A method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride

Abstract

This invention discloses a method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride. This invention relates to the field of optoelectronic materials and devices, and includes the following specific steps: Step 1: Weigh cesium iodide, lead iodide, and dimethylamine hydroiodide as raw materials, select DMF as the solvent, and then slowly add these raw materials to the DMF solvent. Stirring is performed at room temperature to obtain an inorganic perovskite precursor solution. The advantages of this invention are: by selecting cesium iodide, lead iodide, and dimethylamine hydroiodide in the inorganic perovskite precursor solution, it provides the basic elements for constructing the perovskite crystal structure, ensuring that the thin film possesses basic optoelectronic properties. It enhances the adhesion between the thin film and the substrate, effectively alleviates stress caused by differences in thermal expansion coefficients, and greatly suppresses the structural phase transition of the thin film under high-temperature conditions, successfully solving the problem of a sharp decline in the optoelectronic performance of thin films at high temperatures in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, specifically to a method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride. Background Technology

[0002] Inorganic perovskite materials, by replacing organic cations such as MA+ and FA+ with inorganic cations such as Cs+ at the A site, have shown significant advantages such as enhanced thermal stability, attracting considerable research interest in recent years. In fact, inorganic perovskite materials were synthesized as early as 1893, but it was not until around 2012, with the rapid development of organic-inorganic hybrid perovskite materials in the field of solar cells, that the optoelectronic applications of inorganic perovskite materials began to receive widespread attention from researchers. In recent years, by adjusting and improving the crystal phase, particle morphology, and coverage of thin films, research on inorganic perovskite solar cells has made some progress. However, further improving the quality of thin films remains the focus of current research. At the same time, research on light-emitting diodes (LEDs) based on inorganic perovskite materials has become an important research frontier, attracting high attention from many research institutions. Research in this field also urgently needs to improve the quality of inorganic perovskite thin films.

[0003] Existing technologies have certain drawbacks. First, they suffer from poor thermal stability. Under high-temperature conditions, inorganic perovskite films may undergo structural phase transitions, changing from a phase with good photoelectric properties to other phases, leading to a sharp decline in their photoelectric performance. Differences in thermal expansion coefficients may cause stress between the film and the substrate. With temperature changes, this stress may cause problems such as cracking and peeling of the film. Second, inorganic perovskite films prepared by existing technologies are not dense and are uneven, making them unsuitable for use in optoelectronic devices such as solar cells and light-emitting diodes. To address these issues, we propose a method for preparing inorganic perovskite films assisted by cystamine dihydrochloride. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing inorganic perovskite thin films with the assistance of cystamine dihydrochloride.

[0005] To address the problems mentioned in the background section, the present invention provides the following technical solution: a method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride, the method comprising the following specific steps:

[0006] Step 1: Weigh cesium iodide, lead iodide and dimethylamine hydroiodate as raw materials, select DMF as the solvent, and then slowly add these raw materials to the DMF solvent. Stir at room temperature to obtain an inorganic perovskite precursor solution.

[0007] Step 2: Weigh out cystamine dihydrochloride and dimethyl sulfoxide solvent, add cystamine dihydrochloride to dimethyl sulfoxide solvent and stir to obtain cystamine dihydrochloride solution;

[0008] Step 3: Take the prepared inorganic perovskite precursor solution and divide it into two equal parts, A and B. Then, slowly add the prepared cystamine dihydrochloride solution to solution B while stirring. After the addition is complete, continue stirring to obtain a mixed precursor solution containing cystamine dihydrochloride.

[0009] Step 4: Select a silicon wafer as the substrate. First, immerse it in hydrofluoric acid solution to remove the oxide layer on the surface. After immersion, rinse with deionized water. Then, immerse the silicon wafer substrate in deionized water, acetone, and ethanol in sequence for ultrasonic cleaning. After cleaning, dry it under a nitrogen atmosphere. Then, place the treated silicon wafer substrate on a spin coater. Take solution A without cystamine dihydrochloride and drop it onto the center of the substrate for pre-spin coating to make the solution spread evenly. Then, take solution B with cystamine dihydrochloride and drop it onto the center of the substrate. Then, use a spin coater to perform spin coating to form a uniform film.

