Preparation method of tin oxide thin film and solar cell

Abstract

The invention discloses a preparation method of a tin oxide thin film and a solar cell, and the method comprises the steps: depositing a tin oxide precursor solution on a substrate, and carrying out the annealing treatment to form the tin oxide thin film in situ. The method optimizes the nucleation and crystallization behaviors of the tin oxide film on the substrate, ensures the uniformity and compactness of the film, improves the interface quality, and improves the electron transmission performance of the film by adjusting the surface properties of the film, enhancing the energy level matching, reducing the electron recombination phenomenon and improving the electron extraction efficiency. And moreover, the production cost and the environmental influence are reduced, and the large-scale application of the process is ensured.

Description

Technical Field

[0001] This application belongs to the field of materials technology, and particularly relates to a method for preparing tin oxide thin films and a solar cell. Background Art

[0002] Perovskite solar cells have made remarkable progress in the past decade or so. Their small-area efficiency has increased significantly from the initial 3.8% to 26.9%, and the efficiency of small-sized modules has also reached 24.7%. However, against the backdrop of increasingly fierce price competition in crystalline silicon photovoltaic technology, the cost advantage of perovskite photovoltaics has gradually shown a weakening trend. Therefore, how to develop a photovoltaic technology that combines high efficiency, stability, and large-scale preparation has become one of the core issues for future development.

[0003] In the process of promoting the industrialization of perovskite photovoltaics, the key challenges include: the stability of materials, the effectiveness of the transport layer and the active layer, and the feasibility of large-scale manufacturing. In particular, the electron transport layer (ETL) plays a crucial role in high-performance perovskite devices. It can not only effectively block the transport of holes but also reduce non-radiative recombination at the interface, thereby improving the photoelectric conversion efficiency of the device.

[0004] Currently, the preparation methods for high-performance normal devices mainly rely on two technologies: chemical bath deposition (CBD) and nanoparticle method. Since the technology was first published in 2021, chemical bath deposition (CBD) has become the main preparation method for high-performance normal devices. Although a relatively ideal electron transport layer can be obtained by depositing SnO2 or nano-tin oxide, its cost is high, and this method will cause the pH value to increase and a large amount of by-products to be generated during the reaction, resulting in waste liquid pollution problems. This method was initially proposed by a South Korean research team in the journal Nature (Nature, 2021, 590, 587-593.).

[0005] Another preparation method is the nanoparticle method based on the technology of ALFA Corporation. Since You et al. published relevant papers in Nature Energy in 2016 (Nat. Energy, 2016, 2, 16177.), this method has been widely used in the preparation of flat-panel devices due to its simple process and convenient operation. However, there is a problem of poor densification during the assembly of nanoparticles. Therefore, large-sized devices based on nanoparticles usually adopt secondary recombination to obtain a multi-layer composite structure to make up for this deficiency, which undoubtedly increases the complexity and cost of the production process. Currently, research on the electron transport layer mainly focuses on optimizing and improving these two methods.

[0006] In contrast, spray pyrolysis (J.Am.Chem.Soc., 2018, 1, 541-547.; Adv.EnergySustainability Res., 2022, 4, 2200150.) is used as an alternative technology for the preparation of electron transport layers. With its lower equipment cost, better controllability and film uniformity, it has shown great advantages in the preparation of electron transport layers. However, spray pyrolysis may lead to higher organic volatile organic compound (VOC) emissions in industrial production, poor charge extraction ability, and require multi-layer composites. In addition, due to high-temperature operation, the energy consumption is large, which makes its environmental friendliness and energy consumption issues urgently need to be solved. In addition, spray pyrolysis is similar to atomic layer deposition (ALD). Although it has a higher electron mobility, it has a low efficiency in carrier extraction in perovskite materials. In order to improve performance, SnO2 nanomaterials are usually required to be multi-layer composites, which not only increases the material cost, but also makes the production process more complicated.

[0007] In this context, how to directly coat SnO2 precursors on rough substrates such as FTO (fluorine-doped nickel tin oxide) glass surfaces at one time, and make the coating uniform and have good electrical properties, has become an important breakthrough direction for technological development. The surface of FTO glass has a relatively complex surface morphology, including narrow angle and wide angle areas, which leads to inconsistent dynamics of nucleation and crystallization before and after during large-scale scraping. This inconsistency will lead to differences in the density of the film, and then form leakage areas, which seriously affect the performance of the device. Therefore, there is an urgent need for a simple and feasible solution to improve the assembly behavior of tin oxide precursors on substrates such as rough FTO glass surfaces, ensure the consistency and electrical properties of the coating, and thus improve the overall efficiency and stability of perovskite solar cells. It is urgent to develop a simple, low-pollution, low-energy consumption and industrially suitable process method to meet the needs of large-scale production. Summary of the invention

[0008] The purpose of the present application is to solve the problems in the prior art in the preparation process of tin oxide thin films and to propose an optimized method for preparing tin oxide thin films.

[0009] The first aspect of the present application provides a method for preparing a tin oxide thin film, comprising:

[0010] Depositing a tin oxide precursor solution on a substrate and annealing the substrate to in-situ form a tin oxide film;

[0011] Wherein, the precursor solution includes a tin-containing compound, doping ions and additives;

[0012] The tin-containing compound is selected from one or more of stannous chloride (II), tin(IV) chloride, stannous iodide (II), tin(IV) iodide, stannous sulfate (II), or tin(IV) sulfate;

[0013] The doping ions are selected from one or more of Group IA, Group IIIA, and lanthanide metal ions;

[0014] The additive is an acidic additive.

[0015] According to the method of the first aspect, the doping ions are selected from In 3+ , Eu 2+ , La 3+ , Li + ; and / or

[0016] The acidic additive is a hydrohalic acid, preferably hydrochloric acid.

[0017] According to the method of the first aspect, the concentration of the tin-containing compound in the tin oxide precursor solution is 0.01 - 0.5 mol / L, preferably 0.1 - 0.3 mol / L; and / or

[0018] The concentration of the doping ions in the tin oxide precursor solution is 0.001 - 0.02 mol / L, preferably 0.002 - 0.008 mol / L.

[0019] According to the method of the first aspect, the solvent of the tin oxide precursor solution is selected from one or more of water, ethanol, 1-propanol, isopropanol, n-butanol (abbreviated as nBA), isobutanol, tert-butanol, pentanol, 2-pentanol, or ethylene glycol; and / or

[0020] The substrate is selected from FTO, ITO, or AZO, preferably FTO.

