Method for manufacturing perovskite solar cells

Abstract

The present invention aims to provide a method for manufacturing solar cells that offers improved simplicity and reduced manufacturing costs. [Solution] The present invention relates to a method for manufacturing a solar cell having a photoelectric conversion layer mainly composed of a perovskite compound, comprising the steps of: applying a precursor solution containing the perovskite compound as a solute to a coating surface on a substrate; heating the substrate coated with the precursor solution at a temperature of 110°C to 170°C to form the photoelectric conversion layer on the substrate; and forming a passivation layer on the surface of the photoelectric conversion layer.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a perovskite-type solar cell. [Background technology]

[0002] One type of solar cell known is the perovskite solar cell, in which the main component of the photoelectric conversion layer is a perovskite compound. Patent Document 1 discloses a laminate including a perovskite layer and a surface treatment layer formed on the perovskite layer, and a solar cell including the laminate. In the example of Patent Document 1, the perovskite layer is formed by heating a coated precursor solution of the perovskite compound twice at different temperatures. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-174029 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Methods involving a two-stage heat treatment, such as the one disclosed in Patent Document 1, lead to complicated manufacturing processes and increased manufacturing costs. Therefore, the present invention aims to provide a method for manufacturing solar cells that is simpler and has improved manufacturing costs. [Means for solving the problem]

[0005] The inventors of the present invention have discovered that a solar cell can be manufactured in a single heating step by controlling the temperature at which a substrate coated with a precursor solution is heated within a specific range, thereby completing the present invention.

[0006] In other words, the gist of this invention is as follows: (1) The following formula (1) AMX3(1) (In the formula, A is at least one selected from cesium ions, methylammonium ions, and formamidinium ions. M is a divalent lead ion, X is a halogen ion. A method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound represented by as the main component, A step of applying a precursor solution containing the perovskite compound as a solute to a coating surface on a substrate, The process involves heating the substrate coated with the precursor solution at a temperature of 110°C to 170°C to form the photoelectric conversion layer on the substrate, A step of forming a passivation layer on the surface of the photoelectric conversion layer. A method for manufacturing solar cells, including (2) The method for manufacturing a solar cell according to (1), wherein the step of forming the passivation layer includes applying a solution of ethylenediammonium diiodine to the photoelectric conversion layer. (3) A method for manufacturing a solar cell according to (1) or (2), comprising the step of dropping a poor solvent having less solubility for the perovskite compound than the solvent of the precursor solution onto the substrate coated with the precursor solution before heating the substrate coated with the precursor solution. (4) A method for manufacturing a solar cell according to any one of (1) to (3), wherein the heating time of the substrate coated with the precursor solution is 5 minutes or more and 15 minutes or less. [Effects of the Invention]

[0007] The present invention makes it possible to provide a method for manufacturing solar cells that is simpler and has improved manufacturing costs. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1A is a schematic cross-sectional view showing an example of the structure of the solar cell of the present invention. Figure 1B is a schematic cross-sectional view of the photoelectric conversion layer in the solar cell of the present invention. [Figure 2]Graph showing the relationship between the annealing temperature during the formation of the perovskite layer and the power generation efficiency for a solar cell with a passivation layer (Example). [Figure 3] Graph showing the relationship between the annealing temperature during the formation of the perovskite layer and the power generation efficiency for a solar cell without a passivation layer (Comparative Example). [Figure 4] Graph showing the relationship between the annealing temperature during the formation of the perovskite layer and the PbI2 / ITO (intensity ratio). [Figure 5] SEM image of the surface of the perovskite layer formed with varying annealing temperatures. [Figure 6] SEM cross-sectional image of the perovskite layer formed with varying annealing temperatures.

Mode for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0010] <Structure of the Solar Cell> First, the structure of a perovskite solar cell manufactured by the manufacturing method of the present invention (hereinafter, also referred to as the solar cell of the present invention) will be described. FIG. 1A is a schematic cross-sectional view showing an example of the structure of the solar cell of the present invention. As shown in FIG. 1A, in one embodiment, the 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. These layers may consist of one layer or may consist of two or more layers.

[0011] (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 upon 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.

[0012] 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 hole transport layer of the first carrier transport layer 3a and the second carrier transport layer 3b. Similarly, 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 electron transport layer of the first carrier transport layer 3a and the second carrier transport layer 3b.

[0013] The photoelectric conversion layer 4 mainly contains a perovskite compound. 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.

