Method for manufacturing perovskite solar cell

Abstract

The purpose of the present invention is to provide a method for manufacturing a solar cell, the method being improved in manufacturing cost and simplicity. The present invention relates to a method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound, comprises: a step for applying a precursor solution of a perovskite compound, which contains formamidine ions and at least one metal ion selected from the group consisting of potassium ions (K +), rubidium ions (Rb +), cesium ions (Cs +) and francium ions (Fr +), to an application surface; and a step for drying the applied precursor solution at a temperature of 130-160 DEG C (inclusive) in an inert gas atmosphere.

Description

Technical Field

[0001] This invention relates to a method for manufacturing perovskite solar cells. Background Technology

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

[0003] As a method for manufacturing perovskite solar cells, for example, Non-Patent Document 1 discloses a technique for crystallization using a lead halide template. The method disclosed in Non-Patent Document 1 includes: a step of coating a substrate with a precursor solution of a perovskite compound; and a step of drying the coated precursor solution by a two-step heat treatment with different temperatures and atmospheres.

[0004] Existing technical documents

[0005] Non-patent literature

[0006] Non-patent literature 1: Bu et al., Science, 2021, Vol. 372, pp. 1327-1332 Summary of the Invention

[0007] However, the method disclosed in Non-Patent Document 1, which includes a two-step heat treatment process, has room for improvement in terms of manufacturing cost and ease of use. Therefore, the object of the present invention is to provide a method for manufacturing a solar cell with improved manufacturing cost and ease of use.

[0008] The inventors discovered that by controlling the drying temperature of the precursor solution of the coated perovskite compound within a specific range, solar cells can be manufactured through a one-step heat treatment, thus completing the present invention.

[0009] That is, the main idea of ​​this invention is as follows.

[0010] (1) A method for manufacturing a solar cell, comprising:

[0011] Will contain formamiditin Ions and those selected from potassium ions (K ions) + ), rubidium ions (Rb + ), cesium ions (Cs) + ) and francium ions (Fr + The process of coating a precursor solution of at least one metal ion of a perovskite compound onto a coating surface, and

[0012] The process of drying the coated precursor solution in an inactive gas atmosphere at a temperature of 130°C or higher and 160°C or lower.

[0013] (2) The method for manufacturing a solar cell according to (1) above, wherein the solvent of the precursor solution comprises N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

[0014] (3) The method for manufacturing a solar cell according to (1) or (2) above, wherein the precursor solution contains a perovskite compound represented by the following formula (1).

[0015] ABX3(1)

[0016] (In the formula, A represents the amount of formamidinium) Ions and those selected from potassium ions (K ions) + ), rubidium ions (Rb + ), cesium ions (Cs) + ) and francium ions (Fr + B is a monovalent cation of at least one metal ion in the group consisting of lead ions (Pb). 2+ ), tin ions (Sn) 2+ (and their combinations, where X is a halide ion.)

[0017] (4) The method for manufacturing a solar cell according to any one of (1) to (3) above, wherein, in the drying process, the heat treatment time is 10 minutes or more and 20 minutes or less.

[0018] According to the present invention, a method for manufacturing solar cells with improved manufacturing costs and ease of use can be provided. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view illustrating an example of the structure of the solar cell of the present invention.

[0020] Figure 2 The image shows a surface SEM image of the perovskite layer obtained by applying the annealing conditions described in Non-Patent Document 1.

[0021] Figure 3 It is a surface SEM image of the perovskite layer obtained by one-step annealing at a specified temperature.

[0022] Symbol Explanation

[0023] 1: Substrate

[0024] 2a: First electrode layer

[0025] 2b: Second electrode layer

[0026] 3a: First carrier transport layer

[0027] 3b: Second carrier transport layer

[0028] 4: Photoelectric conversion layer

[0029] C: Solar cell Detailed Implementation

[0030] The preferred embodiments of the present invention will be described in detail below.

[0031] This invention relates to a method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound.

[0032] <Composition of a Solar Cell>

[0033] First, the structure of the perovskite solar cell (hereinafter also referred to as the solar cell of the present invention) manufactured by the manufacturing method of the present invention will be described in detail. Figure 1 This is a schematic cross-sectional view illustrating an example of the structure of the solar cell of the present invention.

