Laminate, perovskite solar cell, method for producing laminate, and method for producing perovskite solar cell

Abstract

To provide a laminate capable of obtaining a perovskite solar cell having excellent output characteristics.SOLUTION: In the solar battery including a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector layer, the light-transmitting electrode layer and the electron transport layer are stacked, the light-transmitting electrode layer includes a conductive member, the electron transport layer includes a tin oxide layer, and the tin oxide layer has a thickness of 5.0 nm or more and 80.0 nm or less and satisfies Condition A. Condition A: A peak current and a peak potential of an anode peak appearing in a first cyclic voltammogram obtained by performing cyclic voltammetry on a conductive member whose surface is not covered are defined as a current value A and a potential V, respectively. A current value at potential V in a second cyclic voltammogram obtained by subjecting the stack to cyclic voltammetry is defined as a current value B. At this time, the coverage ratio calculated by Formula (1) (coverage ratio (%) = (1-B / A) * 100) is 90% or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, a known perovskite solar cell is a "normal type (NIP structure)" perovskite solar cell having, in this order, a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer. Furthermore, in recent years, from the perspective of improving durability, an "inverted (PIN structure)" perovskite solar cell has been proposed, which has a light-transmitting electrode layer, a hole transport layer, a perovskite layer, an electron transport layer, and a collector electrode layer in that order. For example, Patent Document 1 describes a photovoltaic device having a PIN structure, in which a p-type hole transport layer is supported on a substrate, a perovskite layer and an n-type electron transport layer are disposed on the p-type layer in this order, a light-transmitting conductive layer is provided on top of the n-type electron transport layer to form a light-receiving upper surface, and an interface structure is provided between the n-type electron transport layer and the light-transmitting conductive layer, which has two inorganic electrical insulating layers with a layer of electrically conductive material therebetween, the electrical insulating layer and the layer of electrically conductive material being made of materials with bandgaps in a predetermined range, and each electrical insulating layer forms a Type 1 offset junction with the layer of electrically conductive material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-533037 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, a perovskite solar cell has, for example, a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order. Such perovskite solar cells are required to exhibit excellent output characteristics.

[0005] Therefore, an object of the present invention is to provide a laminate that serves as the light-transmitting electrode layer and the electron transport layer of a normal-type perovskite solar cell having a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order, and that can provide a perovskite solar cell with excellent output characteristics. Another object of the present invention is to provide a perovskite solar cell having excellent output characteristics. Furthermore, an object of the present invention is to provide a novel method for producing the above-mentioned laminate, and a novel method for producing a perovskite solar cell. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above object can be achieved by employing the following configuration, and have completed the present invention.

[0007] That is, the present invention provides the following [1] to [4]. [1] A perovskite solar cell having, in this order, a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer. The laminate comprises a conductive member that forms the light-transmitting electrode layer and a tin oxide layer that forms the electron transport layer and is disposed on the surface of the conductive member. The tin oxide layer has a thickness of 5.0 nm to 80.0 nm, and satisfies the following condition A. Condition A: The peak current and peak potential of an anodic peak appearing in a first cyclic voltammogram obtained by performing cyclic voltammetry on the conductive member whose surface is uncoated are defined as current value A and potential V, respectively. The current value at potential V in a second cyclic voltammogram obtained by performing cyclic voltammetry on the laminate is defined as current value B. In this case, the coverage calculated by equation (1) (coverage (%) = (1 - B / A) × 100) is 90% or greater. [2] A perovskite solar cell having, in this order, a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer, The perovskite solar cell, wherein the light-transmitting electrode layer and the electron transport layer are the laminate according to [1]. [3] A method for producing a laminate according to [1], A method for producing a laminate, comprising cathodically polarizing the conductive member in a treatment liquid containing a Sn component and a nitrate ion component, thereby forming the tin oxide layer on the surface of the conductive member. [4] A method for producing a perovskite solar cell, using the laminate according to [1], to produce a perovskite solar cell having a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a laminate that serves as the light-transmitting electrode layer and the electron transport layer of a perovskite solar cell having a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order, and that can provide a perovskite solar cell with excellent output characteristics. Furthermore, the present invention can provide a perovskite solar cell with excellent output characteristics. Furthermore, the present invention can provide a novel method for producing the above-mentioned laminate and a novel method for producing a perovskite solar cell. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of a perovskite solar cell. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of the configuration of a laminate. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the embodiments described below are merely examples, and the present invention is not limited to the embodiments described below. In the drawings, the scale of the components may differ from the actual scale for easier viewing and explanation. In this specification, when a range is expressed using "to", the range includes both ends of the "to". For example, a range "A to B" includes A and B. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. In this specification, when two or more components are present, the description of the content of the component refers to the total content of the two or more components. As used herein, a combination of two or more preferred embodiments is a more preferred embodiment.

[0011] [Perovskite solar cells] First, a perovskite solar cell 1 will be described with reference to FIG. Figure 1 is a cross-sectional view schematically showing an example of the configuration of a perovskite solar cell 1. The perovskite solar cell 1 shown in Figure 1 has, in this order, a light-transmitting electrode layer 2, an electron transport layer 3, a perovskite layer 4, a hole transport layer 5, and a collector electrode layer 6. The thicknesses of the perovskite layer 4, the hole transport layer 5 and the collector electrode layer 6 are set appropriately.