[0014] The thickness of the photoelectric conversion layer is typically between 100 nm and 1000 nm.

[0015] Perovskite compounds are compounds that have a perovskite-type crystal structure. The presence of a perovskite-type crystal structure in a compound can be confirmed, for example, by X-ray diffraction measurements.

[0016] The perovskite compound used in the present invention can be represented by the following formula (1). AMX3(1) (In the formula, A is a monovalent cation, M is a divalent cation, and X is a monovalent anion.)

[0017] Specifically, the perovskite compound used in the present invention is represented by the following formula (1). AMX3(1) (In the formula, A is cesium ion (Cs + ), methylammonium ion (CH3NH3 + :MA) and formamidinium ion (HC(NH2)2 + At least one selected from :FA) M is divalent lead ion (Pb 2+ ), and X is a halogen ion.)

[0018] In formula (1), A may further contain a monovalent cation other than Cs + , MA and FA. Examples of the other monovalent cation include a monovalent organic ammonium ion, a monovalent amidinium ion and a monovalent metal ion. Examples of the monovalent organic ammonium ion include C2H5NH3 + , C3H7NH3 + and C4H9NH3 + . Examples of the monovalent metal ion include rubidium ion (Rb + ).

[0019] In one embodiment, in formula (1), A is two or more selected from Cs + , MA and FA, preferably three or more including Cs + , MA and FA, and more preferably consists of these three.

[0020] In one embodiment, in formula (1), M may further contain a divalent cation other than Pb 2+ (for example, tin ion (Sn 2+ )). From the viewpoint of durability, M is preferably Pb 2+ .

[0021] In one embodiment, in formula (1), X is at least one selected from fluoride ion (F - ), chloride ion (Cl - ), bromide ion (Br - ) and iodide ion (I - ), and Cl - , Br - and I - are preferred, and Br - and I - are more preferred.

[0022] The solar cell C of the present invention has a passivation layer on the surface of the photoelectric conversion layer 4 opposite to the substrate (the surface on the side of the second carrier transport layer 3b in Figure 1A). Figure 1B is a schematic cross-sectional view of the photoelectric conversion layer in the solar cell of the present invention. As shown in Figure 1B, the photoelectric conversion layer 4 has a passivation layer 4b formed on the surface of a layer (perovskite layer) 4a mainly containing a perovskite compound. In this specification, this structure will also be described as a photoelectric conversion layer 4 having a passivation layer on its surface. The passivation layer has the function of suppressing the adverse effects of crystal defects in the perovskite compound on power generation performance. As will be described later, when the photoelectric conversion layer 4 has a passivation layer on its surface, the power generation performance of the solar cell is improved by heating the photoelectric conversion layer at a specific temperature during film formation.

[0023] The passivation layer is formed, for example, by applying a solution containing the components of the passivation layer to the surface of the photoelectric conversion layer (perovskite layer). The components of the passivation layer are, for example, amines or salts thereof. The amine may be either a monoamine or a polyamine, but polyamines are preferred, and diamines are more preferred. The monoamine or salt thereof may be, for example, a linear or branched alkylamine, a cyclic alkylamine, an aromatic amine or salt thereof (preferably an iodide salt). The diamine or salt thereof may be an alkyldiamine, a cyclic diamine, an aromatic diamine or salt thereof (preferably an iodide salt), for example, an alkyldiamine having 2 to 4 carbon atoms or a salt thereof, and may also be ethylenediamine or a salt thereof, or ethylenediammonium diiodide.

[0024] The thickness of the passivation layer is typically greater than or equal to the thickness of the monolayer but less than or equal to 10 nm.

[0025] (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 these charge carriers to the first electrode layer 2a. If the first carrier transport layer 3a is a hole transport layer (HTL), it transports holes to the first electrode layer 2a. If the first carrier transport layer 3a is an electron transport layer (ETL), it transports electrons to the first electrode layer 2a.

[0026] The second carrier transport layer 3b accepts charge carriers generated in the photoelectric conversion layer 4 and transports these charge carriers to the second electrode layer 2b. If the second carrier transport layer 3b is a hole transport layer, it transports holes to the second electrode layer 2b. If the second carrier transport layer 3b is an electron transport layer, it transports electrons to the second electrode layer 2b.

[0027] 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. 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.

