitable solvent.

[0049] The precursor solution contains formamidinium ions and potassium ions (K + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + and at least one metal ion selected from the group consisting of:

[0050] When the perovskite compound is represented by the above formula (1), the precursor solution can also be prepared by dissolving one or more compounds represented by the following formula (2) and one or more compounds represented by the following formula (3) in an appropriate solvent. In formulas (2) and (3), A, B, and X are as defined for formula (1). AXE (2) BX2(3)

[0051] In one embodiment, the precursor solution contains a perovskite compound represented by the following formula (1): ABX3(1) (Wherein, A represents a combination of a formamidinium ion and a potassium ion (K + ), rubidium ion (Rb + ), cesium ions (Cs + ) and francium ion (Fr + ) and at least one metal ion selected from the group consisting of lead ions (Pb 2+ ), tin ions (Sn 2+) and combinations thereof, and X is a halogen ion. Includes.

[0052] The solvent for the precursor solution is preferably a polar solvent from the viewpoint of solubility of the perovskite compound. Furthermore, the solvent for the precursor solution is preferably an aprotic solvent from the viewpoint of stability of the perovskite compound in the solution. Examples of solvents that can be used as the solvent for the precursor solution include N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), γ-butyrolactone, and mixed solvents containing one or more of these. The solvent for the precursor solution preferably contains DMF and NMP, and more preferably consists of DMF and NMP. When the solvent for the precursor solution contains DMF and NMP, perovskite crystal nucleation and α-phase formation are promoted, improving the power generation performance of the solar cell.

[0053] In step S1 according to the present embodiment, the surface of the first carrier transport layer 3a corresponds to the application surface, but the application surface in step S1 is not limited to the surface of the first carrier transport layer 3a. For example, if the manufactured solar cell C does not have a 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. Furthermore, if the manufactured solar cell C 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. In other words, the application surface in step S1 is appropriately selected depending on the configuration of the manufactured solar cell C. More specifically, the application surface in step S1 is the surface of the manufactured solar cell C that contacts the photoelectric conversion layer 4 on the substrate side.

[0054] The precursor solution can be applied by a known method, and any method can be used as long as it can apply the precursor solution to the surface to be coated in a substantially uniform layer, such as spin coating, inkjet coating, spray coating, blade coating, and die coating.

[0055] From the viewpoint of the stability of the perovskite compound, step S1 is preferably carried out in a dry air atmosphere, more preferably in an inert gas atmosphere. Any inert gas may be used as long as it does not react with the perovskite compound, such as nitrogen or argon.

[0056] In the film formation process of the photoelectric conversion layer 4, after step S1, a poor solvent is applied to the surface coated with the precursor solution (step S2). By performing step S2 according to this embodiment, the poor solvent is added to the liquid film of the precursor solution formed on the surface of the first carrier transport layer 3a in step S1, and a liquid film of the precursor solution containing the poor solvent (i.e., a mixed liquid film of the precursor solution and the poor solvent) is formed. The generation of crystal nuclei of the perovskite compound is promoted in this liquid film. The generated crystal nuclei of the perovskite compound undergo crystal growth through the steps described below to become the photoelectric conversion layer 4. By performing step S2, the amount of crystal nuclei generated increases, allowing the crystal grain size of the perovskite compound to be controlled within an appropriate range. The crystal grain size of the perovskite compound is usually 300 nm or more and less than 1000 nm, preferably 300 nm or more and 700 nm or less, and more preferably 300 nm or more and 500 nm or less.

[0057] Here, the poor solvent is a solvent in which the solubility of the perovskite compound is at least lower than that of the solvent of the precursor solution, and more preferably a solvent in which the perovskite compound cannot substantially dissolve. For example, the poor solvent is a solvent in which the solubility of the perovskite compound at 25°C (weight ratio of solute to 100 g of solvent) is usually less than 1 wt%, preferably less than 0.5 wt%.

