Preparation method of perovskite thin film and solar cell

Abstract

The invention relates to a preparation method of a perovskite thin film and a solar cell. The invention provides a preparation method of a perovskite thin film. The preparation method comprises the following steps: preparing a perovskite precursor solution and a trimethylsulfonium salt post-treatment solution, forming the perovskite thin film on a substrate by using the perovskite precursor solution, and performing post-treatment on the formed perovskite thin film by using the trimethylsulfonium salt post-treatment solution to prepare the large-size grain perovskite thin film. According to the invention, the trimethyl sulfonium salt is introduced into the perovskite, the trimethyl sulfonium salt and the perovskite have strong interaction, and the phenomena of absorbing moisture and dissolving the perovskite can occur under the humidity condition. Meanwhile, due to the fact that the surface free energy of the large grains is different from that of the small grains, the small grains can generate a dynamic process that dissolution is larger than crystallization until disappearance, and the large grains can generate a dynamic process that crystallization is larger than dissolution. And finally, the Ovchwald ripening of the perovskite is realized at a relatively low temperature, and the perovskite thin film with high crystallinity, few grain boundaries and large-size grains is obtained.

Description

A method for preparing perovskite thin films and solar cells. Technical Field

[0001] This invention relates to the field of perovskite photovoltaics, and more specifically to a method for preparing a perovskite thin film and a solar cell. Background Technology

[0002] In p-type metal-semiconductor-metal perovskite solar cells (p-MPSCs), the mesopore confinement effect induced by the mesopore layer significantly impacts the perovskite crystallization process. Specifically, due to the spatial restriction of the mesopore structure, perovskite cannot grow freely during crystallization, resulting in an excessive number of grain boundaries in the formed perovskite crystal. These excessive grain boundaries disrupt the crystal continuity, forming numerous defect states, which in turn adversely affect the generation and transport of charge carriers. As the key carriers of photocurrent, the generation and transport efficiency of charge carriers directly determines the photoelectric conversion performance of the device. Therefore, perovskite materials with low crystallinity severely limit the overall performance of p-MPSCs.

[0003] To address this issue, existing technologies attempt to add salt additives during the annealing process to improve the crystallinity of perovskite through the Austrowald ripening mechanism. However, this method requires high-temperature conditions, which can damage perovskite materials, such as inducing decomposition and phase transitions. More seriously, the Austrowald ripening state is difficult to precisely control at high temperatures, thus affecting the final crystallinity of the perovskite and device performance. Therefore, developing a new technology that achieves controllable ripening at low temperatures while maintaining the stability of perovskite materials is crucial for improving the performance of p-MPSCs. Summary of the Invention

[0004] This invention provides a method for preparing perovskite thin films and solar cells, which solves the problem in the prior art that it is impossible to achieve controllable ripening at low temperatures while maintaining the stability of perovskite materials.

[0005] In a first aspect, the present invention provides a method for preparing a perovskite thin film, comprising: preparing a perovskite precursor solution and a trimethyl sulfonate post-treatment solution; forming a perovskite thin film on a substrate by applying the perovskite precursor solution; and performing post-treatment on the formed perovskite thin film using the trimethyl sulfonate post-treatment solution to obtain a large-size grain perovskite thin film.

[0006] In one optional embodiment, the perovskite precursor solution is prepared by dissolving chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide in a first solvent; the mass ratio of chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide is 0.5~1:0.5~1:1~2:5~10:40~50; the first solvent includes N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4~5:1; the concentration of the obtained perovskite precursor solution is 1~2 mmol / mL.

[0007] In one optional embodiment, the trimethyl sulfonium salt post-treatment solution comprises a trimethyl sulfonium salt and a second solvent, wherein the concentration of the trimethyl sulfonium salt is 5-15 g / L; the trimethyl sulfonium salt includes, but is not limited to, TMSBr and TMSI; and the second solvent comprises isopropanol and water in a volume ratio of 10-20:1.

[0008] In one optional embodiment, the substrate is an FTO glass substrate; the perovskite film is formed by spin-coating and depositing a perovskite precursor solution onto the FTO glass substrate; the amount of perovskite precursor solution added is 40-50 μL / cm³. 2 .

[0009] In one optional embodiment, the post-treatment method for the perovskite film is as follows: a trimethyl sulfonium salt post-treatment solution is added to the perovskite film by spin coating, and maintained in an environment with an air humidity of 50%-60% for 10-12 hours; the dropwise addition rate of the trimethyl sulfonium salt post-treatment solution is 40-50 μL / cm. 2 .

