A polyimide resin solution, its preparation method, and its application in perovskite solar cells.

Abstract

This invention discloses a polyimide resin solution, its preparation method, and its application in perovskite solar cells. The polyimide resin solution is prepared by mixing a mixture of fluorinated aromatic diamines and rigid aromatic diamines, and a mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides as raw materials. In the mixture of fluorinated aromatic diamines and rigid aromatic diamines, the molar ratio of the fluorinated aromatic diamines to the rigid aromatic diamines is 10–50:90–50; in the mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides, the molar ratio of the fluorinated aromatic tetracarboxylic dianhydrides to the rigid aromatic tetracarboxylic dianhydrides is 100–80:0–20. A polyimide resin solution is coated onto the back surface of a perovskite solar cell device to form a coating with a cutoff transmission wavelength of 380–420 nm and a transmittance of over 80% in the visible light band of 450 nm and above. This coating not only provides resistance to ultraviolet radiation but also facilitates the conversion of solar energy into electrical energy, thus balancing the high efficiency and stability of the battery. Furthermore, the manufacturing process is simple and efficient.

Description

Technical Field

[0001] This invention belongs to the field of polymer thin films and solar cells, and more specifically, relates to a polyimide resin solution, its preparation method, and its application in perovskite solar cells. Background Technology

[0002] In recent years, perovskite solar cells have become a hot research topic in the fields of energy, optoelectronic semiconductors, and other areas. The rapid development of their device performance has attracted widespread attention from researchers. The unique material properties of perovskite, such as low exciton binding energy, high absorption coefficient, long carrier diffusion length, high defect tolerance, and tunable bandgap, make it an excellent active material for photovoltaic devices. Optimization of device structure and fabrication processes, such as perovskite composition adjustment, interface engineering, and functional layer modification, have provided strong support for the rapid development of perovskite solar cells. Photovoltaic efficiency, cost, and stability are the three gold standards for evaluating solar cells. With continuous optimization by researchers, the efficiency and fabrication cost of perovskite solar cells have basically met commercialization requirements. However, their operational instability remains a major factor restricting the further development and commercialization of perovskite solar cells.

[0003] The instability of perovskites stems from two main sources: their inherent defects and the resulting ion migration, as well as the destructive effects of external factors such as water, oxygen, heat, and high-energy ultraviolet light. While perovskite defects can be effectively passivated and external water and oxygen isolated through techniques like perovskite composition adjustment, additive engineering, interface modification, and encapsulation, thus improving device performance and stability, most research employs high-transmittance designs to ensure the light absorption intensity and light utilization rate of the active material. This inevitably leads to the destructive effects of high-energy ultraviolet light on solar cell materials. Furthermore, in practical applications, solar cells are exposed to sunlight for extended periods, making the destructive effects of ultraviolet light on device performance and stability even more pronounced.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a polyimide resin solution, its preparation method, and its application in perovskite solar cells. The polyimide resin solution is directly coated onto the back surface of the perovskite solar cell device to form a spectral modification layer. The prepared perovskite solar cell device exhibits high photocurrent while significantly overcoming the degradation of active materials and performance decline caused by prolonged exposure to strong ultraviolet light, thus balancing high efficiency and stability in battery operation.

[0006] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a polyimide resin solution, which is obtained by mixing a mixture of fluorinated aromatic diamine and rigid aromatic diamine, and a mixture of fluorinated aromatic tetracarboxylic dianhydride and rigid aromatic tetracarboxylic dianhydride as raw materials. In a mixture of fluorinated aromatic diamines and rigid aromatic diamines, the molar ratio of fluorinated aromatic diamines to rigid aromatic diamines is 10~50 : 90~50; in a mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides, the molar ratio of fluorinated aromatic tetracarboxylic dianhydrides to rigid aromatic tetracarboxylic dianhydrides is 100~80 : 0~20.

[0007] In the polyimide resin solution of the present invention, fluorinated aromatic diamines and fluorinated aromatic dianhydrides can reduce the polarity of the resin backbone structure and weaken the charge transfer effect between molecules, which helps to improve the light transmittance of the polyimide resin and the formed film layer. Rigid aromatic diamines and rigid aromatic dianhydrides help to control the cutoff light transmittance wavelength of the polyimide resin solution and the formed film layer and improve the glass transition temperature and mechanical strength of the polyimide film.

