Perovskite film and preparation method thereof, perovskite solar cell

Abstract

The application relates to the technical field of solar cell materials, in particular to a perovskite film, a preparation method thereof and a perovskite solar cell. The preparation method of the perovskite film comprises the following steps: preparing a divalent inorganic salt aqueous solution, wherein the divalent inorganic salt in the divalent inorganic salt aqueous solution is an inorganic salt corresponding to a divalent cation pair of the perovskite; performing film forming treatment on the divalent inorganic salt aqueous solution to obtain a divalent inorganic salt film; soaking the divalent inorganic salt film in a methyl halide ammonium solution for soaking treatment; coating a solution containing a formamidine halide salt on the divalent inorganic salt film after drying; and performing annealing treatment to obtain a perovskite film containing an organic-inorganic hybrid perovskite; wherein the methyl halide ammonium solution contains a linear alkyl halide ammonium with 2-5 carbons. The application can make the monovalent cations in the perovskite film uniformly distributed, so that the perovskite film shows a larger grain size, a lower charge trap density and a longer carrier lifetime, and can be well used in a solar cell.

Description

Technical Field

[0001] The present application belongs to the technical field of solar cell materials, and in particular relates to a perovskite film and a preparation method thereof, and a perovskite solar cell. Background Art

[0002] Perovskite materials are a class of semiconductor materials with uniform size and high color purity. Their elemental composition has a crystal structure similar to the mineral CaTiO3, making them a highly promising photovoltaic material. Perovskite materials possess strong light absorption capacity and a wide absorption range, offering significant advantages in the optoelectronics field. For example, perovskite solar cells (PSCs), which use perovskite materials as the light-absorbing layer, have seen rapid development. Their exceptional carrier mobility, high absorption coefficient, and low-cost solution processing have attracted widespread attention from the business community.

[0003] Solution-based perovskite synthesis has excellent power conversion efficiency (PCE). However, the aprotic polar solvents used to prepare perovskites, such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP), are often skin-penetrating and carcinogenic. The toxicity of these solvents in the perovskite production process can adversely affect the health of manufacturing workers, hinder industrial production, and bring environmental pollution risks. Therefore, from the perspective of green chemistry, aqueous synthesis of perovskites has been applied.

[0004] Current methods for synthesizing perovskites in aqueous systems involve converting a divalent inorganic salt aqueous solution into a divalent inorganic salt film, which is then converted into an organic-inorganic hybrid perovskite via a solid-liquid reaction system. However, this conversion process is prone to uneven exchange of monovalent cations, which can affect the performance of the final perovskite film. Summary of the Invention

[0005] The purpose of this application is to provide a perovskite film and a preparation method thereof, and a perovskite solar cell, aiming to solve the technical problem of how to make the perovskite monovalent cations in the perovskite film uniformly distributed to improve its performance.

[0006] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0007] In a first aspect, the present application provides a method for preparing a perovskite film, comprising:

[0008] preparing a divalent inorganic salt aqueous solution, wherein the divalent inorganic salt in the divalent inorganic salt aqueous solution is an inorganic salt corresponding to the divalent cation of perovskite;

[0009] subjecting the divalent inorganic salt aqueous solution to a film-forming treatment to obtain a divalent inorganic salt film;

[0010] The divalent inorganic salt film is immersed in a methylammonium halide solution, and after drying, coated with a solution containing a formamidine halide salt and annealed to obtain a perovskite film containing an organic-inorganic hybrid perovskite;

[0011] Wherein, the methyl ammonium halide solution contains linear alkyl ammonium halide with 2 to 5 carbon atoms.

[0012] In some embodiments, the linear alkyl ammonium halide includes at least one of ethylammonium chloride, propylammonium chloride, and butylammonium chloride.

[0013] In some embodiments, the molar ratio of the methylammonium halide to the linear alkylammonium halide in the methylammonium halide solution is (5-6):1;

[0014] And / or the concentration of methylammonium halide in the methylammonium halide solution is 8-12 mg / mL.

[0015] In some embodiments, the methylammonium halide in the methylammonium halide solution comprises methylammonium iodide and methylammonium chloride in a molar ratio of (3.5-4.5):1;

[0016] And / or, the solution containing formamidine halide salt contains formamidine iodide and methylammonium iodide dissolved in a molar ratio of (7-10):1.