[0010] Secondly, the present invention also provides a method for fabricating a solar cell device, comprising: preparing a matrix intermediate having a multilayer porous film structure of c-TiO2 / mp-TiO2 / mp-ZrO2 / C, wherein the structure of the matrix intermediate is matrix / mp-TiO2 / mp-ZrO2 / C; filling the prepared intermediate with a perovskite precursor solution; and then performing post-treatment with a trimethyl sulfonium salt post-treatment solution to obtain a solar cell device.

[0011] In one optional embodiment, the perovskite precursor solution is prepared by dissolving chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide in a first solvent; the mass ratio of chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide is 0.5~1:0.5~1:1~2:5~10:40~50; the first solvent includes N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4~5:1; the concentration of the obtained perovskite precursor solution is 1~2 mmol / mL.

[0012] In one optional embodiment, the trimethyl sulfonium salt post-treatment solution comprises a trimethyl sulfonium salt and a second solvent, wherein the concentration of the trimethyl sulfonium salt is 5-15 g / L; the trimethyl sulfonium salt includes, but is not limited to, TMSBr and TMSI; and the second solvent comprises isopropanol and water in a volume ratio of 10-20:1.

[0013] In an optional embodiment, the preparation method of the matrix intermediate structure includes the following steps: depositing a TiO2 dense layer on a substrate to form a matrix, wherein the substrate is FTO glass; the preferred preparation process of the matrix includes: etching and cleaning the FTO glass, heating it to 400~500℃, spraying a TiO2 dense layer solution onto the FTO glass, cooling to complete the preparation of the TiO2 dense layer, and obtaining an FTO / c-TiO2 matrix; depositing TiO2 slurry onto the above-mentioned FTO / c-TiO2 matrix, drying it, sintering it and holding it at a certain temperature, and cooling it to complete the preparation of the mp-TiO2 layer, wherein the sintering temperature is 500~550℃ and the holding time is 0.5~1h; continuing to deposit mp-ZrO2 onto the above-mentioned mp-TiO2 layer, allowing it to stand and dry to obtain an FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 structure, and depositing C slurry on the FTO / c-TiO2 / mp-TiO2 / On an mp-ZrO2 substrate, after drying, sintering and holding at a certain temperature are carried out, and after cooling, a matrix intermediate with the structure FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C is obtained. The sintering temperature is 400~450℃ and the holding time is 0.5~1h.

[0014] In one optional embodiment, the thickness of the TiO2 dense layer is 20-25 nm, the thickness of the mp-TiO2 layer is 800-900 nm, the thickness of the mp-ZrO2 layer is 2-3 μm, and the total thickness of the FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C multilayer porous film structure is 25-30 μm.

[0015] In one optional embodiment, the filling of the perovskite precursor solution includes: drop-coating the perovskite precursor solution onto the carbon electrode side of the prepared matrix intermediate, allowing it to stand and permeate for 5-10 min, and then annealing it at 50-60°C for 18-20 h; the drop-coating amount of the perovskite precursor solution is 3-4 μL / cm. 2 The post-processing method includes: adding a trimethyl sulfonium salt post-processing solution to the obtained multilayer porous membrane structure intermediate, and drying the solution at 90~110℃ for 2~3 min after diffusion.

[0016] The technical solution of the present invention has the following advantages: 1. The present invention provides a method for preparing a perovskite thin film, comprising: preparing a perovskite precursor solution and a trimethyl sulfonate post-treatment solution, forming a perovskite thin film on a substrate by the perovskite precursor solution, and performing post-treatment on the formed perovskite thin film using the trimethyl sulfonate post-treatment solution to obtain a large-size grain perovskite thin film.

[0017] This invention provides a method for preparing perovskite thin films by introducing trimethyl sulfonate into the perovskite. The trimethyl sulfonate interacts strongly with the perovskite and possesses a certain hygroscopic capacity, allowing it to absorb moisture and dissolve the perovskite under humid conditions. Simultaneously, due to the difference in surface free energy between large and small grains, small grains undergo a dynamic process where dissolution exceeds crystallization until they disappear, while large grains undergo a dynamic process where crystallization exceeds dissolution. Ultimately, this method achieves the goal of Ohlwald ripening of perovskite at relatively low temperatures (e.g., room temperature without heating), resulting in perovskite thin films with high crystallinity, few grain boundaries, and large grain sizes.

