Zinc-doped perovskite down-conversion thin film, preparation method and application of zinc-doped perovskite down-conversion thin film in solar cell

Abstract

The invention discloses a zinc-doped perovskite down-conversion thin film, a preparation method and application of the zinc-doped perovskite down-conversion thin film in a solar cell, and belongs to the technical field of solar cells. According to the invention, the zinc ions with a specific molar ratio are introduced into the perovskite precursor, so that the crystallization behavior is effectively regulated and controlled, and the high-quality thin film with compact surface, uniform crystal grains and low defect density is prepared. The average transmittance of the film is larger than 86%, the photoluminescence efficiency is larger than 58%, and ultraviolet light can be efficiently converted into visible light. When the solar cell is integrated on the light incident surface of the perovskite solar cell, the short-circuit current density and the photoelectric conversion efficiency of the cell can be remarkably improved, and the stability of the device is enhanced. The method is simple in process, low in cost and good in compatibility with an existing solution processing technology, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and particularly relates to a zinc-doped perovskite downconversion thin film, its preparation method, and its application in solar cells. Background Technology

[0002] The photoelectric conversion efficiency of solar cells is fundamentally limited by the ability of their active layer to utilize the solar spectrum. In particular, ultraviolet photons, which account for about 5% of the total solar energy, have higher energy than the band gap of common light-absorbing materials such as perovskites. They cannot be effectively absorbed to generate photogenerated carriers and instead lose energy through thermal processes, which may also cause photodegradation of the material. This restricts further improvement of cell efficiency and long-term operational stability.

[0003] To utilize this portion of ultraviolet light and mitigate its harmful effects, downconversion technology has emerged. This technology aims to introduce a functional layer at the cell's light incident interface, converting high-energy ultraviolet photons into two or more low-energy visible photons that can be efficiently absorbed by the cell, thereby simultaneously achieving spectral gain and device protection. Among numerous downconversion materials, halide perovskites are considered highly promising candidates due to their high luminous efficiency, tunable bandgap, and ease of solution processing.

[0004] However, applying perovskite materials to downconversion layers faces a long-standing and unresolved core contradiction: the difficulty in synergistically optimizing film quality and luminescence performance. Specifically, when preparing perovskite films using low-cost spin-coating, the crystallization process is highly random and uncontrollable, easily leading to microstructures with inconsistent grain sizes, rough surfaces, and numerous pores and grain boundary defects. These defects, acting as powerful nonradiative recombination centers, severely quench the material's high photoluminescence quantum yield, resulting in actual downconversion efficiency far below theoretical expectations. This leads to a dilemma: sacrificing luminescence intensity for film continuity, or tolerating a porous film to enhance luminescence intensity.

[0005] Existing technologies attempt to improve upon these technologies through various pathways. For example, while rare-earth organic complexes (such as CN112201757A) exhibit certain luminescent properties, their organic ligands are prone to photochemical degradation under long-term ultraviolet irradiation, leading to rapid decay of down-conversion function and questionable stability. Other approaches shift towards using inorganic rare-earth oxides (such as CN105957966A) or constructing complex multilayer doped structures. However, these methods often involve cumbersome preparation processes, high energy consumption, or expensive raw materials, contradicting the photovoltaic industry's core demand for low-cost, large-area manufacturing.

[0006] While the closest existing technology (such as CN105895726A) proposes the concept of using perovskite thin films as downconversion layers, it relies entirely on the original film formation process and does not provide any effective means to actively control the crystallization process to fundamentally and synergistically improve the morphology quality and luminescence efficiency of the thin film. Therefore, its effect is highly random and lacks repeatability and universality.

[0007] In summary, there is an urgent need in this field for a new method for preparing perovskite downconversion thin films that can start from the source of material preparation, actively guide and optimize the crystallization behavior of perovskites through innovative material modification strategies, thereby overcoming the inherent contradiction between poor film quality and low luminous efficiency, while simultaneously taking into account stability, process economy and device integration effect. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a zinc-doped perovskite downconversion thin film and its application in solar cells, solving the technical problem that "it is difficult to optimize the film quality and photoluminescence efficiency in the spin-coating process of perovskite downconversion thin film", and improving the photoelectric conversion efficiency and long-term operational stability of perovskite solar cells.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a method for preparing a zinc-doped perovskite downconversion thin film, comprising the following steps: (1) Provide a transparent substrate; (2) The perovskite precursor and N,N-dimethylformamide are mixed to prepare a first solution; the zinc salt additive and N,N-dimethylformamide are mixed to prepare a second solution, and the first solution and the second solution are mixed to obtain a precursor solution; (3) The precursor solution is coated on one surface of the transparent substrate and dried to form the zinc-doped perovskite downconversion film.

