A double-layer electron transport layer, a perovskite solar cell, a preparation method thereof, and an application thereof

Abstract

The present invention relates to a double-layer electron transport layer and its application in perovskite solar cells, belonging to the field of optoelectronic materials and devices. The invention utilizes atomic layer deposition (ALD) technology and traditional nano-aqueous solution spin-coating technology to prepare an electron transport layer with a double-layer structure on an FTO conductive substrate. Subsequently, a two-step method is adopted, using MAFa ionic liquid as a solvent, and a uniform and dense perovskite film is obtained after annealing treatment. Then, the film is subjected to subsequent treatment, and Spiro-OMeTAD is spin-coated as a hole transport layer. A MoO3 modification layer and a metal electrode are deposited by vacuum evaporation technology to complete the preparation of the device. This method reduces the loss of leakage current and can obtain a film with better crystallinity. The prepared FAPbI3 perovskite solar cell has excellent photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention relates to a double - layer electron - transport layer and its application in perovskite solar cells, in particular to a simple method for preparing a perovskite solar cell device that can produce a flat and dense perovskite film, has a low density of defect states, reduces device leakage current, and has a high photoelectric conversion efficiency, belonging to the technical field of optoelectronic materials and devices. Background Art

[0002] With the progress and development of society, the environmental problems faced by human society are becoming increasingly severe. Therefore, research on finding alternatives to traditional fossil fuels has been widely carried out. As a clean energy source that is inexhaustible and renewable, solar energy is considered to be one of the clean energy sources that can gradually replace fossil fuels. As one of the main ways to utilize solar energy, solar cells have attracted much attention. Currently, the widely commercialized solar cells are single - crystal and polycrystalline silicon solar cells. However, the production and processing of crystalline silicon solar cells involve high energy consumption. Therefore, under the current concept of sustainable development, it is difficult to have further development.

[0003] Perovskite solar cells have attracted much attention internationally due to their characteristics such as low cost, simple preparation, and excellent photoelectric conversion performance. Therefore, compared with the existing mature crystalline silicon solar cell technology, they have great advantages, which also bring an optimistic prospect for the commercial application of perovskite solar cells. The power conversion efficiency of perovskite solar cells has increased from 3.8% to 25.6% in the past decade. The structure of perovskite solar cells is usually based on mesoporous TiO2 as the electron - transport layer (ETL), which requires a high temperature above 400 °C to burn off the organic components in the precursor slurry, limiting the actual application range. Therefore, low - temperature - treated ETLs are very important and have made rapid progress, such as SnO2, BaSO3, ZnO. Among them, the ETL of SnO2 is widely used and is one of the most effective ETLs in perovskite solar cells. SnO2 has a high electron mobility, resulting in reduced charge accumulation at the interface between the ETL and perovskite, thus suppressing the hysteresis phenomenon.

[0004] Despite these beneficial characteristics, solution - processed SnO2 still has some disadvantages. First, whether the energy levels between the perovskite and the ETL are aligned has a great impact on the device voltage. In addition, there are many hydroxyl groups on the surface of metal oxides, which can lead to non - radiative recombination at the interface between both the perovskite and the ETL. Finally, some inevitable cluster phenomena in the SnO2 solution have a great impact on the generation of device leakage current. Therefore, reasonably managing the energy levels and defects and reducing the leakage current are crucial for improving the performance of PSCs. Therefore, it is particularly important to use a modified electron - transport layer to solve the existing problems. Summary of the Invention

[0005] The technical problem solved by the present invention is that due to the energy level matching problem in the traditional spin coating method of SnO2 aqueous solution, the turn-on voltage is relatively low. A large number of hydroxyl groups on the surface cause non-radiative recombination at the interface between perovskite and ETL, and the leakage current is too large due to clusters. The double-layer electron transport layer structure prepared by the present invention well adjusts the energy level of the electron transport layer, reducing the energy level gap with perovskite by about 0.56 eV, and preparing a FAPbI3 perovskite solar cell with good turn-on voltage (the turn-on voltage is increased by 0.05 V) and excellent power conversion efficiency (PCE reaches 23.43%).