[0034] like Figure 1 As shown, 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.

[0035] (Photoelectric conversion layer 4)

[0036] The photoelectric conversion layer 4 is 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.

[0037] More specifically, the 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 through the equivalent hole transport layers in the first charge carrier transport layer 3a and the second charge carrier transport layer 3b.

[0038] In addition, 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 through the layers equivalent to electron transport layers in the first charge carrier transport layer 3a and the second charge carrier transport layer 3b.

[0039] 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 typically 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.

[0040] The thickness of the photoelectric conversion layer is typically above 100nm and below 1000nm.

[0041] Perovskite compounds are compounds with 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.

[0042] The perovskite compound used in this invention contains formamidinium. Ion (HC(NH2)2) + :FA) and selected from potassium ions (K + ), rubidium ions (Rb + ), cesium ions (Cs) + ) and francium ions (Fr + At least one metal ion in ).

[0043] The perovskite compounds used in this invention can be represented, for example, by the following formula (1).

[0044] ABX3(1)

[0045] (In the formula, A represents the amount of formamidinium) Ions and those selected from potassium ions (K ions) + ), rubidium ions (Rb + ), cesium ions (Cs) + ) and francium ions (Fr + (The following is a list of metal ions, with B being a monovalent cation, B being a divalent cation, and X being a monovalent anion.)

[0046] In equation (1), A may further include formamidin. Other monovalent cations besides the aforementioned metal ions. Other monovalent cations include, for example, monovalent organic ammonium ions. Examples of monovalent organic ammonium ions include CH3NH3. + (Ammonium methyl ion: MA), C2H5NH3 + C3H7NH3 + and C4H9NH3 + In one embodiment, from the viewpoint of the durability of perovskite compounds against high temperatures and light, A in formula (1) is not a carbamate ion (MA).

[0047] In one embodiment, at least one metal ion, which is A in formula (1), is preferably Rb. + and Cs + Cs is preferred. + .

[0048] In one embodiment, in formula (1), B is a divalent metal ion, such as lead ion (Pb). 2+ ), tin ions (Sn) 2 + ) and their combinations. From a durability point of view, B is preferably Pb.2+ .

[0049] In one embodiment, X in formula (1) is a halide ion, for example, a fluoride ion selected from fluoride ions (F... - ), chloride ions (Cl) - ), bromide ions (Br) - ) and iodide ions (I - At least one of the following, preferably Cl - ,Br - and I - .

[0050] In one implementation, in equation (1), A is a combination of FA and K. + 、Rb + Cs + and Fr + The monovalent cation of at least one metal ion in the cation, preferably A is composed of FA and K. + 、Rb + Cs + and Fr + The monovalent cation consists of at least one metal ion, B is selected from Pb. 2+ Sn 2+ And their combinations, where X is a halide ion.

[0051] (First carrier transport layer 3a and second carrier transport layer 3b)

[0052] The first charge 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.

[0053] 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.

[0054] 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.

[0055] The second charge carrier transport layer 3b receives the charge carriers generated in the photoelectric conversion layer 4 and transports these charge carriers to the second electrode layer 2b.

[0056] 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.

[0057] 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.

[0058] 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 sequentially comprises a substrate, a cathode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an anode.

[0059] Furthermore, 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 sequentially comprises a substrate, an anode, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a cathode.

[0060] The hole transport layer has the function of transporting holes generated by photoelectric conversion by the photoelectric conversion layer to the first electrode layer or the second electrode layer. Known organic or inorganic materials suitable for hole transport layers can be used as the material for the hole transport layer.

[0061] There are no particular limitations on the organic materials that can be used as hole transport layers, such as 2,2',7,7'-tetra-(N,N-di-4-methoxyphenylamino)-9,9'-spirobisfluorene (Spiro-OMe TAD), poly(ethylene dioxythiophene: polystyrene sulfonic acid) (PEDOT:PSS), and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA).

[0062] There are no particular limitations on the inorganic materials that can be used as hole transport layers; examples include nickel oxide and copper oxide.

[0063] In the first embodiment of the solar cell of the present invention described above, the preferred material for the hole transport layer is Spiro-OMeTAD, PTAA, and nickel oxide.

[0064] Furthermore, in the second embodiment of the solar cell of the present invention described above, the material of the hole transport layer is preferably PEDOT:PSS, PTAA, and nickel oxide.