[0012] Suitable examples of the light-transmitting electrode layer 2 include conductive metal oxide films such as an indium tin oxide (ITO) film and a fluorine-doped tin oxide (FTO) film. The thickness of the light-transmitting electrode layer 2 corresponds to the thickness of the conductive member 8 (see FIG. 2) described later. The light-transmitting electrode layer 2 may be disposed on the surface of a transparent substrate such as a glass substrate or a resin film. In this case, the transparent substrate is disposed on the surface of the light-transmitting electrode layer 2 opposite to the electron transport layer 3.

[0013] The electron transport layer 3 is the same as the tin oxide layer 9 described later, and a preferred embodiment of the electron transport layer 3 will also be described later. The electron transport layer 3 may be, for example, a tin oxide layer containing tin oxide (SnO22), which is an n-type semiconductor. The thickness of the electron transport layer 3 corresponds to the thickness of the tin oxide layer 9 (see FIG. 2) described later.

[0014] The perovskite layer 4 is a layer containing a compound having a perovskite crystal structure (hereinafter also referred to as a "perovskite compound"). An example of a perovskite compound is a compound represented by the composition formula ABX3 (wherein A is a monovalent cation, B is a divalent cation, and X is a halogen anion). A in the perovskite compound (ABX3) may be, for example, [R 1 R 2 R 3 NH] + and cations of Group 1 elements such as Rb and Cs. 1 and R2 are both H, and R 3 is CH3, A is a methylammonium cation ([CH3NH3] + ) Functional group R 1 , R 2 and R 3 contains, for example, at least one element selected from carbon, hydrogen, nitrogen and oxygen. 1 , R 2 and R 3 contains carbon atoms, the functional group R 1 , R 2 and R 3 The total number of carbon atoms in the functional group R is preferably 4 or less. 1 , R 2 and R 3 may contain Group 1 elements such as Rb and Cs. As described above, B in ABX3 is a divalent cation. Examples of B include divalent cations of elements selected from the group consisting of transition metals, Group 13 elements, Group 14 elements, and Group 15 elements. Preferred specific examples of B include Pb 2+ , Ge 2+ and Sn 2+ B is Pb 2+ and Sn 2+ It is preferable that the compound contains at least one selected from the group consisting of Pb 2+ or Sn 2+ may be partially substituted with other elements. Examples of the substitution elements include Bi, Sb, In, Ge, and Ni. X in ABX3 is preferably at least one selected from Cl, Br and I. In the perovskite compound, each of the A, B and X sites may be occupied by multiple types of ions.

[0015] Specific examples of perovskite compounds (ABX3) include CH3NH3PbI3, CH3CH2NH3PbI3, NH2CHNH2PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CsPbI3, CsPbBr3, CH(NH2)2PbI3, CsPbI3, CH3NH3SnI3, CH3NH3Sn x Pb (1-x) I3, CH(NH2)2SnI3, etc.

[0016] The material constituting the hole transport layer 5 is not particularly limited, and examples thereof include inorganic compounds such as metal oxides, such as copper oxide, nickel oxide, manganese oxide, iron oxide, molybdenum oxide, vanadium oxide, and tungsten oxide. Examples of organic compounds include conductive polymers such as polythiophene, polypyrrole, polyacetylene, triphenylenediamine, and polyaniline doped with sulfonic acid and iodine, polythiophene derivatives having sulfonyl groups as substituents, conductive organic compounds such as arylamines, Nafion, and lithium-doped Spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene). The conductive polymers include a polymer formed by combining poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS) and doped P3HT (poly(3-hexylthiophene-2,5-diyl)). Of these, Spiro-OMeTAD is preferred.

[0017] Examples of the collector electrode layer 6 include an Au electrode layer, an Ag electrode layer, an Al electrode layer, and a Ca electrode layer, and among these, an Au electrode layer is preferable.

[0018] [Laminate] Next, with reference to FIG. 2, the laminate 7 that becomes the light-transmitting electrode layer 2 and the electron transport layer 3 of the perovskite solar cell 1 (see FIG. 1) will be described. 2 is a cross-sectional view schematically illustrating an example of the configuration of the laminate 7. The laminate 7 has a conductive member 8 that serves as the light-transmitting electrode layer 2 (see FIG. 1), and a tin oxide layer 9 that serves as the electron transport layer 3 (see FIG. 1) disposed on the surface of the conductive member 8.

[0019] <Conductive material> The conductive member 8 is a layer that contains a light-transmitting conductive compound and functions as the light-transmitting electrode layer 2 (see FIG. 1) when used in a perovskite solar cell. The conductive member 8 preferably contains a conductive metal oxide, and more preferably contains indium oxide or tin oxide. When the conductive member 8 is a member containing indium oxide, it is more preferable that it is a member containing indium tin oxide (ITO), and it is particularly preferable that it is an ITO film. When the conductive member 8 is a member containing tin oxide, it is more preferable that it is a member containing fluorine-doped tin oxide (FTO), and even more preferable that it is an FTO film. The conductive member 8 may be disposed on the surface of a transparent substrate such as a glass substrate or a resin film. That is, the laminate 7 may have a transparent substrate. When the laminate 7 has a transparent substrate, the transparent substrate is disposed on the surface of the conductive member 8 opposite to the tin oxide layer 9.

