A MAPbI3 perovskite film based on defect competition regulation and a preparation method thereof

Abstract

The application discloses a MAPbI3 perovskite film based on defect competition regulation and a preparation method thereof. The preparation method of the MAPbI3 perovskite film based on defect competition regulation comprises the following steps: S1, methylammonium iodide and lead iodide are added into a solvent to obtain a precursor solution; S2, a substrate is pretreated; S3, the precursor solution is deposited on the substrate by adopting an anti-solvent spin coating method to obtain a precursor film; and S4, the precursor film is subjected to annealing treatment to obtain the MAPbI3 perovskite film based on defect competition regulation. The molar ratio of the methylammonium iodide and the lead iodide is (0.8-1.2):1. By adjusting the stoichiometric ratio of the precursor, the application realizes the synergistic regulation between the grain growth behavior and the defect kinetics, thereby reducing the non-radiation recombination, improving the carrier kinetic behavior and improving the stability of the perovskite film.

Description

Technical Field

[0001] This invention relates to the field of perovskite optoelectronic materials technology, and in particular to a MAPbI3 perovskite thin film based on defect competition regulation and its preparation method. Background Technology

[0002] Organic-inorganic hybrid perovskite materials (represented by MAPbI3) have attracted much attention due to their excellent light absorption, long carrier diffusion length, high defect tolerance, and solution processability. However, the photoelectric properties of MAPbI3 are highly dependent on the crystal quality and defect states of the thin film. In actual preparation, various defect states easily form within the perovskite film due to factors such as precursor evaporation rate mismatch, ion migration behavior, and unstable crystallization kinetics. These defects can induce nonradiative recombination, leading to a shortened carrier lifetime and a reduced diffusion coefficient; simultaneously, defect sites provide channels for ion migration, inducing harmful phase segregation and perovskite phase decomposition; in perovskite solar cells, interface defects can also form potential barriers, hindering effective charge extraction and injection.

[0003] To address the performance degradation caused by the aforementioned defects, existing technologies have developed various defect control strategies, mainly including: interface engineering, additive engineering, solvent engineering, and component engineering. Interface engineering reduces the density of interface trap states by introducing interface modification or passivation layers; additive engineering regulates crystallization kinetics and passivates defects by introducing functional additives into the precursor solution; solvent engineering adjusts the precursor evaporation rate and crystal growth process by optimizing the solvent system or antisolvent dropping process; and component engineering modifies the defect formation energy by adjusting the perovskite ion composition, thus intrinsically suppressing defect formation.

[0004] Existing research generally suggests that large grain size can reduce the number of grain boundaries, thereby lowering the interface defect density and improving device performance. Therefore, traditional techniques typically optimize perovskite performance by promoting thin film grain growth. However, research has revealed that grain size is not the sole determinant of perovskite performance. Current technologies primarily focus on grain size optimization, lacking research on the competition mechanism between interface defects and point vacancy defects. In particular, there is a lack of methods that can combine ultrafast transient absorption spectroscopy to analyze the defect evolution process and further guide defect control and process optimization. Furthermore, existing interface engineering and additive engineering methods often suffer from complex processes, poor repeatability, and high costs, making it difficult to simultaneously achieve synergistic control of grain size optimization and defect state density.

[0005] Therefore, developing a method for preparing MAPbI3 perovskite thin films that can simultaneously control grain size and defect dynamics and achieve a competitive balance between interface defects and point vacancy defects is of great significance for improving the performance and stability of perovskite devices. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a MAPbI3 perovskite thin film based on defect competition regulation and its preparation method. By adjusting the precursor stoichiometry, synergistic regulation between grain growth behavior and defect dynamics is achieved, thereby reducing nonradiative recombination, improving carrier dynamics, and enhancing the stability of the perovskite thin film.

[0007] One object of the present invention is to provide a MAPbI3 perovskite thin film based on defect competition regulation, wherein the structure of the MAPbI3 perovskite thin film based on defect competition regulation includes, from bottom to top: a substrate and a MAPbI3 perovskite thin film layer. The grain size in the MAPbI3 perovskite thin film is 100-500 nm.

