A perovskite thin film stepwise annealing method

Abstract

The application belongs to the technical field of perovskite solar cells, and specifically discloses a perovskite film ladder annealing method, which comprises the following steps: preparing a hole blocking layer on a clean transparent conductive substrate; spin-coating a perovskite light-absorbing layer precursor solution on the conductive substrate and using a vacuum flash technology to extract the excess solution to obtain a perovskite wet film; performing ladder annealing treatment on the perovskite wet film obtained in step S2, placing the perovskite wet film at a position 5 mm above a hot table at 150 DEG C for preheating for 6 s, immediately placing the perovskite wet film on the hot table at 150 DEG C for annealing for 1 min, and then placing the perovskite wet film on a hot table at 100 DEG C for continuous annealing for 6 min. The perovskite film ladder annealing method has the advantages that the ladder annealing avoids the generation of a gray phase of MAPbI3, the crystallization of the perovskite is more uniform, and therefore the short-circuit current density, the open-circuit voltage, the fill factor and the photoelectric conversion efficiency are all improved.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and in particular to a step-by-step annealing method for perovskite thin films. Background Technology

[0002] Perovskite solar cells (PSCs) have become a core candidate for next-generation photovoltaic technology due to their high photoelectric conversion efficiency (PCE), low-cost solution processing characteristics, and tunable bandgap. Among them, the inverted structure (pin type) has become a key direction for industrialization development due to its excellent stability, low-temperature fabrication compatibility, and adaptability to tandem devices. However, this structure still faces two major challenges: 1. Poor interfacial contact and severe nonradiative recombination between the perovskite thin film and the hole transport layer (HTL) lead to reduced carrier extraction efficiency and decreased device stability. 2. Traditional annealing processes (such as hot plate annealing) suffer from uneven temperature gradients and thermal stress concentration, which can easily cause grain boundary defects and phase separation, limiting film quality and device lifespan.

[0003] To address the aforementioned issues, academic research has primarily focused on two approaches: interface engineering and annealing process optimization. For example, strategies such as self-assembled monolayers (SAMs) and multidentate ligand passivation are used to optimize the energy level matching between the hole-blocking layer and the perovskite interface, such as phenylethylamine (PEA). + Modification can reduce the interface defect state density. This includes liquid phase dielectric annealing (LMA) and laser annealing (LA). Liquid phase dielectric annealing suppresses water and oxygen erosion through a uniform temperature field, achieving an efficiency of 23.15% for large-area devices; laser annealing, on the other hand, utilizes high irradiance (>10⁻⁶ ppm) to reduce the interface defect state density. 2 W / cm 2 This enables rapid crystallization.

[0004] Despite significant progress in the aforementioned technologies, the following bottlenecks remain: 1. Traditional thermal annealing relies on overall heating, making it difficult to precisely control the microstructure within the thin film, resulting in uneven grain size (<100nm) and residual PbI2 (>5%). 2. The shift in the conduction / valence band between the hole-blocking layer and the perovskite (>0.3eV) hinders hole extraction, reducing the fill factor and open-circuit voltage. Therefore, it is urgent to achieve simultaneous bottom-up control of the perovskite layer and interface through a simple annealing process, solving all the problems existing in the hole-blocking layer and buried interface, and ultimately achieving long-term stable and efficient inverted PSCs. Summary of the Invention

[0005] The purpose of this invention is to provide a step-by-step annealing method for perovskite thin films, which, for scenarios requiring high flame retardant performance, achieves a synergistic improvement in flame retardant safety, lightweight comfort, and durability of the product through multi-layer flame retardant structure design and process optimization.

[0006] To achieve the above objectives, the present invention provides a step-by-step annealing method for perovskite thin films, comprising the following steps: S1. Prepare a hole blocking layer on a clean transparent conductive substrate; S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film. S3. Perform a stepped annealing process on the perovskite wet film obtained in step S2. Place the perovskite wet film 5 mm above a 150°C hot table for 6 seconds to preheat, then immediately place it on a 150°C hot table for 1 minute to anneal, and then place it on a 100°C hot table for another 6 minutes to anneal.