[0008] The inventors discovered that by controlling the proportions of each component in a mixture of fluorinated aromatic diamines and rigid aromatic diamines, and a mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides, within the aforementioned ranges, the cutoff wavelength and visible light transmittance can be controlled. The resulting coating or film has a cutoff wavelength of 380-420 nm and a visible light transmittance exceeding 80% at 450 nm and above. Polyimide resin solutions are used in perovskite solar cell devices, coating the back side to form a coating. On one hand, this blocks high-energy ultraviolet light from entering the semiconductor layer, preventing UV damage to the device and thus improving the stability and lifespan of the battery. On the other hand, it also has high visible light transmittance, facilitating the full conversion of solar energy into electrical energy; thus, both high efficiency and stability of the battery operation can be achieved.

[0009] In a further embodiment, the molar ratio of the fluorinated aromatic diamine to the rigid aromatic diamine in the mixture is 20-40: 80-60; and the molar ratio of the fluorinated aromatic tetracarboxylic dianhydride to the rigid aromatic tetracarboxylic dianhydride in the mixture is 95-85: 5-15.

[0010] In a further embodiment, the fluorinated aromatic diamine is selected from at least one of 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 1,3-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 4,4'-bis(2-trifluoromethyl-4-aminophenoxy)biphenyl, 2,2'-bistrifluoromethyl-4,4'-diaminobiphenyl, 3,3'-bistrifluoromethyl-5,5'-diaminobiphenyl, 2,2-bis(4-aminophenoxybenzene)hexafluoropropane, 3-trifluoromethyl-m-phenylenediamine, tetrafluoro-p-phenylenediamine, tetrafluoro-m-phenylenediamine, 4,4'-octafluorobiphenylenediamine, or 4,4'-diaminooctafluorobiphenyl ether. The rigid aromatic diamine is selected from at least one of 1,4-p-phenylenediamine, 1,3-m-phenylenediamine, 4,4'-biphenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, or 2,2',3,3'-tetramethyl-4,4'-diaminobiphenyl.

[0011] In a further embodiment, the fluorinated aromatic tetracarboxylic dianhydride is selected from at least one of 4,4'-(hexafluoroisopropyl)diphthalic anhydride, 4,4'-(trifluoromethylphenylisopropyl)diphthalic anhydride, 4,4'-(trifluoromethyl-m-bis(trifluoromethylphenyl-isopropyl)diphthalic anhydride, and 4,4'-(trifluoromethyl-m,m-bis(trifluoromethylphenyl-isopropyl)diphthalic anhydride); The rigid aromatic tetracarboxylic dianhydride is selected from at least one of pyromellitic dianhydride, 4,4'-biphenyl ether dianhydride, bisphenol A type diether dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,-3',4'-biphenyltetracarboxylic acid dianhydride, or 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride.

[0012] In a further embodiment, the polyimide resin solution has a solute content of 5-30%, preferably 15-25%; the viscosity of the polyimide resin solution is 1×10⁻⁶. 4 cP~5×10 5 cP, preferably 5×10 4 cP ~ 2×10 5 cP.

[0013] The second objective of this invention is to provide a method for preparing a polyimide resin solution as described in any of the above schemes or combinations thereof, comprising: adding a mixture of rigid aromatic diamine and fluorinated aromatic diamine solid powder to an organic solvent to obtain a homogeneous solution, then adding a mixture of rigid aromatic tetracarboxylic dianhydride and fluorinated aromatic tetracarboxylic dianhydride solid powder in batches, stirring until a homogeneous solution is formed, and continuing to stir to obtain a polyimide resin solution; Preferably, the organic solvent is selected from at least one of N-methylpyrrolidone, N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, ethyl lactate, cyclopentanone, cyclohexanone, methyl ethyl ketone, dioxane, ethyl acetate, or butyl acetate.

[0014] A third objective of this invention is to provide a polyimide film obtained by imidizing and post-processing a polyimide resin solution as described in any of the above embodiments or combinations thereof. Preferably, the polyimide resin solution described in any of the above schemes or combinations is degassed under vacuum, an imidizing agent is added, and after being mixed evenly, it is coated and heated to form a semi-cured film; the semi-cured film is peeled off, and its perimeter is fixed or subjected to high temperature treatment under biaxial stretching to complete the imidization reaction and then cooled to obtain a colorless and transparent polyimide film.

