A method for preparing a (111) preferentially oriented perovskite film based on substrate regulation

Abstract

This invention discloses a method for preparing a (111) preferred-oriented perovskite thin film based on substrate control, comprising: providing a substrate; forming a SnO2 electron transport layer on the substrate; forming a zinc oxalate (ZnOX) interlayer on the electron transport layer; and preparing the perovskite active layer on the ZnOX interlayer using a two-step sequential deposition method, wherein the perovskite active layer has a (111) preferred orientation; in this invention, the interaction between oxalate anions and PbI2 induces the formation of a porous PbI2 film, which, combined with Zn... 2+ The defect compensation and lattice regulation effects of the embedded perovskite lattice successfully induced the growth of a (111) preferred orientation perovskite thin film with large grains (up to 3 μm in size) and low defect density, and the (111) / (100) peak intensity ratio was improved by nearly 5 times. This invention achieves the simultaneous optimization of perovskite thin film structure and device performance with a simple and effective interface modification strategy, providing a new path that is both scientific and practical for the industrialization of high-performance long-life perovskite solar cells.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a method for preparing a (111) preferred orientation perovskite thin film based on substrate regulation. Background Technology

[0002] With the increasing severity of energy issues, developing efficient, stable, and cost-effective photovoltaic technologies has become a core task in the sustainable energy transition. Perovskite solar cells (PSCs), with their low-cost fabrication processes, high defect tolerance, and excellent power conversion efficiency (PCE), have rapidly become a core research direction for next-generation photovoltaic technologies. Currently, thanks to continuous innovation in materials chemistry and device structure, the certified PCE of single-junction perovskite solar cells has exceeded 27%, demonstrating enormous application potential.

[0003] Perovskite thin films are essentially polycrystalline systems, exhibiting various crystal orientations such as (100), (110), (111), and (210). The differences in atomic arrangement of the crystal planes endow them with significant crystal plane-dependent electronic and physical properties—including carrier mobility, defect state density, surface energy, and environmental stability—which directly affect the photovoltaic performance and long-term operational reliability of the devices. Early research focused on the (100) crystal plane, achieving its preferred orientation through additive engineering and interface modification strategies, and utilizing its high carrier mobility to improve the device's PCE. However, a study published in Science by Ma et al. in 2023 revealed the core advantage of the (111) crystal plane: its resistance to moisture-induced degradation is nearly four times higher than that of the (100) crystal plane. The core mechanism lies in the fact that the adsorption force of water molecules on the (100) crystal plane (93 mN / m) is significantly higher than that on the (111) crystal plane (85 mN / m), which leads to the (100) crystal plane being prone to water molecule-induced Pb-I bond length elongation (from 3.13 Å to 3.15 Å), ultimately triggering an irreversible phase transition from the α phase to the δ phase; while the close-packed atomic structure of the (111) crystal plane can suppress water molecule penetration and ion migration, providing structural protection for the long-term stability of the device. This discovery clarifies the core potential of (111) crystal plane-dominated perovskite films in overcoming the "stability bottleneck" of PSCs.

[0004] However, the inherently rapid crystallization kinetics of perovskites make the controllable growth of the (111) crystal plane a key challenge in the field. In the one-step preparation process, amide additives (such as formamide) and alcohol antisolvents (such as isopropanol) can achieve partial (111) crystal plane orientation by controlling the crystallization rate, but additional defects are easily introduced due to additive residues. In the two-step sequential deposition method adapted to large-scale production, the control of the preferred growth of the (111) crystal plane is more difficult and the process is more complex. The two-step method prepares perovskite films through a stepwise reaction of "inorganic framework preforming - organic salt wetting crystallization". Although this process has the potential for large-scale application, the matching of the penetration depth of organic salt, reaction time and crystallization rate directly affects the crystal plane orientation. Too fast penetration can easily lead to incomplete reaction, and the residual PbI2 will become a defect recombination center; too slow penetration will cause the crystallization kinetics to be unbalanced, and the thermodynamically stable (100) crystal plane will still dominate. Therefore, there are few studies on the preparation of highly oriented (111) preferred oriented films through the two-step method.

