Preparation method for preparing super-thick formamidine and methylamine mixed perovskite thin film through blade coating method and application of super-thick formamidine and methylamine mixed perovskite thin film

Abstract

The invention relates to the technical field of film preparation, in particular to a preparation method for preparing an ultra-thick formamidine and methylamine mixed perovskite film through a blade coating method and application of the super-thick formamidine and methylamine mixed perovskite film through the blade coating method. The preparation method comprises the following steps that a precursor solution is prepared, specifically, methyl ammonium iodide, formamidine ammonium iodide and lead iodide are put into a ternary mixed solvent, and preparation of the precursor solution is completed; and performing deposition treatment, namely depositing the precursor solution prepared in the step 1 on a glass substrate by adopting a blade coating method to form a thin film, and completing the deposition treatment of the glass substrate. In the ternary mixed solvent, ethylene glycol monomethyl ether ensures rapid drying, N, N-dimethylformamide stabilizes the morphology of the wet film, dimethyl sulfoxide regulates and controls the crystallization process, and after the perovskite wet film prepared under the system is subjected to vacuum flash evaporation and thermal annealing, the perovskite wet film can be rapidly dried. And finally, the high-quality perovskite thin film with large crystal grains, uniform distribution, black and bright mirror surfaces on the upper surface and the lower surface and no void defect is formed, and the requirement of a high-performance solar cell on an active layer structure is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thin film preparation, in particular to a preparation method of a super-thick formamidinium methylamine mixed perovskite thin film prepared by a doctor blade method and application thereof. BACKGROUND

[0002] The doctor blade method for preparing perovskite thin films is an efficient and low-cost thin film preparation method, which is mainly used in the field of perovskite solar cells. Through the doctor blade method, perovskite precursor solution can be uniformly coated on the substrate, and after annealing treatment, high-quality perovskite thin films are formed. Perovskite solar cells, as the third generation of high-efficiency, clean and sustainable photovoltaic technology, have the advantages of high energy conversion efficiency, low cost, large-area thick film preparation and flexible substrate compatibility. In recent years, it has attracted widespread attention. With continuous research, the performance of perovskite cells continues to improve, and the efficiency of polycrystalline perovskite solar cells has only increased from 25.2% to 26.7%, indicating that its performance development has reached a bottleneck. Based on the calculation of density functional theory, it is pointed out that the band gap below the absorption characteristics of perovskite material is closely related to the spatial orientation of organic molecules. When CH3NH3 + arranges along the crystal direction, the PbI6 octahedron is twisted, resulting in a direct band gap to an indirect band gap. However, the absorption coefficient of indirect band gap transition is significantly lower than that of direct band gap, which means that if you want to fully utilize its indirect band gap absorption characteristics, the thickness of the perovskite thin film needs to reach several microns or even thicker.

[0003] In the prior art, the thickness of most perovskite thin films prepared by the current solution method cannot meet the requirements, and the thickness of the perovskite thin film prepared by the anti-solvent method is usually not more than 1 μm, and the thickness of the perovskite thin film prepared by the doctor blade method can only reach about 2 μm, which cannot meet the optical path requirement of indirect band gap absorption. At the same time, the existing solution process cannot realize the preparation of large-area, thickness-controllable perovskite thin films.

[0004] Therefore, the present application provides a preparation method of a super-thick formamidinium methylamine mixed perovskite thin film prepared by a doctor blade method and application thereof. SUMMARY

[0005] The present application aims to provide a preparation method of a super-thick formamidinium methylamine mixed perovskite thin film prepared by a doctor blade method and application thereof. The thickness of the perovskite thin film prepared by the present application can be controlled in the range of 0.1-3 μm, and the perovskite thin film has excellent structural characteristics such as uniform crystal grains, no pinholes and no delamination.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a preparation method of a super-thick formamidinium methylamine mixed perovskite thin film prepared by a doctor blade method, comprising the following steps: Step one: preparation of precursor solution, methyl iodide amine, formamidinium iodide and lead diiodide are added to a ternary mixed solvent to complete the preparation of the precursor solution; Step two: deposition treatment, using a doctor blade coating method to deposit the precursor solution prepared in step one on the glass substrate to form a thin film, and complete the deposition treatment of the glass substrate; Step three: vacuum flash, immediately place the glass substrate that has completed the deposition treatment in step two into a vacuum flash chamber for vacuum flash treatment; Step four: heat treatment, place the vacuum flash treated glass substrate on a hot stage for heat treatment, and complete the preparation of the perovskite thin film.