[0007] Preferably, in step S1, a clean transparent conductive substrate refers to a conductive substrate that has been ultrasonically cleaned with 200-300 mL of deionized water, detergent, and ethanol for 20-30 min, dried in dry air for 5-10 min, and then treated with ultraviolet ozone for 10-25 min, with an ultraviolet ozone intensity of 28-35 mW / cm.

[0008] Preferably, in step S1, preparing the hole-blocking layer refers to: mixing 10-20 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 50-70 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer is obtained by annealing at 140-150℃ for 5-10 min. 0.5-1.0 mg of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid is mixed with ethanol to obtain a self-assembled molecular solution. Then, 50-70 μL of the self-assembled molecular solution is uniformly coated onto the nickel oxide hole-blocking layer, and then annealed at 80-100℃ for 5-10 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0009] Preferably, in step S2, the perovskite light-absorbing layer precursor solution refers to the solution of 1.2~2.0 mmol lead iodide, 1.5~2.0 mmol formamidin hydroiodate, 0.05~0.1 mmol cesium iodide, 0.1~1.5 mmol methylammonium iodide and 0.5~0.9 mmol methylammonium chloride dissolved in 1 mL of organic solvent.

[0010] Preferably, the organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 5:1 to 9:1.

[0011] The advantages and beneficial effects of the above-mentioned step-annealing method for perovskite thin films in this invention are as follows: 1. This invention employs a stepped preheating and annealing process: first, the wet film is preheated at high temperature to induce uniform nucleation of perovskite crystals; then, the main annealing step is implemented to promote directional grain growth. This process significantly improves the crystallization quality of the thin film and reduces the density of bulk and interface defects by optimizing crystallization kinetics; thereby improving the interfacial contact characteristics between the hole blocking layer and the perovskite layer and enhancing charge extraction efficiency; ultimately, it improves the stability of the device's buried interface, suppresses phase separation caused by ion migration, and extends the working life of the inverted perovskite solar cell.

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0013] Figure 1 The results are the performance test results of Example 1 and Comparative Examples 1-3, where A is the short-circuit current density, B is the open-circuit voltage, C is the fill factor, and D is the photoelectric conversion efficiency. Figure 2 In the diagram, A represents the non-uniform gray phase of MAPbI3, and B represents the uniformly crystalline black phase of FAMAPbI3. Figure 3 XRD patterns of Example 1 and Comparative Examples 1-3; Figure 4 for Figure 3 Enlarged XRD pattern; Figure 5 The images shown are SEM images of Example 1 and Comparative Examples 1-3, where A is Comparative Example 1, B is Comparative Example 2, C is Comparative Example 3, and D is Example 1. Detailed Implementation

[0014] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0016] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0017] Example 1 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0018] A clean transparent conductive substrate is defined as a substrate that has been ultrasonically cleaned sequentially with 200 mL of deionized water, detergent, and ethanol for 30 min, dried in dry air for 5 min, and then treated with ultraviolet ozone for 15 min with an ultraviolet ozone intensity of 30 mW / cm.

[0019] The preparation of the hole-blocking layer involves mixing 15 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 60 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 150°C for 5 min. 0.5 mg of Me-4Pacz molecules ((4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid) was mixed with ethanol to obtain a self-assembled molecular solution. 70 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 100°C for 5 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0020] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0021] The perovskite light-absorbing layer precursor solution is defined as follows: 1.5 mmol lead iodide, 2.0 mmol formamidin hydroiodate, 0.1 mmol cesium iodide, 0.5 mmol methyl ammonium iodide, and 0.6 mmol methyl ammonium chloride are dissolved in 1 mL of organic solvent.

