Method for preparing high-stability perovskite solar cell through perovskite microcrystal recrystallization and in-situ inverse temperature crystallization

Abstract

The invention relates to the technical field of photovoltaic device processes, in particular to a method for preparing a high-stability perovskite solar cell through perovskite microcrystal recrystallization in-situ inverse temperature crystallization. The preparation method comprises the following steps: re-dissolving MAPbI3 microcrystals in gamma-valerolactone (GVL) to prepare a precursor solution; the high-crystallinity perovskite thin film is prepared by adopting a spin-coating method and in-situ inverse-temperature crystallization, and strong absorption in a wide range is still kept between 300 nm and 850 nm. Due to the improvement of the crystal quality of the thin film, the defect state density and the interface carrier recombination probability are reduced, so that the separation and transmission of carriers are improved, and the perovskite solar cell prepared based on the method still keeps relatively high stability under the conditions of high temperature and high humidity.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic device processes, and particularly to a method for preparing a highly stable perovskite solar cell by in-situ inverse temperature crystallization of perovskite microcrystal recrystallization. Background Art

[0002] As an organic-inorganic hybrid semiconductor material, MAPbI3 has been widely studied in the fields of solar cells and the like due to its excellent optoelectronic properties. Although the current energy conversion efficiency of solar cells has exceeded 27% at most, its working life is far from meeting the requirements of practical applications. The main reason is that when preparing the perovskite active layer film by the classical room-temperature anti-solvent supersaturated crystallization method, due to the too-fast crystallization speed, a large number of grain boundaries and various surface defects are inevitably generated, inducing ion migration and making its intrinsic stability poor, seriously affecting the operation stability of the perovskite battery. And currently, traditional high-performance devices often rely on high-purity raw materials, with high costs and poor reproducibility, which is not conducive to commercial applications.

[0003] To solve the above problems, the perovskite crystal re-dissolution strategy is now widely used. The pre-prepared crystals are re-dissolved in good solvents such as DMF and DMSO to prepare a precursor solution, and then a dense perovskite film is prepared under the action of an anti-solvent at a low temperature. Compared with the traditional method of directly mixing raw materials, this method not only has an accurate stoichiometric ratio, but also the perovskite film can well inherit the excellent properties of the original crystal, such as high crystallinity, high purity and low defect state density. Since the synthesis of perovskite crystals belongs to a purification process, the purity requirement for raw materials is relatively low. Therefore, it helps to prepare high-performance perovskite batteries at a lower cost, and is more conducive to the commercial application of perovskite solar cells.

[0004] However, this method has high requirements for the quality of the pre-synthesized crystals. At present, large-size high-quality perovskite single crystals are usually prepared by the inverse temperature crystallization method. The synthesis process has complex steps and requires a long time, which is not conducive to large-scale commercial applications. In addition, the currently commonly used methods all use the action of an anti-solvent at room temperature to promote the volatilization of the solvent, thereby achieving rapid crystallization. This method results in a high defect state density of the film, which is difficult to be stable for a long time and limits its further application. And the ultraviolet-visible light absorption of the perovskite film often shows a rapid decay after 500 nm, which is not conducive to the full-spectrum utilization of sunlight and affects its photovoltaic performance. The solvents and anti-solvents commonly used for re-dissolving to prepare the precursor solution are mostly toxic solvents such as DMF, NMP and chlorobenzene, which pose a great threat to the environment and human body, and are also important factors affecting their applications. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for preparing a highly stable perovskite solar cell by recrystallizing perovskite microcrystals and in-situ inverse temperature crystallization. The present invention dissolves MAPbI3 microcrystals in γ-valerolactone (GVL) again to prepare a precursor solution. By adopting the spin-coating method, in-situ inverse temperature crystallization is carried out to prepare a perovskite thin film with high crystallinity, which still maintains strong absorption in a wide range between 300 - 850 nm. Due to the improvement of the film crystallization quality, the density of defect states and the probability of interfacial carrier recombination are reduced, thereby improving the separation and transport of carriers, so that the perovskite solar cell prepared by this method still maintains high stability under high-temperature and high-humidity conditions.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a highly stable perovskite solar cell by recrystallizing perovskite microcrystals and in-situ inverse temperature crystallization, comprising the following steps:

[0008] 1) Place the FTO conductive glass on a heating substrate and prepare a TiO2 dense layer by spray pyrolysis;

[0009] 2) Spin-coat the mesoporous layer raw material on the obtained TiO2 dense layer and sinter it to prepare a mesoporous TiO2 layer;

