Application of polyimide film in preparation of perovskite solar cell

Abstract

The invention relates to application of a polyimide film in preparation of a perovskite solar cell. The thermal expansion coefficient of the polyimide film is slightly different from that of ITO or IZO, the matching degree is good in the subsequent heating process, the material flatness is high, and subsequent processing is facilitated. Furthermore, the polyimide film is good in transparency and resistant to high temperature, so that the polyimide film is particularly suitable for preparing a flexible conductive substrate of a perovskite solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible polymer thin film materials, and particularly to the application of an ultra-low coefficient of thermal expansion transparent flexible polyimide film in the preparation of a flexible conductive substrate for perovskite solar cells. Background Art

[0002] Flexible perovskite solar cells (f-PSC) have the advantages of high flexibility, light weight, good portability, and compatibility with irregular electronic products. Therefore, they have shown great potential in wearable power sources and integration with architectures. As an important functional material, transparent conductive materials have been widely used in many fields. Transparent conductive materials prepared on glass have reached a relatively high level of preparation and application. Transparent conductive materials such as ITO, AZO, and sandwich structures (oxide / metal / oxide, OMO) prepared on ordinary organic flexible conductive substrates (PEN, PET, etc.) have good electrical conductivity and light transmittance. However, organic flexible substrates have insurmountable defects: they are not resistant to high temperatures, the bonding force between the substrate and the material is poor, and there is a large difference in the linear coefficient of thermal expansion between the substrate and the conductive layer. Therefore, there is an urgent need in technology to develop a new type of flexible conductive substrate material with high temperature resistance, low coefficient of thermal expansion, small surface roughness, and high transparency. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides the use of a polyimide film in the preparation of a flexible conductive substrate for perovskite solar cells. The polyimide is a polymer of a dianhydride monomer and a diamine monomer. The dianhydride monomer is selected from 4,4'-biphenyl dianhydride (ODPA) or hexafluorodiacid dianhydride (6FDA), and the diamine monomer is selected from 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB).

[0004] According to an embodiment of the present invention, the weight average molecular weight Mw of the polyimide is 100,000 or more.

[0005] According to an embodiment of the present invention, the polyimide film is prepared by the following method:

[0006] The dianhydride monomer ODPA or 6FDA and the diamine monomer 6FAPB are subjected to a stepwise temperature increase reaction in DMAc at 60°C / 10h; 80°C / 10h; 200°C / 3h; 250°C / 2h:

[0007]

[0008] Wherein, the molar ratio of the dianhydride monomer to the diamine monomer is 1:1;

[0009] n is an integer of 200 or more.

[0010] According to an embodiment of the present invention, the polyimide film is prepared by the following method:

[0011] (1) Under a nitrogen atmosphere, one of ODPA or 6FDA and 6FAPB is stirred and dissolved in DMAc solution in an ice bath until the raw materials are completely dissolved in the DMAc solution, and stirring is continued for 1 to 24 hours until the solution becomes clear and viscous;

[0012] (2) The solution is slowly poured onto a glass plate, and a flat wet film is obtained using a doctor blade coater. Thermal imidization is carried out on it by stepwise heating: 60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h to obtain a polyimide film, which is peeled off from the glass plate using deionized water and dried in an oven.

[0013] The present invention also provides a flexible conductive substrate for a perovskite solar cell, which comprises the polyimide film as described above and an ITO or IZO sputtering layer on the surface of the film.

[0014] According to an embodiment of the present invention, the magnetron sputtering device used is the Shenkeyi TRP450-B type magnetron sputtering system.

[0015] According to an embodiment of the present invention, the thickness of the transparent conductive layer ITO or IZO on the flexible conductive substrate of the perovskite solar cell is 100 - 400 nm, for example, 200 - 300 nm.

[0016] According to an embodiment of the present invention, the light transmittance of the flexible conductive substrate in the perovskite solar cell is more than 80%, for example, more than 85%.

