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: The thickness of the nickel oxide layer of the hole transport layer is 5. 0nm or more and 300. 0nm or less in the laminate of the light transmissive layer and the hole transport layer. Condition 1: A peak current and a peak potential of an anode peak appearing in a first cyclic voltammogram obtained by performing cyclic voltammetry on an electrically 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. Condition 2: The total light transmittance of the laminate is 70% 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, a hole transport layer, a perovskite layer, an electron 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 hole-transport layer of an inverted perovskite solar cell having a light-transmitting electrode layer, a hole-transport layer, a perovskite layer, an electron-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 a light-transmitting electrode layer, a hole transport layer, a perovskite layer, an electron transport layer, and a collector electrode layer in this order, the laminate comprising the light-transmitting electrode layer and the hole transport layer, the laminate comprising a conductive member that forms the light-transmitting electrode layer, and a nickel oxide layer that forms the hole transport layer and is disposed on the surface of the conductive member, the nickel oxide layer having a film thickness of 5.0 nm or more and 300.0 nm or less, and satisfying the following conditions 1 and 2. Condition 1: The peak current and peak potential of an anodic peak appearing in a first cyclic voltammogram obtained by performing cyclic voltammetry on a 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 more. Condition 2: The total light transmittance of the laminate is 70% or more. [2] A perovskite solar cell having a light-transmitting electrode layer, a hole-transporting layer, a perovskite layer, an electron-transporting layer, and a collector electrode layer in this order, wherein the light-transmitting electrode layer and the hole-transporting layer are the laminate according to [1]. [3] A method for producing the laminate according to [1], comprising cathodically polarizing the conductive member in a treatment solution containing a Ni component and a nitrate ion component, thereby forming the nickel 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, a hole transport layer, a perovskite layer, an electron 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 hole-transport layer of a perovskite solar cell having a light-transmitting electrode layer, a hole-transport layer, a perovskite layer, an electron-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, a hole transport layer 3, a perovskite layer 4, an electron transport layer 5, and a collector electrode layer 6. The thicknesses of the perovskite layer 4, the electron 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 hole transport layer 3.

[0013] The hole transport layer 3 is the same as the nickel oxide layer 9 described later, and a preferred embodiment of the hole transport layer 3 will also be described later. The hole transport layer 3 may be, for example, a nickel oxide layer containing nickel oxide (NiO), which is a p-type semiconductor. The thickness of the hole transport layer 3 corresponds to the Ni film thickness of the nickel 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. 1and R 2 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 electron transport material constituting the electron transport layer 5 is not particularly limited, and examples thereof include n-type conductive polymers, n-type low-molecular organic semiconductors, graphene materials, n-type metal oxides, and fullerene compounds (C 60 , C 70 , Phenyl C 61 Butyric acid methyl ester (PCBM) and indene-C 60 Examples include diadducts (e.g., ICBA), perylene diimide compounds, and naphthalene diimide compounds. Among these, PCBM 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 will become the light-transmitting electrode layer 2 and the hole-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 nickel oxide layer 9 that serves as the hole 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 nickel 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] <Nickel oxide layer> The nickel oxide layer 9 is a layer containing nickel oxide. The nickel oxide layer 9 is a layer that functions as the hole transport layer 3 (see Figure 1) in the perovskite solar cell 1. The hole transport layer 3 extracts holes generated in the perovskite layer 4 during light absorption and suppresses the backflow of electrons, thereby suppressing the recombination of electrons and holes and contributing to improved output characteristics. Conventionally, the material for the hole transport layer 3 is CuO. x , CuSCN, V2O5 and MoO x However, in the present invention, nickel oxide is used as the material for the hole transport layer 3. This is because nickel oxide has an optimal energy level, high hole mobility, high transmittance, environmental stability, and the like.

