Perovskite thin film and preparation method, solar cell device

Abstract

This application provides a perovskite thin film, its preparation method, and a solar cell device, belonging to the field of perovskite materials. The preparation method of the perovskite thin film includes: providing a substrate; alternately depositing CsBr and PbBr2 on the substrate, followed by a first annealing treatment to obtain a precursor film; heating the precursor film in a bromine-rich atmosphere, followed by a second annealing treatment to obtain the perovskite thin film; wherein the molar ratio of CsBr to PbBr2 is (1-1.2):1. This method enables the in-situ transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase, thereby obtaining a perovskite thin film with high crystallinity, excellent phase purity, and outstanding photoelectric performance.

Description

Technical Field

[0001] This invention relates to the field of perovskite materials technology, specifically to a perovskite thin film, its preparation method, and a solar cell device. Background Technology

[0002] All-inorganic perovskite CsPbBr3 (approximately 2.3 eV) holds significant promise for applications in high-stability optoelectronic devices due to its excellent thermal and optical stability and suitable bandgap characteristics, particularly for high-stability solar cells and semi-transparent photovoltaic devices. Currently, the preparation of CsPbBr3 thin films mainly includes two methods: solution methods and physical vapor deposition (PVD). While solution methods offer advantages such as low equipment cost and simple processes, they suffer from poor film uniformity and repeatability. In contrast, physical vapor deposition methods, such as co-evaporation and sequential evaporation techniques, can achieve the preparation of perovskite thin films with high uniformity and high density, making them more suitable for industrial production.

[0003] However, in the process of preparing CsPbBr3 thin films by co-evaporation of CsBr and PbBr2 in related technologies, the large difference in vapor pressure between the two materials and the complex reaction kinetics easily lead to the formation of non-ideal phase structures, especially lead-rich intermediate products such as CsPb2Br5. Existing technologies usually suppress or eliminate the formation of the CsPb2Br5 phase by increasing the annealing temperature or adjusting the evaporation ratio, but these methods often cannot completely avoid the formation of this intermediate phase and may lead to poor film crystal quality or compositional deviation. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a perovskite thin film, a preparation method thereon, and a solar cell device. The preparation method of this perovskite thin film enables in-situ transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase, thereby obtaining a perovskite thin film with high crystallinity, excellent phase purity, and outstanding photoelectric performance.

[0005] To achieve the above objectives, in a first aspect, embodiments of this application provide a method for preparing a perovskite thin film, comprising: Provide a base; CsBr and PbBr2 were alternately deposited on the substrate, and the precursor film was obtained by first annealing. The precursor film was heated in a bromine-rich atmosphere, followed by a second annealing treatment to obtain the perovskite film; wherein... The molar ratio of CsBr to PbBr2 is (1-1.2):1.

[0006] Furthermore, the molar ratio of CsBr to PbBr2 is (1-1.1):1.

[0007] Furthermore, the bromine-rich atmosphere includes at least one of CsBr and HBr.

[0008] Furthermore, the heat treatment temperature is 150℃-200℃; and / or, The heat treatment time is 10 min-40 min; and / or, The vacuum degree of the heat treatment is 10. -6 Pa-10 -5 Pa.

[0009] Furthermore, the CsBr deposition thickness is 150nm-300nm.

[0010] Furthermore, the PbBr2 deposition thickness is 200nm-450nm.

[0011] Furthermore, the temperature for the first annealing treatment is 200℃-350℃; and / or, The first annealing process takes 10-40 minutes.

[0012] Furthermore, the second annealing treatment is performed at a temperature of 260℃-300℃; and / or, The second annealing process takes 10-40 minutes.

[0013] Secondly, embodiments of this application also provide a perovskite thin film, which is prepared by the above-described method for preparing perovskite thin films.

[0014] Thirdly, embodiments of this application also provide a solar cell device, including the perovskite thin film described above.