[0010] Specifically, the zinc salt additive in step (2) is one of zinc acetate, zinc chloride, zinc nitrate, and zinc acetylacetonate.

[0011] Specifically, the perovskite precursor in step (2) includes methylamine bromide and lead bromide.

[0012] Specifically, in step (2), the mass ratio of methylamine bromide to lead bromide is 1:(3-4).

[0013] Specifically, in step (2), the molar ratio of zinc ions in the second solution to lead ions in the first solution is (0.83~1.43%):1.

[0014] Specifically, in step (3), the coating is spin-coated, and the spin-coating is performed on the other side of the transparent substrate where no conductive layer has been formed.

[0015] Specifically, the spin coating speed is 3000-5000 r / min, and the spin coating time is 20-40 s.

[0016] In a second aspect, the present invention provides a zinc-doped perovskite downconversion thin film, which is prepared by the preparation method described above.

[0017] A third aspect of the present invention provides a perovskite solar cell comprising, from bottom to top, the following stacked layers: a zinc-doped perovskite downconversion thin film as described in the second aspect of the present invention, a transparent substrate, a hole transport layer, a perovskite absorber layer, an electron transport layer, and an electrode.

[0018] A fourth aspect of the present invention provides a method for preparing a perovskite solar cell, comprising the following steps: (1) Provide a transparent substrate; (2) A zinc-doped perovskite downconversion thin film is formed on one surface of the transparent substrate using the preparation method described in the first aspect of the present invention; (3) On the other surface of the transparent substrate, a hole transport layer, a perovskite absorber layer, an electron transport layer and an electrode are prepared in sequence to finally complete the preparation of the perovskite solar cell.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention significantly improves the crystal quality and microstructure of perovskite downconversion films by introducing a specific proportion of zinc ions into the precursor. The resulting film has increased surface coverage, enhanced grain size uniformity, and significantly reduced density of defects such as internal pores and grain boundaries. This allows the film to maintain high average transmittance while effectively improving photoluminescence intensity and photoluminescence efficiency.

[0020] 2. The zinc ion-doped perovskite downconversion thin film prepared by this invention is integrated into the light incident surface of a perovskite solar cell, which can efficiently convert ultraviolet light into visible light and enhance spectral utilization. Due to its all-inorganic composition and the stabilizing effect of zinc ions on the crystal lattice, it exhibits superior photostability. This dense thin film layer can block some water, oxygen and harmful ultraviolet photons, which helps to improve the long-term reliability of the device.

[0021] 3. The preparation method described in this invention is simple, the zinc salt additive is inexpensive and readily available, no complex equipment or post-processing steps are required, it is fully compatible with the solution processing technology of mainstream perovskite batteries, and is suitable for large-area preparation and industrial application. Attached Figure Description

[0022] Figure 1The diagram shows the structure of the perovskite solar cells in Examples 6-8 and Comparative Example 3.

[0023] Figure 2 The images show the XRD patterns of the perovskite downconversion films of Example 2 and Comparative Example 1.

[0024] Figure 3 SEM images of the perovskite downconversion films of Example 2 and Comparative Example 1.

[0025] Figure 4 The photoluminescence intensity of the perovskite downconversion films of Example 2 and Comparative Example 1 at different wavelengths is shown.

[0026] Figure 5 The image shows the IV curves of the perovskite solar cells of Comparative Example 3 and Example 7.

[0027] Among them, 0 is a zinc-doped perovskite downconversion thin film; 1 is an ITO glass substrate; 2 is a hole transport layer; 3 is a perovskite absorber layer; 4 is an electron transport layer; 5 is a hole blocking layer; and 6 is an electrode. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0029] This invention provides a method for preparing zinc-doped perovskite downconversion thin films, the method comprising the following steps: (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0030] (2) Mix methylamine bromide, lead bromide and N,N-dimethylformamide at a mass ratio of 1:(3-3.5):(5-8) and stir at 25-30℃ for 1-2 hours to obtain a first solution; mix zinc acetate and N,N-dimethylformamide at a mass ratio of 1:(100-130) and stir at 25-30℃ for 1-2 hours to obtain a second solution; mix the first solution and the second solution and continue stirring for 5 minutes to obtain a precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 3000-5000 r / min for 20-40 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0031] Preferably, the mass ratio of methylamine bromide, lead bromide, and N,N-dimethylformamide is 1:3.3:7.

