Method for preparing lead-free perovskite by ball milling method

Abstract

The invention provides a preparation method for preparing lead-free perovskite through a ball milling method, and relates to the technical field of titanium ore preparation, the method comprises the following steps: placing a sealed grinding tank in a planetary ball mill, and carrying out ball milling treatment for 1-12 hours at a rotating speed of 200-800 rpm; wherein the mass ratio of the grinding balls to the materials is (5: 1)-(20: 1), and the grinding balls are composed of small balls with the diameter of 1 mm and large balls with the diameter of 5 mm according to the mass ratio of 7: 3; the ball milling temperature is controlled to be less than or equal to 50 DEG C; and taking out the product after the ball-milling reaction, screening, washing with ethanol to remove the residual additive, and carrying out vacuum drying on the washed product at 40 DEG C for 2 hours to obtain crystalline perovskite powder. The energy consumption is greatly reduced, and meanwhile, the adverse effect of high temperature on the material performance is avoided.

Description

Technical Field

[0001] This invention relates to the field of titanium ore preparation technology, and in particular to a method for preparing lead-free perovskite by ball milling. Background Technology

[0002] Perovskite materials, due to their excellent photoelectric properties, have shown great application potential in fields such as solar cells, light-emitting diodes, and photodetectors, becoming a research hotspot in materials science in recent years. Although traditional lead-based perovskite materials have high photoelectric conversion efficiency, the toxicity of lead and the poor chemical and environmental stability of the materials themselves severely limit their large-scale industrial application and sustainable development.

[0003] To address the inherent defects of lead-based perovskites, developing environmentally friendly and high-performance lead-free perovskite materials has become a key research focus. Currently, the main methods for preparing lead-free perovskites include solution methods and vapor deposition methods. Solution methods typically require the use of organic solvents, which not only easily cause environmental pollution but may also introduce impurities affecting product purity. Furthermore, the subsequent solvent evaporation process is difficult to control precisely, easily leading to poor material crystallinity. While vapor deposition can prepare high-purity thin film materials, it requires high-temperature and high-vacuum conditions, resulting in high equipment costs, complex processes, and low production efficiency, making it difficult to meet the needs of large-scale industrial production.

[0004] Mechanical ball milling, as a green and efficient solid-phase synthesis technology, has advantages such as simple operation, no solvent required, low energy consumption, and large-scale production, and is widely used in the field of inorganic functional material preparation. However, existing ball milling technologies still have many problems in the preparation of lead-free perovskites, such as poor matching of ball milling parameters leading to insufficient product purity and low crystallinity, or difficulty in forming the target perovskite structure due to incomplete reaction of raw materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing lead-free perovskite by ball milling, which improves the environmental safety of the material throughout its entire life cycle of production, use and disposal.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A method for preparing lead-free perovskite by ball milling, the method comprising:

[0008] Step 1: Weigh the raw material according to the target perovskite molecular formula, wherein the A-site cation is selected from Cs. + At least one of the formamidinium cations, wherein the B-site cation is selected from Ag. + Bi 3+ Ba 2+ In 3+At least one of them, the X-position halide ion is selected from I - ,Br - Cl - At least one of them;

[0009] Step 2: Place the raw materials from Step 1 in an inert gas atmosphere;

[0010] Step 3: Add the treated raw material and zirconia grinding balls together into a ball mill jar, and perform mechanical ball milling under solvent-free conditions. The ball milling parameters should meet the following requirements:

[0011] The ball-to-material mass ratio is 5:1 to 15:1, the rotation speed is 200 rpm to 800 rpm, and the ball milling time is 1 hour to 12 hours;

[0012] Step 4: Wash and dry the ball-milled products sequentially to obtain lead-free perovskite material.

[0013] Further, in step 1, weigh the raw material according to the target perovskite molecular formula, wherein the A-site cation is selected from Cs. + At least one of the formamidinium cations, wherein the B-site cation is selected from Ag. + Bi 3+ Ba 2+ In 3+ At least one of them, the X-position halide ion is selected from I - ,Br - Cl - At least one of the following, including:

[0014] Accurately weigh the raw material according to the target perovskite molecular formula ABX3, wherein:

[0015] The cation at site A is Cs. + With formamidinium cation FA + The mixture has a molar ratio of (0.1–0.9):(0.9–0.1);

[0016] The cation at the B site is Bi. 3+ With Ag + The mixture has a molar ratio of (0.5~2):1;

[0017] The halogen ion at the X-position is I. - With Br - A mixture with a molar ratio of (2-4):1;

[0018] The raw materials include at least three of the following: CsI, formamidin iodide (FAI), BiI3, AgI, and BiBr3.

[0019] Further, step 2 involves placing the raw materials from step 1 in an inert gas atmosphere, including:

[0020] The weighed raw material is transferred to a vacuum-sealed zirconia grinding jar. High-purity nitrogen is introduced into the glove box to replace the air in the jar, reducing the oxygen content to below 1 ppm. An inert atmosphere is maintained until the ball milling is complete.

[0021] Further, in step 3, the treated raw material and zirconia grinding balls are added together into a ball mill jar, and mechanical ball milling is performed under solvent-free conditions, including:

[0022] The zirconia grinding balls adopt a multi-level particle size combination, including spheres with diameters of 1mm, 2mm and 5mm, with a quantity ratio of (3~5):(2~4):1;

[0023] The ball milling process is carried out in a planetary ball mill, with the rotation speed controlled at 400-600 rpm, the ball-to-material mass ratio at 8:1-12:1, and the milling time at 4-8 hours.

[0024] Further, in step 4, the ball-milled product is washed and dried sequentially to obtain a lead-free perovskite material, including:

[0025] Add the ball-milled product to anhydrous ethanol and sonicate for 10-30 minutes. After centrifugation, discard the supernatant and repeat 3 times.

[0026] The washed solid was dried in a vacuum oven at 60–80°C for 6–12 hours to obtain lead-free perovskite powder.

[0027] Furthermore, the ball-milled product was added to anhydrous ethanol and ultrasonically dispersed for 10–30 minutes. After centrifugation, the supernatant was discarded. This process was repeated three times, including:

[0028] The ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:10 to 1:15, and ultrasonically treated for 10 to 15 minutes at a power of 200 to 300 W.

[0029] Centrifuge the dispersion at 3000-5000 rpm for 5-10 minutes and discard the supernatant containing free impurities.

[0030] Add an equal amount of anhydrous ethanol back to the centrifuged precipitate, repeat the operation twice, and complete a total of 3 washing cycles.