[0017] The present invention also provides a method for preparing a flexible conductive substrate for a perovskite solar cell using the polyimide film as described above, which includes: sputtering ITO or IZO onto the polyimide film as described above.

[0018] According to an embodiment of the present invention, the following steps are adopted to prepare the flexible conductive substrate of the solar cell:

[0019] a. Install the target ITO or IZO in the RF cathode target slot of the magnetron sputtering device, place the polyimide film as described above in the substrate holder, insert the substrate holder into the substrate tray in the sputtering chamber, and adjust the distance between the target and the substrate to 90 - 130 mm;

[0020] b. Pump the sputtering chamber to make the vacuum degree of the sputtering chamber 1.0×10 -4Below Pa, argon gas is filled into the sputtering chamber, and the pumping volume is adjusted to make the gas pressure in the sputtering chamber 0.1 - 6 Pa; the RF power supply of the target is turned on, and the power is 30 - 60 w. After pre-sputtering for a period of time, the baffle is opened, and the transparent conductive layer ITO or IZO is sputter-deposited on the surface of the polyimide film to obtain a flexible conductive substrate.

[0021] The present invention also provides a perovskite solar cell, which includes the flexible conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode as described above. The flexible conductive substrate, the electron transport layer, the perovskite layer, the hole transport layer, and the metal electrode are arranged in sequence;

[0022] Among them, the electron transport layer is deposited on one side of the PI film with ITO or IZO.

[0023] The present invention also provides a preparation method of the perovskite solar cell as described above, including the following steps: etching and cleaning the flexible conductive substrate, preparing a precursor solution, sequentially depositing an electron transport layer, a perovskite layer, and a hole transport layer on the flexible conductive substrate, and evaporating and depositing a metal electrode.

[0024] According to the embodiment of the present invention, the etching and cleaning of the flexible conductive substrate include: rubbing the surface of the conductive polyimide film with dishwashing liquid to remove dust and impurities, etc., and placing it on the cleaning rack; after cleaning, putting it into a large beaker, adding plasma water to cover the wafer, covering the cup mouth with tin foil, ultrasonically vibrating for 15 min, then ultrasonically vibrating with ethanol for 15 min, then putting it into an oven at 70 °C to dry the solvent, taking it out and sticking a 6 mm high-temperature tape at the cathode;

[0025] According to the embodiment of the present invention, the preparation of the precursor solution includes:

[0026] a1. Prepare SnO 2 Precursor solution

[0027] Weigh the commercial tin oxide colloid precursor solution and deionized water according to the mass ratio of 1:3, mix and dilute them, and stir for later use;

[0028] b1. Prepare the perovskite precursor solution

[0029] The whole process of preparing the perovskite precursor solution needs to be carried out in a nitrogen glove box, and all the drugs and solvents used need to be anhydrous reagents to ensure the usability of the perovskite precursor solution; the perovskite precursors to be weighed include 1.53 M lead iodide (PbI 2 ), 0.11 M lead bromide (PbBr 2) 1.4 M formamidinium hydroiodide (FAI), 0.11 M methylammonium hydrobromide (MABr), 0.5 M methylammonium chloride (MACl); After weighing the above-mentioned drugs according to the concentration of the prepared solution, add a mixed solvent of DMF and DMSO with a volume ratio of 9:1, stir until completely dissolved, and then add 45 μL of a CsI (DMSO) solution with a concentration of 1.5 mmol / ml, and continue to stir for 12 to 24 h to obtain a usable perovskite precursor solution;

[0030] c1. Prepare the Spiro-OMeTAD precursor solution

[0031] Use Spiro-OMeTAD as the hole transport layer. Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, stir until completely dissolved, and then add 17.5 μL of a LiTFSID (acetonitrile) solution with a concentration of 520 mg / mL and 28.5 μL of t-BP; It should be noted that the Spiro-OMeTAD precursor solution must be kept stirring at all times before spin coating;

[0032] According to the embodiment of the present invention, the deposition of the electron transport layer includes: plasma treating the cleaned and dried flexible conductive substrate for 10 min, aiming to clean the surface and increase the wettability to facilitate the uniform spreading of the solution; Filter the prepared SnO 2 solution with a 0.25 μm inorganic filter head; Spin coat using a program of 3000 rpm, 3000 rpm / s, 30 s, and then place it on a heating plate at 150 °C for annealing for 30 min.