[0006] To solve the above problems, the technical solution proposed by the present invention is: a method for preparing an efficient formamidinium perovskite solar cell by designing a double-layer electron transport layer to make up for the deficiencies of the traditional single-layer electron transport layer spin coating, including the following steps:

[0007] (1) Dissolve 1.5 M lead iodide in the formamidinium methylammonium ionic liquid MAFa solvent to prepare the precursor solution for the first step. Mix 0.5 M formamidinium iodide with an appropriate amount of methylammonium iodide and methylammonium chloride, and dissolve them in the isopropyl alcohol IPA solvent to prepare the precursor solution for the second step. Stir at 60 °C for 6 - 8 h;

[0008] (2) Place the cleaned and treated fluorine-doped tin oxide conductive glass sheet FTO into the atomic layer deposition ALD deposition system. Pass nitrogen gas at 50 sccm, set the lower chamber temperature at 100 °C, the upper chamber temperature at 110 °C, the source temperature at 60 °C, and set the pipeline temperature at 80 °C. Preheat the whole process for 15 min; Set the deposition thickness for 30 cycles, and start depositing the electron transport layer using the water source and tin source pipelines respectively. After deposition, cool naturally to room temperature. The whole process should avoid vibration and dust;

[0009] (3) Place the deposited FTO in the air. Without post-treatment operations such as ultraviolet irradiation, the second electron transport layer can be directly prepared on its surface by spin coating; The electron transport layer on the surface of the ALD deposition layer in step (3) is SnO2. Specifically: Take an aqueous solution of tin dioxide for spin coating. The volume ratio of the tin dioxide stock solution to deionized water is 1:5. After mixing, perform ultrasonic treatment for a period of time. Finally, take 40 μL and drop it on the surface of the deposition layer for spin coating. The spin coating conditions are 4000 r s -1 Spin coat for 30 s; After spin coating, anneal on a hot plate at 150 °C for 30 min;

[0010] (4) Spin coat the prepared lead iodide solution in the air on the FTO conductive substrate with the electron transport layer, and anneal at 150 °C for 5 min to obtain a vertically oriented lead iodide thin film;

[0011] (5) Spin-coat the formamidinium iodide solution on the lead iodide layer and anneal it at 160 °C for 5 min to obtain a flat and dense perovskite thin film;

[0012] (6) Use phenethylamine iodide salt to modify the interface on the perovskite layer;

[0013] (7) Spin-coat the hole transport layer;

[0014] (8) Vacuum deposit the modification layer and the metal electrode on the hole transport layer.

[0015] Preferably, a double-layer tin oxide electron transport layer structure prepared by an ALD deposition system and a spin-coating method.

[0016] Preferably, in step (4), the prepared lead iodide solution is spin-coated on the FTO conductive substrate with an electron transport layer in air. The specific steps are as follows:

[0017] (1) Preheat the substrate at 100 - 120 °C for 1 - 5 min.

[0018] (2) The spin-coating condition is 5000 r s -1 Spin-coat for 30 s.

[0019] Preferably, in step (5), the formamidinium iodide solution is spin-coated on the lead iodide layer. The specific steps are as follows:

[0020] (1) Preheat the substrate at 40 - 60 °C for 1 - 2 min.

[0021] (2) The spin-coating condition is a rotation speed of 4500 r s -1 Spin-coat for 25 s.

[0022] Preferably, in step (6), phenethylamine iodide salt is used to modify the interface on the perovskite layer. The spin-coating condition is a rotation speed of 5000 r s -1 Spin-coat for 30 s.

[0023] Preferably, the spin-coated hole transport layer in step (7) is Spiro-OMeTAD. The specific steps are as follows:

[0024] (1) Dissolve 73.2 mg of Spiro-OMeTAD in 1 mL of chlorobenzene;

[0025] (2) Dissolve 520 mg of lithium bis(trifluoromethanesulfonyl)imide in 1 mL of acetonitrile solution.