[0031] The above-described solution of the present invention has at least the following beneficial effects:

[0032] The mechanical ball milling process employs solvent-free conditions, eliminating the need for organic solvents throughout the entire process. This avoids environmental pollution and the emission of toxic and harmful substances caused by solvent evaporation, reducing potential health hazards to operators and aligning with the principles of green chemistry and sustainable development. Furthermore, the prepared lead-free perovskite material contains no lead, fundamentally solving the toxicity problem of traditional lead-based perovskites and significantly improving the environmental safety of the material throughout its entire lifecycle, from production and use to disposal.

[0033] By optimizing ball milling parameters (ball-to-material mass ratio 5:1 to 15:1, rotation speed 200 rpm to 800 rpm, and time 1 hour to 12 hours), the raw materials can be fully reacted in a short time, significantly shortening the preparation cycle and greatly improving production efficiency compared to traditional methods such as vapor deposition. Furthermore, the entire process does not require harsh conditions such as high temperature or high vacuum, the operation steps are simple, the parameters are easy to control, facilitating standardized production and reducing the skill requirements for operators.

[0034] Ball milling in an inert gas atmosphere effectively prevents the introduction of impurities through reactions between raw materials and products and water or oxygen in the air, ensuring high product purity. Simultaneously, appropriate ball milling parameters provide sufficient mechanical energy, promoting full contact, breakage, and reaction of raw material particles. This facilitates the formation of a structurally complete and highly crystalline target perovskite phase, reducing the formation of amorphous and impurity phases, thereby guaranteeing the excellent optoelectronic properties of lead-free perovskite materials.

[0035] Wide applicability and high flexibility in material design: This invention targets the A-site (Cs) + (formamidin cation), B site (Ag) + Bi 3 + Ba 2+ In 3+ ) and X position (I - ,Br - Cl - Lead-free perovskite systems with various ion combinations have good applicability. Lead-free perovskite materials with different compositions can be flexibly prepared by adjusting the raw material ratio, which can meet the diverse needs of different fields such as solar cells and light-emitting diodes for material performance. This provides a broad space for the composition optimization and performance control of lead-free perovskite materials.

[0036] Mechanical ball milling has the advantages of low equipment cost and easy scale-up of production process. Combined with the optimized process parameters of this invention, it can realize the mass production of lead-free perovskite materials, effectively reducing the threshold for industrial production. Detailed Implementation

[0037] Example 1

[0038] Raw material preparation: Accurately weigh all raw materials according to the target perovskite molecular formula ABX3. For the A-site cation, select Cs. + with FA + To achieve a molar ratio of 0.5:0.5, 0.5 mmol of CsI was weighed, and its mass could be calculated from the molar mass of CsI (approximately 259.81 g / mol), i.e., 0.5 mmol × 259.81 g / mol = 129.905 mg; 0.5 mmol of formamidin iodide (FAI) was weighed, and the molar mass of FAI is approximately 174.94 g / mol, so its mass is 0.5 mmol × 174.94 g / mol = 87.47 mg.

[0039] Regarding the B-site cation, Bi 3+ With Ag + The molar ratio was set to 1:1. 0.5 mmol of BiI3 was weighed; the molar mass of BiI3 is approximately 589.69 g / mol, corresponding to a mass of 0.5 mmol × 589.69 g / mol = 294.845 mg. 0.5 mmol of AgI was weighed; the molar mass of AgI is approximately 234.77 g / mol, corresponding to a mass of 0.5 mmol × 234.77 g / mol = 117.385 mg.

[0040] For the X-position halide ion, I - With Br - The molar ratio is 3:1, so 0.25 mmol of BiBr3 is weighed out. The molar mass of BiBr3 is approximately 448.69 g / mol, and the mass is 0.25 mmol × 448.69 g / mol = 112.1725 mg. These carefully weighed raw materials are set aside, ready for the next step of processing.

[0041] Establishing an inert gas atmosphere: Carefully transfer all weighed raw materials into a specialized vacuum-sealed zirconia grinding jar. Then, move the grinding jar into a glove box filled with high-purity nitrogen. Continuously purge high-purity nitrogen into the glove box, constantly replacing the existing air within the jar. Monitor the oxygen content in real-time using a high-precision oxygen content detection device until the oxygen content in the jar successfully drops below 1 ppm. Thereafter, maintain this high-purity nitrogen inert atmosphere within the glove box throughout the entire subsequent ball milling process to ensure the stability of the reaction environment and prevent interference from impurities such as oxygen in the air.

[0042] Mechanical ball milling operation: Zirconia grinding balls of a specific size are added to a grinding jar already under inert gas protection. These grinding balls are produced using a multi-stage particle size combination, with the ratio of 1mm, 2mm, and 5mm diameter balls strictly controlled at 4:3:1. Through precise calculation and addition, the ball-to-material mass ratio is ensured to reach 10:1. The grinding jar loaded with raw materials and grinding balls is then installed in a planetary ball mill, and the mill speed is set to 500 rpm. Ball milling is performed for 6 hours under solvent-free conditions. During the ball milling process, the high-speed operation of the mill causes the grinding balls to continuously collide and rub against the raw materials, gradually refining the raw material particles and inducing a chemical reaction, transforming them into the target perovskite structure.

[0043] Washing and Drying: After ball milling, the product is washed. The milled product is mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:12. The mixture is placed in an ultrasonic device, set to 250W, and ultrasonically dispersed for 20 minutes. Ultrasonic action ensures the milled product is fully dispersed in the anhydrous ethanol and helps remove some impurities adhering to the product surface. After ultrasonic dispersion, the mixture is transferred to a centrifuge and centrifuged at 4000 rpm. Under centrifugal force, the heavier product precipitates at the bottom of the centrifuge tube, while the supernatant containing free impurities remains on top. The supernatant is carefully discarded, completing the first wash. Next, an equal volume of anhydrous ethanol is added back to the precipitate in the centrifuge tube, and the ultrasonic dispersion and centrifugation are repeated. This washing cycle is performed a total of 3 times to remove impurities from the product to the greatest extent possible.

[0044] After washing, the washed solid product was transferred to a vacuum oven. The temperature of the vacuum oven was set to 70℃, and drying was carried out under vacuum for 8 hours. Vacuum drying effectively removed residual solvents such as anhydrous ethanol from the product, ultimately yielding pure lead-free perovskite powder. Subsequent testing and analysis showed that the powder exhibited the expected lead-free perovskite structure and performance characteristics.

[0045] Example 2

[0046] Raw material preparation: Weigh the raw materials according to the specified molecular formula ABX3 for the target perovskite. The A-site cation is selected as Cs. + with FA + The molar ratio was set to 0.3:0.7. 0.3 mmol of CsI was weighed, which corresponds to a mass of 0.3 mmol × 259.81 g / mol = 77.943 mg; 0.7 mmol of FAI was weighed, which corresponds to a mass of 0.7 mmol × 174.94 g / mol = 122.458 mg.

