A method for preparing a tin-based perovskite thin film

Abstract

This application discloses a method for preparing a tin-based perovskite thin film, belonging to the field of photovoltaic materials technology. The preparation method includes the following steps: providing a tin-based perovskite precursor solution, wherein a halogen-like additive is added to the precursor solution; coating the precursor solution into a film, and annealing the film to obtain a tin-based perovskite thin film; wherein the cation of the halogen-like additive is EDA. 2+ Gua + At least one of them, wherein the anion is BF4 — PF6 — At least one of the following. By doping tin-based perovskite thin films with specific halogen-like additives in a specific manner, the crystallization of tin-based perovskite thin films can be controlled, defects in perovskite thin films can be reduced, and the photoelectric conversion efficiency and stability of devices can be improved.

Description

Technical Field

[0001] This application belongs to the field of perovskite material technology, specifically relating to a method for preparing tin-based perovskite thin films. Background Technology

[0002] Metal halide perovskite materials have shown great application potential in the field of optoelectronic devices due to their unique crystal structure and excellent photoelectric properties. Among them, tin-based perovskites have the general chemical formula ASnX3, with the A-site typically occupied by a cesium ion (Cs). + ), Methylamine ion (MA + ) or formamidinium ion (FA + The X-position is a halide ion (Cl). — ,Br — I — As a direct bandgap semiconductor material, tin-based perovskite has advantages such as high carrier mobility and tunable bandgap. In particular, its environmental friendliness makes it an ideal candidate material to replace lead-containing perovskite, and it has attracted much attention in the fields of solar cells and light-emitting diodes.

[0003] However, the development of tin-based perovskites still faces severe technical challenges. Due to the lack of lanthanide contraction effect in tin atoms, tin iodide (SnI₂) exhibits stronger Lewis acidity than its lead-based analogues, while the ionization energy of the tin-iodine (Sn-I) bond is relatively low. These intrinsic properties make it extremely difficult to control the crystallization kinetics of tin-based perovskites during solution film formation. Specifically, this manifests as excessively rapid crystallization rates, leading to low film surface coverage, rough morphology, and the introduction of numerous structural defects. Furthermore, the Sn content in the precursor solution and the film... 2+ It is easily oxidized to Sn 4+ This leads to self-doping and severe tin vacancy defects in the thin film, which further exacerbates nonradiative recombination. These factors collectively result in tin-based perovskite optoelectronic devices exhibiting efficiency far below their theoretical values ​​and poor stability, severely hindering their commercialization. To address these issues, existing technologies have attempted corresponding improvements. For example, Chinese patent application CN119604162A proposes a method for film formation assisted by interfacial protonation reactions. This method introduces ethylenediamine derivatives into the perovskite precursor to form a complex mesophase, and then uses an acidic substrate to undergo a protonation reaction with it during annealing, thereby inducing the transformation of the mesophase into the perovskite thin film. This aims to control the crystallization rate and improve the film quality.

[0004] However, existing technologies still have room for improvement. First, their crystallization control strategy primarily relies on the protonation reaction occurring at the substrate interface. This process is highly dependent on the type and density of acidic functional groups on the substrate, resulting in a narrow process window and making it difficult to universally apply to different hole transport layers or substrate materials. Second, although this method delays crystallization by forming an intermediate phase, the growth and densification processes of grains still lack effective control in the later stages of film conversion, and the thickness uniformity and nanoscale morphological defects of the prepared films require further optimization. More importantly, existing technologies for Sn... 2+ The oxidation inhibition effect is limited, mainly by introducing stannous fluoride (SnF2) as a sacrificial agent. However, its antioxidant capacity is insufficient under long-term working conditions, and its uneven distribution may lead to differences in local properties of the film.

[0005] Therefore, how to develop a more effective strategy for preparing tin-based perovskite thin films by synergistically addressing both crystallization kinetics regulation and chemical stability enhancement, in order to obtain films with higher crystal quality, lower defect density, and stronger oxidation resistance, thereby further improving the photoelectric conversion efficiency and operational stability of devices, remains a key issue that urgently needs to be addressed in this field.