[0015] A fourth objective of this invention is to provide an application of the polyimide resin solution or polyimide film as described in any of the above embodiments or combinations thereof in the fabrication of perovskite solar cell devices.

[0016] The fifth objective of this invention is to provide a perovskite solar cell device, wherein the back surface of the perovskite solar cell device has a spectral modification layer formed by coating with a polyimide resin solution as described above or any combination thereof.

[0017] A further embodiment involves using a spin coating method to coat the polyimide resin solution described above or any combination thereof onto the back surface of the perovskite solar cell device. The spin coating speed of the polyimide resin solution is 500 rpm to 5000 rpm, preferably 1500 rpm to 2500 rpm; the thickness of the polyimide film layer is 5 μm to 25 μm, preferably 10 μm to 15 μm.

[0018] A further approach involves coating the back surface of the perovskite solar cell device with a polyimide resin solution and then annealing it; the annealing temperature is 320℃-50℃, and the annealing time is 2.5-1.5 hours.

[0019] A further proposed approach is to use a spectral modification layer with a cutoff transmission wavelength of 380-420 nm and a transmittance of over 80% in the visible light band at 450 nm and above.

[0020] In a further embodiment, the electron transport layer of the perovskite solar cell device is prepared by SnO2 aqueous dispersion system, the perovskite active layer of the perovskite solar cell is prepared by a two-step spin coating method, the hole transport layer of the perovskite solar cell is prepared by Li salt doped Spiro-OMeTAD, and the metal electrode (gold electrode) of the perovskite solar cell is prepared by high vacuum thermal evaporation deposition.

[0021] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. The polyimide resin solution provided by this invention, by adjusting the composition and content of each component, and controlling the solute content and viscosity, can be prepared into a thin film through imidization and post-treatment, or directly into a coating. Compared with thin films that need to be adhered to perovskite solar cell devices using adhesives, the polyimide resin solution of this invention has suitable solute content and viscosity, meeting the conditions for coating. Therefore, it can be directly coated onto the back surface of perovskite solar cell devices to form a spectral modification layer. The preparation process is simple, convenient, and efficient, and can also save manpower and resources.

[0022] 2. The perovskite solar cell device of the present invention has a polyimide thin film back surface spectral modification layer, which is obtained by spin-coating a polyimide resin solution onto the back surface of the perovskite solar cell device followed by annealing. The polyimide resin solution is used in the perovskite solar cell device to form a coating, i.e., a spectral modification layer, on its back surface. The cutoff transmission wavelength is 380-420 nm, and the transmittance in the visible light band at 450 nm and above exceeds 80%. On the one hand, it can block high-energy ultraviolet light from entering the semiconductor layer, avoiding damage to the device from ultraviolet rays, thereby improving the stability and lifespan of the battery. On the other hand, it also has high visible light transmittance, which is beneficial for fully converting solar energy into electrical energy. Therefore, the perovskite solar cell device of the present invention has a high photocurrent while significantly overcoming the degradation of active materials and the decline in device performance caused by prolonged exposure to strong ultraviolet light, thus balancing high efficiency and stability in battery operation.

[0023] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 a is the light absorption and fluorescence spectrum of the polyimide film in Example 1; Figure 1 b is a comparison spectrum of the transmittance of the ITO / polyimide film substrate in Example 1 and the ITO substrate in Comparative Example 1; Figure 2 a is a schematic diagram of the perovskite solar cell device structure with polyimide thin film back surface modification layer in Example 1; Figure 2 b is a schematic diagram of the perovskite solar cell device in Comparative Example 1; Figure 3 a represents the UV stability test of the device in Comparative Example 1 and the device with the polyimide back modification layer in Example 1; Figure 3 b represents the JV test curves of the device in Comparative Example 1 and the device with the polyimide back modification layer in Example 1; Figure 4 The XRD patterns of the perovskite active layer of the device with the polyimide back modification layer in the examples and the comparative device before and after illumination are shown.

[0025] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0027] It should be noted that, unless otherwise specified, all reagents used in the embodiments of this invention are commercially available.

[0028] Detection method: Viscosity: The viscosity was measured using an AMETEK Brookfield MRVT115 viscometer. The resin was dropped into the test chamber and the final reading was taken after 10 minutes. The test temperature was 25℃.