[0022] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, with a molar ratio of dimethylamide to dimethyl sulfoxide of 6:1. The perovskite light-absorbing layer precursor solution is a FAMACsPbI3 ternary system perovskite precursor solution.

[0023] S3. Perform a stepped annealing process on the perovskite wet film obtained in step S2. Place the perovskite wet film 5 mm above a 150°C hot table for 6 seconds to preheat, then immediately place it on a 150°C hot table for 1 minute to anneal, and then place it on a 100°C hot table for another 6 minutes to anneal.

[0024] Example 2 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0025] A clean transparent conductive substrate is defined as a substrate that has been ultrasonically cleaned with 250 mL of deionized water, detergent, and ethanol for 25 minutes, dried in dry air for 8 minutes, and then treated with ultraviolet ozone for 20 minutes. The intensity of the ultraviolet ozone light is 32 mW / cm.

[0026] The preparation of the hole-blocking layer involves mixing 15 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 50 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 140°C for 10 min. 1.0 mg of Me-4Pacz molecules were mixed with ethanol to obtain a self-assembled molecular solution. 60 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 90°C for 10 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0027] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0028] The perovskite light-absorbing layer precursor solution is defined as follows: 1.8 mmol lead iodide, 1.5 mmol formamidin hydroiodate, 0.08 mmol cesium iodide, 0.8 mmol methyl ammonium iodide, and 0.5 mmol methyl ammonium chloride are dissolved in 1 mL of organic solvent.

[0029] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 7:1.

[0030] S3. Perform a stepped annealing process on the perovskite wet film obtained in step S2. Place the perovskite wet film 5 mm above a 150°C hot table for 6 seconds to preheat, then immediately place it on a 150°C hot table for 1 minute to anneal, and then place it on a 100°C hot table for another 6 minutes to anneal.

[0031] Example 3 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0032] A clean transparent conductive substrate is prepared by sequentially ultrasonically cleaning the conductive substrate with 300mL of deionized water, detergent, and ethanol for 20 minutes, drying it in dry air for 5 minutes, and then treating it with ultraviolet ozone for 25 minutes. The ultraviolet ozone intensity is 35mW / cm.

[0033] The preparation of the hole-blocking layer involves mixing 10 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 60 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 145°C for 8 min. 0.5 mg of Me-4Pacz molecules were mixed with ethanol to obtain a self-assembled molecular solution. 50 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 80°C for 8 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0034] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0035] The perovskite light-absorbing layer precursor solution is defined as follows: 2 mmol lead iodide, 1.8 mmol formamidin hydroiodate, 0.1 mmol cesium iodide, 1.1 mmol methylammonium iodide and 0.8 mmol methylammonium chloride are dissolved in 1 mL of organic solvent.

[0036] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 8:1.

[0037] S3. Perform a stepped annealing process on the perovskite wet film obtained in step S2. Place the perovskite wet film 5 mm above a 150°C hot table for 6 seconds to preheat, then immediately place it on a 150°C hot table for 1 minute to anneal, and then place it on a 100°C hot table for another 6 minutes to anneal.

[0038] Comparative Example 1 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0039] A clean transparent conductive substrate is defined as a substrate that has been ultrasonically cleaned sequentially with 200 mL of deionized water, detergent, and ethanol for 30 min, dried in dry air for 5 min, and then treated with ultraviolet ozone for 15 min with an ultraviolet ozone intensity of 30 mW / cm.

[0040] The preparation of the hole-blocking layer involves mixing 15 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 60 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 150°C for 5 min. 0.5 mg of Me-4Pacz molecules were mixed with ethanol to obtain a self-assembled molecular solution. 70 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 100°C for 5 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0041] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0042] The perovskite light-absorbing layer precursor solution is defined as follows: 1.5 mmol lead iodide, 2.0 mmol formamidin hydroiodate, 0.1 mmol cesium iodide, 0.5 mmol methyl ammonium iodide, and 0.6 mmol methyl ammonium chloride are dissolved in 1 mL of organic solvent.

