Method for manufacturing perovskite solar cell

Abstract

The present invention provides means for producing a perovskite solar cell having high conversion efficiency and high durability.SOLUTION: An aspect of the present invention relates to a method for producing a perovskite solar cell, the method including a coating step of coating a carrier transport layer with a precursor solution containing a precursor substance that generates a perovskite-type crystal, an additive represented by the formula (I), and a solvent, and a heating step of heat-treating a precursor layer obtained in the coating step to form a photoelectric conversion layer containing a perovskite film.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, perovskite solar cells have been developed as a technology for achieving carbon neutrality. Perovskite solar cells have a perovskite film containing perovskite-type crystals as a photoelectric conversion layer.

[0003] For example, Patent Document 1 describes a method for producing a finely divided perovskite film by applying and drying a solution in which a precursor substance for forming perovskite crystals and an ionic liquid are dissolved in a solvent, followed by annealing. This document also describes a method for producing a functional device such as a perovskite solar cell, which uses the finely divided perovskite film produced by the above method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6501303 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, Patent Document 1 describes that the method described therein can microparticulate perovskite crystals to the nano-level, thereby improving optical properties, etc. However, Patent Document 1 does not consider durability under high temperature and high humidity environments. Thus, conventional perovskite solar cells have had problems in terms of achieving both conversion efficiency and durability.

[0006] Therefore, an object of the present invention is to provide a means for producing perovskite solar cells with high conversion efficiency and high durability. [Means for solving the problem]

[0007] The present inventors have investigated various means for solving the above problems. They have found that by forming a perovskite film to be used as the photoelectric conversion layer of a perovskite solar cell using a precursor solution containing a specific additive, the conversion efficiency and durability of the photoelectric conversion layer can be improved. Based on this finding, the present inventors have completed the present invention.

[0008] That is, the present invention includes the following aspects and embodiments. (Embodiment 1) A method for manufacturing a perovskite solar cell, comprising: a precursor material for forming a perovskite crystal and a compound represented by formula (I): [ka] a coating step of coating a precursor solution containing an additive represented by the formula (I) and a solvent onto the carrier transport layer; a heating step of heating the precursor layer obtained in the coating step to form a photoelectric conversion layer including a perovskite film; The method comprising: Embodiment 2: The method of embodiment 1, wherein the precursor material is a mixture of a halogenated organic amine and a metal halide. Embodiment 3: The method of embodiment 2, wherein the precursor material is a mixture of methylammonium iodide and lead iodide. Embodiment 4: The method of any one of embodiments 1 to 3, wherein the solvent is N,N-dimethylformamide. [Effects of the Invention]

[0009] The present invention makes it possible to provide a means for producing perovskite solar cells having high conversion efficiency and high durability. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a cross-sectional view illustrating one embodiment of a perovskite solar cell manufactured by a method according to one aspect of the present invention. [Figure 2] These are scanning electron microscope (SEM) images of perovskite films prepared in the examples. In the figure, 1 to 7 represent SEM images of perovskite films prepared using precursor solutions containing the respective compounds as additives. "No" represents an SEM image of a perovskite film prepared using a precursor solution of a comparative example that does not contain any additives. [Figure 3] 1 is a graph showing the results of high-temperature and high-humidity tests on the perovskite films prepared in the examples. In the graph, the horizontal axis represents the compound number of the additive contained in the precursor solution, and the vertical axis represents the percentage of the area of ​​lead iodide (PbI) relative to the total area of ​​the measured perovskite film (PVK) (PbI / PVK area ratio, %). DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will now be described in detail.

[0012] One aspect of the present invention relates to a method for manufacturing a perovskite solar cell.

[0013] In each embodiment of the present invention, a perovskite solar cell refers to a dye-sensitized solar cell having at least a photoelectric conversion layer containing a perovskite film and two carrier transport layers disposed on both sides of the photoelectric conversion layer, one of which is a hole transport layer and the other is an electron transport layer.

