A mixed-halogen wide-bandgap perovskite thin film, its preparation method and application

Abstract

This invention belongs to the field of photovoltaic materials technology and discloses a mixed-halogen wide-bandgap perovskite thin film, its preparation method, and its application. The preparation method includes the following steps: first, dissolving the raw materials for preparing the mixed-halogen wide-bandgap perovskite and poly(4-hydroxystyrene) in an organic solvent to obtain a mixed-halogen wide-bandgap perovskite precursor solution; then, coating the mixed-halogen wide-bandgap perovskite precursor solution onto a conductive substrate, followed by annealing to form a mixed-halogen wide-bandgap perovskite thin film. This invention selects a specific P4VP polymeric additive containing hydroxyl functional groups. Due to its polymer properties, it can in-situ encapsulate the perovskite grain boundaries during annealing, passivating them; the reducing properties of the hydroxyl groups can reduce molecular iodine generated at the grain boundaries to iodide ions, and inhibit iodine volatilization and iodine vacancy formation, weakening the positive feedback between iodide oxidation and halide segregation, thereby significantly improving the photoelectric performance of the mixed-halogen perovskite thin film and its devices.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic materials technology, specifically relating to a mixed-halogen wide-bandgap perovskite thin film, its preparation method and application, and particularly to a method for preparing high-performance mixed-halogen wide-bandgap perovskite thin films by grain boundary regulation, as well as the prepared mixed-halogen wide-bandgap perovskite thin films and their applications. Background Technology

[0002] Mixed-halogen wide-bandgap perovskite thin films are a class of functional semiconductor materials based on the perovskite structure, which broaden their optical bandgap by mixing at least two types of halide ions. These materials are mainly used as the top absorber layer in perovskite / silicon tandem solar cells because their bandgap is tunable and their absorption spectrum complements that of narrow-bandgap bottom cells (such as silicon or tin-lead perovskite), effectively breaking through the efficiency limit of single-junction cells.

[0003] However, mixed-halogen wide-bandgap perovskite films are prone to compositional and structural instability under light and heat, caused by the heterogeneity of the grain boundary microstructure. Specifically, defects accumulate at grain boundaries, promoting halide migration. During long-term operation, halogen redistribution occurs, such as the formation of an iodine-rich, low-bandgap phase at grain boundaries and a bromine-rich phase within the grains. The iodine-rich regions induce vacancy accumulation, further promoting the migration of iodide ions to the grain boundaries and triggering iodide oxidation to molecular iodine. The partial volatilization of molecular iodine causes irreversible iodine loss, while simultaneously introducing iodine vacancies and establishing a concentration gradient, further exacerbating halide migration and phase separation. Thus, halide phase segregation, iodide oxidation, vacancy formation, and halide loss are coupled, forming a self-reinforcing degradation cycle. Existing stabilization methods for small molecules or ordinary polymers are insufficient to simultaneously achieve grain boundary sealing, redox regulation, and long-term suppression of iodine loss.

[0004] Therefore, there is an urgent need to develop a new method for preparing mixed-halogen wide-bandgap perovskite thin films to improve the efficiency and stability of mixed-halogen wide-bandgap perovskite solar cells. Summary of the Invention

[0005] This invention addresses the performance degradation problem caused by halogen phase separation in existing mixed-halogen wide-bandgap perovskite films. It proposes a mixed-halogen wide-bandgap perovskite film, its preparation method, and its application. The preparation method uses additive engineering to control grain boundary defects in the mixed-halogen wide-bandgap perovskite film, which significantly improves the photoelectric performance of the film, thereby effectively enhancing the efficiency and stability of mixed-halogen wide-bandgap perovskite solar cells.

[0006] The inventive concept of this invention is as follows: Through additive engineering, an appropriate concentration of poly(4-hydroxystyrene) (P4VP) is added to the mixed halide perovskite precursor solution. On the one hand, the hydroxyl functional groups contained in the polymer are used to reduce molecular iodine generated at the grain boundary to iodide ions, thereby inhibiting iodine volatilization and iodine vacancy formation from the source and weakening the positive feedback between iodide oxidation and halide segregation. On the other hand, by leveraging the synergistic effect of polymer encapsulation and redox regulation, the self-reinforcing degradation loop of halide segregation-iodine oxidation-halide loss is broken, thereby improving the photothermal stability and operational durability of perovskite thin films and photovoltaic devices.