[0029] Solid content: The solid content is calculated based on the amount of solids (W1) and solvent (W2) added during the synthesis of the resin: W1 / (W1+W2)×100%.

[0030] Cutoff wavelength: The cutoff wavelength was determined using a Hitachi U3900 spectrophotometer with a test range of 180~800nm ​​and a sample thickness of 25μm. The wavelength at the intersection of the tangents of the opaque region and the region where light begins to pass through was taken as the cutoff wavelength.

[0031] Example 1

[0032] 1. Preparation of polyimide resin solution: In a 500ml three-necked round-bottom flask equipped with a mechanical stirrer, thermometer, and nitrogen protection device, add 200ml of N-methylpyrrolidone, 96.1g (0.3mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 140.0g (0.7mol) of 4,4'-diaminodiphenyl ether. Under stirring and nitrogen protection, dissolve all the solids to form a homogeneous solution. Cool the round-bottom flask to 0-5ºC in an ice bath. While stirring, add 399.6g (0.9mol) of 4,4'-(hexafluoroisopropyl)diphthalic anhydride and 29.4g (0.1mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride solid powder in batches to the above homogeneous solution. After the solid is completely dissolved, the reaction is continued for 24 hours to obtain a viscous homogeneous polyimide film-specific resin solution with a viscosity of 60,000 cP and a solid content of 23.5%.

[0033] 2. Preparation of polyimide film and testing of film performance: Take 100g of the above-mentioned polyimide film-specific resin and put it into a 200ml glass flask. Add 20g of a mixture of acetic anhydride and pyridine (2 / 1 molar ratio) under stirring, mix evenly, filter under pressure, and degas under vacuum. Coat the resin solution onto the surface of a glass plate and heat-treat (60ºC / 1h + 120ºC / 10min). Peel off the formed semi-cured film from the surface of the glass plate. Then, fix the perimeter of the semi-cured film on a stainless steel frame or treat it at high temperature at 250-350ºC / 1h under biaxial stretching conditions. After cooling, a transparent polyimide film (25µm) is obtained with a transmittance of 85.6% at 450nm.

[0034] 3. Fabrication of perovskite solar cells: SnO2 dilution solution: The SnO2 (15% aqueous colloidal dispersion) dispersion was diluted with ultrapure water at a ratio of 6.5:1.2. After ultrasonic treatment for 30 min, it was filtered with a 0.45 μm filter and then used for later use.

[0035] Preparation of PbI2 precursor solution: 760 mg PbI2 and 18.2 mg CsI were added to a mixed solvent of 1 mL DMF and 160 μL DMSO, stirred at 60 °C for 12 h, and filtered through a 0.22 μm polytetrafluoroethylene filter before use.

[0036] Preparation of mixed ammonium salt solution: Dissolve 11.5 mg MACl, 11 mg MABr and 110 mg FAI in 1.5 mL isopropanol, filter with a 0.22 μm polytetrafluoroethylene filter and set aside.

[0037] Preparation of Spiro-OMeTAD solution: Add 72.3 mg Spiro-OMeTAD, 35 μL Li-TFSI acetonitrile solution (260 mg / mL) and 28.8 μL 4-tert-butylpyridine (TBP) to 1 mL of chlorobenzene to prepare Spiro-OMeTAD solution. Filter the solution through a 0.22 μm polytetrafluoroethylene filter and set aside for later use.

[0038] Method: (1) At room temperature (around 22 °C), drop the above appropriate amount of polyimide resin onto the back of the ITO glass substrate and spin coat it at 2000 rpm for 60 s. Then transfer it to a hot plate and gradually heat it from room temperature to 300 °C. After curing for 2 h, remove it.

[0039] (2) Wipe the substrate with the surface modification layer with acetone and dry it with a nitrogen gun. Place it in an oxygen plasma cleaner, evacuate for 2 minutes, pass oxygen for 5 minutes, and then treat the ITO surface with oxygen plasma for 5 minutes.

[0040] (3) The SnO2 dilution solution was dropped onto the ITO substrate and spin-coated at 3000 rpm for 35 s. Then it was transferred to a hot plate at 150℃ and annealed for 30 min (air humidity was 40%) to obtain the SnO2 layer.

[0041] (4) After SnO2 annealing, transfer it to a nitrogen glove box, drop PbI2 precursor liquid onto SnO2 / ITO substrate, spin coat at 1600 rpm for 20 s and then spin coat at 4000 rpm for 30 s, then transfer it to a 70℃ hot stage for annealing for 2 min.