[0022] Film Thickness The thickness of the nickel oxide layer 9 is not less than 5.0 nm and not more than 300.0 nm, which provides the perovskite solar cell 1 manufactured using the laminate 7 with excellent output characteristics. When the thickness of the nickel 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 nickel oxide layer 9. This is thought to reduce the occurrence of leakage current and improve output characteristics. Furthermore, it is presumed that when the thickness of the nickel oxide layer 9 is 300.0 nm or less, the resistance to movement of holes generated in the perovskite layer 4 adjacent to the hole transport layer 3 (nickel oxide layer 9) is reduced, improving the output characteristics. However, mechanisms other than those described above are also considered to be within the scope of the present invention as long as the thickness of nickel oxide layer 9 is 5.0 nm or more and 300.0 nm or less.

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

[0024] In the present disclosure, the film thickness of nickel oxide layer 9 is determined as follows. First, a cross-sectional sample is prepared by processing an arbitrary portion of the nickel oxide layer 9 into a thin slice using a focused ion beam (FIB). The obtained cross-sectional sample is subjected to fluorescent X-ray analysis under the following conditions using an X-ray fluorescence analyzer (XRF device) to measure the fluorescent X-ray intensity of nickel (Ni). The film thickness (unit: nm) of the nickel oxide layer 9 is determined from the obtained fluorescent X-ray intensity of Ni using a calibration curve prepared in advance. The calibration curve is created using the following method. First, a sample with a nickel 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 nickel (Ni). A calibration curve is created using linear regression from the obtained Ni X-ray fluorescence intensity and the film thickness measured by STEM. Hereinafter, the thickness of the nickel oxide layer measured by the above-mentioned measuring method will also be referred to as "Ni 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 1: Nickel oxide layer coverage The laminate according to the present invention satisfies the following condition 1. Condition 1: 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 nickel 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 nickel 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 nickel oxide layer on the surface of the conductive member, and it is considered that the higher the coverage, the larger the area of ​​the surface of the conductive member covered by the nickel oxide layer and the more densely the nickel oxide layer is covered. When the coverage is 90% or more and the laminate 7 satisfies condition 1, 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 nickel 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 nickel oxide layer 9, and it may be 100% or less.

[0030] Condition 2: Total light transmittance of laminate The total light transmittance of the laminate 7 is 70% or more, which means that the perovskite solar cell 1 using the laminate 7 has excellent output characteristics. In order to obtain a perovskite solar cell with more excellent output characteristics, the total light transmittance of the laminate 7 is preferably 75% or more, and more preferably 80% or more. There is no particular upper limit to the total light transmittance of the laminate 7, and it may be 100% or less.

[0031] The total light transmittance (hereinafter also simply referred to as "transmittance") of the laminate 7 can be obtained by measuring in the measurement wavelength range of 380 to 780 nm using a spectrophotometer / colorimeter (for example, "SD 7000" manufactured by Nippon Denshoku Industries Co., Ltd.) and a pulsed xenon lamp as a light source.

[0032] [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 nickel oxide layer that serves as a hole 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 nickel oxide layer, where the nickel oxide layer has a film thickness of 5.0 to 300.0 nm and satisfies conditions 1 and 2.

[0033] A more detailed example of a method for manufacturing a laminate includes a method of forming a nickel oxide layer 9 on the surface of the conductive member 8 by cathodically polarizing the conductive member 8 in a treatment solution containing a Ni component and a nitrate ion component, i.e., by passing electricity through the conductive member 8 as a cathode (hereinafter also referred to as the "present film formation method").

[0034] In this film formation method, it is presumed that the nickel 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, when the Ni component in the treatment solution is nickel nitrate, nickel hydroxide is produced. This nickel hydroxide adheres to the surface of the conductive member 8, and then undergoes dehydration condensation through subsequent washing, drying, etc., to form a nickel 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 thickness of the formed nickel oxide layer 9 is 5.0 to 300.0 nm and the laminate satisfies conditions 1 and 2.

[0035] 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.

[0036] The treatment liquid contains a Ni component (Ni compound), which supplies Ni (nickel element) to the nickel oxide layer 9 to be formed. The Ni component is not particularly limited as long as it is a compound that dissociates in the treatment solution to generate Ni cations, and is preferably at least one selected from the group consisting of nickel nitrate (Ni(NO3)2), nickel fluoride (NiF2), nickel chloride (NiCl2), nickel bromide (NiBr2), nickel sulfate (NiSO4), and nickel acetate (Ni(CH3COO)2).