[0014] A cross-sectional view of one embodiment of a perovskite solar cell manufactured by the method of this aspect is shown in Figure 1. As shown in Figure 1, the perovskite solar cell 100 at least includes a substrate 11, a first electrode 12a disposed on the upper surface of the substrate 11, a first carrier transport layer 13a disposed on the upper surface of the first electrode 12a, a photoelectric conversion layer 14 disposed on the upper surface of the first carrier transport layer 13a, a second carrier transport layer 13b disposed on the upper surface of the photoelectric conversion layer 14, and a second electrode 12b disposed on the upper surface of the second carrier transport layer 13b. For example, when the perovskite solar cell 100 has a normal structure, the substrate 11 is a transparent substrate made of glass, resin, or the like, the first electrode 12a is a transparent electrode, the first carrier transport layer 13a is an electron transport layer, the second carrier transport layer 13b is a hole transport layer, and the second electrode 12b is a back electrode. Alternatively, when the perovskite solar cell 100 has an inverted structure, the substrate 11 is a transparent substrate made of glass, resin, or the like, the first electrode 12a is a transparent electrode, the first carrier transport layer 13a is a hole transport layer, the second carrier transport layer 13b is an electron transport layer, and the second electrode 12b is a back electrode.

[0015] The perovskite film contained in the photoelectric conversion layer usually contains perovskite crystals, which usually have a composition formula of ABX3 (wherein A is a monovalent cation, B is a divalent cation, and X is a monovalent anion) and have a cubic unit cell.

[0016] Examples of the monovalent cation A that constitutes the perovskite crystal include monovalent organic ammonium ions, monovalent amidinium ions, and monovalent metal ions. The monovalent organic ammonium ions are CH3NH3 + (methylammonium ion, hereinafter also referred to as "MA"), C2H5NH3 + , C3H7NH3 + or C4H9NH3 + The monovalent amidinium ion is preferably HC(NH2)2 +(formamidinium ion, hereinafter also referred to as "FA") is preferred. The monovalent metal ion is preferably a rubidium ion (Rb + ) or cesium ions (Cs + The monovalent cation A may be only one of the cations exemplified above, or may be a combination of two or more of the cations exemplified above. The monovalent cation A is preferably MA alone or a combination of MA and another cation, and more preferably MA alone.

[0017] The divalent cation B constituting the perovskite crystal can be, for example, a divalent metal ion. The divalent metal ion is a lead ion (Pb 2+ ) or tin ions (Sn 2+ The divalent cation B may be only one of the cations exemplified above, or may be a combination of two or more of the cations exemplified above. The divalent cation B is preferably Pb 2+ It is preferable that:

[0018] The monovalent anion X constituting the perovskite crystal can be, for example, a halogen ion. The halogen ion is a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ) or iodide ion (I - The halogen ion may be one of the anions listed above, or a combination of two or more of the anions listed above. The monovalent anion X is preferably I - , Cl - or Br - Preferably, I - It is more preferable that:

[0019] In the perovskite solar cell produced by the method of this embodiment, whether the perovskite film contained in the photoelectric conversion layer contains perovskite crystals having the characteristics described above can be confirmed, for example, by analyzing the perovskite film contained in the photoelectric conversion layer by X-ray diffraction (XRD).

[0020] The method of this embodiment includes at least a coating step and a heating step. The coating step and the heating step are steps for forming a photoelectric conversion layer. The method of this embodiment may optionally include a material preparation step and an electrode and carrier transport layer formation step. The electrode and carrier transport layer formation step can be performed by applying a technique for forming an electrode and a carrier transport layer that is commonly used in the technical field. The coating step, the heating step, and the material preparation step for performing these steps will be described in detail below.

[0021] [1: Material preparation process] This step involves preparing a precursor solution for a perovskite film to be used in the coating step and heating step for forming a photoelectric conversion layer. The precursor solution prepared in this step typically contains at least a precursor substance for generating perovskite crystals, an additive, and a solvent.

[0022] Each component of the precursor solution may be prepared by purchasing a commercially available product or by self-synthesis.

[0023] Each component of the precursor solution is described in further detail below.

[0024] [2: Coating process] This process involves applying a precursor solution containing a precursor material for generating perovskite crystals, an additive, and a solvent to the carrier transport layer, and by this process, a precursor layer containing the precursor material, the additive, and the solvent can be formed on the surface of the carrier transport layer.

[0025] The precursor material for producing the perovskite crystal can be appropriately selected based on the composition of the perovskite crystal described above. For example, when the monovalent cation A constituting the perovskite crystal is a monovalent organic ammonium ion, the divalent cation B is a divalent metal ion, and the monovalent anion X is a halogen ion, the precursor material may be a mixture of a halogenated organic amine and a metal halide. For example, when the monovalent cation A constituting the perovskite crystal is only MA and the divalent cation B is Pb 2+ and the monovalent anion X is I - In this case, the precursor material is preferably a mixture of methylammonium iodide (MAI) and lead iodide (PbI2).