[0017] In some embodiments, the soaking treatment includes multiple times of the following process: soaking for 4 to 5 minutes and then drying with nitrogen;

[0018] And / or, the annealing treatment time is 140-160°C.

[0019] In some embodiments, the solvent in the methylammonium halide solution is an alcohol solvent, and the solvent in the solution containing the formamidine halide salt is an alcohol solvent.

[0020] In some embodiments, the concentration of the divalent inorganic salt in the divalent inorganic salt aqueous solution is 1.0 to 2.0 mol / L;

[0021] And / or, the divalent inorganic salt includes at least one of nitrate and acetate corresponding to the divalent cation of the perovskite.

[0022] In some embodiments, the step of forming a film with the divalent inorganic salt aqueous solution comprises: coating the divalent inorganic salt aqueous solution into a film under the conditions of relative humidity <10% and temperature <20° C., and then performing a drying treatment.

[0023] In a second aspect, the present application provides a perovskite film prepared by the preparation method provided in the first aspect of the present application.

[0024] In a third aspect, the present application provides a perovskite solar cell, comprising the perovskite film provided in the second aspect of the present application.

[0025] The first aspect of the present application provides a method for preparing a perovskite film, in which a divalent inorganic salt film is immersed in a methylammonium halide solution to generate a methylamine-based perovskite, and then coated with a solution containing a formamidine halide salt for annealing. Methylamine ions and formamidine ions are exchanged in a solid-liquid system. Since the previous methylammonium halide solution contains linear alkylammonium halides with 2 to 5 carbon atoms, the linear alkylammonium halide decomposes into alkylamines with a higher boiling point than methylamine during the subsequent annealing process, thereby promoting the top-down diffusion of formamidine ions in the solid-liquid system. The exchange process achieves homogenization of the formamidine ion and methylamine ion components, thereby promoting the uniformity of the aqueous organic-inorganic hybrid perovskite components. The resulting perovskite film exhibits a larger grain size, lower charge trap density, and longer carrier lifetime, and can be well used in solar cells.

[0026] The perovskite film provided in the second aspect of the present application is prepared by the preparation method provided in the first aspect of the embodiment of the present application. Therefore, the monovalent organic cations in the perovskite film of the present application are evenly distributed, have a low charge trap density and a long carrier lifetime, and can be well used in solar cells.

[0027] The perovskite solar cell provided in the third aspect of the present application includes the perovskite film provided in the second aspect of the present application. Based on the advantages of the perovskite film, the perovskite solar cell of the present application has good conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 is an XRD pattern of the perovskite film provided in the examples of the present application; wherein, MAX+EA corresponds to the perovskite film in the perovskite solar cell of Example 1, MAX+PA corresponds to the perovskite film in the perovskite solar cell of Example 2, MAX+BA corresponds to the perovskite film in the perovskite solar cell of Example 3, and MAX corresponds to the perovskite film in the perovskite solar cell of Example 1;

[0030] Figure 2is a micro-morphology diagram of the perovskite film provided by the embodiment of the present application; wherein, MAX+EA corresponds to the perovskite film in the perovskite solar cell of embodiment 1, MAX+PA corresponds to the perovskite film in the perovskite solar cell of embodiment 2, MAX+BA corresponds to the perovskite film in the perovskite solar cell of embodiment 3, and MAX corresponds to the perovskite film in the perovskite solar cell of comparative example 1.

[0031] Figure 3 is a photovoltaic efficiency diagram of the perovskite solar cell device provided by the embodiment of the present application; wherein, MAX+PA corresponds to the efficiency curve of the perovskite solar cell of embodiment 2, and MAX corresponds to the efficiency curve of the perovskite solar cell of comparative example 1. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0033] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0034] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items.

[0035] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0036] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0037] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0038] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0039] Organic-inorganic hybrid perovskite solar cells have significantly improved their photoelectric conversion efficiency. From a green chemistry perspective, using aqueous solvents to synthesize these materials is ideal and environmentally friendly. Therefore, using aqueous solutions of divalent inorganic salts (e.g., aqueous lead nitrate precursors) to prepare perovskites has been well-used.

