Preparation method of CsxFA1-xPbI3 thin film capable of inhibiting deprotonation to realize high crystallization and solar cell

Abstract

The invention discloses a preparation method of a CsxFA1-xPbI3 thin film capable of inhibiting deprotonation to realize high crystallization and a solar cell. (S)-piperazine-2-carboxylic acid dihydrochloride is adopted as an additive and dissolved in a perovskite precursor solution, and the high-quality CsxFA1-xPbI3 perovskite thin film is prepared. C-NH-C functional groups in (S)-piperazine-2-carboxylic acid dihydrochloride are utilized to prevent methylamine formed after deprotonation of methyl ammonium chloride in a solution from reacting with formamidine iodide, and mismatch of A-site cation stoichiometric ratio caused by deficiency of organic salt in perovskite is reduced, so that the CsxFA1-xPbI3 perovskite thin film with high crystallinity is realized. And meanwhile, growth of crystal grains and reduction of crystal boundaries between crystals are facilitated. Through the modification of the (S)-piperazine-2-carboxylic acid dihydrochloride, the photoelectric conversion efficiency of the CsxFA1-xPbI3 perovskite solar cell is increased to 25.17% from 22.61%, and is increased by about 11.32%.

Description

Technical Field

[0001] This invention relates to the field of novel thin-film solar cell fabrication technology, and particularly to a highly crystalline Cs... x FA 1-x The preparation method of PbI3 perovskite thin films and their solar cells specifically refers to the one-step preparation of CsI3 perovskite films with suppressed deprotonation and high crystallinity by using (S)-piperazine-2-carboxylic acid dihydrochloride as an additive and adjusting the content of (S)-piperazine-2-carboxylic acid dihydrochloride in the perovskite precursor solution. x FA 1-x PbI3 thin films and their high-efficiency perovskite solar cells. Background Technology

[0002] In the current era, my country's economy is developing rapidly, with a large demand for energy and a tight energy supply. Energy is the material foundation for human society's survival and development and holds a particularly important strategic position in the national economy. Therefore, the development of new energy sources is imminent. Continuously usable and renewable energy sources such as wind, hydro, and solar energy have attracted much attention. Among them, solar energy has the characteristics of wide range, high energy density, safety, and no pollution, making it the most promising type. Therefore, photovoltaic devices that can convert solar energy into electricity are an important strategy for human society to cope with the energy crisis and seek sustainable development.

[0003] Since the initial discovery of the potential of perovskite solar cells in the 1990s, Swiss scientist Michael Grätzel developed a dye-sensitized solar cell (DSSC) based on a perovskite structure and successfully realized the principle of efficient light energy conversion. In the decades that followed, we have achieved continuous improvement in the efficiency and stability of perovskite solar cells by using inorganic perovskite materials or inorganic-organic hybrid perovskite materials instead of dyes. In particular, the development has been rapid in the last decade. During this period, the photoelectric conversion efficiency of perovskite solar cells has increased from the initial 3.8% to more than 26%. Compared with the first-generation silicon-based solar cells and the second-generation thin-film solar cells, perovskite solar cells have become the representative of the third-generation solar cells due to their advantages such as high performance, high conversion efficiency, low manufacturing cost, good flexibility and plasticity for fabricating flexible devices, and rapid response to low light conditions.

[0004] In traditional FAPbI3 perovskite films, due to FA +The large ionic radius and high rotational mobility of Cs ions result in dynamic disorder within the octahedral framework, making it difficult to achieve a stable lattice structure and prone to forming numerous defects, leading to poor stability and consequently low device efficiency and instability. While the introduction of Cs ions can stabilize the structure, it inevitably increases the band gap, sacrificing the original band gap advantage of FAPbI3. This results in poor thermal stability, unfavorable phase separation and carrier trap states, and poor crystallinity. Furthermore, the introduction of methylammonium chloride leads to the reaction of methylamine, which, after deprotonation, reacts with formamidinium iodide, reducing the loss of organic salts in the perovskite and causing a mismatch in the cation stoichiometry at the A-site. Therefore, developing methods to address these issues is crucial. Summary of the Invention

[0005] In this field, due to the unsatisfactory crystallization of perovskites and the poor quality of thin films, the present invention designs and prepares (S)-piperazine-2-carboxylic acid dihydrochloride, which can effectively prevent the reaction between methylamine formed after the deprotonation of methylamine chloride in solution and formamidinium iodide, improve the crystallization performance of perovskite thin films, effectively passivate the interface defects on the surface of the thin film crystals, optimize the energy level arrangement of the perovskite interface, promote carrier transport, and thus improve the optoelectronic properties of nip structure perovskite devices.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: the fabrication of a perovskite solar cell device.