[0010] Step 5: Place the spin-coated film on a hot stage for preliminary annealing. During this process, the precursor undergoes a partial reaction to form a preliminary crystal nucleus structure. Then, transfer the pre-annealed film to the hot stage for a second annealing. After these two annealing steps, the remaining precursor reacts completely, completing the preparation of the inorganic perovskite film.

[0011] Step 6: After annealing, allow the film to cool naturally to room temperature on the hot plate. Then, gently rinse the film surface with a solution of deionized water and ethanol to remove any impurities and unreacted substances that may remain on the film surface. After that, dry the cleaned film in a nitrogen atmosphere. Finally, use vacuum encapsulation technology to encapsulate the film in glass material.

[0012] As a further aspect of the present invention: In step one, 1.4 mol-1.6 mol of cesium iodide, 1.4 mol-1.6 mol of lead iodide and 1.3 mol-1.5 mol of dimethylamine hydroiodate are weighed, and 1000 μL-1200 μL of DMF solvent is used. The stirring operation is carried out at a speed of 200 r / min-300 r / min for 1 h-3 h.

[0013] As a further aspect of the present invention: In step two, 0.7 mol-0.8 mol of cystamine dihydrochloride is weighed, and 500 mL-700 mL of dimethyl sulfoxide solvent is selected. The stirring operation is carried out at a stirring speed of 150 r / min-300 r / min for 30 min-60 min to obtain a cystamine dihydrochloride solution with a concentration of 1.0 mol / L-1.6 mol / L.

[0014] As a further aspect of the present invention: In step three, the inorganic perovskite precursor solution is divided into two equal parts, A and B, each with a volume of 500uL-6000uL. Then, 25uL-30uL of the prepared cystamine dihydrochloride solution is slowly added dropwise to solution B. During the dropwise addition, the mixture is stirred at a speed of 150r / min-300r / min. After the dropwise addition is completed, stirring is continued for 5min-15min.

[0015] As a further aspect of the present invention: In step four, the silicon wafer substrate is immersed in a hydrofluoric acid solution with a hydrofluoric acid to water volume ratio of 1:10-20 for 3 min-5 min, then rinsed with deionized water 5-7 times, and ultrasonic cleaning time is 8 min-15 min for each time. After cleaning, it is dried under a nitrogen atmosphere.

[0016] As a further aspect of the present invention: In step four, 40-60 μL of solution A without added cystamine dihydrochloride is dropped onto the center of the substrate and pre-sprayed at a speed of 400-600 r / min for 3-8 seconds to ensure uniform spread of the solution. Then, 40-60 μL of solution B with added cystamine dihydrochloride is dropped onto the center of the substrate. The spin coater speed is set to 3500-4500 r / min and the spin coating time is 25-35 seconds to form a uniform film. During the spin coating process, the ambient humidity must be strictly controlled at 25%-50% and the temperature at 18℃-25℃.

[0017] As a further aspect of the present invention: In step five, the spin-coated film is first placed on a hot stage at 90℃-130℃ for preliminary annealing treatment, and the annealing time is controlled at 2min-4min. During this process, the precursor undergoes a partial reaction to form a preliminary crystal nucleus structure.

[0018] As a further aspect of the present invention: in step five, the secondary annealing process involves transferring the pre-annealed film to a hot plate at 160°C-180°C for 4-6 minutes, and during the annealing process, the heating rate is controlled at 8°C / min-20°C / min.

[0019] As a further aspect of the present invention: In step six, the film surface is washed with a solution of deionized water and ethanol mixed at a volume ratio of 1:1-2 for 8-20 seconds, and the vacuum level of the encapsulation environment needs to be controlled at 10. -3 Pa-10 - 6 Pa.

