阅读说明：本技术 一种高质量卤化物钙钛矿薄膜的制备方法 (Preparation method of high-quality halide perovskite film ) 是由 韩宏伟 梅安意 刘爽 张德义 李代宇 于 2021-08-19 设计创作，主要内容包括：本发明公开了一种高质量卤化物钙钛矿薄膜的制备方法,属于卤化物钙钛矿半导体技术领域。本发明通过调控卤化物钙钛矿前驱体,在基底上涂敷卤化物钙钛矿前驱体湿膜,在密闭空间中调控前驱体湿膜中溶剂的挥发过程,从而控制前驱体湿膜的饱和度,抑制均匀成核,促进钙钛矿晶粒的充分生长,实现高质量钙钛矿薄膜的制备。通过本方法,实现了形核少、生长充分、晶界少的高质量卤化物钙钛矿薄膜的可控制备,为高性能卤化物钙钛矿光电子器件的制备提供有力支撑。(The invention discloses a preparation method of a high-quality halide perovskite thin film, and belongs to the technical field of halide perovskite semiconductors. According to the invention, the halide perovskite precursor is regulated, the halide perovskite precursor wet film is coated on the substrate, and the volatilization process of the solvent in the precursor wet film is regulated and controlled in a closed space, so that the saturation of the precursor wet film is controlled, uniform nucleation is inhibited, the full growth of perovskite crystal grains is promoted, and the preparation of the high-quality perovskite film is realized. By the method, the controllable preparation of the high-quality halide perovskite thin film with less nucleation, sufficient growth and less crystal boundary is realized, and powerful support is provided for the preparation of high-performance halide perovskite optoelectronic devices.)

1. A method for preparing a halide perovskite thin film is characterized by comprising the following steps:

(1) adding a positive monovalent salt and a positive divalent metal salt into a solvent to obtain a perovskite precursor; the positive monovalent salt and the positive divalent metal salt are both halogen salts or pseudohalogen salts;

(2) coating the perovskite precursor obtained in the step (1) on a substrate to obtain a precursor wet film;

(3) the method controls the saturation degree of the precursor wet film by regulating the volatilization process of the solvent in the precursor wet film so as to inhibit uniform nucleation, promote the full growth of perovskite crystal grains and prepare the halide perovskite thin film with the full growth of the crystal grains.

2. The method for preparing a halide perovskite thin film according to claim 1, wherein the step (3) of regulating the volatilization process of the solvent in the precursor wet film is specifically as follows: placing the precursor wet film in a closed space for heating, volatilizing a solvent in the precursor wet film to fill the closed space, and adjusting the heating temperature and the volume of the closed space so that the concentration of the perovskite in the wet film does not reach the uniform nucleation critical supersaturation concentration after the concentration of the solvent vapor in the closed space is saturated; then the solvent vapor in the closed space diffuses to the external space from the exhaust port, and the size of the exhaust port is regulated, so that the speed of the solvent vapor diffusing to the external space is regulated, in the process of increasing the supersaturation degree in the wet film, random nucleation starts to occur and gradually grows, the supersaturation degree in the wet film is reduced in the process of nucleation and grain growth, the saturation degree caused by solvent volatilization is increased, the supersaturation degree in the wet film is balanced, the uniform nucleation supersaturation concentration point is prevented from being reached, the sufficient growth of crystal nuclei is ensured, and the halide perovskite thin film with fully grown crystal grains is prepared.

3. The method for preparing a halide perovskite thin film according to claim 1, wherein the step (3) of regulating the volatilization process of the solvent in the precursor wet film is specifically as follows: placing the precursor wet film in a space with an air vent and an air vent for heating, and introducing a mixed gas of carrier gas and solvent vapor in the perovskite precursor into the space, so that the partial pressure of the solvent vapor in the mixed gas is greater than the saturated vapor pressure of the solvent in the wet film at the current temperature, and the solvent in the wet film does not volatilize; and then, raising the heating temperature in the space or reducing the partial pressure of the solvent vapor in the mixed gas to ensure that the partial pressure of the solvent vapor in the mixed gas is lower than the saturated vapor pressure of the solvent at the current heating temperature, so that the solvent in the wet film volatilizes, the perovskite gradually reaches saturation, and random nucleation occurs.