[0021] According to the method of the first aspect, the deposition method is selected from slot-die coating, dip coating, knife coating, or soaking, preferably slot-die coating or knife coating.

[0022] According to the method of the first aspect, the deposition method is a one-step knife coating method;

[0023] Preferably, the distance between the blade tip of the doctor blade and the substrate during knife coating is 0.1 - 0.5 mm;

[0024] Preferably, the knife coating rate is 5 - 20 mm / s; and / or

[0025] Preferably, the knife coating temperature is 25 - 100 °C;

[0026] More preferably, the knife coating temperature is 40 - 60 °C.

[0027] According to the method of the first aspect, the annealing treatment temperature is 100 to 230 °C, preferably 170 to 190 °C; and / or

[0028] the annealing treatment time is 30 to 120 min, preferably 50 to 70 min.

[0029] The second aspect of the present application provides a solar cell, which includes a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a counter electrode stacked in sequence. Among them, the electron transport layer is an indium tin oxide thin film prepared by the method of the first aspect;

[0030] Preferably, the solar cell is a normal structure cell.

[0031] For the solar cell according to the second aspect, the thickness of the electron transport layer is 5 to 50 nm.

[0032] For the solar cell according to the second aspect, the hole transport layer material is a p-type semiconductor, preferably selected from one or more of nickel oxide, Spiro-OMeTAD, poly-TPD, copper phthalocyanine, nickel phthalocyanine, poly(triarylamine), poly(3-hexylthiophene), molybdenum oxide; more preferably, the thickness of the hole transport layer is 30 to 150 nm;

[0033] The perovskite material has a general formula of ABX3, where A is one or more of monovalent cations of amino group, amidinium group, guanidinium group, cesium, and rubidium; B is Pb 2+ 、Sn 2+ one or more of them; X is Cl - 、Br - 、I - 、SCN - 、CH3COO - one or more of them; preferably, the molar fraction of lead ions in B is not less than 80%; more preferably, the thickness of the perovskite layer is 400 to 900 nm; and / or

[0034] The material of the counter electrode is selected from one or more of gold, silver, copper, ITO, and AZO, and the thickness of the counter electrode is preferably 60 to 300 nm.

[0035] The method of the present application has the following beneficial effects but is not limited to:

[0036] (1) Improve the nucleation and crystallization quality of indium tin oxide thin film: By regulating ion doping, solvent selection, and rapid supersaturation process, optimize the nucleation and crystallization behavior of indium tin oxide thin film on the FTO substrate, ensure the uniformity and denseness of the thin film, and then improve the electron transport performance of the thin film.

[0037] (2) Optimize the contact interface between perovskite and tin oxide: Improve the interface quality between perovskite and tin oxide. By adjusting the surface properties of the thin film, enhance the energy level matching between the two, reduce the electron recombination phenomenon, and improve the electron extraction efficiency.

[0038] (3) Reduce production costs and environmental impacts: By optimizing the solvent selection and coating process, reduce the emissions of volatile organic compounds (VOCs) during the production process, lower the production costs, meet the environmental protection requirements, and ensure the scalable application of the process. Brief Description of the Drawings

[0039] Figure 1 Shows the structure of the normal perovskite solar cell module prepared in Example 1.

[0040] Figure 2 Shows the wettability of different solvents on FTO glass.

[0041] Figure 3 Shows the influence of different solvents on the dispersion of SnCl2 colloid.

[0042] Figure 4 Shows the SEM images, C-AFM images and C-AFM surface current distributions of SnO2 prepared in different solvents.

[0043] Figure 5 Shows the influence of perovskite precursor on the wettability of SnO2 electron transport layer prepared with different solvents.

[0044] Figure 6 Shows the influence of doctor blade coating temperature on the front-back consistency of tin oxide. Detailed Description of the Embodiments

[0045] The present application will be further described in detail below with reference to the drawings and embodiments. Through these descriptions, the features and advantages of the present application will become more clearly defined.

[0046] The special term "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0047] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0048] Directly coating the SnO2 precursor on the rough substrate surface once and achieving coating uniformity and good electrical properties is an important technical breakthrough direction in the preparation of perovskite solar cells. However, due to technical problems in practical applications, there is no report on relevant technical routes. To achieve high-performance and stable tin oxide thin films, the following three key technical points need to be met. Although they are relatively independent, they complement each other and jointly determine the overall performance of the thin film.

[0049] 1. Assembly structure on the substrate surface

[0050] Through the spin-coating method, a 6×6 cm 2 module based on the ITO electrode successfully achieved a conversion efficiency of 18.7%. However, when the same solution formulation was applied to blade coating, its repeatability was poor.

[0051] In particular, the distribution uniformity of SnO2 in water as a solvent on the FTO surface is poor. This unsatisfactory assembly quality becomes a key factor restricting device performance. This is because the FTO glass surface has a complex surface topography, including narrow-angle and wide-angle regions. During the coating process, the kinetics of nucleation and crystallization before and after are inconsistent, resulting in differences in the density of the thin film. This inconsistency may cause defects or pores in the microstructure of different regions of the coating, thus generating differences in electrical properties and ultimately leading to the formation of leakage regions. This problem not only affects the overall performance of the device, but also reduces the photoelectric conversion efficiency and may lead to differences in long-term stability. In fact, the density of the coating directly affects the interface characteristics of the device and the carrier transport efficiency. Therefore, uneven or defective coatings will significantly reduce the overall efficiency of optoelectronic devices. Large-scale manufacturing requires a highly repeatable and easy-to-control production process, and this method may face great challenges in actual large-scale production, especially in how to control the consistency of the coating quality during the coating process.

[0052] 2. Energy level matching and surface defect concentration between the tin oxide thin film and the perovskite

[0053] The energy level matching and surface defect concentration between the tin oxide thin film and the perovskite material have a profound impact on the carrier extraction and recombination processes. The effective extraction and transport of carriers are key factors in the photoelectric conversion efficiency, and energy level matching and surface defects are the main factors affecting this process.