[0007] Therefore, this invention selects specific P4VP polymeric additives containing hydroxyl functional groups and utilizes their polymer properties to in-situ encapsulate perovskite grain boundaries during annealing, thereby passivating them. At the same time, the reducing properties of the hydroxyl groups are used to reduce molecular iodine generated at the grain boundaries to iodide ions, and to suppress iodine volatilization and iodine vacancy formation, thereby weakening the positive feedback between iodide oxidation and halide segregation. The combined effect of these two factors significantly improves the photoelectric properties of mixed halide perovskite films and their devices.

[0008] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing a mixed-halogen wide-bandgap perovskite thin film, comprising the following steps: (1) Dissolve the raw materials for preparing mixed halogen wide-bandgap perovskite and poly(4-hydroxystyrene) in an organic solvent to obtain a mixed halogen wide-bandgap perovskite precursor solution; (2) The mixed halogen wide-bandgap perovskite precursor solution is coated onto a conductive substrate and then annealed to form the mixed halogen wide-bandgap perovskite film.

[0009] In some embodiments of the present invention, the poly(4-hydroxystyrene) has the structural formula shown in formula (1): Equation (1) Wherein: n is a positive integer, and the weight-average molecular weight of the poly(4-hydroxystyrene) is 10000-12000.

[0010] The CAS number for poly(4-hydroxystyrene) is 24979-70-2, and its molecular formula is [CH2CH(C6H4OH)]. n .

[0011] In some embodiments of the present invention, the general chemical formula of the mixed-halogen wide-bandgap perovskite is: ABX3, where: A represents Cs. + FA + MA + At least one of them; B represents Pb 2+ Sn 2+ At least one of them; X represents Cl- ,Br - I - At least two of them.

[0012] In some embodiments of the present invention, the raw materials for preparing the mixed-halogen wide-bandgap perovskite include cesium iodide, formamide iodide, lead bromide, and lead iodide.

[0013] In some embodiments of the present invention, the organic solvent is a mixed solution of dimethylformamide and dimethyl sulfoxide.

[0014] In some embodiments of the present invention, the volume ratio of dimethylformamide to dimethyl sulfoxide is (2-4):1.

[0015] In some embodiments of the present invention, the concentration of the mixed halogen wide-bandgap perovskite precursor solution is 1.3-1.5 mol / L. For example, the concentration of the solution can be 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, etc., including but not limited to the listed values, and other values ​​not listed are also applicable within the numerical range.

[0016] In some embodiments of the present invention, the concentration of poly(4-hydroxystyrene) in the mixed halogen wide-bandgap perovskite precursor solution is 0.25-2 mg / mL. For example, the concentration of poly(4-hydroxystyrene) can be 0.25 mg / mL, 0.50 mg / mL, 1.00 mg / mL, 1.50 mg / mL, 2.00 mg / mL, etc., including but not limited to the listed values, and other values ​​not listed are also applicable within the numerical range.

[0017] In some embodiments of the present invention, the concentration of poly(4-hydroxystyrene) in the mixed halogen wide-bandgap perovskite precursor solution is 0.25-1.00 mg / mL.

[0018] In some embodiments of the present invention, the concentration of poly(4-hydroxystyrene) in the mixed halogen wide-bandgap perovskite precursor solution is 0.25-0.50 mg / mL.

[0019] In some embodiments of the present invention, the coating process is as follows: first spin coating at a speed of 900-1100 rpm for 15-25 seconds; then spin coating at a speed of 3800-4200 rpm for 25-35 seconds; and finally, in the last 8-12 seconds, dropping ethyl acetate onto the conductive substrate.

[0020] In some embodiments of the present invention, the annealing process is performed at 80-120°C for 20-40 minutes.

[0021] In some embodiments of the present invention, the conductive substrate is ITO conductive glass coated with a hole transport layer.