4. The method of producing a halide perovskite thin film as claimed in claim 1, wherein the monovalent salt is a monovalent organic salt or an alkali metal salt.

5. The method for producing a halide perovskite thin film as claimed in claim 4, wherein the monovalent organic salt is a salt of a monovalent organic cation with a halogen ion or a pseudohalogen ion; the alkali metal salt is a salt formed by cesium ions and halogen ions or pseudohalogen ions; the positive divalent metal salt is a salt formed by positive divalent metal cations and halogen ions or pseudohalogen ions.

6. The method of making a halide perovskite thin film of claim 5, wherein the positive monovalent organic cation is CH₃NH₃ ⁺、CH(NH₂)₂ ⁺、CH₃NH₂OH⁺、(CH₃)₂NHOH⁺、C(NH₂)₃ ⁺、(CH₃)₂NH₂ ⁺、NH₂CH₂NH₃ ⁺Or, CH₃C(NH₂)₂ ⁺(ii) a The positive divalent cation is Pb²⁺、Sn²⁺、Ge²⁺Or Cu²⁺(ii) a The halide ion is F^-、Cl^-、Br^-Or I^-The pseudohalogen ion is CN^-Or SCN^-。

7. The method for producing a halide perovskite thin film as claimed in any one of claims 1 to 3, wherein the solvent is nitrogen-methylformamide.

8. A method of producing a halide perovskite thin film as claimed in any one of claims 1 to 3, wherein the step (1) further comprises a solubilization treatment, in particular physical means of heating, stirring or ultrasound, or chemical means of introducing a solubilizing agent, after the addition of the monovalent and divalent metal salts to the solvent.

9. The method for producing a halide perovskite thin film as claimed in any one of claims 1 to 3, wherein the coating is spin coating, blade coating, drop coating, slit coating, print coating or ink jet coating.

10. The method for producing a halide perovskite thin film as claimed in any one of claims 1 to 3, wherein the substrate is a planar substrate or a porous substrate deposited with a porous film.

Technical Field

The invention belongs to the field of halide perovskite semiconductors, and particularly relates to a preparation method of a high-quality halide perovskite thin film.

Background

Since the twentieth century, the rapid development of human society has been promoted by the progress of semiconductor science and technology. The system comprises a semiconductor-based computer technology, an intelligent sensing technology, a communication technology, a laser technology, a light-emitting and displaying technology, a solar cell new energy technology and the like, and brings great convenience to industrial production and daily life. Semiconductor materials are the basis of the development of semiconductor technology, and researchers have been working on the development of new semiconductor materials. Elemental semiconductors such as silicon and germanium have been studied most extensively for the first time, and silicon is also the most widely used semiconductor material at present. The use of silicon semiconductors in the fields of chips and solar cells is well known, but the high energy consumption during processing of high quality crystalline silicon brings with it a high cost. Gallium arsenide semiconductors, in addition to silicon, are another well known class of semiconductor materials. The material has excellent semiconductor performance, but the material cost is high. With the efforts of researchers, metal halide perovskite semiconductor materials having properties comparable to those of silicon and gallium arsenide have been discovered and are receiving much attention.

The metal halide perovskite material is generally provided with ABX₃The structural general formula is shown in the specification, wherein A is monovalent cation, B is divalent cation, and X is halogen anion. The material has excellent semiconductor properties of adjustable components and band gaps, high carrier mobility, long carrier service life, low exciton binding energy, strong light absorption capacity and the like. In addition, the halide perovskite raw material has wide sources and can be prepared by using a low-cost solution processing technology, so that the halide perovskite raw material has the remarkable advantage of low cost. At present, halide perovskites have been studied for applications in the fields of solar cells, light emitting diodes, photodetectors, lasers, etc., and exhibit excellent properties. Among the various applications, halide perovskite-based solar cell technology has developed most rapidly. The photoelectric conversion efficiency of the perovskite solar cell is broken through to 25.5 percent, is close to the photoelectric conversion efficiency of a silicon solar cell, can obviously reduce the production cost of the solar cell, and is expected to realize the price flattening and even the cheapness of the photovoltaic power generation rate. The rapid development of the perovskite solar cell technology is expected to become a revolutionary technology, and powerful support is provided for clean and sustainable energy.