[0054] (1) Energy level matching: As an electron transport layer, tin oxide must be aligned with the conduction band of the perovskite to ensure that electrons can efficiently migrate from the perovskite to the tin oxide thin film and ultimately flow to the electrode. If the conduction band position of tin oxide does not match that of the perovskite, it will hinder the migration of electrons and reduce the device efficiency. Optimizing the doping or modification materials of the tin oxide thin film can adjust its conduction band position to better match the energy levels of the perovskite material, thereby improving the electron extraction efficiency.

[0055] (2) Surface defect concentration: The surface defects of the tin oxide film will become the centers of electron recombination, reducing the extraction efficiency of carriers. Defects such as oxygen vacancies and tin ion deficiencies in the tin oxide film will cause non-radiative recombination, wasting the absorbed light energy. Therefore, reducing the intrinsic defect concentration of the tin oxide film, especially the defect concentration at the interface with perovskite, is the key to improving the performance of perovskite solar cells.

[0056] 3. Influence of the substrate surface properties on the nucleation and crystallization of perovskite

[0057] The properties of the substrate surface have an important influence on the nucleation and crystallization processes of perovskite, and thus determine the optoelectronic performance of the final device. The quality of the perovskite film, especially the size, crystallization degree, and uniformity of its grains, is directly closely related to the nucleation behavior of the tin oxide film. The nucleation behavior of the tin oxide film on the FTO glass substrate has a significant impact on the crystallization quality of perovskite. Whether the substrate surface is flat and whether the surface energy is appropriate will affect the nucleation rate and uniformity of the perovskite precursor on it. If there are too many defects or chemical inhomogeneities on the substrate surface, it may lead to non-uniform nucleation of the perovskite film, resulting in grains with too large or irregular sizes, reducing the photoelectric conversion efficiency. By optimizing the surface treatment (such as surface modification or doping) of the tin oxide film, the nucleation process of the perovskite film can be improved, enhancing the crystallization quality and uniformity of the film.

[0058] This application provides a method for preparing a tin oxide film, including:

[0059] Depositing a tin oxide precursor solution on a substrate and annealing it in situ to form a tin oxide film;

[0060] Wherein, the precursor solution includes a tin-containing compound, doping ions, and an additive;

[0061] The tin-containing compound is selected from one or more of stannous chloride (II), tin(IV) chloride, stannous iodide (II), tin(IV) iodide, stannous sulfate (II), or tin(IV) sulfate;

[0062] The doping ions are selected from one or more of Group IA, Group IIIA, and lanthanide metal ions;

[0063] The additive is an acidic additive.

[0064] In the prior art, the nucleation and crystallization processes of tin oxide films often have non-uniformities, resulting in poor film densification and thus affecting the electron transport performance. To solve this problem, this application effectively regulates the nucleation and crystallization behavior of tin oxide films on conductive substrates, especially FTO substrates, through ion doping, solvent selection, and rapid supersaturation processes.

[0065] The present application provides an optimized method for preparing an SnO₂ electron transport layer, which overcomes the deficiencies of common techniques such as the CBD method, the nanoparticle method, the spray pyrolysis method, and the ALD method in the prior art. By improving process conditions, selecting appropriate solvents and dopants, the high quality, densification, uniformity, and charge transport ability of the SnO₂ thin film are ensured. The metal oxide electron transport layer material provided by the present application can have good assembly densification on the substrate, especially the FTO surface, optimize the interfacial energy level of the device, assist the high-quality growth of perovskite, thereby improving the device efficiency and extending the service life.

[0066] By optimizing these process parameters, it is possible to ensure the uniform nucleation of the tin oxide thin film on the FTO surface, form a high-quality crystalline thin film, and optimize the contact interface between perovskite and tin oxide, which has the advantages of low cost, scalable application, and environmental protection. This technology provides a reliable solution for the industrialization of perovskite solar cells, is expected to promote the application of photovoltaic technology in the field of clean energy, and provides strong support for the innovation of electronic devices.

[0067] The method of the present application has the value of improving industrial application:

[0068] (1) Overcome the problem of large pollution of the CBD method

[0069] Due to the use of a large number of chemical substances in the chemical deposition process, the traditional CBD method is prone to environmental pollution and waste discharge during the production process. By optimizing the process, the present application can significantly reduce the generation of harmful substances, thereby reducing environmental pollution, meeting the requirements of green environmental protection, and contributing to large-scale and low-cost production.

[0070] (2) Overcome the problems of complex synthesis process, poor film assembly densification, and poor charge transport ability in nanoparticle method deposition

[0071] The nanoparticle method often has problems such as cumbersome synthesis process, uneven thin film, and insufficient densification, resulting in low charge transport efficiency and affecting the overall performance of the device. Through the optimized method of the present application, the preparation process can be simplified, and the densification and uniformity of the thin film can be improved, thereby effectively improving the charge transport performance and enhancing the photoelectric conversion efficiency and stability of the device.

[0072] (3) Overcome the problems of large VOC emissions, high energy consumption, poor electron extraction ability, and the need for secondary composite with nanomaterials in the spray pyrolysis method

[0073] Although the spray pyrolysis method can prepare uniform and dense thin films, the high energy consumption caused by its high-temperature operation severely limits its industrial application. In addition, the SnO2 thin films prepared by the spray pyrolysis method usually need to be secondarily combined with nanomaterials to improve the electron extraction ability; in order to ensure uniform atomization, the precursor solution used in this method has a low concentration, resulting in low solvent utilization rate and thus generating high emissions of volatile organic compounds (VOCs). Through the optimized technology of this project, not only the VOC emissions and energy consumption are effectively reduced, but also the secondary combination step is avoided, thereby improving the electron extraction efficiency and providing a more sustainable solution for large-scale production.

[0074] (4) Overcome the problems of high equipment investment, low production efficiency, and the need for secondary combination in the ALD method

[0075] Although the atomic layer deposition (ALD) method can prepare high-quality thin films, its equipment cost is high, production efficiency is low, and usually a secondary combination step is required to improve the electronic properties. This application simplifies the preparation process, avoids the problems of high equipment investment and low production efficiency in the ALD method, and at the same time reduces the need for secondary combination, making the entire production process more efficient, economical, and more suitable for large-scale production.

[0076] In one embodiment, the doped ions are selected from one or more of In 3+ , Eu 2+ , La 3+ , Li + ; and / or

[0077] The acidic additive is a hydrohalic acid, preferably hydrochloric acid.