[0007] Step 1: Clean the FTO glass sequentially using glass cleaner, ultrapure water, isopropanol, ultrapure water, and ethanol. After drying with a nitrogen spray gun, perform plasma irradiation on the FTO substrate to clean the surface and increase its wettability for spin coating of the electron layer. Step 2: Mix the tin dioxide aqueous solution stock solution with deionized water at a volume ratio of 1:4 under magnetic stirring for half an hour until homogeneous. Then, spin coat the homogeneous solution onto the substrate from Step 1 at a speed of 4000 rpm. After spin coating, anneal at 150°C for 30 minutes to obtain the tin dioxide electron transport layer. Step 3: Prepare Cs in a glove box. x FA 1-x PbI3 solution, heat and stir until completely dissolved; Step 4, add (S)-piperazine-2-carboxylic acid dihydrochloride to the Cs solution prepared in Step 3. x FA 1-xIn the PbI3 solution, stir until the reaction is complete; Step 5, spin-coat the perovskite precursor solution with additives prepared in Step 4 in two steps: first spin-coat at 1000 rpm for 10 seconds, and second spin-coat at 4000 rpm for 30 seconds, while adding a certain amount of chlorobenzene solution dropwise using a pipette during the 10-second spin-coating of the second step. After spin-coating, anneal in air on a 150°C heating stage for 15 minutes to obtain a perovskite film; Step 6, spin-coat PEAI onto the surface of the generated perovskite film at a spin-coating speed of 4000 rpm to form a passivation layer on the surface of the perovskite film; Step 7, spin-coat Spiro-OMeTAD solution onto the PEAI passivation layer surface from Step 6 at a spin-coating speed of 5000 rpm to form a hole transport layer; Step 8, after spin-coating the hole transport layer, deposit an 80 nm gold electrode on its surface by thermal evaporation under high vacuum to complete the device fabrication. During the evaporation process, the first 10 nm thick Au layer is slowly evaporated at a rate of 0.1 Å / s to reduce damage to the hole transport layer. The initial vacuum degree of evaporation is 5 × 10⁻⁴ Pa, thus forming a complete perovskite solar cell device.

[0008] The perovskite solar cell has a structure of FTO glass / SnO2 electron transport layer / Cs. x FA 1-x PbI3+(S)-piperazine-2-carboxylic acid dihydrochloride perovskite light absorption layer / Spiro-OMeTAD hole transport layer / Au electrode.

[0009] As can be seen from the above technical solution, the Cs provided by the present invention x FA 1-x The difference between the preparation method of PbI3 perovskite thin film and its solar cell and the prior art is that: (1) In this invention, (S)-piperazine-2-carboxylic acid dihydrochloride is introduced into the perovskite thin film as an additive. The C─NH─C functional group in (S)-piperazine-2-carboxylic acid dihydrochloride prevents the reaction between methylamine formed after the deprotonation of methylamine chloride in the solution and formamidinium iodine, thereby reducing the loss of organic salts in the perovskite and the resulting mismatch of the cation stoichiometry at the A site, and thus achieving high crystallinity of Cs x FA 1-x The PbI3 perovskite film has a crystallinity as high as 58,000; it is also conducive to grain growth and reduction of grain boundaries between crystals. (2) The perovskite film prepared by this invention can be directly used to construct perovskite solar cells. Devices based on this perovskite film can obtain perovskite solar cell devices with high photoelectric conversion efficiency and stability. The Cs prepared by this invention x FA 1-x The efficiency of PbI3 perovskite solar cells was significantly improved compared to Cs solar cells without any additives. x FA1-x Compared with PbI3 perovskite solar cells, its highest photoelectric conversion efficiency increased from 22.61% to 25.17%, an increase of about 11.32%. (3) The method of the present invention is simple, easy to implement, low in cost, and suitable for widespread use. Attached Figure Description

[0010] Figure 1 Scanning electron microscope images of the surfaces of perovskite films without (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. a) and perovskite films with (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. b) (at optimal concentration).