[0040] After the divalent inorganic salt aqueous solution system is made into a divalent inorganic salt film, it is then converted into an organic-inorganic hybrid perovskite through a solid-liquid reaction system. However, during this conversion process, if the MA-FA cation is exchanged during the annealing process, + In comparison, FA + The diffusion rate is slow, and the perovskite film will have an uneven distribution of monovalent cations, that is, there is still a certain amount of FA + and MA + They are enriched on the upper surface of the film and the buried interface respectively. This will cause stress in the lattice and energy level mismatch at the perovskite / electron transport layer interface, hindering carrier transport and ultimately limiting the PCE of the device.

[0041] Based on this, the present invention proposes introducing a linear alkyl ammonium halide with a certain carbon number. This involves immersing the divalent inorganic salt membrane in a methylammonium halide solution containing linear alkyl ammonium halides with 2 to 5 carbon atoms. This allows for a more uniform monovalent cation composition of the aqueous perovskite during subsequent annealing. The specific technical solution is as follows.

[0042] In a first aspect, the present invention provides a method for preparing a perovskite film. Specifically, the method comprises:

[0043] S01: preparing a divalent inorganic salt aqueous solution, wherein the divalent inorganic salt in the divalent inorganic salt aqueous solution is an inorganic salt corresponding to the divalent cation of the perovskite;

[0044] S02: treating the divalent inorganic salt aqueous solution to form a film to obtain a divalent inorganic salt film;

[0045] S03: placing the divalent inorganic salt film in a methylammonium halide solution for immersion treatment, coating it with a solution containing a formamidine halide salt after drying and annealing it to obtain a perovskite film containing an organic-inorganic hybrid perovskite; wherein the methylammonium halide solution contains a linear alkyl ammonium halide with 2 to 5 carbon atoms.

[0046] The embodiment of the present application is based on the fact that a methylammonium halide solution contains a linear alkyl ammonium halide with 2 to 5 carbon atoms. In the subsequent annealing process, the linear alkyl ammonium halide decomposes into an alkylamine with a higher boiling point than methylamine, thereby promoting the top-down diffusion of formamidinium ions in the solid-liquid system. The exchange process achieves the homogenization of the formamidinium ion and methylamine ion components, thereby promoting the uniformity of the aqueous organic-inorganic hybrid perovskite components. The resulting perovskite film exhibits a larger grain size, a lower charge trap density, and a longer carrier lifetime.

[0047] In step S01, the divalent inorganic salt in the divalent inorganic salt aqueous solution is an inorganic salt corresponding to the divalent cation of the perovskite. For example, the chemical formula of the organic-inorganic hybrid perovskite material can be ABM3; wherein A is a monovalent organic cation, which can include CH3NH3 + (MA + )、CH(NH2)2 + (FA + ), B is a divalent metal cation, specifically Pb 2+ 、Sn 2+ At least one of; M is a monovalent anion, specifically a halogen ion, including Cl - Br - and I - At least one of .

[0048] For example, in the organic-inorganic hybrid perovskite, the divalent metal ion may be a lead ion or a tin ion, and the divalent inorganic salt may be a lead salt or a tin salt. Specifically, the divalent inorganic salt may be a corresponding acetate or nitrate. For example, the lead salt may be lead nitrate or lead acetate, and the tin salt may be tin nitrate or tin acetate.

[0049] The preparation step of the divalent inorganic salt aqueous solution may be: adding the divalent inorganic salt into water and dissolving it to obtain the divalent inorganic salt aqueous solution.

[0050] In some embodiments, the concentration of the divalent inorganic salt in the divalent inorganic salt aqueous solution is 1.0-2.0 mol / L.

[0051] Step S02 is a film-forming process of a divalent inorganic salt aqueous solution.

[0052] In some embodiments, the step of film-forming the divalent inorganic salt aqueous solution comprises: coating the divalent inorganic salt aqueous solution to form a film under the conditions of relative humidity <10% and temperature <20° C., and then performing a drying treatment.

[0053] In some embodiments, the temperature of the divalent inorganic salt aqueous solution after coating is 80-100° C. and the time is 20-40 minutes. Under the above conditions, the aqueous solvent can be dried well.

[0054] Step S03 is a step of generating an organic-inorganic hybrid perovskite.