[0032] Preferably, the mass ratio of zinc acetate to N,N-dimethylformamide is 1:120.

[0033] Preferably, the molar ratio of zinc ions in the second solution to lead ions in the first solution is (0.83~1.44%):1, and the molar ratio of zinc ions in the second solution to lead ions in the first solution is further preferably 0.01:1.

[0034] Preferably, both the first solution and the second solution are stirred at 25°C for 2 hours.

[0035] Preferably, the spin coating speed is 4000 r / min.

[0036] Preferably, the spin coating time is 30 seconds.

[0037] Specific examples Figure 1 As shown in (a), the perovskite solar cell comprises, from bottom to top, the following layers stacked sequentially: a zinc-doped perovskite downconversion film, a transparent substrate, a hole transport layer, a perovskite film absorber layer, an electron transport layer, a hole blocking layer, and an electrode, as described above.

[0038] This invention also provides a method for preparing a perovskite solar cell, comprising the following steps: (1) A zinc-doped perovskite downconversion thin film was prepared on one side of an ITO glass substrate using the method described above; (2) Add 1.5 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] to 1 mL of chlorobenzene, spin coat it on the other side of the ITO glass substrate at a speed of 4000 r / min for 20-40 s, and then dry it at 90-110 °C for 10-15 min to prepare the hole transport layer; (3) Lead iodide, methyl iodide, acrylamide, N,N-dimethylformamide and dimethyl sulfoxide are mixed in a mass ratio of (12.5-13.5):(3.2-3.6):1:9.5:0.5 and stirred thoroughly to obtain a perovskite precursor solution; then the perovskite precursor solution is spin-coated at a speed of 4000 r / min for 20 s and annealed at 90-110℃ for 10-20 min to obtain a perovskite absorber layer; (4) Using the thermal evaporation method, C 25nm layers were deposited sequentially. 60 The perovskite solar cell was fabricated by preparing a hole blocking layer, depositing a 5nm BCP (bath copper spirit) layer to prepare an electron transport layer, and depositing a 100nm Ag layer to prepare an electrode.

[0039] In step (2), the spin coating time is 20 to 40 seconds, preferably 30 seconds.

[0040] In step (2), the drying temperature is 90-110°C and the drying time is 10-15 min, preferably the drying temperature is 100°C and the drying time is 10 min.

[0041] In step (3), the annealing temperature is 90-110°C and the annealing time is 10-20 min, preferably the annealing temperature is 100°C and the annealing time is 15 min.

[0042] As a preferred embodiment of the present invention, the mass ratio of lead iodide, methyl iodide, acrylamide, N,N-dimethylformamide and dimethyl sulfoxide is 13:3.4:1:9.5:0.5.

[0043] Example 1: A zinc-doped perovskite downconversion thin film (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0044] (2) Mix 166.7 mg of methyl bromide, 500 mg of lead bromide and 0.88 mL of N,N-dimethylformamide evenly and stir at 30 °C for 1 h to obtain the first solution; mix 2.5 mg of zinc acetate and 318 μL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the second solution; mix the first solution and the second solution and continue stirring for 5 min to obtain the precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 3000 r / min for 20 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0045] Example 2; A zinc-doped perovskite downconversion thin film (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0046] (2) Mix 151.5 mg of methyl bromide, 500 mg of lead bromide and 1.1 mL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the first solution; mix 2.5 mg of zinc acetate and 318 μL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the second solution; mix the first solution and the second solution and continue stirring for 5 min to obtain the precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 4000 r / min for 30 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0047] Example 3: A zinc-doped perovskite downconversion thin film (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0048] (2) Mix 166.7 mg of methyl bromide, 500 mg of lead bromide and 0.88 mL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the first solution; mix 2.5 mg of zinc acetate and 318 μL of N,N-dimethylformamide evenly and stir at 30 °C for 1 h to obtain the second solution; mix the first solution and the second solution and continue stirring for 5 min to obtain the precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 5000 r / min for 40 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0049] Example 4: A zinc-doped perovskite downconversion thin film (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0050] (2) Mix 151.5 mg of methyl bromide, 500 mg of lead bromide and 1.1 mL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the first solution; mix 2.1 mg of zinc acetate and 265 μL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the second solution; mix the first solution and the second solution and continue stirring for 5 min to obtain the precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 4000 r / min for 30 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0051] Example 5; A zinc-doped perovskite downconversion thin film (1) ITO glass substrates were sequentially immersed in glass detergent, acetone and isopropanol solution for ultrasonic cleaning for 15 min, dried and then placed in ultraviolet ozone for 15 min.