[0006] Application content In view of this, the primary objective of this application is to provide a method for preparing a tin-based perovskite thin film, which involves doping the tin-based perovskite thin film with specific halogen-like additives in a specific manner to regulate the crystallization of the tin-based perovskite, reduce defects in the perovskite thin film, and obtain a tin-based perovskite thin film with high crystal quality, low defect density, and strong oxidation resistance, thereby improving the photoelectric conversion efficiency and stability of the device.

[0007] To achieve the above objectives, this application adopts the following technical solution: One aspect of this application discloses a method for preparing a tin-based perovskite thin film, comprising the following steps: A tin-based perovskite precursor solution is provided, wherein a halogen-like additive is added to the precursor solution; The precursor solution was coated into a film, and after annealing, a tin-based perovskite thin film was obtained. The cation of the halogen-like additive is EDA. 2+ Gua + At least one of them, wherein the anion is BF4 — PF6 — At least one of them.

[0008] Another aspect of this application discloses a tin-based perovskite thin film prepared using the preparation method described in this application.

[0009] Another aspect of this application discloses a tin-based perovskite solar cell, including a perovskite absorber layer, which is prepared using the preparation method described in this application.

[0010] This application has at least the following beneficial effects: This application introduces halogen-like additives into a tin-based perovskite precursor solution through a specific method, thereby significantly improving the thin film quality, enhancing its oxidation resistance, and improving the photoelectric conversion efficiency and stability of solar cell devices. Specifically, the anions in the halogen-like additives can partially replace the halide ions in the tin-based perovskite, inhibiting halide ion migration, reducing halogen site defects, and thus regulating the crystallization process of the tin-based perovskite thin film. Simultaneously, the cations in the additives can passivate tin and halogen defects, regulating the perovskite energy levels. The combination of these two elements results in a tin-based perovskite thin film with fewer defects and higher quality, leading to more efficient and stable tin-based perovskite solar cell devices. Attached Figure Description

[0011] Figure 1 These are comparative images of the surface morphology of tin-based perovskite films prepared in Example 1 (experimental sample) and Comparative Example 1 (control sample) of this application.

[0012] Figure 2 The image shows the crystallinity intensity of the tin-based perovskite thin films prepared in Example 1 (experimental sample) and Comparative Example 1 (control sample) of this application.

[0013] Figure 3 This is a structural diagram of a tin-based perovskite solar cell prepared according to an embodiment of this application.

[0014] Figure 4 The graph shows the photoelectric conversion efficiency of the tin-based perovskite solar cells prepared in Example 1 (experimental sample) and Comparative Example 1 (control sample) of this application.

[0015] Figure 5 Transient photovoltage diagrams of tin-based perovskite solar cells prepared in Example 1 (experimental sample) and Comparative Example 1 (control sample) of this application.

[0016] Figure 6 Transient photocurrent diagrams of tin-based perovskite solar cells prepared in Example 1 (experimental sample) and Comparative Example 1 (control sample) of this application. Detailed Implementation

[0017] The embodiments of this application will be clearly and completely described below. The technical solutions in the embodiments described below are exemplary and only possible technical implementations of this application, not all possible implementations. Those skilled in the art can combine the embodiments of this application to obtain other embodiments without creative effort, and these embodiments are also within the protection scope of this application.

[0018] The first aspect of this application discloses a method for preparing a tin-based perovskite thin film, comprising the following steps: A tin-based perovskite precursor solution is provided, wherein a halogen-like additive is added to the precursor solution; The precursor solution was coated into a film, and after annealing, a tin-based perovskite thin film was obtained. The cation of the halogen-like additive is EDA. 2+ Gua + At least one of them, wherein the anion is BF4 — PF6 — At least one of them.

[0019] In this application, specific halogen-like additives are incorporated into the perovskite precursor solution to prepare perovskite thin films. This not only regulates the crystallization process of the perovskite film but also effectively enables both cations and anions to be successfully incorporated into the perovskite lattice, with effects not limited to the upper and lower interfaces of the perovskite. This preparation method not only achieves passivation of the overall lattice structure but also inhibits the migration of internal halide ions. The effective area, effect, and function of the halogen-like additives are maximized under this preparation method.