[0037] 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 nickel nitrate (Ni(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.

[0038] One of the Ni component and the nitrate ion component may also serve as the other. For example, when the Ni component is nickel nitrate, the Ni component also serves as a nitrate ion component. From the viewpoints of the stability of the treatment solution, ease of availability, etc., it is preferable to use nickel nitrate as a component that serves as both an Ni component and a nitrate ion component.

[0039] The content of the Ni component 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 Ni 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.

[0040] 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.

[0041] The solvent contained in the treatment liquid is not particularly limited, but water is preferred. The pH of the treatment liquid is not particularly limited and is, for example, pH 2.0 to 6.0. To adjust the pH, known acid components (such as phosphoric acid and sulfuric acid) or alkali components (such as sodium hydroxide and aqueous ammonia) 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.

[0042] The temperature of the treatment solution used in this film formation method is preferably 20°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher, from the viewpoint of increasing the thickness of the Ni film in the resulting nickel oxide layer 9. If the temperature of the treatment solution is high, the activation energy of the dehydration reaction is likely to be exceeded, and the number of hydroxy groups in the formed nickel oxide layer tends to decrease. Therefore, it is believed that an increase in the temperature of the treatment solution promotes the generation of nickel hydroxide, resulting in an increase in the thickness of the Ni film in the nickel 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 80°C or lower.

[0043] 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.

[0044] 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 / cm2 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 nickel 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 Ni film thickness of the nickel 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.

[0045] Next, methods for increasing the coverage under various cathodic polarization conditions will be described.

[0046] <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 nickel oxide layer 9 is formed by increasing the pH near the conductive member 8 due to current application, generating nickel 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 Ni film thickness of the nickel oxide layer 9 and increase the coverage.

[0047] <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 Ni film thickness of the nickel oxide layer 9, thereby increasing the coverage. Increasing the electrical conductivity in the treatment solution increases the reduction reaction rate, which promotes the production of nickel hydroxide and increases the Ni film thickness of the nickel oxide layer.

[0048] <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 nickel hydroxide and increasing the thickness of the Ni film in the nickel oxide layer.

[0049] Furthermore, a method for suppressing the decrease in transmittance of the nickel oxide layer due to various cathodic polarization conditions will be described.

[0050] <Relationship between current application time, current density and transmittance> For the same current application time, increasing the current density decreases the transmittance of the nickel oxide layer. The nickel oxide layer 9 is formed by increasing the pH near the conductive member 8 due to current application, generating nickel hydroxide, followed by a dehydration reaction. When the current density is high, the reduction reaction rate of nitrate ions is high, resulting in the generation of not only colorless and transparent Ni(OH)2 but also brown NiOOH and black Ni2O3, which tends to decrease the transmittance of the nickel oxide layer. On the other hand, when the current density is low, the reduction reaction rate of nitrate ions is relatively slow, resulting in the generation of only Ni(OH)2. This suppresses the decrease in the transmittance of the nickel oxide layer and, as a result, the decrease in the total light transmittance of the laminate. Furthermore, by decreasing the current density and increasing the current application time, the decrease in the transmittance of the nickel oxide layer can be suppressed without changing the Ni film thickness, thereby suppressing the decrease in the total light transmittance of the laminate.

[0051] 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 nickel oxide layer progresses as the retention time increases. Therefore, the retention time is not particularly limited as long as the nickel oxide layer 9 does not dissolve completely, but is preferably 30 seconds or less, and more preferably 2 seconds or less.

[0052] In the present film forming method, the conductive member with the nickel 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 nickel 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 nickel 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.

[0053] [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, a hole transport layer 3, a perovskite layer 4, an electron 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 perovskite layer 4, electron transport layer 5, and collector electrode layer 6 in that order on the surface of nickel oxide layer 9 in laminate .

[0054] 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 nickel oxide layer 9 that will become the hole 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.