[0020] The thickness of the conductive member 8, which is, for example, an ITO film or FTO film, is set appropriately depending on the resulting perovskite solar cell 1 (see FIG. 1), but is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more, while it is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less. The thickness of the conductive member 8 is a value obtained by forming a cross section of the conductive member 8 using a focused ion beam and measuring the cross section using a scanning electron microscope.

[0021] <Tin oxide layer> The tin oxide layer 9 is a layer containing tin oxide. The tin oxide layer 9 is a layer that functions as the electron transport layer 3 (see Figure 1) in the perovskite solar cell 1. The electron transport layer 3 extracts electrons generated in the perovskite layer 4 during light absorption and suppresses the backflow of holes, thereby suppressing the recombination of electrons and holes and contributing to improved output characteristics. Conventionally, salts of alkali metals such as lithium, sodium, potassium, and cesium, and metal oxides such as zinc oxide, titanium oxide, aluminum oxide, indium oxide, and tin oxide have been used as materials for the electron transport layer 3, but in the present invention, tin oxide is used as the material for the electron transport layer 3. This is because tin oxide has an optimal energy level, high electron mobility, high transmittance, environmental stability, and the like.

[0022] Film Thickness The thickness of the tin oxide layer 9 is not less than 5.0 nm and not more than 80.0 nm, which provides the perovskite solar cell 1 manufactured using the laminate 7 with excellent output characteristics. When the thickness of the tin oxide layer 9 is 5.0 nm or more, it is difficult for an area on the surface of the conductive member 8 not to be covered with the tin oxide layer 9. This is thought to reduce the occurrence of leakage current and improve output characteristics. Furthermore, it is presumed that if the thickness of the tin oxide layer 9 is 80.0 nm or less, the resistance to the movement of electrons generated in the perovskite layer 4 adjacent to the electron transport layer 3 (tin oxide layer 9) is reduced, improving the output characteristics. However, any mechanism other than the above is also within the scope of the present invention as long as the film thickness of the tin oxide layer 9 is 5.0 nm or more and 80.0 nm or less.

[0023] For reasons of better output characteristics, the thickness of the tin oxide layer 9 is preferably 10.0 nm or more, more preferably 15.0 nm or more. For the same reasons, the thickness of the tin oxide layer 9 is preferably 100.0 nm or less, more preferably 50.0 nm or less.

[0024] In the present disclosure, the thickness of the tin oxide layer 9 is determined as follows. First, a cross-sectional sample is prepared by processing an arbitrary portion of the tin oxide layer 9 into a thin slice using a focused ion beam (FIB). An X-ray fluorescence analysis is performed on the obtained cross-sectional sample using an X-ray fluorescence analyzer (XRF device) under the following conditions to measure the X-ray fluorescence intensity of tin (Sn). The film thickness (unit: nm) of the tin oxide layer 9 is determined from the obtained X-ray fluorescence intensity of Sn and the film thickness measured by STEM using a calibration curve prepared in advance. The calibration curve is created using the following method. First, a sample with a tin oxide layer is prepared, and a cross-sectional specimen is prepared by processing it into a thin slice using a focused ion beam (FIB). The obtained cross-sectional specimen is observed using a scanning transmission electron microscope (STEM) and the film thickness (unit: nm) is measured. In addition, an X-ray fluorescence analysis is performed on an arbitrary portion of the same sample used for length measurement using the STEM using an X-ray fluorescence analyzer (XRF) under the following conditions to measure the X-ray fluorescence intensity of tin (Sn). A calibration curve is created using linear regression from the obtained X-ray fluorescence intensity of Sn and the film thickness measured by STEM. Hereinafter, the film thickness of the tin oxide layer measured by the above-mentioned measuring method will also be referred to as "Sn film thickness."

[0025] (Conditions for measurement using an XRF device) XRF equipment: EDX-7000 (Shimadzu Corporation) X-ray tube: Rhodium (Rh) target (voltage: 50 kV, current: 88 μA) Primary filter: OPEN Detector: Silicon drift semiconductor detector ·Analysis area: φ5mm ·Analysis time: 100 seconds Dead time: 30% Smoothing calculation method: Savitzky-Gloay Smoothing score: 5 Repeat count: 1 Background calculation: Automatic Sample form: Bulk (sample size: 16mm x 11mm)

[0026] Condition A: Tin oxide layer coverage The laminate according to the present invention satisfies the following condition A. Condition A: The peak current and peak potential of the anodic peak in a first cyclic voltammogram obtained by performing cyclic voltammetry on a conductive member whose surface is not covered with a tin oxide layer or the like are defined as current value A and potential V, respectively. The current value at potential V in a second cyclic voltammogram obtained by performing cyclic voltammetry on a laminate in which a tin oxide layer is disposed on the surface of a conductive member is defined as current value B. In this case, the coverage calculated by the following formula (1) is 90% or more. Coverage (%) = (1-B / A) x 100 (1)