[0005] To address the aforementioned technical challenges, this invention proposes introducing a zinc oxalate (ZnOX) functional intermediate layer between the SnO2 electron transport layer and the perovskite active layer. Through its multifunctional synergistic effect, precise control of perovskite crystallization can be achieved. This not only induces preferential growth of the (111) crystal plane but also passivates interface defects and inhibits ion migration, significantly improving the photoelectric conversion efficiency and long-term stability of the device. Summary of the Invention

[0006] This invention aims to solve the problem of controllable growth of (111) preferred-oriented perovskite thin films by leveraging the multifunctional synergistic effect of zinc oxalate (ZnOX) molecules. Specific objectives include: (1) By utilizing the strong electron-withdrawing properties of oxalate anions in ZnOX, oxygen vacancies on the surface of SnO2 electron transport layer are passivated, thus constructing a high-quality interface with low recombination and high charge extraction efficiency. (2) By taking advantage of the strong interaction between oxalate anions and PbI2, a porous PbI2 film is induced to form, thereby optimizing the perovskite crystallization kinetics and providing an excellent template for high-quality film growth. (3) Through Zn in ZnOX 2+ By embedding into the perovskite lattice, lead vacancies (VPb) are compensated and synergistic induction of preferential nucleation of the (111) crystal plane is achieved, ultimately resulting in a (111) oriented perovskite thin film with large grains and low defect density. (4) Combining the moisture resistance of the (111) crystal plane with the "lead-fixing" effect of ZnOX, the long-term stability of the device under humidity and light conditions is significantly improved.

[0007] Specifically, the solution provided by this invention is as follows: A method for preparing a substrate-controlled (111) preferred-oriented perovskite thin film includes the following steps: S1. Provide a substrate; S2. Forming a SnO2 electron transport layer on the substrate: In an air atmosphere, 70 μL of SnO2 electron transport layer dispersion is dropped onto the ITO substrate, spin-coated at 3000 rpm for 50 s, and then annealed on a hot plate at 150 °C for 25 min. S3. Forming a zinc oxalate (ZnOX) interlayer on the electron transport layer: Under a nitrogen atmosphere, 70 μL of ZnOX interlayer solution is dropped onto the surface of the SnO2 film, spin-coated at 3000 rpm for 30 s, and annealed at 100 °C for 10 min. S4. The perovskite active layer is prepared on the zinc oxalate (ZnOX) intermediate layer by a two-step sequential deposition method: first, a PbI2 layer is deposited on the ZnOX intermediate layer, and then the PbI2 layer is reacted with an organic salt solution to form a perovskite film; wherein the perovskite active layer has a (111) crystal plane preferred orientation.

[0008] Preferably, the preparation steps of the SnO2 electron transport layer dispersion include: taking a SnO2 colloidal solution with a mass fraction of 15%, adding deionized water at a volume ratio of 1:3, stirring at room temperature for 30 minutes, and filtering through a 0.22 μm filter membrane for later use.

[0009] Preferably, the method for preparing the ZnOX intermediate layer solution includes: weighing a certain amount of ZnOX powder, adding it to an HBr / DMF mixed solvent, adding a stir bar, stirring at 1000 rpm for 0.5 h at room temperature until completely dissolved, filtering through a 0.22 μm filter membrane to obtain a uniform ZnOX intermediate layer solution for subsequent spin coating; wherein the volume ratio of HBr / DMF is 50:950.

[0010] Preferably, in step S4, the preparation step of the perovskite active layer specifically includes: under a nitrogen atmosphere, adding 70 μL of PbI2 precursor solution, spin-coating at 2000 rpm for 30 s, and annealing at 70°C for 1 min; after cooling, adding 70 μL of organic salt solution, spin-coating at 1800 rpm for 30 s, transferring to an air atmosphere with a humidity of 30%–40%, and annealing at 150°C for 30 min.

[0011] Preferably, the preparation steps of the PbI2 precursor solution include: dissolving 599.3 mg of PbI2 powder in a mixed solvent of 950 μL DMF and 50 μL DMSO, stirring at 70°C for 6 h until completely dissolved, and filtering through a 0.22 μm filter membrane for later use. The preparation steps of the organic salt solution include: dissolving 90 mg of FAI, 6.4 mg of MAI and 9 mg of MACl in 1 mL of isopropanol, stirring at room temperature for 30 min until completely dissolved, and filtering through a 0.22 μm filter membrane for later use.