[0026] In the method of this embodiment, the additive is represented by formula (I): [ka] The compound represented by formula (I) is a compound (1-(4-sulfobutyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide) represented by the formula (I). The compound represented by formula (I) has properties as an ionic liquid. The perovskite film obtained by carrying out this process using a precursor solution containing the compound represented by formula (I) as an additive has a larger particle size of perovskite crystals contained in the perovskite film and is more durable under high temperature and high humidity conditions than conventional perovskite films obtained using a precursor solution without any additive. Furthermore, the perovskite film obtained by carrying out this process using a precursor solution containing the compound represented by formula (I) as an additive has a larger particle size of perovskite crystals contained in the perovskite film and is more durable under high temperature and high humidity conditions than not only ionic liquids consisting of other combinations of cations and anions but also perovskite films obtained using similar ionic liquids with different anions (e.g., 1-(4-sulfobutyl)-3-methylimidazolium trifluoromethanesulfonate) as an additive.

[0027] In perovskite solar cells, the larger the particle size of the perovskite crystals contained in the perovskite film used as the photoelectric conversion layer, the fewer grain boundaries with high electrical resistance there are. Therefore, perovskite solar cells having a perovskite film containing perovskite crystals with large particle sizes as a photoelectric conversion layer have high light energy conversion efficiency. Furthermore, the perovskite crystals contained in the perovskite film can be hydrolyzed when they come into contact with water vapor. This hydrolysis reaction is generally accelerated under high temperature and high humidity conditions (e.g., a temperature of 50°C or higher and a humidity of 80% RH or higher). Therefore, the higher the durability of the perovskite film used as the photoelectric conversion layer under high temperature and high humidity conditions, the higher the durability of the perovskite solar cell. Therefore, by performing this process using a precursor solution containing the additives exemplified above, it is possible to produce perovskite solar cells with high conversion efficiency and high durability.

[0028] Examples of the solvent include aprotic polar solvents such as amide solvents, lactone solvents, lactam solvents, and sulfoxide solvents. The solvent is preferably N,N-dimethylformamide (DMF), γ-butyrolactone, N-methylpyrrolidone, dimethyl sulfoxide (DMSO), or a mixture thereof, and more preferably DMF. By carrying out this step using a precursor solution containing the solvents exemplified above, the precursor solution can be applied uniformly.

[0029] In this step, the means for applying the precursor solution to the carrier transport layer is not particularly limited, and various means commonly used in the art can be applied. Examples of application means include blade coating, die coating, inkjet coating, spraying, and spin coating. Any of the above-mentioned methods can be applied to this step.

[0030] This step may optionally further include applying a poor solvent to the precursor layer. In this embodiment, the poor solvent refers to a solvent in which the solubility of the perovskite crystal is lower than that of the solvent contained in the precursor solution. The poor solvent is preferably an aliphatic hydrocarbon, an aromatic hydrocarbon, an alcohol, an ether, or a fatty acid, more preferably dichloromethane, chloroform, toluene, benzene, chlorobenzene, tetralin, propanol, butanol, diethyl ether, tetrahydrofuran, or acetic acid, or a mixture thereof, and even more preferably chlorobenzene. In this embodiment, the means for applying the poor solvent to the precursor layer may be the same as the means for applying the precursor solution to the carrier transport layer, as exemplified above. Performing this step using the poor solvent exemplified above promotes the growth of the perovskite crystal and improves the conversion efficiency of the resulting perovskite solar cell.

[0031] [3:Heating process] This step includes heat-treating the precursor layer obtained in the coating step, and this step anneals the precursor layer to form a photoelectric conversion layer including a perovskite film.

[0032] In this step, the heat treatment temperature is preferably in the range of 70 to 200°C. The heat treatment time is preferably in the range of 1 to 60 minutes. By carrying out this step under the conditions exemplified above, the precursor layer can be annealed to promote the growth of perovskite crystals.