[0008] Furthermore, the MAPbI3 perovskite thin film layer is a precursor solution obtained by mixing methylammonium iodide (MAI) and lead iodide (PbI2), which is prepared by antisolvent spin coating and annealing.

[0009] Furthermore, the antisolvent is chlorobenzene (CB).

[0010] Furthermore, the substrate is a glass substrate.

[0011] Furthermore, the method for preparing the MAPbI3 perovskite thin film based on defect competition regulation includes the following steps: S1. Add methylammonium iodide and lead iodide to a solvent to obtain a precursor solution; S2. Pre-treat the substrate; S3. The precursor solution is deposited onto the substrate using an anti-solvent spin coating method to obtain a precursor film. S4. Anneal the precursor film to obtain a MAPbI3 perovskite film based on defect competition regulation.

[0012] Furthermore, the molar ratio of the methylammonium iodide to lead iodide is (0.8-1.2):1.

[0013] Furthermore, the molar ratio of the methylammonium iodide and lead iodide is selected from 0.8:1, 0.9:1, 1:1, 1.1:1, and 1.2:1.

[0014] The inventors discovered that when the stoichiometry deviates further from equilibrium, although the perovskite film grains continue to increase, device performance does not improve further; instead, carrier dynamics deteriorates and stability decreases. Further research shows that while excess precursor components can reduce grain boundary numbers and interface defects, they also induce an increase in point vacancy defects, thereby forming new defect recombination centers and enhancing nonradiative recombination processes. Therefore, perovskite performance is not only affected by interface defects but also constrained by the evolution behavior of point vacancy defects, and these two factors compete with each other.

[0015] Furthermore, the concentration of the precursor solution is 0.6-0.8 mol / L.

[0016] Furthermore, the solvent is selected from one or more of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0017] Furthermore, the annealing temperature is 90-110℃ and the time is 10-30 min.

[0018] Furthermore, the preprocessing includes: The substrate was sequentially immersed in deionized water, ethanol, isopropanol and acetone for ultrasonic cleaning. The ultrasonic cleaning time for each solvent is 15 min. The cleaned substrate is then subjected to ultraviolet ozone treatment to enhance its surface hydrophilicity. The ultraviolet ozone treatment time is 15 minutes.

[0019] Furthermore, the antisolvent spin coating method includes: 40 μL of the precursor solution was dropped onto the substrate surface and spin-coated at 4000 rpm for 30 s. During the high-speed rotation, 150 μL of CB was rapidly added dropwise at 6 s as an antisolvent to induce the supersaturation precipitation of the precursor.

[0020] Another objective of this invention is to provide a method for characterizing the defect dynamics of the aforementioned MAPbI3 perovskite thin film based on defect competition regulation, comprising the following steps: M1. Transient absorption spectroscopy was performed on MAPbI3 perovskite thin films based on defect competition modulation. M2. Extract the kinetic curve of the transient absorption spectrum bleaching peak and analyze the carrier lifetime; M3. Transient absorption wide-field imaging was used to test and analyze the evolution process of dominant defects in perovskite thin films. M4. The evolution process of point vacancy defects in perovskite thin films was analyzed using transient absorption point imaging tests. It also includes: extracting the thin film carrier diffusion constant from test data, including the following steps: L1. Extract the carrier distribution profile along the X-axis from the point image at each delay time, and fit the profile with a Gaussian function to obtain the Gaussian curves of the carrier distribution at different times and their full width at half maximum (FWHM). L2. Based on the Gaussian fitting results, calculate the mean square displacement of the carrier distribution; L3. According to diffusion theory, the mean square displacement of carrier distribution It satisfies the one-dimensional diffusion equation with respect to time t: right The relationship with t is linearly fitted, and the carrier diffusion coefficient D is calculated from the fitting slope. The point vacancy defect states of the thin film are analyzed using the carrier diffusion coefficient D.

[0021] The present invention has the following beneficial effects: This invention achieves synergistic regulation of grain growth behavior and defect kinetics in MAPbI3 perovskite films by adjusting the stoichiometric ratio of MAI to PbI2. As the MAI ratio increases, the perovskite film grain size gradually increases, while the interface defect density decreases, thereby weakening the nonradiative recombination process at the interface. When MAI is further excessive, although the grain size continues to increase, point vacancy defects further increase, thereby enhancing nonradiative recombination and leading to deterioration of carrier kinetics. This invention reveals a competitive relationship between interface defects and point vacancy defects, breaking through the traditional perception that "larger grains equal higher performance."

