Fluorine-containing polymer regulated and controlled mixed halogen perovskite thin film and preparation method and application thereof

Abstract

The invention relates to the technical field of mixed halogen perovskite thin films, in particular to a fluorine-containing polymer regulated mixed halogen perovskite thin film and a preparation method and application thereof, and the preparation method comprises the following steps: weighing a perovskite precursor according to a proportion, dissolving the perovskite precursor in a first solvent to form a mixed solvent, and adding an amino acid ligand to form a perovskite precursor solution; adding a fluorine-containing polymer with a first mass concentration to obtain a fluorine-containing polymer perovskite precursor solution; the preparation method comprises the following steps: carrying out film forming treatment on a substrate to form a liquid film, carrying out time-sharing annealing treatment to enable the liquid film to form a micron-sized split-phase region under the initiation of a fluorine-containing polymer, carrying out liquid-liquid separation, and cooling to obtain the fluorine-containing polymer regulated and controlled mixed halogen perovskite thin film. The liquid-liquid phase separation process in the perovskite film is initiated in situ through the fluorine-containing polymer, so that halogen ions in the film are uniformly distributed, the lattice stress in the perovskite crystallization process is reduced, and the quality of the mixed halogen perovskite film is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mixed halogen perovskite thin films, and in particular to a mixed halogen perovskite thin film regulated by a fluorine-containing polymer, and a preparation method and application thereof. Background Art

[0002] Solution-processable metal halide perovskite films are ideal light-emitting layer materials for the preparation of next-generation high-efficiency and stable light-emitting diodes (PeLEDs) due to their advantages such as high color purity, wide color gamut, and low cost. In the metal halide three-dimensional perovskite ABX3 structure, Cs occupies the A position. + 、HC(NH2)2 + (FA + ) and CH3NH3 + (MA + ) etc. The B-site ion is usually a divalent lead metal ion. The X-site is usually composed of a halogen (Cl - Br − and I − By adjusting the type of mixed halogen, the spectrum can be adjusted from blue light to near-infrared light, and the spectrum half-width of mixed halogen perovskite is narrow and the luminescent color purity is high.

[0003] However, when halide perovskites are prepared by solution methods, the perovskite crystallizes from the precursor solution too quickly and the crystallization process is difficult to control. This results in numerous defects within the solution-prepared perovskites. Mixed halide perovskites, in particular, experience significant lattice stress during crystallization due to the varying halide ion composition. This leads to the presence of numerous Ruddlesden-Popper (RP)-type high-dimensional planar defects within the mixed halide perovskite. The presence of these planar defects can lead to defects at the perovskite band edge, which in turn affects the perovskite's luminescence properties. Summary of the Invention

[0004] In order to solve at least one of the above technical problems, the present invention proposes a mixed halogen perovskite film regulated by a fluorine-containing polymer and a preparation method thereof. By introducing fluorine-containing polymers of different molecular weights into the mixed halogen perovskite precursor solution, during the low-temperature annealing process, the fluorine-containing polymer in situ triggers the liquid-liquid phase separation process inside the perovskite film, so that the halogen ions inside the film are evenly distributed, the lattice stress of the perovskite crystallization process is reduced, and the quality of the mixed halogen perovskite film is improved, thereby achieving the optimization of the performance of the perovskite LED device.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides a method for preparing a mixed halide perovskite film regulated by a fluorine-containing polymer, comprising the following steps: S1, weighing a perovskite precursor according to a ratio, dissolving it in a first solvent to form a mixed solvent, adding an amino acid ligand for guiding the perovskite orientation crystallization process to the mixed solvent, heating and stirring to form a uniform and clear perovskite precursor solution; S2, adding a fluorine-containing polymer of a first mass concentration to the perovskite precursor solution to obtain a fluorine-containing polymer perovskite precursor solution; S3, a fluorine-containing polymer perovskite precursor solution is subjected to a film-forming treatment on a substrate to form a liquid film, and then subjected to a time-sharing annealing treatment so that the liquid film forms a micron-scale phase separation region under the initiation of the fluorine-containing polymer, and liquid-liquid separation occurs. After cooling, a mixed halogen perovskite film regulated by the fluorine-containing polymer is obtained.