[0055] First, a divalent inorganic salt film is placed in a methylammonium halide solution for immersion treatment to obtain a methylamine-based perovskite. After drying, it is coated with a solution containing a formamidinium halide salt and annealed to obtain a formamidinium-based organic-inorganic hybrid perovskite. In this process, the divalent inorganic salt film is first converted into a methylamine-based perovskite, and then converted into a formamidinium-based organic-inorganic hybrid perovskite through the exchange of monovalent ions. The desired formamidinium-based organic-inorganic hybrid perovskite can be obtained according to the configuration of monovalent cations in the solution containing the formamidinium halide salt, for example, a formamidinium-methylamine-based (different stoichiometric ratio) organic-inorganic hybrid perovskite. The methylammonium halide solution contains a linear alkyl ammonium halide with 2 to 5 carbon atoms, wherein the halogen atom can be chlorine, bromine, iodine, etc.

[0056] In some embodiments, the linear alkylammonium halide includes at least one of ethylammonium halide, propylammonium halide, and butylammonium halide, such as at least one of ethylammonium chloride, propylammonium chloride, and butylammonium chloride.

[0057] The above-mentioned linear alkyl ammonium halides can spontaneously decompose into alkylamine and HCl (deprotonation) during the annealing process. For example, ethylammonium chloride decomposes into ethylamine and HCl, propylammonium chloride decomposes into propylamine and HCl, and butylammonium chloride decomposes into butylamine and HCl.

[0058] Methylamine, vapor pressure 186.1kPa, boiling point -6.6℃; ethylamine, vapor pressure 121.1kPa, boiling point 17℃; propylamine, vapor pressure 33.01.1kPa, boiling point 47~51℃; butylamine, vapor pressure 9.07kPa, boiling point 77~79℃. Compared with methylamine, which evaporates at room temperature, the presence of ethylamine, propylamine and butylamine with higher boiling points will carry FA +It fully diffuses from top to bottom along the grain boundary. This solid-liquid diffusion promotes full FA-MA exchange. The slow decomposition and volatilization of the straight-chain alkyl ammonium halide can prolong the FA-MA exchange time and make the FA more evenly distributed in the film. It should be noted that the implementation of this application found through research that if the above-mentioned straight-chain alkyl ammonium halide is not added to the methyl ammonium halide solution, but is added to the subsequent solution containing formamide halide, and is deposited on the surface of the MA-based perovskite by spin coating, because the alkylamine ions in the straight-chain alkyl ammonium halide are large in size and have a slow diffusion rate, the spin coating step makes it difficult for the straight-chain alkyl ammonium halide to be evenly distributed from top to bottom at the perovskite grain boundary. It is only distributed on the upper surface and cannot play a mediating role during the annealing process, resulting in FA + Therefore, in the preparation method of the embodiment of the present application, the linear alkyl ammonium halide is added to the methyl ammonium halide solution.

[0059] In some embodiments, the molar ratio of methylammonium halide to linear alkylammonium halide in the methylammonium halide solution is (5-6):1, and the concentration of methylammonium halide in the methylammonium halide solution is 8-12 mg / mL. At this concentration, the linear alkylammonium halide has a good regulating effect.

[0060] In some embodiments, each soaking treatment lasts for 4 to 5 minutes, followed by drying with nitrogen, and can be performed 3 to 4 times. This allows for sufficient conversion to obtain methylamino perovskite.

[0061] In some embodiments, the annealing treatment time is 140-160° C. Under this condition, the formamidinium-based perovskite can be fully converted into a formamidinium-based organic-inorganic hybrid perovskite.

[0062] Specifically, the methylammonium halide solution contains methylammonium iodide (MAI) and methylammonium chloride (MACl) dissolved in a molar ratio of (3.5-4.5):1; the solution containing formamidinium halide contains formamidinium iodide (FAI) and methylammonium iodide (MAI) dissolved in a molar ratio of (7-10):1. The resulting formamidinium-based organic-inorganic hybrid perovskite can contain both formamidinium and methylamino-based organic-inorganic hybrid perovskites. Furthermore, the solution containing formamidinium halide also contains methylammonium chloride (MACl). The solvent in the methylammonium halide solution and the solution containing formamidinium halide can be an alcohol solvent, such as isopropyl alcohol (IPA).