[0007] Preferably, the preparation method of the ternary mixed solvent in step one is to select ethylene glycol methyl ether, N,N-dimethylformamide and dimethyl sulfoxide lead to add them into a mixing barrel, and place them in a water bath kettle, set the temperature to 50℃, and stir them at 200r / min for 30min through a mechanical stirrer, then stand still for 10min, and complete the preparation of the ternary mixed solvent.

[0008] Preferably, in step one, the mass ratio of methyl amine iodide, methyl amine iodide and lead diiodide is 72.2:155.8:645.4, and the volume ratio of the solvents of ethylene glycol methyl ether, N,N-dimethylformamide and dimethyl sulfoxide lead is 920:40:40, the methyl amine iodide, methyl amine iodide and lead diiodide are placed in the mixing barrel at a molar ratio of 3:7, and the electric stirrer is used to stir the solvents at 400r / min at room temperature for 30min, then the solvents are filtered through a polytetrafluoroethylene filter film with a pore size of 0.22μm after being taken out, and the preparation of the precursor solution is completed.

[0009] Preferably, in step two, the glass substrate is ITO / PTAA:F4-TCNQ / PMMA.

[0010] Preferably, in step two, the deposition is carried out in a fume hood, the environmental temperature is 20℃, the relative humidity is 50±5%, an automatic doctor blade coater is used, the slit width of the doctor blade is set to 250μm, the doctor blade coating speed is set to 20mm / s, the substrate temperature is controlled at 15-20℃, and the volume of the precursor solution used for single doctor blade coating is 8μL.

[0011] Preferably, in step three, the glass substrate that has completed the doctor blade coating treatment is immediately placed in a vacuum box, and the system vacuum degree is reduced to the limit within 10s through a double-pole rotary vane vacuum pump, and the vacuum flash time is maintained for 60s.

[0012] Preferably, in step four, the vacuum flash treated glass substrate is placed on a hot stage for heat treatment, and the temperature of the hot stage is 100℃, and the heat treatment is continued for 20min.

[0013] Preferably, the concentration of the precursor solution prepared in step one is 1.4M, and the concentration of the lead diiodide is 0.5-1.4mol / L.

[0014] The application of a doctor blade method for preparing an ultra-thick formamidinium methylamine mixed perovskite film, the perovskite film prepared by the application is suitable for an optical absorption layer of a trans-structure perovskite solar cell, comprising: taking ITO glass as an anode, depositing a PTAA:F4-TCNQ hole transport layer, depositing a PMMA hole interface layer on the hole transport layer, then depositing a perovskite active layer, and sequentially spin-coating PC 60 BM electron transport layer, Bphen cathode interface layer, and finally evaporating Ag as a cathode.

[0015] Preferably, the ITO has a thickness of 120 nm, the PTAA:F4-TCNQ has a thickness of 30-40 nm, the spin-coating rate is 6000 rpm, the time is 30 s, the annealing temperature is 120 DEG C, and the time is 2 min; the PMMA interface layer has a thickness of 3-8 nm, the spin-coating conditions are the same, the annealing temperature is 100 DEG C, and the time is 1 min; the electron transport layer PC 60 BM has a thickness of 70-100 nm, the spin-coating rate is 2000 rpm, and the time is 60 s; the Bphen cathode interface layer has a thickness of 5-10 nm, the spin-coating rate is 6000 rpm, and the time is 60 s; and the Ag cathode has a thickness of 100 nm, and the evaporation rate is 1 nm / s.