[0047] For the B-site cation, Bi 3+ With Ag +The molar ratio was determined to be 1.5:1. 0.75 mmol of BiI was weighed, with a mass of 0.75 mmol × 589.69 g / mol = 442.2675 mg; 0.5 mmol of AgI was weighed, with a mass of 0.5 mmol × 234.77 g / mol = 117.385 mg.

[0048] Regarding the X-position halide ion, I - With Br - The molar ratio was set at 2.5:1, therefore 0.2 mmol of BiBr3 was weighed, with a mass of 0.2 mmol × 448.69 g / mol = 89.738 mg. These carefully weighed raw materials were properly stored in preparation for subsequent reaction operations.

[0049] Creating an inert gas environment: The precisely weighed raw materials were transferred one by one into a vacuum-sealed zirconia grinding jar. The jar was then moved into a glove box equipped with a high-purity nitrogen supply system. Inside the glove box, the high-purity nitrogen valve was opened, allowing nitrogen to continuously flow into the grinding jar to displace the existing air. The oxygen content was closely monitored using a professional oxygen content monitoring instrument until it stabilized below 1 ppm. Throughout the subsequent ball milling process, the high-purity nitrogen inert environment within the glove box was maintained to provide a stable and pure atmosphere for the raw material reaction, preventing external impurities from adversely affecting the reaction.

[0050] Mechanical ball milling implementation: Zirconia grinding balls were added to a grinding jar under inert gas protection, using a combination of 1mm, 2mm, and 5mm diameter balls in a ratio of 5:2:1. Through precise calculation and addition, the ball-to-material mass ratio was achieved to 12:1. The grinding jar, loaded with raw materials and grinding balls, was installed on a planetary ball mill, and the mill speed was set to 450 rpm. The ball milling operation was carried out for 5 hours under solvent-free conditions. During the ball milling process, the high-speed rotating grinding balls continuously impacted and rubbed the raw material particles, promoting physical refinement and chemical reactions, gradually forming the target lead-free perovskite structure.

[0051] Washing and Drying Process: After the ball milling reaction is completed, the product washing process begins. The ball-milled product is mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:10. The mixture is placed in an ultrasonic device with a power setting of 200W and ultrasonically dispersed for 15 minutes. Ultrasonic action ensures the ball-milled product is uniformly dispersed in the anhydrous ethanol and helps remove impurities adsorbed on the product surface. After ultrasonic dispersion, the mixture is transferred to a centrifuge and centrifuged at 3500 rpm. Under centrifugal force, the product precipitates at the bottom of the centrifuge tube, while the supernatant containing impurities remains on top. The supernatant is carefully discarded, completing the first wash. Then, an equal volume of anhydrous ethanol is added to the precipitate in the centrifuge tube, and the ultrasonic dispersion and centrifugation are repeated for a total of three washing cycles to ensure high product purity.

[0052] After the washing step, the washed solid product was transferred to a vacuum oven. The vacuum oven temperature was set to 65℃, and drying was carried out under vacuum for 10 hours. Vacuum drying effectively removed residual solvents such as anhydrous ethanol from the product, ultimately yielding a pure lead-free perovskite material. Subsequent testing and analysis showed that the material exhibited the expected lead-free perovskite structure and performance characteristics.

[0053] Example 3

[0054] Raw material preparation: Weigh the raw material according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.7:0.3, with Bi at the B-site cation. 3+ With Ag + The molar ratio is 2:1, and the X-position halide ion I - With Br - The molar ratio is 4:1. The specific raw materials and dosages are: CsI 0.7 mmol (0.7 × 259.81 = 181.867 mg), FAI 0.3 mmol (0.3 × 174.94 = 52.482 mg), BiI3 1 mmol (1 × 589.69 = 589.69 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), BiBr3 0.25 mmol (0.25 × 448.69 = 112.1725 mg).

[0055] Inert gas atmosphere treatment: The weighed raw materials are transferred to a vacuum-sealed zirconia grinding jar, and then transferred to a glove box to purge the air in the jar with high-purity nitrogen. The oxygen content is monitored in real time by an oxygen content monitor until the oxygen content drops to 0.8 ppm. This inert atmosphere is maintained until the ball milling is completed.

[0056] Mechanical ball milling: Add zirconia grinding balls with diameters of 1mm, 2mm, and 5mm in a ratio of 3:4:1 and a ball-to-material mass ratio of 8:1. Install the grinding jar into a planetary ball mill, set the speed to 400 rpm, and ball mill for 8 hours without solvent. During the ball milling process, regularly observe the operating status of the ball mill to ensure stable operation of the equipment.

[0057] Washing and drying: The ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:15 and ultrasonically dispersed at 300W for 10 minutes. Then, it was centrifuged at 5000rpm, and the supernatant was discarded. This process was repeated three times. The washed solid was then dried in an 80℃ vacuum oven for 6 hours to obtain lead-free perovskite powder.

[0058] Example 4

[0059] Raw material preparation: Weigh the raw materials according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.1:0.9, with Bi at the B-site cation. 3+ With Ag + The molar ratio is 0.5:1, and the X-position halide ion I... - With Br - The molar ratio is 2:1. The raw materials and dosages are: CsI 0.1 mmol (0.1 × 259.81 = 25.981 mg), FAI 0.9 mmol (0.9 × 174.94 = 157.446 mg), BiI3 0.25 mmol (0.25 × 589.69 = 147.4225 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), BiBr3 0.25 mmol (0.25 × 448.69 = 112.1725 mg).

[0060] Inert gas atmosphere treatment: Transfer the weighed raw materials to a vacuum-sealed zirconia grinding jar. Purge the air with high-purity nitrogen into the glove box to reduce the oxygen content to 0.9 ppm. Maintain this inert atmosphere until ball milling is complete. During the transfer process, prevent spillage of the raw materials and ensure that all materials enter the grinding jar.

[0061] Mechanical ball milling: Add zirconia grinding balls with diameters of 1mm, 2mm, and 5mm in a ratio of 4:2:1 and a ball-to-material mass ratio of 9:1. Perform solvent-free ball milling at 600 rpm for 4 hours in a planetary ball mill. During ball milling, monitor the equipment temperature to prevent overheating from affecting the milling effect.

[0062] Washing and drying: The ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:11, ultrasonically dispersed at 220W for 25 minutes, and centrifuged at 3800rpm. The supernatant was discarded, and the process was repeated three times. The washed solid was dried in a vacuum oven at 60℃ for 12 hours to obtain lead-free perovskite material.