[0022] In some embodiments of the present invention, the preparation process of the ITO conductive glass coated with a hole transport layer includes the following steps: 1) Sonicate the ITO conductive glass with acetone, isopropanol, deionized water and ethanol alternately for 10-20 minutes. 2) The ITO conductive glass treated in step 1) is dried by blowing with nitrogen gas, and then subjected to ultraviolet ozone treatment for 10-20 min. A hole transport layer is then deposited on its surface. The deposition process of the hole transport layer is as follows: a nickel oxide film with a thickness of 15-25 nm is prepared by magnetron sputtering at a sputtering power of 60-70 W; the Me-4PACz hole transport layer material is dissolved in ethanol at a concentration of 1 mg / mL, filtered and set aside; 120 μL of the solution is dropped onto the surface of the ITO / nickel oxide substrate, and then spin-coated at 2800-3200 rpm for 28-32 s, followed by annealing at 95-105℃ for 8-12 min to obtain the ITO glass coated with the hole transport layer.

[0023] A second aspect of the present invention provides a mixed-halogen wide-bandgap perovskite thin film, prepared by the method described in the first aspect of the present invention. The mixed-halogen wide-bandgap perovskite thin film prepared by the method of the present invention exhibits higher photoelectric properties and stability compared to conventional mixed-halogen wide-bandgap perovskite thin films.

[0024] A third aspect of the present invention provides a photovoltaic device comprising the mixed-halogen wide-bandgap perovskite thin film described in the second aspect of the present invention.

[0025] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) This invention proposes a method to suppress halogen phase separation in mixed halide wide-bandgap perovskite films by grain boundary regulation. This method uses additive engineering to add an appropriate concentration of poly(4-hydroxystyrene) to the mixed halide perovskite precursor solution. The hydroxyl functional groups contained in the polymer reduce molecular iodine generated at the grain boundary to iodide ions, thereby suppressing iodine volatilization and iodine vacancy formation from the source and weakening the positive feedback between iodide oxidation and halide segregation. With the synergistic effect of polymer encapsulation and redox regulation, the self-reinforcing degradation loop of halide segregation-iodine oxidation-halide loss is broken, thereby improving the photothermal stability and operational durability of perovskite films and photovoltaic devices.

[0026] (2) The present invention selects a specific P4VP polymeric additive containing hydroxyl functional groups, which has a better passivation effect on mixed halide wide-bandgap perovskite films compared with traditional polymer additives (such as PMMA); in addition, the hydroxyl group in the polymer has a reducing property, which significantly improves the photoelectric performance of mixed halide perovskite films and their devices. Attached Figure Description

[0027] Figure 1 The UV-Vis absorption spectra are of pure molecular iodine solution and molecular iodine solution after adding P4VP. Figure 2 A comparison of the solubility of PMMA and P4VP in a mixed solvent of DMF and DMSO; Figure 3 The Fourier transform infrared spectra of the perovskite thin films prepared in Example 1 and Comparative Example 1 of this invention are shown below. Figure 4 Atomic force microscopy images of the perovskite films prepared in Example 1 and Comparative Example 1 of this invention. Figure 5 TRPL mapping of the perovskite thin films prepared in Example 1 and Comparative Example 1 of this invention; Figure 6 The results are the in-situ PL test results of the perovskite thin films prepared in Example 1 and Comparative Example 1 of this invention. Figure 7 The UV-Vis absorption spectra of the perovskite films prepared in Example 1 and Comparative Example 2 of this invention are shown below. Figure 8 The photoelectric performance of single-junction perovskite solar cells based on perovskite thin films prepared in Examples 1-4 and Comparative Example 1 of this invention is shown in the figure. Figure 9 The results show the device structure and performance characterization of single-junction perovskite solar cells based on the perovskite thin films prepared in Example 1 and Comparative Example 1 of this invention. Figure 10 The results show the structural and performance characterization of perovskite / polycrystalline silicon tandem solar cells prepared based on the perovskite thin films of Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0029] Example 1 A method for preparing a mixed-halogen wide-bandgap perovskite thin film includes the following steps: (1) The ITO glass substrate was ultrasonically cleaned sequentially with acetone, isopropanol, deionized water and ethanol for 15 min each time. Then, the ITO glass substrate was dried with nitrogen gas and subjected to ultraviolet ozone treatment for 15 min to further clean and activate the substrate surface, and then a hole transport layer was deposited on it. A nickel oxide film with a thickness of 15 nm was prepared by magnetron sputtering at a sputtering power of 65 W. The Me-4PACz hole transport layer material was dissolved in ethanol at a concentration of 1 mg / mL, filtered and set aside; 120 μL of the solution was dropped onto the surface of the ITO / nickel oxide substrate, and then spin-coated at 3000 rpm for 30 s, followed by annealing at 100 °C for 10 min to obtain ITO conductive glass coated with a hole transport layer.