[0006] Preferably, the general formula of the perovskite in S1 is ABX3; wherein the A-site ion is one or more of cesium ion, formamidine ion and methylamine ion; the B-site ion is lead ion and / or tin ion; the X-site ion is one or more of chloride ion, bromide ion and iodide ion; the amino acid ligand is one or more of amino acids such as glycine, serine, arginine, histidine, cysteine and methionine; and the first solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone.

[0007] Preferably, the molar mass ratio of the amino acid ligand to the perovskite precursor is (0.05-0.2):1, calculated based on the molar amount of the B-site ion in the perovskite precursor.

[0008] Preferably, the fluorine-containing polymer includes one or more of polyperfluoroethylene propylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, fluorine-containing polyimide, fluorine-containing polyurethane, amorphous fluorine polymer, and perfluoropolyether, and the molecular weight of the fluorine-containing polymer ranges from 0.6W to 100W.

[0009] Preferably, the mass ratio of the fluorine-containing polymer to the perovskite precursor, calculated based on the total mass of the perovskite precursor components, is (0.02-0.06):1.

[0010] Preferably, the film forming process includes one or more of spin coating, blade coating and drop coating.

[0011] Preferably, the time-sharing annealing includes low-temperature annealing and high-temperature annealing. The low-temperature annealing temperature is 40-100° C. and the low-temperature annealing time is 1-20 minutes; the high-temperature annealing temperature is 100-130° C. and the high-temperature annealing time is 1-200 minutes.

[0012] The second aspect of the present invention provides a film prepared by the method for preparing a mixed halide perovskite film regulated by a fluorine-containing polymer as described in the first aspect.

[0013] A third aspect of the present invention provides a use of the thin film according to the second aspect in a semiconductor light-emitting material or a photovoltaic device.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces fluoropolymers of varying molecular weights into a mixed halide perovskite precursor solution. The high electronegativity (4.0) of the fluorine atoms in the fluoropolymers creates strong polar sites within the polymer chains. This electrostatic anchoring effect stabilizes the perovskite nuclei and inhibits disordered growth during the initial crystallization phase. Furthermore, the fluorinated side chains (such as -CF3 and -CF2-) impart low surface energy to the polymers, allowing them to spontaneously migrate toward the air-liquid interface in solution, forming a dynamic self-assembled layer. This property enables the polymers to continuously regulate the surface tension of the perovskite precursor solution during film formation, promoting uniform lateral growth of perovskite grains. The polar CF bonds in the fluoropolymer network strongly interact with the polar solvent in the perovskite precursor, facilitating the retention of the polar solvent within the perovskite mesophase during time-sharing annealing, resulting in uniform diffusion of ionic components throughout the film. At the same time, the polymer matrix ultimately exists at the grain boundaries of the perovskite film, which can confine the growth of perovskite grains and improve the film forming properties, ultimately obtaining a perovskite film with uniform perovskite grain size and no pinholes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a flow chart of a method for preparing a mixed halide perovskite film regulated by a fluorine-containing polymer.

[0016] Figure 2 This is an analysis diagram of the crystallization of the perovskite film in the present invention. Figure 2 a is CsPbI with PVDF of different molecular weights added 3-x Br x X-ray diffraction pattern of the film after annealing at 90 °C for 10 min; Figure 2 b is the X-ray diffraction pattern of the perovskite film annealed at 120 °C for 5 minutes.

[0017] Figure 3 The mixed halogen CsPbI in the present invention 3-x Br x Characterization diagram of the liquid-liquid phase separation process of the film. Figure 3 a, Figure 3 c, Figure 3 e, Atomic force microscopy images of perovskite films with different molecular weights of PVDF added after annealing at 90°C for 5 minutes. Figure 3 b, Figure 3 d, Figure 3f are atomic force microscopy images of perovskite films with different molecular weights of PVDF added after annealing at 90°C for 10 minutes.