[0020] In this application, "tin-based perovskite" refers to a chemical structure in which the B-site cation is primarily divalent tin ions (Sn). 2+ Cesium ions are a type of perovskite material. Their crystal structure is typically three-dimensional ABX3, where the A-site is a monovalent cation, usually a cesium ion (Cs). + ), Methylamine ion (MA + ) or formamidinium ion (FA + At least one of the following: B site is a divalent metal cation Sn 2+ The X-position is a halide anion, such as Cl. — ,Br — I — At least one of the following. In this application, specific examples of the tin-based perovskite include, but are not limited to, at least one of formamidine stannous iodide (FASnI3), methylamine stannous iodide (MASnI3), and cesium stannous iodide (CsSnI3), and may also be a mixture of the above materials at the A-site or in a mixture of halogen forms, such as (FASnI3). x (MASnI3) 1-x or FASnI 3-x Br x wait.

[0021] In this application, the "precursor solution" of the tin-based perovskite refers to a raw material solution used to prepare tin-based perovskite films by solution processing techniques (such as coating). This precursor solution contains a mixture of various components required to form the tin-based perovskite and is dissolved in a suitable organic solvent. Its main components include: providing Sn 2+ The source of the tin salt (usually tin halides, such as tin iodide SnI2), the salt providing the A-site cation (such as formamidine iodide FAI, methylamine iodide MAI, cesium iodide CsI, etc.), and various functional additives for regulating crystallization or improving film quality, such as SnF2. Halogen-like additives are specifically added in this application.

[0022] The solvent in the precursor solution can be any solvent well known in the art, without particular limitation. Specific examples include at least one of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), or a mixed solvent formed by mixing them in any proportion. In some specific examples, the solvent used is a mixed solvent of DMF and DMSO in a volume ratio of 4:1.

[0023] In some specific examples, the concentration of SnI2 in the precursor solution ranges from 0.1M to 2.0M, for example, it can be any concentration or a range between any two concentrations from 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, 0.7M, 0.8M, 0.9M, 1.0M, 1.1M, 1.2M, 1.3M, 1.4M, 1.5M, 1.6M, 1.7M, 1.8M, 1.9M, or 2M. The ratio of raw materials can be configured according to the desired target product. The film thickness can be controlled by adjusting the concentration in the precursor solution. It should be noted that the preparation process of the precursor solution is usually carried out at a suitable temperature and in a non-reactive atmosphere (such as nitrogen or a rare gas) to prevent Sn from spreading. 2+ After oxidation, the solution must be filtered to remove undissolved particles. In some specific examples, the preparation temperature of the precursor solution is 15-70°C, for example, any temperature or a range between any two of the following: 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, and 70°C. The specific temperature can be adjusted appropriately according to the selection of raw materials, and those skilled in the art are capable of doing so.

[0024] In this application, the term "halogen-like additive" refers to a class of functional substances that are chemically similar to halogens and can coordinate with metal ions or participate in the perovskite crystallization process, thereby regulating the morphology and defect states of thin films. Specifically, in this application, it refers to substances with EDA as the cation. 2+ Gua + At least one of them, wherein the anion is BF4— PF6 — At least one of the following halogenated additives. Specific examples are at least one of EDA(BF4)2, GuaBF4, and EDA(PF6)2, but are not limited thereto.

[0025] The anions in this type of halogen additive can replace some halogens, inhibit the migration of halide ions, and reduce halogen site defects. At the same time, the cations can passivate tin defects and halogen defects, and regulate the energy levels of perovskites. The combination of the two improves the overall quality of tin-based perovskites.

[0026] In this application, the amount of halogen-like additive can be appropriately adjusted according to the experimental purpose and research needs. Relative to the molar amount of stannous iodide in the precursor solution, the amount of halogen-like additive is preferably 0.01%-5%, for example, any value or range between any two values ​​from 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. Preferably, the amount added is 1%-2%, more preferably 1.5%. If the amount added is too small, crystallization cannot be effectively controlled; if the amount added is too large (if it exceeds 5%), the crystallization rate will be significantly increased, resulting in an uneven and less dense perovskite film, leading to a significant increase in the film roughness.