[0016] Compared with the prior art, the application has the following beneficial effects: 1. In the ternary mixed solvent, the ethylene glycol methyl ether ensures rapid drying, the N,N-dimethylformamide stabilizes the wet film morphology, and the dimethyl sulfoxide regulates the crystallization process. In this system, the perovskite wet film prepared by vacuum flash evaporation and heat annealing finally forms a high-quality perovskite film with large crystal grains, uniform distribution, black and bright mirror surfaces on the upper and lower surfaces, and no void defects, which meets the requirements of high-performance solar cells for active layer structure.

[0017] 2. The application adopts a solution doctor blade method to replace the spin coating process, and is suitable for preparing a large-area perovskite film with high uniformity and scalability.

[0018] 3. The application can prepare a perovskite film with a thickness ranging from 0.1 to 3 microns by precisely controlling the lead diiodide concentration in the precursor solution, and has excellent structural characteristics such as uniform crystal grains, no pinholes, and no delamination, which significantly improves the controllability and film quality of the ultra-thick perovskite film. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 SEM image of the perovskite film in Comparative Example 1; Figure 2 SEM image of the perovskite film in Comparative Example 2; Figure 3 SEM image of the perovskite film in Comparative Example 3; Figure 4 FA prepared in Example One 0.3 MA 0.7 SEM morphology of PbI3perovskite film at different magnifications; Figure 5 FA of different thicknesses in Example One 0.3 MA 0.7 Cross-sectional SEM image of PbI3perovskite film; Figure 6 FA in Example One 0.3 MA 0.7 UV-Vis absorption spectrum of PbI3perovskite film; Figure 7 FA prepared in Example One 0.3 MA 0.7 Steady-state fluorescence emission spectrum of PbI3perovskite film; Figure 8 Structure diagram of trans-perovskite solar cell in Example One; Figure 9 Current-voltage (J-V) test curve of perovskite solar cell prepared in Example One; Figure 10 Steady-state efficiency output curve of perovskite solar cell in Example One; Figure 11 Structure diagram of perovskite battery module prepared in Example One; Figure 12 J-V test curve of perovskite battery module in Example One. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0021] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings.

[0022] Example One: A preparation method of an ultra-thick formamidinium methylamine mixed perovskite film prepared by a doctor blade method, comprising the following steps: Step One: Preparation of precursor solution, methylammonium iodide, formamidinium iodide and lead diiodide are added into a ternary mixed solvent to complete the preparation of the precursor solution; Step two: deposition treatment, using a doctor blade coating method to deposit the precursor solution prepared in step one on the glass substrate to form a thin film, and complete the deposition treatment of the glass substrate; Step three: vacuum flash, immediately place the glass substrate that has completed the deposition treatment in step two into a vacuum flash chamber for vacuum flash treatment; Step four: heat treatment, place the glass substrate that has completed the vacuum flash treatment into a hot stage for heat treatment, and complete the preparation of the perovskite thin film.

[0023] The preparation method of the ternary mixed solvent in step one is as follows: select ethylene glycol methyl ether, N,N-dimethylformamide, and lead dimethyl sulfoxide, and place them into a mixing bucket and a water bath, set the temperature to 50℃, and stir them at 200r / min for 30min through a mechanical stirrer, then stand still for 10min, and complete the preparation of the ternary mixed solvent.

[0024] In step one, the mass ratio of methyl amine iodide, methylformamidine ammonium iodide, and lead diiodide is 72.2:155.8:645.4, and the volume ratio of methyl ethylene glycol methyl ether, N,N-dimethylformamide, and lead dimethyl sulfoxide is 920:40:40. The methyl amine iodide, methylformamidine ammonium iodide, and lead diiodide are placed into the mixing bucket in a molar ratio of 3:7 with the ternary mixed solvent, and the solvent is stirred at 400r / min for 30min through an electric stirrer at room temperature. After being taken out, it is filtered through a polytetrafluoroethylene filter membrane with a pore size of 0.22μm to complete the preparation of the precursor solution.

[0025] In step two, the glass substrate is ITO / PTAA:F4-TCNQ / PMMA.