[0012] The present invention also discloses a perovskite solar cell, comprising the following sequentially stacked components: Substrate; The electron transport layer, zinc oxalate ZnOX intermediate layer and perovskite active layer prepared by the above method, wherein the perovskite active layer has a (111) crystal plane preferred orientation. Hole transport layer formed on the perovskite active layer; And electrodes formed on the hole transport layer.

[0013] Preferably, the preparation steps of the hole transport layer include: adding 50 μL of hole transport layer solution under a nitrogen atmosphere, spin-coating at 3000 rpm for 30 s, and transferring to an air drying cabinet with a humidity of 10%–20% and letting it stand overnight.

[0014] Preferably, the preparation steps of the hole transport layer solution include: dissolving 72.3 mg of Spiro-OMeTAD, 17.5 μL of Li-TFSI solution and 29 μL of 4-tBP in 1 mL of chlorobenzene, filtering through a 0.22 μm filter membrane, and then using it for later use. The Li-TFSI solution is 520 mg of Li-TFSI dissolved in 1 mL of acetonitrile.

[0015] Preferably, the preparation steps of the gold electrode include: in a 5×10 -4 Under a vacuum of Pa, an 80 nm Au thin film was thermally deposited as the back electrode to complete the device fabrication.

[0016] Preferably, the average grain size of the perovskite active layer is greater than or equal to 3 μm.

[0017] In this scheme, ZnOX is a carefully selected multifunctional intermediate layer material whose unique molecular structure endows it with multiple synergistic functions: 1. Oxalate anion (C2O4) 2- It has strong electronegativity and electron-withdrawing properties, and on the one hand, it can react with Sn on the SnO2 surface. 4+ Dangling bonds form strong coordination effects, effectively passivating oxygen vacancies and inhibiting interfacial charge recombination; on the other hand, they can interact strongly with PbI2, increasing the nucleation energy of PbI2, inducing the formation of porous PbI2 films, and optimizing the permeation efficiency of organic salt solutions and the uniform nucleation environment of perovskites.

[0018] 2. Zinc ions (Zn) 2+ ): The ionic radius is small and it is a divalent cation, which can be embedded in the perovskite lattice. It can not only compensate for the lead vacancies (VPb) in the perovskite bulk phase and reduce the defect density, but also regulate the crystallization thermodynamics through lattice distortion, and synergistically promote the preferential nucleation and growth of the (111) crystal plane.

[0019] In summary, the advantages of this invention compared to the prior art are as follows: This invention proposes a method for preparing (111) preferred-oriented perovskite thin films based on zinc oxalate (ZnOX) functional intermediate layer modified substrates. By introducing ZnOX between the SnO2 electron transport layer and the perovskite active layer, multiple functional synergistic optimizations are achieved. 1. Interface optimization: Oxalate anions in ZnOX react with Sn on the SnO2 surface. 4+ It forms a strong coordination effect, efficiently passivates oxygen vacancies, and constructs an interface with low recombination and high charge extraction efficiency; 2. Crystallization regulation: The interaction between oxalate anions and PbI₂ induces the formation of porous PbI₂ membranes, which, combined with Zn... 2+ The defect compensation and lattice regulation effects embedded in the perovskite lattice successfully induced the growth of (111) preferred orientation perovskite thin films with large grains (size up to 3μm) and low defect density, and the (111) / (100) peak intensity ratio was improved by nearly 5 times. 3. Dual performance improvement: The photoelectric conversion efficiency of the device increased from 23.22% to 25.69%, while the humidity stability (T80>1248h) and light stability (maintaining more than 90% of the initial efficiency for 720h) were significantly better than the control group devices.

[0020] 4. Process compatibility and scalability potential: The preparation process of this invention is simple and reproducible, requiring no complex equipment or harsh reaction conditions. It is directly compatible with existing two-step spin coating, spray coating and other large-scale production processes, without the need for major modifications to the production line, thus lowering the threshold for industrial application.

[0021] 5. Application scenario extension: Based on the high stability of the (111) crystal plane and the defect passivation advantage of ZnOX, this technical solution can be extended to new device structures such as perovskite tandem cells and flexible perovskite cells, providing technical support for the application of photovoltaic devices in extreme environments (high humidity, strong light).

[0022] 6. Performance optimization potential: By controlling the interaction strength between ZnOX and perovskite precursors (such as adjusting ZnOX concentration and optimizing solvent system), or by using it in synergy with other functional additives (such as passivators and crystallization regulators), it is expected to further improve the orientation of perovskite films and the long-term stability of devices, and promote the development of PSCs towards higher efficiency and longer lifespan.