[0030] (2) Take 61.83 mg of cesium iodide, 199.83 mg of formamide iodide, 154.14 mg of lead bromide, 451.79 mg of lead iodide and 0.5 mg of P4VP, dissolve them in 1 μL of a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (the volume ratio of DMF to DMSO is 3:1) to prepare a mixed halogen wide-bandgap perovskite precursor solution with a concentration of 1.4 mol / L.

[0031] (3) Drop 100 μL of the mixed halogen wide bandgap perovskite precursor solution obtained in step (2) onto the ITO conductive glass coated with the hole transport layer obtained in step (1), and then rapidly rotate and coat it at a speed of 5000 rpm for 30 s. In the last 5 s, drop 200 μL of ethyl acetate onto the ITO conductive glass. Finally, anneal at 100 °C for 30 min to obtain the mixed halogen wide bandgap perovskite film of this embodiment.

[0032] Example 2 Referring to the preparation method of Example 1, only the amount of P4VP in step (2) was changed to 0.25 mg to obtain the mixed halogen wide-bandgap perovskite film of this example.

[0033] Example 3 Referring to the preparation method of Example 1, only the amount of P4VP in step (2) was changed to 1.00 mg to obtain the mixed halogen wide-bandgap perovskite film of this example.

[0034] Example 4 Referring to the preparation method of Example 1, only the amount of P4VP in step (2) was changed to 2.00 mg to obtain the mixed halogen wide-bandgap perovskite film of this example.

[0035] Comparative Example 1 A method for preparing a mixed-halogen wide-bandgap perovskite thin film includes the following steps: (1) The ITO glass substrate was ultrasonically cleaned sequentially with acetone, isopropanol, deionized water and ethanol for 15 min each time. Then, the ITO glass substrate was dried with nitrogen gas and subjected to ultraviolet ozone treatment for 15 min to further clean and activate the substrate surface, and then a hole transport layer was deposited on it. A nickel oxide film with a thickness of 15 nm was prepared by magnetron sputtering at a sputtering power of 65 W. The Me-4PACz hole transport layer material was dissolved in ethanol at a concentration of 1 mg / mL, filtered and set aside; 120 μL of the solution was dropped onto the surface of the ITO / nickel oxide substrate, and then spin-coated at 3000 rpm for 30 s, followed by annealing at 100 °C for 10 min to obtain ITO conductive glass coated with a hole transport layer.

[0036] (2) Take 61.83 mg of cesium iodide, 199.83 mg of formamide iodide, 154.14 mg of lead bromide and 451.79 mg of lead iodide, dissolve them in 1 μL of a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (the volume ratio of DMF to DMSO is 3:1) to prepare a mixed halogen wide-bandgap perovskite precursor solution with a concentration of 1.4 mol / L.

[0037] (3) Drop 100 μL of the mixed halogen wide bandgap perovskite precursor solution obtained in step (2) onto the ITO conductive glass coated with the hole transport layer obtained in step (1), and then rapidly rotate and coat it at a speed of 5000 rpm for 30 s. In the last 5 s, drop 200 μL of ethyl acetate onto the ITO conductive glass. Finally, anneal at 100 °C for 30 min to obtain the mixed halogen wide bandgap perovskite film of this comparative example.

[0038] Comparative Example 2 Following the preparation method of Example 1, only the 0.5 mg of P4VP in step (2) was replaced with 0.5 mg of polymethyl methacrylate (PMMA, CAS: 9011-14-7, molecular formula: [C5H8O2]). nThe mixed-halogen wide-bandgap perovskite thin film of this comparative example was prepared.