[0055] The electron transport layer 5 may be formed, for example, by spin-coating an electron transport material such as PCBM (518-83371, Fujifilm Wako Pure Chemical Industries, Ltd.) on the surface of the perovskite layer 4 and drying it.

[0056] The collecting electrode layer 6 may be formed, for example, by depositing a conductive metal such as Au on the surface of the electron 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]

[0057] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the following examples.

[0058] <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.

[0059] <Preparation of Laminate> First, a treatment solution (hereinafter simply referred to as "treatment solution") containing nickel nitrate (Ni(NO3)2) or nickel chloride (NiCl2) and adjusted to a pH of 4 to 5 using sodium hydroxide or sulfuric acid was prepared. In each treatment solution, the amount of nickel nitrate or nickel chloride was adjusted so as to obtain the Ni content (unit: mol / L) shown in Tables 1 and 2 below. Further, potassium nitrate was added to the treatment solutions used in Examples 1 to 16 and Comparative Examples 1 to 4 in amounts that would give the contents (unit: mol / L) shown in Tables 1 and 2 below.

[0060] 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.

[0061] The cleaned glass substrate with the ITO film was immersed in each of the prepared treatment solutions, whose temperatures (units: ° C.) were as shown in Tables 1 and 2 below. 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 nickel 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. As a result, a nickel oxide layer (25 mm x 25 mm) that would serve as a hole transport layer was formed on the surface of the ITO film of the ITO-coated glass substrate, and a glass substrate with an ITO film on which a nickel oxide layer was formed (a laminate that would serve as a light-transmitting electrode layer and a hole transport layer) was produced.

[0062] <Ni film thickness measurement> The thickness of the nickel oxide layer of each of the produced laminates was measured according to the method described above, and the results are shown in Tables 1 and 2 below.

[0063] <<Measurement of coverage (condition 1)>> The coverage of the nickel 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.

[0064] 《Total light transmittance (condition 2)》 The total light transmittance of the produced laminate was measured according to the method described above.

[0065] <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.

[0066] <<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 nickel oxide layer of each laminate produced 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 resulting material was then heated at 100°C for approximately 1 hour to form a 500 nm-thick perovskite layer.

[0067] <<Formation of Electron Transport Layer>> A solution of 2% by mass of PCBM (Product No. 518-83371, Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in chlorobenzene was dropped onto the surface of the perovskite layer, and the layer was spin-coated at 1000 rpm for 30 seconds. The layer was then heated at 105°C for 15 minutes to form a 50 nm thick electron transport layer.

[0068] <<Formation of Collector Electrode Layer>> On the surface of the formed electron 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 an electron 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 electron 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.

[0069] The glass substrate thus obtained, on one surface of which was formed an ITO film (light-transmitting electrode layer), a nickel oxide layer (hole transport layer), a perovskite layer, an electron 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 nickel oxide layer (hole transport layer), a perovskite layer, an electron transport layer, and a collector electrode layer.

[0070] <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.

[0071] (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

[0072] The reference cell (perovskite solar cell of Comparative Example 13) was produced according to the above-described method for producing a perovskite solar cell, except that when producing the laminate, instead of forming a nickel oxide layer by cathode polarization, a laminate was used in which a dispersion liquid prepared by dispersing 2 mass % nickel oxide nanoparticles (637130, manufactured by Sigma-Aldrich) in 1-butanol (026-03326, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was spin-coated at 4000 rpm for 40 seconds to form a nickel oxide layer with a Ni film thickness of 20.0 nm. Furthermore, perovskite solar cells of Comparative Examples 11 and 12 were fabricated according to the method for fabricating the reference cell described above, except that the spin coating conditions were changed to form nickel oxide layers with Ni film thicknesses of 300.0 nm and 100.0 nm, respectively, to obtain laminates.

[0073] Tables 1 and 2 show the method for forming the nickel oxide layer, the measurement results of the laminate, and the evaluation results of 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 nickel 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 nickel oxide layer was formed and a laminate was produced by the above-mentioned spin coating.