[0020] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows:

[0021] 1. This invention provides the basic elements for constructing the perovskite crystal structure by selecting cesium iodide, lead iodide, and dimethylamine hydroiodate in the inorganic perovskite precursor solution, ensuring that the film possesses basic photoelectric properties. The cystamine dihydrochloride in the cystamine dihydrochloride solution complexes with the metal ions in the precursor solution to form a complex intermediate phase, which guides the orderly growth of the crystal during film growth, significantly reduces crystal defects, makes the film denser and flatter, improves film quality, and is conducive to the formation of a flat and dense film. At the same time, it enhances the adhesion between the film and the substrate, effectively alleviates the stress caused by the difference in thermal expansion coefficients, and greatly suppresses the structural phase transition of the film under high temperature conditions, successfully solving the problem of the rapid decline in photoelectric properties of the film at high temperatures in the prior art.

[0022] 2. In the spin-coating process, the present invention enables the uniform spreading of solution A without cystamine dihydrochloride on the substrate surface by pre-spin-coating solution A without cystamine dihydrochloride, thereby optimizing the chemical environment of the substrate and creating favorable conditions for subsequent spin-coating of solution B with cystamine dihydrochloride. During the spin-coating process of solution B, cystamine dihydrochloride plays a full role, further ensuring the compactness and flatness of the film, improving the thermal stability of the film, effectively avoiding problems such as film cracking and peeling caused by stress, ensuring the integrity and stability of the film, and extending its service life.

[0023] 3. This invention promotes the uniform formation of crystal nuclei through a first annealing at a suitable low temperature, which initially stabilizes the thin film structure and enhances its adhesion to the substrate. The second annealing at a higher temperature promotes the complete reaction of the remaining precursors, achieving complete crystal growth, optimizing the crystal structure and performance. At the same time, cystamine dihydrochloride continuously stabilizes the structure, further improving the thermal stability of the thin film. This effectively avoids cracking and peeling of the thin film, while traditional thin films show significant damage. This strongly promotes its widespread application in optoelectronic devices such as solar cells and light-emitting diodes, providing solid support for the development of related technologies. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the method steps in an embodiment of the present invention;

[0025] Figure 2 These are schematic diagrams of the SEM morphology of the comparative sample and the sample containing cystamine dihydrochloride in the embodiments of the present invention.

[0026] Figure 3 This is a schematic diagram comparing the comparative sample and the example sample in the embodiments of the present invention using XRD.

[0027] Figure 4 This is a schematic diagram of the photoluminescence detection spectra of the comparative example and the embodiment in this invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0029] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Please see the appendix Figure 1 -Appendix Figure 4 This invention discloses a method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride, the method comprising the following specific steps:

[0031] Step 1: Weigh cesium iodide, lead iodide and dimethylamine hydroiodate as raw materials, select DMF as the solvent, and then slowly add these raw materials to the DMF solvent. Stir at room temperature to obtain an inorganic perovskite precursor solution.

[0032] Step 2: Weigh out cystamine dihydrochloride and dimethyl sulfoxide solvent, add cystamine dihydrochloride to dimethyl sulfoxide solvent and stir to obtain cystamine dihydrochloride solution;

[0033] Step 3: Take the prepared inorganic perovskite precursor solution and divide it into two equal parts, A and B. Then, slowly add the prepared cystamine dihydrochloride solution to solution B while stirring. After the addition is complete, continue stirring to obtain a mixed precursor solution containing cystamine dihydrochloride.

[0034] Step 4: Select a silicon wafer as the substrate. First, immerse it in hydrofluoric acid solution to remove the oxide layer on the surface. After immersion, rinse with deionized water. Then, immerse the silicon wafer substrate in deionized water, acetone, and ethanol in sequence for ultrasonic cleaning. After cleaning, dry it under a nitrogen atmosphere. Then, place the treated silicon wafer substrate on a spin coater. Take solution A without cystamine dihydrochloride and drop it onto the center of the substrate for pre-spin coating to make the solution spread evenly. Then, take solution B with cystamine dihydrochloride and drop it onto the center of the substrate. Then, use a spin coater to perform spin coating to form a uniform film.

[0035] Step 5: Place the spin-coated film on a hot stage for preliminary annealing. During this process, the precursor undergoes a partial reaction to form a preliminary crystal nucleus structure. Then, transfer the pre-annealed film to the hot stage for a second annealing. After these two annealing steps, the remaining precursor reacts completely, completing the preparation of the inorganic perovskite film.

