Method for synthesizing pure α-phase formamidine lead iodine perovskite powder and method for regulating and controlling phase

Abstract

Disclosed in the present invention is a method for regulating and controlling a phase of aqueous synthetic formamidine lead iodine perovskite powder, for use in synthesizing pure α-phase and δ-phase perovskite powder. The method comprises the following steps: first dissolving a lead source in an aqueous acetic acid solution, then adding formamidine acetate, stirring to obtain a clear and transparent solution, adding hydroiodic acid to obtain a large amount of precipitate, filtering and collecting the precipitate, using a detergent to wash the precipitate, then collecting a solid product, placing the solid product in a drying oven, and drying to obtain the perovskite powder. The pure α-phase and δ-phase perovskite powder can be obtained by controlling the type of a washing solvent and a drying temperature.

Description

A method for synthesizing pure α-phase formamidinium lead iodide perovskite powder and regulating the phase Technical Field

[0001] The present invention belongs to the field of optoelectronic functional semiconductor materials, and in particular relates to a method for synthesizing pure α-phase formamidine lead iodine perovskite powder and regulating the physical phase. Background Art

[0002] Halide perovskites, owing to their excellent optoelectronic properties, have been widely used in optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes. Among the halide perovskite family, formamidinium-based lead halide perovskites exhibit superior thermal stability, a more suitable bandgap, and a wider spectral response than other organic-inorganic hybrid perovskite materials. For example, formamidinium-based lead iodide (FAPbI3) exhibits both a room-temperature stable δ phase and a photovoltaic-capable α phase.

[0003] In perovskite solar cells, the perovskite material typically exists in the device as a thin film. A recently developed strategy for preparing thin films using pre-synthesized perovskite microcrystalline powder as a precursor can avoid the stoichiometric deviations and other issues associated with mixing binary halide raw materials. Furthermore, the pre-synthesized powder can be used not only in solution deposition processes but also in evaporation deposition. Aqueous synthesis methods do not rely on organic solvents as reaction solvents, and the synthesized powders are of high purity. By manipulating the phase of formamidinium lead iodide during aqueous synthesis, it is possible to produce a δ-phase powder that is easy to transport and store for long periods, as well as an α-phase powder that can be directly used in the preparation of high-quality perovskite thin films.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide an environmentally friendly strategy for the controllable synthesis of pure α-phase and δ-phase perovskite powders in an aqueous solution system.

[0006] The present invention adopts the following technical solutions:

[0007] A method for synthesizing pure α-phase formamidinium lead iodide perovskite powder comprises the following steps:

[0008] (1) adding a certain amount of lead source to a certain concentration of acetic acid aqueous solution, controlling the temperature to 40-80° C. and stirring to form a clear and transparent solution;

[0009] (2) Weighing an excess of formamidine acetate and adding it to the clear and transparent solution obtained in step (1), maintaining the temperature and stirring rapidly until the solution becomes clear and transparent again;

[0010] (3) adding a certain amount of hydroiodic acid at 50-80° C. to the clear and transparent solution obtained in step (2) to adjust the pH of the mixed solution to <2, maintaining the temperature and rapidly stirring until a large amount of precipitate is generated;

[0011] (4) Adding one or both of ethyl acetate and isopropyl alcohol to the precipitate obtained in step (3) for washing, then filtering and collecting the solid product and placing it in an oven, and drying it to obtain pure α-phase perovskite powder.

[0012] Preferably, the lead source in step (1) comprises one or more of lead oxide, lead carbonate or lead oxalate.

[0013] Preferably, the concentration of the acetic acid aqueous solution in step (1) is 25-100%.

[0014] Preferably, in step (2), the formamidine acetate is in excess of 0-3 times relative to the lead source in terms of molar ratio.

[0015] Preferably, the concentration of hydroiodic acid in step (3) is 45%-55%; the molar ratio of hydroiodic acid to lead source is 1:1-1:8; and the stirring time is 3-24 hours.