[0043] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 6:1.

[0044] S3. Anneal the perovskite wet film obtained in step S2 by placing it on a 100°C hot plate for annealing for 7 minutes.

[0045] Comparative Example 2 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0046] A clean transparent conductive substrate is defined as a substrate that has been ultrasonically cleaned sequentially with 200 mL of deionized water, detergent, and ethanol for 30 min, dried in dry air for 5 min, and then treated with ultraviolet ozone for 15 min with an ultraviolet ozone intensity of 30 mW / cm.

[0047] The preparation of the hole-blocking layer involves mixing 15 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 60 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 150°C for 5 min. 0.5 mg of Me-4Pacz molecules were mixed with ethanol to obtain a self-assembled molecular solution. 70 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 100°C for 5 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0048] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0049] The perovskite light-absorbing layer precursor solution is defined as follows: 1.5 mmol lead iodide, 2.0 mmol formamidin hydroiodate, 0.1 mmol cesium iodide, 0.5 mmol methyl ammonium iodide, and 0.6 mmol methyl ammonium chloride are dissolved in 1 mL of organic solvent.

[0050] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 6:1.

[0051] S3. Anneal the perovskite wet film obtained in step S2 by placing it on a hot plate at 150°C for 7 minutes.

[0052] Comparative Example 3 A step-type annealing method for perovskite thin films includes the following steps: S1. A hole blocking layer is prepared on a clean, transparent conductive substrate.

[0053] A clean transparent conductive substrate is defined as a substrate that has been ultrasonically cleaned sequentially with 200 mL of deionized water, detergent, and ethanol for 30 min, dried in dry air for 5 min, and then treated with ultraviolet ozone for 15 min with an ultraviolet ozone intensity of 30 mW / cm.

[0054] The preparation of the hole-blocking layer involves mixing 15 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 60 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer was obtained by annealing at 150°C for 5 min. 0.5 mg of Me-4Pacz molecules were mixed with ethanol to obtain a self-assembled molecular solution. 70 μL of the self-assembled molecular solution was then uniformly coated onto the nickel oxide hole-blocking layer and annealed at 100°C for 5 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

[0055] S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film.

[0056] The perovskite light-absorbing layer precursor solution is defined as follows: 1.5 mmol lead iodide, 2.0 mmol formamidin hydroiodate, 0.1 mmol cesium iodide, 0.5 mmol methyl ammonium iodide, and 0.6 mmol methyl ammonium chloride are dissolved in 1 mL of organic solvent.

[0057] The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 6:1.

[0058] S3. Anneal the perovskite wet film obtained in step S2. Place the perovskite wet film on a 150°C hot plate for annealing for 1 minute, and then transfer it to a 100°C hot plate for annealing for 6 minutes.

[0059] The performance of the samples obtained by the annealing methods of Example 1 and Comparative Examples 1-3 was tested.

[0060] like Figure 1 As shown in Figure A, the Jsc (short-circuit current density) of Comparative Example 1 (Control Group A) is concentrated in the range of 24.5~25.0 mA / cm². 2The range; the Jsc of Comparative Example 2 (Control Group B) and Comparative Example 3 (Control Group C) showed a decreasing trend, while the Jsc of Example 1 (preferred) rebounded to a level close to that of Control Group A. For example... Figure 1 As shown in Figure B, the Voc (open-circuit voltage) of Comparative Example 1 (Control Group A) was approximately 1.65~1.70V; the Voc of Comparative Example 2 (Control Group B) was significantly increased; and in Comparative Example 3 (Control Group C), the Voc of Example 1 (preferred) increased again and reached the highest level among all groups. Figure 1 As shown in Figure C, the fill factor (FF) of Comparative Example 1 (Control Group A) is approximately 80%; the FFs of Comparative Example 2 (Control Group B) and Comparative Example 3 (Control Group C) fluctuate slightly, while the FF of Example 1 (preferred) remains close to the level of Control Group A. Figure 1 As shown in Figure D, the PCE (photoelectric conversion efficiency) of Comparative Example 1 (Control Group A) is approximately 25%; the PCE of Comparative Example 2 (Control Group B) increases significantly, while that of Comparative Example 3 (Control Group C) decreases, and the PCE of Example 1 (Preferred) reaches the highest value among all groups.