[0022] This invention also incorporates ultrafast transient absorption spectroscopy to analyze the changes in carrier lifetime and carrier diffusion coefficient of perovskite films under different stoichiometric conditions, enabling the characterization of the evolution of interface defects and point vacancy defects, and establishing a defect competition control mechanism. Compared to traditional interface engineering and additive engineering, this invention eliminates the need for complex additives or multilayer interface modifications, achieving long carrier lifetime and high stability MAPbI3 perovskite films simply through stoichiometric control. The process is simple, highly reproducible, and facilitates large-area fabrication and industrial application. Attached Figure Description

[0023] Figure 1 A schematic flowchart of the steps for preparing MAPbI3 perovskite thin films based on defect competition regulation according to the present invention is shown.

[0024] Figure 2 The scanning electron microscope images, X-ray diffraction test results, photoluminescence spectrum and steady-state visible light absorption spectrum of the thin film prepared in the examples are shown. in, Figure 2 (a) shows the scanning electron microscope images of the thin film; Figure 2 (b) shows the XRD pattern of the thin film; Figure 2 (c) shows the PL pattern of the thin film; Figure 2 (d) shows the visible absorption spectrum of the thin film.

[0025] Figure 3 The pump probe optical path diagram is shown.

[0026] Figure 4 The transient absorption test and analysis results of the thin films prepared in the examples are shown; in, Figure 4 (a) shows the transient absorption spectrum of the MAI:PbI2 thin film prepared in the example with a ratio of 1.1:1; Figure 4 (b) illustrates the evolution of transient absorption signals of the MAI:PbI2 1.1:1 thin film prepared in the examples at different delay times; Figure 4 (c) shows the bleaching peak kinetic fitting results of the films prepared in the examples.

[0027] Figure 5 The transient absorption wide-field imaging test results of the thin film prepared in the examples are shown.

[0028] Figure 6 The transient absorption point imaging test results of the thin film prepared in the example are shown; in, Figure 6 (a) shows dot images of the MAI:PbI2 1.1:1 thin film prepared in the example at different delay times; Figure 6 (b) shows a one-dimensional carrier diffusion distribution evolution diagram of the MAI:PbI2 1.1:1 thin film prepared in the example; Figure 6 (c) shows a linear fit plot of the diffusion variance over time for the MAI:PbI2 1.1:1 thin film prepared in the examples; Figure 6 (d) shows the carrier diffusion coefficient of the thin film prepared in the examples.

[0029] Figure 7 A mechanism diagram of MAPbI3 perovskite thin films based on defect competition regulation is shown. Detailed Implementation

[0030] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0031] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0032] It should be understood that, except in any operational instance or otherwise indicated, all figures representing the amounts of ingredients used, for example, in the specification and claims, should be understood to be modified in all cases by the term "about". Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximations varying with the desired performance to be obtained according to the invention.

[0033] Example 1 A MAPbI3 perovskite thin film based on defect competition regulation, wherein the structure of the MAPbI3 perovskite thin film based on defect competition regulation includes, from bottom to top: a substrate and a MAPbI3 perovskite thin film layer. The method for preparing the MAPbI3 perovskite thin film based on defect competition regulation includes the following steps: S1. Add 1.12 mmol MAI and 1.4 mmol PbI2 to a mixed solvent of 1.8 ml DMF and 0.2 ml DMSO, and stir magnetically at room temperature until completely dissolved and clear to obtain a MAPbI3 precursor solution. S2. The glass substrate was sequentially immersed in deionized water, ethanol, isopropanol and acetone for ultrasonic cleaning. The ultrasonic cleaning time in each solvent was 15 min to remove impurities and organic contaminants from the substrate surface. After cleaning, the substrate surface was dried with high-purity nitrogen. Then, the substrate was placed in an ultraviolet ozone cleaner for 15 min to enhance the hydrophilicity of the substrate surface and improve the spreading ability of the precursor solution on the substrate surface. S3. 40 μL of MAPbI3 precursor solution was dropped onto the pretreated glass substrate surface; then, thin film deposition was performed by spin coating at a speed of 4000 rpm for 30 s; 6 s after the start of spin coating, 150 μL of CB was rapidly dropped onto the high-speed rotating substrate surface as an antisolvent to induce rapid supersaturation precipitation of the precursor and promote the formation of perovskite nuclei, thus obtaining the precursor film; S4. After spin coating, the precursor film is placed on a 100°C heating stage for annealing for 20 min to obtain a MAPbI3 perovskite film based on defect competition regulation.