[0010] 3) Spin-coat the MAPbI3 microcrystal precursor solution on the obtained mesoporous TiO2 layer and perform annealing treatment to prepare a perovskite layer;

[0011] The concentration of MAPbI3 microcrystals in the MAPbI3 microcrystal precursor solution is 0.75 mmol / mL;

[0012] The spin-coating is carried out in 2 steps. The spin-coating speed in the first step is 1000 rpm and the spin-coating time is 10 s; the spin-coating speed in the second step is 5000 rpm and the spin-coating time is 20 s. Anisole of equal volume is added at the 4th second of the spin-coating time in the second step;

[0013] 4) Spin-coat the transparent solution on the obtained perovskite layer, and then evaporate and deposit an Au electrode to obtain a perovskite solar cell.

[0014] Preferably, the temperature of the heating substrate in step 1) is 475 °C;

[0015] The specification of the FTO conductive glass is: the area is 2.5 cm × 2.5 cm and the thickness is 0.5 cm;

[0016] The conditions of the spray pyrolysis include: using an isopropanol solution with a mass percentage content of 75% for spray pyrolysis, spraying one circle every 30 s, for a total of 30 - 40 min;

[0017] The preparation method of the 75% isopropyl alcohol solution is as follows: Add 515 μL of acetylacetone and 775 μL of diisopropoxybis(acetylacetonato)titanium into 9 mL of isopropyl alcohol.

[0018] Preferably, the components of the mesoporous layer raw material in step 2) are Dyesol-30NR-D and absolute ethanol, and the mass ratio of Dyesol-30NR-D to absolute ethanol is 1:7.

[0019] The average particle size of the Dyesol-30NR-D is 30 nm.

[0020] The conditions for spin-coating the mesoporous layer raw material include: spin-coating for 20 s at 4000 rpm.

[0021] Preferably, the conditions for sintering in step 2) include: the temperature is 500 °C and the time is 12 h.

[0022] Preferably, the area ratio of the spraying amount of the MAPbI3 microcrystalline precursor solution to the area of the mesoporous TiO2 layer in step 3) is 50 μL: 2.5 cm × 2.5 cm.

[0023] Preferably, the preparation method of the MAPbI3 microcrystalline precursor in step 3) includes: dissolving the MAPbI3 microcrystals in γ-valerolactone.

[0024] Preferably, the conditions for the annealing treatment in step 3) include: the time is 30 min and the temperature is 120 °C.

[0025] Preferably, the preparation method of the transparent solution in step 4) includes: dissolving 72.3 mg of spiro-OMeTAD in 1 mL of chlorobenzene, and then adding 17.5 μL of the acetonitrile solution of Li-TFSI and 28 μL of 4-tert-butylpyridine.

[0026] The concentration of Li-TFSI in the acetonitrile solution of Li-TFSI is 520 mg / mL.

[0027] Preferably, the volume ratio of the transparent solution to the area of the perovskite layer in step 4) is 50 μL: 2.5 cm × 2.5 cm.

[0028] The spin-coating time of the transparent solution is 20 s.

[0029] Preferably, the thickness of the Au electrode in step 4) is 80 nm.

[0030] Beneficial effects:

[0031] In terms of process: Compared with the traditional anti-solvent promoted crystallization, the in-situ inverse temperature crystallization method is adopted, and in the subsequent large-scale preparation, the heating substrate scraping method can be used instead, which is suitable for large-scale preparation.

[0032] In terms of effects: Compared with the traditional solvent system DMF:DMSO, GVL has a lower Gutman donor number (Dn), is less likely to coordinate with the Pb 2+ center, resulting in an increase in the Pb-I interaction, a larger colloidal network, and correspondingly larger crystal sizes. The increase in particle size helps reduce grain boundaries and the defect state density of the thin film, thereby promoting the improvement of device performance.

[0033] Dissolve perovskite microcrystals of different masses in GVL and stir for 2 h at room temperature for complete dissolution to prepare a 0.35M–0.95M precursor solution (the concentration of the precursor solution)

[0034] Drop the perovskite precursor solution onto the prepared substrate and spin-coat it at 60 °C and 5000 rpm. Quickly drop 50 μL of anisole antisolvent at 14 s (heating spin-coating process). Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments.

