Perovskite thin film, perovskite solar cell and preparation method thereof

Abstract

The invention relates to the technical field of perovskite solar cells, in particular to a perovskite thin film, a perovskite solar cell and a preparation method of the perovskite thin film. The invention provides a preparation method of a perovskite thin film, which comprises the following steps: S1, mixing a perovskite thin film precursor, an additive and a solvent to obtain a precursor solution; the additive is prepared from 1-(2-fluorobenzyl)-1H-pyrazolo [3, 4-B] pyridine-3-formamidine hydrochloride; and S2, coating a substrate with the precursor solution, and annealing to obtain the perovskite thin film. According to the invention, 1-(2-fluorobenzyl)-1H-pyrazolo [3, 4-b] pyridine-3-formamidine hydrochloride with a multifunctional conjugated system is used as an additive to be introduced into a perovskite precursor solution, and abundant N atoms in a molecular structure and an aromatic heterocyclic conjugated system are utilized to form multiple hydrogen bonds with each other with components in the precursor, so that the perovskite performance is improved. And the crystallization process of the perovskite is effectively regulated and controlled.

Description

Technical Field

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

[0002] Organometal halide perovskite semiconductors have become a research hotspot in the photovoltaic field due to their excellent photoelectric properties. In recent years, thin-film solar cells based on these materials have developed rapidly, with their photoelectric conversion efficiency exceeding 27.3%, demonstrating enormous application potential. However, the realization of high-efficiency devices is highly dependent on the preparation of high-quality perovskite thin films, especially the "liquid-solid" phase transition process from the precursor liquid to the thin film. If this process is not properly controlled, it can easily lead to problems such as poor film crystal quality and lattice stress accumulation, which in turn can result in a large number of defects and interface barriers inside the device, seriously affecting the extraction, separation, and transport of charge carriers, ultimately restricting further improvement in the photovoltaic performance of the cell.

[0003] Currently, the crystallization control of perovskite thin films largely relies on traditional additives such as methylammonium chloride (MACl). However, these additives have significant limitations in their mechanism of action: on the one hand, their surface energy control ability is insufficient, making it difficult to achieve a precise balance of crystallization kinetics, easily leading to disordered crystal orientation and uneven grain size; on the other hand, chloride ions easily form volatile byproducts during annealing, not only causing component loss but also exacerbating internal defects in the film and impairing the long-term stability of the device. Therefore, existing methods are still insufficient in simultaneously optimizing the crystallization process and defect passivation, and there is an urgent need to develop novel additives to achieve a systematic improvement in the quality of perovskite film formation and optoelectronic performance. Summary of the Invention

[0004] This invention provides a perovskite thin film, a perovskite solar cell, and a method for preparing the same, in order to solve the problems mentioned above.

[0005] In a first aspect, the present invention provides a method for preparing a perovskite thin film, comprising the following steps: S1, mix the perovskite precursor, additives and solvent to obtain a precursor solution; The additives include 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-formamidinium hydrochloride; S2, the precursor solution is coated onto the substrate and annealed to obtain a perovskite thin film.

[0006] In one alternative embodiment, the substrate includes at least one of an electron transport layer substrate and a hole transport layer substrate.

[0007] In one optional embodiment, the ratio of the perovskite precursor, additive, and solvent is (400-1600) mg: (1-10) mg: (0.8-1.2) ml.

[0008] In one optional embodiment, the molar ratio of lead source, first organic amine salt, and second organic amine salt in the perovskite precursor is (0.8-1.2):(0.8-1.2):(0.2-0.5).

[0009] In one alternative embodiment, the coating thickness is 100-500 nm.

[0010] In one alternative embodiment, the coating includes spin coating; Optionally, the spin coating rotation speed is 5000-6000 rpm and the time is 30-50s; Optionally, the spin coating includes adding an antisolvent dropwise 7-12 seconds after the start of spin coating; Further optionally, the volume ratio of the antisolvent to the perovskite precursor solution is (0.6-1):(0.05-0.1). Further, optionally, the antisolvent includes anhydrous diethyl ether.