[0015] The beneficial effects of this application are as follows: In this application, a precursor film containing CsPb2Br5 is formed by alternating deposition of CsBr and PbBr2. After deposition, a first annealing treatment is performed to stabilize the crystal structure and uniformity of the precursor film, facilitating the formation of a more regular lattice for the CsPb2Br5 mesophase or lead-rich mesophase structure. This makes it easier for the bromine-rich source to enter the CsPb2Br5 mesophase or lead-rich mesophase structure during subsequent gas-phase bromine-rich source treatment, achieving in-situ transformation. Heating the precursor film in a bromine-rich atmosphere promotes the transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase under the driving force of the bromine-rich chemical potential, while simultaneously suppressing the formation of bromine vacancies. A second annealing treatment yields a perovskite film with high crystallinity and high phase purity. The bromine-rich atmosphere treatment and annealing treatment work synergistically in stages, achieving decoupled control of the phase transformation kinetics and thermodynamic processes. Furthermore, by controlling the molar ratio of CsBr to PbBr2 within the range of (1-1.2):1, the cesium composition in the system can be finely controlled while ensuring stoichiometric equilibrium of the reaction. This allows for the effective in-situ transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase under a bromine-rich atmosphere. This ratio range not only improves the completeness of the phase transformation but also suppresses the formation of defect states and the precipitation of secondary phases caused by compositional deviations, thereby significantly improving the crystallinity, phase purity, and photoelectric properties of the perovskite film.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0018] Figure 1 Images obtained using a scanning electron microscope according to Embodiment 1 of this application; Figure 2 Images obtained using a scanning electron microscope according to Embodiment 2 of this application; Figure 3 Images obtained using a scanning electron microscope according to Embodiment 3 of this application; Figure 4 Image of a scanning electron microscope of Comparative Example 1 of this application; Figure 5 Image of the scanning electron microscope used in Comparative Example 2 of this application; Figure 6 Image of a scanning electron microscope of Comparative Example 3 of this application; Figure 7 The images are XRD patterns of Examples 1-3 and Comparative Examples 1-3 of this application. Detailed Implementation

[0019] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0021] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0025] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0026] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0027] All-inorganic perovskite CsPbBr3 (approximately 2.3 eV) holds significant promise for applications in high-stability optoelectronic devices due to its excellent thermal and optical stability and suitable bandgap characteristics, particularly for high-stability solar cells and semi-transparent photovoltaic devices. Currently, the preparation of CsPbBr3 thin films mainly includes two methods: solution deposition and physical vapor deposition. While solution deposition offers advantages such as low equipment cost and simple process, it suffers from poor film uniformity and repeatability, and is difficult to scale up for industrial production. In contrast, physical vapor deposition methods, such as co-evaporation and sequential evaporation techniques, can achieve the preparation of perovskite thin films with high uniformity and high density, making them more suitable for industrial production.

[0028] However, in the co-evaporation preparation of CsPbBr3 thin films using CsBr and PbBr2 in related technologies, the significant difference in vapor pressure between the two materials and the complex reaction kinetics easily lead to the formation of non-ideal phase structures, particularly lead-rich intermediate products such as CsPb2Br5. The formation mechanism lies in the fact that, in the early stages of deposition or reaction, the Pb-Br framework is more likely to form first, while Cs ions diffuse more slowly. Therefore, a structure dominated by the Pb-Br layer is formed first. This structure is essentially a Pb-Br layer, and after Cs ions fill it, a layered CsPb2Br5 two-dimensional layered intermediate phase is further formed. Therefore, even when using a stoichiometric ratio of CsBr to PbBr2 as the overall feed ratio, in actual vacuum deposition, due to the differences in the evaporation behavior of each component and the limited Cs ion diffusion kinetics, the system is difficult to achieve a uniform stoichiometric distribution in the early stages of growth, easily leading to the formation of lead-rich structures locally, thus resulting in the formation of the CsPb2Br5 intermediate phase. Limited in carrier transport and light absorption, its photoelectric properties are typically significantly lower than those of three-dimensional CsPbBr3, and it is often considered an undesirable intermediate phase or byproduct affecting device performance. Existing technologies usually suppress or eliminate the formation of the CsPb2Br5 phase by increasing the annealing temperature or adjusting the evaporation ratio, but these methods often fail to completely avoid the formation of this intermediate phase and may lead to poor film crystal quality or compositional deviation.