[0042] (5) Add 120 μL of mixed ammonium salt solution to the rotating lead iodide at a speed of 2000 rpm for 23 s, and then transfer it to air (relative humidity of 40%) and anneal it on a hot plate at 140℃ for 20 min.

[0043] (6) After the perovskite annealing is completed, it is transferred to a glove box, and 120 μL of isopropanol is added dropwise to the rotating perovskite surface to clean the residual mixed ammonium salts on the perovskite surface. The rotation speed is 4000 rpm and the time is 30 s.

[0044] (7) The hole transport layer Spiro-OMeTAD solution was spin-coated onto the perovskite surface at 4000 rpm for 30 s, and the prepared wafer was placed in a desiccator and stored for 24 h. (8) The sample was placed in a vacuum coating machine and evacuated to a vacuum level of 2.5 × 10⁻⁶. -4 Pa, at 0.3 Å s -1 A gold electrode with a thickness of 80 nm was deposited at a high speed.

[0045] like Figure 1 As shown in b, compared with Comparative Example 1, the polyimide coating / ITO substrate prepared by this invention exhibits strong light absorption in the ultraviolet light band <380 nm, while exhibiting high light transmittance in the visible light band >380 nm. This optical performance is a prerequisite for ensuring the light absorption of the device and significantly improving its ultraviolet stability.

[0046] Example 2-3

[0047] The methods for preparing polyimide resin solutions and perovskite solar cells in Examples 2-3 are the same as those in Example 1, with the differences shown in Table 1.

[0048] Table 1. Preparation methods of polyimide resin solutions in Examples 1-3

[0049] The performance test results of the perovskite solar cells prepared in Examples 1-3 are shown in Table 3 below.

[0050] Comparative Example 1: Perovskite solar cell device without polyimide back surface modification

[0051] Fabrication of perovskite solar cell devices: SnO2 dilution solution: The SnO2 (15% aqueous colloidal dispersion) dispersion was diluted with ultrapure water at a ratio of 6.5:1.2. After ultrasonic treatment for 30 min, it was filtered with a 0.45 μm filter and then used for later use.

[0052] Preparation of PbI2 precursor solution: 760 mg PbI2 and 18.2 mg CsI were added to a mixed solvent of 1 mL DMF and 160 μL DMSO, stirred at 60 °C for 12 h, and filtered through a 0.22 μm polytetrafluoroethylene filter before use.

[0053] Preparation of mixed ammonium salt solution: Dissolve 11.5 mg MACl, 11 mg MABr and 110 mg FAI in 1.5 mL isopropanol, filter with a 0.22 μm polytetrafluoroethylene filter and set aside.

[0054] Preparation of Spiro-OMeTAD solution: Add 72.3 mg Spiro-OMeTAD, 35 μL Li-TFSI acetonitrile solution (260 mg / mL) and 28.8 μL 4-tert-butylpyridine (TBP) to 1 mL of chlorobenzene to prepare Spiro-OMeTAD solution. Filter the solution through a 0.22 μm polytetrafluoroethylene filter and set aside for later use.

[0055] Method: (1) Wipe the ITO glass substrate with acetone and dry it with a nitrogen gun. Place it in an oxygen plasma cleaner, evacuate for 2 minutes, pass oxygen for 5 minutes, and then treat the ITO surface with oxygen plasma for 5 minutes.

[0056] (2) The SnO2 dilution solution was dropped onto the ITO substrate and spin-coated at 3000 rpm for 35 s. Then it was transferred to a hot plate at 150℃ and annealed for 30 min (air humidity was 40%) to obtain the SnO2 layer.

[0057] (3) After SnO2 annealing, transfer it to a nitrogen glove box, drop PbI2 precursor liquid onto SnO2 / ITO substrate, spin coat at 1600 rpm for 20 s and then spin coat at 4000 rpm for 30 s, then transfer it to a 70℃ hot stage for annealing for 2 min.

[0058] (4) Add 120 μL of mixed ammonium salt solution to the rotating lead iodide at a speed of 2000 rpm for 23 s, and then transfer it to air (relative humidity of 40%) and anneal it on a hot plate at 140℃ for 20 min.