[0023] This invention achieves simultaneous optimization of perovskite thin film structure and device performance through a simple and effective interface modification strategy, providing a new path that is both scientific and practical for the industrialization of high-performance, long-life perovskite solar cells. Attached Figure Description

[0024] Figure 1 These are the XPS spectra of the SnO2 electron transport layer in the control and experimental groups of this invention; Where: a is the C 1s spectrum; b is the Zn 2p spectrum; c is the Sn 3d spectrum; d is the O 1s spectrum; Figure 2 These are the morphology, crystallization kinetics, and crystal structure characterization diagrams of the control group and experimental group films in this invention; Wherein: a and b are SEM morphology images of PbI2 films in the control group and experimental group; c and d are SEM morphology images of perovskite films in the control group and experimental group; e and f are in-situ PL spectra of perovskite annealing process in the control group and experimental group; g is XRD comparison image of perovskite films in the control group and experimental group; h is comparison image of (111) / (100) peak intensity ratio of perovskite films in the control group and experimental group; i and j are TEM images of perovskite grains in the control group and experimental group; k and l are EDXS elemental analysis images of perovskite grains in the control group and experimental group. Figure 3 This is a schematic diagram of the light stability of the control group and the experimental group in this invention; Where: a represents the storage stability of the control group and experimental group devices under air atmosphere (30-50% relative humidity); b and c represent the contact angle test of the perovskite thin film of the control group and experimental group; d represents the operational stability of the control group and experimental group devices under continuous illumination under nitrogen atmosphere.

[0025] Figure 4 This is a schematic diagram of the device structure and the molecular formula of ZnOX of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Example

[0027] (a) Experimental group (including ZnOX functional intermediate layer) A method for fabricating a perovskite solar cell includes the following steps: S1. Provide a substrate; S2. Forming a SnO2 electron transport layer on the substrate: In an air atmosphere, 70 μL of SnO2 electron transport layer dispersion is dropped onto the ITO substrate, spin-coated at 3000 rpm for 50 s, and then annealed on a hot plate at 150 °C for 25 min. The preparation steps of the SnO2 electron transport layer dispersion include: taking a SnO2 colloidal solution with a mass fraction of 15%, adding deionized water at a volume ratio of 1:3, stirring at room temperature for 30 min, and filtering through a 0.22 μm filter membrane for later use. S3. Forming a zinc oxalate (ZnOX) interlayer on the electron transport layer: Under a nitrogen atmosphere, 70 μL of ZnOX interlayer solution is dropped onto the surface of the SnO2 film, spin-coated at 3000 rpm for 30 s, and annealed at 100 °C for 10 min. The method for preparing the ZnOX intermediate layer solution includes: weighing a certain amount of ZnOX powder, adding it to an HBr / DMF mixed solvent, adding a stir bar, stirring at 1000 rpm for 0.5 h at room temperature until completely dissolved, filtering through a 0.22 μm filter membrane to obtain a uniform ZnOX intermediate layer solution for subsequent spin coating; wherein the volume ratio of HBr / DMF is 50:950. S4. The perovskite active layer is prepared on the zinc oxalate (ZnOX) intermediate layer by a two-step sequential deposition method: first, a PbI2 layer is deposited on the ZnOX intermediate layer, and then the PbI2 layer is reacted with an organic salt solution to form a perovskite film; wherein the perovskite active layer has a (111) crystal plane preferred orientation.

