A method for synthesizing a perovskite microcrystal powder

Abstract

The application discloses a synthesis method of perovskite microcrystal powder, which comprises the following steps: (1) adding a certain amount of inorganic lead source into an acetic acid aqueous solution with a certain concentration, controlling the temperature and stirring to form a clear and transparent solution; (2) weighing an excess of monovalent cation acetate and adding the monovalent cation acetate into the clear and transparent solution obtained in the step A, rapidly stirring until the solution is clear and transparent again; (3) maintaining the same reaction temperature as that in the step (1), introducing halogen elements into the clear and transparent solution obtained in the step (2) at a uniform speed drop by drop, then adding an acidity regulator, adjusting the pH of the mixed solution to be less than 2, and then rapidly stirring until a large amount of precipitate is generated; and (4) adding an organic washing solvent into the precipitate obtained in the step (3), washing the precipitate for more than three times, then filtering and collecting the solid product, and placing the solid product in an oven to obtain the perovskite microcrystal powder after drying.

Description

Technical Field

[0001] This invention discloses a method for synthesizing perovskite microcrystalline powder, which belongs to the field of optoelectronic functional semiconductor materials. Background Technology

[0002] Halide perovskite materials (structural formula abbreviated as ABX3, where A is a monovalent cation such as formamidinium, methylamine, or cesium, B is a divalent metal cation such as lead or tin, and X is a halogen element) have been widely used in optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes due to their excellent photoelectric properties. Among the halide perovskite family of materials, formamidinium-based and cesium-based halide perovskite materials exhibit better thermal stability compared to other organic-inorganic hybrid perovskite materials. In particular, lead formamidinium iodide (FAPbI3) and lead cesium iodide (CsPbI3) possess suitable band gaps and spectral response ranges. Solar cells based on CsPbI3 have achieved photoelectric conversion efficiencies exceeding 20%, while perovskite solar cells based on FAPbI3 have achieved photoelectric conversion efficiencies exceeding 25%.

[0003] Currently, in perovskite solar cells, perovskite materials are typically present in the device as thin films using solution deposition technology. The traditional method involves mixing organic halides (such as formamidinium hydroiodide) and metal halides (such as lead iodide) in a specific solvent, and then preparing the perovskite thin film using techniques such as spin coating, spraying, or printing. In recent years, a strategy using pre-synthesized perovskite microcrystalline powder for re-dissolution coating has gradually developed. This strategy prepares pure-phase perovskite powder in advance, avoiding problems such as stoichiometric deviations caused by mixing halide raw materials. Simultaneously, since the precipitation and crystallization process of perovskite material is also a purification process, this strategy can use raw materials with lower purity, greatly reducing the dependence of perovskite solar cell fabrication on high-purity raw materials. However, most existing perovskite powder preparation methods are carried out in flammable and volatile organic solvent systems such as alcohols, ethers, and nitriles, which are not conducive to large-scale preparation. Furthermore, since different solvents have different effects on the phases of perovskite powder (usually there are two phases, δ and α), perovskite materials in organic solvent systems often exhibit phase inhomogeneity. Summary of the Invention

[0004] The purpose of this invention is to provide a low-cost strategy for preparing stable and high-purity perovskite microcrystalline powder in an aqueous solution system.

[0005] The present invention adopts the following technical solution ( Figure 1 ):

[0006] (1) Add a certain amount of inorganic lead source to an aqueous solution of acetic acid of a certain concentration, control the temperature and stir to form a clear and transparent solution;

[0007] (2) Weigh out an excess of monovalent cation acetate and add it to the clear and transparent solution obtained in step A. Stir quickly until the solution becomes clear and transparent again.

[0008] (3) Keep the same reaction temperature as in step (1), introduce halogen elements dropwise at a uniform rate into the clear and transparent solution obtained in step (2), then add an acidity regulator to adjust the pH of the mixed solution to <2, and then stir rapidly until a large amount of precipitate is generated.

[0009] (4) Add an organic washing solvent to the precipitate obtained in step (3), wash the precipitate more than 3 times, then filter to collect the solid product and place it in an oven to dry to obtain perovskite microcrystalline powder.

[0010] Preferably, the inorganic lead source in step (1) includes one or more of lead oxide, lead carbonate, lead acetate, or lead oxalate.

[0011] Preferably, the concentration of the acetic acid aqueous solution in step (1) is 10-100%, and the stirring temperature is 20-90℃.

[0012] Preferably, the monovalent cationic acetate in step (2) is one or more of methylamine acetate (MAAc), formamidine acetate (FAAc), or cesium acetate (CsAc), and the methylamine acetate, formamidine acetate, or cesium acetate is in 0-3 times excess (molar ratio) relative to the lead source.

[0013] Preferably, the halogen element in step (3) is one or more of iodine, bromine or chlorine, and the ratio of the halogen element to the lead source is in the range of 1:1 to 1:4 (molar ratio).