[0026] (3) Add 28.8 μL of the TBP solution to the Spiro-OMeTAD solution;

[0027] (4) Add 17.6 μL of the lithium salt solution to the Spiro-OMeTAD solution;

[0028] (5) Stir the mixed solution at room temperature for 2 h;

[0029] (6) The spin-coating conditions are a rotation speed of 2500 r s -1 Spin-coat for 30 s.

[0030] Preferably, in step (8), the vacuum-evaporated modification layer is MoO3, and the metal electrode is Ag. The specific steps are as follows:

[0031] (1) Deposit MoO3 on the hole transport layer with a thickness of 5 nm;

[0032] (2) The thickness of the metal Ag electrode is 100 nm.

[0033] To solve the above problems, another technical solution proposed by the present invention is: a method for preparing a highly efficient ionic liquid formamidinium perovskite thin film and its perovskite solar cell by modifying the structure of the tin oxide electron transport layer.

[0034] To solve the above problems, another technical solution proposed by the present invention is: a method for preparing a highly efficient ionic liquid formamidinium perovskite thin film and its perovskite solar cell by modifying the structure of the tin oxide electron transport layer, and the application of the prepared perovskite solar cell in the field of optoelectronics.

[0035] Advantages of the present invention:

[0036] (1) In the traditional solution-processed SnO2 electron transport layer studied previously, whether the energy levels between the perovskite and the ETL are aligned has a great impact on the device voltage. To a certain extent, it limits the open-circuit voltage of the device. However, the double-layer electron transport layer structure prepared in the present invention well adjusts the energy levels of the electron transport layer, reducing the energy level difference with the perovskite by about 0.56 eV, and preparing a FAPbI3 perovskite solar cell with good open-circuit voltage (the open-circuit voltage is increased by 0.05 V) and excellent energy conversion efficiency (PCE reaches 23.43%).

[0037] (2) In the traditional solution method, there are many hydroxyl groups on the surface of the metal oxide, which will cause non-radiative recombination at the interface between the perovskite and the ETL, affecting the carrier transport. The double-layer electron transport layer structure prepared in the present invention reduces the non-radiative recombination at the interface by affecting crystal growth, greatly improving the carrier transport.

[0038] (3) Traditional SnO2 solutions are affected by temperature and time, resulting in some inevitable clustering phenomena, which lead to uneven spin-coated films, affecting flatness and having a great impact on the generation of device leakage current. The double-layer electron transport layer structure prepared in the present invention can provide a bottom modification and protection effect, greatly reducing the overall leakage current loss of the device.

[0039] (4) Due to the change in the structure of the tin oxide electron transport layer of this double-layer structure as the substrate itself, it affects the change in crystal growth on the upper surface, resulting in the residual methylamine in the solvent in the first step during the film preparation process being able to volatilize better in the form of gas, thereby ultimately promoting the high crystallinity of lead iodide, improving crystal quality, and optimizing device performance.

[0040] (5) When using ALD to deposit the electron transport layer with a thickness of 10 cycles, the overly thin lower-layer electron transport layer film is not dense enough, which instead affects the overall performance. The energy conversion efficiency of the perovskite solar cell prepared is 22.97%. When using ALD to deposit the electron transport layer with a thickness of 50 cycles, due to the increase in the overall thickness of the double-layer electron transport layer, the internal resistance becomes larger, and the fill factor of the device is slightly affected. The energy conversion efficiency of the perovskite solar cell prepared is 21.74%. When using other thicknesses of ALD to deposit the electron transport layer, the energy conversion efficiency of the perovskite solar cells prepared is less than that of the 30-cycle thickness.