[0027] The coverage derived by the above-mentioned cyclic voltammetry measurement indicates the coverage state of the tin oxide layer on the surface of the conductive member, and it is considered that the higher the coverage rate, the larger the area of ​​the conductive member surface covered by the tin oxide layer and the more densely the tin oxide layer is covered. When the coverage is 90% or more and the laminate 7 satisfies condition A, the perovskite solar cell 1 produced using the laminate 7 will have excellent output characteristics. The measurement conditions for the above cyclic voltammetry are as follows.

[0028] (Measurement conditions for cyclic voltammetry) Potentiostat: Multi-electrochemical measurement system (HZ-Pro S12, manufactured by Meiden Hokuto Co., Ltd.) Application: Hoktnet Client (version 1.15a, manufactured by Meiden Hokuto Co., Ltd.) Electrochemical cell: Plate electrode evaluation cell (VM2, manufactured by EC Frontier) Reference electrode: Ag / AgCl (RE-2A, EC Frontier) Counter electrode: Platinum (CE-2, manufactured by EC Frontier) Reaction solution: an aqueous solution containing 0.5 mM K4[Fe(CN)6]·3H2O (Fujifilm Wako Pure Chemical Industries, Ltd.), 0.5 mM K3[Fe(CN)6] (Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.5 M KCl (Fujifilm Wako Pure Chemical Industries, Ltd.). ·Sweep speed: 50mV / s Sweep range: -0.5~1.0V

[0029] In order to obtain a perovskite solar cell with more excellent output characteristics, the coverage of the tin oxide layer 9 is preferably 90% or more, and more preferably 93% or more. There is no particular upper limit to the coverage of the tin oxide layer 9, and it may be 100% or less.

[0030] [Method of manufacturing laminate] The method for producing a laminate of the present invention is, in outline, a method for producing a laminate having a conductive member that serves as a light-transmitting electrode layer and a tin oxide layer that serves as an electron transport layer disposed on the surface of the conductive member. The method for producing the laminate of the present invention is not particularly limited as long as it is a method that can produce a laminate having the above-mentioned conductive member and tin oxide layer, the Sn film thickness of the tin oxide layer being 5.0 to 80.0 nm, and that satisfies condition A.

[0031] A more detailed example of a method for manufacturing a laminate is a method in which a conductive member 8 is cathodically polarized in a treatment solution containing an Sn component and a nitrate ion component, i.e., an electric current is passed through the conductive member 8 as a cathode, thereby forming a tin oxide layer 9 on the surface of the conductive member 8 (hereinafter also referred to as the "film formation method").

[0032] In this film formation method, it is presumed that the tin oxide layer 9 is formed by the following mechanism. First, on the surface of the conductive member 8, a reduction reaction from nitrate ions to nitrite ions occurs, causing an increase in the pH of the treatment solution. As a result, for example, if the Sn component in the treatment solution is tin chloride, tin hydroxide is produced. This tin hydroxide adheres to the surface of the conductive member 8, and then undergoes dehydration and condensation by washing, drying, etc., to form a tin oxide layer 9. However, even if a mechanism other than the above is used, it is considered to be within the scope of the present invention as long as the Sn film thickness of the formed tin oxide layer 9 is 5.0 to 80.0 nm and the laminate satisfies condition A.

[0033] The conductive member 8 used in this film forming method is as already explained. When the conductive member 8 is disposed on the surface of a transparent substrate such as a glass substrate or a resin film, the transparent substrate with the conductive member 8 (for example, a glass substrate with an ITO film) is cathodically polarized. In this case, the laminate obtained by this film formation method also has a transparent substrate.

[0034] The treatment liquid contains a Sn component (Sn compound), which supplies Sn (elemental tin) to the tin oxide layer 9 to be formed. The Sn component is not particularly limited as long as it is a compound that dissociates in the treatment solution to generate Sn cations, and at least one selected from the group consisting of tin nitrate (Sn(NO3)2), tin fluoride (SnF2), tin chloride (SnCl2), tin bromide (SnBr2), tin sulfate (SnSO4), and tin acetate (Sn(CH3COO)2) is preferred.

[0035] The treatment liquid contains a nitrate ion component. The nitrate ion component is not particularly limited as long as it is a compound that dissociates in the treatment solution to generate nitrate ions, and at least one selected from the group consisting of tin nitrate (Sn(NO3)2), nitric acid (HNO3), sodium nitrate (NaNO3), potassium nitrate (KNO3), magnesium nitrate (Mg(NO3)2), calcium nitrate (Ca(NO3)2), and ammonium nitrate (NH4NO3) is preferred.

[0036] One of the Sn component and the nitrate ion component may also serve as the other. For example, when the Sn component is tin nitrate, the Sn component also serves as a nitrate ion component.