[0011] In one alternative embodiment, the lead source includes at least one of lead iodide, lead bromide, and lead chloride.

[0012] In one optional embodiment, the first organic amine salt includes at least one of formamidine halide and acetamidine halide; optionally, it is formamidine hydroiodate. In one optional embodiment, the second organic amine salt includes at least one of methylamine halide and ethylamine halide; optionally, it is methylammonium chloride. In one alternative embodiment, the solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide.

[0013] Optionally, the mass ratio of N,N-dimethylformamide to dimethyl sulfoxide in the solvent is (3-8):1.

[0014] In one alternative implementation, the mixing includes agitation and stirring.

[0015] Optionally, the mixing time is 2-4 hours.

[0016] In one alternative embodiment, the step of filtering the precursor solution is further included, the filtration comprising using an organic filter cartridge; Optionally, the pore size of the organic filter element is <0.22 μm.

[0017] In one optional embodiment, the annealing temperature is 140-165°C, the time is 8-30 minutes, and the ambient humidity is 30%-50%.

[0018] Secondly, the present invention also provides a perovskite solar cell, comprising a perovskite thin film prepared by the above-described preparation method.

[0019] In one optional embodiment, the perovskite solar cell further includes a conductive substrate, an electron transport layer, a hole transport layer, and a metal electrode layer.

[0020] Optionally, the conductive substrate includes at least one of FTO, ITO, and AZO; Optionally, the electron transport layer includes TiO2, SnO2, ZnO, ZrO2, and WO3. 3、 At least one of Fe2O3 and In2O3; Optionally, the hole transport layer includes Spiro-OMeTAD, NiO x PTAA, P3HT, MoO x At least one of SAM; Optionally, the metal electrode layer includes at least one of Au, Ag, and Cu; Optionally, the conductive substrate is FTO glass, the electron transport layer is TiO2, the surface passivation layer is PEAI, the hole transport layer is Spiro-OMeTAD, and the metal electrode is a gold electrode.

[0021] It should be noted that the perovskite solar cell includes at least one of conventional perovskite solar cells and inverted perovskite solar cells.

[0022] It should be noted that the fabrication method of the formal perovskite solar cell includes the following steps: ① Cleaning the FTO glass substrate: Select FTO transparent conductive glass, and clean it with glass cleaning agent and ultrapure water (more than 3 times) for 18-22 minutes. Then dry it with nitrogen gun and treat it with ultraviolet irradiation for 13-17 minutes before use. ②Preparation of the TiO2 electron transport layer: TiCl4 and ultrapure water were added dropwise to ice water at a volume ratio of TiCl4:H2O = (0.02-0.03):1 to obtain a diluted TiCl4 solution. The diluted TiCl4 solution was then poured into a petri dish to cover the FTO glass. The petri dish was then sealed and placed in an electric heating drying oven at 60-80℃ for 50-75 minutes. After being removed, the petri dish was rinsed with water and then annealed at 180-220℃ for 20-40 minutes to obtain FTO / TiO2 for later use.

[0023] ③ Preparation of perovskite precursor solution: Weigh out PbI2:CH(NH2)2I:CH3NH3Cl in a molar ratio of (0.8-1.2):(0.8-1.2):0.2-0.5, and add 1-10 mg of 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-carbamate hydrochloride (C 14 H 13 ClFN5) was used as an additive, and then dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The mixed solution was stirred for 2-4 hours and filtered with an organic filter to obtain a clear and clean perovskite precursor solution with a concentration of 1.4-1.8M for later use.

[0024] ④ Preparation of the perovskite absorber layer: Transfer 50-100 μl of 1.4-1.8 M perovskite precursor solution and uniformly coat it onto an FTO / TiO2 substrate. The spin-coating process is a single-stage process: 5000-6000 rpm for 30-50 s. At the 7th-12th second after the start of spin-coating, add 0.6-1 ml of anhydrous diethyl ether. Then, anneal the wet film obtained by spin-coating at 140-165℃ for 8-30 min, maintaining an ambient humidity of 20%-55% during annealing.