[0041] (6) Without changing the deposition thickness of the ALD layer, using a higher concentration of spin-coated solution (volume ratio 1:4) will significantly decrease the device fill factor and the film quality. Using a lower concentration of spin-coated solution (volume ratio 1:6) will decrease the transport efficiency and significantly decrease the open voltage of the device. The energy conversion efficiency of the perovskite solar cells prepared is less than that of the spin-coated solution with a volume ratio of 1:5. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described below with reference to the accompanying drawings.

[0043] Figure 1 It is the UPS diagram of the tin oxide thin film of the traditional single-layer spin-coated tin oxide electron transport layer in Example 1 of the present invention.

[0044] Figure 2 It is the UPS diagram of the tin oxide thin film of the double-layer tin oxide electron transport layer prepared by using the ALD deposition technology in Example 2 of the present invention.

[0045] Figure 3 It is the TRPL diagram of the traditional single-layer spin-coated tin oxide electron transport layer in Example 1 and the double-layer tin oxide electron transport layer and perovskite layer prepared by using the ALD deposition technology in Example 2 of the present invention.

[0046] Figure 4 It is the dark current diagram of the traditional single-layer spin-coated tin oxide electron transport layer in Example 1 and the double-layer tin oxide electron transport layer prepared by ALD deposition technology and the perovskite layer in Example 2 of the present invention.

[0047] Figure 5 It is the XRD diagram of the lead iodide layer prepared with the traditional single-layer spin-coated tin oxide electron transport layer in Example 1 of the present invention.

[0048] Figure 6 It is the XRD diagram of the lead iodide layer prepared with the double-layer tin oxide electron transport layer prepared by ALD deposition technology in Example 2 of the present invention.

[0049] Figure 7 It is the J-V curve diagram of the perovskite solar cell devices prepared in Example 1 and Example 2 of the present invention.

[0050] Figure 8 It is a schematic diagram of the double electron transport layer and its perovskite solar cell of the present invention. Detailed implementation manners

[0051] Example 1

[0052] In this example, a tin oxide single-layer electron transport layer is used as the electron transport layer of FAPbI3 perovskite to prepare the FAPbI3 perovskite thin film and its perovskite solar cell. For better understanding, the humidity condition in the laboratory of the present invention is greater than 70%. It mainly includes the following steps:

[0053] Step 1) The etched FTO conductive glass is ultrasonically treated in ethanol, ultrapure water plus cleaning agent, ultrapure water, and ethanol for 15 minutes each. After drying with nitrogen, it is placed in an oven at 100 °C for 30 minutes to obtain a clean FTO substrate.

[0054] Step 2) Weigh 691.5 mg of lead iodide, dissolve it in 1 mL of formamidinium formate (MAFa) solvent, and stir at 60 °C for 8 hours until completely dissolved to prepare a lead iodide solution.

[0055] Step 3) Dissolve 73.2 mg of Spiro-OMeTAD in 1 mL of chlorobenzene; dissolve 520 mg of lithium bis(trifluoromethanesulfonyl)imide in 1 mL of acetonitrile solution; add 28.8 μL of TBP solution to the Spiro-OMeTAD solution, and add 17.6 μL of the lithium salt solution to the Spiro-OMeTAD solution; stir the mixed solution at room temperature for 2 hours; the spin-coating condition is a rotation speed of 2500 rs -1 Spin-coat for 30 s;

[0056] Step 4) Dissolve 90 mg of iodomethylformamidine, 9 mg of chloromethylamine, and 6.8 mg of iodomethylamine in 1 mL of isopropanol solution; stir the solution at room temperature for 3 h at 300 r s -1 rotation speed to prepare an iodomethylformamidine solution;

[0057] Step 5) Treat the cleaned FTO substrate in step 1) with ultraviolet ozone for 15 min.

[0058] Step 6) Take 40 μL of the electron transport material SnO2 and drop it onto the FTO substrate treated in step 5), and use a spin coater to spin coat a film at a rotation speed of 4000 r s -1 Spin coat for 30 s, and then anneal the FTO spin coated with SnO2 at 150 °C for 30 min.

