Perovskite thin film material, preparation method thereof and application of perovskite thin film material in perovskite solar cell

Abstract

The invention belongs to the technical field of solar cells, and provides a perovskite thin film material, a preparation method thereof and application of the perovskite thin film material in a perovskite solar cell. According to the perovskite thin film material, the perovskite precursor and the dopant are adopted as main raw material components of the perovskite thin film material, the provided perovskite thin film material can be further used for preparing a perovskite solar cell, and the trifluoromethylthio benzene compound dopant can effectively perform defect passivation on defects in crystals and grain boundaries; the non-radiative recombination of carriers is reduced, the energy level of the electron transport layer is matched, and the cell efficiency and the photo-thermal stability are improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a perovskite thin film material, its preparation method, and its application in perovskite solar cells. Background Technology

[0002] Perovskite solar cells (PSCs), as a promising new solar cell technology, possess advantages such as high photoelectric conversion efficiency, low cost, and ease of fabrication, showing great potential in the renewable energy field. However, the commercial application of PSCs is severely limited by device stability, primarily due to inherent defects in the perovskite thin film material itself. Perovskite thin films are typically prepared using solvent methods, resulting in numerous defects at their grain boundaries. These defects in the perovskite crystal lead to problems such as charge localization, nonradiative recombination, and crystal degradation, hindering the separation and transport of photogenerated carriers and severely impacting the long-term stability and photoelectric conversion efficiency of the device. In particular, the presence of numerous edge ion vacancy defects on the surface or at grain boundaries (GBs) of perovskite crystals can trigger adverse reactions such as carrier recombination and charge rearrangement, making the perovskite thin film susceptible to gradual degradation and damage under the influence of water, heat, and light. This results in poor photothermal stability, a continuous decline in cell efficiency under operating conditions, and a shortened lifespan.

[0003] Chinese patent (publication number CN114649480A) solves the problem of perovskite solar cells' easy decomposition under external conditions by doping them with perfluorinated organic compounds. Chinese patent (publication number CN114122263A) solves the degradation problem of perovskite thin film materials under water and oxygen conditions by introducing thiocyanate ions into perovskite solar cells. However, these existing technologies have relatively limited effects on improving film quality, and they still do not solve the problem of severe non-radiative recombination losses caused by the imperfect energy level arrangement between the perovskite thin film material and the electron transport layer.

[0004] In view of the above problems, there is an urgent need to develop a perovskite solar cell with excellent photoelectric conversion performance and high photothermal stability. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a perovskite thin film material, its preparation method, and its application in perovskite solar cells. The perovskite thin film material provided by this invention can be further used to prepare perovskite solar cells, exhibiting not only excellent photoelectric conversion performance but also high photothermal stability and long-term stability (the efficiency of the perovskite solar cell can still maintain approximately 78-96% of its original efficiency over a period of up to 1000 hours).

[0006] A first aspect of the present invention provides a perovskite thin film material.

[0007] Specifically, a perovskite thin film material comprises the following raw material components: Perovskite precursors and dopants; The dopants include trifluoromethylthiobenzene compounds.

[0008] This invention utilizes trifluoromethylthiobenzene compounds as dopants. The strongly coordinated Lewis basic functional group sulfur can form strong coordination with perovskite, regulating perovskite nucleation and crystal growth rates, passivating lattice defects, and stabilizing the perovskite α phase, resulting in a uniform and dense perovskite thin film. The S-CF3 groups enhance intermolecular stacking, forming an ordered and dense passivation interface layer at the perovskite grain boundaries, improving the quality of the perovskite absorber layer, increasing film stability, and preventing water ingress and decomposition, thereby achieving higher device efficiency and stability. Furthermore, the perovskite thin film material can be used to fabricate perovskite solar cells. The dopant molecules can match the energy levels of the electron transport layer (such as C60), improving charge transport synergistically and solving the problems of low cell efficiency and poor stability.

[0009] Preferably, the dopant includes at least one of 3-(trifluoromethylthio)phenyl isothiocyanate, trifluoromethylthiobenzoic acid, trifluoromethylthioaniline, and 4-(trifluoromethylthio)phenyl isothiocyanate.