[0063] Furthermore, a passivation agent can be spin-coated on the surface of the perovskite film. For example, a passivation agent solution (the passivation agent is phenylethylamine iodide (PEAI), the solvent is isopropyl alcohol, and the concentration is 4-6 mg / mL) is spin-coated on the surface of the perovskite film and then dried.

[0064] In a second aspect, embodiments of the present application provide a perovskite film. Specifically, the perovskite film of the present application is prepared using the preparation method provided in the first aspect of the present application. The perovskite film of the present application has a uniform distribution of monovalent organic cations, a low charge trap density, and a long carrier lifetime, making it well-suited for use in solar cells.

[0065] In a third aspect, an embodiment of the present application provides a perovskite solar cell. The perovskite solar cell of the embodiment of the present application includes the perovskite film provided in the second aspect of the present application.

[0066] The perovskite solar cell provided in the third aspect of the present application includes the perovskite film provided in the second aspect of the present application. Based on the advantages of the perovskite film, the perovskite solar cell of the present application has good conversion efficiency.

[0067] Specifically, the perovskite solar cell of the embodiment of the present application includes a first electrode, a second electrode, and a perovskite layer located between the first electrode and the second electrode. An electron transport layer is provided between the perovskite layer and the first electrode. The perovskite layer is the perovskite film obtained by the above-mentioned preparation method of the embodiment of the present application.

[0068] In some embodiments, the electron transport layer can be a metal oxide or a doped metal oxide. For example, the metal oxide can include at least one of TiO2, meso-TiO2, NiOx, SnO2, ZrO2, and ZnO. In the embodiments of the present application, titanium dioxide and lithium-doped titanium dioxide can be used. The electron transport layer can be a single metal oxide layer or two stacked metal oxide layers.

[0069] In some embodiments, the first electrode may be a transparent conductive substrate, including but not limited to the following materials: fluorine-doped tin oxide (FTO), indium-doped tin oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), indium-doped zinc oxide (IZO), etc. The second electrode may be a metal top electrode, such as gold, silver, copper, etc., or one or more conductive oxide electrodes.

[0070] The above-mentioned method for preparing a perovskite solar cell includes: 1) preparing an electron transport layer on a first electrode; 2) preparing a perovskite layer on the electron transport layer, that is, the perovskite film can be prepared using the preparation method provided in the first aspect of the embodiment of the present application; 3) preparing a second electrode on the perovskite layer. Through this method, a perovskite film with a uniform distribution of monovalent organic cations can be prepared on the electron transport layer. During the preparation of the perovskite film, during the divalent inorganic salt / perovskite conversion process, a linear alkyl ammonium halide (such as ethylammonium chloride EACl, propylammonium chloride PACl or butylammonium chloride BACl) is introduced into a methylammonium halide solution for immersion, and the subsequent coating process of the solution containing formamidine halide promotes FA-MA cation exchange during annealing, and promotes the uniform distribution of monovalent cations in the aqueous perovskite by means of the mediation of the long-chain alkyl ammonium chloride.

[0071] In some embodiments, a hole transport layer may be provided between the perovskite layer and the second electrode to further improve the hole transport performance of the perovskite solar cell. Specifically, the hole transport layer may include materials such as 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly-3-hexylthiophene (P3HT), triphenylamine with triptycene as the core (H101), 3,4-ethylenedioxythiophene-methoxytriphenylamine (EDOT-OMeTPA), N-(4-phenylamino)carbazole-spirobifluorene (CzPAF-SBF), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and the like.

[0072] The following describes the details in conjunction with specific embodiments.

[0073] Example 1

[0074] A perovskite solar cell comprises, in order: an FTO glass substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a top electrode. The preparation method is as follows:

[0075] 1) FTO glass substrate pretreatment

[0076] The FTO glass was ultrasonically cleaned with glass cleaning solution, deionized water, and ethanol for 15 minutes respectively, then dried with a nitrogen stream and treated with UV-O3 for 20 minutes.

[0077] 2) Preparation of electron transport layer

[0078] The pretreated FTO glass substrate was placed in a culture dish: 40 mM titanium tetrachloride aqueous solution was added, and the dish was placed in a 70° C. oven for 1 hour to obtain a dense titanium dioxide layer with a thickness of 40 nm.