[0028] The hole transport layer has the function of transporting holes generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As the material for the hole transport layer, known organic or inorganic materials usable for hole transport layers can be used. Organic materials that can be used as the material for the hole transport layer are not particularly limited, but include, for example, 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), polyethylenedioxythiophene:polystyrene sulfonic acid (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 3PATAT-C3 (PATAT: phosphonic acid functionalized triazatruxene) (Non-patent literature: Journal of the American Chemical Society, 2023, No. 145, p. 7528). The inorganic materials that can be used as the material for the hole transport layer are not particularly limited, but include, for example, nickel oxide and copper oxide.

[0029] The electron transport layer has the function of transporting electrons generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As the material for the electron transport layer, known organic or inorganic materials usable for electron transport layers can be used. Organic materials that can be used as the material for the electron transport layer are not particularly limited, but include, for example, fullerene compounds, phenanthroline derivatives (e.g., bathocuproine (BCP)), polyethyleneimines, etc. Examples of fullerene compounds include fullerenes (e.g., C60 fullerene, C70 fullerene) and derivatives of fullerene with substituents (e.g., [6,6]-phenyl-C 61 -Methyl butyrate (also known as PCBM or

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

[70] PCBM). Inorganic materials that can be used as materials for the electron transport layer include titanium dioxide, tin oxide, zinc oxide, etc.

[0030] (First electrode layer 2a and second electrode layer 2b) As materials for the first and second electrode layers, metal materials such as aluminum (Al), silver (Ag), and gold (Au), transparent conductive films such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO), and carbon nanotubes, materials known as electrodes for solar cells can be used. Preferably, the materials for the first and second electrode layers are ITO, IZO, FTO, and Ag.

[0031] (Circuit board 1) The substrate 1 is a plate-shaped or film-shaped component. The material of the substrate is not particularly limited and includes, for example, inorganic materials such as glass, organic materials such as polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, liquid crystal polymer, and cycloolefin polymer, and metallic materials such as stainless steel and silicon. The substrate may be transparent or opaque. A transparent substrate is used when light is incident on the surface of the substrate.

[0032] <Method of manufacturing solar cells> Next, the method for manufacturing the solar cell of the present invention, that is, the manufacturing method of the present invention, will be described in more detail. In the method for manufacturing the solar cell of the present invention, for example, a solar cell is manufactured by depositing 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 described above. The manufacturing method of the present invention is characterized by the film deposition process of the photoelectric conversion layer 4, and the film deposition processes for the other parts can be carried out using the same methods as conventional photoelectric conversion elements.

[0033] The film formation process for the photoelectric conversion layer 4 will now be described in detail. As mentioned above, the photoelectric conversion layer 4 of the present invention has a passivation layer on its surface. The film formation process for the photoelectric conversion layer 4 of the present invention includes a step of applying a precursor solution to a coating surface on a substrate (step S1), a step of heating the substrate coated with the precursor solution at a temperature of 110°C to 170°C to form a photoelectric conversion layer on the substrate (step S3), and a step of forming a passivation layer on the surface of the photoelectric conversion layer (step S4). The film formation process for the photoelectric conversion layer 4 of the present invention may include a step of dropping a poor solvent onto the substrate coated with the precursor solution (step S2) between steps S1 and S3.

[0034] In the film formation process for the photoelectric conversion layer 4, first, a precursor solution is applied to the coating surface on the substrate (step S1). In this invention, the "coating surface on the substrate" does not refer only to the surface of a layer directly laminated on the substrate, but other layers may exist between the substrate and the layer having the coating surface. In one embodiment, the surface of the first carrier transport layer 3a corresponds to the coating surface.

[0035] 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.

[0036] A precursor solution refers to a solution containing a perovskite compound as a solute. Perovskite compounds are as previously described in relation to solar cells. Precursor solutions can be prepared by dissolving a perovskite compound, a solvent adduct of a perovskite compound, or the raw materials of multiple perovskite compounds in a suitable solvent.

[0037] When the perovskite compound is represented by formula (1) above, the precursor solution can also be prepared by dissolving one or more compounds represented by formula (2) below and one or more compounds represented by formula (3) below in a suitable solvent. In formulas (2) and (3), A, M, and X are as defined for formula (1). AX (2) MX2(3)

[0038] Examples of solvents that can be used as solvents 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. It is preferable that the solvent contains DMF and DMSO, and more preferably that it consists of DMF and DMSO.