[0014] The halogen elements are in the form of one or more of pure halogen elements, halogenated compounds, or aqueous solutions of concentrated hydrohalic acids.

[0015] Preferably, the acidity regulator in step (3) includes one or more of hypophosphite, citric acid, oxalic acid and tartaric acid.

[0016] Preferably, the organic detergent in step (4) includes one or more of dimethyl ether, diethyl ether, methanol, anhydrous ethanol and isopropanol.

[0017] Preferably, the drying temperature in step (4) is 60°C and the drying time is 6-24h.

[0018] This invention proposes a strategy for preparing formamidine-based or cesium-based perovskite microcrystalline powders in an aqueous solution system, and uses this strategy to redissolve and coat the prepared perovskite powders to obtain α-phase perovskite thin films with excellent photoelectric response. Attached Figure Description

[0019] Figure 1 Schematic diagram of the synthesis route for perovskite microcrystalline powder;

[0020] Figure 2 X-ray diffraction pattern of synthesized formamidinium lead iodide (FAPbI3) microcrystalline powder;

[0021] Figure 3 and Figure 4 Microstructure of synthesized δ-phase FAPbI3 microcrystalline powder at different scales;

[0022] Figure 5 XRD pattern of α-phase FAPbI3 thin film prepared using synthesized δ-phase FAPbI3 microcrystalline powder;

[0023] Figure 6 Comparison of IV curves of FAPbI3 solar cells prepared by synthesized δ-phase FAPbI3 microcrystalline powder and those prepared by conventional methods;

[0024] Figure 7 X-ray diffraction pattern of synthesized cesium lead-based (CsPbI2Br) microcrystalline powder;

[0025] Figure 8 Comparison of IV curves of CsPbI2Br solar cells prepared by synthetic CsPbI2Br microcrystalline powder and CsPbI2Br solar cells prepared by conventional methods. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0027] Example 1: Preparation of FAPbI3 microcrystalline powder

[0028] A. Measure 11.64 ml of 20% glacial acetic acid aqueous solution and add it to a round-bottom flask. Place the flask in a heated stirring tank and stir at room temperature.

[0029] B. Weigh 12.7g of lead oxide, pour it into the pre-prepared acetic acid aqueous solution, place it in a heated stirring tank and stir at room temperature for 30 minutes, then raise the temperature to 40℃ and continue stirring until the solution is clear and transparent and there are no visible insoluble substances.

[0030] C. Weigh 5.92g of formamidine acetate solid and add it to a round-bottom flask. Keep the temperature of step B constant and continue stirring until the solution becomes clear and transparent again.

[0031] D. Take 23 ml of 20% hydroiodic acid aqueous solution and add it dropwise at a uniform rate to the clear and transparent solution obtained in step C. Keep the temperature the same as in steps B and C, add hypophosphoric acid, control the pH of the mixed solution to be less than 2, and increase the stirring rate. At this time, a large amount of precipitate can be observed to form.

[0032] E. Collect the precipitate obtained in step D by filtration, then wash the filtered solid product with 30 ml of isopropanol more than 3 times, and then put the solid product into an oven to dry for 24 hours to obtain the final product.

[0033] Product Result Analysis:

[0034] X-ray diffraction results are as follows Figure 2 As shown, the final product is δ-phase FAPbI3 microcrystalline powder. Please refer to... Figure 3 and Figure 4 The microcrystalline powder exhibits a rod-like morphology, with smooth surfaces and no obvious impurities in individual microcrystals. EDX analysis shows that the lead to iodine ratio in the δ-phase FAPbI3 microcrystalline powder conforms to the stoichiometric ratio of Pb:I = 1:3 in perovskite. FAPbI3 films were prepared using this δ-phase FAPbI3 microcrystalline powder, and the films underwent a phase transformation to the α-phase. Please refer to [reference needed]. Figure 5 FAPbI3 solar cells prepared based on the δ-phase FAPbI3 microcrystalline powder exhibit superior performance compared to FAPbI3 solar cells prepared using conventional methods, such as... Figure 6 As shown.

[0035] Example 2: Preparation of CsPbI2Br microcrystalline powder

[0036] A. Measure 8 ml of 90% glacial acetic acid and add it to a round-bottom flask. Place the flask in a heated stirring tank and stir at room temperature.

[0037] B. Weigh 11g of lead carbonate, pour it into the pre-prepared acetic acid aqueous solution, place it in a heated stirring tank and stir at room temperature for 30 minutes, then raise the temperature to 65℃ and continue stirring until the solution is clear and transparent and there are no visible insoluble substances.

[0038] C. Weigh 18g of cesium acetate solid and add it to a round-bottom flask. Keep the temperature of step B constant and continue stirring until the solution becomes clear and transparent again.