[0036] Step 6: After annealing, allow the film to cool naturally to room temperature on the hot plate. Then, gently rinse the film surface with a solution of deionized water and ethanol to remove any impurities and unreacted substances that may remain on the film surface. After that, dry the cleaned film in a nitrogen atmosphere. Finally, use vacuum encapsulation technology to encapsulate the film in glass material.

[0037] In one embodiment of the present invention: in step one, 1.4 mol-1.6 mol of cesium iodide, 1.4 mol-1.6 mol of lead iodide and 1.3 mol-1.5 mol of dimethylamine hydroiodate are weighed, and 1000 μL-1200 μL of DMF solvent is selected. The stirring operation is carried out at a speed of 200 r / min-300 r / min for 1 h-3 h.

[0038] In one embodiment of the present invention: In step two, 0.7 mol-0.8 mol of cystamine dihydrochloride is weighed, and 500 mL-700 mL of dimethyl sulfoxide solvent is selected. The stirring operation is carried out at a stirring speed of 150 r / min-300 r / min for 30 min-60 min to obtain a cystamine dihydrochloride solution with a concentration of 1.0 mol / L-1.6 mol / L.

[0039] In one embodiment of the present invention: In step three, the inorganic perovskite precursor solution is divided into two equal parts, A and B, each with a volume of 500uL-6000uL. Then, 25uL-30uL of the prepared cystamine dihydrochloride solution is slowly added dropwise to solution B. During the dropwise addition, the mixture is stirred at a speed of 150r / min-300r / min. After the dropwise addition is completed, stirring is continued for 5min-15min.

[0040] In one embodiment of the present invention: in step four, the silicon wafer substrate is immersed in a hydrofluoric acid solution with a hydrofluoric acid to water volume ratio of 1:10-20 for 3 min-5 min, then rinsed with deionized water 5-7 times, and ultrasonic cleaning time is 8 min-15 min for each time. After cleaning, it is dried under a nitrogen atmosphere.

[0041] In one embodiment of the present invention: In step four, 40-60 μL of solution A without added cystamine dihydrochloride is dropped onto the center of the substrate and pre-sprayed at a speed of 400-600 r / min for 3-8 seconds to ensure uniform spread of the solution. Then, 40-60 μL of solution B with added cystamine dihydrochloride is dropped onto the center of the substrate. The spin coater speed is set to 3500-4500 r / min and the spin coating time is 25-35 seconds to form a uniform film. During the spin coating process, the ambient humidity must be strictly controlled at 25%-50% and the temperature at 18℃-25℃.

[0042] In one embodiment of the present invention: in step five, the spin-coated film is first placed on a hot stage at 90°C-130°C for preliminary annealing treatment. The annealing time is controlled at 2 min-4 min. During this process, the precursor undergoes a partial reaction to form a preliminary crystal nucleus structure.

[0043] In one embodiment of the present invention: in step five, the secondary annealing process involves transferring the pre-annealed film to a hot plate at 160°C-180°C for 4-6 minutes, and during the annealing process, the heating rate is controlled at 8°C / min-20°C / min.

[0044] In one embodiment of the present invention: In step six, the surface of the film is washed with a solution of deionized water and ethanol mixed at a volume ratio of 1:1-2 for 8-20 seconds, and the vacuum degree of the encapsulation environment needs to be controlled at 10. -3 Pa-10 -6 Pa.

[0045] In one embodiment of the present invention: In step one, a surfactant, comprising 0.1%-0.5% of the solvent volume, may be added to the DMF solvent. The surfactant may be sodium dodecylbenzenesulfonate or polyvinylpyrrolidone. During stirring, ultrasonic vibration is applied for 10-30 minutes at a frequency of 20kHz-50kHz to further promote the dissolution and dispersion of the raw materials, reduce agglomeration in the precursor solution, and improve the stability of the precursor solution, thereby contributing to the formation of a more uniform and high-quality inorganic perovskite film.