[0016] A method for regulating the phase of aqueous synthesis of formamidinium lead iodide perovskite powder comprises the following steps:

[0017] (1) adding a certain amount of lead source to a certain concentration of acetic acid aqueous solution, controlling the temperature to 40-80° C. and stirring to form a clear and transparent solution;

[0018] (2) Weighing an excess of formamidine acetate and adding it to the clear and transparent solution obtained in step (1), maintaining the temperature and stirring rapidly until the solution becomes clear and transparent again;

[0019] (3) adding a certain amount of hydroiodic acid at 50-80° C. to the clear and transparent solution obtained in step (2) to adjust the pH of the mixed solution to <2, maintaining the temperature and rapidly stirring until a large amount of precipitate is generated;

[0020] (4) adding one or both of ethyl acetate and isopropanol to the precipitate obtained in step (3) for washing, and then washing with an organic washing solvent, and then filtering and collecting the solid product and placing it in an oven, and drying it under controlled temperature to obtain pure α-phase or pure δ-phase perovskite powder, wherein the organic washing solvent is one or more of ether, anhydrous ethanol, acetonitrile and acetone.

[0021] Preferably, when pure δ-phase perovskite powder is to be synthesized, the drying temperature in step (4) is 50-125°C.

[0022] Preferably, when pure α-phase perovskite powder is to be synthesized, the drying temperature in step (4) is 130-200°C.

[0023] The present invention proposes a strategy for controllably synthesizing pure α-phase and δ-phase perovskite powders in an aqueous solution system, and uses this strategy to apply the prepared perovskite powders to the preparation of perovskite films with excellent photoelectric response. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1: Microscopic morphology of pure α-phase perovskite powder synthesized in Example 1;

[0025] Figure 2: X-ray diffraction pattern of pure α-phase perovskite powder synthesized in Example 1;

[0026] Figure 3: Microscopic morphology of pure δ-phase perovskite powder synthesized in Example 2;

[0027] Figure 4: X-ray diffraction pattern of pure δ-phase perovskite powder synthesized in Example 2;

[0028] Figure 5: Microscopic morphology of pure α-phase perovskite powder synthesized in Example 3;

[0029] Figure 6: X-ray diffraction pattern of pure α-phase perovskite powder synthesized in Example 3;

[0030] Figure 7: Microscopic morphology of pure δ-phase perovskite powder synthesized in Example 4;

[0031] Figure 8: X-ray diffraction pattern of pure δ-phase perovskite powder synthesized in Example 4. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0033] Example 1: Preparation of pure α-phase perovskite powder

[0034] A. Weigh 9g of lead oxide into a flask. Then, weigh 11ml of 60% acetic acid solution and add it to the flask containing the lead oxide. Stir continuously at 70°C until the solution becomes clear.

[0035] B. Weigh 7 g of formamidine acetate solid and add it to the round-bottom flask. Maintain the temperature at 70°C and continue stirring until the solution becomes clear again.

[0036] C. Heat 20 mL of 55% hydroiodic acid to 70°C and add it to the clear solution obtained in step B. Maintain the temperature at 70°C and continue stirring for 6 hours.

[0037] D. Collect the precipitate obtained in step C by filtration, rinse the filtered solid product 1-3 times with 50 ml of isopropanol, and then dry the solid product in an oven at 50° C. for 24 hours to obtain the final product.

[0038] The product micromorphology is shown in Figure 1, and the X-ray diffraction results are shown in Figure 2. The final product is a microcrystalline α-FAPbI3 powder with no XRD peaks from impurity phases. ICP testing confirmed a purity of 99.996%.

[0039] Example 2: Preparation of pure δ-phase perovskite powder

[0040] A. Weigh 9g of lead oxide into a flask. Then, weigh 11ml of 60% acetic acid solution and add it to the flask containing the lead oxide. Stir continuously at 50°C until the solution becomes clear.

[0041] B. Weigh 7 g of formamidine acetate solid into a round-bottom flask, maintain the temperature at 50°C, and continue stirring until the solution becomes clear again;

[0042] C. Heat 20 mL of 55% hydroiodic acid to 50°C and add it to the clear solution obtained in step B. Maintain the temperature at 50°C and continue stirring for 6 hours.

[0043] D. The precipitate obtained in step C was collected by filtration, and the filtered solid product was rinsed once with 50 ml of ethyl acetate, and then rinsed twice or more with 50 ml of acetonitrile. The solid product was then dried in an oven at 50° C. for 24 h to obtain the final product.