[0061] Example 1 showed the best performance in terms of Voc and PCE. Combined with the stability of Jsc and FF, it can be seen that its overall performance is better than that of Comparative Examples 1-3.

[0062] Comparative Example 2: Annealed at 150℃ for 7 min, due to the ternary perovskite solar cell (Cs 0.05 MA 0.05 FA 0.9 PbI 2.96 Cl 0.04 ) contains MA + Cations readily lead to metamorphic activity (MA) within perovskites. + The movement of components leaves empty spaces, resulting in a decrease in the device fill factor.

[0063] Comparative Example 1: Annealing at 100℃ for 7 min resulted in incomplete evaporation of the solvent in the system, leading to the formation of incorrect phases and thus reducing the fill factor and short-circuit current.

[0064] Comparative Example 3: Annealing at 150℃ for 1 minute followed by 100℃ for 10 minutes allowed for rapid crystallization and avoided the defects caused by the first two annealing methods. However, the high temperature of 150℃ resulted in excessive crystallization of Cs. 0.05 MA 0.05 FA 0.9 PbI 2.96 Cl 0.04 It decomposes into the gray phase of MAPbI3, rather than the target Cs. 0.05 MA 0.05 FA 0.9 PbI 2.96 Cl 0.04This phase means that if a sub-cell containing the gray phase of MAPbI3 is detected during testing, the current density of that sub-cell will drop sharply.

[0065] This invention first preheats the perovskite wet film at a height of 5 mm above the 150°C hot stage for 6 seconds to evaporate most of the solvent. Since it does not directly contact the hot stage, it allows the perovskite wet film to pre-crystallize Cs at a lower temperature. 0.05 MA 0.05 FA 0.9 PbI 2.96 Cl 0.04 ( Figure 2 (B), and then the perovskite wet film was placed on a hot stage at 150℃ for annealing for 1 min for rapid crystallization and evaporation of all solvent, and then moved to a hot stage at 100℃ for annealing for another 6 min. Because the perovskite layer promotes the formation of the FAPbI3 black phase ( Figure 2 Therefore, the perovskite crystals are more uniform, resulting in a higher short-circuit current density (J / L) in the complete device. SC ), open circuit voltage (V) OC The fill factor (FF) and photoelectric conversion efficiency (PCE) have all been improved.

[0066] Figure 3 The XRD patterns of Example 1 (preferred), Comparative Example 1 (control group A), Comparative Example 2 (control group B), and Comparative Example 3 (control group C) show that their perovskite phase (such as the FAMACsPbI3 black phase) has the highest crystallinity and best purity. This effectively induces uniform nucleation and directional growth of perovskite crystal nuclei. It significantly improves the crystallinity and phase purity of the thin film, laying the foundation for obtaining high-efficiency and stable perovskite solar cells.

[0067] Figure 4 for Figure 3 The magnified XRD pattern shows the (110) peak, a characteristic diffraction peak of the perovskite black phase. Its intensity and peak shape are core indicators for evaluating film quality. The XRD pattern clearly verifies the superiority of the stepped annealing process: it effectively promotes the preferential growth of the perovskite (110) crystal plane and significantly improves the crystallinity and purity of the black phase. Compared with other annealing processes, the preferred group (Example 1 group) has higher peak intensity and better peak shape, directly proving its significant effect in suppressing impurities and optimizing grain quality, providing strong structural support for obtaining efficient and stable perovskite solar cells.