[0018] 2. The present invention provides a method for preparing a solar cell device by introducing trimethyl sulfonium salt into perovskite. Since trimethyl sulfonium salt interacts strongly with perovskite, it can dissolve perovskite under specific conditions and has a certain hygroscopic capacity. Through its interaction with perovskite and moisture in the air, the crystallinity of perovskite in p-MPSCs is improved, thereby achieving the technical effect of improving the performance of perovskite solar cell devices. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 shows the SEM images of the perovskite films prepared in Examples 1(b), 2(c), and Comparative Example 1(a) of the present invention, and the XRD patterns (d) of the perovskite films prepared in Examples 1, 2, and Comparative Example 1 of the present invention; Figure 2 shows the SEM images of the perovskite films prepared in Comparative Example 1 and Comparative Example 2 of the present invention; Figure 3 shows the optimal performance reverse scan JV curves of the solar cell devices prepared in Examples 5, 6, and Comparative Example 3 of the present invention. Detailed embodiments are provided to better understand the present invention. However, the following embodiments do not limit the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0021] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] Example 1 This example provides a method for preparing a perovskite thin film, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0130 g cesium iodide (CsI), 0.0239 g MAI, 0.1376 g formamidinium hydroiodate (FAI) and 0.461 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 4:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of 1.25 mmol / mL.

[0023] S2. Preparation of the trimethylsulfonium salt post-treatment solution: Dissolve 5 mg of TMSBr in a mixed solution containing 475 μL of isopropanol (IPA) and 25 μL of water (volume ratio 19:1), and stir thoroughly until completely dissolved to obtain the TMSBr post-treatment solution.

[0024] S3. Sample Preparation: A 1 cm × 1 cm FTO glass was ultrasonically cleaned for 30 min. 40 μL of filtered perovskite solution was then deposited onto the FTO substrate using spin-coating to prepare a perovskite thin film. Specific spin-coating parameters were: acceleration from 200 rpm / s to 1000 rpm over 10 s, followed by acceleration from 2000 rpm / s to 6000 rpm / s.

[0025] S4. Post-treatment of the perovskite film: The perovskite film was post-treated using the TMSBr post-treatment solution prepared in step S2. Specifically, the post-treatment solution was spin-coated onto the perovskite film at a speed of 3000 r / min for 40 s. At the 15th second, 40 μL of sulfonium salt post-treatment solution was added dropwise. The treated film was then transferred to a humidity chamber with a set humidity of 50% and stored for 12 hours to allow for complete Oswald ripening and secondary crystallization, resulting in the post-treated perovskite film.

[0026] Example 2 This example provides a method for preparing a perovskite thin film, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0130 g cesium iodide (CsI), 0.0239 g MAI, 0.1376 g formamidinium hydroiodate (FAI) and 0.461 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 4:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of 1.25 mmol / mL.

[0027] S2. Preparation of Trimethylsulfonium Salt Post-treatment Solution: Dissolve 5 mg of TMSI in a mixed solution containing 475 μL of isopropanol (IPA) and 25 μL of water (volume ratio 19:1), and stir thoroughly until completely dissolved to obtain the TMSI post-treatment solution.

[0028] S3. Sample Preparation: A 1 cm × 1 cm FTO glass substrate was ultrasonically cleaned for 30 min. 40 μL of filtered perovskite solution was then deposited onto the FTO substrate using spin-coating to prepare a perovskite thin film. Specific spin-coating parameters were: acceleration from 200 rpm / s to 1000 rpm in 10 s, followed by acceleration from 2000 rpm / s to 6000 rpm / s in 30 s.

[0029] S4. Post-treatment of the perovskite film: The perovskite film is post-treated using the TMSI post-treatment solution prepared in step S2. Specifically, the post-treatment solution is spin-coated onto the perovskite film at a speed of 3000 r / min for 40 s. At the 15th second, 40 μL of matte salt post-treatment solution is added dropwise. The treated film is then transferred to a humidity chamber with 50% humidity and stored for 12 hours to allow for complete Oswald ripening and secondary crystallization, resulting in the post-treated perovskite film.