[0018] Figure 4 CsPbI without PVDF added in the present invention 3-x Br x Thin film phase and morphology analysis. Figure 4 a is CsPbI without PVDF added 3-x Br x X-ray diffraction patterns of the films after annealing at 90 °C for 10 min. Figure 4 b is the X-ray diffraction pattern of the perovskite film without PVDF added and annealed at 120°C for 5 minutes. Figure 4 c- Figure 4 e are atomic force microscopy images of the perovskite film without PVDF added after annealing at 90°C for 2 minutes, 90°C for 5 minutes, and 90°C for 10 minutes.

[0019] Figure 5 The present invention adds mixed halogen CsPbI with different molecular weight PVDF 3-x Br x Atomic force microscope images and particle size statistics. Figure 5 a is an atomic force microscope image of the perovskite film with 40W PVDF added; Figure 5 b is the particle size statistics of the perovskite film with 40W PVDF added; Figure 5 c is the atomic force microscopy of the perovskite film with 53W PVDF added; Figure 5 d is the particle size statistics of the perovskite film with 53W PVDF added.

[0020] Figure 6 The present invention adds mixed halogen CsPbI with different molecular weight PVDF 3-x Br x -LED device performance diagram. Among them, Figure 6 a is the curve of the current density of the LED device changing with voltage. Figure 6 b is the performance curve of LED device brightness changing with voltage. Figure 6 c is the curve of the external quantum efficiency of the LED device changing with voltage.

[0021] Figure 7 CsPbI with only PVDF added 3-x Br x Thin film phase and morphology analysis, including: Figure 7 a is CsPbI with only PVDF added 3-x Br x X-ray diffraction patterns of the films after annealing. Figure 7 b and Figure 7 c is the atomic force micrograph of the perovskite film with only PVDF added at 90°C after annealing for 5 minutes and 10 minutes. Figure 7 d is the transmission electron microscopy image of the perovskite film with only PVDF added. Figure 7 e and Figure 7 f is the characterization of the internal surface defects of the lattice of the perovskite film with only PVDF added.

[0022] Figure 8 CsPbI with amino acid and PVDF additives without time-sharing annealing 3-x Br x Thin film phase and morphology analysis. Figure 8 a is CsPbI without time-sharing annealing 3-x Br x X-ray diffraction patterns of the films after annealing. Figure 8 b and Figure 8 c is CsPbI without time-sharing annealing 3-x Br x Atomic force microscopy images of the films after annealing at 110°C for 5 and 10 minutes. Figure 8 d is CsPbI without time-sharing annealing 3-x Br x Transmission electron microscopy image of the film. Figure 8 e and Figure 8 f is CsPbI without time-sharing annealing 3-x Br x Characterization of surface defects within the lattice of thin films.

[0023] Figure 9 CsPbI with only amino acids added after time-sharing annealing 3-x Br x Thin film phase and morphology analysis. Figure 9 a and Figure 9 b is CsPbI with only amino acids added 3-x Br x X-ray diffraction patterns of films after annealing at 90°C and 120°C. Figure 9 c- Figure 9 e is CsPbI with only amino acids added 3-x Br x Atomic force micrographs of the films after annealing at 90°C for 2, 5, and 10 minutes. Figure 9 f is CsPbI without time-sharing annealing 3-x Br x Transmission electron microscopy image of the film. Figure 9 g and Figure 9 h is CsPbI without time-sharing annealing 3-x Br x Characterization of surface defects within the lattice of thin films.

[0024] Figure 10 Initiating mixed-halogen CsPbI for uneven halogen distribution 3-x Br x Schematic diagram of surface defects within perovskite crystal. Figure 10 a is atomically resolved CsPbI 3-x Br x Spherical aberration electron microscope image of the film. Figure 10 b is the dose analysis of the spherical aberration electron microscopy image at the surface defect, which is used to identify the type of halogen ions. Figure 10 c is the halogen ion arrangement of defect sites obtained from the results of Figure b. Figure d is the mixed halogen CsPbI 3-x Br x Schematic diagram of the formation of lattice plane defects in thin films.

[0025] Figure 11 Lattice characterization of facet-defect-free perovskite films regulated by liquid-liquid phase separation. Figure 11 a and Figure 11 b is CsPbI 3-x Br x Lattice characterization of thin films. Figure 11 c is a schematic diagram of liquid-liquid phase separation to homogenize halogen ions and eliminate surface defects. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention.