[0068] Figure 5 The SEM images are from Example 1 and Comparative Examples 1-3. Figure 5 Comparative Example 1 (A): The grains are small and randomly distributed, with a large number of grain boundaries and pores, and the film coverage is low, indicating that there are too many nuclei and insufficient growth during the crystallization process. Figure 5Comparative Example 2 (B): The grain size has increased, but there are still many isolated small grains and obvious grain boundary gaps, and the film uniformity is generally poor. Figure 5 In Comparative Example 3 (C), the grains grow further, the grain boundaries decrease, and the coverage increases, but some incompletely fused grains and a small number of pores can still be seen. Figure 5 Example D (as in Example 1) shows the largest and most uniform grain size, significantly reduced grain boundaries, highest film coverage, and a smooth, dense surface with almost no obvious pores or defects. SEM images visually verify the superiority of the stepped annealing process from a microscopic morphology perspective: it effectively induces uniform nucleation and full growth of perovskite grains, significantly reducing grain boundaries and pores, and improving film density and coverage. These excellent morphological characteristics are a crucial structural basis for achieving high-efficiency and stable perovskite solar cells.

[0069] Therefore, the present invention adopts the above-mentioned step-by-step annealing method for perovskite thin films. By step-by-step annealing, the generation of gray phase of MAPbI3 is avoided, so the crystallization of perovskite is more uniform, thereby improving the short-circuit current density, open-circuit voltage, fill factor and photoelectric conversion efficiency.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A step-by-step annealing method for perovskite thin films, characterized in that, Includes the following steps: S1. Prepare a hole blocking layer on a clean transparent conductive substrate; S2. Spin-coat the perovskite light-absorbing layer precursor liquid onto the conductive substrate, and use vacuum flash evaporation technology to extract the excess solution to obtain a perovskite wet film. S3. Perform a stepped annealing process on the perovskite wet film obtained in step S2. Place the perovskite wet film 5 mm above a 150°C hot table for 6 seconds to preheat, then immediately place it on a 150°C hot table for 1 minute to anneal, and then place it on a 100°C hot table for another 6 minutes to anneal.

2. The step-annealing method for perovskite thin films according to claim 1, characterized in that: In step S1, a clean transparent conductive substrate refers to a conductive substrate that is ultrasonically cleaned with 200-300 mL of deionized water, detergent, and ethanol for 20-30 minutes, dried in dry air for 5-10 minutes, and then treated with ultraviolet ozone for 10-25 minutes. The intensity of the ultraviolet ozone light is 28-35 mW / cm.

3. The step-annealing method for perovskite thin films according to claim 1, characterized in that: In step S1, preparing the hole-blocking layer refers to: mixing 10-20 mg of nickel oxide with ultrapure water to obtain a nickel oxide solution, and then uniformly coating 50-70 μL of the nickel oxide solution onto a 1.5 × 1.5 cm surface. 2 On a conductive substrate, a nickel oxide hole-blocking layer is obtained by annealing at 140-150℃ for 5-10 min. 0.5-1.0 mg of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid is mixed with ethanol to obtain a self-assembled molecular solution. Then, 50-70 μL of the self-assembled molecular solution is uniformly coated onto the nickel oxide hole-blocking layer, and then annealed at 80-100℃ for 5-10 min to obtain a nickel oxide-self-assembled molecular composite hole-blocking layer.

4. The step-annealing method for perovskite thin films according to claim 1, characterized in that: In step S2, the perovskite light-absorbing layer precursor solution refers to the solution of 1.2-2.0 mmol lead iodide, 1.5-2.0 mmol formamidin hydroiodate, 0.05-0.1 mmol cesium iodide, 0.1-1.5 mmol methylammonium iodide and 0.5-0.9 mmol methylammonium chloride dissolved in 1 mL of organic solvent.

5. The step-annealing method for perovskite thin films according to claim 4, characterized in that: The organic solvent is a mixed solution of dimethylamide and dimethyl sulfoxide, wherein the molar ratio of dimethylamide to dimethyl sulfoxide is 5:1 to 9:1.

Images