[0065] The electron transport layer functions to transport electrons generated by photoelectric conversion by the photoelectric conversion layer to the first electrode layer or the second electrode layer. Known organic or inorganic materials suitable for electron transport layers can be used as the material for the electron transport layer.

[0066] Organic materials suitable for use as electron transport layers are not particularly limited, and examples include fullerene compounds, phenanthroline derivatives (e.g., copper sulfate), and polyethyleneimine compounds. Examples of fullerene compounds include fullerenes (e.g., C60 fullerenes, C70 fullerenes) and derivatives of fullerenes with added substituents (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) etc.

[0067] Inorganic materials that can be used as electron transport layers include titanium oxide, tin oxide, and zinc oxide.

[0068] In the first embodiment of the solar cell of the present invention described above, the preferred material for the electron transport layer is fullerene, PCBM, copper bath, polyethyleneimine, titanium dioxide, and tin oxide.

[0069] Furthermore, in the second embodiment of the solar cell of the present invention described above, the material of the electron transport layer is preferably fullerene, PCBM, copper bath, and polyethyleneimine.

[0070] (First electrode layer 2a and second electrode layer 2b)

[0071] The first electrode layer 2a is an electrode that contacts the first carrier transport layer 3a. The second electrode layer 2b is an electrode that contacts the second carrier transport layer 3b.

[0072] Materials used for the first and second electrode layers include metals 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, all known materials for solar cell electrodes. Preferably, the materials for the first and second electrode layers are ITO, IZO, FTO, and Ag.

[0073] (Substrate 1)

[0074] The substrate 1 is a plate-shaped or film-shaped component 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.

[0075] The material of substrate 1 is not particularly limited, and examples include inorganic materials such as glass, polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, liquid crystal polymer, cyclic olefin polymer, and other organic materials, as well as metal materials such as stainless steel and silicon.

[0076] Substrate 1 can be either transparent or opaque. A transparent substrate is used when light is incident from the surface of the substrate. As a transparent substrate, a substrate made of glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, or a cyclic olefin polymer can be used. Alternatively, the substrate can be opaque when light is incident from the side opposite to the substrate.

[0077] <Methods for Manufacturing Solar Cells>

[0078] Next, the manufacturing method of the solar cell of the present invention will be described in more detail. In the manufacturing method of the solar cell of the present invention, for example, 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 are sequentially formed on a substrate 1, thereby manufacturing a solar cell. The manufacturing method of the present invention is characterized in the film-forming process of the photoelectric conversion layer 4; the film-forming processes for the remaining portions can be performed using the same methods as conventional photoelectric conversion elements.

[0079] The following describes in detail the film formation process of the photoelectric conversion layer 4. The film formation process of the photoelectric conversion layer 4 of the present invention includes: a process of coating a precursor solution of a perovskite compound onto a coating surface (process S1); and a process of drying the coated precursor solution under an inactive gas atmosphere at a temperature of 130°C or higher and 160°C or lower (process S2).

[0080] In the film formation process of the photoelectric conversion layer 4, firstly, a precursor solution is coated onto the coating surface (process S1). In one embodiment, the surface of the first carrier transport layer 3a corresponds to the coating surface.

[0081] As described above, the photoelectric conversion element coated with the precursor solution can be manufactured by forming a first electrode layer 2a and a first carrier transport layer 3a on a substrate 1 using a known method.

[0082] In step S1 of this embodiment, a precursor solution is coated onto the surface of the first carrier transport layer 3a. The precursor solution coated onto the surface of the first carrier transport layer 3a forms a liquid film on the first carrier transport layer.

[0083] A precursor solution is a solution containing a perovskite compound as a solute. Precursor solutions can be prepared by dissolving a perovskite compound, a solvation adduct of a perovskite compound, or a mixture of perovskite compounds in a suitable solvent.

[0084] The precursor solution contains formamidin. Ions and those selected from potassium ions (K ions) + ), rubidium ions (Rb + ), cesium ions (Cs)+ ) and francium ions (Fr + Perovskite compounds containing at least one metal ion.

