Method for regulating and controlling crystallization of cesium-lead-bromine-based optical active layer by using low-ignition-point nanocrystals

Abstract

The invention provides a method for regulating and controlling crystallization of a cesium-lead-bromine-based optical active layer by using low-ignition-point nanocrystalline, and the method comprises the following steps: taking P-type low-ignition-point nanocrystalline cuprous thiocyanate as a modifier of an optical active layer-carbon electrode interface, so that the extraction and transmission efficiency of current carriers can be remarkably improved; the cuprous thiocyanate nanocrystals are embedded in the cesium-lead-bromine-based optical active layer in a form of gradient distribution from top to bottom to form a gradient hybrid film. The characteristic that cuprous thiocyanate is flammable at low temperature is utilized, micro-combustion occurs in the high-temperature annealing process, the generated micro-flame melting effect can induce grain boundary reconstruction and grain recrystallization, and therefore crystallization of the cesium-lead-bromine-based optical active layer is regulated and controlled. The embedding of the cuprous thiocyanate effectively improves the crystallinity of the cesium-lead-bromine-based optical active layer, the large-grain cesium-lead-bromine-based hybrid optical active layer is successfully prepared, and the stable and efficient carbon-based CsPbBr3 perovskite solar cell is assembled.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite solar cells, and in particular relates to a method for regulating the crystallization of a cesium-lead-bromine-based photoactive layer by utilizing low-ignition-point nanocrystals. Background Art

[0002] Perovskite solar cells (PSCs) have become a research hotspot due to their high conversion efficiency and low fabrication cost. However, organic-inorganic hybrid perovskite materials exhibit poor stability under environmental conditions such as high temperature, humidity, and light, which has limited their further development. Compared with typical organic-inorganic hybrid perovskites, cesium lead bromide (CsPbBr3) materials exhibit excellent moisture and thermal stability, making them a research hotspot in the perovskite field. Carbon-based perovskite cells assembled with CsPbBr3 as the photoactive layer have excellent environmental stability. However, due to the lack of a hole transport layer between the CsPbBr3 photoactive layer and the carbon electrode, the devices exhibit relatively low photoelectric conversion efficiency. Optimizing the CsPbBr3 photoactive layer and its interface with the carbon electrode can further improve interfacial connectivity and enhance their environmental and operational stability.

[0003] Existing technologies for optimizing the CsPb-based photoactive layer and its interface with the carbon electrode vary, primarily including surface passivation, the addition of nanomaterials, the introduction of composite materials, and carbon electrode interface modification. However, these technologies suffer from the following drawbacks: 1. The quality of the CsPb-based photoactive layer limits the device current density, which falls far short of the theoretical current density, hindering further improvements in the photoelectric conversion efficiency of CsPb-based perovskite solar cells; 2. The complex preparation process limits the large-scale production of CsPb-based perovskite solar cells. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for regulating the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals. By embedding cuprous thiocyanate nanocrystals into the cesium lead bromine-based photoactive layer in a top-down gradient distribution, and utilizing the low-temperature flammability of cuprous thiocyanate nanocrystals, a micro-flame is used to reconstruct the grain boundaries during a high-temperature annealing process to regulate the crystallization of the cesium lead bromine-based photoactive layer, thereby preparing a high-efficiency perovskite solar cell with a large-grain cesium lead bromine-based hybrid photoactive layer, further improving the quality of the cesium lead bromine-based photoactive layer film and simplifying the preparation process of the cesium lead bromine-based perovskite solar cell.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A method for regulating the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals comprises the following steps: after spin coating and annealing to obtain a lead bromide coating, spin coating a cesium bromide aqueous solution, and dripping a cuprous thiocyanate nanocrystal dispersion before the spin coating of the cesium bromide aqueous solution is completed, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromine, and performing heat treatment; utilizing the low-temperature flammability of the cuprous thiocyanate nanocrystals to generate micro-combustion during the annealing process, and the generated micro-flame melting effect induces grain boundary reconstruction and grain recrystallization, thereby preparing a cesium lead bromine-based photoactive layer with large grains.

[0007] Furthermore, the specific method of adding the cuprous thiocyanate nanocrystal dispersion is as follows: using a pipette to first inhale 10-15 μl of the cuprous thiocyanate nanocrystal dispersion, then inhale 10-15 μl of air, and finally inhale 90-100 μl of cesium bromide aqueous solution, forming a gradient of cuprous thiocyanate nanocrystals-air thin layer-cesium bromide in the pipette, and before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide.

[0008] Furthermore, the concentration of the cuprous thiocyanate nanocrystal dispersion is 0.6-1.2 mg / ml, and the concentration of the cesium bromide aqueous solution is 0.25 g / ml.