Good morphology is the basis for ensuring excellent performance of semiconductor materials, and halide perovskite semiconductors are no exception. In various devices based on halide perovskite semiconductors, especially in solar cells, a great deal of research work is being carried out around optimizing morphology control of halide perovskite thin films. Currently, the most widely used topography control strategies include rapid solvent removal and continuous deposition. Typical methods of the rapid solvent removal strategy include an anti-solvent method, a thermal coating method, an air blowing method and a vacuum pumping method, and the core idea of the methods is to rapidly remove the solvent in the perovskite precursor, so that the solute can reach supersaturation in a short time, uniform nucleation is induced, a large number of crystal nuclei are generated in a short time, and a uniform perovskite thin film is obtained. In the continuous deposition strategy, a divalent metal salt, such as lead iodide, is deposited and then placed in an atmosphere of a monovalent salt, such as methylamine iodide, to react with the divalent salt to form a perovskite. Whether a rapid solvent removal strategy or a continuous deposition strategy, the crystallization of the perovskite is generally substantially completed in a short time, e.g., several minutes, with a large number of nuclei and less nuclei growing, resulting in a perovskite thin film with smaller grain sizes, typically from several hundred nanometers to several microns, and grain boundaries between the grains that are detrimental to device performance. In order to further prepare perovskite thin films with large-size crystal grains and reduce grain boundaries, a space-limited inverse temperature growth process is developed to prepare high-quality perovskite thin films. In the method, a perovskite solution is placed between two substrates and heated at a high temperature, and the inverse temperature dissolution characteristic of perovskite is utilized to realize the full growth of perovskite crystal nucleus. The method has the disadvantages that after the crystal growth is finished, the prepared perovskite film is in a liquid phase precursor, and effective cleaning is needed to ensure the crystal quality, so that the application of the perovskite film is limited. Therefore, it is of great significance to develop more effective technology to realize the controllable preparation of high-quality perovskite thin film.

Disclosure of Invention

Aiming at the defects or improvement requirements in the prior art, the invention provides a preparation method of a high-quality perovskite thin film, which controls the saturation degree of a precursor wet film, inhibits uniform nucleation, promotes the full growth of perovskite grains and realizes the preparation of the high-quality perovskite thin film by regulating and controlling the volatilization process of a solvent in the precursor wet film. By the method, the controllable preparation of the high-quality halide perovskite thin film with less nucleation, sufficient growth, high crystallinity and less crystal boundary is realized, so that the performance of the halide perovskite semiconductor photoelectronic device is promoted, and the technical problems of more nucleation, insufficient growth and more crystal boundary of the perovskite thin film in the prior art are solved.

In order to achieve the above object, the present invention provides a method for preparing a halide perovskite thin film, comprising the steps of:

(1) adding a positive monovalent salt and a positive divalent metal salt into a solvent to obtain a perovskite precursor; the positive monovalent salt and the positive divalent metal salt are both halogen salts or pseudohalogen salts;

(2) coating the perovskite precursor obtained in the step (1) on a substrate to obtain a precursor wet film;

(3) the method controls the saturation degree of the precursor wet film by regulating the volatilization process of the solvent in the precursor wet film so as to inhibit uniform nucleation, promote the full growth of perovskite crystal grains and prepare the halide perovskite thin film with the full growth of the crystal grains.