[0011] Figure 2 Cross-sectional scanning electron microscope images of perovskite films without (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. a) and with (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. b) (at optimal concentration).

[0012] Figure 3 Atomic force microscopy images of perovskite films without (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. a) and perovskite films with (S)-piperazine-2-carboxylic acid dihydrochloride (Fig. b) (at optimal concentration), and the resulting surface roughness.

[0013] Figure 4 X-ray diffraction patterns of (S)-piperazine-2-carboxylic acid dihydrochloride perovskite films without (S)-piperazine-2-carboxylic acid dihydrochloride and (S)-piperazine-2-carboxylic acid dihydrochloride perovskite films (at optimal concentration).

[0014] Figure 5 The 1H NMR spectra of perovskite films without (S)-piperazine-2-carboxylic acid dihydrochloride (Figures a and b) and with (S)-piperazine-2-carboxylic acid dihydrochloride (Figures c and d) (at optimal concentrations).

[0015] Figure 6 The JVM curves for each instance are shown. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments.

[0017] Example 1: Step 1, ultrasonically clean the FTO glass for 25-30 minutes in the following order: glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the wettability of the substrate. Step 2, dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until well mixed, then add the diluted solution... The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 0 mol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at a speed of 1000 rpm for 10 seconds, and then spin-coat at a speed of 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0018] Example 2: Step 1: Following the order of glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol, ultrasonically clean the FTO glass for 25-30 minutes. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the wettability of the substrate. Step 2: Dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until thoroughly mixed. Then, add the diluted solution... The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 2 mmol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at 1000 rpm for 10 seconds, and then spin-coat at 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0019] Experimental Example 3: Step 1: Following the order of glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol, ultrasonically clean the FTO glass for 25-30 minutes. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the wettability of the substrate. Step 2: Dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until thoroughly mixed. The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 4 mmol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at 1000 rpm for 10 seconds, and then spin-coat at 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0020] Example 4: Step 1: Following the order of glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol, ultrasonically clean the FTO glass for 25-30 minutes. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the substrate's wettability. Step 2: Dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until thoroughly mixed. Then, add the diluted solution... The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 6 mmol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at 1000 rpm for 10 seconds, and then spin-coat at 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0021] Example 5: Step 1: Following the order of glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol, ultrasonically clean the FTO glass for 25-30 minutes. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the wettability of the substrate. Step 2: Dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until thoroughly mixed. The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 8 mmol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at 1000 rpm for 10 seconds, and then spin-coat at 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0022] Experimental Example 6: Step 1: Following the order of glass cleaner, ultrapure water, isopropanol, ultrapure water, and anhydrous ethanol, ultrasonically clean the FTO glass for 25-30 minutes. After drying with a nitrogen gun, irradiate the substrate with plasma for 5-10 minutes to clean the surface and increase the wettability of the substrate. Step 2: Dilute a 15wt% tin dioxide aqueous solution with deionized water (tin dioxide aqueous solution to deionized water at a volume ratio of 1:4). Stir for 30 minutes until thoroughly mixed. The dissolved tin dioxide aqueous solution was spin-coated onto FTO at a spin-coating speed of 4000 rpm for 30 seconds, and then annealed at 150°C for 30 minutes to form a tin dioxide electron transport layer on the FTO. In step 3, in a glove box, a certain proportion of lead iodide, methylammonium chloride, FAI, and CsI were dissolved in a mixed solution of N,N-dimethylformamide / dimethyl sulfoxide (volume ratio 9:1), and stirred with a magnetic stirrer until completely dissolved to prepare a 1M CsI solution. x FA 1-x PbI3 solution; Step 4, in Cs x FA 1-x Add 10 mmol of (S)-piperazine-2-carboxylic acid dihydrochloride to the PbI3 solution and continue stirring until the reaction is complete. Prepare 230-240 μL of chlorobenzene solution in a pipette. After completion, spin-coat the former solution onto the surface of the tin dioxide electron transport layer at 1000 rpm for 10 seconds, and then spin-coat at 4000 rpm for 30 seconds. During this 10-second spin-coating step, drop the prepared chlorobenzene solution onto the surface (the entire process should be continuous and the drop rate should be uniform). Anneal at 150°C for 10-15 minutes to form Cs. x FA 1-x PbI3 perovskite film; Step 5, in Cs x FA 1-x Step 6: Spin-coating a PEAI solution (2.5 mg dissolved in 1 mL of isopropanol) onto a PbI3 film at a spin speed of 4000 rpm for 30 seconds to form a passivation layer on the perovskite film surface. Step 7: Spin-coating a Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL of chlorobenzene, 29 μL of 4-tert-pyridine, and 17 μL of 520 mg / mL lithium bis(trifluoromethanesulfonyl)imide / acetonitrile solution) onto the PEAI film at a spin speed of 5000 rpm for 30 seconds to form a Spiro-OMeTAD hole transport layer on the PEAI surface. Step 8: After spin-coating the hole transport layer, depositing an 80 nm gold electrode onto the hole transport layer using thermal evaporation under high vacuum to complete the device fabrication.