[0027] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0028] The raw materials used in the present invention are not particularly limited in purity. In the present invention, the raw materials are preferably analytically pure or of conventional purity in the field of perovskite material preparation.

[0029] All materials of the present invention, their brands and abbreviations are conventional brands and abbreviations in the field. Each brand and abbreviation is clear and unambiguous in the field of its relevant use. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand, abbreviation and corresponding use.

[0030] The abbreviations of all processes of the present invention are conventional abbreviations in the field. Each abbreviation is clear and unambiguous in the field of its relevant use. Those skilled in the art can understand its conventional process steps based on the abbreviations.

[0031] In the following examples, unless otherwise specified, the methods used are conventional methods in the art, and the materials, reagents, detection devices, etc. used are all commercially available.

[0032] Please refer to Figure 1 As shown, a method for preparing a mixed halide perovskite film regulated by a fluorine-containing polymer comprises the following steps: S1. Weigh a perovskite precursor according to a ratio, dissolve it in a first solvent to form a mixed solvent, add an amino acid ligand for guiding the perovskite orientation crystallization process to the mixed solvent, and heat and stir at 60° C. for one hour to form a uniform and clear perovskite precursor solution.

[0033] It should be noted that the general formula of the perovskite is ABX3; wherein the A-site ion is one or more of cesium ion, formamidine ion, and methylamine ion; the B-site ion is lead ion and / or tin ion; the X-site ion is one or more of chloride ion, bromide ion, and iodide ion; and the amino acid ligand is one or more of amino acids such as glycine, serine, arginine, histidine, cysteine, and methionine. The first solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0034] In this example, an electronic balance was used to weigh the perovskite precursor and amino acid ligand. The perovskite precursors included cesium iodide (CsI, Xi'an Biolight, anhydrous grade, 99.99% purity), cesium bromide (CsBr, Xi'an Biolight, anhydrous grade, 99.99% purity), lead iodide (PbI2, Xi'an Biolight, anhydrous grade, 99.99% purity), and lead bromide (PbBr2, Xi'an Biolight, anhydrous grade, 99.99% purity). The amino acid ligand used was arginine (L-Arg, Aladdin, anhydrous grade, 99.8%). In this example, the molar mass ratio of cesium iodide, cesium bromide, lead iodide, lead bromide, and arginine was 0.12 mmol: 0.025 mmol: 0.037 mmol: 0.06 mmol. The first solvent was N,N-dimethylformamide (DMF, Sigma-Aldrich, 99.8%).

[0035] It is understandable that the amino acid ligands contain amino, carboxyl and other functional groups, which can react with the metal ions at the B position in the perovskite (such as Pb 2+ 、Sn 2+ ) form coordination bonds. This coordination effect stabilizes the perovskite structure and reduces its internal defect state density. For example, amino acid ligands bind to uncoordinated metal ions on the perovskite surface, reducing surface dangling bonds, inhibiting carrier recombination on the surface, and improving material stability and carrier transport performance.

[0036] Furthermore, during the crystallization process of perovskite precursor solutions, amino acid ligands can act as templates or directing agents, influencing the growth direction, size, and morphology of perovskite grains. For example, by interacting with perovskite precursor ions, they can encourage grain growth along specific crystal planes, forming uniformly oriented and sized grains. This optimizes film quality and, in turn, improves the performance of perovskite devices (such as solar cells and light-emitting diodes).

[0037] Furthermore, amino acid ligands can modify the interface between perovskites and other functional layers (such as electron transport layers and hole transport layers). Their functional groups can interact with the interfacial materials, improving interfacial contact and enhancing carrier extraction and transport efficiency at the interface. This can also reduce the charge load at the interface, improving overall device performance.

[0038] S2, adding a fluorine-containing polymer of a first mass concentration to the perovskite precursor solution to obtain a fluorine-containing polymer perovskite precursor solution.

[0039] It should be noted that in this embodiment, the fluoropolymer includes one or more of poly(perfluoroethylene propylene), poly(vinylidene fluoride), ethylene-tetrafluoroethylene copolymer, perfluoroalkoxy resin, poly(chlorotrifluoroethylene), fluorinated polyimide, fluorinated polyurethane, amorphous fluoropolymer, and perfluoropolyether. The mass ratio of the fluoropolymer to the perovskite precursor, calculated based on the total mass of the perovskite precursor components, is (0.02-0.06):1. In this embodiment, the fluoropolymer is a polyvinylidene fluoride (PVDF) solution, with a first mass concentration of 4% by weight.