[0063] Example 5

[0064] Raw material preparation: Weigh the raw material according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.9:0.1, with Bi at the B-site cation. 3+ With Ag + The molar ratio is 1.2:1, and the X-position halide ion I... - With Br - The molar ratio is 3.5:1. The specific raw materials and dosages are: CsI 0.9 mmol (0.9 × 259.81 = 233.829 mg), FAI 0.1 mmol (0.1 × 174.94 = 17.494 mg), BiI3 0.6 mmol (0.6 × 589.69 = 353.814 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), BiBr3 0.14 mmol (0.14 × 448.69 ≈ 62.8166 mg).

[0065] Inert gas atmosphere treatment: Transfer the raw material to a vacuum-sealed zirconia grinding jar, and purge the air with high-purity nitrogen in the glove box to reduce the oxygen content to 0.8 ppm. Maintain the inert atmosphere until the ball milling is complete. During operation, ensure the grinding jar is well-sealed to prevent nitrogen leakage.

[0066] Mechanical ball milling: Zirconia grinding balls with diameters of 1mm, 2mm, and 5mm were added in a ratio of 3:4:1, and the ball-to-material mass ratio was 11:1. The mixture was ball-milled in a planetary ball mill at 550 rpm for 7 hours without solvent. The equipment operation was checked periodically during the milling process.

[0067] Washing and drying: The ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:13, ultrasonically dispersed at 280W for 18 minutes, and centrifuged at 4500rpm. The supernatant was discarded, and the process was repeated 3 times. The washed solid was then dried in a vacuum oven at 75℃ for 7 hours to obtain lead-free perovskite powder.

[0068] Example 6

[0069] Raw material preparation: Weigh the raw materials according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.4:0.6, with Bi at the B-site cation.3+ With Ag + The molar ratio is 1.8:1, and the X-position halide ion I... - With Br - The molar ratio was 3.2:1. The specific raw materials and quantities were: CsI 0.4 mmol (0.4 × 259.81 = 103.924 mg), FAI 0.6 mmol (0.6 × 174.94 = 104.964 mg), BiI3 0.9 mmol (0.9 × 589.69 = 530.721 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), and BiBr3 0.16 mmol (0.16 × 448.69 ≈ 71.7904 mg). An electronic balance with an accuracy of 0.01 mg was used during the weighing process to ensure the accuracy of each raw material. After weighing, the raw materials were placed into clean weighing bottles for later use.

[0070] Inert gas atmosphere treatment: Carefully transfer all weighed raw materials into a vacuum-sealed zirconia grinding jar, avoiding spillage during the transfer. Then, move the grinding jar into a glove box, close the glove box door, open the high-purity nitrogen valve, and introduce high-purity nitrogen into the glove box to displace the air inside the box and grinding jar. Monitor the oxygen content in real time using an oxygen content detector inside the glove box until the oxygen content in the jar drops below 0.9 ppm. Maintain the inert atmosphere in the glove box until the ball milling operation is complete.

[0071] Mechanical ball milling: Add zirconia grinding balls to the grinding jar, with a ball ratio of 1mm, 2mm, and 5mm in diameter of 3:3:1. The ball-to-material mass ratio is calculated and controlled to be 8:1. Install the grinding jar securely in the corresponding position on the planetary ball mill. Set the ball mill speed to 420 rpm and perform ball milling under solvent-free conditions for 7 hours. During the ball milling process, observe the operating status of the ball mill every hour, including whether the speed is stable and whether there is any abnormal noise, to ensure the ball milling process is proceeding normally.

[0072] Washing and Drying: After ball milling, remove the grinding jar and transfer the milled product to a beaker. Add anhydrous ethanol at a solid-liquid mass ratio of 1:14. Place the beaker in an ultrasonic cleaner, set the ultrasonic power to 260W, and ultrasonically disperse for 22 minutes. After ultrasonication, pour the mixture into a centrifuge tube and centrifuge at 3900 rpm for 8 minutes. After centrifugation, carefully remove the supernatant with a pipette, retaining the precipitate at the bottom. Repeat the above washing operation twice, for a total of three washings. Transfer the washed precipitate to a petri dish and place it in a vacuum oven. Set the oven temperature to 68℃ and the vacuum degree to -0.09MPa, and dry for 9 hours. After drying, remove the petri dish to obtain lead-free perovskite powder, which should be sealed and stored in a desiccator for later use.

[0073] Example 7

[0074] Raw material preparation: Weigh the raw material according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.6:0.4, with Bi at the B-site cation. 3+ With Ag + The molar ratio is 0.8:1, and the X-position halide ion I... - With Br - The molar ratio was 2.8:1. The specific raw materials and dosages were: CsI 0.6 mmol (0.6 × 259.81 = 155.886 mg), FAI 0.4 mmol (0.4 × 174.94 = 69.976 mg), BiI3 0.4 mmol (0.4 × 589.69 = 235.876 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), and BiBr3 0.18 mmol (0.18 × 448.69 ≈ 80.7642 mg). Each raw material was weighed twice after initial weighing to minimize errors. The weighed materials were then placed together in a dry glass tray.

[0075] Inert gas atmosphere treatment: Transfer all raw materials from the tray to a vacuum-sealed zirconia grinding jar, tighten the jar lid but do not completely seal it, and then place it in a glove box. Inside the glove box, first evacuate the grinding jar, then introduce high-purity nitrogen. Repeat this replacement process three times. After the last nitrogen introduction, ensure that the oxygen content inside the jar drops below 0.8 ppm. Then, completely seal the grinding jar and maintain the inert atmosphere until the ball milling is completed.

[0076] Mechanical ball milling: Add zirconia grinding balls (1mm, 2mm, 5mm diameter) to a sealed grinding jar in a ratio of 5:4:1, controlling the ball-to-material mass ratio to be 11:1. Install the grinding jar onto a planetary ball mill. After verifying that everything is correct, set the mill speed to 580 rpm and perform solvent-free ball milling for 5 hours. During the milling process, record the operating temperature of the ball mill, ensuring it does not exceed 40℃. If the temperature is too high, pause the milling process and resume operation only after the temperature has dropped to the normal range.

[0077] Washing and Drying: After ball milling, collect the milled product and add anhydrous ethanol at a solid-liquid mass ratio of 1:11. After stirring evenly, place the mixture in an ultrasonic cleaner, set the power to 230W, and ultrasonically disperse for 16 minutes. Transfer the ultrasonically dispersed mixture to a centrifuge tube and centrifuge at 4300 rpm for 7 minutes, discarding the supernatant. Perform two more washing operations using the same method. Place the washed solid in a vacuum desiccator and dry it in a vacuum oven at 62℃ for 11 hours. During the drying process, observe the vacuum level in the oven every 2 hours to ensure that the vacuum level is stable at approximately -0.095 MPa. After drying, lead-free perovskite material is obtained, and the purity meets the requirements.