[0009] Furthermore, the dropping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion is 10-15 μl / s.

[0010] Furthermore, the heat treatment conditions are: 250° C. for 4-6 minutes.

[0011] The present invention also provides a cesium lead bromine-based perovskite solar cell, which has a structure of a conductive glass substrate / electron transport layer / cesium lead bromine-based photoactive layer / carbon electrode, wherein the cesium lead bromine-based photoactive layer is prepared by the above-mentioned method of using low-ignition-point nanocrystals to regulate the crystallization of the cesium lead bromine-based photoactive layer.

[0012] The present invention also provides a method for preparing the cesium lead bromine-based perovskite solar cell as described above, the method comprising the following steps:

[0013] (1) Clean the conductive glass and blow dry it for later use;

[0014] (2) Spin coating a precursor solution of an electron transport layer material on a conductive glass and annealing the resulting solution to prepare an electron transport layer.

[0015] (3) spin coating a lead bromide solution mixed with N,N-dimethylformamide and dimethyl sulfoxide on the electron transport layer and performing annealing treatment;

[0016] (4) Then, a cesium bromide aqueous solution is spin-coated, and before the spin-coating of the cesium bromide aqueous solution is completed, a cuprous thiocyanate nanocrystal dispersion is dropped to form a top-down gradient distribution of the cuprous thiocyanate nanocrystals in the cesium lead bromine, and heat treatment is performed to prepare a cesium lead bromine-based photoactive layer;

[0017] (5) Finally, a carbon electrode is formed on the surface by screen printing carbon paste.

[0018] Furthermore, in step (1), the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence.

[0019] Furthermore, in step (2), the precursor solution of the electron transport layer material is a precursor solution of titanium dioxide, the solvent is ethanol, the annealing temperature is 500°C, and the annealing time is 30-40 minutes; or the precursor solution is a precursor solution of tin dioxide, the solvent is ethanol, the annealing temperature is 120°C, and the annealing time is 30-40 minutes.

[0020] Furthermore, in step (3), the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 3:1-6:1, the annealing temperature is 80-100° C., and the annealing time is 30-40 minutes.

[0021] Compared with the prior art, the method of using low-ignition-point nanocrystals to regulate the crystallization of cesium-lead-bromine-based photoactive layers described in the present invention has the following advantages:

[0022] (1) The method of using low-ignition-point nanocrystals to regulate the crystallization of a cesium-lead-bromine-based photoactive layer described in the present invention uses P-type low-ignition-point nanocrystals of cuprous thiocyanate as a modifier for the cesium-lead-bromine-based photoactive layer, and embeds the photoactive layer in a gradient distribution to improve the interface connection between the photoactive layer and the carbon electrode, thereby enhancing the extraction and transmission efficiency of carriers at the interface. Utilizing the low-temperature flammability of cuprous thiocyanate, micro-combustion occurs during high-temperature annealing. The resulting micro-flame melting effect can induce grain boundary reconstruction and grain recrystallization, thereby regulating the crystallization of the cesium-lead-bromine-based photoactive layer. The embedding of cuprous thiocyanate effectively improves the crystallinity of the cesium-lead-bromine-based photoactive layer, successfully preparing a large-grain cesium-lead-bromine-based hybrid photoactive layer and assembling a stable and efficient carbon-based CsPbBr3 perovskite solar cell.

[0023] (2) The method described in this invention for controlling the crystallization of a cesium-lead-bromide-based photoactive layer using low-ignition-point nanocrystals provides a simple method for preparing gradient hybrid thin films. This method has the significant advantages of being simple, controllable, and low-cost, with a simple preparation process. The method has a wide range of applications and is suitable for optimizing other cesium-lead-bromide-based or mixed-phase perovskite-based solar cells.

[0024] (3) The cesium lead bromine-based active layer film prepared by the method of using low-ignition-point nanocrystals to regulate the crystallization of the cesium lead bromine-based photoactive layer described in the present invention has excellent quality, large grains and a single-layer structure, which can improve the extraction and transmission efficiency of carriers.

[0025] (4) The solar cells fabricated using the method described in this invention exhibit outstanding photoelectric conversion performance, with the device's photoelectric conversion efficiency increasing by 24% under the same illumination conditions, demonstrating a promising future for future applications. The device also exhibits outstanding stability, maintaining over 95% of its initial photoelectric conversion efficiency after two hours of exposure to a solar simulator, demonstrating excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 Schematic diagram of micro-flame melting-induced grain boundary reconstruction;

[0028] Figure 2 This is a diagram of the hierarchical structure of cesium lead bromide-based perovskite solar cells;

[0029] Figure 3 is the time-of-flight secondary ion mass spectrum;

[0030] Figure 4 1 is the current density and voltage (JV) characteristic curve of Example 1 and Comparative Example 1.