[0026] In step two, the deposition is carried out in a fume hood, the environmental temperature is 20℃, the relative humidity is 50±5%, an automatic doctor blade coater is used, the doctor blade slit width is set to 250μm, the doctor blade coating speed is set to 20mm / s, the substrate temperature is controlled at 15-20℃, and the volume of the precursor solution used for single doctor blade coating is 8μL.

[0027] In step three, the glass substrate that has completed the doctor blade coating treatment is immediately placed into a vacuum box, and the system vacuum degree is reduced to the limit within 10s through a double-pole rotary vane vacuum pump, and the vacuum flash time is maintained for 60s.

[0028] In step four, the glass substrate that has completed the vacuum flash treatment is placed into a hot stage for heat treatment, the hot stage temperature is 100℃, and the heat treatment is continuously performed for 20min.

[0029] The concentration of the precursor solution prepared in step one is 1.4M, and the concentration of lead diiodide is 0.5-1.4mol / L.

[0030] Specifically, by regulating the concentration of lead diiodide, the film thickness can be precisely adjusted: 1.4 mol / L corresponds to a thickness of about 3 microns; 1 mol / L corresponds to 1.5 microns; 0.7 mol / L corresponds to 0.7 microns; 0.5 mol / L corresponds to 0.3 microns; 0.4 mol / L corresponds to 0.2 microns.

[0031] The application of a doctor blade method for preparing an ultra-thick formamidine methylamine mixed perovskite film, the perovskite film prepared by the application is suitable for a light-absorbing layer of a trans-structure perovskite solar cell, comprising: taking ITO glass as an anode, depositing a PTAA:F4-TCNQ hole transport layer, depositing a PMMA hole interface layer thereon, then depositing a perovskite active layer, and sequentially spin-coating PC 60 BM electron transport layer, Bphen cathode interface layer, and finally evaporating Ag as a cathode.

[0032] The ITO thickness is 120 nm, the PTAA:F4-TCNQ thickness is 30-40 nm, the spin-coating speed is 6000 rpm, the time is 30 s, the annealing temperature is 120 DEG C, and the time is 2 min; the PMMA interface layer thickness is 3-8 nm, the spin-coating conditions are the same, the annealing temperature is 100 DEG C, and the time is 1 min; the electron transport layer PC 60 BM thickness is 70-100 nm, spin-coating speed is 2000 rpm, time is 60 s; Bphen cathode interface layer thickness is 5-10 nm, spin-coating speed is 6000 rpm, time is 60 s, Ag cathode thickness is 100 nm, and evaporation speed is 1 nm / s.

[0033] Specifically, the trans perovskite solar cell structure constructed in the application is ITO / PTAA:F4-TCNQ / PMMA / perovskite / PCBM / Bphen / Ag, wherein ITO (indium tin oxide) is a transparent conductive anode, PTAA:F4-TCNQ is a hole transport layer, PMMA is a hole interface regulation layer, PCBM is an electron transport layer, Bphen is a cathode modification layer, and Ag is a top metal electrode.

[0034] The specific preparation process is as follows: first, the patterned ITO glass substrate (previously formed with an electrode pattern by laser scribing) is sequentially subjected to ultrasonic cleaning treatment with ethanol, acetone and ultrapure water, then is sufficiently blown dry with nitrogen, and is treated in a UV ozone treatment instrument for 15 minutes to improve surface wettability. Subsequently, in a low-humidity nitrogen glove box, a PTAA:F4-TCNQ chlorobenzene solution (concentration of 5 mg / mL) is spin-coated at a speed of 6000 rpm to form a hole transport layer with a thickness of about 30 nm, and is annealed at 100 DEG C for 2 minutes. A PMMA ethyl acetate solution (0.5 mg / mL) is continuously spin-coated to obtain an interface layer with a thickness of about 5 nm, and is annealed at 100 DEG C for 1 minute.