[0029] To achieve the above objectives, in a first aspect, embodiments of this application provide a method for preparing a perovskite thin film, comprising: providing a substrate; alternately depositing CsBr and PbBr2 on the substrate, and performing a first annealing treatment to obtain a precursor film; heating the precursor film in a bromine-rich atmosphere, and performing a second annealing treatment to obtain a perovskite thin film; wherein the molar ratio of CsBr to PbBr2 is (1-1.2):1.

[0030] In this application, a precursor film containing CsPb2Br5 is formed by alternating deposition of CsBr and PbBr2. After deposition, a first annealing treatment is performed to stabilize the crystal structure and uniformity of the precursor film, facilitating the formation of a more regular lattice for the CsPb2Br5 mesophase or lead-rich mesophase structure. This makes it easier for the bromine-rich source to enter the CsPb2Br5 mesophase or lead-rich mesophase structure during subsequent gas-phase bromine-rich source treatment, achieving in-situ transformation. Heating the precursor film in a bromine-rich atmosphere promotes the transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase under the driving force of the bromine-rich chemical potential, while simultaneously suppressing the formation of bromine vacancies. A second annealing treatment yields a perovskite film with high crystallinity and high phase purity. The bromine-rich atmosphere treatment and annealing treatment work synergistically in stages, achieving decoupled control of the phase transformation kinetics and thermodynamic processes. Furthermore, by controlling the molar ratio of CsBr to PbBr2 within the range of (1-1.2):1, the cesium composition in the system can be finely controlled while ensuring stoichiometric equilibrium of the reaction. This allows for the effective in-situ transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase under a bromine-rich atmosphere. This ratio range not only improves the completeness of the phase transformation but also suppresses the formation of defect states and the precipitation of secondary phases caused by compositional deviations, thereby significantly improving the crystallinity, phase purity, and photoelectric properties of the perovskite film.

[0031] In summary, by constructing precursor films through sequential deposition, regulating the phase transformation kinetics and promoting crystal structure reconstruction in a bromine-rich atmosphere, and optimizing the junction process through secondary high-temperature annealing to ensure complete transformation into the target CsPbBr3 phase, the in-situ transformation process from CsPb2Br5 to CsPbBr3 can be controlled in stages, thereby synergistically optimizing the phase purity and crystal quality of the film. Simultaneously, the bromine-rich atmosphere can compensate for bromine vacancy defects generated during perovskite film growth, reducing defect density and improving crystal order, which is beneficial for enhancing the photoelectric properties and stability of the perovskite film.

[0032] It can be explained that the role of the substrate is to provide a flat and stable supporting surface for carrying the subsequently deposited perovskite precursor material. The choice of substrate needs to consider its lattice matching with the perovskite thin film, compatibility of thermal expansion coefficients, and chemical stability. Specifically, the substrate can be a transparent conductive oxide glass substrate, such as a fluorine-doped tin oxide (FTO) substrate, or a silicon substrate or other glass substrate, depending on the application requirements of the target device.

[0033] It can be noted that the substrate can be heated to optimize the deposition quality and crystallization characteristics of the thin film. The substrate heating temperature can be controlled within the range of 50℃-150℃, which helps to promote the surface migration of deposited atoms and improve the density and adhesion of the thin film.

[0034] It can be explained that the specific operation of alternating deposition of CsBr and PbBr2 can be as follows: In a vacuum evaporation apparatus, CsBr and PbBr2 are placed in independent evaporation sources, and by precisely controlling the evaporation rate and deposition time, CsBr and PbBr2 layers are deposited sequentially on the substrate surface. The deposition order can be either CsBr first followed by PbBr2, or PbBr2 first followed by CsBr; this application does not limit this. The number of alternating deposition cycles can be set according to the target film thickness.