[0034] Figure 1 A schematic flowchart of the steps for preparing MAPbI3 perovskite thin films based on defect competition regulation according to the present invention is shown.

[0035] Example 2 A MAPbI3 perovskite thin film based on defect competition regulation. The difference between this embodiment and Example 1 is that in step S1, the MAPbI3 perovskite film is modified to 1.26 mmol MAI and 1.4 mmol PbI2, while the other preparation methods are the same as in Example 1.

[0036] Example 3 A MAPbI3 perovskite thin film based on defect competition regulation. The difference between this embodiment and Example 1 is that in step S1, the MAPbI3 perovskite film is modified to 1.4 mmol MAI and 1.4 mmol PbI2, while the other preparation methods are the same as in Example 1.

[0037] Example 4 A MAPbI3 perovskite thin film based on defect competition regulation. The difference between this embodiment and Example 1 is that in step S1, the MAPbI3 perovskite film is modified to 1.54 mmol MAI and 1.4 mmol PbI2, while the other preparation methods are the same as in Example 1.

[0038] Example 5 A MAPbI3 perovskite thin film based on defect competition regulation. The difference between this embodiment and Example 1 is that in step S1, the MAPbI3 perovskite film is modified to 1.68 mmol MAI and 1.4 mmol PbI2, while the other preparation methods are the same as in Example 1.

[0039] Test Example 1 Basic characterization: Basic characterization was performed on the thin films with different stoichiometric ratios prepared in the examples.

[0040] Figure 2 The scanning electron microscope images, X-ray diffraction test results, photoluminescence spectrum and steady-state visible light absorption spectrum of the thin film prepared in the examples are shown. in, Figure 2 (a) shows the scanning electron microscope images of the thin film; Figure 2 (b) shows the XRD pattern of the thin film; Figure 2 (c) shows the PL pattern of the thin film; Figure 2 (d) shows the visible absorption spectrum of the thin film.

[0041] The scanning electron microscope (SEM) images show that as the MAI increases, the grain size of the thin film gradually increases and the number of grain boundaries gradually decreases, indicating that the crystallization quality of the thin film is improved and the interface defect density decreases accordingly.

[0042] XRD results show that all five groups of MAPbI3 films exhibit distinct and sharp diffraction peaks at approximately 14.1°, 28.4°, and 31.8° 2θ, corresponding to the (110), (220), and (310) crystal planes of the tetragonal MAPbI3 perovskite crystal structure, respectively. This result is largely consistent with standard MAPbI3 crystal diffraction data reported in relevant literature. This indicates that in this embodiment of the invention, minor deviations in the precursor stoichiometry did not cause a phase transition or significant lattice distortion in the perovskite crystal structure, and high-purity MAPbI3 polycrystalline films were successfully prepared under different stoichiometric conditions.

[0043] The PL spectral results show that the emission peak positions of all samples remain basically consistent, indicating that the band gap structure of the MAPbI3 film did not change significantly under different stoichiometric conditions. However, there are significant differences in the PL luminescence intensity among the samples. With the increase of MAI content, the PL luminescence intensity gradually increases, indicating that the nonradiative recombination process in the film is suppressed and the radiative recombination efficiency gradually increases, suggesting a decrease in the defect state density.

[0044] The absorption spectra show that all MAPbI3 films exhibit similar absorption edge positions around 780 nm, further indicating that changing the MAI:PbI2 stoichiometric ratio did not significantly alter the intrinsic bandgap structure of MAPbI3. With increasing MAI content, the overall absorption intensity of the films gradually increases, while the absorption edge becomes steeper, indicating improved film crystallinity and reduced structural disorder and defect state density.