[0036] Figure 1 Is the XRD pattern of the experimental example thin film;

[0037] Figure 2 Are the UV-visible absorption spectra of the comparative example and the experimental example;

[0038] Figure 3 Are the single-carrier test spectra of the comparative example and the experimental example;

[0039] Figure 4 Are the forward and reverse scan J-V curves of the comparative example and the experimental example. Detailed Embodiments

[0040] The present invention provides a method for preparing a highly stable perovskite solar cell by recrystallizing perovskite microcrystals in situ with inverse temperature crystallization, including the following steps:

[0041] 1) Place the FTO conductive glass on a heating substrate and prepare a TiO2 dense layer by spray pyrolysis;

[0042] 2) Spin-coat the mesoporous layer raw material on the obtained TiO2 dense layer and sinter it to prepare a mesoporous TiO2 layer;

[0043] 3) Spin-coat the MAPbI3 microcrystal precursor solution on the obtained mesoporous TiO2 layer and perform annealing treatment to prepare a perovskite layer;

[0044] The concentration of MAPbI3 microcrystals in the MAPbI3 microcrystal precursor solution is 0.75 mmol / mL;

[0045] The spin coating is carried out in two steps. The spin coating speed in the first step is 1000 rpm and the spin coating time is 10 s. The spin coating speed in the second step is 5000 rpm and the spin coating time is 20 s. Anisole of equal volume is added at the 4th second of the spin coating time in the second step;

[0046] 4) Spin coat the transparent solution on the obtained perovskite layer, and then evaporate the Au electrode to obtain a perovskite solar cell.

[0047] In the present invention, the FTO conductive glass is placed on a heating substrate, and a TiO2 dense layer is prepared by spray pyrolysis. In the present invention, the temperature of the heating substrate is preferably 475 °C. In the present invention, the specifications of the FTO conductive glass are preferably: the area is 2.5 cm × 2.5 cm and the thickness is 0.5 cm. The present invention has no special limitation on the source of the FTO conductive glass, and conventional ones can be used. In the present invention, the conditions of the spray pyrolysis preferably include: using an isopropanol solution with a mass percentage of 75% for spray pyrolysis, spraying one circle every 30 s for a total of 30 - 40 min; the preparation method of the 75% isopropanol solution is: adding 515 μL of acetylacetone and 775 μL of diisopropoxybis(acetylacetonate)titanium to 9 mL of isopropanol. The present invention has no special limitation on the material of the heating substrate, and conventional heating instruments can be used. The heating substrate is not in terms of structure.

[0048] In the present invention, the mesoporous layer raw material is spin coated on the obtained TiO2 dense layer and sintered to prepare a mesoporous TiO2 layer. In the present invention, the components of the mesoporous layer raw material are preferably: Dyesol-30NR-D and absolute ethanol, and the mass ratio of Dyesol-30NR-D to absolute ethanol is 1:7; the average particle size of Dyesol-30NR-D is 30 nm; the conditions for spin coating the mesoporous layer raw material include: spin coating at 4000 rpm for 20 s. In the present invention, the sintering conditions preferably include: the temperature is 500 °C and the time is 12 h.

[0049] The MAPbI3 microcrystal precursor solution is spin-coated on the obtained mesoporous TiO2 layer and annealed to prepare a perovskite layer; the concentration of MAPbI3 microcrystals in the MAPbI3 microcrystal precursor solution is 0.75 mmol / mL; the spin-coating is carried out in 2 steps. The spin-coating speed in the first step is 1000 rpm and the spin-coating time is 10 s; the spin-coating speed in the second step is 5000 rpm and the spin-coating time is 20 s. Anisole of equal volume is added at the 4th s of the spin-coating time in the second step. In the present invention, the ratio of the spraying amount of the MAPbI3 microcrystal precursor solution to the area of the mesoporous TiO2 layer is 50 μL: 2.5 cm × 2.5 cm. In the present invention, the preparation method of the MAPbI3 microcrystal precursor preferably includes: dissolving MAPbI3 microcrystals in γ-valerolactone. In the present invention, the conditions of the annealing treatment preferably include: the time is 30 min and the temperature is 120 °C.

[0050] In the present invention, a transparent solution is spin-coated on the obtained perovskite layer, and then an Au electrode is evaporated to obtain a perovskite solar cell. In the present invention, the preparation method of the transparent solution preferably includes: dissolving 72.3 mg of spiro-OMeTAD in 1 mL of chlorobenzene, and then adding 17.5 μL of an acetonitrile solution of Li-TFSI and 28 μL of 4-tert-butylpyridine; the concentration of Li-TFSI in the acetonitrile solution of Li-TFSI is 520 mg / mL. In the present invention, the ratio of the volume of the transparent solution to the area of the perovskite layer is preferably 50 μL: 2.5 cm × 2.5 cm. In the present invention, the spin-coating time of the transparent solution is preferably 20 s. In the present invention, the thickness of the Au electrode is preferably 80 nm.