[0079] The substrate with the compact TiO2 layer prepared above was rinsed with water and dried, and a TiO2 slurry (TiO2 particle size about 30 nm) was diluted with anhydrous alcohol at a mass ratio of 7:1, stirred for 12 hours to form a stable suspension; the suspension was coated on the substrate at an initial rotation speed of 5000 revolutions per second (r / s) and an acceleration of 1000 r / s, and the spin coating time was 30 seconds, and then the substrate was annealed at 500°C for half an hour to obtain a porous TiO2 layer with a thickness of 200 nm.

[0080] Then the substrate was placed in a culture dish, 20 mM titanium tetrachloride solution was added, and the substrate was incubated in a 70°C oven for 30 minutes. After washing with water and drying, an aqueous lithium carbonate solution (concentration 2 mg / mL) was spin-coated on the substrate at a rotation speed of 3000 r / s for 30 seconds, and the substrate was annealed at 450°C for half an hour to obtain the final electron transport layer.

[0081] 3) Perovskite layer preparation

[0082] 3.1 Lead nitrate film: First, prepare an aqueous lead nitrate solution; add lead nitrate to 1 mL of water, stir to dissolve, and then filter to obtain an aqueous lead nitrate solution with a concentration of 1.5 M; spin-coat the aqueous lead nitrate solution on the electron transport layer, control the environmental humidity and temperature during the process, and perform dynamic spin-coating of the aqueous lead nitrate solution at 5000 r / s under low humidity conditions (RH = 5%, temperature = 15°C), and then bake at 100°C for 30 minutes to obtain a transparent white lead nitrate film with a thickness of about 350 nm.

[0083] 3.2 Water-based perovskite conversion: First, convert the lead nitrate film to an MA-based perovskite using multiple soaking. Specifically, add ethylammonium chloride to a methyl halide amine solution (containing MAI and MACI, molar ratio MAI:MACI = 4:1, solvent IPA, total concentration of methyl halide amine 10 mg / mL); then, add ethylammonium chloride to the methyl halide amine solution in an amount of 1 / 5 of the total molar amount of methyl halide amine; then, immerse the lead nitrate film substrate in the methyl halide amine solution with added ethylammonium chloride for 4 minutes, rinse with IPA, dry with nitrogen, and then immerse again, repeating this process four times to obtain an MA-based perovskite. Subsequently, prepare a solution containing a high-concentration formamidinium halide salt (containing FAI 155 mg, MAI 15 mg, and MACI 20 mg in 3.2 mL of IPA), and spin-coat the solution containing FAI (about 200 μL) on the surface of the MA-based perovskite at 3000 r / s, and then anneal at 150°C for 15 minutes (RH about 30-40%) to obtain a perovskite film with a thickness of 500 nm.

[0084] Spin-coating of passivation agent: spin-coat a passivation agent solution (passivation agent PEAI, solvent IPA, passivation agent concentration 5 mg / mL) on the surface of the perovskite film at 5000 r / s, and then dry the solvent.

[0085] 4) Preparation of hole transport layer

[0086] 72.3 mg of Spiro-OMeTAD, 28.6 μL of 4-tert-butylpyridine, and 18.6 μL of Li-TFSI acetonitrile solution (concentration of 520 mg / mL) were added to 1 mL of chlorobenzene, stirred for 12 hours, and then spin-coated on the perovskite surface at a speed of 5000 r / s for 30 seconds to obtain a hole transport layer with a thickness of about 200 nm.

[0087] 5) Top electrode preparation

[0088] The gold electrode is evaporated to a thickness of about 80nm.

[0089] Example 2

[0090] A perovskite solar cell and a preparation method thereof, which differs from Example 1 in that: in the preparation of the perovskite layer, the linear alkyl ammonium halide added to the methyl ammonium halide solution is propyl ammonium chloride, and all other aspects are the same as Example 1.

[0091] Example 3

[0092] A perovskite solar cell and a preparation method thereof, which differs from Example 1 in that: in the preparation of the perovskite layer, the linear alkyl ammonium halide added to the methyl ammonium halide solution is butyl ammonium chloride, and all other aspects are the same as Example 1.