[0045] Among the samples, the MAI:PbI2 ratio of 1.1:1 exhibited the strongest absorption intensity and the steepest absorption edge, indicating that the thin film crystal structure was more complete under this stoichiometric ratio, defect-induced band tail states were effectively suppressed, and non-radiative recombination channels were further reduced, thereby improving the optical quality and carrier dynamics of the thin film. However, when the MAI content was further increased to 1.2:1, the absorption performance did not continue to improve, but instead showed a certain degree of decline. This indicates that although excessive MAI can further promote grain growth and reduce some grain boundary defects, it also introduces local structural disorder, thereby inducing the formation of new point vacancy defects, ultimately leading to the deterioration of the thin film's optical performance. The above results show that grain size is not the only factor determining the performance of MAPbI3 thin films; there is a competitive relationship between interface defects and point vacancy defects, which jointly affect the photoelectric properties of perovskite thin films.

[0046] Test Example 2 Transient absorption spectroscopy test: The thin films prepared in the examples were subjected to transient absorption spectroscopy test and the carrier lifetime was analyzed.

[0047] Test Method: The transient absorption spectrum of the thin film was measured using a pump-probe optical path. In this path, a strong beam of light was used as the pump light to excite the sample, while a separate beam of visible white light was used as the probe light to test the sample's absorption. By controlling the delay time between the pump and probe light using a displacement platform, the change in the sample's absorption of the probe beam (transient absorption signal ∆A) during each pump-probe delay could be recorded, both with and without pump excitation, thus visualizing carrier dynamics. This test example used a 515 nm femtosecond pulse as the pump light, and the detection range covered the visible wavelength range of 520 nm to 950 nm.

[0048] Figure 3 The pump probe optical path diagram is shown.

[0049] Figure 4 The transient absorption test and analysis results of the thin films prepared in the examples are shown; in, Figure 4 (a) shows the transient absorption spectrum of the MAI:PbI2 thin film prepared in the example with a ratio of 1.1:1; Figure 4 (b) illustrates the evolution of transient absorption signals of the MAI:PbI2 1.1:1 thin film prepared in the examples at different delay times; Figure 4 (c) shows the bleaching peak kinetic fitting results of the films prepared in the examples.

[0050] Transient absorption spectroscopy, with its femtosecond to microsecond temporal resolution, can track the generation and decay of excited states, reflecting the complete dynamic behavior of carriers being trapped, escaping, and recombinating due to defects. Therefore, it is an effective measurement method for studying defect states in semiconductor materials. Figure 4 As shown in (a), the thin film exhibits a significant negative signal near 755 nm, corresponding to ground-state bleaching (GSB). This signal originates from the bandgap absorption saturation effect caused by photogenerated carriers filling the band edge states, and its peak position coincides with the exciton peak position in the steady-state absorption spectrum. The decay rate of the bleaching signal is closely related to the defect state density in the material. By analyzing the change of this signal with delay time, the influence of defects on carrier dynamics can be evaluated. Figure 4 (c) It can be seen that as the MAI ratio increases, the carrier lifetime of the film gradually increases, reaching a maximum value when the MAI:PbI2 ratio is 1.1:1. When MAI is further in excess, although the grain size continues to increase, the carrier lifetime decreases instead, indicating that new defect recombination channels appear inside the film at this time.

[0051] Test Example 3 Transient absorption wide-field imaging test: Transient absorption wide-field imaging test was performed on the thin film prepared in the example and the evolution of dominant defects was analyzed.

[0052] Test method: The pump light and probe light in the pump-probe optical path are introduced into an optical microscope, which can reduce the light spot to the micrometer level. The absorption change of the sample in the excited state to the probe light is imaged by a wide-field microscopic imaging module and recorded by a high-sensitivity area array detector to obtain a series of transient absorption wide-field images at different delay times.

[0053] Figure 5 The transient absorption wide-field imaging test results of the thin film prepared in the examples are shown.