[0027] In this application, "coating" refers to a process method in which a tin-based perovskite precursor solution is applied to the surface of a substrate to form a uniform wet film. The purpose is to spread the precursor solution on the substrate, preparing it for subsequent solvent evaporation and thin film crystallization. In this application, the coating method includes, but is not limited to, any one of spin coating, blade coating, and spray coating. Those skilled in the art can select a suitable coating method based on the substrate size, required film thickness, and production efficiency requirements, without any particular limitation.

[0028] In some specific examples, the coating is performed by spin coating, and the specific coating parameters can be adjusted or optimized according to specific experimental requirements. In some specific examples, the spin coating speed is 5000 rpm and the time is 50 s. More preferably, 500-600 μL of chlorobenzene is added dropwise at the 14th-20th s of the coating time to extract the precursor solution and accelerate the nucleation process.

[0029] After coating, an annealing step is also included. Annealing refers to the heat treatment of the wet film formed after coating at a certain temperature, a key process step that promotes solvent evaporation, induces the reaction of precursor components, and crystallizes to form a perovskite thin film. This process directly affects the crystallinity, grain size, and final quality of the perovskite film.

[0030] In this application, the annealing conditions include annealing temperature and annealing time, wherein the annealing temperature is 70-100℃ and the annealing time is 10-20 min. Specific annealing parameters can be adjusted or selected according to specific experimental purposes or research needs. For example, regarding the annealing temperature, in some specific examples, any temperature or a range between any two temperatures can be selected from 70℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, 98℃, or 100℃. Regarding the annealing time, in some specific examples, any time or a range between any two times can be selected from 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min. It should be noted that temperature and time can be combined in any way, and the specific combination should be adjusted according to the experimental needs. For example, the combination of annealing temperature and time can be 70℃ / 10min, 70℃ / 15min, 70℃ / 20min, 80℃ / 10min, 80℃ / 15min, 80℃ / 20min, 90℃ / 10min, or 100℃ / 10min, but it is not limited to these combinations.

[0031] Appropriate annealing temperature and time are beneficial for obtaining dense perovskite films with high crystallinity and few defects. Furthermore, it should be noted that annealing is typically performed under a non-reactive atmosphere to prevent Sn from forming. 2+ Oxidation at high temperatures.

[0032] The second aspect of this application discloses a tin-based perovskite thin film. The thickness of the tin-based perovskite thin film prepared by this application can be 30-500 nm, for example, any thickness or a range between any two thicknesses selected from 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm. It is understood that the thickness can be controlled by adjusting the concentration of the precursor solution and the coating conditions, etc. A suitable film thickness results in better performance release, and those skilled in the art can choose according to their needs; therefore, there are no particular limitations.

[0033] A third aspect of this application discloses a tin-based perovskite solar cell, which includes a perovskite absorber layer prepared by the preparation method described in this application.

[0034] The "perovskite solar cell" described in this application is a photovoltaic device that directly converts light energy into electrical energy. Its core component is a perovskite material as the light-absorbing layer, specifically referring to the prepared tin-based perovskite thin film. In some specific examples of this application, a typical perovskite solar cell sequentially comprises a substrate layer, a hole transport layer, a perovskite absorber layer, a carrier transport layer, a buffer layer, and a top electrode.

[0035] The substrate layer serves to provide mechanical support and a conductive base for the entire device. It typically includes a transparent substrate and a transparent conductive oxide electrode deposited thereon. The transparent substrate needs to have good light transmittance and chemical stability, while the transparent conductive oxide needs to have high conductivity and high light transmittance. In this application, the substrate layer can adopt compositions well-known in the art. The transparent substrate can be a flexible polymer material such as glass, polyethylene terephthalate (PET), or polyethylene naphthalate (PEN), and the transparent conductive oxide can be indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or aluminum-doped zinc oxide (AZO), but is not limited to these. In some specific examples, ITO glass or FTO glass is preferred.