[0031] Description of reference numerals:

[0032] 1. Conductive glass substrate; 2. Electron transport layer; 3. Cesium lead bromine-based photoactive layer; 4. Carbon electrode. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1 Preparation of cesium lead bromine-based perovskite solar cells

[0036] The preparation method comprises the following steps:

[0037] (1) First, the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol, and deionized water in sequence, and then the conductive glass is blown dry for later use as the conductive glass substrate 1.

[0038] (2) A titanium dioxide precursor solution was prepared, spin-coated on a conductive glass substrate, and annealed at 500° C. for 35 minutes to prepare an electron transport layer 2.

[0039] (3) A lead bromide solution prepared by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1 was then spin-coated on the electron transport layer and annealed at 90°C for 35 minutes.

[0040] (4) Use a pipette to first inhale 15 μl of cuprous thiocyanate nanocrystal dispersion (0.8 mg / ml), then inhale 15 μl of air, and finally inhale 90 μl of cesium bromide aqueous solution (0.25 g / ml), forming a gradient of cuprous thiocyanate nanocrystal-air thin layer-cesium bromide in the pipette. Before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide; and heat treatment is performed at 250°C for 5 minutes. The dripping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion is 10-15 μl / s.

[0041] In this step, a gradient hybrid film of cuprous thiocyanate and CsPbBr3 was prepared. Cuprous thiocyanate nanocrystals formed a top-down gradient distribution in cesium lead bromine. The time-of-flight secondary ion mass spectrometry is shown in Figure 2. Figure 3 As shown, the longitudinal distribution of thiocyanate ions in cesium lead bromide is demonstrated.

[0042] This step utilizes the low-temperature flammability of cuprous thiocyanate nanocrystals to generate micro-combustion during the annealing process. The micro-flame melting effect induces grain boundary reconstruction and grain recrystallization, thereby preparing a cesium lead bromine-based photoactive layer 3 with large grains. The micro-flame melting induces grain boundary reconstruction. Figure 1 shown.

[0043] (5) Finally, a carbon electrode 4 is formed on the surface of the solar cell by screen printing carbon paste to complete the preparation of the solar cell. The structure of the solar cell is conductive glass substrate 1 / electron transport layer 2 / cesium lead bromine photoactive layer 3 / carbon electrode 4 (conductive glass substrate / electron transport layer / cuprous thiocyanate-cesium lead bromine perovskite / carbon electrode). The structure is as follows: Figure 2 shown.

[0044] The battery assembled using the above method achieved a maximum photoelectric conversion efficiency of 10.06% under the irradiation of a solar simulator, and was still able to maintain more than 95% of the initial photoelectric conversion efficiency after 2 hours of irradiation by the solar simulator.

[0045] Comparative Example 1: No cuprous thiocyanate nanocrystal dispersion was added

[0046] (1) First, the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence, and then the conductive glass is blown dry for use as a conductive glass substrate.

[0047] (2) A titanium dioxide precursor solution was prepared, spin-coated on a conductive glass substrate, and annealed at 500° C. for 35 minutes to prepare an electron transport layer.

[0048] (3) A lead bromide solution prepared by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1 was then spin-coated on the electron transport layer and annealed at 90°C for 35 minutes.

[0049] (4) Prepare an aqueous solution of cesium bromide (0.25 g / ml), spin-coat it on the substrate and heat-treat it at 250° C. for 5 minutes. The dripping rate of the aqueous solution of cesium bromide is 10-15 μl / s.

[0050] (5) Finally, a carbon electrode is formed on its surface by screen printing carbon paste to complete the preparation of the solar cell, whose structure is conductive glass substrate / electron transport layer / cesium lead bromide-based perovskite / carbon electrode.

[0051] The battery assembled using the above method achieved a maximum photoelectric conversion efficiency of 8.11% under the irradiation of a solar simulator, and was still able to maintain more than 85% of the initial photoelectric conversion efficiency after 2 hours of irradiation by the solar simulator.

[0052] Comparative Example 2 The concentration of cuprous thiocyanate nanocrystal dispersion is different

[0053] (1) First, the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence, and then the conductive glass is blown dry for use as a conductive glass substrate.

[0054] (2) A titanium dioxide precursor solution was prepared, spin-coated on a conductive glass, and annealed at 500° C. for 35 minutes to prepare an electron transport layer.