[0039] In step S1 according to this embodiment, the surface of the first carrier transport layer 3a was the coating surface, but the coating surface in step S1 is appropriately selected according to the configuration of the solar cell C after manufacturing. The coating surface in step S1 is the surface in the solar cell C after manufacturing that the photoelectric conversion layer 4 is in contact with on the substrate side.

[0040] Any method can be used to apply the precursor solution to the coating surface, as long as it allows for the application of the precursor solution in a substantially uniform layer. Examples include spin coating, inkjet, spray, blade coating, and die coating.

[0041] Step S1 is preferably carried out under a dry air atmosphere, and more preferably under an inert gas atmosphere, from the viewpoint of the stability of the perovskite compound. Examples of inert gases include nitrogen and argon.

[0042] In the film formation process for the photoelectric conversion layer 4, a step (step S2) of dropping a poor solvent onto a substrate coated with the precursor solution may be performed between steps S1 and S3. That is, the manufacturing method of the present invention may include a step of dropping a poor solvent onto a substrate coated with the precursor solution before heating the substrate coated with the precursor solution. By performing step S2, the poor solvent is added to the liquid film of the precursor solution formed 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. In this liquid film, the formation of crystal nuclei of the perovskite compound is promoted. The formed crystal nuclei of the perovskite compound undergo crystal growth through the steps described later, and become the photoelectric conversion layer 4.

[0043] Here, a poor solvent is a solvent in which the solubility of the perovskite compound is at least less than that of the solvent in the precursor solution, and more preferably a solvent in which the perovskite compound is substantially insoluble. A poor solvent is, for example, a solvent in which the solubility of the perovskite compound at 25°C (weight ratio of solute to 100g of solvent) is usually less than 1% by weight, preferably less than 0.5% by weight.

[0044] The solvents that can be used as poor solvents are not particularly limited, but include, for example, 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 organic solvents such as acetic acid. In this invention, aromatic compounds also include compounds that partially contain an aromatic ring. These poor solvents may be used individually or in combination of two or more. In one embodiment, the poor solvent is chlorobenzene.

[0045] Step S2 is preferably carried out under a dry air atmosphere, and more preferably under an inert gas atmosphere, from the viewpoint of the stability of the perovskite compound. Examples of inert gases include nitrogen and argon.

[0046] In the film formation process for the photoelectric conversion layer 4, after step S1, or after step S2 if it is performed, a heat treatment is performed to form the photoelectric conversion layer on the surface of the first carrier transport layer 3a on the substrate (step S3).

[0047] In step S3, the liquid film of the precursor solution or (if step S2 has been performed) the mixed liquid film of the precursor solution and the poor solvent is heated to a predetermined temperature to remove the solvent from the liquid film. In the manufacturing method of the present invention, step S3 can also be called the annealing step. Furthermore, the heat treatment in step S3 is performed in one stage.

[0048] In step S3, the heating temperature is between 110°C and 170°C. A heating temperature of 110°C or higher allows for sufficiently large crystal grain sizes, suppressing the formation of grain boundaries that serve as starting points for carrier recombination. Furthermore, a heating temperature of 170°C or lower suppresses the decomposition of the perovskite compound. Therefore, a heating temperature between 110°C and 170°C improves the power generation performance of the solar cell.

[0049] In step S3, the heating time can be appropriately selected according to the heating temperature. The heating time is usually between 1 minute and 30 minutes, and preferably between 5 minutes and 15 minutes.

[0050] Step S3 is preferably carried out under a dry air atmosphere, and more preferably under an inert gas atmosphere, from the viewpoint of the stability of the perovskite compound. Examples of inert gases include nitrogen and argon.

[0051] In the film deposition process for the photoelectric conversion layer 4, following step S3, a step (step S4) is performed to deposit a passivation layer on the surface of the photoelectric conversion layer. By performing step S4, a passivation layer is formed on the surface of the photoelectric conversion layer, and the manufacturing of a photoelectric conversion layer having a passivation layer on its surface is completed.

[0052] The passivation layer can be formed by known methods, for example, by applying a solution (coating solution) containing the components of the passivation layer to the surface of the photoelectric conversion layer. The components of the passivation layer are as described above for solar cells. In one embodiment, the step of forming the passivation layer includes applying a solution containing ethylenediammonium diiodide to the photoelectric conversion layer.

[0053] Examples of solvents for the solution containing the components of the passivation layer include alcohols (such as isopropyl alcohol (IPA)) and aromatic hydrocarbons (such as toluene). In one embodiment, the solvent is a mixture of alcohol and aromatic hydrocarbons, and may be a mixture of IPA and toluene.