[0078] Example 8

[0079] Raw material preparation: Weigh the raw materials according to the target perovskite molecular formula ABX3, and the A-site cation Cs + with FA + The molar ratio is 0.2:0.8, with Bi at the B-site cation. 3+ With Ag + The molar ratio is 1.3:1, and the X-position halide ion I... - With Br - The molar ratio is 3.8:1. The specific raw materials and dosages are as follows: CsI 0.2 mmol (0.2 × 259.81 = 51.962 mg), FAI 0.8 mmol (0.8 × 174.94 = 139.952 mg), BiI3 0.65 mmol (0.65 × 589.69 ≈ 383.2985 mg), AgI 0.5 mmol (0.5 × 234.77 = 117.385 mg), BiBr3 0.13 mmol (0.13 × 448.69 ≈ 58.3297 mg). Before weighing, all raw materials are pretreated to remove any impurities and moisture that may be present on the surface, ensuring the purity of the raw materials.

[0080] Inert gas atmosphere treatment: Transfer the pretreated raw materials to a vacuum-sealed zirconia grinding jar. Place the grinding jar in a glove box, open the high-purity nitrogen inlet valve, and continuously purge with nitrogen for 30 minutes to displace the air inside the jar. After confirming that the oxygen content inside the jar has dropped below 0.7 ppm using an oxygen content monitor, close the inlet valve and maintain the inert environment inside the glove box until the ball milling is complete. When transferring raw materials, use a dedicated stainless steel spoon to avoid contamination from contact with other substances.

[0081] Mechanical ball milling: Add zirconia grinding balls (1mm, 2mm, 5mm diameter) to the grinding jar in a ratio of 4:4:1, controlling the ball-to-material mass ratio to be 10:1. Fix the grinding jar on a planetary ball mill, set the speed to 520 rpm, and ball mill without solvent for 6.5 hours. During the ball milling process, adopt an intermittent operation mode, i.e., run for 30 minutes and pause for 5 minutes, to reduce heat accumulation during the ball milling process and ensure uniform ball milling effect.

[0082] Washing and Drying: After ball milling, the milled product was removed, and anhydrous ethanol was added at a solid-liquid mass ratio of 1:13. After mixing thoroughly, the mixture was ultrasonically treated with a power of 270W for 19 minutes. Following ultrasonication, the mixture was centrifuged at 4100 rpm for 6 minutes, and the supernatant was discarded. The washing process was repeated twice. The solid product was then placed in a vacuum oven at 69℃ and dried for 8.5 hours. After drying, the oven temperature was allowed to drop to room temperature, and the product was removed, yielding lead-free perovskite powder with uniform particles and a stable structure.

[0083] Comparative Example 1

[0084] Raw material preparation: The types of raw materials are the same as in Example 1, but the molar ratio of A-site, B-site, and X-site ions is adjusted. A-site cation Cs + with FA + The molar ratio is 1:0 (i.e., only Cs is used). + ), B-site cation Bi 3+ With Ag + The molar ratio is 0.3:1, and the X-position halide ion I... - With Br - The molar ratio is 1:1. The specific raw materials and quantities are: CsI 1.0 mmol (1.0 × 259.81 = 259.81 mg), BiI3 0.3 mmol (0.3 × 589.69 = 176.907 mg), AgI 1.0 mmol (1.0 × 234.77 = 234.77 mg), BiBr3 0.5 mmol (0.5 × 448.69 = 224.345 mg). An electronic balance with an accuracy of 0.01 mg was used for weighing to ensure accuracy.

[0085] Inert gas atmosphere treatment: No strict inert gas replacement was performed in the glove box. The raw materials were simply placed in a regular sealed grinding jar with an oxygen content of about 20,000 ppm (i.e., the normal oxygen content in the air). No nitrogen replacement was performed.

[0086] Mechanical ball milling: Using zirconium oxide grinding balls of a single particle size (balls with a diameter of only 5 mm), the ball-to-material mass ratio was 4:1 (lower than 10:1 in Example 1), and the balls were ball-milled in a planetary ball mill at a speed of 150 rpm (lower than 500 rpm in Example 1) for 3 hours without solvent (shorter than 6 hours in Example 1).

[0087] Washing and drying: During washing, the ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:5 (higher than the 1:12 ratio in Example 1), the ultrasonic power was 150W (lower than the 250W in Example 1), and the ultrasonic time was 10 minutes. Washing was performed only once (less than the three times in Example 1). Drying was carried out in a conventional oven (non-vacuum) at 80°C for 6 hours. The final product contained many impurities and did not form a complete perovskite structure.

[0088] Comparative Example 2

[0089] Raw material preparation: The types of raw materials are the same as in Example 4, but the combination and ratio of raw materials are adjusted. BiBr3 (i.e., only I at the X position) is not used. - ), B-site cation Bi 3+ With Ag + The molar ratio is 3:1 (higher than 0.5:1 in Example 4), with the A-site cation Cs. + with FA + The molar ratio is 0.05:0.95 (Cs) + The proportion is lower than 0.1:0.7 in Example 4. The specific raw materials and amounts are: CsI 0.05mmol (0.05×259.81=12.9905mg), FAI 0.95mmol (0.95×174.94=166.193mg), BiI 3 1.5mmol (1.5×589.69=884.535mg), AgI 0.5mmol (0.5×234.77=117.385mg).

[0090] Inert gas atmosphere treatment: After the raw materials were transferred to the grinding jar, high-purity nitrogen was introduced for only 1 minute (not fully replaced), and the oxygen content in the jar was about 50 ppm (higher than 0.9 ppm in Example 4). The inert atmosphere was not maintained until the end of ball milling (the grinding jar was opened for observation during ball milling).

[0091] Mechanical ball milling: Zirconia grinding balls were used with a single particle size of 1 mm in diameter, and the ball-to-material mass ratio was 6:1 (lower than 9:1 in Example 4). The balls were milled in a planetary ball mill at a speed of 700 rpm (higher than 600 rpm in Example 4) for 2 hours (shorter than 4 hours in Example 4).

[0092] Washing and drying: During washing, the ultrasonic power was 180W (lower than 220W in Example 4), the ultrasonic time was 10 minutes (shorter than 25 minutes in Example 4), the centrifugation speed was 3000 rpm (lower than 3800 rpm in Example 4), the drying temperature was 50℃ (lower than 60℃ in Example 4), and the drying time was 5 hours (shorter than 12 hours in Example 4). The final product had poor crystallinity and contained a large amount of unreacted raw material impurities.