[0035] In some embodiments, the molar ratio of CsBr to PbBr2 is (1-1.1):1.

[0036] In this embodiment, by further controlling the molar ratio of CsBr to PbBr2 to (1-1.1):1, more precise control of the cesium composition can be achieved. Within this ratio range, a slight excess of cesium can provide sufficient Cs ion source for the phase transformation reaction under a bromine-rich atmosphere, ensuring the complete transformation of the CsPb2Br5 mesophase to the CsPbBr3 perovskite phase.

[0037] In some embodiments, the bromine-rich atmosphere includes at least one of CsBr and HBr.

[0038] In this embodiment, through the reaction CsBr + CsPb2Br5 = 2CsPbBr3, under a bromine-rich atmosphere, CsBr participates in the reaction as both a bromine and cesium source. The bromine-rich source enters the CsPb2Br5 mesophase, which begins to undergo structural reconstruction under the drive of the bromine-rich chemical potential and transforms into CsPbBr3, while simultaneously suppressing the formation of bromine vacancy defects. HBr gas is used as a component of the bromine-rich atmosphere; under heating conditions, HBr can decompose to produce H... + and Br - , of which Br - It can effectively replenish bromine during the thin film growth process, while H + The presence of these substances helps to regulate the chemical potential of the reaction system, promotes the dissociation and reconstruction of the CsPb2Br5 intermediate phase, and accelerates the transformation kinetics to the CsPbBr3 phase. Furthermore, it is worth mentioning that these substances can be used alone or in combination.

[0039] In some embodiments, the temperature of the heat treatment is 150°C-200°C.

[0040] In this embodiment, by setting the heat treatment temperature within the range of 150℃-200℃, suitable thermodynamic conditions can be provided for the phase transformation reaction under a bromine-rich atmosphere. This is beneficial for the CsPb2Br5 mesophase to have sufficient structural activity, making it easier for the Pb-Br layers in its layered framework to dissociate and reconstruct.

[0041] In some embodiments, the heat treatment time is 10 min to 40 min.

[0042] In this embodiment, by controlling the heating treatment time within the range of 10 min to 40 min, sufficient time can be provided for the phase transformation reaction under a bromine-rich atmosphere.

[0043] In some embodiments, the vacuum degree of the heat treatment is 10. -6 Pa-10 -5 Pa.

[0044] In this embodiment, the pressure of the inorganic bromide is controlled at 10. -6 Pa-10 -5 Within the Pa range, the efficient transport of bromine source materials in the gas phase and their uniform arrival at the precursor film surface are facilitated. Simultaneously, the low-pressure environment reduces gas phase collisions and interference from impurity gases, suppresses side reactions, and contributes to the kinetics of the phase transformation reaction.

[0045] In some embodiments, the CsBr deposition thickness is 150 nm-300 nm.

[0046] In this embodiment, by controlling the CsBr deposition thickness within the range of 150nm-300nm, the uniformity and density of the precursor film are achieved while ensuring sufficient reaction with subsequent PbBr2.

[0047] In some embodiments, the PbBr2 deposition thickness is 200 nm-450 nm.

[0048] In this embodiment, by controlling the PbBr2 deposition thickness within the range of 200nm-450nm, a reasonable ratio can be achieved with the CsBr deposition thickness, ensuring that the molar ratio of Cs to Pb in the precursor is within the target range of (1-1.2):1. This thickness range guarantees sufficient lead source supply to form a complete Pb-Br framework structure while avoiding the problem of incomplete conversion of the CsPb2Br5 mesophase due to excessive lead.

[0049] In some embodiments, the temperature of the first annealing treatment is 200°C-350°C.

[0050] In this embodiment, by setting the temperature of the first annealing treatment within the range of 200℃-350℃, the initial reaction between CsBr and PbBr2 can be promoted, forming a well-structured precursor film. This temperature range provides sufficient thermal activation energy for atomic diffusion and lattice rearrangement, while avoiding film decomposition or component volatilization caused by excessively high temperatures.