[0058] The solvent that can be used as the poor solvent is not particularly limited, and examples thereof include organic solvents such as substituted aliphatic hydrocarbons such as dichloromethane and chloroform; aromatic compounds such as toluene, benzene, chlorobenzene, and tetralin; ethers such as diethyl ether and tetrahydrofuran (THF); alcohols having 3 or more carbon atoms; hydrocarbons having 4 to 10 carbon atoms; and acetic acid. In the present invention, aromatic compounds also include compounds containing an aromatic ring in part. These solvents may be used alone or in combination of two or more as the poor solvent. In one embodiment, the poor solvent is chlorobenzene.

[0059] From the viewpoint of the stability of the perovskite compound, step S2 is preferably carried out in a dry air atmosphere, more preferably in an inert gas atmosphere. Any inert gas may be used as long as it does not react with the perovskite compound, such as nitrogen or argon.

[0060] In step S2, the poor solvent can be applied in the same manner as in the application of the precursor solution in step S1.

[0061] In the film formation process of the photoelectric conversion layer 4, a drying process is performed after step S2, thereby completing the film formation of the photoelectric conversion layer 4 (step S3). By performing step S3 according to this embodiment, the photoelectric conversion layer 4 is formed on the surface of the first carrier transport layer 3a.

[0062] In step S3, the liquid film of the precursor solution containing the poor solvent is dried under predetermined heat treatment conditions to remove the solvent in the liquid film (i.e., the solvent of the precursor solution and the poor solvent). Note that in the manufacturing method of the present invention, step S3 can also be called an annealing step.

[0063] In step S3, the heat treatment temperature is 100°C or higher and 120°C or lower. When the heat treatment temperature is 100°C or higher, the crystal grain size can be sufficiently increased, and the generation of crystal grain boundaries that serve as starting points for carrier recombination is suppressed. Furthermore, when the heat treatment temperature is 120°C or lower, decomposition of the perovskite compound is suppressed.

[0064] In step S3, the heat treatment time can be appropriately selected depending on the heat treatment temperature, and is usually from 5 minutes to 30 minutes, preferably from 10 minutes to 20 minutes.

[0065] From the viewpoint of the stability of the perovskite compound, step S3 is preferably carried out in a dry air atmosphere, more preferably in an inert gas atmosphere. Any inert gas that does not react with the perovskite compound may be used, such as nitrogen or argon.

[0066] As described above, the manufacturing method according to this embodiment is carried out by the poor solvent method, and in the step of drying the applied precursor solution, the heat treatment temperature is controlled to 100°C or higher and 120°C or lower. This configuration allows the solar cell to be manufactured in a single heat treatment step, thereby improving manufacturing costs and simplicity. Furthermore, this configuration improves the power generation performance of the solar cell. [Example]

[0067] The present invention will be described in more detail below using examples, although the technical scope of the present invention is not limited to these examples.

[0068] <Preparing the substrate> An indium tin oxide (ITO) film was formed on a non-alkali glass plate by sputtering, and this was used as the substrate. The substrate was ultrasonically cleaned in 1-propanol and ethanol in that order. Then, the substrate was exposed to ultraviolet light at a 10 mW / cm irradiance using a UV ozone generator. 2 The sample was treated for 10 minutes and then dry washed.

[0069] <Preparation of precursor solution> The predetermined amounts of FAI (formamidinium iodide), CsI, PbI2, PbCl2, NMP, and DMF were added to a screw bottle and dissolved at 60 °C to prepare a precursor solution (composition: 2M FA 0.83 Cs 0.17A solution of PbI3-10% PbCl2-NMP / DMF (1 / 5 volume ratio) was prepared.

[0070] <Perovskite layer deposition> The precursor solution was dropped onto the substrate and coated using a spin coater at 5000 rpm for 50 seconds, and a perovskite layer was formed on the substrate using the method described in Non-Patent Document 1 below or a poor solvent method.

[0071] 1. Annealing conditions in Non-Patent Document 1 Two-stage annealing was performed as described in Non-Patent Document 1 (Science, 2021, Vol. 372, pp. 1327-1332). Specifically, the substrate coated with the precursor solution was annealed at 70°C for 5 minutes in a glove box filled with inert gas (N2), and then the substrate was removed from the glove box and annealed in air at 150°C for 10 minutes.