[0093] Comparative Example 3

[0094] Raw material preparation: The types of raw materials are the same as in Example 7, but the combination of raw materials is changed. Lead-containing raw material PbI2 is added (which does not meet the lead-free requirement), and the ratio of X-site ions is adjusted. X-site halide ions I - With Br - The molar ratio was 1:2 (lower than 2.8:1 in Example 7), and only Bi was used as the B-site cation. 3+ (No Ag) + The specific raw materials and dosages are as follows: CsI 0.6 mmol (0.6 × 259.81 = 155.886 mg), FAI 0.4 mmol (0.4 × 174.94 = 69.976 mg), BiI3 0.9 mmol (0.9 × 589.69 = 530.721 mg), BiBr3 0.6 mmol (0.6 × 448.69 = 269.214 mg), and PbI2 0.2 mmol (0.2 × 461.01 = 92.202 mg).

[0095] Inert gas atmosphere treatment: Raw material transfer and ball milling are carried out directly in the air without the use of a glove box (no inert gas protection), and the oxygen content in the tank is the same as that in the air (about 21%).

[0096] Mechanical ball milling: The number ratio of zirconia grinding balls was 1:1:1 (different from 5:4:1 in Example 7), and the ball-to-material mass ratio was 3:1 (much lower than 11:1 in Example 7). The balls were milled in a planetary ball mill at a speed of 300 rpm (lower than 580 rpm in Example 7) for 15 hours (longer than 5 hours in Example 7).

[0097] Washing and drying: Deionized water (instead of anhydrous ethanol) was used for washing, with a solid-liquid mass ratio of 1:8 (lower than 1:11 in Example 7). No ultrasonic treatment was performed (direct stirring). Centrifugation speed was 2500 rpm (lower than 4300 rpm in Example 7). Drying was done by natural air drying (not in a vacuum oven). The final product did not meet the lead-free requirements due to the introduction of lead, and the use of water damaged the perovskite structure, resulting in extremely poor performance.

[0098] Beneficial effects corresponding to Example 1

[0099] Compared with Comparative Examples 1, 2, and 3, Example 1 has significantly better effects. Regarding the raw material ratio, Example 1 uses A-site Cs... + with FA + Molar ratio 0.5:0.5, B site Bi 3+ With Ag + Molar ratio 1:1, X position I - With Br - A reasonable combination with a molar ratio of 3:1, while in Comparative Example 1, only Cs is used at position A. + An imbalance in the B-site ratio (0.3:1) and a deviation in the X-site ratio (1:1) resulted in incomplete reaction of the raw materials; Comparative Example 2 lacked Br. - Furthermore, the ratio of B sites is too high (3:1), and in Comparative Example 3, lead was introduced and there is no Ag at the B sites. + All of these measures disrupted the ideal structure of the perovskite. Regarding inert gas treatment, Example 1 strictly controlled the oxygen content to below 1 ppm, while Comparative Example 1 did not use inert gas, Comparative Example 2 had insufficient replacement (oxygen content 50 ppm), and Comparative Example 3 operated directly in air, thus avoiding raw material oxidation and ensuring the purity of the reaction. In terms of ball milling parameters, Example 1 used multi-stage grinding balls (4:3:1), a ball-to-material ratio of 10:1, a rotation speed of 500 rpm, and a time of 6 hours. Comparative Example 1 used single-size balls, a ball-to-material ratio of 4:1, a low rotation speed, and a short time. Comparative Example 2 had an excessively high rotation speed and a short time, while Comparative Example 3 had an excessively low ball-to-material ratio and an excessively long time. This resulted in more uniform mixing of the raw materials, a more thorough reaction, and finer product particles in Example 1. During washing and drying, Example 1 underwent three washes with anhydrous ethanol (solid-liquid ratio 1:12) and vacuum drying. Compared to Comparative Example 1's single wash (solid-liquid ratio 1:5) and ordinary drying, Comparative Example 2's short-time ultrasonication and low-speed centrifugation, and Comparative Example 3's water washing and natural air drying, these methods effectively removed impurities and prevented structural damage. Therefore, the lead-free perovskite powder obtained in Example 1 has high purity, intact structure, good crystallinity, and is free from impurity contamination, meeting lead-free requirements and exhibiting stable performance.

[0100] Beneficial effects corresponding to Example 2

[0101] Compared with Comparative Examples 1, 2, and 3, Example 2 shows significant advantages. Regarding the raw material ratios, Example 2 has a balanced ratio of A-site (0.3:0.7), B-site (1.5:1), and X-site (2.5:1), while Comparative Example 1 has a single A-site and an unbalanced B-site ratio, Comparative Example 2 has a single X-site and an excessively high B-site ratio, and Comparative Example 3 contains lead and has an inverted X-site ratio, thus ensuring the stability of the perovskite lattice. In the inert gas treatment, Example 2 controls the oxygen content to below 1 ppm and maintains it throughout the process, while Comparative Example 1 has no inert atmosphere, Comparative Example 2 has insufficient replacement and disrupted the atmosphere midway, and Comparative Example 3 has no protection. This effectively prevents the raw materials from being oxidized and ensures the directional progress of the reaction. Regarding the ball milling parameters, Example 2 used a 5:2:1 multi-stage grinding ball ratio of 12:1, a rotation speed of 450 rpm, and a milling time of 5 hours. Compared to Comparative Example 1's single ball, low ball-to-material ratio, and low rotation speed, Comparative Example 2's single ball, high rotation speed, and short milling time, and Comparative Example 3's unreasonable ball ratio and excessively long milling time, this resulted in more uniform stress on the raw material, more complete reaction, and better particle dispersion. During washing and drying, Example 2 underwent three washes (solid-liquid ratio 1:10) and vacuum drying at 65°C for 10 hours. Comparative Example 1's fewer washes and ordinary drying, Comparative Example 2's low-power ultrasonic treatment and short drying time, and Comparative Example 3's water washing and natural air drying all resulted in impurity residue or structural damage. In contrast, the product of Example 2 had fewer impurities and a more stable structure. In summary, the lead-free perovskite material of Example 2 has high purity, uniform particles, complete crystallization, meets lead-free characteristics, and outperforms all comparative examples.