[0051] In some embodiments, the first annealing process takes 10-40 minutes.

[0052] In this embodiment, by controlling the first annealing time within the range of 10 min to 40 min, sufficient time can be provided for the reaction between CsBr and PbBr2, thereby promoting the lattice ordering and structural stabilization of the precursor film.

[0053] In some embodiments, the temperature of the second annealing treatment is 260°C-300°C.

[0054] In this embodiment, by controlling the annealing temperature within the range of 260℃-300℃, the residual CsPb2Br5 phase in the intermediate can be further transformed into the CsPbBr3 perovskite phase at high temperature, while promoting grain growth and grain boundary optimization.

[0055] In some embodiments, the second annealing process takes 10-40 minutes.

[0056] In this embodiment, by controlling the annealing time within the range of 10-40 minutes, it is possible to ensure sufficient phase transformation while avoiding problems such as excessive grain growth caused by excessive annealing time. This time window is sufficient for the residual intermediate phase to complete its transformation and for the grain size to reach a more ideal distribution, thereby optimizing the microstructure and photoelectric properties of the perovskite thin film.

[0057] Secondly, embodiments of this application also provide a perovskite thin film, which is prepared by the above-described method for preparing perovskite thin films.

[0058] In this embodiment, the perovskite film prepared by the above-described method has excellent phase purity and crystal quality, with a high proportion of CsPbBr3 perovskite phase and a significantly reduced content of non-ideal intermediate phases such as CsPb2Br5.

[0059] Thirdly, embodiments of this application also provide a solar cell device, including the perovskite thin film described above.

[0060] It is understood that this solar cell device has all the beneficial effects of the perovskite thin film prepared by the above-described perovskite thin film preparation method, which will not be elaborated here.

[0061] It is understandable that this solar cell device can be an all-inorganic perovskite solar cell, or the top or bottom cell in a perovskite tandem solar cell. When used as an all-inorganic perovskite solar cell, the perovskite thin film serves as the light-absorbing layer, working in conjunction with the electron transport layer, hole transport layer, and electrodes to form a complete device structure, utilizing its high phase purity and low defect density to achieve efficient photoelectric conversion. When applied to a perovskite tandem solar cell, the CsPbBr3 perovskite thin film, due to its wide bandgap and excellent thermal stability, is suitable as the light-absorbing layer of the top cell, forming a complementary spectral response with the narrow bandgap bottom cell, thus improving the overall photoelectric conversion efficiency of the tandem device.

[0062] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] I. Preparation Method Example 1 In a vacuum evaporation system, an FTO glass substrate with a deposited SnO2 electron transport layer is placed inside the evaporation chamber, and at 10... -6 Under vacuum conditions, CsBr and PbBr2 were sequentially evaporated and deposited at a molar ratio of 1.1:1 to obtain precursor films. The deposition thickness of PbBr2 was 340 nm, and the deposition thickness of CsBr was 240 nm. After deposition, the substrate was annealed at 320 °C for 20 min.

[0064] The precursor film was heated in a bromine-rich atmosphere at a temperature of 200℃ for 20 min. The bromine-rich atmosphere was an inorganic bromine source, CsBr.

[0065] The perovskite film of Example 1 was then subjected to a second annealing treatment at 300°C for 20 minutes.

[0066] A nickel oxide hole transport layer was deposited on the surface of a perovskite thin film using electron beam evaporation technology. Then, a conductive carbon electrode was screen printed onto the nickel oxide hole transport layer to obtain the perovskite solar cell device of Example 1.

[0067] Example 2 The difference from Example 1 is that CsBr and PbBr2 are sequentially evaporated and deposited at a molar ratio of 1.0:1 to obtain the precursor. The remaining steps are largely the same as in Example 1, resulting in the perovskite thin film and perovskite solar cell device of Example 2.