[0023] Figure 1 and Figure 2These are scanning electron microscope images of the surface and cross-section of the perovskite films prepared in Experimental Examples 1 and 2. It can be seen that Cs using (S)-piperazine-2-carboxylic acid dihydrochloride as an additive... x FA 1-x The PbI3 perovskite thin film exhibits a more regular crystal arrangement and a significant reduction in grain boundaries.

[0024] Figure 3 The images shown are atomic force microscopy images of the perovskite films prepared in Experimental Examples 1 and 2. It can be seen that the addition of (S)-piperazine-2-carboxylic acid dihydrochloride results in a smoother surface, significantly reduced surface roughness, and significantly improved film quality.

[0025] Figure 4 The perovskite thin films prepared in Experimental Examples 1 and 2 x X-ray diffraction pattern. (From...) Figure 4 It can be seen that Cs with (S)-piperazine-2-carboxylic acid dihydrochloride as an additive x FA 1-x The crystallinity of the (110) and (220) planes of the PbI3 perovskite film was significantly improved. The strength of the (110) plane of the added perovskite film reached 58,000, while the strength of the (110) plane of the unadded perovskite film was only 7,000. The half-width at half maximum (WHM) of the (110) plane decreased from 0.07538 to 0.07003, and the WHM of the (220) plane decreased from 0.11868 to 0.11848, proving that a highly crystalline perovskite film was obtained.

[0026] Figure 5 The 1H NMR spectra obtained in Experimental Examples 1 and 2, with the addition of (S)-piperazine-2-carboxylic acid dihydrochloride, show that they represent MFA. + The disappearance of these substances fully demonstrates that the reaction between methylamine formed after the deprotonation of methylamine chloride in solution and formamidinium iodide is prevented, thus reducing the loss of organic salts in the perovskite and causing a mismatch in the stoichiometric ratio of cations at the A-site, thereby achieving highly crystallizable Cs. x FA 1-x PbI3 perovskite thin films.

Claims

1. Inhibiting deprotonation to achieve high crystalline Cs x FA 1-x A method for preparing a PbI3 thin film and a solar cell, characterized in that: To Cs x FA 1-x (S)-Piperazine-2-carboxylic acid bis-hydrochloride is added to PbI3 precursor solution, x = 0~0.99, and Cs x FA 1-x PbI3 perovskite precursor solution is coated on the electron transport layer, and then annealed to obtain Cs x FA 1-x PbI3 perovskite film, the concentration of (S)-piperazine-2-carboxylic acid bis-hydrochloride is 1~10 mmol.

2. The solar cell of claim 1, wherein: The C─NH─C functional group in (S)-piperazine-2-carboxylic acid bis-hydrochloride salt is used to prevent the methylamine formed after the deprotonation of methylamine chloride in the solution from reacting with formamidine iodine, thereby reducing the loss of organic salt in the perovskite, causing the stoichiometric ratio mismatch of the A-site cation, and further realizing high crystallinity of Cs x FA 1-x PbI3perovskite thin film, which is conducive to the growth of crystal grains and the reduction of grain boundaries between crystals.

Images