[0102] Beneficial effects corresponding to Example 3

[0103] Compared to Comparative Examples 1, 2, and 3, Example 3 exhibits significantly beneficial effects. Regarding the raw material ratios, the A-site (0.7:0.3), B-site (2:1), and X-site (4:1) ratios in Example 3 conform to the formation rules of perovskite. Comparative Example 1 has a single A-site and an excessively low B-site ratio; Comparative Example 2 has a single X-site and an excessively high B-site ratio; and Comparative Example 3 contains lead and has a single B-site ratio, thus ensuring lattice matching. In the inert gas treatment, Example 3 reduced the oxygen content to 0.8 ppm and maintained it throughout the process. Comparative Example 1 had no protection, Comparative Example 2 had insufficient replacement and was disrupted midway, and Comparative Example 3 had no protection, thus avoiding oxidation and deterioration of the raw materials and ensuring the purity of the reaction. Regarding the ball milling parameters, Example 3 used multi-stage grinding balls in a 3:4:1 ratio, a ball-to-material ratio of 8:1, a rotation speed of 400 rpm, and a milling time of 8 hours. Comparative Example 1 used a single ball, a low ball-to-material ratio, a low rotation speed, and a short milling time; Comparative Example 2 used a single ball, a high rotation speed, and a short milling time; and Comparative Example 3 used a low ball-to-material ratio and an excessively long milling time. These methods ensured that the raw materials reacted more thoroughly under sufficient mechanical force, resulting in finer and more uniform particle size. For washing and drying, Example 3 underwent three washes (solid-to-liquid ratio 1:15) and vacuum drying at 80°C for 6 hours. Compared to the fewer washes and ordinary drying of Comparative Example 1, the short ultrasonic treatment and low-speed centrifugation of Comparative Example 2, and the water washing and natural air drying of Comparative Example 3, these methods effectively removed unreacted raw materials and impurities, preventing structural hydrolysis. Therefore, the lead-free perovskite material obtained in Example 3 has high purity, a complete structure, uniform particle distribution, no oxidized impurities, meets lead-free standards, and exhibits stable and reliable performance.

[0104] Beneficial effects corresponding to Example 4

[0105] Compared with Comparative Examples 1, 2, and 3, Example 4 exhibits significant advantages. Regarding the raw material ratio, the proportions of A-site (0.1:0.9), B-site (0.5:1), and X-site (2:1) in Example 4 are reasonable. In Comparative Example 1, the A-site ratio is too low and the B-site ratio is too high; in Comparative Example 2, the X-site ratio is too low and the B-site ratio is too high; and in Comparative Example 3, the X-site ratio is reversed, thus ensuring the integrity of the perovskite structure. In the inert gas treatment, Example 4 controls the oxygen content below 0.9 ppm, while Comparative Example 1 lacks protection, Comparative Example 2 suffers from insufficient replacement and midway destruction, and Comparative Example 3 lacks protection. This prevents the oxidation of the raw materials and ensures the smooth progress of the reaction. Regarding the ball milling parameters, Example 4 used multi-stage grinding balls in a 4:2:1 ratio, a ball-to-material ratio of 9:1, a rotation speed of 600 rpm, and a milling time of 4 hours. Comparative Example 1 used a single ball, a low ball-to-material ratio, a low rotation speed, and a short milling time; Comparative Example 2 used a single ball, a high rotation speed, and a short milling time; and Comparative Example 3 used a low ball-to-material ratio and an excessively long milling time. These methods ensured uniform mixing of the raw materials, thorough reaction, and good particle refinement. For washing and drying, Example 4 underwent three washes (solid-to-liquid ratio 1:11), 220W ultrasonication, 3800 rpm centrifugation, and 60°C vacuum drying for 12 hours. Comparative Example 1 underwent fewer washes and ordinary drying; Comparative Example 2 underwent short ultrasonication and low-speed centrifugation; and Comparative Example 3 underwent water washing and natural air drying. These methods effectively removed impurities and prevented structural damage. Therefore, the lead-free perovskite material obtained in Example 4 has high purity, good crystallinity, and meets the lead-free characteristics standard, exhibiting superior performance compared to the products of the comparative examples.

[0106] Beneficial effects corresponding to Example 5

[0107] Compared with Comparative Examples 1, 2, and 3, Example 5 showed significant beneficial effects. Regarding the raw material ratios, Example 5 exhibited a harmonious ratio of A-site (0.9:0.1), B-site (1.2:1), and X-site (3.5:1), while Comparative Example 1 had a single A-site and an unbalanced B-site; Comparative Example 2 had a single X-site and an excessively high B-site ratio; and Comparative Example 3 contained lead and had an abnormal X-site ratio. This ensured the stability and integrity of the perovskite lattice. In the inert gas treatment, Example 5 controlled the oxygen content below 0.8 ppm and maintained a good seal, while Comparative Example 1 lacked protection, Comparative Example 2 had insufficient replacement and leakage, and Comparative Example 3 lacked protection. This prevented the oxidation of the raw materials and ensured the purity of the reaction. Regarding the ball milling parameters, Example 5 used multi-stage grinding balls in a 3:4:1 ratio, a ball-to-material ratio of 11:1, a rotation speed of 550 rpm, and a milling time of 7 hours. Comparative Example 1 used a single ball, a low ball-to-material ratio, a low rotation speed, and a short milling time; Comparative Example 2 used a single ball, a high rotation speed, and a short milling time; and Comparative Example 3 used a low ball-to-material ratio and an excessively long milling time. These methods ensured thorough reaction of the raw materials under sufficient mechanical action, resulting in uniformly fine particles. For washing and drying, Example 5 underwent three washes (solid-to-liquid ratio 1:13), 280W ultrasonication, 4500 rpm centrifugation, and 75°C vacuum drying for 7 hours. Comparative Example 1 used fewer washes and ordinary drying; Comparative Example 2 used short ultrasonication and low-speed centrifugation; and Comparative Example 3 used water washing and natural air drying. These methods effectively removed impurities and prevented structural damage. Therefore, the lead-free perovskite powder obtained in Example 5 has high purity, high crystallinity, and is free of impurities, meeting lead-free requirements and exhibiting stable performance.

[0108] Beneficial effects corresponding to Example 6

[0109] Example 6 demonstrates significant advantages over Comparative Examples 1, 2, and 3. Regarding the raw material ratios, Example 6 exhibits a scientifically sound ratio of A-site (0.4:0.6), B-site (1.8:1), and X-site (3.2:1). Comparative Example 1 suffers from a single A-site and an excessively low B-site ratio; Comparative Example 2 suffers from a single X-site and an excessively high B-site ratio; and Comparative Example 3 contains lead and has an inverted X-site ratio. This ensures the formation conditions for the perovskite structure. In the inert gas treatment, Example 6 reduces the oxygen content to below 0.9 ppm and maintains it throughout the process. Comparative Example 1 lacks protection, Comparative Example 2 suffers from insufficient replacement and midway destruction, and Comparative Example 3 lacks protection. This avoids raw material oxidation and ensures the directionality of the reaction. Regarding the ball milling parameters, Example 6 used multi-stage grinding balls in a 3:3:1 ratio, a ball-to-material ratio of 8:1, a rotation speed of 420 rpm, and a milling time of 7 hours. Comparative Example 1 used a single ball, a low ball-to-material ratio, a low rotation speed, and a short milling time; Comparative Example 2 used a single ball, a high rotation speed, and a short milling time; and Comparative Example 3 used a low ball-to-material ratio and an excessively long milling time. These methods ensured uniform mixing of the raw materials, thorough reaction, and good particle refinement. For washing and drying, Example 6 underwent three washes (solid-to-liquid ratio 1:14), 260W ultrasonication, 3900 rpm centrifugation, and 68°C vacuum drying for 9 hours. Comparative Example 1 underwent fewer washes and ordinary drying; Comparative Example 2 underwent short ultrasonication and low-speed centrifugation; and Comparative Example 3 underwent water washing and natural air drying. These methods effectively removed impurities and prevented structural damage. Therefore, the lead-free perovskite material obtained in Example 6 has high purity, a complete structure, uniform particles, meets lead-free characteristics, and exhibits superior performance compared to the products of the comparative examples.