[0068] Example 3 The difference from Example 1 is that CsBr and PbBr2 were sequentially evaporated and deposited at a molar ratio of 1.2:1 to obtain the precursor. The remaining steps are largely the same as in Example 1, resulting in the perovskite thin film and perovskite solar cell device of Example 3.

[0069] Comparative Example 1 The difference from Example 1 is that the precursor is directly annealed (i.e., the precursor film is not heated in a bromine-rich atmosphere). The remaining steps are largely the same as in Example 1, resulting in the perovskite film of Comparative Example 1 and the perovskite solar cell device.

[0070] Comparative Example 2 The difference from Example 1 is that CsBr and PbBr2 were sequentially evaporated and deposited at a molar ratio of 0.9:1 to obtain the precursor. The remaining steps were largely the same as in Example 1, resulting in the perovskite thin film of Comparative Example 2 and the perovskite solar cell device.

[0071] Comparative Example 3 The difference from Example 1 is that CsBr and PbBr2 were sequentially evaporated and deposited at a molar ratio of 1.3:1 to obtain the precursor. The remaining steps were largely the same as in Example 1, resulting in the perovskite thin film of Comparative Example 3 and the perovskite solar cell device.

[0072] II. Testing Methods 1. The crystal composition and structure of the thin film were characterized using an X-ray diffraction (XRD, Bruker D8 Advance) instrument. The test range was 2θ = 10°-40°, and the tests were conducted at room temperature.

[0073] 2. The surface morphology and microstructure of the thin film were observed using a field emission scanning electron microscope (FESEM, Zeiss Ultra Plus). The tests were conducted at room temperature and in a vacuum environment, with a magnification of 10,000 times.

[0074] 3. The photoelectric performance of the device was measured using a solar simulator (Oriel 94023A, 300 W) coupled with a source meter (Keithley 2400) to obtain its photocurrent density-voltage curve. JV (curve) During the test, the light intensity was one solar radiation intensity (100mW / cm²). 2The light intensity was calibrated using standard silicon solar cells (Oriel VLSI standards silicon solar cell), and the test was conducted at room temperature.

[0075] III. Analysis of Test Results for Each Embodiment and Comparative Example Table 1. Photovoltaic parameters of CsPbBr3 solar cells in Examples 1-3 and Comparative Examples 1-3 As shown in Table 1, compared to the embodiments, the perovskite films in the comparative devices exhibit significant problems such as voids, uneven grain size, and particle agglomeration due to the lack of bromine-rich atmosphere control or deviation from the optimal ratio described in this paper. These structural defects not only increase carrier recombination centers but also reduce the efficiency of the perovskite films. J SC and V OC This can also lead to poor interfacial contact and hindered charge transport, significantly reducing the device's flyback effect (FF). Therefore, by treating the film with a bromine-rich atmosphere and combining it with a reasonable CsBr to PbBr2 ratio (1-1.2:1), the microstructure and interfacial properties of the thin film can be effectively optimized, thereby achieving a synergistic improvement in the overall device performance.

[0076] Depend on Figure 1-3 It can be seen that the perovskite films prepared in Examples 1-3 all exhibit large grain size and dense and uniform surface morphology. In particular, Example 1 has uniform grain distribution, clear boundaries and no obvious pores or impurity phase precipitation, indicating that it has excellent crystal quality.

[0077] Depend on Figure 4-5 It can be seen that, in Comparative Example 1, due to the lack of bromine-rich atmosphere treatment, the film contained a large number of fine particles and an inhomogeneous structure, indicating that the lead-rich mesophase was not fully transformed. In Comparative Example 2, insufficient CsBr content led to significant precipitation of lead iodide, resulting in poor film morphology; while in Comparative Example 3, due to excessive CsBr, the film exhibited blurred grains and an inhomogeneous structure. The above results indicate that bromine-rich atmosphere treatment plays a crucial role in promoting the transformation of the mesophase to the target perovskite phase. Furthermore, controlling the molar ratio of CsBr to PbBr2 within the range of (1-1.2):1 is beneficial for obtaining high-quality perovskite films with uniform grain size and good density.