[0033] This step may further include drying the precursor layer, if desired. In this embodiment, the drying step may be performed as the same step as the annealing step, or may be performed as a separate step. Examples of drying steps include heat drying, vacuum drying, and dry gas spraying. When a heat drying step is used, it is preferable to perform the same step as the annealing step in this step.

[0034] The high conversion efficiency of the perovskite solar cell produced or capable of being produced by the method of this embodiment described above can be evaluated, for example, by using a scanning electron microscope (SEM) to observe the surface condition of the perovskite film contained in the photoelectric conversion layer of the perovskite solar cell and measuring the particle size of the perovskite particles present in the perovskite film. In perovskite solar cells produced or capable of being produced by the method of this embodiment, the particle size of the perovskite particles present in the perovskite film contained in the photoelectric conversion layer is usually 100 nm or more, particularly 140 nm or more.

[0035] The high durability of perovskite solar cells produced or capable of being produced by the method of this embodiment described above can be evaluated, for example, by conducting a high-temperature and high-humidity test using a perovskite film contained in the photoelectric conversion layer of the perovskite solar cell according to the following procedure. The perovskite film is exposed to high-temperature and high-humidity test conditions (e.g., 50°C, 80% RH) for a predetermined period of time. An XRD analyzer is then used to analyze the composition of the perovskite crystals present on the surface of the exposed perovskite film and the hydrolysis products of the perovskite crystals (e.g., BX2 formed by hydrolysis of the perovskite crystals ABX3). Based on the analytical values, the percentage of the area of ​​the hydrolysis products (e.g., BX2) relative to the total area of ​​the measured perovskite film is calculated. In a perovskite solar cell that is or can be produced by the method of this embodiment, the proportion of hydrolysis products of perovskite crystals present in the perovskite film contained in the photoelectric conversion layer is usually less than the proportion of hydrolysis products calculated by carrying out a similar high-temperature and high-humidity test on a conventional perovskite solar cell produced using a precursor solution that does not contain any additives.

[0036] That the perovskite solar cell is manufactured by the method of the present embodiment described above can be confirmed, for example, by identifying the compound represented by the formula (I) in the perovskite film included in the photoelectric conversion layer of the perovskite solar cell by instrumental analysis such as nuclear magnetic resonance spectrum (NMR) or mass spectrum (MS).

[0037] As described in detail above, by the method of the present embodiment, a perovskite solar cell having high conversion efficiency and high durability can be manufactured. The perovskite solar cell manufactured or manufacturable by the method of the present embodiment has high conversion efficiency of light energy in the perovskite film used as the photoelectric conversion layer and high durability of the perovskite film under high temperature and high humidity conditions. Therefore, the perovskite solar cell manufactured or manufacturable by the method of the present embodiment is suitable for applications used in outdoor environments continuously exposed to high temperature and high humidity environments (for example, a temperature of 50°C or higher and a humidity of 80% RH or higher), such as in-vehicle applications such as automobiles, or installation applications on the roofs or walls of buildings. The perovskite solar cell manufactured or manufacturable by the method of the present embodiment can exhibit high conversion efficiency and high durability over a long period even when applied to the applications exemplified above.

Example

[0038] <I: Fabrication of Perovskite Film> [I-1: Preparation of Precursor Solution] A mixture of methylammonium iodide (MAI) and lead iodide (PbI2) as a precursor substance for generating perovskite crystals, the compounds shown in Table 1 below as additives, N,N-dimethylformamide (DMF) as a solvent, and chlorobenzene as a poor solvent were each prepared. The precursor substance was dissolved in the solvent. A predetermined additive was added to this solution so as to have a content of 0.75% by mass to prepare a precursor solution. As a comparative example, a precursor solution not containing an additive was prepared.

[0039]

Table 1

[0040] [I-2: Formation of Perovskite Film] By the spin coating method, after dropping the precursor solution prepared in I-1 onto a glass substrate, the glass substrate was rotated at a high speed under the conditions of 1000 rpm for 10 seconds or 4000 rpm for 20 seconds to uniformly coat the precursor solution on the glass substrate. Next, after dropping a poor solvent onto the applied precursor solution, the glass substrate was rotated at a high speed under the condition of 4000 rpm for 10 seconds to form a precursor layer on the surface of the glass substrate (coating process). Then, the glass substrate was heated on a hot plate under the conditions of 100°C for 15 minutes to dry and anneal the precursor layer (heating process). By such treatment, the solvent and poor solvent contained in the precursor layer were removed, and perovskite-type crystals were grown to form a perovskite film.