[0110] Beneficial effects corresponding to Example 7

[0111] Compared with Comparative Examples 1, 2, and 3, Example 7 exhibits significantly beneficial effects. Regarding the raw material ratios, Example 7 shows a balanced proportion of A-site (0.6:0.4), B-site (0.8:1), and X-site (2.8:1). In Comparative Example 1, the A-site ratio is singular and the B-site ratio is too low; in Comparative Example 2, the X-site ratio is singular and the B-site ratio is too high; and in Comparative Example 3, the material contains lead and the X-site ratio is abnormal. This ensures the stability of the perovskite lattice. In the inert gas treatment, Example 7 reduces the oxygen content to below 0.8 ppm through multiple replacements and then seals the container. Comparative Example 1 lacks protection, Comparative Example 2 suffers from insufficient replacement and leakage, and Comparative Example 3 lacks protection. This prevents the oxidation of the raw materials and ensures the purity of the reaction. Regarding the ball milling parameters, Example 7 used a 5:4:1 multi-stage grinding ball ratio of 11:1, a rotation speed of 580 rpm, and a milling time of 5 hours (temperature controlled). Comparative Example 1 used a single ball, a low ball-to-material ratio, a low rotation speed, and a short milling time; Comparative Example 2 used a single ball, a high rotation speed, and a short milling time (due to excessively high temperature); and Comparative Example 3 used a low ball-to-material ratio and an excessively long milling time. These methods ensured that the raw materials reacted fully under suitable conditions, resulting in uniform particle size. For washing and drying, Example 7 underwent three washes (solid-to-liquid ratio 1:11), 230W ultrasonication, 4300 rpm centrifugation, and 62℃ vacuum drying for 11 hours (to stabilize the vacuum). Comparative Example 1 underwent fewer washes and ordinary drying; Comparative Example 2 underwent short ultrasonication and low-speed centrifugation; and Comparative Example 3 underwent water washing and natural air drying. These methods effectively removed impurities and prevented structural damage. Therefore, the lead-free perovskite material obtained in Example 7 has high purity, good crystallinity, stable performance, and meets the lead-free characteristics, surpassing the products of the comparative examples.

[0112] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing lead-free perovskite by ball milling, characterized in that, The method includes: Step 1: Weigh the raw material according to the target perovskite molecular formula, wherein the A-site cation is selected from Cs. + At least one of the formamidinium cations, wherein the B-site cation is selected from Ag. + Bi 3+ Ba 2+ In 3+ At least one of them, the X-position halide ion is selected from I - ,Br - Cl - At least one of them; Step 2: Place the raw materials from Step 1 in an inert gas atmosphere; Step 3: Add the treated raw material and zirconia grinding balls together into a ball mill jar, and perform mechanical ball milling under solvent-free conditions. The ball milling parameters should meet the following requirements: The ball-to-material mass ratio is 5:1 to 15:1, the rotation speed is 200 rpm to 800 rpm, and the ball milling time is 1 hour to 12 hours; Step 4: Wash and dry the ball-milled products sequentially to obtain lead-free perovskite material.

2. The method for preparing lead-free perovskite by ball milling according to claim 1, characterized in that, Step 1: Weigh the raw material according to the target perovskite molecular formula, wherein the A-site cation is selected from Cs. + At least one of the formamidinium cations, wherein the B-site cation is selected from Ag. + Bi 3+ Ba 2+ In 3+ At least one of them, the X-position halide ion is selected from I - ,Br - Cl - At least one of the following, including: Accurately weigh the raw material according to the target perovskite molecular formula ABX3, wherein: The cation at site A is Cs. + With formamidinium cation FA + The mixture has a molar ratio of (0.1–0.9):(0.9–0.1); The cation at the B site is Bi. 3+ With Ag + The mixture has a molar ratio of (0.5~2):1; The halogen ion at the X-position is I. - With Br - A mixture with a molar ratio of (2-4):1; The raw materials include at least three of the following: CsI, formamidin iodide (FAI), BiI3, AgI, and BiBr3.

3. The method for preparing lead-free perovskite by ball milling according to claim 2, characterized in that, Step 2, placing the raw materials from Step 1 in an inert gas atmosphere, including: The weighed raw material is transferred to a vacuum-sealed zirconia grinding jar. High-purity nitrogen is introduced into the glove box to replace the air in the jar, reducing the oxygen content to below 1 ppm. An inert atmosphere is maintained until the ball milling is complete.

4. The method for preparing lead-free perovskite by ball milling according to claim 3, characterized in that, Step 3: Add the treated raw material and zirconia grinding balls together into a ball mill jar, and perform mechanical ball milling under solvent-free conditions, including: The zirconia grinding balls adopt a multi-level particle size combination, including spheres with diameters of 1mm, 2mm and 5mm, with a quantity ratio of (3~5):(2~4):1; The ball milling process is carried out in a planetary ball mill, with the rotation speed controlled at 400-600 rpm, the ball-to-material mass ratio at 8:1-12:1, and the milling time at 4-8 hours.

5. The method for preparing lead-free perovskite by ball milling according to claim 4, characterized in that, Step 4: The ball-milled products are washed and dried sequentially to obtain lead-free perovskite material, including: Add the ball-milled product to anhydrous ethanol and sonicate for 10-30 minutes. After centrifugation, discard the supernatant and repeat 3 times. The washed solid was dried in a vacuum oven at 60–80°C for 6–12 hours to obtain lead-free perovskite powder.

6. The method for preparing lead-free perovskite by ball milling according to claim 5, characterized in that, The ball-milled product was added to anhydrous ethanol and ultrasonically dispersed for 10–30 minutes. After centrifugation, the supernatant was discarded. This process was repeated three times, including: The ball-milled product was mixed with anhydrous ethanol at a solid-liquid mass ratio of 1:10 to 1:15, and ultrasonically treated for 10 to 15 minutes at a power of 200 to 300 W. Centrifuge the dispersion at 3000-5000 rpm for 5-10 minutes and discard the supernatant containing free impurities. Add an equal amount of anhydrous ethanol back to the centrifuged precipitate, repeat the operation twice, and complete a total of 3 washing cycles.