[0059] Step 7) Take 60 μL of the lead iodide solution prepared in step 2 and drop it onto the FTO substrate in step 6), spin coat a film, and then anneal to form a lead iodide thin film. Preheat at 110 °C for 2 min before spin coating, and the rotation speed of spin coating the lead iodide solution is 5000 r s -1 Spin coat for 30 s, and anneal in humid air at 150 °C for 5 min.

[0060] Step 8) Spin coat the iodomethylformamidine solution in step 4 onto the lead iodide thin film in step 7. Preheat at 60 °C for 1 min before spin coating, and use 4500 r s when spin coating the solution -1 Spin coat for 30 s. Anneal at 170 °C for 5 min in humid air.

[0061] Step 9) Spin coat the hole transport material in step 3 onto the perovskite thin film in step 8. Use 2500 r s for spin coating Spiro-OMeTAD -1 Spin coat for 30 s to form a hole transport layer.

[0062] Step 10) Adopt vacuum evaporation technology to evaporate 5 nm of MoO3 on the hole transport layer in step 9, and then evaporate 100 nm of metal electrode Ag to obtain a perovskite solar cell.

[0063] Step 11) Under standard test conditions (AM1.5 G illumination), the optimal cell device prepared in this example has an energy conversion efficiency of 22.51%, an open circuit voltage of 1.109 V, and a short circuit current of 25.22 mA / cm 2 , and the fill factor is 80.49%;

[0064] Example 2

[0065] This embodiment is about using a double-layer tin oxide electron transport layer as the electron transport layer of FAPbI3 perovskite to prepare an FAPbI3 perovskite thin film with low defect state density and excellent crystallinity by regulating the thickness of the ALD deposition layer, and its perovskite solar cell. For a full understanding, the humidity condition in the laboratory of the present invention is greater than 70%. The main steps are as follows:

[0066] Step 1) Ultrasonic the etched FTO conductive glass in ethanol, ultrapure water with cleaning agent, ultrapure water, and ethanol for 15 minutes each. After drying with nitrogen, place it in an oven at 100 °C for 30 minutes to obtain a clean FTO substrate.

[0067] Step 2) Weigh 691.5 mg of lead iodide and dissolve it in 1 mL of formamidinium formate (MAFa) solvent, and stir at 60 °C for 8 hours until completely dissolved to prepare a lead iodide solution.

[0068] Step 3) Dissolve 73.2 mg of Spiro-OMeTAD in 1 mL of chlorobenzene; dissolve 520 mg of lithium bis(trifluoromethanesulfonyl)imide in 1 mL of acetonitrile solution; add 28.8 μL of TBP solution to the Spiro-OMeTAD solution, and add 17.6 μL of the lithium salt solution to the Spiro-OMeTAD solution; stir the mixed solution at room temperature for 2 hours; the spin-coating condition is 2500 r s -1 Spin-coat for 30 s;

[0069] Step 4) Dissolve 90 mg of iodomethylformamidinium, 9 mg of chloromethylamine, and 6.8 mg of iodomethylamine in 1 mL of isopropanol solution; stir the solution at a speed of 300 r s -1 at room temperature for 3 hours to prepare an iodomethylformamidinium solution;

[0070] Step 5) Treat the cleaned FTO substrate in step 1) with ultraviolet ozone for 15 minutes.

[0071] Step 6) Place the FTO substrate treated in step 5) into the ALD deposition system, introduce nitrogen gas at a flow rate of 50 sccm, set the chamber temperature to 100 °C, and preheat the tin source temperature to 60 °C for 15 minutes. Deposit the electron transport layer with a thickness of 30 cycles;

[0072] Step 7) Take 40 μL of the electron transport material SnO2 and drop it onto the single-layer electron transport layer in step 6), and use a spin coater to spin-coat into a film at a speed of 4000 r s -1 Spin-coat for 30 s, and then anneal the FTO spin-coated with SnO2 at 150 °C for 30 minutes.