[0010] The structural formula of 3-(trifluoromethylthio)phenyl isothiocyanate is as follows: .

[0011] Preferably, the perovskite precursor comprises PbI2.

[0012] Preferably, the perovskite precursor further includes at least one of CsI, FAI, MABr, and PbBr2.

[0013] Preferably, the molar amount of the dopant accounts for 0.3-1.5% of the molar amount of the perovskite precursor.

[0014] More preferably, the molar amount of the dopant accounts for 0.5-0.9% of the molar amount of the perovskite precursor.

[0015] More preferably, the molar amount of the dopant accounts for 0.7% of the molar amount of the perovskite precursor.

[0016] A second aspect of the present invention provides a method for preparing a perovskite thin film material.

[0017] A method for preparing a perovskite thin film material includes the following steps: The perovskite precursor and solvent are mixed to obtain a perovskite precursor solution, and then a dopant is added to obtain a doping solution. The doping solution is coated on a carrier and subjected to a first annealing to obtain the perovskite thin film material.

[0018] Preferably, the carrier is a conductive substrate.

[0019] More preferably, the carrier is a glass conductive substrate.

[0020] More preferably, the carrier is a glass conductive substrate containing a hole transport layer.

[0021] Preferably, the temperature of the first annealing is 90-110°C, and / or the time of the first annealing is 10-30 min.

[0022] Preferably, the solvent is dimethyl sulfoxide and / or N,N-dimethylformamide.

[0023] A third aspect of the present invention provides an application of a perovskite thin film material.

[0024] Application of a perovskite thin film material in the fabrication of perovskite solar cells.

[0025] A fourth aspect of the present invention provides a perovskite solar cell.

[0026] A perovskite solar cell includes a conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer, and a metal electrode layer stacked sequentially, wherein the perovskite layer is made of the perovskite thin film material.

[0027] Preferably, the conductive substrate is fluorine-doped tin oxide transparent conductive oxide (TCO) glass or indium tin oxide (ITO) glass.

[0028] More preferably, the conductive substrate is fluorine-doped tin oxide transparent conductive oxide (TCO) glass.

[0029] The perovskite solar cell provided by this invention, when light is incident on the surface of the perovskite solar cell, if the energy of the photon is greater than the bandgap of the perovskite layer, it excites the perovskite to generate charge carriers. These free charge carriers are extracted by the built-in electric field formed by the heterojunction contact between the hole transport layer and the electron transport layer, and transported to the conductive substrate and the two ends of the metal electrode, thereby forming a photocurrent in the external circuit, and thus realizing solar power generation.

[0030] The fifth aspect of the present invention provides a method for preparing a perovskite solar cell.

[0031] A method for fabricating a perovskite solar cell includes the following steps: (1) Fabricate a hole transport layer on a conductive substrate; (2) Mix the perovskite precursor and solvent to obtain a perovskite precursor solution, then add a dopant to obtain a doping solution, coat the doping solution on the surface of the hole transport layer, and perform a second annealing to obtain a perovskite layer. (3) An electron transport layer and a metal electrode layer are sequentially fabricated on the surface of the perovskite layer.

[0032] Preferably, in step (1), the hole transport layer is fabricated by the following steps: coating the surface of the conductive substrate with organic small molecules and then performing a third annealing.

[0033] Preferably, in step (1), the temperature of the third annealing is 110-130°C, and / or the time of the third annealing is 20-40 min.

[0034] Preferably, the organic small molecule includes N4,N4'-bis(naphthyl-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine and / or (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid (MEO-2PACZ).

[0035] More preferably, the organic small molecule is N4,N4'-bis(naphthyl-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine.

[0036] Fluorine-doped tin oxide transparent conductive oxide (TCO) glass was used as the conductive substrate, and N4,N4'-di(naphthyl-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine was used as the hole transport layer to extract holes and increase the interface connection effect, improve the energy level arrangement and enhance stability.

[0037] Preferably, in step (1), the conductive substrate is cleaned before use.

[0038] Preferably, the cleaning process includes performing UV treatment, ozone cleaning, and high-temperature treatment in sequence.

[0039] Preferably, the UV treatment and ozone cleaning times are 10-30 min and 10-30 min, respectively.