[0085] When the perovskite compound is represented by formula (1) above, the precursor solution can also be prepared by dissolving one or more of the compounds represented by formula (2) below and one or more of the compounds represented by formula (3) below in a suitable solvent. In formulas (2) and (3), A, B and X are as defined in formula (1).

[0086] AX (2)

[0087] BX2 (3)

[0088] In one embodiment, the precursor solution comprises a perovskite compound represented by the following formula (1).

[0089] ABX3(1)

[0090] (In the formula, A represents the amount of formamidinium) Ions and those selected from potassium ions (K ions) + ), rubidium ions (Rb + ), cesium ions (Cs) + ) and francium ions (Fr + B is a monovalent cation of at least one metal ion in the group consisting of lead ions (Pb). 2+ ), tin ions (Sn) 2+ (and their combinations, where X is a halide ion.)

[0091] From the viewpoint of solubility of the perovskite compound, the solvent of the precursor solution is preferably a polar solvent. Furthermore, from the viewpoint of stability of the perovskite compound in solution, the solvent of the precursor solution is preferably an aprotic solvent. Examples of solvents that can be used as 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 of the precursor solution preferably contains DMF and NMP, and more preferably consists of DMF and NMP. If the solvent of the precursor solution contains DMF and NMP, perovskite nucleation and α-phase formation are promoted, thus improving the power generation performance of the solar cell.

[0092] It should be noted that in step S1 of this embodiment, the surface of the first carrier transport layer 3a is equivalent to the coating surface, but the coating 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 coated on the first electrode layer 2a, and the surface of the first electrode layer 2a is equivalent to the coating surface. Furthermore, if the manufactured solar cell C has other layers between the photoelectric conversion layer 4 and the first carrier transport layer 3a, the precursor solution is coated on these other layers, and the surface of these other layers is equivalent to the coating surface. That is, the coating surface in step S1 is appropriately selected according to the configuration of the manufactured solar cell C. More specifically, the coating surface in step S1 is the surface of the manufactured solar cell C that contacts the substrate side.

[0093] The precursor solution can be coated using known methods. Any method can be used as long as it can be applied to the coating surface in a substantially uniform layer, such as spin coating, inkjet coating, spray coating, doctor blade coating, and mold coating.

[0094] From the viewpoint of the stability of perovskite compounds, step S1 is preferably carried out in a dry air atmosphere, and more preferably in an inert gas atmosphere. As the inert gas, any gas that does not react with the perovskite compound can be used, such as nitrogen, argon, etc.

[0095] In the film formation process of the photoelectric conversion layer 4, a drying process is performed after process S1, thereby completing the film formation of the photoelectric conversion layer 4 (process S2). By performing process S2 of this embodiment, the photoelectric conversion layer 4 is formed on the surface of the first carrier transport layer 3a.

[0096] In step S2, the liquid film of the precursor solution coated in step S1 is dried under specified heat treatment conditions to remove the solvent from the liquid film. It should be noted that in the manufacturing method of the present invention, step S2 can also be referred to as an annealing step.

[0097] In step S2, the liquid film of the precursor solution coated in step S1 is dried at a temperature of 130°C or higher and 160°C or lower. If the heat treatment temperature is 130°C or higher, the coverage of the photoelectric conversion layer over the underlying layer is increased, thus improving the power generation performance of the solar cell and preventing short circuits. If the heat treatment temperature is 160°C or lower, the decomposition of the perovskite compound is suppressed, thus improving the power generation performance of the solar cell. It should be noted that the heat treatment temperature can be, for example, 100°C or higher and 180°C or lower, provided that the coverage of the photoelectric conversion layer over the underlying layer is sufficiently high and the decomposition of the perovskite compound is suppressed.

[0098] In step S2, the heat treatment time can be appropriately selected based on the heat treatment temperature. The heat treatment time is typically 5 minutes or more and 30 minutes or less, preferably 10 minutes or more and 20 minutes or less.

[0099] From the perspective of the stability of perovskite compounds, process S2 is carried out in an inactive gas atmosphere.

[0100] As an inert gas, any gas that does not react with perovskite compounds can be used, such as nitrogen or argon.

[0101] As explained above, in the manufacturing method of this embodiment, the heat treatment temperature is controlled between 130°C and 160°C during the drying process of the coated precursor solution. With this configuration, solar cells can be manufactured in a single heat treatment step, thus improving manufacturing cost and ease of use. Furthermore, with this configuration, the power generation performance of the solar cell is improved.