[0030] Example 3 This example provides a method for preparing a perovskite thin film, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0202 g cesium iodide (CsI), 0.0202 g MAI, 0.101 g formamidinium hydroiodate (FAI) and 0.808 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 5:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of about 1.50 mmol / mL.

[0031] S2. Preparation of the trimethylsulfonium salt post-treatment solution: Dissolve 2.5 mg of TMSBr in a mixed solution containing 454 μL of isopropanol (IPA) and 45 μL of water (volume ratio 10:1), and stir thoroughly until completely dissolved to obtain the TMSBr post-treatment solution.

[0032] S3. Sample Preparation: A 1 cm × 1 cm FTO glass substrate was ultrasonically cleaned for 30 min. 50 μL of filtered perovskite solution was then deposited onto the FTO substrate using spin coating to prepare a perovskite thin film. Specific spin coating parameters were: acceleration from 200 rpm / s to 1000 rpm over 10 s, followed by acceleration from 2000 rpm / s to 6000 rpm / s over 30 s.

[0033] S4. Post-treatment of the perovskite film: The perovskite film was post-treated using the TMSBr post-treatment solution prepared in step S2. Specifically, the post-treatment solution was spin-coated onto the perovskite film at a speed of 3000 r / min for 40 s. At the 15th second, 50 μL of sulfonium salt post-treatment solution was added dropwise. The treated film was then transferred to a humidity chamber with 60% humidity and stored for 10 hours to allow for complete Oswald ripening and secondary crystallization, resulting in the post-treated perovskite film.

[0034] Example 4 This example provides a method for preparing a perovskite thin film, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0130 g cesium iodide (CsI), 0.0239 g MAI, 0.1376 g formamidinium hydroiodate (FAI) and 0.461 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 5:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of 1.25 mmol / mL.

[0035] S2. Preparation of Trimethylsulfonium Salt Post-treatment Solution: Dissolve 7.5 mg of TMSI in a mixed solution containing 454 μL of isopropanol (IPA) and 45 μL of water (volume ratio 10:1), and stir thoroughly until completely dissolved to obtain the TMSI post-treatment solution.

[0036] S3. Sample Preparation: A 1 cm × 1 cm FTO glass substrate was ultrasonically cleaned for 30 min. 40 μL of filtered perovskite solution was then deposited onto the FTO substrate using spin-coating to prepare a perovskite thin film. Specific spin-coating parameters were: acceleration from 200 rpm / s to 1000 rpm in 10 s, followed by acceleration from 2000 rpm / s to 6000 rpm / s in 30 s.

[0037] S4. Post-treatment of the perovskite film: The perovskite film is post-treated using the TMSI post-treatment solution prepared in step S2. Specifically, the post-treatment solution is spin-coated onto the perovskite film at a speed of 3000 r / min for 40 s. At the 15th second, 40 μL of matte salt post-treatment solution is added dropwise. The treated film is then transferred to a humidity chamber with 50% humidity and stored for 12 hours to allow for complete Oswald ripening and secondary crystallization, resulting in the post-treated perovskite film.

[0038] Example 5 This example provides a method for preparing a solar cell device, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0130 g cesium iodide (CsI), 0.0239 g MAI, 0.1376 g formamidinium hydroiodate (FAI) and 0.461 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 4:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of 1.25 mmol / mL.

[0039] S2. Preparation of the trimethylsulfonium salt post-treatment solution: Dissolve 5 mg of TMSBr in a mixed solution containing 475 μL of isopropanol (IPA) and 25 μL of water (volume ratio 19:1), and stir thoroughly until completely dissolved to obtain the TMSBr post-treatment solution.

[0040] Preparation of S3 and p-MPSCs (1) Etching and cleaning of FTO glass: The FTO glass was etched with a CO2 laser to ensure that the positive and negative electrodes could not be directly connected. The etched glass was then ultrasonically cleaned for 10 min each with detergent, deionized water and anhydrous ethanol, and dried before use.

[0041] (2) Preparation of TiO2 dense layer: The cleaned FTO glass is covered with a mask and placed on a hot stage and heated to 450°C. The TiO2 dense layer solution is sprayed onto the FTO glass by spray pyrolysis. The FTO glass is then allowed to cool naturally to room temperature to achieve the preparation of TiO2 dense layer.