[0040] Preferably, the high-temperature treatment temperature is 140-160°C, and / or the high-temperature treatment time is 10-30 min.

[0041] Preferably, in step (2), the temperature of the second annealing is 90-110°C, and / or the time of the second annealing is 10-30 min.

[0042] Preferably, in step (2), the solvent includes dimethyl sulfoxide (DMSO) and / or N,N-dimethylformamide (DMF).

[0043] More preferably, in step (2), the solvent is dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:(5-7). This is beneficial for perovskite crystallization.

[0044] Preferably, in step (2), the perovskite precursor includes cesium iodide (CsI), formamidine iodide (FAI), lead iodide (PbI2), methylamine bromide (MABr), and lead bromide (PbBr2). Cesium iodide (CsI), formamidine iodide (FAI), and lead iodide (PbI2) are added to a solvent to prepare a first solution. Then, methylamine bromide (MABr) and lead bromide (PbBr2) are added to a solvent to prepare a second solution. The first solution and the second solution are then mixed to obtain a perovskite precursor solution.

[0045] Preferably, in step (3), the fabrication of the electron transport layer includes the following steps: sequentially fabricating a C60 film and a tin oxide film on the surface of the perovskite layer.

[0046] More preferably, in step (3), the fabrication of the electron transport layer includes the following steps: sequentially depositing a C60 film and an atomic layer depositing a tin oxide film on the surface of the perovskite layer.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses perovskite precursors and dopants as the main raw material components of perovskite thin film materials. The perovskite thin film materials provided can be further used to prepare perovskite solar cells. The dopants can effectively passivate defects and grain boundaries within the crystal, reduce nonradiative recombination of charge carriers, match the energy levels of the electron transport layer, and improve the cell efficiency and photothermal stability. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the perovskite solar cell prepared in Application Example 1 of the present invention; Figure 2 The graph shows the cell efficiency test results of the perovskite solar cells prepared in Application Examples 1-5 and Comparative Application Example 1. Figure 3 The graph shows the stability test results of the perovskite solar cells prepared in Application Examples 1-5 and Comparative Application Example 1. Detailed Implementation

[0049] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0050] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0051] Unless otherwise specified in the examples or comparative examples, the conditions shall be performed under normal conditions or conditions recommended by the manufacturer.

[0052] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0053] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0054] Example 1 A method for preparing a perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI, and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to the mixed solution of DMF and DMSO to prepare the second solution. Finally, mix the first solution with the second solution to obtain the perovskite precursor solution. The chemical formula of the perovskite precursor is MABr. 0.05 (Cs 0.05 FA 0.95 ) 0.95 Pb(I 0.95 Br 0.05 3.

[0055] (2) Doping: 3-(trifluoromethylthio)phenyl isothiocyanate is added to the perovskite precursor solution, wherein the molar amount of 3-(trifluoromethylthio)phenyl isothiocyanate accounts for 0.5% of the molar amount of the perovskite precursor, and a doped solution is obtained.

[0056] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0057] Example 2 A method for preparing a perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0058] (2) Doping: 3-(trifluoromethylthio)phenyl isothiocyanate is added to the perovskite precursor solution, wherein the molar amount of 3-(trifluoromethylthio)phenyl isothiocyanate accounts for 0.6% of the molar amount of the perovskite precursor, and a doped solution is obtained.

[0059] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0060] Example 3 A method for preparing a perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0061] (2) Doping: 3-(trifluoromethylthio)phenyl isothiocyanate is added to the perovskite precursor solution, wherein the molar amount of 3-(trifluoromethylthio)phenyl isothiocyanate accounts for 0.7% of the molar amount of the perovskite precursor, and a doped solution is obtained.

[0062] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0063] Example 4 A method for preparing a perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0064] (2) Doping: 3-(trifluoromethylthio)phenyl isothiocyanate is added to the perovskite precursor solution, wherein the molar amount of 3-(trifluoromethylthio)phenyl isothiocyanate accounts for 0.8% of the molar amount of the perovskite precursor, and a doped solution is obtained.

[0065] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0066] Example 5 A method for preparing a perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0067] (2) Doping: Add 3-(trifluoromethylthio)phenyl isothiocyanate as a dopant to the perovskite precursor solution. The molar amount of 3-(trifluoromethylthio)phenyl isothiocyanate accounts for 0.9% of the molar amount of the perovskite precursor to obtain a doped solution.

