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 + and drying the applied precursor solution at a temperature of 130°C or higher and 160°C or lower in an inert gas atmosphere.

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: drying the applied precursor solution at a temperature of 130°C or higher and 160°C or lower under an inert gas atmosphere; 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 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 one-step annealing at a predetermined temperature. 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 Pb 2+ 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] (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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] Inorganic materials that can be used as the material for the electron transport layer include titanium oxide, tin oxide, and zinc oxide.

[0037] 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.

[0038] (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.

[0039] 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, or 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.

[0040] (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.

[0041] 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.

[0042] 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.

[0043] <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.

[0044] The following provides a detailed description of the film-forming step of the photoelectric conversion layer 4. The film-forming step of the present invention for the photoelectric conversion layer 4 includes a step of applying a precursor solution of a perovskite compound to the application surface (step S1), and a step of drying the applied precursor solution at a temperature of 130°C or higher and 160°C or lower in an inert gas atmosphere (step S2).

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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:

[0049] 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)

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] In the film formation process of the photoelectric conversion layer 4, a drying process is performed after step S1, thereby completing the film formation of the photoelectric conversion layer 4 (step S2). By performing step S2 according to this embodiment, the photoelectric conversion layer 4 is formed on the surface of the first carrier transport layer 3a.

[0056] In step S2, the liquid film of the precursor solution applied in step S1 is dried under predetermined heat treatment conditions to remove the solvent in the liquid film. Note that in the manufacturing method of the present invention, step S2 can also be called an annealing step.

[0057] In step S2, the liquid film of the precursor solution applied in step S1 is dried at a temperature of 130°C or higher and 160°C or lower. When the heat treatment temperature is 130°C or higher, the coverage of the photoelectric conversion layer with respect to the lower layer is improved, thereby improving the power generation performance of the solar cell and preventing short circuits. When the heat treatment temperature is 160°C or lower, decomposition of the perovskite compound is suppressed, thereby improving the power generation performance of the solar cell. Note that the heat treatment temperature may be, for example, 100°C or higher and 180°C or lower, as long as a sufficiently high coverage of the photoelectric conversion layer with respect to the lower layer and the suppression of decomposition of the perovskite compound are achieved.

[0058] In step S2, 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.

[0059] Step S2 is carried out in an inert gas atmosphere from the viewpoint of the stability of the perovskite compound. Any gas that does not react with the perovskite compound may be used as the inert gas, such as nitrogen or argon.

[0060] As described above, in the manufacturing method according to this embodiment, the heat treatment temperature is controlled to 130°C or higher and 160°C or lower in the step of drying the applied precursor solution. This configuration allows a solar cell to be manufactured in a single heat treatment step, thereby improving manufacturing costs and ease of use. Furthermore, this configuration improves the power generation performance of the solar cell. [Example]

[0061] 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.

[0062] <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.

[0063] <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 0.17 A solution of PbI3-10% PbCl2-NMP / DMF (1 / 5 volume ratio) was prepared.

[0064] <Perovskite layer deposition> The precursor solution was dropped onto the substrate, and coated using a spin coater at 5000 rpm for 50 seconds, followed by annealing under the specified conditions described below to form a perovskite layer on the substrate.

[0065] 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, annealing was performed at 70 °C for 5 minutes in a glove box filled with inert gas (N), and then the substrate was removed from the glove box and annealed in air at 150 °C for 10 minutes.

[0066] 2. One-step annealing The substrate coated with the precursor solution was annealed for 15 minutes at a predetermined temperature (70°C, 100°C, 130°C, 160°C, or 190°C) in a glove box filled with inert gas (N2).

[0067] <Evaluation> 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.

[0068] 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.

[0069] Figure 3 shows a summary of SEM images of the surface of the perovskite layer obtained by one-stage annealing at a predetermined temperature. As shown in Figure 3, when the annealing temperature was 100°C or lower (70°C, 100°C), it was confirmed that there were bare areas of the substrate that were not covered with the perovskite layer. On the other hand, when the annealing temperature was 130°C or higher (130°C, 160°C, 190°C), it was confirmed that the coverage of the perovskite layer improved. Furthermore, when the annealing temperature was 190°C, it was confirmed that the perovskite crystals were broken. Therefore, when annealing was performed at a temperature of 130°C or higher and 160°C or lower, it was confirmed that a sufficiently high coverage of the perovskite layer could be achieved by one-stage heat treatment, and the crystals could remain intact. [Explanation of symbols]

[0070] 1:Substrate 2a: First electrode layer 2b: Second electrode layer 3a: First Carrier Transport Layer 3b: Second Carrier Transport Layer 4: Photoelectric conversion layer C: Solar Cell

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: drying the applied precursor solution at a temperature of 130° C. or higher and 160° C. or lower under an inert gas atmosphere; 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 or 2, wherein the heat treatment time in the drying step is 10 minutes or more and 20 minutes or less.

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