[0044] The product's micromorphology is shown in Figure 3, and the X-ray diffraction results are shown in Figure 4. The final product is a δ-FAPbI3 microcrystalline powder with no XRD peaks from impurity phases. ICP testing confirmed a purity of 99.998%.

[0045] Example 3: Preparation of pure α-phase perovskite powder by phase regulation

[0046] The preparation steps of this embodiment are basically the same as the steps from step A to D of embodiment 2, except that the drying temperature in step D is 160°C.

[0047] The product's micromorphology is shown in Figure 5, and the X-ray diffraction results are shown in Figure 6. The final product is a microcrystalline α-FAPbI3 powder with no XRD peaks from impurity phases. ICP testing confirmed a purity of 99.995%.

[0048] Example 4: Preparation of pure δ-phase perovskite powder by phase regulation

[0049] The preparation steps of this embodiment are basically the same as those of steps A to D in embodiment 1, except that acetone is used for washing 1-3 times in step D.

[0050] The product micromorphology is shown in Figure 7, and the X-ray diffraction results are shown in Figure 8. The final product is a δ-FAPbI3 microcrystalline powder with no XRD peaks from impurity phases. ICP testing confirmed a purity of 99.992%.

Claims

1. A method for synthesizing pure α-phase formamidinium lead iodide perovskite powder, characterized in that: The following steps are involved: (1) adding a certain amount of lead source to a certain concentration of acetic acid aqueous solution, controlling the temperature to 40-80° C. and stirring to form a clear and transparent solution; (2) Weighing an excess of formamidine acetate and adding it to the clear and transparent solution obtained in step (1), maintaining the temperature and stirring rapidly until the solution becomes clear and transparent again; (3) adding a certain amount of hydroiodic acid at 50-80° C. to the clear and transparent solution obtained in step (2) to adjust the pH of the mixed solution to <2, maintaining the temperature and rapidly stirring until a large amount of precipitate is generated; (4) Adding one or both of ethyl acetate and isopropyl alcohol to the precipitate obtained in step (3) for washing, then filtering and collecting the solid product and placing it in an oven, and drying it to obtain pure α-phase perovskite powder.

2. The method according to claim 1, wherein The lead source in step (1) includes one or more of lead oxide, lead carbonate or lead oxalate.

3. The method according to claim 1, wherein The concentration of the acetic acid aqueous solution in step (1) is 25-100%.

4. The method according to claim 1, wherein In terms of molar ratio, the formamidine acetate in step (2) is in excess of 0-3 times relative to the lead source.

5. The method according to claim 1, wherein The concentration of the hydroiodic acid in step (3) is 45%-55%; the molar ratio of the hydroiodic acid to the lead source is 1:1-1:8; and the stirring time is 3-24 hours.

6. A method for regulating the phase of aqueous synthesis of formamidinium lead iodide perovskite powder, characterized in that: The following steps are involved: (1) adding a certain amount of lead source to a certain concentration of acetic acid aqueous solution, controlling the temperature to 40-80° C. and stirring to form a clear and transparent solution; (2) Weighing an excess of formamidine acetate and adding it to the clear and transparent solution obtained in step (1), maintaining the temperature and stirring rapidly until the solution becomes clear and transparent again; (3) adding a certain amount of hydroiodic acid at 50-80° C. to the clear and transparent solution obtained in step (2) to adjust the pH of the mixed solution to <2, maintaining the temperature and rapidly stirring until a large amount of precipitate is generated; (4) adding one or both of ethyl acetate and isopropanol to the precipitate obtained in step (3) for washing, and then washing with an organic washing solvent, and then filtering and collecting the solid product and placing it in an oven, and drying it under controlled temperature to obtain pure α-phase or pure δ-phase perovskite powder, wherein the organic washing solvent is one or more of ether, anhydrous ethanol, acetonitrile and acetone.

7. The method according to claim 6, wherein When pure δ-phase perovskite powder is to be synthesized, the drying temperature in step (4) is 50-125°C.

8. The method according to claim 6, wherein When pure α-phase perovskite powder is to be synthesized, the drying temperature in step (4) is 130-200°C.

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