[0068] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0069] Example 6 A method for preparing a perovskite thin film material differs from Example 3 in that, in step (2), the dopant 3-(trifluoromethylthio)isothiocyanate is replaced with an equimolar amount of the dopant trifluoromethylthiobenzoic acid.

[0070] The preparation method of the above-mentioned perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0071] (2) Doping: Trifluoromethylthiobenzoic acid is added to the perovskite precursor solution, with the molar amount of trifluoromethylthiobenzoic acid accounting for 0.7% of the molar amount of the perovskite precursor, to obtain a doped solution.

[0072] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0073] Example 7 A method for preparing a perovskite thin film material differs from Example 3 in that, in step (2), the dopant 3-(trifluoromethylthio)isothiocyanate is replaced with an equimolar amount of the dopant trifluoromethylthioaniline.

[0074] The preparation method of the above-mentioned perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0075] (2) Doping: Trifluoromethylthioaniline is added to the perovskite precursor solution, with the molar amount of trifluoromethylthioaniline accounting for 0.7% of the molar amount of the perovskite precursor, to obtain a doped solution.

[0076] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0077] Example 8 A method for preparing a perovskite thin film material differs from Example 3 in that, in step (2), the dopant 3-(trifluoromethylthio)phenyl isothiocyanate is replaced with an equimolar amount of dopant 4-(trifluoromethylthio)phenyl isothiocyanate.

[0078] The preparation method of the above-mentioned perovskite thin film material includes the following steps: (1) Preparation of perovskite precursor solution: Take 0.112 mmol cesium iodide, 1.4 mmol lead iodide, 1.288 mmol formamidinium iodide, 0.112 mmol lead bromide, and 0.224 mmol methylamine bromide. Solvent: dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:6. First, add CsI, FAI and PbI2 to a mixed solution of DMF and DMSO to prepare the first solution. Then, add MABr and PbBr2 to a mixed solution of DMF and DMSO to prepare the second solution. Mix the first solution and the second solution to obtain the perovskite precursor solution.

[0079] (2) Doping: 4-(trifluoromethylthio)phenyl isothiocyanate was added to the perovskite precursor solution, with the molar amount of 4-(trifluoromethylthio)phenyl isothiocyanate accounting for 0.7% of the molar amount of the perovskite precursor, to obtain a doped solution.

[0080] (3) Annealing: The doping solution was spin-coated onto the hole transport layer and annealed at 100°C for 20 min to obtain the perovskite thin film material.

[0081] Comparative Example 1 A method for preparing a perovskite thin film material differs from Example 1 in that, in step (2), phenyl 3-(trifluoromethylthio)isothiocyanate is not added.

[0082] Application Example 1 A perovskite solar cell, such as Figure 1 As shown, the perovskite solar cell includes a conductive substrate (fluorine-doped tin oxide TCO glass, i.e., FTO glass), a hole transport layer (HTL), a perovskite layer (PVK), an electron transport layer (ETL), and a metal electrode layer (Ag) stacked sequentially. The perovskite layer is the perovskite thin film material used in Example 1. The specific fabrication method of the perovskite solar cell includes the following steps: (1) Prepare FTO glass as a substrate and perform UV treatment for 20 min, ozone cleaning for 20 min and high temperature treatment at 150℃ for 20 min in sequence; (2) The organic small molecule N4,N4'-bis(naphthyl-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine was spin-coated on fluorine-doped tin oxide glass, annealed at 120°C for 30 min, and cooled to room temperature to obtain a hole transport layer film. (3) The doping solution prepared in step (2) of Example 1 was spin-coated onto the hole transport layer film and annealed at 100°C for 20 min to form a perovskite layer; (4) A C60 film is deposited on the perovskite layer, and then a tin oxide film is deposited on the C60 film by atomic layer deposition, and a metal electrode layer is deposited on the tin oxide film.

[0083] Application Example 2-5 Application Examples 2-5 provide perovskite solar cells, which differ from Application Example 1 in that the doping solution obtained in step (2) of Example 1 is replaced with the doping solution obtained in step (2) of Example 2-5.