[0037] The content of Sn components in the treatment solution is preferably 1.500 mol / L or less, more preferably 1.000 mol / L or less, even more preferably 0.500 mol / L or less, particularly preferably 0.400 mol / L or less, and most preferably 0.300 mol / L or less. On the other hand, the content of the Sn component in the treatment liquid is preferably 0.001 mol / L or more, more preferably 0.005 mol / L or more, and even more preferably 0.010 mol / L or more.

[0038] The content of nitrate ions in the treatment solution is nitrate ions (NO3 - ) is preferably 3.5 mol / L or less, more preferably 3.0 mol / L or less, and even more preferably 2.0 mol / L or less. On the other hand, the content of nitrate ions in the treatment solution is nitrate ions (NO3 - ) is preferably 0.001 mol / L or more, more preferably 0.005 mol / L or more, and even more preferably 0.01 mol / L or more.

[0039] The solvent contained in the treatment liquid is not particularly limited, but water is preferred. The pH of the treatment solution is not particularly limited and is, for example, 0.0 to 8.0, preferably 0.1 to 6.0. To adjust the pH, known acid components (e.g., phosphoric acid, sulfuric acid, etc.) or alkali components (e.g., sodium hydroxide, aqueous ammonia, etc.) can be used. The treatment liquid may contain, as necessary, a surfactant such as sodium lauryl sulfate or acetylene glycol, etc. From the viewpoint of stability of adhesion behavior over time, the treatment liquid may contain a condensed phosphate such as pyrophosphate.

[0040] The temperature of the treatment solution used in this film formation method is preferably 20°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher, from the viewpoint of increasing the Sn film thickness of the resulting tin oxide layer 9. If the temperature of the treatment solution is high, it is likely to exceed the activation energy of the dehydration reaction, and the hydroxyl groups in the formed tin oxide layer tend to decrease. Therefore, it is thought that an increase in the temperature of the treatment solution promotes the production of tin hydroxide, resulting in a thicker Sn film in the tin oxide layer. On the other hand, the upper limit of the temperature of the treatment liquid is not particularly limited, and is, for example, 90° C. or lower, preferably 85° C. or lower.

[0041] The treatment liquid may further contain a conduction aid. Examples of the conduction aid include sulfates such as potassium sulfate, sodium sulfate, magnesium sulfate, and calcium sulfate, and chlorides such as potassium chloride, sodium chloride, magnesium chloride, and calcium chloride. The conduction aid also contains the above-mentioned nitrate ion component. The content of the conduction aid in the treatment liquid is preferably 0.001 to 3.5 mol / L, more preferably 0.005 to 3.0 mol / L, and even more preferably 0.01 to 2.0 mol / L.

[0042] The current density during cathodic polarization was 0.1 mA / cm 2 More than 1.0 mA / cm is preferable. 2 The above is more preferable. On the other hand, the current density during cathodic polarization is 100mA / cm 2 Preferably less than 80mA / cm 2 Less than 50mA / cm is more preferable. 2 The following is even more preferable: If the current density is within this range, it is easy to obtain a tin oxide layer 9 that uniformly covers the surface of the conductive member 8. The current application time is appropriately set to obtain a desired coverage rate and Sn film thickness of the tin oxide layer 9. As the counter electrode when performing cathodic polarization, an insoluble electrode such as a platinum electrode is preferred because it is suitable for this film formation method.

[0043] Next, methods for increasing the coverage under various cathodic polarization conditions will be described.

[0044] <Relationship between current application time, current density and coverage rate> When the current density is the same, the coverage can be increased by increasing the current application time. The tin oxide layer 9 is formed by increasing the pH near the conductive member 8 due to the application of current, generating tin hydroxide, which then undergoes a dehydration reaction. As the current application time increases, there is enough time for the dehydration reaction to proceed, which is thought to increase the Sn film thickness of the tin oxide layer 9 and increase the coverage.

[0045] <Relationship between nitrate ion content and coverage rate> When the current density and current application time are the same, increasing the content of the nitrate ion component increases the Sn film thickness of the tin oxide layer 9 and can increase the coverage. Increasing the electrical conductivity in the treatment solution increases the reduction reaction rate, which promotes the production of tin hydroxide and increases the Sn film thickness of the tin oxide layer.

[0046] <Relationship between processing liquid temperature and coverage rate> When the temperature of the treatment solution is high, the activation energy of the dehydration reaction is easily exceeded, promoting the production of tin hydroxide, increasing the Sn film thickness of the tin oxide layer, and increasing the coverage.

[0047] <Relationship between pH of treatment solution and coverage rate> When the current density and current flow time are the same, the lower the pH of the treatment solution, the more easily the tin hydroxide generated by cathodic polarization redissolves in the treatment solution, resulting in a decrease in the thickness of the Sn film in the tin oxide layer. Therefore, when the pH of the treatment solution is low, extending the current flow time increases the Sn film thickness and can increase the coverage.

[0048] In this film formation method, after cathodic polarization is performed by passing a current through the conductive member, the laminate 7 may be retained in the treatment solution. It is believed that dissolution of the deposited tin oxide layer progresses as the retention time increases. Therefore, the retention time is not particularly limited as long as the tin oxide layer 9 does not dissolve completely, but is preferably 30 seconds or less, and more preferably 2 seconds or less.