[0074] [Table 1]

[0075] [Table 2]

[0076] <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 18 of the present invention, in which the Ni deposition amount of the nickel oxide layer was 5 nm or more and 300 nm or less, the coverage of the nickel oxide layer was 90% or more, and the transmittance of the laminate was 70% or more, had good output characteristics. In particular, Examples 1, 2, 4, 8, 9, 11, 12 and 15 to 17, in which the Ni film thickness of the nickel oxide layer was 15.0 nm or more and 50.0 nm or less, the coverage of the nickel oxide layer was 90% or more, and the transmittance of the laminate was 75% or more, had better output characteristics. In contrast, Comparative Examples 2, 3, 4, 9, and 10, in which the Ni film thickness of the nickel oxide layer was too thin, Comparative Example 7, in which the Ni film thickness was too thick, Comparative Examples 2 to 10 and 12, in which the coverage of the nickel oxide layer was too low, and Comparative Examples 5, 7, and 11, in which the transmittance of the laminate was too low, had insufficient output characteristics.

[0077] <Ni film thickness> The thickness of the Ni film increases with an increase in the charge density, which is the product of the current density and the current application time. Comparing Examples 5 to 8 and 10 to 13, which differ only in the current flow time, the Ni film thickness increased as the current flow time increased. By adjusting the current flow time so that the Ni film thickness was 5.0 nm or more and 300.0 nm or less, the power generation efficiency was evaluated as B. Furthermore, by adjusting the current flow time so that the Ni film thickness was 15.0 nm or more and 50.0 nm or less, the power generation efficiency was evaluated as A. This is presumably because adjusting the Ni film thickness makes it possible to suppress leakage current and the resistance to hole migration generated in the perovskite layer 4 adjacent to the hole transport layer 3 (nickel oxide layer 9). Furthermore, when obtaining the same Ni 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 Ni deposition amount 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 Ni film thickness can be obtained with a shorter current flow time.

[0078] Coverage The coverage rate increased as the Ni film thickness increased, reaching 90% or more when the Ni film thickness was 15.0 nm or more, and tended to be 95% or more when the Ni film thickness was 20.0 nm or more. Comparing Examples 1 to 18 of the present invention with Comparative Examples 1 to 6 and 8 to 10, when the Ni 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 7, when the Ni film thickness was too thick, the coverage rate was 90% or less. This is thought to be because when the Ni film thickness was too thick, cracks were more likely to occur in the nickel oxide layer, exposing part of the light-transmitting electrode and reducing the coverage rate.

[0079] 《Transmittance》 The transmittance of the laminate decreases with increasing current density and current flow time. Comparing invention examples 1 and 2 with comparative example 1, the transmittance of the laminate decreases with increasing current density. Furthermore, comparing invention examples 5 to 8, the transmittance of the laminate decreases with increasing current flow time. As the current density and current flow time increase, the Ni film thickness increases, and the transmittance of the laminate decreases. [Explanation of symbols]

[0080] 1: Perovskite solar cells 2: Light-transparent electrode layer 3: Hole transport layer 4: Perovskite layer 5:Electron transport layer 6:Collector electrode layer 7: Laminate 8: Conductive material 9: Nickel oxide layer

Claims

1. A perovskite solar cell having a light-transmitting electrode layer, a hole transport layer, a perovskite layer, an electron transport layer, and a collector electrode layer in this order, comprising a laminate that forms the light-transmitting electrode layer and the hole transport layer, a conductive member that will become the light-transmitting electrode layer; a nickel oxide layer that serves as the hole transport layer and is disposed on the surface of the conductive member; the thickness of the nickel oxide layer is 5.0 nm or more and 300.0 nm or less; A laminate satisfying the following conditions 1 and 2: Condition 1: 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) Condition 2: The laminate has a total light transmittance of 70% or more.

2. A perovskite solar cell having, in this order, a light-transmitting electrode layer, a hole transport layer, a perovskite layer, an electron transport layer, and a collector electrode layer, A perovskite solar cell, wherein the light-transmitting electrode layer and the hole 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 Ni component and a nitrate ion component, thereby forming the nickel 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, a hole transport layer, a perovskite layer, an electron transport layer, and a collector electrode layer in this order.

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