[0033] According to the embodiment of the present invention, the deposition of the perovskite layer includes: plasma cleaning the cooled tin dioxide glass, transferring it to the glove box, and first filtering it with a 0.22 μm organic filter head. Subsequently, uniformly drop 60 μL of the prepared perovskite precursor solution on the flexible conductive substrate; Set the spin coater program to 1000 rpm / s, 10 s; 5000 rpm, 3000 rpm / s, 30 s, and add 110 μL of chlorobenzene solution during the last 5 - 3 s of the program; After the program stops, transfer the film to a heating plate at 105 °C for annealing for 30 min;

[0034] According to the embodiment of the present invention, the deposition of the hole transport layer includes: depositing 60 μL of HITM on the perovskite film, with a program of 4000 rpm, 2000 rpm / s, 30 s, and then placing it in a moisture-proof cabinet for 24 h.

[0035] According to an embodiment of the present invention, the vapor-deposited metal electrode includes: placing perovskite in a mask template, putting gold / silver into the vapor deposition chamber, vapor-depositing at 0.05 A / s for 5 nm, 0.10 A / s until 10 nm, and 0.8 A / s until 80 nm, and then putting it into a moisture-proof cabinet.

[0036] Beneficial effects

[0037] The thermal expansion coefficients of the commonly used ITO and IZO substrates for perovskite solar cells are 6 to 7 ppm / °C. When using substrates PEN or PET and conductive layers ITO and IZO to prepare perovskite solar cells, there is a large difference in the linear thermal expansion coefficients between the substrate and the conductive layer (the thermal expansion coefficients of PEN and PET are 80 ppm / °C and 90 ppm / °C respectively). In the process of depositing the electron transport layer and the perovskite layer on the flexible conductive substrate for preparing perovskite solar cells, heat treatment such as heating and annealing is required. Once the difference in thermal expansion coefficients between the substrate and the conductive layer is large, it is easy to cause different deformation sizes of the two materials in the conductive substrate, material mismatch, and even curling, making it impossible to carry out subsequent processing and preparation. The thermal expansion coefficients of the two polyimide films used in the present invention are less different from ITO or IZO, with good matching during subsequent heating, high material flatness, and convenient for subsequent processing. Further, the two polyimide films used in the present invention have good transparency and high temperature resistance, so they are suitable for preparing flexible conductive substrates for perovskite solar cells. Description of the drawings

[0038] Figure 1 Ultraviolet transmission spectra of polyimide films prepared using 6FDA-6FAPB and ODPA-6FAPB.

[0039] Figure 2 Thermal expansion coefficient test diagrams of polyimide films prepared using 6FDA-6FAPB (a) and ODPA-6FAPB (b).

[0040] Figure 3 Schematic diagram of the structure of a perovskite solar cell.

[0041] Figure 4 Photovoltaic conversion efficiency of perovskite solar cells in Examples 2 and 4.

[0042] Figure 5 Photos of PET / ITO film and PI / ITO film after annealing at 150 °C for 30 min. Detailed implementation manners

[0043] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the described examples are only used to help understand the present invention, and the protection scope of the present invention should include all the contents of the claims, not limited to this embodiment only.

[0044] In the following examples, ultraviolet-visible absorption spectroscopy (UV-Vis Spectra) was used to test the prepared flexible conductive substrate, and the characterization results of its optical transmittance performance were obtained. The specific results are as Figure 1 shown. It can be seen from Figure 1 that the light transmittance of both flexible conductive substrates is 86%.

[0045] In the following examples, the method for testing the sheet resistance is to measure the sheet resistance of the prepared conductive thin film by using the four-probe method.