Preferably, the step (3) of regulating and controlling the volatilization process of the solvent in the precursor wet film specifically comprises the following steps: placing the precursor wet film in a closed space for heating, volatilizing a solvent in the precursor wet film to fill the closed space, and adjusting the heating temperature and the volume of the closed space so that the concentration of the perovskite in the wet film does not reach the uniform nucleation critical supersaturation concentration after the concentration of the solvent vapor in the closed space is saturated; then the solvent vapor in the closed space diffuses to the external space from the exhaust port, and the size of the exhaust port is regulated, so that the speed of the solvent vapor diffusing to the external space is regulated, in the process of increasing the supersaturation degree in the wet film, random nucleation starts to occur and gradually grows, the supersaturation degree in the wet film is reduced in the process of nucleation and grain growth, the saturation degree caused by solvent volatilization is increased, the supersaturation degree in the wet film is balanced, the uniform nucleation supersaturation concentration point is prevented from being reached, the sufficient growth of crystal nuclei is ensured, and the halide perovskite thin film with fully grown crystal grains is prepared.

Preferably, the step (3) of regulating and controlling the volatilization process of the solvent in the precursor wet film specifically comprises the following steps: placing the precursor wet film in a space with an air vent and an air vent for heating, and introducing a mixed gas of carrier gas and solvent vapor in the perovskite precursor into the space, so that the partial pressure of the solvent vapor in the mixed gas is greater than the saturated vapor pressure of the solvent in the wet film at the current temperature, and the solvent in the wet film does not volatilize; and then, raising the heating temperature in the space or reducing the partial pressure of the solvent vapor in the mixed gas to ensure that the partial pressure of the solvent vapor in the mixed gas is lower than the saturated vapor pressure of the solvent at the current heating temperature, so that the solvent in the wet film volatilizes, the perovskite gradually reaches saturation, and random nucleation occurs.

Preferably, the monovalent salt is an organic salt or an alkali metal salt.

Preferably, the monovalent organic salt is a salt of a monovalent organic cation with a halogen ion or pseudohalogen ion; the alkali metal salt is a salt formed by cesium ions and halogen ions or pseudohalogen ions; the positive divalent metal salt is a salt formed by positive divalent metal cations and halogen ions or pseudohalogen ions.

Preferably, the monovalent organic cation is CH₃NH₃ ⁺、CH(NH₂)₂ ⁺、CH₃NH₂OH⁺、 (CH₃)₂NHOH⁺、C(NH₂)₃ ⁺、(CH₃)₂NH₂ ⁺、NH₂CH₂NH₃ ⁺Or, CH₃C(NH₂)₂ ⁺(ii) a The positive divalent cation is Pb²⁺、Sn²⁺、Ge²⁺Or Cu²⁺(ii) a The halide ion is F^-、Cl^-、Br^-Or I^-The pseudohalogen ion is CN^-Or SCN^-。

Preferably, the solvent is N-methylformamide.

Preferably, the step (1) further comprises a solubilization treatment, specifically a physical means of heating, stirring or ultrasound, or a chemical means of introducing a solubilizing agent, after the n-monovalent salt and the n-divalent metal salt are added into the solvent.

Preferably, the coating is spin coating, knife coating, drop coating, slot coating, print coating or ink jet coating.

Preferably, the substrate is a planar substrate or a porous substrate deposited with a porous membrane.

Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

(1) the invention provides a preparation method of a high-quality halide perovskite thin film, which is characterized in that the core of the preparation method comprises the steps of preparing a precursor which is well dissolved, controlling the removal process of solvent molecules in a precursor wet film, inhibiting the occurrence of uniform nucleation in the crystallization process and promoting the full growth of non-uniform crystal nuclei.

(2) Compared with the rapid mass nucleation and the limited growth in the processes of rapid solvent removal, continuous deposition and the like which are mainstream at present, the perovskite thin film growth in the method is a process with less nucleation and sufficient growth, so that the high-crystallinity perovskite thin film with larger-size grains and less crystal boundaries can be obtained; compared with the preparation method of the perovskite thin film with space limited inverse temperature growth reported at present, the method provided by the invention has the advantages that the solvent in the wet film is removed when the perovskite thin film is generated, the dry film is directly obtained, and the operation is simpler.