[0051] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0052] Example 1

[0053] In this example, the perovskite solar cell adopted is a formal mesoporous structure of FTO / c-TiO2 / m-TiO2 / perovskite active layer / Spiro-OMeTAD / Au. The connection relationship is as shown in this structure. First, a cleaned FTO glass substrate, then c-TiO2 and m-TiO2 layers are respectively prepared on the substrate as electron transport layers, then the perovskite active layer, then the hole transport layer (Spiro-OMeTAD) and the gold electrode (Au). Among them, FTO: the glass thickness is 0.5 cm, the c-TiO2 layer (40 - 50 nm), the m-TiO2 layer (200 - 300 nm), the perovskite active layer (500 - 800 nm), the thickness of the Spiro-OMeTAD layer is rarely mentioned, Au (80 nm).

[0054] (1) Preparation of the electron transport layer: Place the FTO glass (with an area of 2.5 cm × 2.5 cm and a thickness of 0.5 cm) on a heated substrate. At a temperature of 475 °C, spray pyrolysis is carried out to prepare the TiO2 dense layer (c-TiO2). Then, spin-coat the mesoporous layer on the obtained c-TiO2 layer and bake it overnight in a muffle furnace (treated at 500 °C for 12 h) to prepare the mesoporous TiO2 layer (m-TiO2), obtaining FTO-c-TiO2-m-TiO2; the substrate is only an instrument for heating.

[0055] The specific method of spray pyrolysis is as follows: Use an isopropanol solution with a mass percentage of 75% for spray pyrolysis, spray one circle every 30 s, for a total of 30 - 40 min;

[0056] The preparation method of the 75% isopropanol solution is as follows: Add 515 μL of acetylacetone and 775 μL of titanium diisopropoxide bis(acetylacetonate) to 9 mL of isopropanol.

[0057] (2) Preparation of the perovskite active layer: Weigh the prepared MAPbX3 microcrystals, dissolve them in GVL to prepare a precursor solution with a concentration of 0.75 mmol / ml, place it in a glove box under a nitrogen atmosphere and stir for 2 h until completely dissolved. Place the FTO-c-TiO2-m-TiO2 on a heated spin coater and heat it at 60 °C for 1 min to fully preheat the FTO-c-TiO2-m-TiO2. Prepare the perovskite thin film through a two-step procedure. Drop 50 μL of the precursor solution on the preheated FTO-c-TiO2-m-TiO2. The spin coating speed in the first step is 1000 rpm, and the spin coating time is 10 s. The spin coating speed in the second step is 5000 rpm, and the spin coating time is 20 s. Add an equal proportion of the antisolvent anisole at the 4th s of the spin coating time in the second step. After the procedure is completed, place the prepared sample on a hot stage at 120 °C and anneal it for 30 min to obtain the perovskite active layer.

[0058] Preparation process: Dissolve MAI and PbI2 in a molar ratio of 1:1 in GVL and add an equal proportion of the antisolvent anisole. After stirring and dissolving, filter and quickly synthesize high-quality MAPbX3 microcrystals at a low temperature of 70 °C within ten minutes;

[0059] (3) Preparation of the Spiro-OMeTAD layer: Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, and then add 17.5 μL of the acetonitrile solution of Li-TFSI (520 mg mL -1) and 28 μL of 4-tert-butylpyridine (TBP), and shake evenly. Take 50 μL of the evenly mixed clear and transparent solution and spin-coat it dynamically onto the perovskite active layer for 20 s; (4) Preparation of Au: Place the film in a high-vacuum coating glove box system, and evaporate an Au electrode with a thickness of 80 nm on the hole transport layer.

[0060] Supplementary comparative experiment: For all the following comparative experiments, except for the different preparation methods of the perovskite active layer, the preparation of other layers is consistent with that of the above experimental examples.