[0046] In the following examples, the method for testing the photoelectric conversion efficiency of the perovskite solar cell is as follows: Using a J-V test light source, placing the perovskite solar cell under a specific light source, applying different voltages to measure the output current of the cell, and a J-V curve of the device can be plotted. This curve can be used to test various parameters of the perovskite solar cell, including short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency. The test results are as Figure 4 shown. It can be seen from Figure 4 that the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency of the perovskite solar cell obtained in Example 4 are 19.08 mA / cm 2 , 1.61 V, 79%, and 17.46% respectively. The short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency of the perovskite solar cell obtained in Example 2 are 19.05 mA / cm 2 , 1.58 V, 79%, and 17.39% respectively.

[0047] Example 1

[0048] Preparation of polyimide film: Under a nitrogen atmosphere, 5 mmol of ODPA and 5 mmol of 6FAPB were stirred and dissolved in 10 mL of DMAc solution in an ice bath until the raw materials were completely dissolved in the DMAc solution. Stirring was continued for 24 h until the solution became clear and viscous. The solution was slowly poured onto a glass plate, and a flat wet film was obtained using a doctor blade coater. Then, thermal imidization was carried out on it by stepwise heating (60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h) to obtain a polyimide film. It was peeled off from the glass plate using deionized water and dried in an oven to obtain a polyimide film with a thickness of about 90 nm, uniform and colorless and transparent.

[0049] Preparation of flexible conductive substrate: A commercial IZO target with a purity of 99.99 wt% is placed in a water-cooled RF cathode target slot in the sputtering chamber of a magnetron sputtering device. A flexible transparent polyimide film with a thickness of 90 μm after peeling is placed on the substrate holder, and the substrate holder is inserted into the substrate tray in the sputtering chamber. The distance between the target and the substrate is adjusted to 90 - 130 mm. The sputtering chamber and the gas pipeline are evacuated so that the base vacuum of the sputtering chamber is 1.0×10 -4 Pa. Then, argon gas with a purity of 99.99% is introduced into the sputtering chamber, and the pumping rate is adjusted so that the gas pressure in the sputtering chamber is 3 Pa. After turning on the RF power supply of the IZO target, the gas pressure is adjusted to 0.5 Pa. After the RF glow discharge is stable, the baffle is opened, and an IZO transparent conductive film with a thickness of 200 nm is deposited by sputtering. The obtained flexible conductive substrate has a sheet resistance of 60 Ω / □ and an average visible light transmittance of 86%. The structure and optoelectronic properties of the flexible conductive substrate are stable, and the IZO and polyimide are firmly bonded.

[0050] The preparation process of the perovskite solar cell device is as follows:

[0051] Cleaning the flexible conductive substrate: The flexible conductive substrate obtained by magnetron sputtering is cut into pieces with a size of 18 mm x 24 mm. The surface of the flexible conductive substrate is scrubbed with dishwashing liquid to remove dust and impurities, etc., and then placed on the cleaning rack. After cleaning, it is put into a large beaker, filled with deionized water to cover the pieces, the cup mouth is covered with tin foil, ultrasonically vibrated for 15 min, then ultrasonically vibrated with ethanol for 15 min, and then placed in an oven at 70 °C to dry the solvent. After taking it out, a 6 mm high-temperature resistant tape is pasted at the cathode.

[0052] Depositing the electron transport layer: The cleaned and dried flexible conductive substrate is treated by plasma for 10 min, aiming to clean the surface and increase the wettability to facilitate the uniform spreading of the solution. The pre-prepared SnO 2 solution is filtered with a 0.25 μm inorganic filter head. Spin coating is carried out using the program of 3000 rpm, 3000 rpm / s, 30 s, and then annealed on a hot plate at 150 °C for 30 min.