[0055] (3) A lead bromide solution prepared by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1 was then spin-coated on the substrate and annealed at 90°C for 35 minutes.

[0056] (4) Use a pipette to first inhale 15 μl of cuprous thiocyanate nanocrystal dispersion (2 mg / ml), then inhale 15 μl of air, and finally inhale 90 μl of cesium bromide aqueous solution (0.25 g / ml), forming a gradient of cuprous thiocyanate nanocrystal-air thin layer-cesium bromide in the pipette. Before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide; and heat treatment is performed at 250°C for 5 minutes. The dripping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion is 10-15 μl / s.

[0057] (5) Finally, a carbon electrode is formed on its surface by screen printing carbon paste to complete the preparation of the solar cell, whose structure is conductive glass substrate / electron transport layer / cuprous thiocyanate-cesium lead bromide perovskite / carbon electrode.

[0058] Comparative Example 3 The amount of cuprous thiocyanate nanocrystal dispersion is different

[0059] (1) First, the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence, and then the conductive glass is blown dry for use as a conductive glass substrate.

[0060] (2) A titanium dioxide precursor solution was prepared, spin-coated on a conductive glass, and annealed at 500° C. for 35 minutes to prepare an electron transport layer.

[0061] (3) A lead bromide solution prepared by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1 was then spin-coated on the electron transport layer and annealed at 90°C for 35 minutes.

[0062] (4) Use a pipette to first inhale 30 μl of cuprous thiocyanate nanocrystal dispersion (0.8 mg / ml), then inhale 15 μl of air, and finally inhale 90 μl of cesium bromide aqueous solution (0.25 g / ml), forming a gradient of cuprous thiocyanate nanocrystal-air thin layer-cesium bromide in the pipette. Before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide; and heat treatment is performed at 250°C for 5 minutes. The dripping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion is 10-15 μl / s.

[0063] (5) Finally, a carbon electrode is formed on its surface by screen printing carbon paste to complete the preparation of the solar cell, whose structure is conductive glass substrate / electron transport layer / cuprous thiocyanate-cesium lead bromide perovskite / carbon electrode.

[0064] Comparative Example 4: The heat treatment time of the cesium lead bromine-based photoactive layer is different

[0065] (1) First, the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence, and then the conductive glass is blown dry for use as a conductive glass substrate.

[0066] (2) A titanium dioxide precursor solution was prepared, spin-coated on a conductive glass, and annealed at 500° C. for 35 minutes to prepare an electron transport layer.

[0067] (3) A lead bromide solution prepared by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1 was then spin-coated on the electron transport layer and annealed at 90°C for 35 minutes.

[0068] (4) Use a pipette to first inhale 15 μl of cuprous thiocyanate nanocrystal dispersion (0.8 mg / ml), then inhale 15 μl of air, and finally inhale 90 μl of cesium bromide aqueous solution (0.25 g / ml), forming a gradient of cuprous thiocyanate nanocrystal-air thin layer-cesium bromide in the pipette. Before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide; and heat treat at 250°C for 10 minutes, with the dripping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion being 10-15 μl / s.

[0069] (5) Finally, a carbon electrode is formed on its surface by screen printing carbon paste to complete the preparation of the solar cell, whose structure is conductive glass substrate / electron transport layer / cuprous thiocyanate-cesium lead bromide perovskite / carbon electrode.

[0070] Table 1 Photovoltaic parameters of the cells in the experimental examples and comparative examples

[0071]

[0072] The photovoltaic parameters of Example 1 and Comparative Example 1 in Table 1 are given by Figure 4 The current density and voltage (JV) characteristic curve is obtained from Table 1 and Figure 4 It can be concluded that compared with the solar cell of comparative example 1 before optimization, the open circuit voltage (V oc ), short-circuit current (J sc ), the fill factor (FF) was improved, and the photoelectric conversion efficiency was increased by 24%.

[0073] Compared with Example 1, the photoelectric conversion efficiency of Comparative Example 2 decreased by 14.6%, indicating that the concentration of the cuprous thiocyanate nanocrystal dispersion will affect the crystallization of the cesium lead bromine-based photoactive layer, thereby affecting the photoelectric conversion efficiency of the battery. Only within the range required by the present invention can better effects be achieved.

[0074] Compared with Example 1, the photoelectric conversion efficiency of Comparative Example 3 decreased by 9.4%, indicating that the amount of cuprous thiocyanate nanocrystal dispersion used will affect the crystallization of the cesium lead bromine-based photoactive layer, thereby affecting the photoelectric conversion efficiency of the battery. Only within the range required by the present invention can better effects be achieved.