[0061] Effect of different temperatures: Preparation of the perovskite active layer: Weigh the prepared perovskite microcrystals, dissolve them in GVL to prepare a 0.95 M precursor solution, and place it in a glove box under a nitrogen atmosphere and stir for 2 h until completely dissolved. Then place the FTO-c-TiO2-m-TiO2 on a heating spin coater and heat it at 20 °C, 40 °C, 60 °C, and 80 °C for 1 min respectively to fully preheat the FTO-c-TiO2-m-TiO2. Prepare the perovskite film through a two-step procedure. Drop 50 μL of the precursor solution onto the preheated FTO-c-TiO2-m-TiO2. The spin-coating speed in the first step is 1000 rpm, and the spin-coating time is 10 s. The spin-coating speed in the second step is 5000 rpm, and the spin-coating time is 20 s. Add an equal proportion of the antisolvent anisole at the 4th s of the spin-coating time in the second step. After the procedure is completed, place the prepared sample on a hot plate at 120 °C and anneal it for 30 min to obtain the perovskite active layer. The average photoelectric conversion efficiencies of the perovskite solar cells prepared at different temperatures are 5.547%, 8.956%, 11.457%, and 3.395% respectively.

[0062] Effect of different precursor solution concentrations: Preparation of perovskite active layer: Weigh the prepared perovskite microcrystals and dissolve them in GVL to prepare precursor solutions with concentrations of 0.35 M, 0.55 M, 0.75 M, and 0.95 M respectively. Place them in a glove box under a nitrogen atmosphere and stir for 2 h until completely dissolved. Then place FTO-c-TiO2-m-TiO2 on a heated spin coater and heat it at 60 °C for 1 min to fully preheat FTO-c-TiO2-m-TiO2. Prepare the perovskite thin film through a two-step process. Drop 50 μL of the precursor solution on the preheated FTO-c-TiO2-m-TiO2. The spin coating speed in the first step is 1000 rpm and the spin coating time is 10 s. The spin coating speed in the second step is 5000 rpm and the spin coating time is 20 s. Add an equal proportion of the antisolvent anisole at the 4th s during the spin coating time of the second step. After the process is completed, place the prepared sample on a hot plate at 120 °C and anneal it for 30 min to obtain the perovskite active layer. The average photoelectric conversion efficiencies of the perovskite solar cells prepared at different precursor concentrations are 8.851%, 11.018%, 16.994%, and 12.967% respectively. Therefore, it is concluded that the device performance is the best when prepared at 60 °C with a precursor solution concentration of 0.75 M.

[0063] Control

[0064] The preparation of the perovskite active layer adopts: Dissolve the perovskite microcrystals in a mixed solvent of DMF:DMSO (9:1) to prepare a 1.5 M solution, and adopt a two-step process to prepare the perovskite thin film. Take 50 μL of the solution and spin coat it on the substrate, and then add 100 μL of chlorobenzene at the 14th s during the second step. After the process is completed, place the sample on a hot plate at 120 °C and anneal it for 30 min. Other layers are the same as above.

[0065] Results:

[0066] Dissolve the prepared microcrystals in GVL to obtain a precursor solution. Under the condition of 60 °C, high-quality perovskite thin films are prepared by in-situ inverse temperature crystallization. Sharp characteristic peaks appear at 2θ = 14.17° and 28.32°, and this process retains the growth characteristics of the parent perovskite crystals, that is, it tends to preferentially grow on the (110) crystal plane ( Figure 1 ).

[0067] Regarding the UV-vis absorption of the MG thin film, due to the reduction of grain boundaries and the improvement of film quality, MG shows a relatively wide plateau absorption intensity between 300 - 900 nm, which is beneficial to improving the utilization rate of light energy by the battery device ( Figure 2 ).

[0068] The single-hole devices with the structure of ITO / PEDOT:PSS / MAPbI3 / MoO3 / Au were prepared using the MG thin film and the perovskite thin film prepared by the classical method (Control) respectively. The J-V curves of the two single-hole devices were tested under dark conditions by the SCLC method, as Figure 3 shown. The defect filling voltages of the MG thin film and the control group thin film are 1.135 V and 1.771 V respectively, and the corresponding defect state densities are 3.50×1016 cm-3 and 5.47×1016 cm-3 respectively. It shows that the defect state density of the film prepared by in-situ inverse temperature crystallization is lower, and the non-radiative recombination of carriers in the film is less. This is mainly due to the higher crystallization quality of the MG thin film.