[0039] Application Example 1 Single-junction perovskite solar cells were fabricated using the perovskite thin films prepared in Examples 1-4 and Comparative Examples 1-2, respectively. The specific steps are as follows: A 0.3 mg / mL PI isopropanol solution was dropwise added to the surfaces of the perovskite films prepared in Examples 1-4 and Comparative Examples 1-2, respectively. The films were then spin-coated at 5000 rpm for 30 s and annealed at 100°C for 10 min to form an interface modification layer. Subsequently, an electron transport layer and an electrode layer were sequentially deposited on top of the perovskite layer using a thermal evaporation process. Specifically, a 20 nm thick C layer was first deposited. 60 A layer is deposited, followed by an 8nm thick BCP layer, and finally a 100nm thick silver electrode layer to fabricate a single-junction perovskite solar cell. A schematic diagram of its structure is shown below. Figure 9 Part a in the text.

[0040] Application Example 2 The perovskite thin films prepared in Examples 1-4 and Comparative Examples 1-2 were used to fabricate mixed-halogen wide-bandgap perovskite solar cells on silicon substrates. The specific steps are as follows: After fabricating a normal hole transport layer and perovskite layer on a silicon substrate, a 20nm C layer was sequentially deposited on the upper interface transport layer of the perovskite. 60 A perovskite / polycrystalline silicon tandem solar cell was fabricated using a 20nm ALD-SnO2 layer, a 100nm indium zinc oxide (IZO) layer, a 300nm silver layer, and a 100nm MgF2 contact layer. A schematic diagram of its structure is shown below. Figure 10 Part a in the text.

[0041] Performance testing 1. P4VP characteristics The ability of P4VP to reduce I2 was evaluated to verify its regulatory role in iodine-related degradation processes in mixed halide perovskites. Figure 1 The graphs show the UV-Vis absorption spectra of pure molecular iodine solution and molecular iodine solution with added P4VP (P4VP concentration 4 mg / mL). The horizontal axis represents wavelength, and the vertical axis represents emissivity. Figure 1 It can be seen that after adding solid P4VP to the iodine solution, the UV-Vis absorption spectrum changed significantly, and the solution transmittance increased significantly, indicating that the yellow molecular iodine (I2) was effectively reduced to colorless iodide ions (I3). - This demonstrates that P4VP has a strong iodine reducing ability.

[0042] The solubility of P4VP and PMMA in a mixed solvent of DMF and DMSO at a volume ratio of 3:1 was compared, and the results are as follows: Figure 2 As shown. Figure 2 The results showed that under the same conditions, a large number of PMMA particles were observed, while P4VP was completely dissolved. This indicates that the amount of PMMA added in the solvent is limited, which restricts the passivation effect of PMMA on perovskite films with high concentrations of defects. P4VP, on the other hand, exhibits better solubility in DMF and DMSO, which is beneficial for improving its solvation behavior and dispersion uniformity in perovskite precursor solutions, providing a basis for its effective introduction during film formation.

[0043] After confirming that P4VP possesses reducing properties and good solvation characteristics, its distribution in perovskite films was further investigated, and the results are as follows: Figure 3 As shown. Figure 3 Fourier transform infrared spectroscopy was used to observe a region located at 1602 cm⁻¹ in the P₄VP-containing perovskite film prepared in Example 1. -1 The obvious characteristic absorption peak at the point is attributed to the C=C vibration; however, this characteristic peak was not observed in the perovskite film without P4VP prepared in Comparative Example 1, indicating that P4VP has been successfully introduced into the perovskite film.

[0044] 2. Thin film properties Figure 4 At 1602 cm -1 Atomic force microscopy morphology images of the region corresponding to the C=C stretching vibration, where, Figure 4 Parts a and b in the figure are surface morphology height diagrams of the perovskite films prepared in Comparative Example 1 (Control) and Example 1 (P4VP), respectively. Figure 4 0nm represents the average surface height; Figure 4 Parts c and d are atomic force microscopy images of the corresponding regions of the perovskite films prepared in Comparative Example 1 and Example 1, respectively.