[0035] After cooling, the perovskite absorber layer was prepared by the same doctor-blade method as in Example 1, with a precursor solution concentration of 0.7 M, forming a perovskite film of about 400 nm thickness, followed by spin-coating of PCBM solution in chlorobenzene (20 mg / mL) at 6000 rpm, forming an electron transport layer of 70-100 nm thickness; and spin-coating of Bphen solution in ethanol (0.7 mg / mL) in the same way, forming a cathode buffer layer of about 7 nm. Finally, the sample with the completed structure was transferred to a vacuum evaporation system, and an Ag electrode of 100 nm thickness was evaporated under a vacuum of 5 x 10 - 4 The device was completed by evaporating an Ag electrode of 100 nm thickness under a vacuum of 5 x 10

[0036] Specifically, to achieve modular applications, the present application also constructed a large-area perovskite solar cell module, which has the same device structure as the single cell, still ITO / PTAA:F4-TCNQ / PMMA / perovskite / PCBM / Bphen / Ag. The module was divided into 10 series-connected sub-cells by laser scribing (P1, P2, P3) technology in a 5 x 5 cm² area, as shown in Figure 11 .

[0037] The specific preparation steps are as follows: first, the ITO substrate was patterned and scribed using a P1 laser (power 0.5 W, speed 2000 mm / s, wavelength 1064 nm), forming an independent anode area of the series-connected sub-cell. Subsequently, the same process as the single cell was followed to sequentially clean, ultraviolet ozone treat, and spin-coat the PTAA:F4-TCNQ and PMMA layers in a low-humidity glove box at 6000 rpm, with annealing treatment for 2 min and 1 min, respectively. After cooling, a doctor blade with a 100 μm slot was used to doctor-blade the perovskite absorber layer at a speed of 20 mm / s, with a single solution usage of 20 μL. Vacuum flash treatment was performed immediately after doctor-blading, with a vacuum reaching the limit within 10 s and being maintained for 60 s, followed by heat treatment at 100°C for 20 min on a hot table. After spin-coating the PCBM and Bphen layers, P2 laser (power 0.1 W, speed 5000 mm / s) etching was performed to ensure complete removal of all the covering film layers on the ITO surface without damaging the ITO layer. Finally, an Ag electrode (100 nm) was evaporated under a vacuum of 5 x 10 -4 Pa, and P3 laser (power 0.1 W, speed 2500 mm / s) scribing was performed to remove the Ag layer without damaging the underlying ITO, completing the module fabrication.

[0038] Comparative Example 1, the difference between the present comparative example and Experimental Example 1 is that the ternary mixed solvent in the present comparative example only uses ethylene glycol methyl ether; Comparative Example 2, the difference between the present comparative example and Experimental Example 1 is that the ternary mixed solvent in the present comparative example does not contain dimethyl sulfoxide; Comparative Example 3, the difference between Comparative Example 3 and Experimental Example 1 is that the ternary mixed solvent in Comparative Example 3 does not contain N,N-dimethylformamide.

[0039] Performance test of perovskite thin film: The perovskite thin films prepared in Experimental Example 1 and Comparative Examples 1, 2 and 3 were tested for performance. First, the surface and cross-sectional morphology of the prepared thin films were characterized by using a German Zeiss Sigma300+ scanning electron microscope (SEM). Figure 4 The surface morphology of a 3-μm-thick perovskite thin film is shown, which is flat and dense, free of pinholes, and has uniform grain size. Figure 5 The cross-sectional images of thin films with different thicknesses (3 μm, 1.7 μm, 0.4 μm and 0.2 μm) are shown, all of which show excellent structural characteristics of uniform crystallization from top to bottom, free of voids and obvious delamination.

[0040] Secondly, the absorption spectrum of the thin film was tested by using an Agilent HP8453 ultraviolet-visible spectrophotometer. Figure 6 The absorption spectrum curve of a 3-μm-thick FA 0.3 MA 0.7 PbI3thin film is shown, which shows that its absorption range covers 300-820 nm, and it has excellent visible light response performance. According to the maximum absorption edge method, the optical band gap Eg of the thin film is 1.51 eV, and it has excellent light absorption capacity.