[0069] The power conversion efficiency (PCE) of the control group device is 13.93%, V OC is 1.05 V, J SC is 19.10 mA / cm 2 , and the fill factor (FF) is 69.35%. The PCE of the target cell is increased to 17.20%, V OC and J SC are increased to 1.00 V and 23.40 mA / cm 2 respectively, and the FF is 73.03%. Based on the analysis of the above tests, it can be seen that the improvement of V OC and J SC of the MG device is mainly due to the reduction of defect recombination at the interface and the improvement of the film crystallization quality. As Figure 4 shown, the incident photon-to-current conversion efficiency (IPCE) of the two devices and the current values in the J-V test are basically the same. The hysteresis factor (HI) of the MG device is 1.57%, and the HI of the control group device is 2.16%. The reduction of the hysteresis factor is mainly due to the reduction of the internal defect density of the device and the more efficient charge transport efficiency.

[0070] The perovskite solar cell prepared in Example 1: at a high temperature of 80 °C, in a nitrogen environment, the experimental example can maintain 71.7% of the initial efficiency after 300 hours;

[0071] High humidity: After being continuously placed in an air environment with 80%-90% high humidity for 300 hours, the experimental example can still maintain 79.3% of the initial PCE.

[0072] Although the above embodiments have made a detailed description of the present invention, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments according to these embodiments without creative efforts, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A method for preparing a highly stable perovskite solar cell by in-situ inverse temperature crystallization of perovskite microcrystal recrystallization, characterized in that, It includes the following steps: 1) Place the FTO conductive glass on a heating substrate, and prepare a TiO2 dense layer by spray pyrolysis; 2) Spin-coat the mesoporous layer raw material on the obtained TiO2 dense layer and sinter it to prepare a mesoporous TiO2 layer; 3) Spin-coat the MAPbI3 microcrystal precursor solution on the obtained mesoporous TiO2 layer and perform annealing treatment to prepare a perovskite layer; The concentration of MAPbI3 microcrystals in the MAPbI3 microcrystal precursor solution is 0.75 mmol / mL; The spin-coating is carried out in 2 steps. The spin-coating speed in the first step is 1000 rpm and the spin-coating time is 10 s. The spin-coating speed in the second step is 5000 rpm and the spin-coating time is 20 s. Anisole with an equal volume is added at the 4th second of the spin-coating time in the second step; 4) Spin-coat the transparent solution on the obtained perovskite layer, and then evaporate and deposit an Au electrode to obtain a perovskite solar cell.

2. The method according to claim 1, characterized in that The temperature of the heating substrate in step 1) is 475 °C; The specifications of the FTO conductive glass are: the area is 2.5 cm × 2.5 cm and the thickness is 0.5 cm; The conditions for spray pyrolysis include: using an isopropanol solution with a mass percentage of 75% for spray pyrolysis, spraying one circle every 30 s for a total of 30 - 40 min; The preparation method of the 75% isopropanol solution is: add 515 μL of acetylacetone and 775 μL of diisopropoxybis(acetylacetonate)titanium to 9 mL of isopropanol.

3. The method according to claim 1, wherein The components of the mesoporous layer raw material in step 2) are: Dyesol-30NR-D and absolute ethanol, and the mass ratio of Dyesol-30NR-D to absolute ethanol is 1:7; The average particle size of Dyesol-30NR-D is 30 nm; The conditions for spin-coating the mesoporous layer raw material include: spin-coating at 4000 rpm for 20 s.

4. The method according to claim 1, wherein The sintering conditions in step 2) include: the temperature is 500 °C and the time is 12 h.

5. The method according to claim 1, characterized in that, The ratio of the spin-coating amount of the MAPbI3 microcrystal precursor solution to the area of the mesoporous TiO2 layer in step 3) is 50 μL:2.5 cm × 2.5 cm.

6. The method according to claim 1, characterized in that, The preparation method of the MAPbI3 microcrystal precursor in step 3) includes: dissolving MAPbI3 microcrystals in γ-valerolactone.

7. The method according to claim 1, wherein The annealing treatment conditions in step 3) include: the time is 30 min and the temperature is 120 °C.

8. The method according to claim 1, characterized in that The preparation method of the transparent solution in step 4) includes: dissolve 72.3 mg of spiro-OMeTAD in 1 mL of chlorobenzene, and then add 17.5 μL of the acetonitrile solution of Li-TFSI and 28 μL of 4-tert-butylpyridine; The concentration of Li-TFSI in the acetonitrile solution of Li-TFSI is 520 mg / mL.

9. The method according to claim 1, wherein The ratio of the volume of the transparent solution to the area of the perovskite layer in step 4) is 50 μL:2.5 cm × 2.5 cm; The spin-coating time of the transparent solution is 20 s.

10. The method according to claim 1, wherein The thickness of the Au electrode in step 4) is 80 nm.

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