[0040] S3, a fluorine-containing polymer perovskite precursor solution is subjected to a film-forming treatment on a substrate to form a liquid film, and then subjected to a time-sharing annealing treatment so that the liquid film forms a micron-scale phase separation region under the initiation of the fluorine-containing polymer, and liquid-liquid separation occurs. After cooling, a mixed halogen perovskite film regulated by the fluorine-containing polymer is obtained.

[0041] It should be noted that the above-mentioned film forming process includes one or more of spin coating, blade coating, and drop coating. Time-sharing annealing includes low-temperature annealing and high-temperature annealing. The low-temperature annealing temperature is 40-100°C and the low-temperature annealing time is 1-20 minutes; the high-temperature annealing temperature is 100-130°C and the high-temperature annealing time is 1-200 minutes.

[0042] Specifically, in this embodiment, a spin coating method is used to spin-coat the fluorine-containing polymer perovskite precursor solution at a rotation speed of 8000 revolutions per second for 50 seconds. During the time-sharing annealing, the solution is annealed at 90° C. for 10 minutes and then at 120° C. for 5 minutes.

[0043] The experimental instruments used for spin coating and heating annealing of the fluorine-containing polymer perovskite precursor solution in this embodiment include Jiangsu Leibo spin coater; German IkA magnetic heating stirrer; Suzhou Weige Technology nitrogen glove box; Japan Hamamatsu fluorescence quantum yield instrument, etc.

[0044] It is understood that in this embodiment, the high electronegativity of the fluorine atoms (4.0) in the fluoropolymer creates strong polar sites within the polymer chain. This electrostatic anchoring effect stabilizes the perovskite nuclei and inhibits disordered growth during the initial crystallization phase. Furthermore, the fluorinated side chains (e.g., -CF3 and -CF2-) impart low surface energy to the polymer, allowing it to spontaneously migrate toward the air-liquid interface in solution, forming a dynamic self-assembled layer. This property enables the polymer to continuously regulate the surface tension of the perovskite precursor solution during film formation, promoting the uniform lateral growth of perovskite grains. The strong interaction between the polar CF bonds in the fluoropolymer network and the polar solvent in the perovskite precursor facilitates the retention of the polar solvent within the perovskite mesophase during time-sharing annealing, resulting in uniform diffusion of ionic components within the film. Furthermore, the polymer matrix ultimately resides at the grain boundaries of the perovskite film, confining perovskite grain growth and improving film formability, ultimately resulting in a perovskite film with uniform grain size and no pinholes.

[0045] Furthermore, conventional antisolvent film formation relies on the rapid extraction effect of toluene / chlorobenzene, which can easily lead to transient supersaturation and precipitation of the perovskite. The fluoropolymer in this embodiment modulates the volatilization kinetics of the precursor solution, causing a gradient volatilization of the solvent (e.g., DMF / DMSO), inducing gradual crystallization of the perovskite and forming a dense, pinhole-free film structure. By omitting the antisolvent, not only is the emission of volatile organic solvents eliminated, but side reactions between the antisolvent and the perovskite precursor are also avoided.

[0046] The following combination Figures 2 to 7 Specifically, the addition of fluoropolymers (PVDF) of varying molecular weights was used to modulate the liquid-liquid phase separation process in the mixed-halogen perovskite mesophase. Furthermore, to demonstrate at a macroscopic scale that liquid-liquid phase separation actually occurs within the perovskite mesophase, the present invention employed X-ray diffraction to study the film phases and atomic force microscopy to investigate the evolution of the liquid film morphology during low-temperature annealing.

[0047] Specifically, the molecular weights of the fluoropolymer PVDF used in this embodiment are 18W, 40W and 53W. Figure 2 This is the crystallization condition of the perovskite film prepared in an embodiment of the present invention during the annealing process. Figure 3 Characterization of the liquid-liquid phase separation process of perovskite films.