[0078] This application introduces doped ions, significantly improving the electrical properties and thermal stability of the SnO2 thin films. The doped electron transport layer can improve the efficiency of the device.

[0079] In one embodiment, the concentration of the tin-containing compound in the tin oxide precursor solution is 0.01 - 0.5 mol / L, preferably 0.1 - 0.3 mol / L.

[0080] For example, the concentration of the tin-containing compound in the tin oxide precursor solution can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L.

[0081] In this application, the concentration of the tin compound in the tin oxide precursor solution is set within the range of 0.01 to 0.5 mol / L, especially 0.1 to 0.3 mol / L, and a film layer with uniform thickness, high density, and excellent performance can be prepared. When the concentration of the tin compound in the precursor solution is too high, the solute content in the solution is high, the viscosity is high, and the fluidity is poor, making it difficult to form a uniform film layer. The non-equilibrium desolvation process is prone to form pores or defects, resulting in poor film layer uniformity and low density, which will have an adverse impact on the optoelectronic performance of the solar cell. When the concentration of the tin compound in the precursor solution is too low, the solute content in the solution is low, which may lead to incomplete coverage of the substrate surface, insufficient mechanical strength, and the film layer is prone to cracking or peeling, thus affecting the continuity and functionality of the film layer.

[0082] In one embodiment, the concentration of the doped ions in the tin oxide precursor solution is 0.001 to 0.02 mol / L, preferably 0.002 to 0.008 mol / L.

[0083] By setting the concentration of the doped ions in the tin oxide precursor solution within the above range, the conduction band position of the tin oxide thin film can be adjusted to better match the energy level of the perovskite material, thereby improving the electron extraction efficiency, and can also improve the nucleation and crystallization process of the perovskite thin film, enhancing the crystallization quality and uniformity of the thin film.

[0084] In one embodiment, the addition amount of the acidic additive in the tin oxide precursor solution is 0.5 to 3% vol, and the concentration of the acidic additive is 20% to 50%.

[0085] In one embodiment, the solvent of the tin oxide precursor solution is selected from one or more of water, ethanol, 1-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, 2-pentanol, or ethylene glycol; and / or

[0086] The substrate is selected from FTO (Fluorine-doped Tin Oxide), ITO (Indium-Tin Oxide), or AZO (Al-doped Zinc Oxide), preferably FTO.

[0087] This application optimizes the selection of the solvent. For example, n-butanol is used as the solvent to prepare the SnO2 thin film. The solvent used in this application has good wettability, which helps to form a uniform and dense thin film. At the same time, its dispersibility in the SnCl2 solution is better than that of other solvents, which is beneficial to improving the quality of the thin film, improving the buried interface of the perovskite, and enhancing the optoelectronic conversion efficiency and thermal stability of the overall device.

[0088] In one embodiment, the deposition method is selected from slot coating, dip coating, knife coating or soaking method, preferably slot coating or knife coating.

[0089] In a specific embodiment, the deposition method is a one-step knife coating method;

[0090] Preferably, the distance between the blade tip of the doctor blade and the substrate during knife coating is 0.1 - 0.5 mm;

[0091] The knife coating rate is 5 - 20 mm / s; and / or the knife coating temperature is 25 - 100 °C;

[0092] More preferably, the knife coating temperature is 40 - 60 °C.

[0093] In a preferred embodiment, the present application proposes a simple and low-cost one-step knife coating method to prepare the SnO2 electron transport layer. This method can not only overcome the environmental pollution and process complexity in traditional preparation methods, but also effectively improve the uniformity, denseness of the film and the contact performance between perovskite and SnO2, thereby improving the photoelectric conversion efficiency and stability of the device. In particular, by increasing the knife coating temperature, the present application reduces the nucleation energy barrier of the SnO2 precursor on the surface of the FTO glass, thereby promoting a more uniform nucleation process and improving the front-middle-back consistency of the large-size SnO2 film. This improvement helps to reduce the efficiency difference between sub-cells, thereby further improving the overall module performance and achieving the best comprehensive performance.

[0094] Specifically, the knife coating temperature can be 25 °C, 30 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 80 °C, 90 °C, 100 °C.

[0095] The knife coating temperature refers to the temperature of the substrate during knife coating. By controlling the knife coating temperature within the range of the present application, it is beneficial to control the drying rate and fluidity of the precursor solution, reduce the nucleation energy barrier of the SnO2 precursor on the substrate surface, promote a more uniform nucleation process, improve the front-middle-back consistency of the large-size SnO2 film, and prepare a uniform and dense SnO2 film layer, thereby improving the efficiency and stability of the module. When the knife coating temperature is too low, the drying rate is too low, which may cause the film layer to take too long to dry and incomplete drying, resulting in low production efficiency and poor front-middle-back consistency of the SnO2 film, which may lead to uneven film layer or surface defects, thereby affecting the performance of the solar cell; when the knife coating temperature is too high, the solvent evaporation rate is too fast, which may cause pores or defects to form on the surface of the film layer, and may also cause the mechanical properties of the film layer to decline, making it easy to crack or peel off.

[0096] In one embodiment, the annealing treatment temperature is 100 - 230 °C, preferably 170 - 190 °C; and / or

[0097] The annealing treatment time is 30 to 120 minutes, preferably 50 to 70 minutes.

[0098] This application also provides a solar cell, which includes a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a counter electrode stacked in sequence. Among them, the electron transport layer is the tin oxide thin film prepared by the foregoing method;

[0099] Preferably, the solar cell is a normal structure cell.

[0100] In one embodiment, the thickness of the electron transport layer is 5 to 50 nm.

[0101] In one embodiment, the hole transport layer material is a P-type semiconductor, preferably selected from one or more of nickel oxide, Spiro-OMeTAD, poly-TPD, copper phthalocyanine, nickel phthalocyanine, poly(triarylamine), poly(3-hexylthiophene), molybdenum oxide; more preferably, the thickness of the hole transport layer is 30 to 150 nm;

[0102] The perovskite material has a general formula of ABX3, where A is one or more of monovalent cations of amino group, amidino group, guanidine group, cesium, and rubidium; B is Pb 2+ , Sn 2+ One or more of them; X is Cl - , Br - , I - , SCN - , CH3COO - One or more of them; preferably, the molar fraction of lead ions in B is not less than 80%; more preferably, the thickness of the perovskite layer is 400 to 900 nm; and / or

[0103] The material of the counter electrode is selected from one or more of gold, silver, copper, ITO, and AZO, and the thickness of the counter electrode is preferably 60 to 300 nm.