[0054] Transient absorption microscopy combines the ultra-high time resolution of transient absorption spectroscopy with the spatial resolution of optical microscopy, enabling spatially resolved characterization of ultrafast carrier dynamics within materials. Through spatial mapping, it directly reveals the dynamic differences between grains, grain boundaries, and local defect regions, effectively avoiding the masking of local dynamic characteristics by the ensemble averaging effect in polycrystalline systems. Furthermore, it reveals key physical processes such as thin film morphology, carrier diffusion, and transgrain transport.

[0055] Transient absorption wide-field imaging (TAM) results show that the spatial carrier dynamics homogeneity of the MAPbI3 film significantly evolves with increasing MAI content in the precursor. For the 0.8:1 sample with insufficient MAI, numerous local regions with alternating high and low signal distributions are observed in the TAM image, exhibiting significant spatial heterogeneity. This is mainly attributed to the rapid longitudinal crystallization of PbI2 under MAI-deficient conditions, leading to the formation of numerous grain boundary defects within the film, thus causing significantly differentiated recombination dynamics of carriers in different regions. As the MAI ratio increases to 0.9:1 and 1:1, the TAM signal gradually becomes more uniform, indicating that an appropriate amount of MAI can disrupt [PbI6]. 4- The layered structure inhibits the rapid longitudinal crystallization of PbI2 and slows down the crystallization process, thereby promoting the formation of large grain films, reducing the density of grain boundary trap states, and ultimately effectively suppressing the defect-assisted recombination process and improving the uniformity of carrier transport.

[0056] Among them, the 1.1:1 sample exhibited the most uniform transient absorption response, with significantly reduced spatial signal fluctuations, indicating that this sample possesses the lowest energy disorder and the best defect passivation effect, achieving optimal carrier dynamics uniformity. Further increasing the MAI to 1.2:1 revealed a reappearance of a distinct striped non-uniform structure in the TAM image, suggesting that excessive MAI induces new microscopic heterogeneity. Since excessive MAI further promotes grain size increase, the heterogeneity in the film at this point differs from the random local trap distribution dominated by grain boundary defects under insufficient MAI conditions, and is more likely derived from the increase in point vacancy defects caused by local composition fluctuations. Overall, the wide-field TAM results reveal that with increasing MAI content, the MAPbI3 film undergoes an evolution from "grain boundary defect-dominated heterogeneity" to "uniform defect passivation" and then to "point vacancy defect-dominated heterogeneity," providing important evidence for understanding the influence of precursor stoichiometry on perovskite local carrier dynamics and defect regulation mechanisms.

[0057] Test Example 4 Transient absorption point imaging test: The thin film prepared in the example was subjected to transient absorption point imaging test and the evolution process of point defects was analyzed.

[0058] Test method: Transient absorption point images with different delay times were obtained by using point excitation and wide-field detection modes of transient absorption microscopy.

[0059] Figure 6 The transient absorption point imaging test results of the thin film prepared in the example are shown; in, Figure 6 (a) shows dot images of the MAI:PbI2 1.1:1 thin film prepared in the example at different delay times; Figure 6 (b) shows a one-dimensional carrier diffusion distribution evolution diagram of the MAI:PbI2 1.1:1 thin film prepared in the example; Figure 6 (c) shows a linear fit plot of the diffusion variance over time for the MAI:PbI2 1.1:1 thin film prepared in the examples; Figure 6 (d) shows the carrier diffusion coefficient of the thin film prepared in the examples.

[0060] Depend on Figure 6 As can be seen, the carrier diffusion coefficient D can be quantitatively obtained by analyzing the point transient absorption microscopy results of MAPbI3 films with different stoichiometric ratios. Overall, the diffusion coefficient gradually increases with the increase of MAI content in the precursor, indicating that the lateral transport capacity of carriers inside the film is significantly improved.