[0078] Depend on Figure 7The XRD results show that, in the XRD patterns of samples 1 and 2 of Examples, apart from the characteristic diffraction peak of CsPbBr3, other intermediate phase characteristic diffraction peaks are basically invisible. This indicates that under bromine-rich atmosphere and reasonable stoichiometric conditions, the intermediate phase can be effectively transformed into the target perovskite phase, achieving the effective preparation of pure-phase CsPbBr3 thin films. In Example 3, since the molar ratio of CsBr to PbBr2 has reached 1.2:1, after further bromine-rich atmosphere treatment, the characteristic diffraction peak of Cs4PbBr6 at 12.7° has begun to appear, indicating that at this point, the molar ratio of CsBr to PbBr2, or even a larger molar ratio, is no longer suitable for bromine-rich atmosphere treatment. When the molar ratio of CsBr to PbBr2 reaches 1.3:1 (Comparative Example 3), the sample treated with a bromine-rich atmosphere shows a significant excess of CsBr. The characteristic diffraction peaks of the Cs-enriched mesophase Cs4PbBr6 are significantly enhanced, and a slight peak position shift occurs between the characteristic diffraction peaks of Cs4PbBr6 and CsPbBr3, indicating strain within the crystal. This significantly affects the uniformity and stability of the film. In Comparative Example 1, a distinct characteristic diffraction peak of CsPb2Br5 is still present at 11.7°, indicating that the mesophase is difficult to fully transform without the control of a bromine-rich atmosphere, resulting in low purity of the CsPbBr3 perovskite phase. In the XRD pattern of Comparative Example 2, while the intensity of the CsPbBr3 characteristic diffraction peak decreases, a CsPb2Br5 characteristic diffraction peak is also observed, indicating significant incomplete transformation in the system, accompanied by residual Pb-enriched mesophase. SEM images reveal that when the CsBr content is significantly insufficient, treatment with a bromine-rich atmosphere cannot completely remove the mesophase, and the film morphology cannot be significantly improved. It is worth noting that the position shifts of the diffraction peaks for each component under conditions of CsBr excess or deficiency are mainly attributed to changes in the internal stress state and defect distribution of the film, rather than changes in the crystalline structure type.

[0079] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a perovskite thin film, characterized by, include: Provide a base; CsBr and PbBr2 were alternately deposited on the substrate, and a first annealing treatment was performed to obtain a precursor film. The precursor film was heated in a bromine-rich atmosphere, followed by a second annealing treatment to obtain a perovskite film; wherein... The molar ratio of CsBr to PbBr2 is (1-1.2):

1.

2. The method of claim 1, wherein the perovskite thin film is prepared by a method comprising: The molar ratio of CsBr to PbBr2 is (1-1.1):

1.

3. The method for preparing perovskite thin films according to claim 1, characterized in that, The bromine-rich atmosphere includes at least one of CsBr and HBr.

4. The method for preparing perovskite thin films according to claim 1, characterized in that, The heat treatment temperature is 150℃-200℃; and / or, The heat treatment time is 10 min-40 min; and / or, The vacuum degree of the heating treatment is 10 -6 Pa-10 -5 Pa.

5. The method for preparing perovskite thin films according to claim 1, characterized in that, The CsBr deposition thickness is 150nm-300nm.

6. The method for preparing perovskite thin films according to claim 1, characterized in that, The PbBr2 deposition thickness is 200nm-450nm.

7. The method for preparing perovskite thin films according to claim 1, characterized in that, The temperature of the first annealing treatment is 200℃-350℃; and / or, The first annealing process takes 10-40 minutes.

8. The method for preparing perovskite thin films according to claim 1, characterized in that, The temperature for the second annealing treatment is 260℃-300℃; and / or, The second annealing process takes 10-40 minutes.

9. A perovskite thin film, characterized in that, It is prepared by the method for preparing perovskite thin films according to any one of claims 1-8.

10. A solar cell device, characterized in that, Including the perovskite thin film as described in claim 9.

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