[0042] (3) Preparation of the three-layer mesoporous membrane: TiO2 slurry was deposited onto the FTO / c-TiO2 substrate by screen printing. After standing for 2 hours to allow the slurry to spread, it was dried on a hot stage at 75°C and then sintered at 500°C for 40 minutes on a programmable hot stage. After natural cooling, the mp-TiO2 layer was prepared. Next, the mp-ZrO2 layer was deposited again by screen printing and dried on a hot stage after standing for 20 minutes. Finally, C slurry was deposited onto the FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 substrate by screen printing. After drying on a hot stage at 75°C, it was sintered at 400°C for 40 minutes and then naturally cooled to room temperature to achieve the multilayer porous membrane structure of FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C.

[0043] (4) Filling of perovskite precursor solution: 3.6 μL of the perovskite precursor solution prepared in step S1 was drop-coated on one side of the carbon electrode edge of the prepared porous membrane. After 5 min of static infiltration, it was placed on a hot plate at 56℃ for annealing for 18 h and then the solvent was removed to achieve crystallization of perovskite and finally achieve the preparation of p-MPSCs.

[0044] S4. Post-treatment of p-MPSCs: 10 μL of the TMSBr post-treatment solution prepared in step S2 was added to the prepared p-MPSCs. After the solution diffused for 1 min, the device was placed on a hot stage at 100℃ and dried for 2 min to complete the fabrication of the solar cell device.

[0045] Example 6 This example provides a method for preparing a solar cell device, including the following steps: S1, Preparation of perovskite precursor solution: Weigh 0.0101 g chloromethylamine (MACl), 0.0130 g cesium iodide (CsI), 0.0239 g MAI, 0.1376 g formamidinium hydroiodate (FAI) and 0.461 g lead iodide (PbI2) into a reagent bottle, and add 800 μL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 4:1. Then stir on a magnetic stirrer at 55°C for 1 h to obtain a perovskite precursor solution with a concentration of 1.25 mmol / mL.

[0046] S2. Preparation of Trimethylsulfonium Salt Post-treatment Solution: Dissolve 5 mg of TMSI in a mixed solution containing 475 μL of isopropanol (IPA) and 25 μL of water (volume ratio 19:1), and stir thoroughly until completely dissolved to obtain the TMSI post-treatment solution.

[0047] Preparation of S3 and p-MPSCs (1) Etching and cleaning of FTO glass: The FTO glass was etched with a CO2 laser to ensure that the positive and negative electrodes could not be directly connected. The etched glass was then ultrasonically cleaned for 10 min each with detergent, deionized water and anhydrous ethanol, and dried before use.

[0048] (2) Preparation of TiO2 dense layer: The cleaned FTO glass is covered with a mask and placed on a hot stage and heated to 450°C. The TiO2 dense layer solution is sprayed onto the FTO glass by spray pyrolysis. The FTO glass is then allowed to cool naturally to room temperature to achieve the preparation of TiO2 dense layer.

[0049] (3) Preparation of the three-layer mesoporous membrane: TiO2 slurry was deposited onto the FTO / c-TiO2 substrate by screen printing. After standing for 2 hours to allow the slurry to spread, it was dried on a hot stage at 75°C and then sintered at 500°C for 40 minutes on a programmable hot stage. After natural cooling, the mp-TiO2 layer was prepared. Next, the mp-ZrO2 layer was deposited again by screen printing and dried on a hot stage after standing for 20 minutes. Finally, C slurry was deposited onto the FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 substrate by screen printing. After drying on a hot stage at 75°C, it was sintered at 400°C for 40 minutes and then naturally cooled to room temperature to achieve the multilayer porous membrane structure of FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C.

[0050] (4) Filling of perovskite precursor solution: 3.6 μL of the perovskite precursor solution prepared in step S1 was drop-coated on one side of the carbon electrode edge of the prepared porous membrane. After 5 min of static infiltration, it was placed on a hot plate at 56℃ for annealing for 18 h and then the solvent was removed to achieve crystallization of perovskite and finally achieve the preparation of p-MPSCs.

[0051] S4. Post-treatment of p-MPSCs: 10 μL of the TMSI post-treatment solution prepared in step S2 was added to the prepared p-MPSCs. After the solution diffused for 1 min, the device was placed on a hot stage at 100℃ and dried for 2 min to complete the fabrication of the solar cell device.

[0052] Comparative Example 1 This comparative example provides a method for preparing a perovskite thin film, including the following steps: The only difference between this comparative example and Example 1 is that the post-treatment solution is a mixed solution of IPA and water in a volume ratio of 19:1. The remaining steps are the same as those in Example 1.

