A method for preparing a perovskite thin film

Abstract

The application discloses an economical and environment-friendly perovskite thin film preparation method, and has the advantages of simple preparation process, no need of expensive and complex equipment, good thin film quality and thin film uniformity, high photoelectric conversion efficiency of a perovskite solar cell based on the method, very little waste of raw materials and organic solvents, all solvents can be reused, maximum utilization of materials is realized, little environmental pollution in the whole process, low energy consumption, and the method can be used for economically and environment-friendly preparation of high-quality perovskite thin films, and plays a great role in efficiency improvement and industrialization popularization of the perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cells, and more particularly to a method for preparing perovskite thin films for large-scale solar cell modules. Background Technology

[0002] Halide perovskites have an elemental composition of ABX3, where A is a methylamine, formamidinium, or cesium cation, B is a lead or tin cation, and X is an iodine, bromine, or chloride anion. They possess suitable band gaps and excellent optical and electrical properties, and their elemental composition is abundant in the Earth's crust. The theoretical limit of perovskite solar cells is higher than that of silicon solar cells, exceeding 31%. They generally only require a preparation temperature below 150°C, resulting in low pollution and low energy consumption, making them the most promising next-generation photovoltaic power generation material.

[0003] Perovskite solar cells have developed rapidly in the last decade or so, with small-area devices achieving photoelectric conversion efficiencies exceeding 25% and large-area devices exceeding 20%. However, several issues need to be addressed for their large-scale commercial application. First, high-efficiency perovskite devices in the laboratory are generally prepared using spin-coating. However, when spin-coating is extended to large-area films, it becomes difficult to guarantee film quality. Similarly, methods like blade coating and vacuum evaporation for preparing large-area perovskite films also suffer from difficulties in controlling film quality and high equipment costs. Second, current methods for preparing perovskite films present environmental pollution and resource waste. For example, the organic solvents used in the preparation process, such as dimethylimide, dimethyl sulfoxide, and the antisolvent chlorobenzene, are all toxic. Furthermore, nearly 90% of the solution from spin-coating cannot be effectively utilized or recycled, posing a significant pollution risk. Finally, the yield of the film preparation process is generally low, requiring sophisticated production equipment and precise control of film thickness and surface morphology. Even small defects and impurities in the film can affect its final efficiency.

[0004] To achieve green and pollution-free production, low economic cost, high production efficiency, high product yield, and large-scale production, the current perovskite thin film preparation methods still need further optimization to realize the economical and environmentally friendly preparation of perovskite thin films and maximize the potential of perovskite materials in photoelectric conversion. Summary of the Invention

[0005] The purpose of this invention is to propose an economical and environmentally friendly method for preparing perovskite thin films, thereby achieving efficient resource utilization, reducing the preparation cost and environmental pollution of perovskite thin films, promoting the commercialization of perovskite solar cells, and maximizing the utilization of solar energy resources.

[0006] To achieve the above objectives, this invention proposes an economical and environmentally friendly method for preparing perovskite thin films, comprising the following steps:

[0007] A: Weigh lead iodide, cesium halide, methylamine halide, and formamidinium halide in a certain proportion, dissolve them in a mixed solution of dimethyl sulfoxide and dimethyl imide, and prepare a precursor solution with a designed stoichiometric ratio. The precursor solution is solution A.

[0008] B: Weigh a certain amount of lead chloride or lead bromide and dissolve it in a specific low-boiling-point solvent to prepare solution B;

[0009] C: After surface treatment, a certain number of conductive glass substrates with prepared transport layers are fixed in an open container;

[0010] D: Add solution A to the container in step C, ensuring the liquid level covers the substrate, heat the solvent and stir; quickly pour solution B into the container, continue stirring until a large number of crystals appear in the solution, stop stirring and cool down to obtain a perovskite precursor film on the substrate surface, remove it and anneal for a certain time to obtain a perovskite film.

[0011] E: Heat the remaining solution from step D to evaporate and condense the low-boiling-point solvent to recover it. Continue stirring until there is no solid residue and recover the precursor solution. Repeat steps C, D, and E to prepare the thin film.