[0052] (2) Mix 151.5 mg of methyl bromide, 500 mg of lead bromide and 1.1 mL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the first solution; mix 3.6 mg of zinc acetate and 454 μL of N,N-dimethylformamide evenly and stir at 25 °C for 2 h to obtain the second solution; mix the first solution and the second solution and continue stirring for 5 min to obtain the precursor solution; (3) Take a piece of ITO glass that has been cleaned and treated with ultraviolet ozone as a transparent substrate. Use a spin coater to drop the above precursor solution onto the non-ITO side of the ITO glass. First, spin coat at a speed of 4000 r / min for 30 s. After spin coating, let it dry naturally to prepare a zinc-doped perovskite downconversion film.

[0053] Example 6; A perovskite solar cell (1) A zinc-doped perovskite downconversion film was prepared on one side of an ITO glass substrate according to the method described in Example 2; (2) 1.5 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was added to 1 mL of chlorobenzene and spin-coated on the other side of the ITO glass substrate at a speed of 3000 r / min for 20 s. Then it was dried at 90 °C for 15 min to prepare the hole transport layer. (3) 650 mg lead iodide, 170 mg methyl iodide and 50 mg acrylamide were added to 503 μL of N,N-dimethylformamide and 23 μL of dimethyl sulfoxide mixed solvent and stirred thoroughly to obtain a perovskite precursor solution; then the perovskite solution was spin-coated at 3000 r / min for 20 s and annealed at 90 °C for 10 min to obtain a perovskite absorber layer; (4) Using the thermal evaporation method, C 25nm layers were deposited sequentially. 60 A hole-blocking layer was prepared, an electron transport layer was prepared by evaporating a 5 nm BCP (bath copper spirit), and an electrode was prepared by evaporating a 100 nm Ag layer, thus completing the fabrication of the perovskite solar cell.

[0054] Example 7; A perovskite solar cell (1) A zinc-doped perovskite downconversion film was prepared on one side of an ITO glass substrate according to the method described in Example 2; (2) 1.5 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was added to 1 mL of chlorobenzene and spin-coated on the other side of the ITO glass substrate at a speed of 4000 r / min for 30 s. Then it was dried at 100 °C for 10 min to prepare the hole transport layer. (3) 625 mg lead iodide, 160 mg methyl iodide and 50 mg acrylamide were added to 503 μL of N,N-dimethylformamide and 23 μL of dimethyl sulfoxide mixed solvent and stirred thoroughly to obtain a perovskite precursor solution; then the perovskite precursor solution was spin-coated at 4000 r / min for 20 s and annealed at 100 °C for 15 min to obtain a perovskite absorber layer; (4) Using the thermal evaporation method, C 25nm layers were deposited sequentially. 60 A hole-blocking layer was prepared, an electron transport layer was prepared by evaporating a 5 nm BCP (bath copper spirit), and an electrode was prepared by evaporating a 100 nm Ag layer, thus completing the fabrication of the perovskite solar cell.

[0055] Example 8; A perovskite solar cell (1) A zinc-doped perovskite downconversion film was prepared on one side of an ITO glass substrate according to the method described in Example 2; (2) 1.5 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was added to 1 mL of chlorobenzene and spin-coated on the other side of the ITO glass substrate at a speed of 4000 r / min for 30 s. Then it was dried at 110 °C for 10 min to prepare the hole transport layer. (3) 675 mg lead iodide, 180 mg methyl iodide and 50 mg acrylamide were added to 503 μL of N,N-dimethylformamide and 23 μL of dimethyl sulfoxide mixed solvent and stirred thoroughly to obtain a perovskite precursor solution; then the perovskite precursor solution was spin-coated at 5000 r / min for 20 s and annealed at 110 °C for 20 min to obtain a perovskite absorber layer; (4) Using the thermal evaporation method, C 25nm layers were deposited sequentially. 60 A hole-blocking layer was prepared, an electron transport layer was prepared by evaporating a 5 nm BCP (bath copper spirit), and an electrode was prepared by evaporating a 100 nm Ag layer, thus completing the fabrication of the perovskite solar cell.