[0046] In one embodiment of the present invention: In step two, 0.05 mol-0.15 mol of metal-organic framework (MOF) material, ZIF-8 or MIL-101, is added to the cystamine dihydrochloride solution. During stirring, the solution is subjected to ultraviolet irradiation for 15 min-45 min, with an ultraviolet wavelength of 254 nm-365 nm. The porous structure and adsorption properties of the MOF material are utilized to adsorb impurity ions in the solution. At the same time, the ultraviolet irradiation promotes the synergistic effect between the MOF and cystamine dihydrochloride, changing the electronic structure of cystamine dihydrochloride and enhancing its complexation ability with metal ions in the precursor solution, thereby improving the quality and performance of the final film.

[0047] In one embodiment of the present invention: In step four, an alumina or titanium dioxide thin film with a thickness of 1nm-5nm is grown on the surface of a silicon substrate using atomic layer deposition (ALD) technology as a buffer layer. The ALD growth temperature is 80℃-150℃, the precursor pulse time is 0.1s-0.5s, the purge time is 5s-15s, and the number of cycles is 10-50. This buffer layer can effectively adjust the energy level difference between the silicon substrate and the inorganic perovskite thin film, reduce charge recombination at the interface, improve charge transport efficiency, and enhance the adhesion between the thin film and the substrate, thereby further improving the stability and photoelectric performance of the thin film.

[0048] Example 1, please refer to the appendix. Figure 1 -Appendix Figure 41.6 mol of cesium iodide, 1.6 mol of lead iodide, and 1.5 mol of dimethylamine hydroiodate were weighed as raw materials. 1200 μL of DMF solvent was used, and these raw materials were slowly added to the DMF solvent. The mixture was stirred at 300 rpm for 3 h at room temperature (25 °C) to obtain an inorganic perovskite precursor solution. 0.8 mol of cystamine dihydrochloride and 700 mL of dimethyl sulfoxide solvent were weighed. The cystamine dihydrochloride was added to the dimethyl sulfoxide solvent and stirred continuously at 300 rpm for 60 min to obtain a solution with a concentration of 1.6 mol / L. A 1 / L cystamine dihydrochloride solution was prepared. The prepared inorganic perovskite precursor solution was divided into two equal portions, A and B, each 6000 μL. Then, 30 μL of the prepared cystamine dihydrochloride solution was slowly added dropwise to solution B, while stirring at 300 rpm. After the addition was complete, stirring continued for 15 minutes to obtain a mixed precursor solution containing cystamine dihydrochloride. A silicon wafer was used as the substrate, and the substrate was immersed in a hydrofluoric acid solution with a hydrofluoric acid to water volume ratio of 1:20 for 5 minutes. Then, rinse seven times with deionized water. Next, ultrasonically clean the silicon substrate sequentially with deionized water, acetone, and ethanol for 15 minutes each. After cleaning, dry under a nitrogen atmosphere. Place the treated silicon substrate on a spin coater. Add 60 μL of solution A (without cystamine dihydrochloride) to the center of the substrate and pre-spray at 600 rpm for 8 seconds to ensure even spreading. Then, add 60 μL of solution B (with cystamine dihydrochloride) to the center of the substrate. Set the spin coater speed to 400 rpm. Spin-coating was performed at 500 rpm for 35 seconds to form a uniform film. During spin-coating, the ambient humidity was strictly controlled at 50%, and the temperature at 25°C. The spin-coated film was then placed on a 130°C hot stage for preliminary annealing for 4 minutes. During this process, the precursor partially reacted, forming a preliminary crystal nucleus structure. The pre-annealed film was then transferred to a 180°C hot stage for 6 minutes, with the heating rate controlled at 20°C / min. After these two annealing steps, the remaining precursor reacted completely, completing the main preparation of the inorganic perovskite film. After annealing, the film was allowed to cool naturally to room temperature on the hot stage. Then, the film surface was gently rinsed with a solution of deionized water and ethanol (volume ratio 1:2) for 20 seconds to remove any remaining impurities and unreacted substances. The cleaned film was then dried under a nitrogen atmosphere. Finally, vacuum encapsulation was used to encapsulate the film in a glass material, with the vacuum level of the encapsulation environment controlled at 10... -6 Pa.