[0048] like Figure 2As shown in the figure, a diffraction peak around 4° appears when the perovskite film is annealed at 90°C. With further high-temperature annealing, the intermediate phase structure disappears, and the perovskite crystal diffraction peak appears. The low-angle diffraction peak only exists during low-temperature annealing, indicating that the film phase obtained under low-temperature annealing is the intermediate metastable perovskite phase.

[0049] like Figure 3 As shown, the atomic force microscopy results show that a continuous liquid-liquid phase separation process occurs inside the film. With the extension of annealing time at low temperature, the crystal domains inside the perovskite film are observed to be gradually divided into smoother and smaller domains, which is attributed to the phase segregation behavior induced by the fluorine-containing polymer.

[0050] At the same time, as the molecular weight of the polymer increases, the degree of phase separation becomes more obvious. During the liquid-liquid phase separation process, the halogen ions inside the gel membrane will be quickly and evenly distributed.

[0051] Figure 4 This is a physical property analysis of a comparative film example. During low-temperature annealing, a low-angle diffraction peak appears in the perovskite film without PVDF. However, this diffraction peak persists even after further high-temperature annealing. No gradual regional separation was observed during the low-temperature annealing of the film, indicating that phase separation does not occur in the sample without the fluoropolymer.

[0052] Figure 5 The grain size of the perovskite film changes after the addition of the fluoropolymer. Because the fluoropolymer is distributed at the grain boundaries, it wraps around the perovskite grains during their growth, thereby limiting their growth. As a result, the perovskite film with the fluoropolymer has a more uniform grain size distribution and better film-forming properties. Furthermore, as the molecular weight of the added fluoropolymer increases, the grain distribution of the perovskite film becomes more uniform.

[0053] Figure 6 Mixed halogen CsPbI with different molecular weight PVDF 3-x Br x -LED device performance diagram. Figure 6 As shown in Figure a, the current density of the perovskite LED device does not decrease significantly with increasing PVDF molecular weight, indicating that the addition of high-molecular-weight PVDF does not adversely affect the device's transmission performance. Furthermore, it can be seen that as the PVDF molecular weight increases, the brightness of the LED device increases, and the device efficiency improves. This is because as the PVDF molecular weight increases, the defect state density of the perovskite film decreases, demonstrating that an increase in the degree of phase separation is beneficial to improving device performance.

[0054] The following combination Figures 8-11It is further explained that the synergistic effect of the fluoropolymer, amino acid and time-sharing annealing process in the present application synergistically regulates the homogenization of the halogen ions inside the system, thereby eliminating the high-latitude surface defects inside the mixed halogen perovskite lattice.

[0055] Figure 7 CsPbI with only PVDF added 3-x Br x Thin film phase and morphology analysis, including: Figure 7 a is CsPbI with only PVDF added 3-x Br x X-ray diffraction patterns of the films after annealing. Figure 7 b and Figure 7 c is the atomic force micrograph of the perovskite film with only PVDF added at 90°C after annealing for 5 minutes and 10 minutes. Figure 7 d is the transmission electron microscopy image of the perovskite film with only PVDF added. Figure 7 e and Figure 7 f is the characterization of the internal surface defects of the lattice of the perovskite film with only PVDF added.

[0056] from Figure 7 It can be seen that for CsPbI with only polymer added 3-x Br x For the sample, due to the lack of crystallization control and time-sharing annealing control by amino acids, the film will not undergo liquid-liquid phase separation. At the same time, the crystallinity of the film is poor and there are many defects in the lattice. Figure 7 As shown in Figure a, the perovskite film with only polymer added has poor crystallinity, which reflects that the polymer cannot regulate the crystallization process of the perovskite film. Figure 7 b and Figure 7 c. Under continuous temperature annealing, the grain morphology of the perovskite film did not change significantly, which reflects that the addition of polymer alone cannot regulate the liquid-liquid phase separation process of the mixed halide perovskite film.

[0057] like Figure 7 d, Through the transmission electron microscope of the film, it can be seen that the above perovskite film presents a cobblestone polycrystalline morphology. Figure 7 e and Figure 7 Further atomic-level resolution using spherical aberration electron microscopy revealed the presence of numerous intracrystalline planar defects within the lattice of mixed-halide perovskites that have not undergone liquid-liquid phase separation. These planar defects are extensively distributed within the perovskite lattice. Further magnification of the lattice at the defect site revealed that these planar defects are formed by the misalignment of lead-halide octahedral atomic layers, representing a shale-type cesium halide lattice inserted within the normal lattice.