[0025] ⑤ Fabrication of the Spiro-OMeTAD hole transport layer: Weigh 85-95 mg Spiro-OMeTAD, add 0.8-1.2 ml of chlorobenzene, then add 33-39 μL of tBP solution and 20-24 μL of pre-prepared Li-TFSI solution (acetonitrile solution with a concentration of 500-540 mg / mL), stir at room temperature in the dark for more than 5 hours, and then filter with an organic filter to obtain Spiro-OMeTAD solution; cool the annealed perovskite film to room temperature, spin-coat the Spiro-OMeTAD solution onto the perovskite film at a speed of 3000-5000 rpm for 25-35 s to obtain hole transport layer, and finally store in an environment with humidity below 15-25% in the dark for 5-12 hours.

[0026] ⑥ Au electrode evaporation: The oxidized "FTO / TiO2 / perovskite thin film / Spiro-OMeTAD" was transferred into the evaporation chamber, and Au electrodes were deposited using thermal evaporation at a vacuum level of 9×10⁻⁶. 4 -2×10 5 Pa, with a deposition thickness of 50-120 nm.

[0027] It should be noted that the fabrication method of the inverted perovskite solar cell includes the following steps: Cleaning the glass substrate → Preparing the hole transport layer → Preparing the perovskite absorber layer → Preparing the electron transport layer → Electrode evaporation. The preparation methods for each functional layer are the same as those for the formal perovskite solar cell described above.

[0028] The technical solution of this invention has the following advantages: 1. The present invention provides a method for preparing a perovskite thin film, comprising the following steps: S1, mixing and filtering a perovskite thin film precursor, an additive, and a solvent to obtain a precursor solution; the additive comprises 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-formamidinium hydrochloride (C 14 H 13 ClFN5); S2, after coating the precursor solution onto the substrate, annealing is performed to obtain a perovskite thin film. This invention introduces 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine-3-formamidinium hydrochloride, which has a multifunctional conjugated system, as an additive into the perovskite precursor solution. Utilizing the abundant N atoms and aromatic heterocyclic conjugated system in its molecular structure, it forms multiple hydrogen bonds with the components in the precursor, effectively regulating the crystallization process of the perovskite. This effect optimizes crystal orientation and significantly increases grain size, improving the crystallinity of the thin film; simultaneously, its conjugated structure effectively passivates bulk defects in the thin film, reducing the defect state density. These combined effects optimize the photoelectric performance of the perovskite active layer, ultimately achieving a significant improvement in the device's photoelectric conversion efficiency.

[0029] 2. The perovskite film precursor, additive, and solvent provided by this invention are in the following proportions: (400-1600) mg: (1-10) mg: (0.8-1.2) ml. The molar ratio of lead source, first organic amine salt, and second organic amine salt in the perovskite film precursor is (0.8-1.2):(0.8-1.2):(0.2-0.5). Within this range, the crystallization regulation and defect passivation effects of the second organic amine salt can be effectively utilized under the premise that the first organic amine salt is the main component of the perovskite. At the same time, the additive-assisted crystallization regulation can effectively reduce the problems of uneven perovskite film growth and micro-strain accumulation in the film caused by excessive second organic amine salt, and further promote the nucleation rate and composition uniformity of the film. Attached Figure Description

[0030] 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.

[0031] Figure 1 The current density-voltage curves (JV) of the perovskite thin films prepared in Example 1 and Comparative Example 1 are shown, where the red line represents Example 1 and the black line represents Comparative Example 1.

[0032] Figure 2 The images show grazing incidence wide-angle X-ray diffraction patterns of the perovskite films prepared in Example 1 and Comparative Example 1, with the left image being Comparative Example 1 and the right image being Example 1. Figure 3 The images are scanning electron microscope images of the perovskite thin films prepared in Example 1 and Comparative Example 1. The left image is Comparative Example 1, and the right image is Example 1. Figure 4 The images show the fluorescence emission spectra of the perovskite films prepared in Example 1 and Comparative Example 1, where the red line represents Example 1 and the black line represents Comparative Example 1. Figure 5 The images show time-resolved fluorescence emission patterns of the perovskite thin films prepared in Example 1 and Comparative Example 1, with the red line representing Example 1 and the black line representing Comparative Example 1. Detailed Implementation

[0033] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on 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 scope of protection of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0035] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0037] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0038] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] 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.