[0028] Specifically, the preparation steps of the perovskite active layer include: under a nitrogen atmosphere, adding 70 μL of PbI2 precursor solution, spin-coating at 2000 rpm for 30 s, and annealing at 70 °C for 1 min; after cooling, adding 70 μL of organic salt solution, spin-coating at 1800 rpm for 30 s, transferring to an air atmosphere with a humidity of 30%–40%, and annealing at 150 °C for 30 min; The preparation steps of the PbI2 precursor solution include: dissolving 599.3 mg of PbI2 powder in a mixed solvent of 950 μL DMF and 50 μL DMSO, stirring at 70°C for 6 h until completely dissolved, and filtering through a 0.22 μm filter membrane for later use. The preparation steps of the organic salt solution include: dissolving 90 mg of FAI, 6.4 mg of MAI and 9 mg of MACl in 1 mL of isopropanol, stirring at room temperature for 30 min until completely dissolved, and filtering through a 0.22 μm filter membrane for later use. S5. Prepare a hole transport layer on the perovskite active layer: Under a nitrogen atmosphere, add 50 μL of hole transport layer solution, spin coat at 3000 rpm for 30 s, and transfer to an air drying cabinet with a humidity of 10%–20% and let stand overnight. The preparation steps of the hole transport layer solution include: dissolving 72.3 mg of Spiro-OMeTAD, 17.5 μL of Li-TFSI solution and 29 μL of 4-tBP in 1 mL of chlorobenzene, filtering through a 0.22 μm filter membrane, and then using it for later use. The Li-TFSI solution is 520 mg of Li-TFSI dissolved in 1 mL of acetonitrile. S6. Fabricate a gold electrode on the hole transport layer: in a 5×10 -4 Under a vacuum of Pa, an 80 nm Au thin film was thermally deposited as the back electrode to complete the device fabrication.

[0029] (II) Control group (intermediate layer without ZnOX function) The preparation of the ZnOX functional intermediate layer in the above experimental group steps is omitted, and the remaining preparation steps and process parameters are completely consistent with those of the experimental group.

[0030] (III) Performance Testing 1. Interface quality improvement and efficiency enhancement: Efficient passivation of oxygen vacancies on the SnO2 surface to construct a low-complexity, high-quality interface. X-ray photoelectron spectroscopy (XPS) was used to characterize and analyze the electron transport layer of the control group (blank SnO2) and the experimental group (ZnOX-modified SnO2, ZnOX concentration of 1 mg / mL). Figure 1 As shown in a and b, the XPS spectra of the SnO2 films in the experimental group show obvious C=O characteristic peaks and Zn element characteristic peaks, directly confirming that ZnOX has been successfully modified onto the SnO2 surface. Figure 1 As shown in Figure c, compared with the control group, the Sn3d characteristic peak of the experimental group shifted towards the direction of higher binding energy, indicating a strong interaction between ZnOX and SnO2. Furthermore, peak fitting was performed on the O1s core level spectrum (…). Figure 1d): The O1s spectrum of the control group can be decomposed into two characteristic peaks. The peak at 531.98 eV corresponds to the adsorbed hydroxyl group and oxygen vacancy (OOH+OV), and the peak at 530.78 eV belongs to the SnO2 lattice oxygen (Sn-O-Sn). The O1s spectrum of the experimental group can be decomposed into three characteristic peaks. In addition to the OOH+OV peak (shifted to 532.08 eV) and the Sn-O-Sn peak (shifted to 530.98 eV), a new characteristic peak is added at 533.0 eV, corresponding to the oxalate anion (C2O42-) in ZnOX. The peak area quantitative analysis results (Table 1) show that the relative content of OOH+OV on the SnO2 surface in the control group is 32.3%, while the relative content of this component in the experimental group is significantly reduced to 23.8%. Since the deposition and storage conditions of the two groups of films were exactly the same, the content of adsorbed hydroxyl groups (OOH) on the surface was similar. Therefore, the decrease in the OOH+OV content in the experimental group was mainly due to the effective passivation of oxygen vacancies (OV). The above characterization results fully confirm that ZnOX modification can significantly reduce the oxygen vacancy concentration on the SnO2 surface, inhibit charge recombination at the electron transport layer / perovskite layer interface, and thus construct a high-quality interface with low recombination and high charge extraction efficiency.

[0031] Table 1. Peak areas of different O components in the electron transport layer of the control group and the experimental group.

[0032]

[0033] 2. Precise control of crystallization: Inducing the formation of large-grained (111) preferred-orientation perovskite thin films The effects of ZnOX modification on the PbI2 precursor film, perovskite crystallization kinetics, and crystal orientation were systematically analyzed using various characterization methods. The results are as follows: The PbI2 precursor film was characterized using scanning electron microscopy (SEM). Figure 2 a, b) and the morphology of the perovskite film ( Figure 2 (c, d): The control group PbI2 film had a dense structure, while the experimental group PbI2 film exhibited a porous structure, providing an excellent microstructural basis for the infiltration of organic salt solution and uniform nucleation of perovskite. In the final perovskite films, the control group had a grain size of approximately 1 μm and significant PbI2 residue; the experimental group had a significantly increased grain size of approximately 3 μm, an improvement of 3 times, directly confirming that ZnOX modification can effectively improve the crystallinity of perovskite.