(3) The invention preferably realizes the preparation of the precursor with high solubility by using the nitrogen-methyl formamide solvent, and realizes the preparation of the high-quality halide perovskite thin film by controlling the volatilization and removal of solvent molecules in the perovskite precursor wet film in a closed space.

Drawings

FIG. 1 is a control scheme of the halide perovskite thin film preparation method provided by the present invention.

FIG. 2 is a graph showing the variation of the crystallization process of the halide perovskite thin film prepared in example 1 of the present invention and the results of synchrotron radiation X-ray diffraction of the perovskite thin film prepared.

FIG. 3 is an X-ray diffraction pattern of a halide perovskite thin film prepared in example 2 of the present invention.

FIG. 4 shows another control mode of the preparation method of the halide perovskite thin film provided by the invention.

FIG. 5 is an X-ray diffraction pattern of a halide perovskite thin film prepared in example 3 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a preparation method of a high-quality halide perovskite thin film, which comprises the key steps of regulating and controlling a halide perovskite precursor, coating a halide perovskite precursor wet film on a substrate, and regulating and controlling the volatilization process of a solvent in the precursor wet film, thereby controlling the saturation of the precursor wet film, inhibiting uniform nucleation, promoting the full growth of perovskite grains, and realizing the preparation of the high-quality perovskite thin film; the precursor regulation comprises regulating and controlling a solvent used by the halide perovskite precursor and solubilization treatment; a solvent for dissolving a halide perovskite solute towards true solution, selected from the group consisting of nitrogen-methylformamide; the solubilization treatment is used for further promoting the dissolution of the halide perovskite into a true solution in the solvent, and comprises heating, stirring, ultrasonic treatment and additive introduction; the wet film coating is realized by spin coating, blade coating, drop coating, slit coating, printing, ink jet and the like; the substrate comprises a planar substrate and a porous substrate deposited with a porous membrane; the volatilization speed of the solvent in the precursor wet film is realized by two ways:

the first method is as follows: placing a wet film in a closed space with an exhaust port for heating, wherein the heating temperature is less than 150 ℃, adjusting the heating temperature, the volume of the closed space and the air permeability of the exhaust port, ensuring that the solvent in the precursor wet film is volatilized to fill the closed space so that the concentration of the solvent vapor in the closed space is saturated, the concentration of the perovskite in the wet film does not reach the critical supersaturation concentration of uniform nucleation, then the solvent vapor in the closed space is slowly diffused to an external space from the exhaust port, and regulating and controlling the speed of the solvent vapor diffusing to the external space through the size design of the exhaust port, thereby controlling the further volatilization speed in the wet film, avoiding the rapid increase of the supersaturation in the wet film, wherein in the process of slowly increasing the supersaturation, the non-uniform nucleation starts to occur and gradually grows, the process of nucleation and crystal grain growth leads to the reduction of the supersaturation in the wet film, and the reduction of the saturation is helpful for balancing the increase brought by the slow volatilization of the solvent, thereby balancing the supersaturation degree in the wet film and preventing the wet film from reaching a uniform nucleation supersaturation concentration point, thereby ensuring the full growth of crystal nucleus and realizing the preparation of high-quality perovskite film;

the second method comprises the following steps: placing the wet film in a closed space with an air inlet and an air outlet for heating, wherein the heating temperature is less than 150 ℃, mixing carrier gas such as nitrogen, air and the like and solvent vapor according to a certain partial pressure ratio, and introducing the mixture into the closed space, so as to ensure that the partial pressure of the solvent vapor in the mixed gas is greater than the saturated vapor pressure of the solvent at the current temperature, and the solvent in the wet film does not volatilize; and then, raising the heating temperature of the closed space or reducing the partial pressure of the solvent vapor in the mixed gas to ensure that the partial pressure of the solvent vapor in the mixed gas is slightly lower than the saturated vapor pressure of the solvent at the current heating temperature, slowly volatilizing the solvent in the wet film, gradually saturating the perovskite, and randomly nucleating, wherein in the process of slowly volatilizing the solvent, crystal nuclei gradually grow and are prevented from uniformly nucleating, so that the preparation of the high-quality perovskite thin film is realized.