[0084] Comparative Application Example 1 Comparative Application Example 1 provides a perovskite solar cell. The difference between Comparative Application Example 1 and Application Example 1 is that the doping solution obtained in step (2) of Example 1 is replaced with the doping solution in step (2) of Comparative Example 1.

[0085] Product effectiveness test 1. Photoelectric conversion performance of perovskite solar cells (1) Test method Power conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) were all tested using ENLITECH:SS-X50, IVS-KA6000.

[0086] (2) Test results The photoelectric conversion performance test results of perovskite solar cells in various application examples and comparative application examples are as follows: Figure 2 As shown in Table 1.

[0087] Table 1 Performance test results of perovskite solar cells in various application examples and comparative application examples.

[0088] From the above table and Figure 2 It can be seen that the perovskite solar cells in Application Examples 1-8 all exhibit good photoelectric conversion efficiency. Application Examples 1-5 all used different concentrations of phenyl 3-(trifluoromethylthio)isothiocyanate as a dopant. As the dopant content gradually increased, the photoelectric conversion efficiency also increased, and the degree of improvement gradually became greater. However, when the dopant content continued to increase, as in Application Examples 4 and 5, the photoelectric conversion efficiency decreased due to the higher dopant content. Application Example 3 showed the best performance.

[0089] Application Examples 3 and 6-8 all used different types of dopants with the same content. Application Example 3 exhibited superior photoelectric conversion performance. The 3-(trifluoromethylthio)isothiocyanate dopant, with its strongly coordinated Lewis basic functional groups nitrogen and sulfur, could form strong coordination with perovskite, regulating perovskite nucleation and crystal growth rates, passivating lattice defects, and stabilizing the perovskite α phase, resulting in a uniform and dense perovskite film. Its aromatic amine side chains and S-CF3 groups enhanced intermolecular stacking, forming an ordered and dense passivated interface layer at the perovskite grain boundaries, thus improving the perovskite absorption layer. Improving film quality enhances film stability and prevents water ingress that could lead to decomposition, thereby achieving higher device efficiency and stability. Thiocyanate structures replace halides in the perovskite framework near the bottom of the perovskite film, effectively suppressing defect recombination and improving the device's on-state voltage and fill factor. The meta-thiocyanate molecules in the dopant improve the dipole moment of trifluoromethylthiophenyl ester, resulting in better alignment and allowing the 3-(trifluoromethylthio)isothiophenyl ester dopant molecules to match the energy levels of the electron transport layer (such as C60). This synergistic effect improves charge transport and solves the problems of low battery efficiency and poor stability.

[0090] In contrast, the perovskite layer in Application Example 1, which did not introduce dopants, had more film defects and lower open-circuit voltage and power conversion efficiency.

[0091] Compared to Comparative Application Example 1, the Voc of the perovskite solar cells in Application Examples 1-8 is improved, with an increase of approximately 30-55mV compared to Comparative Application Example 1. This means that the cells in Application Examples 1-8 can generate higher voltages under the same illumination conditions, thereby improving the overall performance of the perovskite solar cells. Furthermore, the FF did not decrease significantly, current transmission was improved, Jsc was increased, and overall PCE was improved to varying degrees.

[0092] 2. Photothermal stability test of perovskite solar cells (1) Test method The perovskite solar cells of each application example and the comparative application example were placed in a nitrogen atmosphere at 70°C for 1000 hours for photothermal stability testing. Then, the power conversion efficiency (PCE) retention rate (%) of the perovskite solar cells at different time points during this process was measured. Power conversion efficiency (PCE) retention rate (%) = Efficiency after photothermal aging / Initial efficiency × 100%.

[0093] (2) Test results The stability test results of perovskite solar cells in various application examples and comparative application examples are as follows: Figure 3 As shown in Table 2.

[0094] Table 2. Stability test results of perovskite solar cells in various application examples and comparative application examples (unit: %)

[0095] From the above table 2 and Figure 3 As can be seen, in Application Examples 1-8, the efficiency of the perovskite solar cells can still maintain approximately 78-96% of the original efficiency over a period of up to 1000 hours.