[0049] In the present film forming method, the conductive member with the tin oxide layer may be washed with water after the cathodic polarization. The method for washing with water is not particularly limited, and examples thereof include a method in which the conductive member with the tin oxide layer is immersed in water after cathodic polarization, etc. The temperature of the water used for washing with water (water temperature) is preferably 10 to 90°C. The water washing time is preferably more than 0.5 seconds, and more preferably 1.0 to 5.0 seconds. Furthermore, instead of or after washing with water, the conductive member with a tin oxide layer may be dried. The temperature and method of drying are not particularly limited, and for example, a drying method using a conventional dryer or electric furnace can be applied. The drying temperature is preferably 100°C or lower.

[0050] [Manufacturing method for perovskite solar cells] The method for producing a perovskite solar cell of the present invention is a method for producing a perovskite solar cell having, in this order, a light-transmitting electrode layer 2, an electron transport layer 3, a perovskite layer 4, a hole transport layer 5, and a collector electrode layer 6, using the above-mentioned laminate 7 of the present invention. A method for manufacturing a perovskite solar cell includes, for example, forming layers to become the perovskite layer 4, the hole transport layer 5, and the collector electrode layer 6 in that order on the surface of the tin oxide layer 9 in the laminate .

[0051] The perovskite layer 4 can be formed, for example, by spin-coating a solution of a perovskite compound, such as methylammonium iodide (132-18262, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and lead(II) iodide (L0279, manufactured by Tokyo Chemical Industry Co., Ltd.), on the surface of the tin oxide layer 9 that will become the electron transport layer 3, followed by heating. Examples of the solvent for the solution include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, pyridine, γ-butyrolactone, etc. A mixed solvent of two or more solvents may also be used.

[0052] The hole transport layer 5 may be formed, for example, by spin-coating the surface of the perovskite layer 4 with a hole transport layer-forming material such as a solution containing a mixture of Spiro-OMeTAD ("LT-S922" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, "B2542" manufactured by Tokyo Chemical Industry Co., Ltd.), and tBP (4-tert-butylpyridine, "142379" manufactured by Sigma-Aldrich), followed by drying. The solvent for the solution may be, for example, chlorobenzene, acetonitrile, or a mixture thereof.

[0053] The collecting electrode layer 6 may be formed, for example, by depositing a conductive metal such as Au on the surface of the hole transport layer 5. The method for forming each layer is not limited to these methods, and any conventionally known method can be used as appropriate. [Example]

[0054] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the following examples.

[0055] <Preparation of conductive material> An ITO (Indium Tin Oxide) film-coated glass substrate (25 mm × 25 mm, 0.7 mm thick, alkali-free glass) was prepared. The ITO film-coated glass substrate (sheet resistance: 5 Ω / sq, manufactured by Geomatec Co., Ltd.) had an ITO film deposited by sputtering on one surface of the glass substrate. This ITO-coated glass substrate was used as a transparent substrate with a conductive member to produce a laminate.

[0056] <Preparation of Laminate> First, a treatment liquid (hereinafter simply referred to as "treatment liquid") containing tin chloride (SnCl2) as the Sn component and nitric acid (HNO3) or potassium nitrate (KNO3) as the nitrate ion component was prepared. When preparing each treatment liquid, the amounts of the Sn component and the nitrate ion component were adjusted so that the contents thereof were as shown in Tables 1 and 2 below (unit: mol / L).

[0057] Next, the prepared ITO-coated glass substrate (transparent substrate with conductive member) was immersed in a cleaning solution prepared by diluting Semiclean (registered trademark) M4 (manufactured by Yokohama Yushi Kogyo Co., Ltd.) detergent 20 times with ion-exchanged water, and ultrasonic cleaning was performed for 10 minutes. Thereafter, the ITO-coated glass substrate was removed from the cleaning solution, immersed in ion-exchanged water, and ultrasonic cleaning was performed for 10 minutes.

[0058] The cleaned ITO-coated glass substrate was immersed in each of the prepared treatment solutions. The temperatures (units: °C) of the treatment solutions were as shown in Tables 1 and 2 below. Tables 1 and 2 below also show the pH of the treatment solutions measured with a pH meter. The ITO-coated glass substrate was subjected to cathodic polarization in the treatment solution under the cathodic polarization conditions (current density and current application time) shown in Tables 1 and 2. The current was stopped, and within 2 seconds from the end of cathodic polarization, the ITO-coated glass substrate with the tin hydroxide attached was removed from the treatment solution, immersed in water at 25°C in a water tank for 2.0 seconds to rinse, and then dried at room temperature using a blower. This resulted in a tin oxide layer (25 mm x 25 mm) that served as an electron transport layer being formed on the surface of the ITO film of the ITO-coated glass substrate, producing a glass substrate with an ITO film on which a tin oxide layer was formed (a laminate that served as a light-transmitting electrode layer and an electron transport layer).

[0059] <<Sn film thickness measurement>> The thickness of the tin oxide layer of each of the produced laminates was determined according to the method described above, and the results are shown in Tables 1 and 2 below.