[0053] Comparative Example 2 This comparative example provides a method for preparing a perovskite thin film, including the following steps: The only difference between this comparative example and Example 1 is that the sulfonium salt in the post-treatment solution is dimethylphenylethyl sulfonium iodide, and the other steps are the same as in Example 1.

[0054] Comparative Example 3 This comparative example provides a method for preparing a solar cell device, including the following steps: The only difference between this comparative example and Example 3 is that the post-treatment solution is a mixed solution of IPA and water in a volume ratio of 19:1, and the other steps are the same as those in Example 3.

[0055] Comparative Example 4 This comparative example provides a method for preparing a solar cell device, including the following steps: The only difference between this comparative example and Example 3 is that the sulfonium salt in the post-treatment solution is dimethylphenylethyl sulfonium iodide, and the other steps are the same as in Example 3.

[0056] In Experiment 1, the microstructure of the perovskite films prepared in Examples 1-2 and Comparative Examples 1-2 of the present invention was characterized by scanning electron microscopy (SEM).

[0057] The microstructure characterization results of the perovskite films in Examples 1-2 and Comparative Example 1 are shown in Figures 1a, b, and c. As can be seen from the figures, the perovskite films post-treated with TMSBr or TMSI have larger grain sizes and higher crystallinity. This is because trimethylsulfonium salt interacts strongly with perovskite and has a certain hygroscopic capacity, allowing it to absorb moisture and dissolve the perovskite under humid conditions. Simultaneously, due to the difference in surface free energy between large and small grains, small grains undergo a dynamic process where dissolution exceeds crystallization until they disappear, while large grains undergo a dynamic process where crystallization exceeds dissolution. Ultimately, this achieves Ohlwald ripening of the perovskite, resulting in a perovskite film with high crystallinity, few grain boundaries, and large grain sizes.

[0058] The microstructure characterization results of the perovskite films of Comparative Example 1 and Comparative Example 2 are shown in Figure 2. Comparative Example 2 uses a hydrophobic sulfonium salt, dimethylphenylethyl sulfonium iodide (DMPESI), which can interact strongly with perovskite. As shown in Figure 2, the perovskite film treated with DMPESI did not undergo Oswald ripening. This is attributed to the fact that even though there is a strong interaction between DMPESI and perovskite, the hydrophobic properties of DMPESI cannot absorb moisture or provide a mass transfer environment, thus failing to induce Oswald ripening in the perovskite.

[0059] The crystal structure of the perovskite thin films prepared in Examples 1-2 and Comparative Example 1 of the present invention was characterized by X-ray diffraction test, and the characterization results are shown in Figure 1d.

[0060] Experimental Example 2 tested the performance of the solar cell devices prepared in Examples 5-6 and Comparative Example 3 of this invention. This test used a testing system consisting of a solar simulator and a digital source meter to record the current data of the solar cells at different voltages. Based on the light intensity during the test and the set test area, the current density-voltage curve (JV curve) was calculated, as shown in Figure 3. From the JV curve, data such as open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), photoelectric conversion efficiency (PCE), and series resistance (RS) were obtained. The applied voltage range was 1.2 to -0.2 V, the scan step size was 0.01 V, and the dwell time was 0.04 s. Unless otherwise specified, the data listed are generally the reverse scan data from positive voltage to negative voltage. The light intensity was calibrated to a standard solar intensity (AM1.5 G, 100 mW / cm²) using a standard silicon cell. Because the printed edges are relatively rough and there may be errors in the printing position each time, the active area of ​​the device may be inconsistent. The test area is standardized based on the mask covering the battery, generally using an area of ​​0.1 cm². 2 The test was conducted using a circular light-blocking mask with a clear aperture. Alternatively, square or rectangular masks of different sizes can be selected depending on the device size or the required test area. The test results are shown in the table below.

[0061] Table 1. Statistical analysis of average performance parameters of solar cell devices obtained in Examples 5-6 and Comparative Example 3

[0062] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a perovskite thin film, characterized in that, include: A perovskite precursor solution and a trimethyl sulfonate post-treatment solution were prepared. The perovskite precursor solution was used to form a perovskite film on a substrate. The formed perovskite film was then post-treated with the trimethyl sulfonate post-treatment solution to obtain a large-size perovskite film.