[0093] Comparative Example 1

[0094] A perovskite solar cell comprises, in order: an FTO glass substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a top electrode. The preparation method differs from that of Example 1 in that, during the preparation of the perovskite layer, no linear alkylammonium halide, ethylammonium chloride, is added to the methylammonium halide solution; otherwise, the preparation method is the same as that of Example 1.

[0095] Performance Testing

[0096] like Figure 1 The XRD data of the perovskite films of the various examples and comparative examples show that in Examples 1-3, the introduction of ethylammonium chloride, propylammonium chloride or butylammonium chloride in the methylammonium halide solution was proven to increase the intensity of the final aqueous perovskite (100) diffraction peak and reduce its half-height width, confirming that the use of the above-mentioned linear alkyl ammonium halide can effectively improve the crystallinity of the perovskite, among which propylammonium chloride (PACl) in Example 2 has the best effect.

[0097] like Figure 2Scanning electron microscopy (SEM) images show that the initial perovskite morphology in Comparative Example 1 exhibits small grain size, while the addition of the linear alkyl ammonium halide in Examples 1-3 results in larger grains and a more uniform size distribution. The introduction of the linear alkyl ammonium halide significantly promotes perovskite grain growth, resulting in high-quality perovskite films with a low density of grain boundary defects.

[0098] In addition, the results of testing the photovoltaic efficiency of perovskite solar cell devices show that the introduction of linear alkyl ammonium halides of Examples 1-3 can improve the photoelectric conversion efficiency of aqueous perovskite solar cell devices, among which Example 2 has the best effect. Figure 3 As shown, the content of the carbon dioxide in Comparative Example 1 can be increased from 20.78% in Comparative Example 1 to 23.88% in Example 2.

[0099] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing a perovskite film, characterized in that: include: preparing a divalent inorganic salt aqueous solution, wherein the divalent inorganic salt in the divalent inorganic salt aqueous solution is an inorganic salt corresponding to the divalent cation of the perovskite; subjecting the divalent inorganic salt aqueous solution to a film-forming treatment to obtain a divalent inorganic salt film; The divalent inorganic salt film is immersed in a methylammonium halide solution, and after drying, coated with a solution containing a formamidine halide salt and annealed to obtain a perovskite film containing an organic-inorganic hybrid perovskite; The methylammonium halide solution contains linear alkylammonium halide with 2 to 5 carbon atoms, and during the annealing process, the linear alkylammonium halide decomposes into alkylamine with a higher boiling point than methylamine.

2. The preparation method according to claim 1, wherein The linear alkyl ammonium halide includes at least one of ethylammonium chloride, propylammonium chloride and butylammonium chloride.

3. The preparation method according to claim 1, wherein The molar ratio of the methylammonium halide to the linear alkylammonium halide in the methylammonium halide solution is (5-6):1; And / or the concentration of methylammonium halide in the methylammonium halide solution is 8-12 mg / mL.

4. The preparation method according to claim 1, wherein The methylammonium halide in the methylammonium halide solution includes methylammonium iodide and methylammonium chloride in a molar ratio of (3.5-4.5):1; And / or, the solution containing formamidine halide salt contains formamidine iodide and methylammonium iodide dissolved in a molar ratio of (7-10):

1.

5. The preparation method according to claim 1, wherein The soaking treatment includes the following steps multiple times: soaking for 4 to 5 minutes and then drying with nitrogen; And / or, the annealing temperature is 140-160°C.

6. The preparation method according to any one of claims 1 to 5, characterized in that The solvent in the methylammonium halide solution is an alcohol solvent, and the solvent in the solution containing formamidine halide salt is an alcohol solvent.

7. The preparation method according to any one of claims 1 to 5, characterized in that In the divalent inorganic salt aqueous solution, the concentration of the divalent inorganic salt is 1.0-2.0 mol / L; And / or, the divalent inorganic salt includes at least one of nitrate and acetate corresponding to the divalent cation of the perovskite.

8. The preparation method according to any one of claims 1 to 5, wherein The step of forming a film with the divalent inorganic salt aqueous solution comprises: coating the divalent inorganic salt aqueous solution to form a film under the conditions of relative humidity <10% and temperature <20°C, and then performing a drying treatment.

9. A perovskite film, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. A perovskite solar cell, characterized in that: Comprising the perovskite film according to claim 9.

Images