[0036] The substrate needs to be cleaned and surface treated (such as ultraviolet ozone treatment or plasma treatment) before use to improve surface wettability and work function, which will not be elaborated here.

[0037] The hole transport layer, located between the substrate (typically the anode) and the perovskite absorber layer, efficiently extracts and transports photogenerated holes while blocking the back transport of electrons, reducing interfacial recombination. The hole transport layer material must possess an energy level structure matching the perovskite absorber layer, high hole mobility, and good film-forming properties. It can be an inorganic or organic hole transport material. For inorganic hole transport materials, nickel oxide (NiO) can be an example. x ), molybdenum oxide (MoO) x Cuprous thiocyanate (CuSCN) is used, but not limited to; organic hole transport materials include, for example, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), but not limited to. In some specific examples in this application, PEDOT:PSS is preferred.

[0038] Hole transport layers are typically prepared on a substrate by methods such as spin coating, blade coating, or atomic layer deposition, followed by appropriate annealing treatment, which will not be elaborated here.

[0039] In this application, the perovskite absorber layer is the thin film layer formed by the tin-based perovskite precursor solution through the "coating" and "annealing" steps mentioned above. It is the core functional layer for the device to realize light absorption and photogenerated carrier generation.

[0040] The carrier transport layer is located between the perovskite absorber layer and the top electrode. Its function corresponds to that of the hole transport layer, primarily for efficiently extracting and transporting photogenerated electrons (often called the electron transport layer in upright structures) and blocking holes. This layer material must possess the lowest unoccupied molecular orbital (LUMO) energy level matching the perovskite absorber layer, high electron mobility, and good chemical stability. It includes both inorganic and organic electron transport materials. For inorganic electron transport materials, examples include at least one of titanium dioxide (TiO2), zinc oxide (ZnO), and tin dioxide (SnO2), without particular limitation; for organic electron transport materials, examples include methyl [6,6]-phenyl-C61-butyrate (PCBM), fullerene (C... 60 Copper bath (BCP). In some specific examples, fullerene (C) with a thickness of 18-22 nm is preferred. 60 The preparation of the charge carrier transport layer can refer to existing technologies such as spin coating, thermal evaporation, or atomic layer deposition, and therefore there are no particular limitations.

[0041] The buffer layer is typically located between the carrier transport layer and the metal top electrode. It protects the underlying structure from damage during electrode deposition, improves the interfacial contact between the electrode and the carrier transport layer, and prevents exciton quenching. The buffer layer material is usually an insulating material or a low work function material with a wide bandgap and appropriate energy levels. Specific examples include, but are not limited to, LiF, BCP, and MoO3. In some specific examples, BCP with a thickness of 5-8 nm is preferred. Its preparation method is typically thermal evaporation deposition, with the thickness controlled on the order of a few nanometers.

[0042] The top electrode, serving as another charge collection point for the device, is typically a metal electrode. The top electrode material must possess high conductivity and be able to form good ohmic contact with adjacent functional layers. Depending on the device structure (positive or negative), the type of charge collected by the top electrode (electrons or holes) varies. Specific examples of top electrode materials include, but are not limited to, gold (Au), silver (Ag), copper (Cu), aluminum (Al), or alloys thereof. In some specific examples, Ag with a thickness of 80-120 nm is preferred. Its fabrication methods are typically vacuum thermal evaporation deposition or magnetron sputtering, which will not be elaborated upon here.

[0043] The materials and fabrication methods described above are merely illustrative. Those skilled in the art can reasonably adjust and optimize the material selection, thickness, and fabrication process of each functional layer according to specific device designs (such as upright structures, inverted structures, mesoporous structures, etc.) and performance objectives. All such adjustments and optimizations should be understood to fall within the scope of protection of this application.

[0044] Thanks to the advantages of the tin-based perovskite thin film prepared in this application, the perovskite solar cell devices prepared based on it have excellent photoelectric conversion efficiency and stability.