[0104] This application has no special restrictions on the sources of all raw materials. Except as otherwise specified, they are all conventional products that can be obtained commercially.

[0105] The preparation method of this application includes:

[0106] Depositing the metal oxide precursor solution on the substrate film and annealing it at 100 to 230 °C for 30 to 120 minutes to in-situ form the metal oxide thin film.

[0107] The solute of the metal oxide precursor solution includes one or more combinations (0.05 - 0.3 M) selected from stannous chloride (II), tin(IV) chloride, stannous iodide (II), tin(IV) iodide, stannous sulfate (II), or tin(IV) sulfate. The additive includes a small amount of hydrochloric acid (0.01 - 2% vol), and the solvent includes one or a combination of water, ethanol, 1-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, 2-pentanol, or ethylene glycol.

[0108] The deposition method can be slit coating, dip coating, or doctor blade coating. Among them, the immersion method requires immersing the substrate film in the metal oxide precursor solution for 10 - 600 s.

[0109] In addition, the embodiments of the present application also provide the application of the above intermediate material in a normal structure solar cell.

[0110] The solar cell can include a transparent electrode (cathode), an electron transport layer, a perovskite layer, a hole transport layer, and a counter electrode (anode) stacked. The above metal oxide electron transport layer is applied to the electron transport layer.

[0111] The solar cell adopts a normal structure.

[0112] Among them, the material of the transparent electrode can be selected from one or more of ITO, FTO, and AZO.

[0113] Preferably, the material of the electron transport layer is the N-type semiconductor SnO2. More preferably, the thickness of the electron transport layer is 5 - 50 nm;

[0114] Preferably, the material of the hole transport layer is a P-type semiconductor, preferably selected from one or more of nickel oxide, Spiro-OMeTAD, poly-TPD, copper phthalocyanine, nickel phthalocyanine, poly(triarylamine), poly(3-hexylthiophene), and molybdenum oxide. More preferably, the thickness of the hole transport layer is 30 - 150 nm;

[0115] Among them, in the perovskite layer, the perovskite material has the general formula ABX3, where A is one or more of monovalent cations such as amino, amidino, guanidino, cesium, and rubidium; B is 2+ Pb 2+ Sn - Br - I - SCN - CH3COO - one or more of; preferably, the mole fraction of lead ions in B is not less than 80%; the thickness of the perovskite layer is 400 - 900 nm.

[0116] The material of the counter electrode can be selected from one or more of gold, silver, copper, ITO, and AZO, and the thickness of the counter electrode can be 60-300 nm.

[0117] Example 1

[0118] This example provides a normal-structure perovskite solar cell module, which includes a plurality of serially connected perovskite solar cell units on a glass substrate.

[0119] Among them, as Figure 1 shown, the structure of the perovskite solar cell unit includes, in a stacked manner in sequence: an FTO bottom electrode layer with a thickness of 200 nm disposed on a glass layer (Glass), an electron transport layer (ETL) with a thickness of 35 nm, and a perovskite layer (PVK) of FA 0.95 Cs 0.05 PbI3 with a thickness of 700 nm, a Spiro-OMeTAD with a thickness of 120 nm and a MoO x composite hole transport layer (Spiro-OMeTAD + MoO x ), and an ITO electrode layer with a thickness of 300 nm.

[0120] The preparation steps are as follows:

[0121] Step S1:

[0122] P1 scribing: Laser scribing treatment is performed on the FTO layer on the surface of a conductive substrate with a size of 6×6 cm 2 to form 8 sub-cell regions on the surface of the substrate.

[0123] Step S2:

[0124] Prepare the electron transport layer (Electron Transport Layer, ETL layer): 47.4 mg of SnCl2·2H2O, 1.33 mg of InCl3 and 1% vol of hydrochloric acid with a concentration of 37% are dissolved in 1 mL of water, aged for 12 h, and a SnO2 precursor solution is prepared. Then it is spin-coated on the surface of the cleaned FTO glass. During spin-coating, the distance between the blade tip and the glass is 0.1 mm, the spin-coating rate is 12 mm / s, and the spin-coating temperature is 25 °C. Finally, the sample is annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The normal-structure perovskite solar cell module prepared through this electron transport layer is labeled as T-1.

[0125] Step S3:

[0126] Prepare the perovskite light absorption layer: Dissolve FAI, CsI, and PbI2 in a mixed solution of NMP and DMF (1:6) to prepare a solution with a stoichiometric ratio of FA0.95 Cs 0.05 Perovskite solution of PbI3. Place the substrate with the electron transport layer prepared on the platform of the doctor blade coater. The distance between the blade tip and the glass is 0.15 mm, and the scraping speed is 15 mm / s. Inject the above perovskite solution into the gap between the doctor blade and the substrate, and then start the doctor blade coating equipment. After flash evaporation for 60 s, anneal at 150 °C for 15 min to obtain the perovskite layer (Perovskite Layer, PVK layer).

[0127] Step S4:

[0128] Prepare the Spiro-OMeTAD hole transport layer (Hole Transport Layer, HTL layer): Weigh 72 mg of Spiro-OMeTAD and add it to 1 mL of chlorobenzene, then add 17.5 μL of Li-TFSI / ACN (520 mg / mL) and 28.8 μL of TBP, and ultrasonically disperse for 10 min to prepare a chlorobenzene dispersion of Spiro-OMeTAD; Place the substrate with the prepared perovskite layer on the platform of the doctor blade coater. The distance between the blade tip and the glass is 0.10 mm, and the scraping speed is 10 mm / s. Inject the above hole transport layer solution into the gap between the doctor blade and the substrate, and then start the doctor blade coating equipment to obtain the hole transport layer by flash evaporation.

[0129] Step S5:

[0130] Prepare MoO x Hole transport layer: Evaporate 20 nm of MoO x Hole transport layer on Spiro-OMeTAD by thermal evaporation.

[0131] Step S6:

[0132] P2 scribing: Use a laser to perform P2 scribing on the electron transport layer, perovskite layer, and hole transport layer, so that the functional layer including the electron transport layer, perovskite layer, and hole transport layer is divided into 8 sub-functional regions. The distance between the P2 line and the P1 line is 20 μm, and the width of the P2 line is 60 μm.