[0073] Step 8) Take 60 μL of the lead iodide solution prepared in Step 2 and drop it onto the FTO substrate in Step 7), spin-coat to form a film, and then perform annealing to form a lead iodide thin film. Preheat at 110 °C for 2 min before spin-coating, and the rotation speed of spin-coating the lead iodide solution is 5000 rs -1 Spin-coat for 30 s and anneal at 150 °C for 5 min in humid air.

[0074] Step 9) Spin-coat the formamidinium iodide solution in Step 4 onto the lead iodide thin film in Step 8). Preheat at 60 °C for 1 min before spin-coating, and use a rotation speed of 4500 rs when spin-coating the solution -1 Spin-coat for 30 s. Anneal at 170 °C for 5 min in humid air.

[0075] Step 10) Spin-coat the hole transport material in Step 3 onto the perovskite thin film in Step 9). Use a rotation speed of 2500 rs for spin-coating Spiro-OMeTAD -1 Spin-coat for 30 s to form a hole transport layer.

[0076] Step 11) Use vacuum evaporation technology to evaporate 5 nm of MoO3 on the hole transport layer in Step 10), and then evaporate 100 nm of metal electrode Ag. Thus, a perovskite solar cell is fabricated.

[0077] Step 12) Under standard test conditions (AM1.5 G illumination), the energy conversion efficiency of the optimal battery device prepared in this example is 23.43%, the open-circuit voltage is 1.145 V, and the short-circuit current is 25.42 mA / cm 2 , and the fill factor is 80.47%;

[0078] Due to the change in the electron transport layer structure, the surface energy level arrangement on the upper surface of the tin oxide electron transport layer is changed. Combining (Appendix Figure 1 with Appendix Figure 2 ), it makes it more conducive to the outward migration of carriers, and to a certain extent, accelerates the transport rate. Combining (Appendix Figure 3 ). Without the structure of the lower ALD deposition layer, the overall film is more rough, which will increase the loss of leakage current (Appendix Figure 4 ), and at the same time, the rough surface is not conducive to the vertical height growth of the lead iodide layer, affecting the volatilization of the ionic liquid solvent and resulting in the residue of the MA component (Appendix Figure 5 , Appendix Figure 6 ), ultimately affecting the overall open-circuit voltage loss, fill factor, and photoelectric conversion efficiency during this period (Appendix Figure 7 ).

[0079] Comparative Example 1

[0080] The electron transport layer was deposited by ALD with a thickness of 10 cycles. The overly thin lower electron transport layer film was not dense enough, which instead affected the overall performance. The energy conversion efficiency of the perovskite solar cell prepared was 22.97%. When the electron transport layer was deposited by ALD with a thickness of 50 cycles, due to the increase in the overall thickness of the double-layer electron transport layer, the internal resistance increased, and the fill factor of the device was slightly affected. The energy conversion efficiency of the perovskite solar cell prepared was 21.74%. When using other thicknesses of ALD-deposited electron transport layers, the energy conversion efficiency of the perovskite solar cells prepared was less than that of the 30-cycle thickness.

[0081] Comparative Example 2

[0082] Without changing the deposition thickness of the ALD layer, using a higher concentration of the spin-coating solution (volume ratio 1:4) would significantly decrease the fill of the device and the film quality would deteriorate. Using a lower concentration of the spin-coating solution (volume ratio 1:6) would decrease the transport efficiency and significantly decrease the open voltage of the device. The energy conversion efficiency of the perovskite solar cells prepared was less than that of the spin-coating solution with a volume ratio of 1:5.

[0083] Generally speaking, the present invention is based on a double-layer electron transport layer of tin oxide as the electron transport layer of FAPbI3 perovskite. By regulating the thickness of the ALD deposition layer, a FAPbI3 perovskite film with a low defect state density and excellent crystallinity and its perovskite solar cell are prepared. The prepared electron transport layer structure has more matched energy levels, reduces non-radiative recombination, greatly promotes the spatial transport of carriers, and the prepared perovskite device has excellent device efficiency. The method for preparing the FAPbI3 perovskite solar cell by this method is simple in operation, has a relatively high photoelectric conversion efficiency, can be prepared in a high-humidity air environment, and has rare industrialization advantages.