[0041] [II: Performance Evaluation of Perovskite Film] [II-1: Observation of Perovskite-Type Crystals and Measurement of Particle Size] The surface state of the prepared perovskite film was observed using SEM. The particle sizes of a plurality of perovskite particles were measured for each perovskite film, and the average value was calculated.

[0042] [II-2: High Temperature and High Humidity Test] The prepared perovskite film was exposed to high temperature and high humidity conditions (50°C, 80%RH) for 15 minutes. Then, using an XRD analyzer, the composition of the compounds present on the surface of the perovskite film after exposure was analyzed. Due to the exposure to the high temperature and high humidity test conditions, the perovskite-type crystals contained in the perovskite film hydrolyzed to form lead iodide. Based on the analysis values, the percentage of the area of lead iodide (PbI2) to the total area of the measured perovskite film (PVK) was calculated.

[0043] [II-3: Evaluation Results] The evaluation results of the fabricated perovskite films are shown in Table 2. In the table, the compound numbers of the additives correspond to the compound numbers shown in Table 1. The rows indicated by the compound numbers show the evaluation results of the perovskite films fabricated using precursor solutions containing the respective compounds as additives. "None" indicates the evaluation results of the perovskite films fabricated using comparative precursor solutions containing no additives. The particle diameter (nm) is the value calculated using the procedure in II-1, and the PbI2 / PVK area ratio (%) is the value calculated using the procedure in II-2.

[0044] [Table 2]

[0045] Figure 2 shows SEM images of the perovskite films prepared. In the figure, numbers 1 to 7 indicate SEM images of perovskite films prepared using precursor solutions containing the respective compounds as additives. "No" indicates an SEM image of a perovskite film prepared using a comparative precursor solution containing no additive. Figure 3 also shows the results of high-temperature and high-humidity tests of the prepared perovskite films. In the figure, the horizontal axis indicates the compound number of the additive contained in the precursor solution, and the vertical axis indicates the percentage of the area of ​​PbI2 relative to the total area of ​​the measured PVK (PbI2 / PVK area ratio, %).

[0046] As shown in Table 2, when a perovskite film was prepared using Compound 6 as an additive, the particle size of the perovskite crystals contained in the perovskite film was larger than that of the comparative perovskite film prepared using a precursor solution containing no additive. Furthermore, no pinholes were observed on the surface of the perovskite crystals (Figure 2). A perovskite solar cell having a perovskite film containing perovskite crystals with large particle sizes as a photoelectric conversion layer can have high light energy conversion efficiency.

[0047] As shown in Figure 3, when a perovskite film was prepared using Compound 6 as an additive, the PbI2 / PVK area ratio was smaller than that of a comparative perovskite film prepared using a precursor solution containing no additive. In high-temperature and high-humidity tests, a smaller PbI2 / PVK area ratio indicates a smaller amount of PbI2 produced by hydrolysis of the perovskite. Therefore, perovskite solar cells having a perovskite film with a small PbI2 / PVK area ratio as a photoelectric conversion layer under high-temperature and high-humidity test conditions can have high durability.

[0048] The above results demonstrate that perovskite solar cells having a photoelectric conversion layer containing a perovskite film prepared using compound 6 as an additive can have higher conversion efficiency and durability than conventional perovskite solar cells.

[0049] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to add, delete, and / or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0050] 100... Perovskite solar cell, 11... Substrate, 12a... First electrode, 12b... Second electrode, 13a... First carrier transport layer, 13b... Second carrier transport layer, 14... Photoelectric conversion layer

Claims

1. 1. A method of manufacturing a perovskite solar cell, comprising: a precursor material for forming a perovskite crystal and a compound represented by formula (I): 【Chemistry 1】 a coating step of coating a precursor solution containing an additive represented by the formula (I) and a solvent onto the carrier transport layer; a heating step of heating the precursor layer obtained in the coating step to form a photoelectric conversion layer including a perovskite film; The method comprising:

2. 10. The method of claim 1, wherein the precursor material is a mixture of a halogenated organic amine and a metal halide.

3. 3. The method of claim 2, wherein the precursor material is a mixture of methylammonium iodide and lead iodide.

4. 10. The method of claim 1, wherein the solvent is N,N-dimethylformamide.

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