[0056] Comparative Example 1 The only difference between Comparative Example 1 and Example 2 is step (2). Step (2) is modified as follows: 151.5 mg of methyl bromide, 500 mg of lead bromide and 1.1 mL of N,N-dimethylformamide are mixed evenly and stirred at 25°C for 2 h to obtain a precursor solution; the remaining steps are the same as in Example 2.

[0057] Comparative Example 2 The only difference between Comparative Example 1 and Example 7 is step (1). Step (1) is modified to: prepare a perovskite downconversion film on one side of the ITO glass substrate according to the method described in Comparative Example 1; the remaining steps are the same as in Example 7.

[0058] Comparative Example 3 like Figure 1 As shown in (b), the perovskite solar cell consists of the following layers stacked from bottom to top: an ITO glass substrate 1, a hole transport layer 2, a perovskite absorber layer 3, an electron transport layer 4, a hole blocking layer 5, and an electrode 6. The fabrication process is as follows: (1) 1.5 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was added to 1 mL of chlorobenzene and spin-coated on one side of an ITO glass substrate at a speed of 4000 r / min for 30 s. Then it was dried at 100 °C for 10 min to prepare a hole transport layer. (3) 625 mg lead iodide, 160 mg methyl iodide and 50 mg acrylamide were added to 503 μL of N,N-dimethylformamide and 23 μL of dimethyl sulfoxide mixed solvent and stirred thoroughly to obtain a perovskite precursor solution; then the perovskite precursor solution was spin-coated at 4000 r / min for 20 s and annealed at 100 °C for 15 min to obtain a perovskite absorber layer; (4) Using the thermal evaporation method, C 25nm layers were deposited sequentially. 60 A hole-blocking layer was prepared, an electron transport layer was prepared by evaporating a 5 nm BCP (bath copper spirit), and an electrode was prepared by evaporating a 100 nm Ag layer, thus completing the fabrication of the perovskite solar cell.

[0059] Test methods Photostability test: The zinc ion-doped perovskite downconversion film prepared in Example 2 and the undoped film prepared in Comparative Example 1 were placed in an environment with an intensity of 100 mW / cm². 2 The film was continuously irradiated under a 365nm ultraviolet lamp for 120 hours. After irradiation, the photoluminescence intensity retention rate of the film in Example 2 was 92.5%, while that of the film in Comparative Example 1 was only 65.3%, indicating that zinc ion doping significantly improved the photostability of the film itself.

[0060] Furthermore, the perovskite solar cell of Example 7, which integrates the thin film, was compared with the standard cell of Comparative Example 3 without a down-conversion layer. Under standard AM 1.5G simulated sunlight, after 200 hours of continuous operation at the maximum power point, the photoelectric conversion efficiency of Example 7 remained at 88.2%, while that of Comparative Example 3 remained at 72.1%. This demonstrates that the down-conversion thin film of the present invention can effectively delay the efficiency degradation of the integrated device.

[0061] Hydrophobicity test: The water contact angle of the film surface in Example 2 was 98.5°, while that of the film in Comparative Example 1 was 72.3°, indicating that zinc ion doping makes the film surface more hydrophobic and has better water vapor barrier ability.

[0062] Average transmittance test: According to the test method of GB / T46227-2025, using the same process parameters as each embodiment and comparative example, the film was prepared on an optical grade quartz glass substrate. The sample was placed in the sample optical path of the spectrophotometer, and a clean quartz glass slide of the same size was used as a reference. The transmission spectrum in the wavelength range of 300-850nm was measured at room temperature, and the integral average value of the spectral transmittance of the film in the wavelength range of 400nm to 800nm ​​was calculated as its average transmittance.

[0063] Photoluminescence efficiency test: According to the test method of GB / T44454, using the same process parameters as each embodiment and comparative example, the thin film was prepared on an optical-grade quartz glass substrate, the sample was fixed in the center of the integrating sphere, the laser was directly irradiated onto the sample, and all emission spectrum signals in the integrating sphere were collected. By accurately measuring and calculating the total number of excitation photons absorbed by the sample and the total number of photons emitted by the sample, the photoluminescence efficiency was automatically calculated. Photoluminescence efficiency = total number of photons emitted by the sample / total number of excitation photons absorbed by the sample. The specific data are shown in Table 1 below.