[0096] In contrast to Application Example 1, after 1000 hours of photothermal stability testing under a solar irradiance and a nitrogen atmosphere at 70°C, the stability results of the tested device showed that its efficiency could only maintain 64.5% of the original efficiency.

[0097] Compared to Comparative Application Example 1, Application Examples 1-5 improved the stability of perovskite solar cells to varying degrees by adding different amounts of 3-(trifluoromethylthio)phenyl isothiocyanate to the perovskite layer, demonstrating excellent long-term stability. This indicates that 3-(trifluoromethylthio)phenyl isothiocyanate helps to slow down the performance degradation of perovskite solar cells, enabling them to maintain a high performance level during long-term use.

[0098] Application Examples 1-5 all used different concentrations of phenyl 3-(trifluoromethylthio)isothiocyanate as a dopant, with Application Example 3 exhibiting the best stability. Application Examples 3 and 6-8 all used different types of dopant in the same amount; the results show that Application Example 3, using phenyl 3-(trifluoromethylthio)isothiocyanate as a dopant, exhibited the best stability.

[0099] This invention modulates the nucleation and crystal growth rates by adding different amounts of 3-(trifluoromethylthio)phenyl isothiocyanate dopant to the perovskite precursor solution, forming a uniform and dense perovskite thin film. This improves the film quality of the perovskite layer, passivates defects and grain boundaries within the crystal, and enhances light absorption and carrier transport efficiency, thereby increasing the conversion efficiency of the solar cell. Furthermore, it matches the energy level of the C60 electron transport layer, reducing non-radiative recombination of carriers to improve the photothermal stability of the solar cell, thus enhancing the conversion efficiency and stability of the perovskite thin-film battery. In actual battery operation, decomposition under photothermal conditions is less likely to occur, while also reducing process complexity and improving process efficiency.

Claims

1. A perovskite thin film material, characterized in that, It includes the following raw material components: Perovskite precursors and dopants; The dopants include trifluoromethylthiobenzene compounds.

2. The perovskite thin film material according to claim 1, characterized in that, The perovskite precursor includes PbI2.

3. The perovskite thin film material according to claim 1, characterized in that, The dopant includes at least one of 3-(trifluoromethylthio)phenyl isothiocyanate, trifluoromethylthiobenzoic acid, trifluoromethylthioaniline, and 4-(trifluoromethylthio)phenyl isothiocyanate.

4. The method for preparing the perovskite thin film material according to any one of claims 1-3, characterized in that, Includes the following steps: The perovskite precursor and solvent are mixed to obtain a perovskite precursor solution, and then a dopant is added to obtain a doping solution. The doping solution is coated on a carrier and subjected to a first annealing to obtain the perovskite thin film material.

5. The preparation method according to claim 4, characterized in that, The temperature of the first annealing is 90-110℃, and / or the time of the first annealing is 10-30 min.

6. The use of the perovskite thin film material according to any one of claims 1-3 in the preparation of perovskite solar cells.

7. A perovskite solar cell, characterized in that, It includes a conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer and a metal electrode layer stacked sequentially, wherein the perovskite layer is made of the perovskite thin film material according to any one of claims 1-3.

8. The method for preparing the perovskite solar cell according to claim 7, characterized in that, Includes the following steps: (1) Fabricate a hole transport layer on a conductive substrate; (2) Mix the perovskite precursor and solvent to obtain a perovskite precursor solution, then add a dopant to obtain a doping solution, coat the doping solution on the surface of the hole transport layer, and perform a second annealing to obtain a perovskite layer. (3) An electron transport layer and a metal electrode layer are sequentially fabricated on the surface of the perovskite layer.

9. The preparation method according to claim 8, characterized in that, In step (2), the perovskite precursor includes cesium iodide, formamidine iodide, lead iodide, methylamine bromide and lead bromide. First, cesium iodide, formamidine iodide and lead iodide are added to a solvent to prepare a first solution. Then, methylamine bromide and lead bromide are added to a solvent to prepare a second solution. The first solution and the second solution are then mixed to obtain a perovskite precursor solution.

10. The preparation method according to claim 8, characterized in that, In step (3), the fabrication of the electron transport layer includes the following steps: sequentially fabricating a C60 film and a tin oxide film on the surface of the perovskite layer.

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