[0039] D. Prepare a mixed aqueous solution of potassium iodide and hydrobromic acid with a high concentration (concentration > 70%, molar ratio of iodine to bromine is 2:1). Measure 80 ml of this mixed solution and add it dropwise at a uniform rate to the clear and transparent solution obtained in step C. At the same time, raise the temperature to 90°C and increase the stirring rate. At this time, a large amount of precipitate can be generated.

[0040] E. Collect the precipitate obtained in step D by filtration, then rinse the filtered solid product with 100ml of methanol more than 3 times, and then put the solid product into an oven to dry for 24 hours to obtain the final product.

[0041] Product Result Analysis:

[0042] X-ray diffraction results are as follows Figure 7 As shown, the final product is α-phase CsPbI₂Br microcrystalline powder. Solar cells prepared based on this CsPbI₂Br microcrystalline powder exhibit superior performance compared to CsPbI₂Br solar cells prepared using conventional methods. Figure 8 As shown.

[0043] Example 3: (FA) 0.9 Cs 0.1 Preparation of PbI3 microcrystalline powder

[0044] A. Measure 25 ml of 80% glacial acetic acid and add it to a round-bottom flask. Place the flask in a heated stirring tank and stir at room temperature.

[0045] B. Weigh 25g of lead carbonate, pour it into the pre-prepared acetic acid aqueous solution, place it in a heated stirring tank and stir at room temperature for 30 minutes, then raise the temperature to 60℃ and continue stirring until the solution is clear and transparent and there are no visible insoluble substances.

[0046] C. Weigh 20g of formamidine acetate and 1.04g of solid cesium acetate into a round-bottom flask according to the stoichiometric ratio of formamidine to cesium acetate = 9:1. Keep the temperature of step B constant and continue stirring until the solution becomes clear and transparent again.

[0047] D. Prepare a high-concentration potassium iodide aqueous solution (concentration > 70%). Measure 70 ml of this potassium iodide solution and add it dropwise at a uniform rate to the clear and transparent solution obtained in step C. At the same time, raise the temperature to 80°C, then add oxalic acid to adjust the pH < 1 and increase the stirring rate. At this time, a large amount of precipitate can be generated.

[0048] E. Collect the precipitate obtained in step D by filtration, then rinse the filtered solid product with 100ml of methanol more than 3 times, and then put the solid product into an oven to dry for 24 hours to obtain the final product.

Claims

1. A method for synthesizing perovskite microcrystalline powder, characterized in that, Includes the following steps: (1) A certain amount of inorganic lead source is added to an aqueous acetic acid solution of a certain concentration, the temperature is controlled and the mixture is stirred to form a clear and transparent solution, wherein the concentration of the aqueous acetic acid solution in step (1) is 10-100%, the stirring temperature is 20-90℃, and the inorganic lead source includes one or more of lead oxide, lead carbonate, lead acetate or lead oxalate. (2) Weigh out an excess of monovalent cationic acetate and add it to the clear and transparent solution obtained in step A. Stir quickly until the solution becomes clear and transparent again. (3) Maintain the same reaction temperature as in step (1), introduce halogen elements dropwise at a uniform rate into the clear and transparent solution obtained in step (2), then add an acidity regulator to adjust the pH of the mixed solution to <2, and then stir rapidly until a large amount of precipitate is generated. The acidity regulator includes one or more of hypophosphorous acid, citric acid, oxalic acid and tartaric acid. (4) Add organic washing solvent to the precipitate obtained in step (3), wash the precipitate more than 3 times, then filter and collect the solid product and place it in an oven. After drying, obtain perovskite microcrystalline powder. Dissolve the prepared perovskite powder and coat it to prepare an α-phase perovskite thin film with excellent photoelectric response.

2. The method for synthesizing perovskite microcrystalline powder as described in claim 1, characterized in that, The monovalent cationic acetate mentioned in step (2) is one or more of methylamine acetate, formamidine acetate, or cesium acetate, in which methylamine acetate, formamidine acetate, or cesium acetate is in 0-3 times excess relative to the lead source by a molar ratio.

3. The method for synthesizing perovskite microcrystalline powder as described in claim 1, characterized in that, The halogen element mentioned in step (3) is one or more of iodine, bromine or chlorine, and the molar ratio of the halogen element to the lead source is in the range of 1:1 to 1:

4.

4. The method for synthesizing perovskite microcrystalline powder as described in claim 1, characterized in that, The halogen elements are in the form of one or more of pure halogen elements, halogenated compounds, or aqueous solutions of concentrated hydrohalic acids.

5. The method for synthesizing perovskite microcrystalline powder as described in claim 1, characterized in that, The organic washing solvent mentioned in step (4) includes one or more of dimethyl ether, diethyl ether, methanol, anhydrous ethanol and isopropanol.

6. The method for synthesizing perovskite microcrystalline powder as described in claim 1, characterized in that, The drying temperature in step (4) is 60℃ and the drying time is 6-24h.

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