[0133] Step S7:

[0134] Prepare the ITO electrode: Sputter a 300 nm ITO electrode by physical vapor deposition.

[0135] Step S8:

[0136] P3 scribing: Use a laser to perform P3 scribing on the perovskite layer, hole transport layer, and counter electrode layer, so that the functional layer including the perovskite layer, hole transport layer, and counter electrode layer is divided into 8 sub-cell regions. The distance between the P3 line and the P2 line is 20 μm, and the width of the P3 line is 50 μm.

[0137] The fabricated normal perovskite solar cell module is as Figure 1 shown.

[0138] Example 2

[0139] The normal perovskite solar cell module was fabricated according to the method of Example 1, except that in step S2, the electron transport layer was prepared by the following method:

[0140] 47.4 mg of SnCl2·2H2O, 1.33 mg of InCl3 and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of ethanol, aged for 12 h to obtain a precursor solution of SnO2. Then it was spin-coated on the surface of a cleaned FTO glass, with a distance of 0.1 mm between the blade tip and the glass during spin-coating, a spin-coating rate of 12 mm / s, and a spin-coating temperature of 25 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared with this electron transport layer was labeled as T-2.

[0141] Example 3

[0142] The normal perovskite solar cell module was fabricated according to the method of Example 1, except that in step S2, the electron transport layer was prepared by the following method:

[0143] 47.4 mg of SnCl2·2H2O, 1.33 mg of InCl3 and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of n-butanol, aged for 12 h to obtain a precursor solution of SnO2. Then it was spin-coated on the surface of a cleaned FTO glass, with a distance of 0.1 mm between the blade tip and the glass during spin-coating, a spin-coating rate of 12 mm / s, and a spin-coating temperature of 25 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared with this electron transport layer was labeled as T-3.

[0144] Example 4

[0145] The normal perovskite solar cell module was fabricated according to the method of Example 1, except that in step S2, the electron transport layer was prepared by the following method:

[0146] Every 47.4 mg of SnCl2·2H2O, 1.33 mg of InCl3, and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of n-butanol, aged for 12 h, and a precursor solution of SnO2 was prepared. Then, it was spin-coated on the surface of a cleaned FTO glass. During spin-coating, the distance between the blade tip and the glass was 0.1 mm, the spin-coating rate was 12 mm / s, and the spin-coating temperature was 55 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The forward-structure perovskite solar cell module prepared through this electron transport layer was labeled as T-4.

[0147] Example 5

[0148] The forward perovskite solar cell module was prepared according to the method of Example 1, with the only difference being that the electron transport layer was prepared by the following method in step S2:

[0149] Every 47.4 mg of SnCl2·2H2O, 0.25 mg of LiCl, and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of n-butanol, aged for 12 h, and a precursor solution of SnO2 was prepared. Then, it was spin-coated on the surface of a cleaned FTO glass. During spin-coating, the distance between the blade tip and the glass was 0.1 mm, the spin-coating rate was 12 mm / s, and the spin-coating temperature was 55 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The forward-structure perovskite solar cell module prepared through this electron transport layer was labeled as T-5.

[0150] Example 6

[0151] The forward perovskite solar cell module was prepared according to the method of Example 1, with the only difference being that the electron transport layer was prepared by the following method in step S2:

[0152] Every 47.4 mg of SnCl2·2H2O, 1.55 mg of EuCl3, and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of n-butanol, aged for 12 h, and a precursor solution of SnO2 was prepared. Then, it was spin-coated on the surface of a cleaned FTO glass. During spin-coating, the distance between the blade tip and the glass was 0.1 mm, the spin-coating rate was 12 mm / s, and the spin-coating temperature was 55 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron transport layer with a film thickness of 35 nm. The forward-structure perovskite solar cell module prepared through this electron transport layer was labeled as T-6.

[0153] Example 7

[0154] The forward perovskite solar cell module was prepared according to the method of Example 1, with the only difference being that the electron transport layer was prepared by the following method in step S2:

[0155] For every 47.4 mg of SnCl₂·2H₂O, 1.33 mg of InCl₃, and 1% vol of hydrochloric acid with a concentration of 37% are dissolved in 1 mL of isopropanol, aged for 12 h, to prepare a precursor solution of SnO₂. Then, it is spin-coated on the surface of a cleaned FTO glass. When spin-coating, the distance between the blade tip and the glass is 0.1 mm, the spin-coating rate is 12 mm / s, and the spin-coating temperature is 55 °C. Finally, the sample is annealed at 180 °C for 30 min to obtain a SnO₂ electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared through this electron transport layer is labeled as T-7.

[0156] Example 8

[0157] The normal perovskite solar cell module is prepared according to the method of Example 1, with the only difference being that in step S2, the electron transport layer is prepared by the following method:

[0158] For every 47.4 mg of SnCl₂·2H₂O, 2.23 mg of LaCl₃·7H₂O, and 1% vol of hydrochloric acid with a concentration of 37% are dissolved in 1 mL of ethanol, aged for 12 h, to prepare a precursor solution of SnO₂. Then, it is spin-coated on the surface of a cleaned FTO glass. When spin-coating, the distance between the blade tip and the glass is 0.1 mm, the spin-coating rate is 12 mm / s, and the spin-coating temperature is 55 °C. Finally, the sample is annealed at 180 °C for 30 min to obtain a SnO₂ electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared through this electron transport layer is labeled as T-8.

[0159] Comparative Example 1 (preparing the electron transport layer by CBD process)

[0160] The normal perovskite solar cell module is prepared according to the method of Example 1, with the only difference being that in step S2, the electron transport layer is prepared by the following method:

[0161] 50 μL of thioglycolic acid, 2.5 mL of concentrated hydrochloric acid (37 wt%), 0.55 g of SnCl₂·2H₂O, and 2.5 g of urea are added to 1 L of deionized water, stirred until completely dissolved to prepare a precursor solution by the CBD method. Then, the cleaned FTO glass is immersed in this precursor solution, placed in an oven at 90 °C for aging treatment for 3 h, and then cleaned. Finally, it is annealed at 180 °C for 30 min to obtain a SnO₂ electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared through this electron transport layer is labeled as C-1.