[0064] Table 1

[0065] As shown in Table 1, the photoluminescence efficiency of the film in Comparative Example 1 is only 32.5%, and the average transmittance is 81.7%. This indicates that zinc doping improves the photoluminescence efficiency and average transmittance of the downconversion film, and synergistically optimizes the overall optical performance of the downconversion film.

[0066] Figure 3 SEM images of the perovskite downconversion films of Example 2 and Comparative Example 1, wherein Figure 3 (a) is a SEM image of the perovskite downconversion film of Comparative Example 1. Figure 3 (b) is a SEM image of the perovskite downconversion film of Example 2. On the surface of the undoped zinc ion film, the perovskite nanocrystals are uneven in size and inconsistent in shape. However, on the surface of the zinc ion-doped film, the nanoparticles are uniform in size and regular in shape, and the grains are evenly dispersed. The film coverage is significantly improved, indicating that zinc ion doping has a significant promoting effect on the uniformity of downconversion film formation and surface coverage on the glass surface.

[0067] Depend on Figure 4It can be seen that after zinc ion doping, the intensity of the intrinsic emission peak (550nm) is significantly improved compared with the undoped condition, while the intensity of other impurity peaks (such as 700nm, 450nm, etc.) is significantly reduced, indicating that the introduction of zinc ions can effectively improve the monochromaticity and luminous efficiency of the thin film.

[0068] Table 2 shows a comparison of the efficiency of the perovskite solar cell devices in Examples 6-8 and Comparative Examples 2-3.

[0069] Table 2

[0070] Based on Table 2 Figure 5 It can be seen that, compared with batteries without a downconversion layer and those with a zinc-doped downconversion layer, devices with a zinc-doped downconversion layer have significantly improved short-circuit current density and conversion efficiency.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a zinc-doped perovskite downconversion thin film, characterized in that, Includes the following steps: (1) Provide a transparent substrate; (2) The perovskite precursor and N,N-dimethylformamide are mixed to prepare a first solution; the zinc salt additive and N,N-dimethylformamide are mixed to prepare a second solution, and the first solution and the second solution are mixed to obtain a precursor solution; (3) The precursor solution is coated on one surface of the transparent substrate and dried to form the zinc-doped perovskite downconversion film.

2. The method for preparing zinc-doped perovskite downconversion thin films according to claim 1, characterized in that, The zinc salt additive in step (2) is one of zinc acetate, zinc chloride, zinc nitrate, and zinc acetylacetonate.

3. The method for preparing zinc-doped perovskite downconversion thin films according to claim 1, characterized in that, The perovskite precursor in step (2) includes methylamine bromide and lead bromide.

4. The method for preparing zinc-doped perovskite downconversion thin films according to claim 2, characterized in that, In step (2), the mass ratio of methylamine bromide to lead bromide is 1:(3-4).

5. The method for preparing zinc-doped perovskite downconversion thin films according to claim 4, characterized in that, In step (2), the molar ratio of zinc ions in the second solution to lead ions in the first solution is (0.83~1.44%):

1.

6. The method for preparing zinc-doped perovskite downconversion thin films according to claim 1, characterized in that, In step (3), the coating is spin-coated, which is performed on the other side of the transparent substrate where no conductive layer has been formed.

7. The method for preparing zinc-doped perovskite downconversion thin films according to claim 6, characterized in that, The spin coating speed is 3000-5000 r / min, and the spin coating time is 20-40 s.

8. A zinc-doped perovskite downconversion thin film, characterized in that, It is obtained by the preparation method according to any one of claims 1 to 6.

9. A perovskite solar cell, characterized in that, The layers, arranged sequentially from bottom to top, include: the zinc-doped perovskite downconversion thin film as described in claim 8, a transparent substrate, a hole transport layer, a perovskite absorber layer, an electron transport layer, a hole blocking layer, and an electrode.

10. A method for preparing the perovskite solar cell of claim 9, characterized in that, Includes the following steps: (1) Provide a transparent substrate; (2) On one surface of the transparent substrate, a zinc-doped perovskite downconversion thin film as described in claim 8 is prepared; (3) On the other surface of the transparent substrate, a hole transport layer, a perovskite absorber layer, an electron transport layer and an electrode are prepared in sequence to finally complete the preparation of the perovskite solar cell.

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