[0075] Compared with Example 1, the photoelectric conversion efficiency of Comparative Example 4 decreased by 13.8%, indicating that the heat treatment time of the cesium lead bromine-based photoactive layer will affect the crystallization of the cesium lead bromine-based photoactive layer, thereby affecting the photoelectric conversion efficiency of the battery. Better results can only be obtained within the scope required by the present invention.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for regulating the crystallization of a cesium-lead-bromine-based photoactive layer using low-ignition-point nanocrystals, characterized by: The method comprises the following steps: after spin coating and annealing to obtain a lead bromide coating, spin coating a cesium bromide aqueous solution, and dripping a cuprous thiocyanate nanocrystal dispersion before the spin coating of the cesium bromide aqueous solution is completed, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromine, and performing heat treatment; utilizing the low-temperature flammability characteristics of the cuprous thiocyanate nanocrystals, micro-combustion occurs during the annealing process, and the generated micro-flame melting effect induces grain boundary reconstruction and grain recrystallization, thereby preparing a cesium lead bromine-based photoactive layer with large grains.

2. The method of controlling the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals according to claim 1, characterized in that: The specific method of adding the cuprous thiocyanate nanocrystal dispersion is as follows: using a pipette, first inhale 10-15 μl of the cuprous thiocyanate nanocrystal dispersion, then inhale 10-15 μl of air, and finally inhale 90-100 μl of cesium bromide aqueous solution, forming a gradient of cuprous thiocyanate nanocrystals-air thin layer-cesium bromide in the pipette, and before the spin coating of the cesium bromide aqueous solution is completed, the cuprous thiocyanate nanocrystal dispersion is dropped, so that the cuprous thiocyanate nanocrystals form a top-down gradient distribution in the cesium lead bromide.

3. The method of controlling the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals according to claim 2, characterized in that: The concentration of the cuprous thiocyanate nanocrystal dispersion is 0.6-1.2 mg / ml, and the concentration of the cesium bromide aqueous solution is 0.25 g / ml.

4. The method of controlling the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals according to claim 2, characterized in that: The dripping rate of the cesium bromide aqueous solution and the cuprous thiocyanate nanocrystal dispersion is 10-15 μl / s.

5. The method of controlling the crystallization of a cesium lead bromine-based photoactive layer using low-ignition-point nanocrystals according to claim 1, characterized in that: The heat treatment conditions are: 250°C for 4-6 minutes.

6. A cesium lead bromine-based perovskite solar cell, characterized in that: The structure of the solar cell is a conductive glass substrate / electron transport layer / cesium lead bromine-based photoactive layer / carbon electrode, wherein the cesium lead bromine-based photoactive layer is prepared by the method of using low-ignition-point nanocrystals to regulate the crystallization of the cesium lead bromine-based photoactive layer as described in any one of claims 1 to 5.

7. A method for preparing a cesium lead bromine-based perovskite solar cell according to claim 6, characterized in that: The method comprises the following steps: (1) Clean the conductive glass and blow dry it for later use; (2) Spin coating a precursor solution of an electron transport layer material on a conductive glass and annealing the resulting solution to prepare an electron transport layer. (3) spin coating a lead bromide solution mixed with N,N-dimethylformamide and dimethyl sulfoxide on the electron transport layer and performing annealing treatment; (4) Then, a cesium bromide aqueous solution is spin-coated, and before the spin-coating of the cesium bromide aqueous solution is completed, a cuprous thiocyanate nanocrystal dispersion is dropped to form a top-down gradient distribution of the cuprous thiocyanate nanocrystals in the cesium lead bromine, and heat treatment is performed to prepare a cesium lead bromine-based photoactive layer; (5) Finally, a carbon electrode is formed on the surface by screen printing carbon paste.

8. The method for preparing a cesium lead bromine-based perovskite solar cell according to claim 7, wherein: In step (1), the conductive glass is ultrasonically cleaned using detergent, ethanol, isopropyl alcohol and deionized water in sequence.

9. The method for preparing a cesium lead bromine-based perovskite solar cell according to claim 7, wherein: In step (2), the precursor solution of the electron transport layer material is a precursor solution of titanium dioxide, the solvent is ethanol, the annealing temperature is 500°C, and the annealing time is 30-40 minutes; or the precursor solution is a precursor solution of tin dioxide, the solvent is ethanol, the annealing temperature is 120°C, and the annealing time is 30-40 minutes.

10. The method for preparing a cesium lead bromine-based perovskite solar cell according to claim 7, wherein: In step (3), the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 3:1-6:1, the annealing temperature is 80-100° C., and the annealing time is 30-40 minutes.

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