[0084] The present invention is not limited to the specific technical solutions described in the above embodiments. Any technical solutions formed by equivalent substitution are within the protection scope required by the present invention.

Claims

1. A dual electron transport layer and a preparation method thereof for a perovskite solar cell, characterized in that, Step (1): The etched FTO conductive glass was ultrasonically treated in ethanol, ultrapure water plus cleaning agent, ultrapure water, and ethanol for 15 min each; after drying with nitrogen, it was placed in an oven at 100 °C for 30 min to obtain a clean FTO substrate; Step (2): Weigh 691.5 mg of lead iodide, dissolve it in 1 mL of formamidine formate solvent, and stir at 60 °C for 8 h until completely dissolved to prepare a lead iodide solution; Step (3): Dissolve 73.2 mg of Spiro-OMeTAD in 1 mL of chlorobenzene to form a Spiro-OMeTAD solution; dissolve 520 mg of lithium bis(trifluoromethanesulfonyl)imide in 1 mL of acetonitrile solution to form a lithium salt solution; add 28.8 μL of TBP solution to the Spiro-OMeTAD solution, and add 17.6 μL of lithium salt solution to the Spiro-OMeTAD solution; stir the mixed solution at room temperature for 2 h; the spin coating conditions are 2500 r·s -1 Spin coat for 30 s; Step (4) Dissolve 90 mg of iodomethylformamidine, 9 mg of chloromethylamine, and 6.8 mg of iodomethylamine in 1 mL of isopropanol solution; stir the solution at 300 r·s -1 rotation speed at room temperature for 3 h to prepare an iodomethylformamidine solution; Step (5): The cleaned FTO substrate in step (1) was treated with ultraviolet ozone for 15 min; Step (6): The FTO substrate treated in step (5) was placed into an ALD deposition system, and a nitrogen gas flow of 50 sccm was introduced. The chamber temperature was set at 100 °C, and the tin source temperature was preheated at 60 °C for 15 min; the electron transport layer was deposited with a thickness of 30 cycles; Step (7): Drop 40 μL of the electron transport material SnO2 onto the single-layer electron transport layer in step (6), and spin-coat it into a film using a spin coater at a rotation speed of 4000 r·s -1 Spin-coat for 30 s, and then anneal the FTO substrate spin-coated with SnO2 at 150 °C for 30 min; Step (8): Take 60 μL of the lead iodide solution prepared in step (2) and drop it onto the FTO substrate in step (7), spin-coat to form a film, and then perform annealing to form a lead iodide thin film; preheat at 110 °C for 2 min before spin-coating, and the rotation speed of spin-coating the lead iodide solution is 5000 r·s -1 Spin-coat for 30 s and anneal at 150 °C for 5 min in humid air; Step (9) spin-coats the formamidinium iodide solution in step (4) onto the lead iodide film in step (8). Preheat it for 1 min at 60 °C before spin-coating, and use a rotation speed of 4500 r·s -1 during spin-coating for 30 s; anneal it at 170 °C for 5 min in humid air; Step (10) spin-coats the hole transport material from step (3) onto the perovskite film from step (9). The Spiro-OMeTAD is spin-coated at a rotational speed of 2500 r·s -1 for 30 s to form a hole transport layer; Step (11): Using vacuum evaporation technology, 5 nm of MoO3 was evaporated on the hole transport layer in step (10), and then 100 nm of metal electrode Ag was evaporated. Thus, the perovskite solar cell was fabricated; In step (12), under AM1.5 G illumination at standard test conditions, the prepared battery device has an energy conversion efficiency of 23.43%, an open-circuit voltage of 1.145 V, and a short-circuit current of 25.42 mA / cm 2 , and a fill factor of 80.47%.

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