[0040] The method for preparing the FTO / TiO2 substrate includes the following steps: TiCl4 and ultrapure water were added dropwise to an ice-water mixture at a volume ratio of 0.0225:1 to obtain a TiCl4 solution for chemical bath deposition. An FTO glass substrate irradiated with ultraviolet light was placed in the TiCl4 solution. The substrate was then reacted at a constant temperature of 70°C in an electric heating drying oven for 60 min. After removal, the substrate was rinsed with water and then annealed at 200°C for 30 min to obtain the FTO / TiO2 substrate.

[0041] Example 1 This embodiment provides a method for preparing perovskite thin films, and the specific steps and parameter settings are as follows: S1, the perovskite thin film precursor (lead iodide, formamidinium hydroiodate, methyl ammonium chloride molar ratio = 1:1:0.35), additive (C) 14 H 13 ClFN5) and solvent (DMF and DMSO in a mass ratio of 4:1) were mixed and filtered to obtain a precursor solution; the ratio of the perovskite film precursor, additive, and solvent was 1050.6 mg: 3 mg: 1 ml. S2, 100 μl of the above perovskite precursor liquid is uniformly coated on an FTO / TiO2 substrate and spin-coated at 5000 rpm for 30 s to prepare a thin film. At the 10th second of spin-coating, 1 mL of anhydrous diethyl ether is added as an antisolvent. Then, after annealing at 160°C for 10 min at an ambient humidity of 30%, the perovskite thin film is obtained.

[0042] Example 2 This embodiment provides a method for preparing perovskite thin films, and the specific steps and parameter settings are as follows: S1, the perovskite thin film precursor (lead iodide, formamidinium hydroiodate, methyl ammonium chloride molar ratio = 1:1:0.25), additive (C) 14 H 13 ClFN5) and solvent (DMF and DMSO in a mass ratio of 4:1) were mixed and filtered to obtain a precursor solution; the ratio of the perovskite film precursor, additive, and solvent was 1039.8 mg: 3 mg: 1 ml. S2, 100 μl of the above perovskite precursor liquid is uniformly coated on an FTO / TiO2 substrate and spin-coated at 5000 rpm for 30 s to prepare a thin film. At the 10th second of spin-coating, 1 mL of anhydrous diethyl ether is added as an antisolvent. Then, after annealing at 160°C for 10 min at an ambient humidity of 30%, the perovskite thin film is obtained.

[0043] Example 3 This embodiment provides a method for preparing perovskite thin films, and the specific steps and parameter settings are as follows: S1, the perovskite thin film precursor (lead iodide, formamidinium hydroiodate, methyl ammonium chloride molar ratio = 1:1:0.2), additive (C) 14 H 13 ClFN5) and solvent (DMF and DMSO in a mass ratio of 8:1) were mixed and filtered to obtain a precursor solution; the ratio of the perovskite film precursor, additive, and solvent was 1163.7 mg: 10 mg: 1 ml. S2, 50 μl of the above perovskite precursor liquid is uniformly coated on an FTO / TiO2 substrate and a thin film is prepared by spin coating at 6000 rpm for 30 s. At the 12th second after the start of spin coating, 0.6 mL of anhydrous diethyl ether antisolvent is added dropwise. Then, after annealing at 140°C for 30 min at an ambient humidity of 50%, the perovskite thin film is obtained.

[0044] Example 4 This embodiment provides a method for preparing perovskite thin films, and the specific steps and parameter settings are as follows: S1, the perovskite thin film precursor (lead iodide, formamidinium hydroiodate, methyl ammonium chloride molar ratio = 1:1:0.5), additive (C) 14 H 13 The perovskite film precursor, additive, and solvent (DMF and DMSO in a mass ratio of 3:1) were mixed and filtered to obtain a precursor solution; the ratio of the perovskite film precursor, additive, and solvent was 933.45 mg: 1 mg: 1 ml. S2, 100 μl of the above perovskite precursor liquid is uniformly coated on an FTO / TiO2 substrate and a thin film is prepared by spin coating at 5000 rpm for 50 s. At the same time, 1 mL of anhydrous diethyl ether antisolvent is added at the beginning of spin coating. Then, after annealing at 165°C for 8 min at an ambient humidity of 30%, the perovskite thin film is obtained.