[0102] Example

[0103] The present invention will be further described in detail below using examples. However, the technical scope of the present invention is not limited to these examples.

[0104] <Substrate Preparation>

[0105] Indium tin oxide (ITO) films were sputtered onto an alkali-free glass plate and used as substrates. The substrates were then ultrasonically cleaned sequentially with 1-propanol and ethanol. Finally, a UV ozone generator was used with an ultraviolet irradiation of 10 mW / cm². 2 The substrate is processed for 10 minutes for dry cleaning.

[0106] <Preparation of Precursor Solution>

[0107] The specified amount of FAI (formamidin) was respectively Iodides), CsI, PbI2, PbCl2, NMP, and DMF were added to a screw-top flask and dissolved at 60°C to prepare a precursor solution (composition: 2MFA). 0.83 Cs 0.17 PbI3-10%PbCl2-NMP / DMF (1 / 5 volume ratio)

[0108] <Perovskite film formation>

[0109] The precursor solution was dropped onto the substrate and coated using a spin coater at 5000 rpm for 50 seconds. Annealing was then performed under the conditions specified below to form a perovskite layer on the substrate.

[0110] 1. Annealing conditions of non-patent document 1

[0111] As described in Non-Patent Literature 1 (Science, 2021, Vol. 372, pp. 1327-1332), a two-step annealing process is performed. Specifically, the substrate is annealed at 70°C for 5 minutes in a glove box filled with an inert gas (N2), and then removed from the glove box and annealed at 150°C for 10 minutes in the atmosphere.

[0112] 2. One-step annealing

[0113] The substrate coated with the precursor solution was annealed for 15 minutes at a specified temperature (70°C, 100°C, 130°C, 160°C, or 190°C) in a glove box filled with inactive gas (N2).

[0114] <Evaluation>

[0115] The surface of the annealed perovskite layer was observed at various magnifications using a scanning electron microscope (SEM) to confirm the coating state of the perovskite layer on the substrate.

[0116] Figure 2 A surface SEM image of the perovskite layer obtained by applying the annealing conditions of Non-Patent Document 1 is shown. For example... Figure 2 As shown, when the annealing conditions of Non-Patent Document 1 are applied, it is confirmed that there are exposed portions of the substrate that are not covered by the perovskite layer.

[0117] Figure 3 The summary shows surface SEM images of the perovskite layer obtained by one-step annealing at a specified temperature. (Example) Figure 3 As shown, when the annealing temperature is below 100°C (70°C, 100°C), it was confirmed that there were exposed portions of the substrate not covered by the perovskite layer. On the other hand, it was confirmed that when the annealing temperature is above 130°C (130°C, 160°C, 190°C), the coverage of the perovskite layer increases. Furthermore, at an annealing temperature of 190°C, perovskite crystal collapse was observed. Therefore, it was confirmed that if annealing is performed at a temperature above 130°C and below 160°C, a sufficiently high coverage of the perovskite layer can be achieved in a single heat treatment without crystal collapse.

Claims

1. A method for manufacturing a solar cell, which is a method for manufacturing a solar cell having a photoelectric conversion layer containing a perovskite compound, comprising: a step of drying a coated precursor solution at a temperature of 130°C or higher and 160°C or lower under a non-reactive gas atmosphere. A precursor solution of a perovskite compound containing formamidinium ions and at least one metal ion selected from potassium ions (K + ), rubidium ions (Rb + ), cesium ions (Cs + ), and francium ions (Fr + ) is coated on a coated surface, and The solvent of the precursor solution contains N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

2. The method for manufacturing a solar cell according to claim 1, wherein The precursor solution contains a perovskite compound represented by the following formula (1), 3. The method for manufacturing a solar cell according to claim 1 or 2, wherein ABX3 (1) In the drying step, the heat treatment time is 10 minutes or longer and 20 minutes or shorter. wherein A is a monovalent cation comprising formamidinium ions and at least one metal ion selected from potassium ions (K + ), rubidium ions (Rb + ), cesium ions (Cs + ), and francium ions (Fr + ), B is selected from lead ions (Pb 2+ ), tin ions (Sn 2+ ), and combinations thereof, and X is a halide ion.

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

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