[0034] Tracking the crystallization and growth process of perovskite thin films using in-situ photoluminescence (insituPL) Figure 2e, f): The control group film showed a significant PL signal after 15s of annealing, indicating a faster crystallization rate; while the experimental group film only showed a significant PL signal after 25s of annealing, indicating that ZnOX modification can effectively delay the crystallization rate of perovskite, providing sufficient time for crystal growth, and thus promoting the formation of large grain films.

[0035] X-ray diffraction (XRD) test results ( Figure 2 g and h) showed that the control group perovskite film had a large number of PbI2 characteristic diffraction peaks, indicating that the conversion of PbI2 to perovskite was incomplete; while the intensity of the PbI2 characteristic peaks in the experimental group was significantly reduced, confirming that the porous PbI2 precursor film facilitated the penetration of organic salt solution, improved the conversion efficiency of PbI2, and reduced bulk defects. Quantitative analysis of crystal orientation showed that the intensity ratio of the (111) / (100) diffraction peaks of the control group perovskite film was 0.74, while the ratio of the experimental group was greatly increased to 3.25, an increase of nearly 5 times, which fully proves that ZnOX modification can effectively induce the preferential growth of perovskite film along the (111) crystal plane.

[0036] Crystal structure analysis of perovskite grains using transmission electron microscopy (TEM) Figure 2 The results showed that the dominant crystal plane of the control group was (100), with a crystal plane spacing of 6.2 Å; while the dominant crystal plane of the experimental group was (111), with a crystal plane spacing of 3.6 Å, further confirming the inducing effect of ZnOX on the preferred growth of the (111) crystal plane. Elemental analysis results showed that there was a significant Zn element signal in the perovskite grains of the experimental group, indicating that Zn2+ in ZnOX can be embedded in the perovskite lattice, effectively compensating for lead vacancies (VPb) in the bulk phase and reducing the defect state density.

[0037] 3. Enhanced Device Performance: Dual Enhancement of Photovoltaic Performance and Stability Photovoltaic performance tests were conducted on devices with different ZnOX concentrations to determine the optimal ZnOX modification concentration of 1 mg / mL. Solar simulator tests showed that the photoelectric conversion efficiency (PCE) of the ZnOX-modified experimental group devices significantly increased from 23.22% in the control group to 25.69%. Specific photovoltaic parameters (open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, etc.) are detailed in Table 2.

[0038] Table 2. Performance of photovoltaic devices modified with different concentrations of ZnOX.

[0039]

[0040] (3.1) To evaluate the long-term stability of the device, humidity stability and light stability tests were conducted. The specific results are as follows: (a) Humidity stability: The device was placed in an air environment with a humidity of 30%-50% for long-term monitoring, and the time (T80) during which the PCE decayed to 80% of its initial value was recorded. Figure 3 As shown in figure a, the T80 of the experimental group devices exceeded 1248 h, which was much higher than the 720 h of the control group, indicating that ZnOX modification significantly improved the moisture resistance of PSCs. This performance improvement is due to the preferred growth of the (111) crystal plane induced by ZnOX, which strengthens the resistance of the perovskite film to moisture-induced degradation. Contact angle test results ( Figure 3 b, c) Further evidence: The contact angle of the perovskite film in the experimental group was 71°, which was higher than that of the control group (64°), proving that its surface hydrophobicity was enhanced and its moisture resistance was improved.