[0045] Comparative Example 1 This comparative example provides a method for preparing a perovskite thin film, which differs from Example 1 only in that: S1, the perovskite thin film precursor (molar ratio of lead iodide, formamidinium hydroiodate, and methylammonium chloride = 1:1:0.35) and solvent (mass ratio of DMF and DMSO = 4:1) are mixed and filtered to obtain a precursor solution; the ratio of the perovskite thin film precursor to the solvent is 1053.6 mg: 1 ml; The remaining steps are the same as in Example 1.

[0046] Comparative Example 2 This comparative example provides a method for preparing a perovskite thin film, which differs from Example 1 only in that: S1, the perovskite thin film precursor (molar ratio of lead iodide, formamidinium hydroiodate, and methyl ammonium chloride = 1:1:0.35), 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine-3-carboxynitrile, and solvent (mass ratio of DMF and DMSO = 4:1) are mixed and filtered to obtain a precursor solution; the ratio of the perovskite thin film precursor, additive, and solvent is 1050.6 mg: 3 mg: 1 ml; The remaining steps are the same as in Example 1.

[0047] Experimental Example 1 The perovskite thin films prepared in each embodiment and comparative example were used to fabricate perovskite solar cells. The specific fabrication methods are as follows: (1) After filtering the 5 mg / mL PEAI-isopropanol solution through a 0.22 µm organic filter, take 70 µL and spin-coat it dynamically at 3000 rpm for 30 s on the perovskite films prepared in each example and comparative example to obtain intermediate-1 containing a surface passivation layer (PEAI). (2) Weigh 90 mg Spiro-OMeTAD and dissolve it in 1 ml of chlorobenzene. Then add 22 μL of 520 mg / mL acetonitrile solution and 36 μL of 4-tert-butylpyridine (t-BP) solution. Stir for 5 h in the dark and filter with an organic filter with a pore size of 0.22 μm. Spin-coat the Spiro-OMeTAD solution onto the surface of intermediate-1 at 5000 rpm for 30 s to prepare a hole transport layer. Finally, store it in the dark at a humidity of less than 20% for 12 h to obtain intermediate-2 with a hole transport layer on the surface. (3) The intermediate-2 was transferred into the evaporation chamber, and a 120 nm thick Au electrode was deposited using thermal evaporation. The effective area of ​​the cell on the mask was 0.09 cm². 2 The device was then stored in a dark environment with humidity below 20% for 2 days to obtain the perovskite solar cell.

[0048] The photoelectric conversion efficiency of the prepared perovskite solar cells was tested.

[0049] The photoelectric conversion efficiency test included testing at room temperature using a Keithley 2450 source meter and a solar simulator from Guangyan Technology, at a light intensity of 100 mW / cm². 2 Perovskite solar cells prepared from perovskite thin films obtained in each embodiment and comparative example were tested under (AM 1.5G) conditions.

[0050] The specific test results are shown in Table 1 below: Table 1. Photoelectric conversion efficiency test data

[0051] As shown in Table 1, the examples are significantly better than the comparative examples. The photoelectric conversion efficiency of Examples 1-4 is between 23.77% and 25.07%, while that of Comparative Examples 1-2 is 22.35% and 22.46%, respectively. The photoelectric conversion efficiency of the examples is improved by more than 2%. Overall, compared with the comparative examples, the examples show a significant improvement in open-circuit voltage and fill factor, indicating that C 14 H 13 ClFN5, as an additive, exhibits a significant passivation effect on bulk defects and also greatly improves short-circuit current, indicating that the additive can effectively promote charge extraction and transport.