[0012] Preferably, the added cesium halide is one or more of cesium iodide, cesium bromide, and cesium chloride; the added methylamine halide is one or more of methylamine iodide, methylamine bromide, and methylamine chloride; and the added formamidine halide is one or more of formamidine iodide, formamidine bromide, and formamidine chloride.

[0013] Preferably, the concentration of added lead chloride or lead bromide is 0.1~10 g / L.

[0014] Preferably, the low-boiling-point solvent used in step B is a weakly polar and volatile solvent, which includes one or more of isopropanol, ethanol, methanol, and ethyl acetate.

[0015] Preferably, the surface treatment method used in step C is ultraviolet ozone treatment for more than 10 minutes, followed by spin coating of polylactic acid on the surface and annealing at 100°C for 10 minutes.

[0016] Preferably, in step D, the amount of solution B added is 2 to 10 times that of solution A.

[0017] Preferably, in step D, the cooling rate is 20~30°C / min, and the temperature needs to be reduced to 0~5°C.

[0018] Preferably, the annealing temperature in step D is 50~150°C and the annealing time is 4~15 min.

[0019] Preferably, the heating temperature in step E is 80~100°C.

[0020] Preferably, when the molar concentration of lead in the recovered precursor solution is less than 0.4 mol / L, a certain amount of lead iodide is added to restore the concentration to 1 mol / L, and it is used as the solution for preparing the thin film; steps C to E are repeated 2 to 5 times.

[0021] The technical principles employed in this invention are as follows:

[0022] Cesium halides, methylamine halides, formamidinium halides, and lead iodide exhibit high solubility in the polar organic solvents dimethyl sulfoxide (DMSO) and dimethylimide (DMIM), but are almost insoluble in low-polarity solvents such as isopropanol, methanol, ethanol, and ethyl acetate. Adding a large amount of low-polarity solvents like isopropanol to the perovskite precursor solution in DMSO and DMIM can induce a supersaturation of the halides. Lowering the temperature of the solution system at this point promotes the deposition of the halides on the surface-treated substrate according to stoichiometric ratios. Annealing after removal yields the perovskite film. After preparation, heating the solution system allows the low-polarity solvents like isopropanol, due to their extremely low boiling points, to be recovered through condensation and recycling. However, because DMSO and DMIM have higher boiling points, the precipitated halides will redissolve, restoring the perovskite precursor solution to its original state.

[0023] Compared with existing perovskite material preparation technologies, this invention has the following advantages:

[0024] This method enables the simultaneous fabrication of multiple perovskite thin films, resulting in high production efficiency and significant benefits for the future large-scale production of perovskite solar cells. The fabrication method is simple, unlike other methods such as blade coating, inkjet printing, slot coating, and vacuum evaporation, which require expensive and complex equipment. The fabrication process is relatively controllable, producing films with good quality and uniformity. Perovskite solar cells based on this method exhibit high photoelectric conversion efficiency. Waste of raw materials and organic solvents is minimal, as all solvents can be effectively recycled, maximizing material utilization. The entire process has minimal environmental pollution and low energy consumption, enabling the economical and environmentally friendly fabrication of high-quality perovskite thin films. This plays a significant role in improving the efficiency and promoting the industrialization of perovskite solar cells. Attached Figure Description

[0025] Figure 1 Here is a scanning electron microscope image of the surface of the perovskite thin film prepared in Example 1;

[0026] Figure 2 The X-ray diffraction pattern of the perovskite thin film prepared in Example 2;

[0027] Figure 3 The image shows the JV curve of a perovskite solar cell based on the perovskite thin film prepared in Example 2. Detailed Implementation

[0028] Example 1:

[0029] A: Weigh 4.16 g lead iodide, 0.78 g cesium iodide, 0.48 g methylamine iodide, and 0.69 g formamidinium iodide, and dissolve them in 10 mL of a mixed solution of dimethyl sulfoxide and dimethyl imide in a 1:4 ratio to obtain (Cs 0.3 MA 0.3 FA 0.4 PbI3 perovskite precursor solution;

[0030] B: Dissolve 0.01g of lead chloride in 100ml of isopropanol to prepare solution B;

[0031] C: After surface treatment, the prepared SnO2 ITO conductive glass substrate is fixed in the designed open beaker;