[0054] In step S4, the coating solution can be applied by known methods. Examples of coating methods include spin coating, inkjet, spray, blade coating, and die coating.

[0055] In step S4, a drying treatment may be performed as needed.

[0056] Step S4 is preferably carried out under a dry air atmosphere, and more preferably under an inert gas atmosphere, from the viewpoint of the stability of the perovskite compound contained in the photoelectric conversion layer. Examples of inert gases include nitrogen and argon.

[0057] As described above, the manufacturing method according to this embodiment has a passivation layer on the surface of the photoelectric conversion layer, and the heating temperature during film formation of the photoelectric conversion layer (perovskite layer) is controlled to be between 110°C and 170°C. With this configuration, solar cells can be manufactured in a single heating process, thus improving simplicity and manufacturing costs. Furthermore, with this configuration, the power generation performance of the solar cell is improved. [Examples]

[0058] The present invention will be described in more detail below using examples. However, the technical scope of the present invention is not limited to these examples.

[0059] <Material> Substrate: A glass plate with a photolithographed ITO film (transparent conductive film) formed on its surface. Hole transport layer: 3PATAT-C3 Raw materials for perovskite compounds: CsI, FAI (formamidinium iodide), MABr (methylammonium bromide), PbI2, PbBr2 Passivation layer: Ethylenediammonium diiodine (EDAI2) Electron transport layer: C60 fullerene, BCP

[0060] <Fabrication of solar cells> A solar cell with a passivation layer on the surface of a perovskite layer was fabricated using the following procedure. Steps 2 onward were performed inside a glove box filled with N2.

[0061] 1. Prepare the circuit board. The substrate was immersed in a cleaning solution, cleaned in an ultrasonic cleaner, rinsed with pure water, and dried. Then, the substrate was pre-baked at 150°C and subjected to atmospheric pressure plasma treatment. 2. Deposition of the hole transport layer 1.42 mg (0.0020 mmol) of 3PATAT-C3 was dissolved in 2 mL of DMF by stirring at 70°C to prepare a 1 mM (mmol / L) solution, which was filtered (0.45 μm pore size) before application. This solution was spin-coated onto an ITO film on a substrate at 3000 rpm for 30 seconds, and then annealed at 120°C for 10 minutes to form a hole transport layer. 3. Deposition of the perovskite layer 48.8 mg (0.19 mmol) of CsI, 60.0 mg (0.54 mmol) of MABr, 497.4 mg (2.89 mmol) of FAI, 267.6 mg (0.18 mmol) of PbBr, and 21581 mg (3.34 mmol) of PbI were dissolved in 720 μL of DMSO and 2420 μL of DMF by stirring at 70°C to prepare a 1.15 M (mol / L) solution, which was filtered (pore size 0.45 μm) before application. This solution was applied to the hole transport layer by a first-stage spin coating at 1000 rpm for 10 seconds, followed by a second-stage spin coating at 3000 rpm for 20 seconds. 300 μL of chlorobenzene (poor solvent) was added dropwise 4 seconds before the end of the second-stage spin coating. Subsequently, the perovskite layer was deposited by annealing at a predetermined annealing temperature (57°C, 87°C, 117°C, 147°C, 167°C, or 197°C) for 10 minutes. 4. Deposition of the passivation layer EDAI 21.0 mg (315.92 mmol) was dissolved in 1000 μL of IPA and 1000 μL of toluene by stirring at 70°C, and the mixture was filtered (pore size 0.45 μm) before application. This solution was spin-coated onto a perovskite layer at 4000 rpm for 20 seconds to deposit a passivation layer. 5. Formation of electron transport layer C60 fullerene (20 nm thick) and BCP (8 nm thick) were deposited on the passivation layer by vacuum deposition. 6. Deposition of the electrode layer Ag (100 nm thick) was deposited on the electron transport layer by vacuum deposition and then patterned using a metal mask.

[0062] A solar cell without a passivation layer on the surface of the perovskite layer was fabricated in the same manner as above, except that the deposition of the passivation layer in step 4 was not performed.

[0063] <Rating> IV measurement IV measurements were performed on solar cells with a passivation layer (Example) and solar cells without a passivation layer (Comparative Example), which were fabricated by varying the annealing temperature during perovskite layer deposition. Specifically, a solar simulator (Spectrometer Co., Ltd. SMO-250III, light intensity 100 mW / cm²) combined with an AM1.5G equivalent air mass filter was used. 2 The light was applied, and the voltage and current were measured using a source meter (Keithley Model 2400) to determine the power generation efficiency.