[0041] Finally, the fluorescence performance of the thin film was tested by using a laboratory-made steady-state fluorescence spectrometer. The steady-state fluorescence spectrum measured by using an 80-mW 532-nm green laser as an excitation light source is shown in Figure 7 The main emission peak is at 800 nm, which is consistent with the absorption spectrum, further verifying the good optoelectronic properties of the thin film.

[0042] In Comparative Example 1, as shown in Figure 1 Due to the extremely fast evaporation speed of ethylene glycol methyl ether, the wet film dries rapidly within 5 seconds, leading to rapid crystallization and insufficient grain growth, forming a rough, small-grained, frosted thin film. Such a thin film has a large surface roughness and poor morphology uniformity, and is difficult to meet the use requirements of high-performance perovskite solar cells; In Comparative Example 2, as shown in Figure 2 The precursor was dissolved in ethylene glycol methyl ether and N,N-dimethylformamide to prepare a thin film. N,N-dimethylformamide delays the evaporation of ethylene glycol methyl ether, providing a more abundant operation window for vacuum flashing, and the thin film surface can achieve a mirror-like black appearance. However, the SEM results show that there is still a large roughness on the surface of the thin film, the grain size is small and unevenly distributed, and the film quality is still limited; In Comparative Example 3, as shown in Figure 3As shown, dimethyl sulfoxide in the system can effectively delay the nucleation of crystals by forming a complex with lead diiodide, and improve the grain size. However, due to the significant difference in the volatilization rate of ethylene glycol methyl ether and dimethyl sulfoxide, ethylene glycol methyl ether volatilizes first to form a white surface during the vacuum flash process, and then dimethyl sulfoxide slowly volatilizes to gradually form a brown intermediate phase, resulting in a layered crystallization process in time and space, and a large number of pores exist in the surface and interior of the perovskite film formed finally, the structure is discontinuous, which seriously affects the device performance. As shown in Example 1, Figure 4 As shown, by mixing the above three solvents in a volume ratio of 920:40:40, the advantages of each solvent are fully integrated: ethylene glycol methyl ether ensures rapid drying, N,N-dimethylformamide stabilizes the wet film morphology, and dimethyl sulfoxide regulates the crystallization process. The perovskite wet film prepared in this system after vacuum flash and heat annealing forms a high-quality perovskite film with large grain size, uniform distribution, black and bright mirror surface on the upper and lower surfaces, and no void defects, which meets the requirements of high-performance solar cells for active layer structure.

[0043] Perovskite battery performance test: all devices are not encapsulated, and the test is completed in air environment. Using Zolix Solar IV-150A-ZZU photovoltaic test system, under AM1.5G (100 mW / cm²) standard sunlight conditions, irradiation is carried out by Zolix-HPS-300XA solar simulator, and Zolix QE-B1 silicon-based standard cell is used for light intensity calibration. Figure 9 The J-V curve of the battery is shown, Figure 10 The steady-state output test curve is shown. From the test results, it can be seen that the perovskite battery device prepared by the doctor blade method exhibits excellent photoelectric conversion performance, with a maximum efficiency of 21.7%, and no obvious performance degradation under continuous 1000s light conditions, which indicates that the crystallization quality of the perovskite film has a significant improvement on the stability of the device; Perovskite module performance test: after the module is simply encapsulated by AB glue, the performance test is carried out in air environment. The J-V curve measuring instrument is consistent with the single cell test system. Figure 12 The J-V test results of the module are shown, and the maximum photoelectric conversion efficiency reaches 14.4%.

[0044] As fully described above, the doctor blade method and vacuum flash treatment method proposed in the present application can be used to construct large-area, high-performance perovskite solar cell modules, which have good expandability and application prospect.

[0045] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "an example", "a specific example" or the like in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0046] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the contents of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method, characterized in that: Includes the following steps: Step 1: Preparation of precursor solution. Methylamine iodide, formammonium iodide and lead diiodide are mixed in a ternary solvent to complete the preparation of the precursor solution. Step 2: Deposition treatment. The precursor solution prepared in Step 1 is deposited on the glass substrate using a blade coating method to form a thin film, thus completing the deposition treatment of the glass substrate. Step 3: Vacuum flash evaporation. Immediately place the glass substrate that has undergone deposition in Step 2 into the vacuum flash evaporation chamber for vacuum flash evaporation. Step 4: Heat treatment. The vacuum flash-treated glass substrate is placed on a hot stage for heat treatment to complete the preparation of the perovskite thin film.

2. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 1, characterized in that, The method for preparing the ternary mixed solvent in step one is as follows: ethylene glycol methyl ether, N,N-dimethylformamide and dimethyl sulfoxide lead are added to a mixing tank and placed in a water bath. The temperature is set to 50°C, and the mixture is stirred at 200 r / min for 30 min by a mechanical stirrer. After standing for 10 min, the preparation of the ternary mixed solvent is completed.

3. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 2, characterized in that, In step one, the mass ratio of methylamine iodide, formamidinium iodide, and lead diiodide is 72.2:155.8:645.4, and the volume ratio of the solvents ethylene glycol monomethyl ether, N,N-dimethylformamide, and dimethyl sulfoxide lead is 920:40:

40. The methylamine iodide, formamidinium iodide, and lead diiodide are placed in a mixing tank with the ternary mixed solvent at a molar ratio of 3:

7. The solvent is stirred with an electric stirrer at 400 r / min for 30 min at room temperature. After stirring, the solution is filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.22 μm to complete the preparation of the precursor solution.

4. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 1, characterized in that, In step two, the glass substrate is ITO / PTAA:F4-TCNQ / PMMA.

5. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 1, characterized in that, In step two, deposition is carried out in a fume hood at an ambient temperature of 20°C and a relative humidity of 50±5%. An automatic scraper is used, with the slit width of the scraper set to 250μm and the scraping speed set to 20mm / s. The substrate temperature is controlled at 15-20°C, and the volume of precursor solution used in a single scraping is 8μL.

6. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 1, characterized in that, In step three, the glass substrate that has been coated is immediately placed in a vacuum box, and the system vacuum is reduced to the limit within 10 seconds by a bipolar rotary vane vacuum pump, maintaining the vacuum flash time for 60 seconds.

7. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 1, characterized in that, In step four, the vacuum flash-treated glass substrate is placed on a hot table for heat treatment at a temperature of 100°C for 20 minutes.

8. The method for preparing ultra-thick formamidinium-methylamine mixed perovskite thin films by a blade coating method according to claim 3, characterized in that, The precursor solution obtained in step one has a concentration of 1.4 M, and the lead diiodide concentration is 0.5-1.4 mol / L.

9. An application of a method for preparing ultrathick formamidinium-methylamine mixed perovskite films by a blade coating method, comprising the method for preparing ultrathick formamidinium-methylamine mixed perovskite films by a blade coating method according to any one of claims 1-8, characterized in that, The perovskite thin film prepared by this invention is suitable as the light-absorbing layer of an inverted perovskite solar cell, comprising: using ITO glass as the anode, depositing a PTAA:F4-TCNQ hole transport layer, depositing a PMMA hole interface layer on it, followed by depositing a perovskite active layer, and then spin-coating PC sequentially. 60 The electron transport layer (BM) and cathode interface layer (Bphen) are constructed, and Ag is finally deposited as the cathode.

10. The application of the blade coating method for preparing ultra-thick formamidinium-methylamine mixed perovskite films according to claim 9, characterized in that, The ITO layer has a thickness of 120 nm, the PTAA:F4-TCNQ layer has a thickness of 30-40 nm, the spin coating speed is 6000 rpm, the time is 30 s, and the annealing temperature is 120℃ for 2 min; the PMMA interface layer has a thickness of 3-8 nm, the spin coating conditions are the same, and the annealing temperature is 100℃ for 1 min; the electron transport layer PC... 60 BM thickness 70-100nm, spin coating rate 2000rpm, time 60s; Bphen cathode interface layer thickness 5-10nm, spin coating rate 6000rpm, time 60s; Ag cathode thickness 100nm, evaporation rate 1nm / s.

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