[0032] D: (Cs) 0.3 MA 0.3 FA 0.4 The PbI3 perovskite precursor solution was added to an open beaker from step C, with the liquid level covering the conductive glass substrate, and heated to 60°C. Solution B was then rapidly poured into the open beaker, and stirring was continued until a large number of crystals appeared in the solution. Stirring was then stopped and the temperature was lowered to 5°C. (Cs) was then obtained on the substrate surface. 0.3 MA 0.3 FA 0.4 PbI3 perovskite precursor film was removed and annealed at 120°C for 10 minutes to obtain (Cs) 0.3 MA 0.3 FA 0.4 PbI3 perovskite thin films;

[0033] E: Heat the remaining solution from step D to 100°C, evaporate the isopropanol and collect it by condensation, and continue stirring until there is no solid residue to obtain the recovered perovskite precursor solution. Repeat steps C, D and E to prepare a new batch of films, and then stop the process.

[0034] This example yields a well-coated (Cs) 0.3 MA 0.3 FA 0.4 Two batches of 90 PbI3 perovskite films were produced, with average thicknesses of 510 nm (first batch) and 420 nm (second batch, i.e., repeating steps C, D, and E once). After completing steps A to E, the concentration of the perovskite precursor solution was found to be approximately 0.4 mol / L. After adding a certain amount of iodide raw material, the concentration was restored to 1 mol / L, making it suitable for continued use as a solution for film preparation. The recovered isopropanol was free of impurities such as cesium iodide, with a purity greater than 99%. The perovskite films were uniformly deposited on a 5×5 cm substrate. Please refer to [reference needed]. Figure 1 Scanning electron microscopy (SEM) surface scanning revealed that the film has a uniform microstructure without voids, making it very suitable as an absorber layer for perovskite solar cells.

[0035] Example 2:

[0036] A: Weigh 0.909 g of cesium iodide, 1.01 g of lead iodide, and 0.484 g of lead bromide into 5 mL of a DMSO / DMF mixed solvent with a solvent ratio of DMSO:DMF = 4:1 to obtain CsPbI 2.25 Br 0.75 Perovskite precursor solution;

[0037] B: Dissolve 20 mg of lead chloride in 15 mL of ethanol to prepare solution B;

[0038] C: After surface treatment, the prepared SnO2 ITO conductive glass substrate is fixed in the designed open beaker;

[0039] D: CsPbI 2.25 Br 0.75 The perovskite precursor solution was added to an open beaker from step C, ensuring the liquid level covered the conductive glass substrate, and heated to 50°C. Solution B was then rapidly poured into the open beaker, and stirring was continued until a large number of crystals appeared in the solution. Stirring was then stopped, and the solution was cooled to 0°C. CsPbI₂ was obtained on the substrate surface. 2.25 Br 0.75 The perovskite precursor film was removed and annealed at 150°C for 10 minutes to obtain CsPbI. 2.25 Br 0.75 Perovskite thin films;

[0040] E: Heat the remaining solution from step D to 90°C, evaporate the ethanol and collect the condensate, stirring continuously until no solid residue remains, to obtain the recovered CsPbI. 2.25 Br 0.75 After preparing three batches of thin films by repeating steps C, D, and E with the perovskite precursor solution, the process is stopped.

[0041] This example yields coated CsPbI. 2.25 Br 0.75 A total of 80 perovskite films were produced in three batches, with average thicknesses of 510 nm (first batch), 420 nm (second batch, i.e., repeating steps C, D, and E once), and 350 nm (third batch, i.e., repeating steps C, D, and E twice). After completing steps A through E, the concentration of the perovskite precursor solution was found to be approximately 0.4 mol / L. After adding a certain amount of iodide raw material, the concentration was restored to 1 mol / L, making it suitable for continued use as a solution for film preparation. The recovered isopropanol was free of impurities such as cesium iodide, with a purity greater than 99.9%. The perovskite films were uniformly deposited on a 1×1 cm substrate. Please refer to [reference needed]. Figure 2The X-ray diffraction pattern shows strong diffraction peaks and a small full width at half maximum (FWHM), indicating good crystallinity. The film grows perpendicularly to the (100) and (200) planes on the substrate, making it highly suitable as an absorber layer for perovskite solar cells. Please refer to... Figure 3 The perovskite solar cell fabricated based on this thin film achieved a photoelectric conversion efficiency of 18%.