[0041] (b) Light stability: The stability of the device was tested according to the international standard ISOS-L-1 protocol under nitrogen atmosphere and continuous light illumination. Figure 3 As shown in Figure d, the experimental group device maintained over 90% of its initial efficiency after 720 hours of continuous operation; while the control group device's efficiency dropped to below 90% of its initial value after 200 hours of operation. This advantage stems from the coordination of oxalate anions with Pb²⁺ in ZnOX, which inhibits ion migration through a "lead-fixing" effect. Figure 3 The embedded I⁻ ion distribution map visually shows that: the electron transport layer / perovskite interface of the control group device shows obvious I⁻ migration, while the I⁻ migration of the experimental group is effectively suppressed, which confirms that ZnOX can improve the light stability of the device by suppressing ion migration.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing (111) preferred-oriented perovskite thin films based on substrate control, characterized in that, Includes the following steps: S1. Provide a substrate; S2. Forming a SnO2 electron transport layer on the substrate: In an air atmosphere, 70 μL of SnO2 electron transport layer dispersion is dropped onto the ITO substrate, spin-coated at 3000 rpm for 50 s, and then annealed on a hot plate at 150 °C for 25 min. S3. Forming a zinc oxalate (ZnOX) interlayer on the electron transport layer: Under a nitrogen atmosphere, 70 μL of ZnOX interlayer solution is dropped onto the surface of the SnO2 film, spin-coated at 3000 rpm for 30 s, and annealed at 100 °C for 10 min. S4. The perovskite active layer is prepared on the zinc oxalate (ZnOX) intermediate layer by a two-step sequential deposition method: first, a PbI2 layer is deposited on the ZnOX intermediate layer, and then the PbI2 layer is reacted with an organic salt solution to form a perovskite film; wherein the perovskite active layer has a (111) crystal plane preferred orientation.

2. The preparation method according to claim 1, characterized in that, The preparation steps of the SnO2 electron transport layer dispersion include: taking a SnO2 colloidal solution with a mass fraction of 15%, adding deionized water at a volume ratio of 1:3, stirring at room temperature for 30 min, and filtering through a 0.22 μm filter membrane for later use.

3. The preparation method according to claim 1, characterized in that, The method for preparing the ZnOX intermediate layer solution includes: weighing a certain amount of ZnOX powder, adding it to an HBr / DMF mixed solvent, adding a stir bar, stirring at 1000 rpm for 0.5 h at room temperature until completely dissolved, filtering through a 0.22 μm filter membrane to obtain a uniform ZnOX intermediate layer solution for subsequent spin coating; wherein the volume ratio of HBr / DMF is 50:

950.

4. The preparation method according to claim 1, characterized in that, In step S4, the preparation steps of the perovskite active layer specifically include: under a nitrogen atmosphere, adding 70 μL of PbI2 precursor solution, spin-coating at 2000 rpm for 30 s, and annealing at 70°C for 1 min; after cooling, adding 70 μL of organic salt solution, spin-coating at 1800 rpm for 30 s, transferring to an air atmosphere with a humidity of 30%–40%, and annealing at 150°C for 30 min.

5. The preparation method according to claim 4, characterized in that, The preparation steps of the PbI2 precursor solution include: dissolving 599.3 mg of PbI2 powder in a mixed solvent of 950 μL DMF and 50 μL DMSO, stirring at 70°C for 6 h until completely dissolved, and filtering through a 0.22 μm filter membrane for later use. The preparation steps of the organic salt solution include: dissolving 90 mg of FAI, 6.4 mg of MAI and 9 mg of MACl in 1 mL of isopropanol, stirring at room temperature for 30 min until completely dissolved, and filtering through a 0.22 μm filter membrane for later use.

6. A perovskite solar cell, characterized in that, Including those set up in a stacked manner: Substrate; The electron transport layer, zinc oxalate ZnOX intermediate layer, and perovskite active layer prepared by the method of any one of claims 1-5, wherein the perovskite active layer has a (111) preferred orientation. Hole transport layer formed on the perovskite active layer; And electrodes formed on the hole transport layer.

7. The perovskite solar cell according to claim 6, characterized in that, The preparation steps of the hole transport layer include: adding 50 μL of hole transport layer solution under a nitrogen atmosphere, spin-coating at 3000 rpm for 30 s, and transferring to an air drying cabinet with a humidity of 10%–20% and letting it stand overnight.

8. The perovskite solar cell according to claim 7, characterized in that, The preparation steps of the hole transport layer solution include: dissolving 72.3 mg of Spiro-OMeTAD, 17.5 μL of Li-TFSI solution and 29 μL of 4-tBP in 1 mL of chlorobenzene, filtering through a 0.22 μm filter membrane and setting aside for later use, wherein the Li-TFSI solution is 520 mg of Li-TFSI dissolved in 1 mL of acetonitrile.

9. The perovskite solar cell according to claim 6, characterized in that, The preparation steps of the gold electrode include: in 5×10 -4 Under a vacuum of Pa, an 80 nm Au thin film was thermally deposited as the back electrode to complete the device fabrication.

10. The perovskite solar cell according to claim 6, characterized in that, The average grain size of the perovskite active layer is greater than or equal to 3 μm.

Images