[0045] Figure 5 Parts a and b show the TRPL mapping of the perovskite films prepared in Example 1 (P4VP) and Comparative Example 1 (Control), respectively. The results show that the film treated with P4VP has a longer lifetime, indicating improved film quality. Furthermore, the standard deviation of the lifetime of the Control film was 7.23 ns, while the standard deviation of the lifetime of the perovskite film treated with P4VP decreased to 4.64 ns, indicating that P4VP treatment helps improve the uniformity of the perovskite film, thereby forming a more uniform perovskite layer.

[0046] Figure 6The in-situ photoluminescence (PL) test results for the perovskite films prepared in Example 1 (P4VP), Comparative Example 1 (Control), and Comparative Example 2 (PMMA) over 59 minutes are shown. The horizontal axis represents time, and the vertical axis represents normalized intensity. Specifically, the PL peak position of the Control film shifted from 743 nm to 754 nm, while the PL peak position of the P4VP-modified film only shifted from 741 nm to 742 nm, indicating that P4VP can effectively suppress photoinduced halide phase separation in the perovskite film. Furthermore, the PMMA-modified film prepared with hydroxyl-free polymethyl methacrylate exhibited more pronounced halogen phase separation under the same conditions than P4VP.

[0047] The perovskite films prepared in Example 1 (P4VP), Comparative Example 1 (Control), and Comparative Example 2 (PMMA) were placed in sealed test tubes containing chlorobenzene (CBZ) and aged on a hot plate at 85°C under simulated sunlight (1x solar radiation) for 120 h. After the solution cooled to room temperature, the chlorobenzene was analyzed by UV-Vis absorption spectroscopy, and the results are as follows. Figure 7 As shown. Figure 7 The results show that introducing P4VP can significantly reduce the I2 concentration during the photodegradation process of the thin film. Furthermore, while introducing PMMA can reduce the I2 concentration during photodegradation through grain encapsulation via grain boundary passivation, PMMA cannot suppress I2 formation mediated by inherent defects in perovskites due to the lack of reducing groups. Therefore, the I2 concentration of the thin film prepared with PMMA after photodegradation is higher than that of the thin film prepared with P4VP.

[0048] 3. Battery performance Figure 8 The graph shows the photoelectric performance of single-junction perovskite solar cells prepared based on perovskite thin films of Examples 1-4 and Control 1, using P4VP precursor solutions of different concentrations. Figure 8 Displays the average open-circuit voltage (V) of the perovskite solar cell without P4VP (Control). oc The voltage is 1.22V, and the average short-circuit current density (J) is... sc The value is 21.47 mA / cm. 2 The average fill factor (FF) was 81.15%, and the average power conversion efficiency (PCE) was 21.17%. In contrast, after adding P4VP, the device performance showed a trend of first increasing and then decreasing with increasing P4VP concentration. The device performance was optimal when the P4VP concentration was 0.5 mg / mL, with an average open-circuit voltage of 1.25 V and an average short-circuit current density of 21.94 mA / cm². 2The average fill factor was 84.35%, and the champion device achieved a photoelectric conversion efficiency of 23.15%. When the concentration of P4VP was further increased, the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the device all decreased to some extent.

[0049] Figure 9 The results represent the device structure and performance characterization of single-junction perovskite solar cells based on the perovskite thin films prepared in Example 1 (P4VP) and Comparative Example 1 (Control). Figure 9 The introduction of P4VP significantly improved the photoelectric properties and photothermal stability of the perovskite thin film. Therefore, control devices without P4VP and wide-bandgap perovskite solar cells with P4VP were fabricated, respectively. The device structure is ITO / NiO. x / Me-4PACz / Cs 0.17 FA 0.83 Pb(I 0.80 Br 0.20 )3 / PI / C 60 / BCP / Ag. Figure 9 Part b shows that the device with added P4VP outperforms the control device in all key performance indicators, with a particularly significant improvement in fill factor (FF). Specifically, the photoelectric conversion efficiency (PCE) of the device with added P4VP increases from 21.78% for the control device to 23.42%, an improvement of approximately 1.64%. Figure 9 Section c also shows that under steady-state test conditions, the stable photoelectric conversion efficiency (PCE of control blased at 1.04V) of the control device is 21.08%; while the stable PCE of control blased at 1.11V with the P4VP device added is 22.65%. These results are consistent with those obtained using reverse scanning. J - V The photoelectric conversion efficiencies obtained from the tests are basically consistent, indicating that the devices have good consistency under dynamic and steady-state testing conditions. Figure 9 The d-section represents the external quantum efficiency (EQE) spectrum of the corresponding device. The short-circuit current density (Integrated J) is calculated based on the integral of the EQE spectrum. sc In this context, the control device has an A / cm value of 21.39. 2 Adding a P4VP device results in an A / cm² of 21.81 mA. 2 .