[0162] Comparative Example 2 (preparing the electron transport layer by nanoparticle method)

[0163] The normal - structure perovskite solar cell module was prepared according to the method of Example 1, except that in step S2, the electron - transport layer was prepared by the following method:

[0164] An aqueous solution of 1.7 wt% tin oxide was spin - coated on the cleaned FTO glass. The distance between the blade tip and the glass during spin - coating was 0.1 mm, and the spin - coating rate was 10 mm / s. After coating, the sample was annealed at 180 °C for 30 min, and finally a SnO2 electron - transport layer with a film thickness of 35 nm was obtained. The normal - structure perovskite solar cell module prepared with this electron - transport layer was labeled as C - 2.

[0165] Comparative Example 3 (preparing the electron - transport layer by spray pyrolysis + nanoparticle method)

[0166] The normal - structure perovskite solar cell module was prepared according to the method of Example 1, except that in step S2, the electron - transport layer was prepared by the following method:

[0167] First, a SnO2 layer was prepared on the cleaned FTO glass by spray pyrolysis. The spraying temperature was 200 °C and the number of spraying circles was 3. After spraying, the sample was annealed at 200 °C for 30 min and then cooled naturally. Then, an aqueous solution of 1.7 wt% tin oxide was spin - coated. The distance between the blade tip and the glass during spin - coating was 0.1 mm, and the spin - coating rate was 10 mm / s. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron - transport layer with a film thickness of 35 nm. The normal - structure perovskite solar cell module prepared with this electron - transport layer was labeled as C - 3.

[0168] Comparative Example 4

[0169] The normal - structure perovskite solar cell module was prepared according to the method of Example 1, except that in step S2, the electron - transport layer was prepared by the following method:

[0170] Every 47.4 mg of SnCl2·2H2O and 1% vol of hydrochloric acid with a concentration of 37% were dissolved in 1 mL of water and aged for 12 h to prepare a precursor solution of SnO2. Then it was spin - coated on the surface of the cleaned FTO glass. The distance between the blade tip and the glass during spin - coating was 0.1 mm, the spin - coating rate was 12 mm / s, and the spin - coating temperature was 25 °C. Finally, the sample was annealed at 180 °C for 30 min to obtain a SnO2 electron - transport layer with a film thickness of 35 nm. The normal - structure perovskite solar cell module prepared with this electron - transport layer was labeled as C - 4.

[0171] Comparative Example 5

[0172] The normal - structure perovskite solar cell module was prepared according to the method of Example 1, except that in step S2, the electron - transport layer was prepared by the following method:

[0173] Preparation of precursor solution: Dissolve stannous chloride (SnO₂·2H₂O) in absolute ethanol to prepare a 0.8 mol / L solution. At the same time, add a small amount of concentrated hydrochloric acid (0.2 mL) and surfactant (ethylene glycol) to improve the quality of the film. Finally, place it on a magnetic stirrer and stir evenly to obtain the SnO₂ precursor solution. Then add LaCl₃·7H₂O with an atomic ratio of (La:Sn) of 1 - 3 at%, forming a rare-earth doped solution.

[0174] Film deposition: Use ultrasonic spray pyrolysis (USP) to generate SnO₂:La film. The substrate temperature is controlled between 300 - 600 °C, the spray air pressure is set at 2 - 3 bar, the atomizer frequency is set at 1.7 MHz, the spray rate is 2 mL / min, and the spray distance from the substrate is 15 cm. After the deposition starts, the tin oxide film grows layer by layer on the substrate surface to form the SnO₂:La film (control the spray time to be 15 - 30 min). The normal structure perovskite solar cell module prepared through this electron transport layer is marked as C-5.

[0175] Comparative Example 6

[0176] Prepare a normal perovskite solar cell module according to the method of Example 1, with the only difference being that in step S2, the electron transport layer is prepared by the following method:

[0177] Dissolve 47.4 mg of SnCl₂·2H₂O and 1% vol of hydrochloric acid with a concentration of 37% in 1 mL of n-butanol, age for 12 h to obtain the SnO₂ precursor solution. Then scrape-coat it on the surface of the cleaned FTO glass. The distance between the blade tip and the glass during scraping is 0.1 mm, the scraping rate is 12 mm / s, and the scraping temperature is 55 °C. Finally, anneal the sample at 180 °C for 30 min to obtain an SnO₂ electron transport layer with a film thickness of 35 nm. The normal structure perovskite solar cell module prepared through this electron transport layer is marked as C-6.

[0178] Perform photoelectric performance tests on the normal structure perovskite solar cell modules prepared in Examples 1 - 8 and Comparative Examples 1 - 6. The test method is well-known in the art.

[0179] Table 1

[0180]

[0181]

[0182]

[0183] *Note: Among them, the aging condition for the retention rate of the photoelectric conversion efficiency of the device after 1000h aging is 65°C in a nitrogen atmosphere.

[0184] As can be seen from Table 1, compared with Comparative Example 1 (preparing the electron transport layer by the CBD process), Comparative Example 2 (preparing the electron transport layer by the nanoparticle method), Comparative Example 3 (preparing the electron transport layer by spray pyrolysis + nanoparticle method), and Comparative Example 5 (preparing the electron transport layer by ultrasonic spray pyrolysis), the device with the SnO2 electron transport layer provided in Example 4 (one-step blade coating method) of the present application has higher photoelectric conversion efficiency and better thermal stability.

[0185] In terms of solvent selection, when comparing Example 2 (using ethanol as the solvent) with Example 3 (using n-butanol as the solvent), and Example 7 (using isopropanol as the solvent) with Example 6 (using n-butanol as the solvent), the devices with the SnO2 electron transport layer prepared with n-butanol as the solvent provided in the examples of the present application showed higher photoelectric conversion efficiency and thermal stability. This result is consistent with the results of the contact angle test ( Figure 2 ) and the dynamic light scattering test ( Figure 3 ). As can be seen from the Figure 2 contact angle test, n-butanol solvent has better surface wettability for FTO glass. At the same time, 47.4 mg of SnCl2·2H2O was dispersed in 1 mL of different solvents (water, ethanol, n-butanol) for dynamic light scattering test, and the test results are as shown in Figure 3 . As can be seen from the Figure 3 dynamic light scattering test, the dispersion of SnCl2 in n-butanol is also better, the formed colloid size is the smallest (0.65 nm), and the particle size distribution is the narrowest, while the colloid sizes formed in ethanol and water are larger and the particle size distributions are wider, indicating that using n-butanol as the solvent helps to form a continuous and dense SnO2 film compared with the solvents ethanol and water. Figure 4 shows the SEM images, C-AFM images and C-AFM surface current distributions of SnO2 prepared in different solvents. As can be seen from Figure 4 , there are a large number of leakage points in the SnO2 film prepared with water as the solvent (Example 1), and the surface current distributions of the films prepared with ethanol as the solvent (Example 2) and n-butanol as the solvent (Example 3) are relatively uniform. Moreover, the film prepared with n-butanol has better conductivity, and the overall surface current value is significantly higher than that of the SnO2 film with ethanol as the solvent.