[0053] Depositing the perovskite layer: The cooled tin dioxide glass is subjected to plasma cleaning, and after being transferred to the glove box, it is first filtered with a 0.22 μm organic filter head. Subsequently, 60 μL of the prepared perovskite precursor solution is uniformly dropped on the flexible conductive substrate. The program of the spin coater is set to 1000 rpm, 1000 rpm / s, 10 s; 5000 rpm, 3000 rpm / s, 30 s, and 110 μL of chlorobenzene solution is dropped in the last 5 - 3 s of the program. After the program stops, the film is transferred to a hot plate at 105 °C for annealing for 30 min.

[0054] Deposition of hole transport layer: Deposit 60 μL of hole transport layer on the perovskite film. The procedure is 4000 rpm, 2000 rpm / s, 30 s, and then place it in a moisture-proof cabinet for 24 h.

[0055] Deposition of metal electrode: Place the perovskite in a mask template, put gold / silver into the evaporation chamber and evaporate at 0.05 A / s for 5 nm, 0.10 A / s until 10 nm, and 0.8 A / s until 80 nm. Then place it in a moisture-proof cabinet.

[0056] Example 2

[0057] Preparation of polyimide film: Under a nitrogen atmosphere, dissolve 5 mmol of ODPA and 5 mmol of 6FAPB in 10 mL of DMAc solution with stirring in an ice bath until the raw materials are completely dissolved in the DMAc solution. Continue stirring and reacting for 24 h until the solution becomes clear and viscous. Slowly pour the solution onto a glass plate and use a doctor blade to obtain a flat wet film. Then perform thermal imidization on it by stepwise heating (60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h) to obtain a polyimide film. Peel it off from the glass plate with deionized water and dry it in an oven to obtain a polyimide film with a thickness of about 90 nm, uniform and colorless and transparent.

[0058] Preparation of flexible conductive substrate: Install a commercially available ITO target with a purity of 99.99 wt% in a water-cooled radio frequency cathode target slot in the sputtering chamber of a magnetron sputtering device. Place the peeled flexible transparent polyimide film with a thickness of 90 μm in the substrate holder, insert the substrate holder into the substrate tray in the sputtering chamber, and adjust the distance between the target and the substrate to 90 - 130 mm; evacuate the sputtering chamber and the gas pipeline to make the base vacuum of the sputtering chamber 1.0×10 -4 Pa, then fill the sputtering chamber with argon with a purity of 99.99%, adjust the pumping rate to make the gas pressure in the sputtering chamber 3 Pa; after turning on the radio frequency power supply of the ITO target, adjust the gas pressure to 0.5 Pa. After the radio frequency glow discharge is stable, open the baffle and perform sputtering deposition of an ITO transparent conductive film with a thickness of 200 nm. The obtained flexible conductive substrate has a sheet resistance of 50 Ω / □ and an average visible light transmittance of 86%.

[0059] Prepare the perovskite solar cell device according to the method of Example 1.

[0060] Example 3

[0061] Preparation of polyimide film: Under a nitrogen atmosphere, 5 mmol of 6FDA and 5 mmol of 6FAPB were dissolved by stirring in 10 mL of DMAc solution in an ice bath until the raw materials were completely dissolved in the DMAc solution. Stirring was continued for 24 h until the polyamic acid solution became clear and viscous. The solution was slowly poured onto a glass plate, and a flat wet film was obtained using a doctor blade coater. Then, thermal imidization was carried out on it with a stepped temperature increase of (60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h) to obtain a polyimide film. It was peeled off from the glass plate using deionized water and dried in an oven to obtain a polyimide film with a thickness of about 90 nm, uniform and colorless and transparent.