2. The preparation method according to claim 1, characterized in that, The perovskite precursor solution is prepared by dissolving chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide in a first solvent; and / or, the mass ratio of chloromethylamine, cesium iodide, methylamine iodate, formamidinium hydroiodate, and lead iodide is 0.5~1:0.5~1:1~2:5~10:40~50; and / or, the first solvent includes N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4~5:1; and / or, the concentration of the obtained perovskite precursor solution is 1~2 mmol / mL.

3. The preparation method according to claim 1, characterized in that, The trimethyl sulfonium salt post-treatment solution includes a trimethyl sulfonium salt and a second solvent, wherein the concentration of the trimethyl sulfonium salt is 5-15 g / L; and / or, the trimethyl sulfonium salt includes, but is not limited to, TMSBr and TMSI; and / or, the second solvent includes isopropanol and water in a volume ratio of 10-20:

1.

4. The preparation method according to claim 1, characterized in that, The substrate is an FTO glass substrate; the perovskite film is formed by spin-coating and depositing a perovskite precursor solution onto the FTO glass substrate; and / or, the amount of perovskite precursor solution added is 40-50 μL / cm³. 2 .

5. The preparation method according to claim 1, characterized in that, The post-treatment method for the perovskite film is as follows: a trimethyl sulfonate post-treatment solution is added to the perovskite film by spin coating, and kept in an environment with an air humidity of 50%-60% for 10-12 hours; and / or, the dropwise addition rate of the trimethyl sulfonate post-treatment solution is 40-50 μL / cm. 2 .

6. A method for fabricating a solar cell device, characterized in that, Includes the following steps: A matrix intermediate with a multilayer porous film structure of c-TiO2 / mp-TiO2 / mp-ZrO2 / C was prepared. The matrix intermediate was structured as matrix / mp-TiO2 / mp-ZrO2 / C. The prepared intermediate was filled with a perovskite precursor solution and then post-treated with a trimethyl sulfonium salt post-treatment solution to obtain a solar cell device.

7. The preparation method according to claim 6, characterized in that, The perovskite precursor solution is prepared by the preparation method described in claim 2; the trimethyl sulfonate post-treatment solution is prepared by the preparation method described in claim 3.

8. The preparation method according to claim 6, characterized in that, The method for preparing the matrix intermediate structure includes the following steps: depositing a dense TiO2 layer on a substrate to form a matrix, wherein the substrate is FTO glass; the preferred preparation process of the matrix includes: etching and cleaning the FTO glass, heating it to 400~500℃, spraying a TiO2 dense layer solution onto the FTO glass, cooling to complete the preparation of the TiO2 dense layer, and obtaining an FTO / c-TiO2 matrix; depositing TiO2 slurry onto the above FTO / c-TiO2 matrix, drying it, sintering it and holding it at a certain temperature, and cooling to complete the preparation of the mp-TiO2 layer, wherein the sintering temperature is 500~550℃ and the holding time is 0.5~1h; continuing to deposit mp-ZrO2 onto the above mp-TiO2 layer, allowing it to stand and dry to obtain an FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 structure, and depositing C slurry on the FTO / c-TiO2 / mp-TiO2 / On an mp-ZrO2 substrate, after drying, sintering and holding at a certain temperature are carried out, and after cooling, a matrix intermediate with the structure FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C is obtained. The sintering temperature is 400~450℃ and the holding time is 0.5~1h.

9. The preparation method according to claim 8, characterized in that, The thickness of the dense TiO2 layer is 20-25 nm, the thickness of the mp-TiO2 layer is 800-900 nm, the thickness of the mp-ZrO2 layer is 2-3 μm; and / or, the total thickness of the multilayer porous film structure of FTO / c-TiO2 / mp-TiO2 / mp-ZrO2 / C is 25-30 μm.

10. The preparation method according to claim 6, characterized in that, The filling of the perovskite precursor solution includes: drop-coating the perovskite precursor solution onto one side of the carbon electrode of the prepared matrix intermediate, allowing it to stand and permeate for 5-10 min, and then annealing it at 50-60℃ for 18-20 h; and / or, the drop-coating amount of the perovskite precursor solution is 3-4 μL / cm. 2 ; and / or, the post-processing method includes: adding a trimethyl sulfonium salt post-processing solution to the obtained multilayer porous membrane structure intermediate, and drying the solution at 90~110℃ for 2~3 min after diffusion.

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