[0186] Further, by performing contact angle tests on the wettability of the perovskite precursor solution (i.e., the perovskite solution prepared in step S3) on the SnO2 substrates prepared with different solvents in Examples 1 to 3, the results are as shown in Figure 5As shown, the SnO2 substrate prepared with n-butanol solvent has better wettability, which helps to improve the quality of the buried interface of perovskite.

[0187] In the comparison between Example 3 and Example 4, it can be found that by further increasing the spin-coating substrate temperature, the efficiency and stability of the component have been significantly improved. For another example, through the comparison between Example 7 and Example 2, it can be seen that although in the contact angle test ( Figure 2 ), the solvent (ethanol) of Example 2 has better wettability on FTO glass than the solvent (isopropanol) of Example 7, but Example 7 effectively improves the efficiency and stability of the component by increasing the substrate temperature. Figure 6 The SEM images of the SnO2 thin films prepared in Example 3 (spin-coating temperature 25 °C) and Example 4 (spin-coating temperature 55 °C) at the front, middle, and end of spin-coating are shown. From Figure 6 it can be seen that when the spin-coating substrate temperature is increased, the front-middle-back consistency of the obtained SnO2 thin film is more excellent. This is mainly due to the fact that the increase in temperature reduces the nucleation energy barrier of the SnO2 precursor on the surface of FTO glass, thus promoting a more uniform nucleation process and improving the front-middle-back consistency of the large-size SnO2 thin film. This improvement helps to reduce the efficiency difference between sub-cells, thereby further improving the overall component performance and achieving the best comprehensive performance.

[0188] In addition, in the selection of doping ions, when comparing Comparative Example 4 (without adding In3+) with Example 1 (adding In 3+ ), adding In 3+ significantly improves the efficiency and thermal stability of the component. Similarly, under the same spin-coating substrate temperature, by comparing Comparative Example 6 (without addition), Example 5 (adding Li + ), Example 6 (adding Eu 3+ ), and Example 8 (adding La 3+ ), it can be seen that by adding different types of doping ions, the photoelectric conversion efficiency of the obtained components is significantly improved. It shows that the method of the present application by selectively adding doping ions in the electron transport layer is beneficial to improving the efficiency of the device.

[0189] The above has described the present application in combination with preferred embodiments. However, these embodiments are only exemplary and only serve an illustrative purpose. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

Claims

1. A method for preparing a tin oxide thin film, comprising: Depositing a tin oxide precursor solution on a substrate and annealing the substrate to in-situ form a tin oxide film; Wherein, the precursor solution includes a tin-containing compound, doping ions and additives; The tin-containing compound is selected from one or more of stannous chloride (II), tin (IV) chloride, stannous iodide (II), tin (IV) iodide, stannous sulfate (II) or tin (IV) sulfate; The doping ions are selected from one or more of group IA, group IIIA, and lanthanide metal ions; The additive is an acidic additive.

2. The method according to claim 1, characterized in that The doping ions are selected from In 3+ 、Eu 2+ ,La 3+ , Li + One or more of; and / or The acidic additive is a hydrohalic acid, preferably hydrochloric acid.

3. The method according to claim 1, characterized in that: The concentration of the tin compound in the tin oxide precursor solution is 0.01 to 0.5 mol / L, preferably 0.1 to 0.3 mol / L; and / or The concentration of doping ions in the tin oxide precursor solution is 0.001 to 0.02 mol / L, preferably 0.002 to 0.008 mol / L.

4. The method according to claim 1, characterized in that: The solvent of the tin oxide precursor solution is selected from one or more of water, ethanol, 1-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, 2-pentanol or ethylene glycol; and / or The substrate is selected from FTO, ITO or AZO, preferably FTO.

5. The method according to claim 1, characterized in that The deposition method is selected from the group consisting of slit coating, pull-up coating, blade coating or immersion, preferably slit coating or blade coating.

6. The method according to claim 5, characterized in that The deposition method is a one-step scraping method; Preferably, the distance between the blade head of the scraper and the substrate during the scraping is 0.1 to 0.5 mm; Preferably, the scraping speed is 5 to 20 mm / s; and / or Preferably, the scraping temperature is 25 to 100°C; More preferably, the coating temperature is 40-60°C.

7. The method according to claim 1, characterized in that The annealing temperature is 100-230° C., preferably 170-190° C.; and / or The annealing treatment time is 30 to 120 minutes, preferably 50 to 70 minutes.

8. A solar cell, comprising a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer and a counter electrode arranged in a stacked manner, wherein: The electron transport layer is a tin oxide thin film prepared by any one of claims 1 to 7; Preferably, the solar cell is a normal structure cell.

9. The solar cell according to claim 8, characterized in that: The thickness of the electron transport layer is 5 to 50 nm.

10. The solar cell according to claim 8, characterized in that The hole transport layer material is a P-type semiconductor, preferably one or more selected from nickel oxide, Spiro-OMeTAD, poly-TPD, copper phthalocyanine, nickel phthalocyanine, poly(triarylamine), poly(3-hexylthiophene), and molybdenum oxide. More preferably, the hole transport layer has a thickness of 30 to 150 nm. The perovskite material has a general formula of ABX3, wherein A is one or more monovalent cations of amine, amidine, guanidine, cesium, and rubidium; B is Pb 2+ Sn 2+ One or more of; X is Cl - Br - ,I - 、SCN - 、CH3COO - One or more of; preferably, the molar fraction of lead ions in B is not less than 80%; more preferably, the thickness of the perovskite layer is 400 to 900 nm; and / or The material of the counter electrode is selected from one or more of gold, silver, copper, ITO, and AZO, and the thickness of the counter electrode is preferably 60 to 300 nm.

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