[0058] Figure 8 CsPbI with amino acid and PVDF additives without time-sharing annealing3-x Br x Thin film phase and morphology analysis. Figure 8 a is CsPbI without time-sharing annealing 3-x Br x X-ray diffraction patterns of the films after annealing. Figure 8 b and Figure 8 c is CsPbI without time-sharing annealing 3-x Br x Atomic force microscopy images of the films after annealing at 110°C for 5 and 10 minutes. Figure 8 d is CsPbI without time-sharing annealing 3-x Br x Transmission electron microscopy image of the film. Figure 8 e and Figure 8 f is CsPbI without time-sharing annealing 3-x Br x Characterization of surface defects within the lattice of thin films.

[0059] from Figure 8 We can conclude that for perovskite films that did not undergo time-sharing annealing, a large number of surface defects were present within the lattice due to the lack of liquid-liquid phase separation. The addition of amino acids resulted in a perovskite film with good crystallinity. However, under continuous high-temperature conditions, since the perovskite film already had good crystallinity, no significant liquid-liquid phase separation occurred within the film during the continuous annealing process. Transmission electron microscopy results revealed that the film possessed the characteristics of a polycrystalline film. Further atomic-level spherical aberration electron microscopy revealed the presence of numerous surface defects within the lattice. This suggests that a large number of surface defects also exist within perovskite films that did not undergo time-sharing annealing.

[0060] Figure 9 CsPbI with only amino acids added after time-sharing annealing 3-x Br x Thin film phase and morphology analysis. Figure 9 a and Figure 9 b is CsPbI with only amino acids added 3-x Br x X-ray diffraction patterns of films after annealing at 90°C and 120°C. Figure 9 c- Figure 9 e is CsPbI with only amino acids added 3-x Br x Atomic force micrographs of the films after annealing at 90°C for 2, 5, and 10 minutes. Figure 9 f is CsPbI without time-sharing annealing 3-x Br x Transmission electron microscopy image of the film. Figure 9 g and Figure 9 h is CsPbI without time-sharing annealing3-x Br x Characterization of surface defects within the lattice of thin films.

[0061] from Figure 9 It can be seen that for perovskite films with only amino acids added, despite the use of a time-sharing annealing process, due to the absence of polymer additives, liquid-liquid phase separation does not occur during crystallization, and a large number of surface defects are present within the lattice. The perovskite film with the addition of amino acids exhibits good crystallinity. However, under continuous high-temperature conditions, since the perovskite film already has good crystallinity, no significant liquid-liquid phase separation occurs within the film during the continued annealing process. Transmission electron microscopy results demonstrate that the film has the characteristics of a polycrystalline film. Further atomic-level spherical aberration electron microscopy results reveal the presence of numerous surface defects within the lattice. This reflects the presence of numerous surface defects within the perovskite film without the addition of polymer.

[0062] Figure 10 Initiating mixed-halogen CsPbI for uneven halogen distribution 3-x Br x Schematic diagram of surface defects within a perovskite crystal.

[0063] from Figure 10 It can be seen that the generation of surface defects inside the perovskite lattice is similar to that of CsPbI 3-x Br x This is related to the uneven distribution of halogen ions during the film crystallization process. Figure 10 a, We use the spherical aberration electron microscope dose analysis method to find that the halogen ion distribution at the defect site is very uneven, which shows that the surface defects are closely related to the uneven distribution of halogen ions in the mixed halogen crystallization process. Figure 10 b, in CsPbI 3-x Br x During film crystallization, the lattice strain caused by uneven halogen distribution will lead to a large number of defects in the perovskite crystallization process. Therefore, in order to avoid mixed halide CsPbI 3-x Br x The formation of surface defects in perovskite films is crucial to promoting uniform mixing of halide ions.