[0062] Preparation of flexible conductive substrate: A commercially available IZO target with a purity of 99.99 wt% was placed in a water-cooled radio frequency cathode target slot in the sputtering chamber of a magnetron sputtering device. A flexible transparent polyimide film with a thickness of 90 μm after peeling was placed on a substrate holder, and the substrate holder was inserted into the substrate tray in the sputtering chamber. The distance between the target and the substrate was adjusted to 90 - 130 mm; the sputtering chamber and the gas pipeline were evacuated so that the base vacuum of the sputtering chamber was 1.0×10 -4 Pa. Then, argon with a purity of 99.99% was introduced into the sputtering chamber, and the pumping rate was adjusted so that the gas pressure in the sputtering chamber was 3 Pa; after the radio frequency power supply of the IZO target was turned on, the gas pressure was adjusted to 0.5 Pa. After the radio frequency glow discharge was stable, the baffle was opened, and an IZO transparent conductive film with a thickness of 200 nm was deposited by sputtering. The obtained flexible conductive substrate had a sheet resistance of 60 Ω / square and an average visible light transmittance of 86%. The structure and optoelectronic properties of the flexible conductive substrate were stable, and the combination of IZO and polyimide was firm.

[0063] The perovskite solar cell device was prepared according to the method of Example 1.

[0064] Example 4

[0065] Preparation of polyimide film: Under a nitrogen atmosphere, 5 mmol of 6FDA and 5 mmol of 6FAPB were dissolved by stirring in 10 mL of DMAc solution in an ice bath until the raw materials were completely dissolved in the DMAc solution. Stirring was continued for 24 h until the solution became clear and viscous. The solution was slowly poured onto a glass plate, and a flat wet film was obtained using a doctor blade coater. Then, thermal imidization was carried out on it with a stepped temperature increase of (60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h) to obtain a polyimide film. It was peeled off from the glass plate using deionized water and dried in an oven to obtain a polyimide film with a thickness of about 90 nm, uniform and colorless and transparent.

[0066] Preparation of flexible conductive substrate: A commercial ITO target with a purity of 99.99 wt% is placed in a water-cooled radio frequency cathode target slot in the sputtering chamber of a magnetron sputtering device. A flexible transparent polyimide film with a thickness of 90 μm after peeling is placed on the substrate holder, and the substrate holder is inserted into the substrate tray in the sputtering chamber. The distance between the target and the substrate is adjusted to 90 - 130 mm. The sputtering chamber and the gas pipeline are evacuated so that the base vacuum of the sputtering chamber is 1.0×10 -4 Pa. Then, argon with a purity of 99.99% is filled into the sputtering chamber, and the pumping volume is adjusted so that the gas pressure in the sputtering chamber is 3 Pa. After turning on the radio frequency power supply of the ITO target, the gas pressure is adjusted to 0.5 Pa. After the radio frequency glow discharge is stable, the baffle is opened, and an ITO transparent conductive film with a thickness of 200 nm is sputter-deposited. The obtained flexible conductive substrate has a sheet resistance of 50 Ω / □ and an average visible light transmittance of 86%. The structure and optoelectronic properties of the flexible conductive substrate are stable, and the ITO and polyimide are firmly bonded.

[0067] The perovskite solar cell device is prepared according to the method of Example 1.

[0068] Comparative Example 1

[0069] The thermal expansion coefficient of the PI prepared from AB-MPBZ and HPMDA disclosed in the literature [Li, D. et al. Synthesis of colorless polyimides with high T g and low coefficient of thermal expansion from benzimidazolediamine containing biamide. J. Polym. Sci. 61, 818–828 (2023).] is 22 ppm / °C, which also has a large difference from the thermal expansion coefficients of ITO and IZO as described above, and a qualified flexible conductive substrate cannot be prepared.

[0070] Test Example 1

[0071] In addition, a micrometer is used to measure the thickness of the PI films prepared in the examples and Comparative Example 1 respectively. The transmittance of the PI films is tested using ultraviolet-visible absorption spectroscopy (UV-Vis Spectra). The thermal expansion coefficient of the PI films is tested using a thermomechanical analyzer (TMA). And the temperature at which the PI films have a 5% thermal weight loss is tested using thermogravimetric analysis (TG). The obtained results are shown in Table 1 below. As can be seen from Table 1, the PI films prepared from 6FDA-6FAPB and ODPA-6FAPB have significantly better optical transparency, thermal stability, and a thermal expansion coefficient more matched with ITO or IZO compared with the PI properties disclosed in the literature.