The halide perovskite comprises ABX₃Halide perovskites and derivatives thereof, said ABX₃The A site in the halide perovskite or the derivative thereof is positive univalent cation selected from methylamine cation CH₃NH₃ ⁺Formamidine cation CH (NH)₂)₂ ⁺Cesium cation Cs⁺Methyl hydroxylamine cation CH₃NH₂OH⁺Dimethyl hydroxylamine, and their preparationIon (CH)₃)₂NHOH⁺Guanidine cation C (NH)₂)₃ ⁺Dimethylamine Cation (CH)₃)₂NH₂ ⁺The methylene diamine cation NH₂CH₂NH₃ ⁺Acetamidine cation CH₃C(NH₂)₂ ⁺One or more of; the B site is a divalent cation selected from Pb²⁺Sn, Sn²⁺Germanium Ge²⁺Copper Cu²⁺One or more of; x is a monovalent anion selected from the group consisting of fluoride F^-Chloride ion Cl^-Bromine ion Br^-Iodine I^-And pseudohalogen ion CN^-、SCN^-One or more of;

to further illustrate the method of preparing a high quality halide perovskite thin film provided by the present invention, the following embodiments are described in detail:

example 1

Weighing 1mmol of lead iodide PbI₂1mmol of methylamine iodide MAI, adding 1mL of nitrogen-methylformamide solvent and 0.15mmol of methylamine chloride MACl additive, and heating and stirring at 50 ℃ for 1h to obtain a perovskite precursor solution; taking conductive glass deposited with compact titanium dioxide, 800nm titanium dioxide porous membrane, 2 μm zirconium oxide porous membrane and 15 μm porous carbon membrane as a substrate, wherein the size of the substrate is 100mm multiplied by 24mm multiplied by 3mm, dripping perovskite precursor solution on the porous membrane substrate, placing the substrate in a closed space, wherein the size of an inner cavity of the closed space is 110mm multiplied by 30mm multiplied by 6mm, the length and the width of an exhaust port of the closed space are respectively 100mm multiplied by 3mm, and the air permeability of the exhaust port is regulated and controlled by covering air permeable adhesive tapes with different meshes on the exhaust port (figure 1); heating at 56 deg.C on a hot bench for 20h to crystallize perovskite in the porous membrane. During the crystallization, the substrate filled with perovskite was observed, and after annealing for 2 hours, 1 crystalline region was observed on the substrate; after 5 hours of annealing, several crystalline regions appeared again; the partially crystallized regions began to join together after annealing for 10 hours; after annealing for 20 hours, the entire observation region was sufficiently crystallized (a in fig. 2). It should be noted that the photographs corresponding to the time points in the figure are not shownThe same film, but the same batch of films, is taken out at different annealing time points for observation, because the crystallization process is interrupted after the film is taken out for observation, and the film is put back into a closed space for annealing, so that good crystallization cannot be obtained. Synchrotron radiation X-ray diffraction characterization of the obtained perovskite, and removal of the porous carbon layer prior to testing in order to exclude the effect of the surface perovskite coating, the test results are shown as b in fig. 2, and it can be seen that the obtained perovskite exhibits a high degree of orientation. In this example, the perovskite is filled in the porous membrane, the pore channel structure in the porous membrane is interconnected in space to form a three-dimensional porous space network structure, after the carbon layer is removed, the perovskite is mainly filled in the porous zirconia and the porous titania layer, the porous titania and the porous zirconia are stacked by nano particles of about 20-30nm, the pore diameter of the formed porous membrane is approximately in similar size, and the pores are random disordered and have no orientation, which means that the perovskite obtained by the conventional crystallization process in the porous membrane does not show the orientation, but the perovskite obtained by the method of the present invention shows a high degree of orientation, which means that the perovskite prepared by the method realizes few nuclei and sufficient growth in the three-dimensional porous space network structure.