[0049] Example 2, please refer to the appendix. Figure 1 -Appendix Figure 41.4 mol of cesium iodide, 1.4 mol of lead iodide, and 1.3 mol of dimethylamine hydroiodate were weighed as raw materials. 1000 μL of DMF solvent was used, and these raw materials were slowly added to the DMF solvent. The mixture was stirred at 200 rpm for 1 h at room temperature (20 °C) to obtain an inorganic perovskite precursor solution. 0.7 mol of cystamine dihydrochloride and 500 mL of dimethyl sulfoxide solvent were weighed. The cystamine dihydrochloride was added to the dimethyl sulfoxide solvent and stirred continuously at 150 rpm for 30 min to obtain a 1.0 mol concentration. A 1 / L cystamine dihydrochloride solution was prepared. The prepared inorganic perovskite precursor solution was divided into two equal portions, A and B, each 500 μL. Then, 25 μL of the prepared cystamine dihydrochloride solution was slowly added dropwise to solution B, while stirring at 150 rpm. After the addition was complete, stirring continued for 5 minutes to obtain a mixed precursor solution containing cystamine dihydrochloride. A silicon wafer was used as the substrate, and the substrate was immersed in a hydrofluoric acid solution with a hydrofluoric acid to water volume ratio of 1:10 for 3 minutes. Then rinse five times with deionized water. Next, ultrasonically clean the silicon substrate sequentially with deionized water, acetone, and ethanol for 8 minutes each. After cleaning, dry under a nitrogen atmosphere. Place the treated silicon substrate on a spin coater. Add 40 μL of solution A (without cystamine dihydrochloride) to the center of the substrate and pre-spray at 400 rpm for 3 seconds to ensure even spreading. Then add 40 μL of solution B (with cystamine dihydrochloride) to the center of the substrate. Set the spin coater speed to 3... Spin-coating was performed at 500 rpm for 25 seconds to form a uniform film. During spin-coating, the ambient humidity was strictly controlled at 25%, and the temperature at 18°C. The spin-coated film was then placed on a 90°C hot stage for preliminary annealing for 2 minutes. During this process, the precursor partially reacted, forming a preliminary crystal nucleus structure. The pre-annealed film was then transferred to a 160°C hot stage for 4 minutes, with the heating rate controlled at 8°C / min. After these two annealing steps, the remaining precursor reacted completely, completing the main preparation of the inorganic perovskite film. After annealing, the film was allowed to cool naturally to room temperature on the hot stage. Then, the film surface was gently rinsed with a solution of deionized water and ethanol (1:1 volume ratio) for 8 seconds to remove any remaining impurities and unreacted substances. The cleaned film was then dried under a nitrogen atmosphere. Finally, vacuum encapsulation was used to encapsulate the film in a glass material, with the vacuum level of the encapsulation environment controlled at 10... - 3 Pa.

[0050] For comparison, please refer to the appendix. Figure 1 -Appendix Figure 4The method described in patent application publication number CN108525963A, entitled "A Method for Preparing an Inorganic Halogen Perovskite Thin Film", is an inorganic halide perovskite thin film (comparative sample). The method includes the following steps: spraying a perovskite precursor liquid CsPbBr3 onto a clean bottom electrode surface at 80-100°C; adding a poor solvent while spin-coating the bottom electrode with deposited perovskite CsPbBr3; and annealing at 250-300°C to obtain an inorganic perovskite thin film. The poor solvent is toluene or a mixture of toluene and butyric acid.

[0051] As attached Figure 2 -Appendix Figure 4 As shown, Examples 1 and 2 improve the thermal stability of the thin film, avoid cracking and peeling, promote its widespread application in the field of optoelectronic devices, and provide strong support for the development of related technologies. Moreover, the synergistic cooperation of multiple technologies in each step has achieved good results in the preparation of inorganic perovskite thin films. This invention has outstanding technical advantages and broad application prospects.