[0045] The present application will be further illustrated below with reference to specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present application in any way.

[0046] 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 in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0047] In addition, unless otherwise specified, methods without detailed conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0048] Example 1: Preparation of tin-based perovskite thin films A 0.9 M FASnI3 tin-based perovskite precursor solution was prepared, with a solute ratio of FAI:SnI2:SnF2 = 1:1:0.1 and 1.5% EDA(BF4)2 added. The solvent was a mixture of DMF and DMSO in a volume ratio of 4:1. The solution was stirred at room temperature (22 °C) for 4 h and filtered through a 0.22 μm PTFE filter for later use. The resulting solution was spin-coated onto an ITO glass substrate at a spin speed of 5000 r / min for 50 s. At the 16th s of spin-coating, 600 μL of CB (chlorobenzene) was added dropwise. After spin-coating, the substrate was transferred to a hot plate and annealed at 80 °C for 20 min to obtain a tin-based perovskite film.

[0049] Example 2: Preparation of tin-based perovskite thin films The same implementation method as in Example 1 was used, except that 1.5% GuaBF4 was added. All other process steps and parameter conditions were the same as in Example 1.

[0050] Example 3: Preparation of tin-based perovskite thin films The same implementation method as in Example 1 was used, except that 1.5% EDA(PF6)2 was added. All other process steps and parameters were the same as in Example 1.

[0051] Example 4: Preparation of tin-based perovskite thin films The same implementation method as in Example 1 was used, except that 1% EDA(BF4)2 was added. All other process steps and parameter conditions were the same as in Example 1.

[0052] Example 5: Preparation of tin-based perovskite thin films The same implementation method as in Example 1 was used, except that 2% EDA(BF4)2 was added. All other process steps and parameter conditions were the same as in Example 1.

[0053] Comparative Example 1 This comparative example was conducted in the same manner as Example 1, except that no additives were added. All other process steps and parameters were the same as in Example 1.

[0054] Comparative Example 2 This comparative example was conducted in accordance with Example 1, except that EDA(BF4)2 was replaced with an equimolar amount of NH4PF6. All other process steps and condition parameters were the same as in Example 1.

[0055] Comparative Example 3 This comparative example was conducted in accordance with Example 1, except that EDA(BF4)2 was replaced with an equimolar amount of PEABr. All other process steps and condition parameters were the same as in Example 1.

[0056] Device performance testing 1. Devices (structure such as...) Figure 3 Preparation (as shown) S1: Substrate cleaning. The ITO transparent glass substrate was ultrasonically cleaned for 15 minutes each with glass cleaner, deionized water, acetone, and isopropanol, respectively. After drying in an oven, it was cleaned with a UV ozone generator for 15 minutes.

[0057] S2: Preparation of the first carrier transport layer, PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)). PEDOT:PSS was spin-coated onto an ITO transparent glass substrate at 5000 r / min in air for 40 s, followed by annealing at 150 °C for 15 min. After cooling, the PEDOT:PSS-coated substrate was transferred into a glove box under a nitrogen atmosphere.

[0058] S3: Preparation of perovskite absorber layers. Tin-based perovskite thin films were prepared according to the methods described in the examples and comparative examples.

[0059] S4: Fabrication of the second carrier transport layer C 60 And a buffer layer. A 20nm thick C layer was formed using a thermal evaporation process. 60And 6nm thick BCP (Bath Copper Essence).

[0060] S5: Fabrication of the top electrode. A 100 nm thick silver layer was formed using a thermal evaporation process.

[0061] 2. Characterization of perovskite thin films Figure 1 The SEM characterization results of the tin-based perovskite films in Example 1 (experimental sample) and Comparative Example 1 (control sample) are shown. It can be seen that, compared with the larger grains in the control sample, the experimental sample has smaller grains due to the induction effect of EDA cations. However, it can be clearly seen that the gaps between the grains in the experimental sample are smaller, indicating that halide-like anions can effectively passivate the grain boundaries between grains, reduce deep-level defects, and obtain better tin-based perovskite films.