[0060] <<Measurement of coverage (condition A)>> The coverage of the tin oxide layer of the produced laminate was determined according to the method described above, and the results are shown in Tables 1 and 2 below.

[0061] <Fabrication of perovskite solar cells> Using each of the prepared laminates, a 3 mm x 3 mm, i.e., 0.09 cm 2 We fabricated perovskite solar cells (PSCs) with a photoelectric conversion area of ​​10.

[0062] <<Formation of perovskite layer>> 0.17 g of methylammonium iodide and 0.48 g of lead iodide were dissolved in a solvent of DMF:DMSO=4:1 (volume ratio) to obtain a mixed solution. 70 μL of the above mixed solution was dropped onto the surface of the tin oxide layer of the laminate prepared in each example, and spin-coated at 3000 rpm for 30 seconds. During the spin-coating, 10 seconds after the constant speed was reached, 700 μL of chlorobenzene (284513, Sigma-Aldrich) was dropped. The sample was then heated at 100°C for approximately 1 hour to form a 500 nm thick perovskite layer.

[0063] <<Formation of Hole Transport Layer>> A mixture of 500 μL of a 7% by mass solution of Spiro-OMeTAD (LT-S922, Fujifilm Wako Pure Chemical Industries, Ltd.) in chlorobenzene, 9 μL of a 50% by mass solution of LiTFSI in acetonitrile, and 14 μL of tBP was dropped onto the surface of the perovskite layer. The dropped mixture was spin-coated at 5000 rpm for 30 seconds and then dried to form a 200 nm thick hole transport layer.

[0064] <<Formation of Collector Electrode Layer>> On the surface of the formed hole transport layer, an Au electrode layer (collecting electrode layer) was formed by vacuum deposition to a thickness of about 100 nm. More specifically, a shadow mask corresponding to the shape of ten 3 mm × 3 mm electrodes and a glass substrate on which a hole transport layer was formed were placed in a chamber. The pressure inside the chamber was reduced using a rotary pump and a turbomolecular pump until the pressure inside the chamber reached 2 × 10 -3 In this chamber, a gold wire was resistance-heated, and a 100 nm Au film was formed on the surface of the hole transport layer through a shadow mask. The film formation rate was 10 to 15 nm / min, and the pressure during film formation was 1×10 -2 It was below Pa.

[0065] The glass substrate thus obtained, on one surface of which was formed an ITO film (light-transmitting electrode layer), a tin oxide layer (electron transport layer), a perovskite layer, a hole transport layer, and a collector electrode layer, was sealed in the atmosphere to produce a perovskite solar cell having, in this order, a glass substrate, an ITO film (light-transmitting electrode layer), a tin oxide layer (electron transport layer), a perovskite layer, a hole transport layer, and a collector electrode layer.

[0066] <Evaluation of perovskite solar cells> The fabricated perovskite solar cells were evaluated as follows. A solar simulator (SAN-EI Electric, XES-502S) was used, with a spectral distribution of AM1.5G (IEC standard 60904-3) and an output of 100 mW / cm 2 The perovskite solar cell was irradiated from the ITO film side with simulated sunlight having a light intensity of 1000 kJ / s. Under this condition, the photocurrent-voltage profile of the perovskite solar cell was measured using a linear sweep voltammetry (LSV) measurement device (HZ-5000, manufactured by Hokuto Denko Co., Ltd.). The conversion efficiency (photoelectric conversion efficiency) was determined from the obtained profile and evaluated according to the following criteria. The results are shown in Tables 1 and 2. The higher the conversion efficiency value, the more excellent the output characteristics can be evaluated to be.

[0067] (Conversion efficiency evaluation standard) A: Conversion efficiency is 1.2 times or more that of the reference cell B: Conversion efficiency is more than 1x but less than 1.2x that of the reference cell C: Conversion efficiency is less than 1x that of the reference cell

[0068] The reference cell (perovskite solar cell of Comparative Example 9) was fabricated according to the above-described method for fabricating a perovskite solar cell, except that when fabricating the laminate, instead of forming a tin oxide layer by cathode polarization, a dispersion of 2.5 mass % tin oxide nanoparticles (18282-10-5, manufactured by Thermo Scientific) dispersed in 1-butanol (solvent) was spin-coated at 4000 rpm for 10 seconds to form a tin oxide layer with a Sn film thickness of 20.0 nm. Furthermore, perovskite solar cells of Comparative Examples 7 and 8 were fabricated according to the method for fabricating the reference cell described above, except that the spin-coating conditions were changed to form laminates in which tin oxide layers with Sn film thicknesses of 300.0 nm and 100.0 nm, respectively, were formed.

[0069] Tables 1 and 2 show the method for forming the tin oxide layer, the measurement results for the laminate, and the evaluation results for the conversion efficiency of the fabricated perovskite solar cell (PSC). In the table, when the "Classification" column of "Film Formation Method" shows "A," it means that a tin oxide layer was formed and a laminate was produced by performing cathodic polarization using the treatment solution shown in the "Treatment Solution Composition" column under the conditions shown in the "Cathode Polarization Conditions" column. Also, when the "Classification" column of "Film Formation Method" shows "B," it means that a tin oxide layer was formed and a laminate was produced by the above-mentioned spin coating.