[0050] Figure 10The following are the structural and performance characterization results of perovskite / polycrystalline silicon tandem solar cells based on perovskite thin films prepared in Example 1 (P4VP) and Comparative Example 1 (Control), wherein: Figure 10 Part b of the figure shows a performance comparison of the tandem solar cell before and after the addition of P4VP. The reverse scanning photoelectric conversion efficiency of the tandem solar cell with added P4VP is 33.18%, and the open-circuit voltage is 1.97V at 1.00cm. 2 The steady-state photoelectric conversion efficiency under effective area is 32.88%; the photoelectric conversion efficiency and steady-state photoelectric conversion efficiency of the Control tandem cell are 30.94% and 30.53%, respectively. Figure 10 Part c in the figure shows the EQE spectrum of the control tandem solar cell, where the current densities of the perovskite top cell and the silicon bottom cell are 20.43 mA / cm². 2 and 20.44 mA / cm 2 . Figure 10 Part d in the figure represents the long-term operational stability test results of the packaged series devices under the conditions of room temperature, nitrogen environment and continuous simulated sunlight (1 times solar radiation). Among them, the stacked cell with P4VP added still retains more than 95% of its initial performance after 1000h.

[0051] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for preparing a mixed-halogen wide-bandgap perovskite thin film, characterized in that, Includes the following steps: (1) Dissolve the raw materials for preparing mixed halogen wide-bandgap perovskite and poly(4-hydroxystyrene) in an organic solvent to obtain a mixed halogen wide-bandgap perovskite precursor solution; (2) The mixed halogen wide-bandgap perovskite precursor solution is coated onto a conductive substrate and then annealed to form the mixed halogen wide-bandgap perovskite film.

2. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 1, characterized in that, The structural formula of the poly(4-hydroxystyrene) is shown in formula (1): Equation (1) Wherein: n is a positive integer, and the weight-average molecular weight of the poly(4-hydroxystyrene) is 10000-12000.

3. The method for preparing mixed-halogen wide-bandgap perovskite thin films according to claim 1, characterized in that, The general chemical formula of the mixed-halogen wide-bandgap perovskite is: ABX3, where: A represents Cs. + FA + MA + At least one of them; B represents Pb 2+ Sn 2+ At least one of them; X represents Cl - ,Br - I - At least two of them.

4. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 1, characterized in that, The organic solvent is a mixed solution of dimethylformamide and dimethyl sulfoxide, and the concentration of the mixed halogen wide-bandgap perovskite precursor solution is 1.3-1.5 mol / L.

5. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 4, characterized in that, In the mixed halogen wide-bandgap perovskite precursor solution, the concentration of poly(4-hydroxystyrene) is 0.25-2 mg / mL.

6. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 1, characterized in that, The coating process is as follows: first, spin coating at a speed of 900-1100 rpm for 15-25 seconds; then spin coating at a speed of 3800-4200 rpm for 25-35 seconds; and finally, drop ethyl acetate onto the conductive substrate in the last 8-12 seconds.

7. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 1, characterized in that, The annealing process is carried out at 80-120℃ for 20-40 minutes.

8. The method for preparing a mixed-halogen wide-bandgap perovskite thin film according to claim 1, characterized in that, The conductive substrate is ITO conductive glass coated with a hole transport layer.

9. A mixed-halogen wide-bandgap perovskite thin film, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A photovoltaic device, characterized in that, Includes the mixed-halogen wide-bandgap perovskite thin film as described in claim 9.

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