[0064] Figure 11 Lattice characterization of facet-defect-free perovskite films regulated by liquid-liquid phase separation. Figure 11 a and Figure 11 b is CsPbI 3-x Br x Lattice characterization of thin films. Figure 11 c is a schematic diagram of liquid-liquid phase separation to homogenize halogen ions and eliminate surface defects.

[0065] from Figure 11It can be seen that for samples using a time-sharing annealing process and co-adding polymer and amino acid, the liquid-liquid phase separation process in the film facilitates the homogenization of halide ions. Specifically, the surface defects within the optimized mixed halide perovskite film are effectively eliminated, demonstrating the role of the liquid-liquid phase separation process in homogenizing halide ions, thereby reducing the lattice stress during the perovskite crystallization process and ultimately achieving a perovskite film without surface defects.

[0066] It should be noted that the thin film prepared by the preparation method of the present invention can be applied to fields such as semiconductor light-emitting materials or photovoltaic devices.

[0067] This invention introduces a fluoropolymer into the mixed-halogen perovskite precursor solution to improve the quality of the resulting mixed-halogen perovskite thin film. During low-temperature annealing, the fluoropolymer can in situ induce liquid-liquid phase separation within the perovskite film, which promotes the uniform distribution of halogen ions within the film. This not only reduces lattice stress during perovskite crystallization but also effectively reduces film defects, improving the quality of the mixed-halogen perovskite film and ultimately optimizing the performance of perovskite LED devices.

[0068] The above is a specific implementation of the embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of this application.

Claims

1. A method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer, characterized in that: The steps include: S1, weighing a perovskite precursor according to a ratio, dissolving it in a first solvent to form a mixed solvent, adding an amino acid ligand for guiding the perovskite orientation crystallization process to the mixed solvent, heating and stirring to form a uniform and clear perovskite precursor solution; S2, adding a fluorine-containing polymer of a first mass concentration to the perovskite precursor solution to obtain a fluorine-containing polymer perovskite precursor solution; S3, a fluorine-containing polymer perovskite precursor solution is subjected to a film-forming treatment on a substrate to form a liquid film, and then subjected to a time-sharing annealing treatment so that the liquid film forms a micron-scale phase separation region under the initiation of the fluorine-containing polymer, and liquid-liquid separation occurs. After cooling, a mixed halogen perovskite film regulated by the fluorine-containing polymer is obtained.

2. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to claim 1, characterized in that: The general formula of the perovskite in S1 is ABX3; Among them, the A-site ion is one or more of cesium ion, formamidine ion and methylamine ion; the B-site ion is lead ion and / or tin ion; the X-site ion is one or more of chloride ion, bromide ion and iodide ion; the amino acid ligand is one or more of amino acids such as glycine, serine, arginine, histidine, cysteine and methionine; and the first solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone.

3. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to claim 2, characterized in that: Calculated based on the molar amount of the B-site ion in the perovskite precursor, the molar mass ratio of the amino acid ligand to the perovskite precursor is (0.05-0.2):

1.

4. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to claim 3, characterized in that: The fluorine-containing polymer includes one or more of polyperfluoroethylene propylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, fluorine-containing polyimide, fluorine-containing polyurethane, amorphous fluorine polymer, and perfluoropolyether; the molecular weight of the fluorine-containing polymer ranges from 0.6W to 100W.

5. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to claim 4, characterized in that: The ratio of the fluorine-containing polymer to the perovskite precursor, calculated based on the total mass of the perovskite precursor components, is (0.02-0.06):

1.

6. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to any one of claims 1 to 5, characterized in that: The film forming process includes one or more of spin coating, blade coating and drop coating.

7. The method for preparing a mixed halogen perovskite film regulated by a fluorine-containing polymer according to any one of claims 1 to 5, characterized in that: The time-sharing annealing includes low-temperature annealing and high-temperature annealing. The low-temperature annealing temperature is 40-100° C. and the low-temperature annealing time is 1-20 minutes; the high-temperature annealing temperature is 100-130° C. and the high-temperature annealing time is 1-200 minutes.

8. A film prepared by the method for preparing a mixed halide perovskite film regulated by a fluorine-containing polymer as claimed in any one of claims 1 to 7.

9. Use of the thin film according to claim 8 in semiconductor light-emitting materials or photovoltaic devices.

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