[0059] (5) After the perovskite annealing is completed, it is transferred to a glove box, and 120 μL of isopropanol is added dropwise to the rotating perovskite surface to clean the residual mixed ammonium salts on the perovskite surface. The rotation speed is 4000 rpm and the time is 30 s.

[0060] (6) The hole transport layer Spiro-OMeTAD solution was spin-coated on the perovskite surface at a speed of 4000 rpm for 30 s, and the prepared film was placed in a desiccator and stored for 24 h.

[0061] (7) Place the sample in a vacuum coating machine and evacuate it to a vacuum level of 2.5 × 10⁻⁶. -4 Pa, at 0.3 Å s -1 The speed of vapor deposition is used to deposit an 80nm thick gold electrode.

[0062] Analysis of the comparison results between Example 1 and Comparative Example 1: like Figure 1 As shown in Figure a, the polyimide film prepared in Example 1 exhibits significant fluorescence emission at a wavelength of 460 nm, which can compensate for the light absorption of the perovskite and reduce the optical loss caused by surface modification.

[0063] like Figure 2 Figures a and 2b show schematic diagrams of the perovskite solar cell device (b) of Comparative Example 1 and the polyimide back surface modified perovskite solar cell device (a) of Example 1.

[0064] like Figure 3As shown in a and 3b, the perovskite solar cell with polyimide back-modified layer obtained in Example 1 of this invention achieved a significant improvement in ultraviolet stability with only a slight loss of 6.54% in initial photoelectric conversion efficiency, at a power of 150 mW / cm². -2 Even after 8 hours of enhanced ultraviolet light (365 nm) irradiation, it still retains more than 85% of its initial efficiency. Figure 3 The reference device (Comparative Example 1) without a polyimide back modification layer showed an efficiency degradation to 40.9% of its initial value under the same UV test. Figure 3 (without PI).

[0065] like Figure 4 As shown in Embodiment 1 of the present invention, the perovskite active layer with a polyimide backing modification layer is used at a power of 150 mW / cm². -2 After 6 hours of enhanced ultraviolet light (wavelength 365 nm) irradiation, no significant degradation was observed in its active layer. Figure 4 The reference device (Comparative Example 1) without a polyimide backing layer showed degradation of the perovskite component after the same UV irradiation, producing a large amount of lead iodide, which significantly damaged the device's performance and stability. Figure 4 (without PI).

[0066] Comparative Examples 2-3

[0067] The preparation methods of the polyimide resin solutions of Comparative Examples 2-3 are the same as those in Example 1, with the differences shown in Table 2.

[0068] Table 2

[0069] Test case

[0070] The performance of the perovskite solar cells prepared in Examples 1-3 and Comparative Examples 1-3 was tested using the following methods: Open-circuit voltage, short-circuit current, fill factor, initial efficiency, and normalized efficiency after UV testing were measured using a Keithley 2400-based solar cell IV testing system. Light intensity was calibrated to 100 mW / cm² for monocrystalline silicon cells. The test methods included: all current density-voltage (JV) curves and corresponding open-circuit voltage, short-circuit current, fill factor, and cell photoelectric conversion efficiency. 2 The effective area of ​​the device is 0.04 cm². 2 .

[0071] The test parameters were set as follows: scan speed of 200 mV / s, scan range of -0.2 V to 1.2 V, number of collection points of 140, and dwell time of 30 ms. The normalized efficiency after UV aging test is the ratio of the efficiency measured after UV aging to the initial efficiency of the device, i.e., PCE(UV-aging) / PCE(initial).

[0072] The performance test results of the perovskite solar cells prepared in Comparative Examples 1-3 are shown in Table 3 below.

[0073] Table 3

[0074] Results analysis: Compared to Comparative Examples 1-3, Examples 1-3 balanced the initial photovoltaic performance and UV stability of the battery, achieving excellent UV resistance with only a slight loss in initial device performance, greatly improving the device's lifespan and stability during actual use. In the three comparative examples, Comparative Example 1, without a PI film, showed significant UV degradation; Comparative Example 2, using PI with an excessively small cutoff wavelength, failed to achieve effective UV resistance; and Comparative Example 3, using PI with an excessively large cutoff wavelength, resulted in a significant loss of initial device performance.