[0061] Combined with wide-field TAM results, it is evident that under insufficient MAI conditions, the heterogeneity within the film is dominated by grain boundary defects. These defects, acting as important nonradiative recombination centers, significantly inhibit carrier diffusion. On one hand, defect states trap free carriers and induce nonradiative recombination, thus reducing the effective diffuse carrier concentration. On the other hand, grain boundary regions are typically accompanied by local energy barriers and potential fluctuations. Carriers must overcome additional scattering and barrier limitations when crossing grain boundaries, leading to a decrease in the diffusion coefficient. When the MAI:PbI₂ ratio increases to 1.1:1 and 1.2:1, point defects dominate the heterogeneity within the film. Compared to deep grain boundary traps, point vacancy defects exhibit more shallow trap states, with a relatively weaker direct nonradiative recombination effect on carriers, but they still influence carrier transport processes as local scattering centers. In the 1.2:1 sample, although grain boundary defects are further reduced, excessive MAI may induce an increase in point vacancy defects, thereby enhancing local energy disorder and carrier scattering effects. Therefore, the sample did not continue to exhibit better spatial transport properties, but instead showed a certain degree of spatial dynamic heterogeneity again.

[0062] Figure 7 A mechanism diagram of MAPbI3 perovskite thin films based on defect competition regulation is shown.

[0063] Overall, both point TAM and wide-field TAM results indicate that carrier diffusion behavior in MAPbI3 films is jointly regulated by the co-evolution of grain boundary defects and point vacancy defects. With increasing MAI content, the dominant factor restricting carrier transport gradually shifts from deep grain boundary traps to shallow point vacancy traps.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A MAPbI3 perovskite thin film based on defect competition regulation, characterized in that, The structure of the MAPbI3 perovskite thin film based on defect competition regulation includes, from bottom to top: a substrate and a MAPbI3 perovskite thin film layer. The grain size in the MAPbI3 perovskite thin film is 100-500 nm.

2. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 1, characterized in that, The MAPbI3 perovskite thin film layer is a precursor solution obtained by mixing methylammonium iodide and lead iodide, and is prepared by antisolvent spin coating and annealing.

3. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 2, characterized in that, The antisolvent is chlorobenzene.

4. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 1, characterized in that, The substrate is a glass substrate.

5. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 1, characterized in that, The method for preparing the MAPbI3 perovskite thin film based on defect competition regulation includes the following steps: S1. Add methylammonium iodide and lead iodide to a solvent to obtain a precursor solution; S2. Pre-treat the substrate; S3. The precursor solution is deposited onto the substrate using an anti-solvent spin coating method to obtain a precursor film. S4. Anneal the precursor film to obtain a MAPbI3 perovskite film based on defect competition regulation.

6. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 5, characterized in that, The molar ratio of ammonium methyl iodide to lead iodide is (0.8-1.2):

1.

7. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 5, characterized in that, The concentration of the precursor solution is 0.6-0.8 mol / L.

8. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 5, characterized in that, The solvent is selected from one or more of dimethyl sulfoxide and N,N-dimethylformamide.

9. The MAPbI3 perovskite thin film based on defect competition regulation according to claim 5, characterized in that, The annealing temperature is 90-110℃ and the time is 10-30 min.

10. A method for characterizing the defect dynamics of MAPbI3 perovskite thin films based on defect competition regulation as described in any one of claims 1-9, characterized in that, Includes the following steps: M1. Transient absorption spectroscopy was performed on MAPbI3 perovskite thin films based on defect competition modulation. M2. Extract the kinetic curve of the transient absorption spectrum bleaching peak and analyze the carrier lifetime; M3. Transient absorption wide-field imaging was used to test and analyze the evolution process of dominant defects in perovskite thin films. M4. The evolution process of point vacancy defects in perovskite thin films was analyzed using transient absorption point imaging tests. It also includes: extracting the thin film carrier diffusion constant from test data, including the following steps: L1. Extract the carrier distribution profile along the X-axis from the point image at each delay time, and fit the profile with a Gaussian function to obtain the Gaussian curves of the carrier distribution at different times and their full width at half maximum (FWHM). L2. Based on the Gaussian fitting results, calculate the mean square displacement of the carrier distribution; L3. According to diffusion theory, the mean square displacement of carrier distribution It satisfies the one-dimensional diffusion equation with respect to time t: right The relationship with t is linearly fitted, and the carrier diffusion coefficient D is calculated from the fitting slope. The point vacancy defect states of the thin film are analyzed using the carrier diffusion coefficient D.

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