[0072] Table 1

[0073]

[0074]

[0075] Comparative Example 2

[0076] Using the method in Example 1, ITO was sputtered onto the surfaces of PET and PI (PI prepared from 6FDA-6FAPB) respectively, and then the film was placed on a heating table at 150 °C for annealing treatment for 30 minutes. The photos of the obtained materials are as Figure 5 shown. As can be seen from Figure 5 , the PET / ITO composite film curled up after annealing treatment, while the PI / ITO composite film did not show obvious deformation after annealing.

[0077] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Use of a polyimide film in the preparation of a conductive substrate for a perovskite solar cell, wherein the polyimide is a polymer of a dianhydride monomer and a diamine monomer, the dianhydride monomer is selected from 4,4'-biphenyl dianhydride (ODPA) or hexafluorodiacid anhydride (6FDA), and the diamine monomer is selected from 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB).

2. The use according to claim 1, characterized in that, the polyimide film is prepared by the following method: The dianhydride monomer ODPA or 6FDA and the diamine monomer 6FAPB are subjected to a stepwise temperature increase reaction in DMAc at 60 °C / 10 h; 80 °C / 10 h; 200 °C / 3 h; 250 °C / 2 h: wherein, the molar ratio of the dianhydride monomer to the diamine monomer is 1:1; n is an integer of 200 or more.

3. A conductive substrate for a perovskite solar cell, characterized in that, it comprises the polyimide film as described in claim 1 or 2 above and an ITO or IZO sputtering layer on the surface of the film.

4. The conductive substrate for a perovskite solar cell according to claim 3, characterized in that, the thickness of the transparent conductive layer ITO or IZO on the conductive substrate for a perovskite solar cell is 100 - 400 nm.

5. The conductive substrate for a perovskite solar cell according to claim 3 or 4, characterized in that, its light transmittance is 80% or more.

6. The conductive substrate for a perovskite solar cell according to any one of claims 3 - 5, characterized in that, its light transmittance is 85% or more.

7. A method for preparing a conductive substrate for a perovskite solar cell using the polyimide film described in claim 1 or 2, characterized in that, it comprises: sputtering ITO or IZO onto the polyimide film described in claim 1 or 2.

8. The method according to claim 7, characterized in that, the following steps are used to prepare the conductive substrate for the solar cell: a. Install the target ITO or IZO in the radio frequency cathode target slot of the magnetron sputtering device, place the polyimide film in the substrate holder, insert the substrate holder into the substrate tray in the sputtering chamber, and adjust the distance between the target and the substrate to 90 - 130 mm; b. Pump the sputtering chamber to make the vacuum degree of the sputtering chamber below 1.0×10 -4 Pa. Fill the sputtering chamber with argon gas, adjust the pumping volume to make the gas pressure in the sputtering chamber 0.1 - 6 Pa; turn on the RF power supply of the target, with the power being 30 - 60 w. After pre-sputtering for a period of time, open the baffle and sputter-deposit the transparent conductive layer ITO or IZO onto the surface of the polyimide film to obtain a conductive substrate.

9. A perovskite solar cell, which comprises the conductive substrate for a perovskite solar cell according to any one of claims 3 - 6, an electron transport layer, a perovskite layer, a hole transport layer and a metal electrode, and the conductive substrate, the electron transport layer, the perovskite layer, the hole transport layer and the metal electrode are arranged in sequence; the electron transport layer is deposited on one side of the PI film having ITO or IZO.

10. The method for preparing the perovskite solar cell according to claim 9, characterized in that, it comprises the following steps: on depositing an electron transport layer, a perovskite layer and a hole transport layer in sequence on the conductive substrate according to any one of claims 3 - 6, and evaporating and depositing a metal electrode; the electron transport layer is deposited on one side of the PI film having ITO or IZO.

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