[0075] Combination Figure 3 , Figure 4 As can be seen from the test results in Table 3, the solution of the present invention can greatly reduce the damage and degradation of materials by ultraviolet light while ensuring the efficiency and photocurrent of perovskite solar cells, and can significantly improve the working stability of the device, meeting the needs of long-term use in daily production and life.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polyimide resin solution, characterized in that, A polyimide resin solution was obtained by mixing a mixture of fluorinated aromatic diamines and rigid aromatic diamines, and a mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides as raw materials. In a mixture of fluorinated aromatic diamines and rigid aromatic diamines, the molar ratio of fluorinated aromatic diamines to rigid aromatic diamines is 10~50 : 90~50; in a mixture of fluorinated aromatic tetracarboxylic dianhydrides and rigid aromatic tetracarboxylic dianhydrides, the molar ratio of fluorinated aromatic tetracarboxylic dianhydrides to rigid aromatic tetracarboxylic dianhydrides is 90-80 : 10-20. The fluorinated aromatic diamine is selected from at least one of 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 2,2'-bistrifluoromethyl-4,4'-diaminobiphenyl, and 2,2-bis(4-aminophenoxybenzene)hexafluoropropane; The rigid aromatic diamine is selected from at least one of 1,4-p-phenylenediamine, 1,3-m-phenylenediamine, and 4,4'-diaminodiphenyl ether; The fluorinated aromatic tetracarboxylic dianhydride is selected from at least one of 4,4'-(hexafluoroisopropyl)diphthalic anhydride and 4,4'-(trifluoromethyl-m-bis(trifluoromethyl)phenyl-isopropyl)diphthalic anhydride; The rigid aromatic tetracarboxylic dianhydride is selected from at least one of 4,4'-biphenyl ether dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride; The coating or film formed by the polyimide resin solution has a cutoff transmission wavelength of 380~420nm, and a transmittance of more than 80% in the visible light band of 450nm and above.

2. The polyimide resin solution according to claim 1, characterized in that, The polyimide resin solution has a solute content of 5-30% and a viscosity of 1×10⁻⁶. 4 cP~5×10 5 cP.

3. The polyimide resin solution according to claim 2, characterized in that, The polyimide resin solution has a solute-solid content of 15-25%.

4. The polyimide resin solution according to claim 2, characterized in that, The viscosity of the polyimide resin solution is 5 × 10⁻⁶. 4 cP ~ 2×10 5 cP.

5. A method for preparing a polyimide resin solution as described in any one of claims 1-4, characterized in that, include: A mixture of rigid aromatic diamine and fluorinated aromatic diamine solid powder is added to an organic solvent to obtain a homogeneous solution. Then, a mixture of rigid aromatic tetracarboxylic dianhydride and fluorinated aromatic tetracarboxylic dianhydride solid powder is added in batches and stirred until a homogeneous solution is formed. Stirring is continued to obtain a polyimide resin solution. The organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, ethyl lactate, cyclopentanone, cyclohexanone, methyl ethyl ketone, dioxane, ethyl acetate, or butyl acetate.

6. A polyimide film, characterized in that, The polyimide resin solution according to any one of claims 1-4 is obtained by imidization and post-treatment.

7. The polyimide film according to claim 6, characterized in that, The polyimide resin solution is degassed under vacuum, an imidizing agent is added, and the mixture is mixed evenly. The mixture is then coated and heated to form a semi-cured film. The semi-cured film is peeled off, and its edges are fixed or subjected to high temperature treatment under biaxial stretching to complete the imidization reaction. After cooling, a colorless and transparent polyimide film is obtained.

8. The use of a polyimide resin solution as described in any one of claims 1-4 or a polyimide film as described in claim 6 or 7 in the fabrication of perovskite solar cell devices.

9. A perovskite solar cell device, characterized in that, The back surface of the perovskite solar cell device has a spectral modification layer formed by coating with a polyimide resin solution as described in any one of claims 1-4.

10. The perovskite solar cell device according to claim 9, characterized in that, The polyimide resin solution described in any one of claims 1-4 is coated onto the back surface of a perovskite solar cell device using a spin coating method. The spin coating speed of the polyimide resin solution is 500 rpm to 5000 rpm, and the thickness of the polyimide film layer is 5 μm to 25 μm.

11. The perovskite solar cell device according to claim 10, characterized in that, The spin-coating speed for the polyimide resin solution is 1500 rpm to 2500 rpm.

12. The perovskite solar cell device according to claim 10, characterized in that, The thickness of the polyimide film is 10 μm-15 μm.

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