[0064] X-ray diffraction (XRD) measurement XRD measurements were performed on solar cells with a passivation layer, fabricated by varying the annealing temperature during perovskite layer deposition. The sample used for measurement was a laminate with the passivation layer deposited. Specifically, XRD measurements were performed using an X-ray diffractometer to determine the PbI2 / ITO (intensity ratio).

[0065] Surface and cross-sectional observation Surface and cross-sectional observations were performed using a scanning electron microscope (SEM) on solar cells with a passivation layer, fabricated by varying the annealing temperature during perovskite layer deposition. The measurement samples used were laminates with the passivation layer deposited.

[0066] Figure 2 shows the relationship between the annealing temperature during perovskite layer deposition and power generation efficiency for a solar cell with a passivation layer (example). Figure 3 shows the relationship between the annealing temperature during perovskite layer deposition and power generation efficiency for a solar cell without a passivation layer (comparative example).

[0067] As shown in Figure 2, in solar cells with a passivation layer, the power generation efficiency of the solar cell improved within the annealing temperature range of 110°C to 170°C during the deposition of the perovskite layer. On the other hand, as shown in Figure 3, in solar cells without a passivation layer, the power generation efficiency of the solar cell decreased within the annealing temperature range of 110°C or higher during the deposition of the perovskite layer.

[0068] Figure 4 shows the relationship between the annealing temperature during perovskite layer deposition and the PbI2 / ITO (intensity ratio). As shown in Figure 4, PbI2 increased exponentially with increasing annealing temperature. PbI2 is a decomposition product of the perovskite compound. In solar cells with a passivation layer, it was suggested that a low annealing temperature is preferable from the viewpoint of suppressing the decomposition of the perovskite compound.

[0069] Figure 5 shows a summary of surface SEM images of perovskite layers deposited at different annealing temperatures. Figure 6 shows a summary of cross-sectional SEM images of perovskite layers deposited at different annealing temperatures. As shown in Figure 5, the crystal grain size increased with increasing annealing temperature. Also, as shown in Figure 6, as the annealing temperature increased, the number of crystal grains in the film thickness direction decreased from 2 to 1, along with the increase in crystal grain size. Larger crystal grain sizes suppress the formation of crystal grain boundaries, which are the starting points for carrier recombination. Therefore, in solar cells with a passivation layer, it is suggested that a higher annealing temperature is preferable from the viewpoint of crystal grain size.

[0070] Based on these results, it is considered that in solar cells with a passivation layer, when the annealing temperature during perovskite layer deposition is within the range of 110°C to 170°C, the balance between suppressing the decomposition of the perovskite compound and suppressing the formation of grain boundaries is optimized, resulting in improved power generation efficiency of the solar cell. [Explanation of Symbols]

[0071] 1: Substrate, 2a: First electrode layer, 2b: Second electrode layer, 3a: First carrier transport layer, 3b: Second carrier transport layer, 4: Photoelectric conversion layer, 4a: Perovskite layer, 4b: Passivation layer, C: Solar cell

Claims

1. The following formula (1) AMX ３ (1) (In the formula, A is at least one selected from cesium ions, methylammonium ions, and formamidinium ions. M is a divalent lead ion, X is a halogen ion. A method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound represented by as the main component, A step of applying a precursor solution containing the perovskite compound as a solute to a coating surface on a substrate, The process involves heating the substrate coated with the precursor solution at a temperature of 110°C to 170°C to form the photoelectric conversion layer on the substrate, A step of forming a passivation layer on the surface of the photoelectric conversion layer. A method for manufacturing solar cells, including

2. The method for manufacturing a solar cell according to claim 1, wherein the step of forming the passivation layer includes applying a solution of ethylenediammonium diiodide to the photoelectric conversion layer.

3. A method for manufacturing a solar cell according to claim 1 or 2, comprising the step of dropping a poor solvent having less solubility for the perovskite compound than the solvent of the precursor solution onto the substrate coated with the precursor solution before heating the substrate coated with the precursor solution.

4. A method for manufacturing a solar cell according to claim 1 or 2, wherein the heating time for the substrate coated with the precursor solution is 5 minutes or more and 15 minutes or less.

Images