[0052] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride, characterized in that, The method includes the following specific steps: Step 1: Weigh cesium iodide, lead iodide and dimethylamine hydroiodate as raw materials, select DMF as the solvent, and then slowly add these raw materials to the DMF solvent. Stir at room temperature to obtain an inorganic perovskite precursor solution. Step 2: Weigh out cystamine dihydrochloride and dimethyl sulfoxide solvent, add cystamine dihydrochloride to dimethyl sulfoxide solvent and stir to obtain cystamine dihydrochloride solution; Step 3: Take the prepared inorganic perovskite precursor solution and divide it into two equal parts, A and B. Then, slowly add the prepared cystamine dihydrochloride solution to solution B while stirring. After the addition is complete, continue stirring to obtain a mixed precursor solution containing cystamine dihydrochloride. Step 4: Select a silicon wafer as the substrate. First, immerse it in a hydrofluoric acid solution. After immersion, rinse it with deionized water. Then, immerse the silicon wafer substrate in deionized water, acetone, and ethanol in sequence for ultrasonic cleaning. After cleaning, dry it under a nitrogen atmosphere. Then, place the treated silicon wafer substrate on a spin coater. Take solution A without cystamine dihydrochloride and drop it onto the center of the substrate for pre-spin coating to make the solution spread evenly. Then, take solution B with cystamine dihydrochloride and drop it onto the center of the substrate. Then, use a spin coater to perform spin coating to form a uniform film. Step 5: Place the spin-coated film on a hot plate for preliminary annealing, then transfer the pre-annealed film to the hot plate for secondary annealing to complete the preparation of the inorganic perovskite film. Step 6: After annealing, allow the film to cool naturally to room temperature on the hot plate. Then, gently rinse the film surface with a solution of deionized water and ethanol. After that, dry the cleaned film in a nitrogen atmosphere. Finally, use vacuum encapsulation technology to encapsulate the film in glass material.

2. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step one, weigh 1.4 mol-1.6 mol of cesium iodide, 1.4 mol-1.6 mol of lead iodide, and 1.3 mol-1.5 mol of dimethylamine hydroiodate, use 1000 uL-1200 uL of DMF solvent, and stir at a speed of 200 r / min-300 r / min for 1 h-3 h.

3. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step two, 0.7 mol-0.8 mol of cystamine dihydrochloride is weighed, and 500 mL-700 mL of dimethyl sulfoxide solvent is selected. The stirring operation is carried out at a stirring speed of 150 r / min-300 r / min for 30 min-60 min to obtain a cystamine dihydrochloride solution with a concentration of 1.0 mol / L-1.6 mol / L.

4. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step three, the inorganic perovskite precursor solution is divided into two equal parts, A and B, each with a volume of 500uL-6000uL. Then, 25uL-30uL of the prepared cystamine dihydrochloride solution is slowly added dropwise to solution B. During the dropwise addition, the solution is stirred at a speed of 150r / min-300r / min. After the dropwise addition is completed, stirring is continued for 5min-15min.

5. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step four, the silicon wafer substrate is immersed in a hydrofluoric acid solution with a hydrofluoric acid to water volume ratio of 1:10-20 for 3-5 minutes, then rinsed with deionized water 5-7 times, and ultrasonically cleaned for 8-15 minutes each time. After cleaning, it is dried under a nitrogen atmosphere.

6. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step four, 40-60 μL of solution A without cystamine dihydrochloride is dropped onto the center of the substrate and pre-sprayed at a speed of 400-600 rpm for 3-8 seconds to ensure uniform spread of the solution. Then, 40-60 μL of solution B with cystamine dihydrochloride is dropped onto the center of the substrate. The spin coater speed is set to 3500-4500 rpm and the spin coating time is 25-35 seconds to form a uniform film. During the spin coating process, the ambient humidity must be strictly controlled between 25% and 50%, and the temperature between 18°C ​​and 25°C.

7. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step five, the spin-coated film is first placed on a hot stage at 90℃-130℃ for preliminary annealing. The annealing time is controlled at 2min-4min. During this process, the precursor undergoes a partial reaction to form a preliminary crystal nucleus structure.

8. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step five, the secondary annealing process involves transferring the pre-annealed film to a hot plate at 160°C-180°C for 4-6 minutes, with the heating rate controlled at 8°C / min-20°C / min during the annealing process.

9. The method for preparing inorganic perovskite thin films assisted by cystamine dihydrochloride according to claim 1, characterized in that: In step six, the film surface is washed with a solution of deionized water and ethanol mixed at a volume ratio of 1:1-2 for 8-20 seconds, and the vacuum level of the encapsulation environment needs to be controlled at 10. -3 Pa-10 -6 Pa.

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