Example 2

Weighing 1mmol of lead iodide PbI₂0.8mmol of formamidine iodide FAI, 0.15mmol of methylamine bromide MABr and 0.05mmol of cesium iodide, 1mL of nitrogen-methylformamide and 0.15mmol of formamidine chloride FACL additive are added, and the mixture is stirred for 1 hour at 50 ℃ to prepare a precursor A; weighing 1mmol of lead iodide PbI₂0.8mmol of formamidine iodide FAI, 0.15mmol of methylamine bromide MABr and 0.05mmol of cesium iodide are added, 0.8mL of nitrogen, nitrogen-dimethylformamide DMF, 0.2 mL of dimethyl sulfoxide DMSO and 0.15mmol of formamidine chloride FACL additive are added, and the mixture is stirred for 1 hour at 50 ℃ to prepare a precursor B; weighing 1mmol of lead iodide PbI₂0.8mmol formamidine FAI, 0.15mmol methylamine bromide MABr, 0.05mmol cesium iodide, 1mL of nitrogen, nitrogen-dimethylformamide DMF and 0.15mmol formamidine chloride FACL additive were added thereto, stirred at 50 ℃ for 1 hour,preparing a precursor C; taking conductive glass deposited with compact titanium dioxide, 800nm titanium dioxide porous membrane, 2 μm zirconium oxide porous membrane and 15 μm porous carbon membrane as a substrate, dripping perovskite precursor solution on the porous membrane substrate, placing the substrate in a closed space, wherein the size of an inner cavity of the closed space is 110mm multiplied by 30mm multiplied by 6mm, the length and the width of an exhaust port of the closed space are respectively 100mm multiplied by 3mm, and the air permeability of the exhaust port is regulated and controlled by covering air permeable adhesive tapes with different meshes on the exhaust port; the perovskite is crystallized in the porous membrane by heating on a hot bench at 58 ℃ for 16h, and compared with the obtained perovskite, as shown in fig. 3, the x-ray diffraction pattern of the perovskite is shown, compared with the perovskite prepared on the basis of DMF and DMSO, the perovskite diffraction peak prepared by the precursor based on nitrogen-methyl formamide is stronger, which means high crystallinity, and simultaneously the intensity of the diffraction peak near 40 degrees is remarkably stronger than other diffraction peaks, which is remarkably different from the intensity signal of the diffraction peak of the perovskite thin film prepared by the general method, and means remarkable crystal orientation. The reason is that the solvents are different, the dissolving degree of the precursor is different, so that the nucleation and growth processes are influenced, the nitrogen-methyl formamide solvent has high solubility on the perovskite, the colloidal particles of the obtained precursor are smaller and tend to true solution, and the perovskite prepared by the method disclosed by the invention has better crystallinity.

Example 3

Weighing 1mmol of lead iodide PbI₂1mmol of methylamine iodide MAI, adding 1mL of nitrogen-methylformamide solvent and 0.15mmol of methylamine chloride MACl additive, heating and stirring at 50 ℃ for 1h to obtain a perovskite precursor solution, scraping the obtained precursor on a glass substrate, and placing the substrate in a closed space; as shown in fig. 4, nitrogen gas is introduced into a gas washing bottle containing a nitrogen-methylformamide solvent, the gas washing bottle is heated at 55 ℃ to fully mix the nitrogen gas with the nitrogen-methylformamide vapor, the mixed gas is introduced into a closed space to fully ventilate the closed space, the closed space is fully filled with the mixed gas, and the closed space is heated to 56 ℃ and kept for 10 hours, so that the crystallization of the perovskite is completed; for the control sample, nitrogen-methyl formamide solvent was not placed in the gas washing bottle, only nitrogen gas was introduced into the sealed space, and the sealed space was heated to 56 deg.C and maintained10 hours; as shown in fig. 5, comparing the x-ray diffraction results of the two samples, it is found that the derived peak intensity of the sample introduced with the mixed gas is significantly stronger than that of the sample introduced with nitrogen, and the difference between the two samples is that the volatilization of solvent molecules in a wet film in a closed space introduced with the mixed gas is regulated and controlled by the vapor pressure of the solvent in the mixed gas, so that the occurrence of rapid supersaturation and uniform nucleation is avoided.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.