[0052] Figure 1 Current density-voltage curves of perovskite solar cells prepared from the perovskite thin films of Example 1 and Comparative Example 1 ( JV Compared to Comparative Example 1, Example 1 has a higher open-circuit voltage (). V OC ), fill factor (FF) and short-circuit current density ( J SC Finally, the device parameters for Example 1 are as follows: V OC 1.168V J SC 26.13 mA / cm 2 FF: 82.15, PCE: 25.07%, while the parameters of the comparative example 1 device are only: V OC 1.119V J SC 25.45 mA / cm 2 , FF: 78.85, PCE: 22.46%.

[0053] Figure 2 The images show the grazing incidence wide-angle X-ray diffraction (GIWAXS) patterns of the perovskite films prepared in Example 1 and Comparative Example 1. In Comparative Example 1, α-FAPbI3 is predominantly diffracted in the z-direction, accompanied by diffraction signals from δ-FAPbI3 and PbI2; while in Example 1, α-FAPbI3 is predominantly diffracted in the 30° direction, and the diffraction signals from δ-FAPbI3 and PbI2 disappear. This indicates that the introduction of C... 14 H 13 After ClFN5 was applied, the crystal orientation of the film changed, and δ-FAPbI3 and uncoordinated lead ions were effectively suppressed and passivated, thus improving the crystal quality of the film.

[0054] Figure 3The images show scanning electron microscope (SEM) images of the perovskite films prepared in Example 1 and Comparative Example 1. The SEM images show a significant increase in grain size and a smoother, denser grain surface in Example 1. This may be due to the addition of additive C. 14 H 13 The effect of ClFN5 on the crystallization orientation and defect passivation of the thin film during the thin film formation process is the result.

[0055] Figure 4 The fluorescence emission spectra (PL) of the perovskite films prepared in Example 1 and Comparative Example 1 are shown. No significant shift in the fluorescence emission peaks of Example 1 and Comparative Example 1 was observed. However, the PL peak intensity of Example 1 was significantly improved, indicating that the introduction of C... 14 H 13 ClFN5 reduced nonradiative recombination in the thin film.

[0056] Figure 5 The images show time-resolved fluorescence emission (TRPL) patterns of the perovskite films prepared in Example 1 and Comparative Example 1. Compared to Comparative Example 1, the carrier lifetime of Example 1 is significantly improved, indicating that C... 14 H 13 The introduction of ClFN5 can effectively suppress nonradiative recombination, reduce defect recombination, improve carrier diffusion lifetime, and ultimately improve the photovoltaic performance of perovskite devices.

[0057] 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, Includes the following steps: S1, mix the perovskite precursor, additives and solvent to obtain a precursor solution; The additives include 1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-formamidinium hydrochloride; S2, the precursor solution is coated onto the substrate and annealed to obtain a perovskite thin film.

2. The preparation method according to claim 1, characterized in that, The ratio of the perovskite precursor, additives, and solvent is (400-1600) mg: (1-10) mg: (0.8-1.2) ml.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of lead source, first organic amine salt, and second organic amine salt in the perovskite precursor is (0.8-1.2):(0.8-1.2):(0.2-0.5).

4. The preparation method according to any one of claims 1-3, characterized in that, The solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide.

5. The preparation method according to claim 3, characterized in that, The first organic amine salt includes at least one of formamidine halide and acetamidine halide.

6. The preparation method according to claim 3, characterized in that, The second organic amine salt includes at least one of methylamine halide and ethylamine halide.

7. The preparation method according to any one of claims 1-6, characterized in that, The coating thickness is 100-500 nm.

8. The preparation method according to any one of claims 1-7, characterized in that, The coating includes spin coating; Optionally, the spin coating rotation speed is 5000-6000 rpm and the time is 30-50s; Optionally, the spin coating includes adding an antisolvent dropwise 7-12 seconds after the start of spin coating; Further optionally, the volume ratio of the antisolvent to the perovskite precursor solution is (0.6-1):(0.05-0.1). Further, optionally, the antisolvent includes anhydrous diethyl ether.

9. The preparation method according to any one of claims 1-8, characterized in that, The annealing temperature is 140-165℃, the time is 8-30 minutes, and the ambient humidity is 30%-50%.

10. A perovskite solar cell, characterized in that, This includes perovskite thin films prepared by the preparation method according to any one of claims 1-9.

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