[0070] [Table 1]

[0071] [Table 2]

[0072] <Summary of evaluation results> In Tables 1 and 2 above, the underlined values ​​are outside the range of the present invention. As shown in Tables 1 and 2 above, all of Examples 1 to 19 in which the Sn film thickness of the tin oxide layer was 5.0 nm or more and 80.0 nm or less and the coverage of the tin oxide layer was 90% or more, exhibited good output characteristics. In particular, Examples 1 to 2, 4 to 5, 7 to 8, 10 to 11, and 15 to 17, in which the Sn film thickness of the tin oxide layer was 10.0 nm or more and 50.0 nm or less and the coverage was 90% or more, had better output characteristics. In contrast, Comparative Example 4, in which the Sn film thickness of the tin oxide layer was too thin, Comparative Examples 2, 5, and 7 to 8, in which the Sn film thickness was too thick, and Comparative Examples 1, 3, and 6 to 9, in which the coverage was too low, had insufficient output characteristics.

[0073] <Sn film thickness> The Sn film thickness increases with an increase in the charge density, which is the product of the current density and the current application time. Comparing Examples 9 to 11 and 15 to 17, which differ only in the current flow time, the Sn film thickness increased as the current flow time increased. By adjusting the current flow time so that the Sn film thickness was 5.0 nm or more and 80.0 nm or less, the power generation efficiency was evaluated as B. Furthermore, by adjusting the current flow time so that the Sn film thickness was 10.0 nm or more and 50.0 nm or less, the power generation efficiency was evaluated as A. This is presumably because adjusting the Sn film thickness makes it possible to suppress leakage current and to suppress the migration resistance of holes generated in the perovskite layer 4 adjacent to the electron transport layer 3 (tin oxide layer 9). Furthermore, when obtaining the same Sn film thickness at different current densities, the current flow time decreased at high current densities and increased at low current densities. Thus, even when the current density is changed, the same Sn film thickness can be obtained by adjusting the current flow time. As the current density increases, the reduction reaction rate of nitrate ions increases, so the desired Sn film thickness can be obtained with a short current flow time.

[0074] Coverage The coverage rate increased as the Sn film thickness increased, reaching 90% or more when the Sn film thickness was 5.0 nm or more, and tended to be 95% or more when the Sn film thickness was 10.0 nm or more. Comparing Examples 1 to 19 and Comparative Examples 1 to 6, when the Sn film thickness was equal to or greater than a predetermined value, the coverage rate was sufficiently high, at 90% or more. On the other hand, in Comparative Example 2, when the Sn film thickness was too thick, the coverage rate was 90% or less. This is thought to be because when the Sn film thickness was too thick, cracks were more likely to occur in the tin oxide layer, exposing part of the light-transmitting electrode and reducing the coverage rate. Furthermore, in Comparative Examples 1 and 3, the coverage was sometimes 90% or less even when the Sn film thickness was within the range of 5.0 to 80.0 nm. This is thought to be because, under conditions that facilitate the reaction relatively easily, such as high reaction temperature, high current density, or long current application time, tin oxide is generated locally in a short period of time, causing unevenness in the Sn film thickness and resulting in a decrease in coverage. [Explanation of symbols]

[0075] 1: Perovskite solar cells 2: Light-transparent electrode layer 3: Electron transport layer 4: Perovskite layer 5: Hole transport layer 6:Collector electrode layer 7: Laminate 8: Conductive material 9: Tin oxide layer

Claims

1. A perovskite solar cell having a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order, comprising a laminate that forms the light-transmitting electrode layer and the electron transport layer, a conductive member that will become the light-transmitting electrode layer; a tin oxide layer that serves as the electron transport layer and is disposed on the surface of the conductive member; the thickness of the tin oxide layer is 5.0 nm or more and 80.0 nm or less; A laminate satisfying the following condition A. Condition A: The peak current and peak potential of the anodic peak appearing in the first cyclic voltammogram obtained by performing cyclic voltammetry on the conductive member whose surface is not coated are defined as the current value A and the potential V, respectively. In a second cyclic voltammogram obtained by subjecting the laminate to cyclic voltammetry, the current value at the potential V is defined as current value B. At this time, the coverage calculated by the following formula (1) is 90% or more. Coverage (%) = (1 - B / A) x 100 (1)

2. A perovskite solar cell having, in this order, a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer, A perovskite solar cell, wherein the light-transmitting electrode layer and the electron transport layer are the laminate according to claim 1.

3. A method for producing the laminate according to claim 1, comprising the steps of: A method for producing a laminate, comprising cathodically polarizing the conductive member in a treatment solution containing a Sn component and a nitrate ion component, thereby forming the tin oxide layer on the surface of the conductive member.

4. A method for producing a perovskite solar cell, comprising using the laminate according to claim 1 to produce a perovskite solar cell having a light-transmitting electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a collector electrode layer in this order.

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