[0042] Comparative Example 1:

[0043] Weigh 0.909 g of cesium iodide, 1.01 g of lead iodide, and 0.484 g of lead bromide into 5 mL of a DMSO / DMF mixed solvent (DMSO:DMF = 4:1). Then dissolve the DMSO in water and add it to a solution containing CsPbI. 2.25 Br 0.75 Perovskite precursor solution. On an ITO substrate with a pre-prepared tin oxide / zinc oxide electron transport layer, the precursor solution was spin-coated to obtain a pre-coated thin film. Chlorobenzene was used as an anti-solvent during the process. A large amount of chlorobenzene was dropped onto the film after 5 seconds of spin-coating, at which point the film turned dark brown. The pre-coated thin film was then placed on a 150°C hot plate to obtain CsPbI₂. 2.25 Br 0.75 Perovskite thin films. This example uses spin coating to prepare perovskite thin films. 90% of the perovskite solution is detached from the substrate during spin coating, and a large amount of toxic anti-solvent chlorobenzene is used, neither of which can be recycled. The yield of films prepared by this method is low; 30 films were obtained after 30 spin coats, with an average thickness of 500 nm. The timing and speed of anti-solvent addition are critical, resulting in a low yield of high-quality films and many rough films that cannot be used to prepare solar cells.

Claims

1. A method for preparing a perovskite thin film, characterized by, The method comprises the following steps: A: a certain amount of lead iodide, cesium halide, methylamine halide and formamidine halide are weighed and dissolved in a mixed solution of dimethyl sulfoxide and dimethylformamide to prepare a precursor solution with a designed stoichiometric ratio, and the precursor solution is the A solution; B: a certain amount of lead chloride or lead bromide is weighed and dissolved in a low-boiling-point solvent to prepare a B solution, wherein the low-boiling-point solvent used in the B step is a weakly polar volatile solvent, and the weakly polar volatile solvent comprises one or more of isopropyl alcohol, ethanol, methanol and ethyl acetate; C: a certain amount of conductive glass substrate with a prepared transport layer is subjected to surface treatment and fixed in an open container; D: the A solution is added to the container in the C step, the liquid level is higher than the substrate, and the solvent is heated and stirred; the B solution is quickly injected into the container, and continuous stirring is performed until a large amount of crystals appear in the solution, the stirring is stopped, and the temperature is lowered, so that a perovskite precursor film is obtained on the surface of the substrate, and the perovskite film is obtained after annealing for a certain period of time; E: the remaining solution in the D step is heated, the low-boiling-point solvent is evaporated and condensed to recover the low-boiling-point solvent, and continuous stirring is performed until no solid residue is left and the precursor solution is recovered, and the steps C, D and E are repeated to prepare the film.

2. The method of claim 1, wherein, The cesium halide added is one or more of cesium iodide, cesium bromide and cesium chloride; the methylamine halide added is one or more of methylamine iodide, methylamine bromide and methylamine chloride; and the formamidine halide added is one or more of formamidine iodide, formamidine bromide and formamidine chloride.

3. The method of claim 1, wherein, The concentration of the added lead chloride or lead bromide is 0.1-10 g / L.

4. The method of claim 1, wherein, The surface treatment method used in the C step is ultraviolet ozone treatment, and the time is greater than 10 min; then, a layer of polylactic acid is spin-coated on the surface, and annealing is performed at 100 ℃ for 10 min.

5. The method of claim 1, wherein, The amount of the B solution added in the D step is 2-10 times that of the A solution.

6. The method of claim 1, wherein, The cooling rate in the D step is 20-30 ℃ / min, and the temperature needs to be reduced to 0-5 ℃.

7. The method of claim 1, wherein, The annealing temperature in the D step is 50-150 ℃, and the annealing time is 4-15 min.

8. The method of claim 1, wherein, The heating temperature in the E step is 80-100 ℃.

9. The method of claim 1, wherein, When the mass concentration of lead in the recovered precursor solution is less than 0.4 mol / L, a certain amount of lead iodide is supplemented to restore the concentration to 1 mol / L, and the solution is continuously used for preparing the film; the number of repetitions of the steps C to E is 2-5 times.

Images