[0062] Figure 2 The crystallization intensity spectra of the experimental and control samples are shown. It can be seen that the experimental sample film exhibits a better (100) main peak crystallization intensity, which not only shows a better and stronger orientation bias, but also indicates a higher degree of crystallinity, demonstrating the significant role of halogen-like additives in improving the quality of perovskite crystals.

[0063] 2. Device performance testing Table 1 Device performance test results

[0064] As can be seen from Table 1, the tin-based perovskite solar cell prepared based on the tin-based perovskite thin film of this application is significantly better than the comparative example in terms of parameters such as photoelectric conversion efficiency, open-circuit voltage, short-circuit current and fill factor. This is mainly due to the introduction of halogen-like additives through a specific process in this application.

[0065] Furthermore, Figure 4 The photoelectric conversion efficiency (PCE) graphs of tin-based perovskite solar cells prepared based on the tin-based perovskite thin films in Example 1 (experimental sample) and Comparative Example 1 (control sample) are shown. In this test, a Keithley 2400 digital source meter was used to scan the photocurrent density-voltage curves of the obtained samples. Figure 4 As shown, the experimental sample achieved a photoelectric conversion efficiency of 10.223% and a short-circuit current of 25.28 mA / cm². 2 The open-circuit voltage was 0.554V, and the fill factor was 73%; in contrast, the photoelectric conversion efficiency of the control sample was only 7.306%, and the short-circuit current was 24.87mA / cm. 2 The open-circuit voltage was 0.459V, and the fill factor was 64%. The significant differences in these parameters fully demonstrate the improvement in photoelectric performance of tin-based perovskite solar cells brought about by the addition of halogen-like additives.

[0066] Figure 5 Transient photovoltage diagrams of tin-based perovskite solar cells fabricated based on the tin-based perovskite thin films in Example 1 and Comparative Example 1 are shown. Figure 5 As shown, after treatment with halogen-like additives, the transient photovoltage of the experimental sample decreased more slowly, and the fitted decrease time was longer, indicating that there were fewer non-radiative recombination defects inside the experimental sample, which would be more conducive to carrier separation.

[0067] Figure 6 Transient photocurrent diagrams of tin-based perovskite solar cells fabricated based on the tin-based perovskite thin films of Example 1 and Comparative Example 1 are shown. Figure 6 As shown, after treatment with halogen-like additives, the transient photocurrent of the experimental sample decreased faster and the fitted decrease time was shorter, indicating that the experimental sample had better connectivity and fewer defects at the tin-based perovskite interface, which will be more conducive to carrier extraction.

[0068] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a tin-based perovskite thin film, characterized in that, Includes the following steps: A tin-based perovskite precursor solution is provided, wherein a halogen-like additive is added to the precursor solution; The precursor solution was coated into a film, and after annealing, a tin-based perovskite thin film was obtained. The halogen-like additive is at least one of EDA(BF4)2 and EDA(PF6)2.

2. The preparation method according to claim 1, characterized in that, The amount of the halogen-like additive added is 0.01%-5% of the molar amount of stannous halide in the precursor solution.

3. The preparation method according to claim 1, characterized in that, The coating method is one of spin coating, scraping coating, or spray coating.

4. The preparation method according to claim 1, characterized in that, The coating time is 50 seconds, and 500-600 μL of chlorobenzene is added dropwise between the 14th and 20th seconds of the coating time.

5. The preparation method according to claim 1, characterized in that, The annealing process is performed at a temperature of 70-100℃ for 10-20 minutes.

6. A tin-based perovskite thin film, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The tin-based perovskite thin film as described in claim 6, characterized in that, The thickness of the tin-based perovskite film is 30-500 nm.

8. A tin-based perovskite solar cell, characterized in that, It includes a perovskite absorber layer, which is prepared by the preparation method according to any one of claims 1-5.

9. The tin-based perovskite solar cell as described in claim 8, characterized in that, The tin-based perovskite solar cell comprises, in sequence, a substrate layer, a hole transport layer, a perovskite absorber layer, a carrier transport layer, a buffer layer, and a top electrode.

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