[0072] 2. Antisolvent method After coating the precursor solution on the substrate, chlorobenzene (a poor solvent) was added dropwise while the spin coater was rotating, and then the substrate was annealed for 15 minutes at a predetermined temperature (70°C, 100°C, 120°C, 130°C, 140°C, 150°C, 160°C, or 190°C) in a glove box filled with inert gas (N2).

[0073] <Evaluation> Surface observation The surface of the annealed perovskite layer was observed under a scanning electron microscope (SEM) at various magnifications to confirm the state of coverage of the perovskite layer on the substrate.

[0074] X-ray diffraction (XRD) measurements The crystallinity of the perovskite compound in the perovskite layer was confirmed using an X-ray diffractometer. Specifically, XRD measurements were performed to determine the PbI2 / ITO intensity ratio.

[0075] Figure 2 shows an SEM image of the surface of the perovskite layer obtained under the annealing conditions of Non-Patent Document 1. As shown in Figure 2, when the annealing conditions of Non-Patent Document 1 were applied, it was confirmed that there were areas of the substrate that were not covered with the perovskite layer and were exposed.

[0076] Figure 3 shows a summary of SEM images of the surface of the perovskite layer obtained using the anti-solvent method. As shown in Figure 3, when the anti-solvent method was used, the perovskite layer completely covered the substrate surface. Also, as shown in Figure 3, as the annealing temperature increased, the crystal grains became larger. The larger the crystal grains, the fewer the crystal grain boundaries, which can suppress carrier recombination. Therefore, in terms of crystal morphology, it is preferable that the annealing temperature be 100°C or higher when using the anti-solvent method.

[0077] Figure 4 shows the relationship between the annealing temperature and the PbI2 / ITO (intensity ratio) for the perovskite layer obtained using the anti-solvent method. As shown in Figure 4, the amount of PbI2 increased as the annealing temperature increased. This is thought to be due to the decomposition of the perovskite crystals by heating. Therefore, from the perspective of crystallinity, it is preferable that the annealing temperature be 120°C or less in the anti-solvent method.

[0078] The above results indicate that in the poor solvent method, the annealing temperature is preferably 100° C. or higher and 120° C. or lower from the viewpoint of crystal morphology and crystallinity. [Explanation of symbols]

[0079] 1: Circuit board 2a: First electrode layer 2b: Second electrode layer 3a: First carrier transport layer 3b: Second carrier transport layer 4: Photoelectric conversion layer C: Solar battery

Claims

1. A method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound, comprising: Formamidinium ion and potassium ion (K ＋ ), rubidium ion (Rb ＋ ), cesium ions (Cs ＋ ) and francium ion (Fr ＋ applying a precursor solution of a perovskite compound containing at least one metal ion selected from the group consisting of: applying a poor solvent, which has a lower solubility for the perovskite compound than the solvent of the precursor solution, to the surface onto which the precursor solution has been applied; drying the applied precursor solution at a temperature of 100°C or higher and 120°C or lower; A method for manufacturing a solar cell, comprising:

2. 2. The method for producing a solar cell according to claim 1, wherein the solvent of the precursor solution contains N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

3. The precursor solution contains a perovskite compound represented by the following formula (1): ABX ３ (1) (Wherein, A represents a combination of a formamidinium ion and a potassium ion (K ＋ ), rubidium ion (Rb ＋ ), cesium ions (Cs ＋ ) and francium ion (Fr ＋ ) and B is a monovalent cation containing at least one metal ion selected from lead ions (Pb ２＋ ), tin ions (Sn ２＋ ) and combinations thereof, and X is a halogen ion. The method for producing a solar cell according to claim 1 or 2, comprising:

4. The method for manufacturing a solar cell according to claim 1 , wherein the drying step is carried out in an inert gas atmosphere.

5. 3. The method for manufacturing a solar cell according to claim 1, wherein the drying step includes a heat treatment time of 10 minutes or more and 20 minutes or less.

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