Method for low-cost solution preparation of all-inorganic perovskite thin films

Abstract

This invention discloses a low-cost solution-based method for preparing all-inorganic perovskite thin films. Specifically, the method involves: pretreating an all-inorganic perovskite thin film substrate; preparing a lower charge transport layer on the pretreated substrate; preparing PbX2 and CsX precursor solutions; dropwise adding the PbX2 precursor solution onto the substrate, spin-coating, and annealing to obtain a PbX2 thin film; dropwise adding a CsX solution onto the PbX2 thin film, spin-coating, and annealing to obtain a CsPbX3 thin film; and dropwise adding a CsX precursor solution onto the CsPbX3 thin film, spin-coating, and annealing to obtain a low-defect, dense CsPbX3 thin film. Compared to traditional multi-step spin-coating methods, this invention suppresses phase transitions in the perovskite thin film while maintaining a device efficiency of 9.37%, and reduces the cost of the fabrication process, making the technology more feasible and scalable.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor polycrystalline thin film preparation technology, specifically relating to a low-cost solution method for preparing all-inorganic perovskite thin films. Background Technology

[0002] The high-temperature and high-humidity resistance of all-inorganic perovskite CsPbX3 materials makes them crucial for applications in high-quality solar cells, high-performance light-emitting diodes, high-response photodetectors, and laser devices. However, inherent defects and ion migration in perovskite films can lead to low absorption, high dark current, and poor stability in these devices.

[0003] Chinese Patent (Application No.: 201910173731.9, Publication No.: CN109904322A, Publication Date: 2019-03-08) discloses a method for preparing all-inorganic perovskite thin films. The method involves mixing inorganic perovskite components with organic amine salts to prepare a mixed film, which is then placed in an atmosphere of methylamine, ethylamine, or butylamine gas to repair defects and surface roughness in the perovskite film. Finally, high-temperature annealing is performed to remove any remaining ammonium salt components within the perovskite film. Perovskite films obtained using this method exhibit uniform thickness, low roughness, and good crystallinity. However, a drawback of this method is that gas leakage and poisoning can easily occur when treating the perovskite film with amine gas, which contradicts the initial goal of low-cost, large-area perovskite film preparation.

[0004] In their paper "Phase Control of Cs-Pb-Br Derivatives to Suppress 0D Cs4PbBr6 for High-Efficiency and Stable All-Inorganic CsPbBr3 Perovskite Solar Cells" (Small, 18.8(2022):2106323), Tang Qunwei et al. disclosed a method for preparing high-performance all-inorganic perovskite films via a multi-step spin-coating solution method. This all-inorganic perovskite film is prepared by first spin-coating lead halide (PbX2), followed by multiple reactions with cesium halide (CsX) to generate a high-purity CsPbX3 phase. However, this multi-step spin-coating method requires precise control of the immersion period or number of cycles of the CsX solution to avoid phase transitions (to CsX-rich or PbX2-rich phases), which can easily lead to complex processes and additional costs, contradicting the original intention of preparing large-area, low-cost perovskite films. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost solution method for preparing all-inorganic perovskite thin films, which can suppress the phase transition of perovskite thin films, resulting in perovskite thin films with better uniformity and lower roughness.

[0006] The technical solution adopted in this invention is a low-cost solution method for preparing all-inorganic perovskite thin films, specifically implemented according to the following steps:

[0007] Step 1: Pre-treat the all-inorganic perovskite thin film substrate;

[0008] Step 2: Prepare a lower charge transport layer on the pretreated all-inorganic perovskite thin film substrate;

[0009] Step 3: Prepare PbX2 and CsX precursor solutions;

[0010] Step 4: Spin-coat a PbX2 precursor solution onto the all-inorganic perovskite thin film substrate after Step 2, and anneal to obtain a PbX2 thin film; spin-coat a CsX solution onto the PbX2 thin film, and anneal to obtain a CsPbX3 thin film; spin-coat a CsX precursor solution onto the CsPbX3 thin film, and anneal to obtain a low-defect, dense CsPbX3 thin film.

[0011] The invention is further characterized in that,

[0012] Step 1 specifically involves:

[0013] The all-inorganic perovskite thin film substrate was sequentially immersed in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water for ultrasonic cleaning, purged with nitrogen, and thermally annealed to remove surface moisture. Then, it was placed in an ultraviolet ozone UV-zone for pretreatment to obtain the pretreated all-inorganic perovskite thin film substrate.

[0014] All-inorganic perovskite thin film substrates are made of indium tin oxide (ITO) substrates or fluorine-doped tin oxide (FTO) substrates.

[0015] Ultrasonic cleaning time is 20-30 min, nitrogen purging time is 1-2 min; ultraviolet ozone (UV-zone) treatment time is 20-30 min.

[0016] In step 2, specifically: spin-coat the precursor solution of the lower charge transport layer onto the all-inorganic perovskite thin film substrate, and place it on a hot plate for annealing;

[0017] The lower charge transport layer is either a hole transport layer or an electron transport layer. If the lower charge transport layer is a hole transport layer, its precursor solution is any one of the following: triphenylamine derivative solution, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate PEDOT:PSS solution, poly(3-hexylthiophene)P3HT solution, cuprous thiocyanate solution, or NiO solution. If the lower charge transport layer is an electron transport layer, its precursor solution is any one of the following: TiO2 solution, SnO2 solution, or ZnO solution.

[0018] Step 3 specifically involves:

[0019] PbX2 and DMF were mixed and heated to 75°C in a nitrogen atmosphere, and stirred for 200-500 min to obtain a PbX2 precursor solution.

[0020] CsX and H2O are mixed and heated to 55°C in a nitrogen atmosphere, and stirred for 200-500 min to obtain a CsX solution.

[0021] CsX and CH3OH were mixed and heated to 55°C in a nitrogen atmosphere, and stirred continuously for 200-500 min to obtain a CsX precursor solution.

[0022] The concentration of the CsX precursor solution was 0.005–0.02 mol / L; X was I. - , Br - Cl - Any one of them.

[0023] Step 4 specifically involves:

[0024] PbX2 precursor solution was spin-coated onto the all-inorganic perovskite thin film substrate after step 2 at a speed of 3000-5000 rpm for 30-40 seconds. The spin-coated all-inorganic perovskite thin film substrate was then transferred to a heating stage for annealing at a temperature of 100°C for 30 minutes to obtain a PbX2 thin film.

[0025] CsX solution was spin-coated onto a PbX2 film at a speed of 3000-5000 rpm for 30-40 s; the spin-coated film was then transferred to a heating stage for annealing at a temperature of 250℃ for 5 min; thus obtaining a CsPbX3 film.

[0026] A CsX precursor solution was spin-coated onto a CsPbX3 thin film at a speed of 3000–5000 rpm for 30–40 s. The spin-coated CsPbX3 thin film substrate was then transferred to a heating stage for annealing at a temperature of 250 °C for 5 min, resulting in a low-defect, dense CsPbX3 thin film.

[0027] The thickness of low-defect dense CsPbX3 films is 300-500 nm.

[0028] The beneficial effects of this invention are: compared with the traditional multi-step spin coating method, the method of this invention can suppress the phase transition of the perovskite thin film, while ensuring that the efficiency of the prepared device reaches 9.37%, and reducing the cost of the preparation process, making the technology more feasible and scalable. Attached Figure Description

[0029] Figure 1 Atomic force microscopy image of the surface morphology of CsPbBr3 obtained without conventional passivation treatment;

[0030] Figure 2 An atomic force microscope image of the surface morphology of CsPbBr3 after CsBr passivation by the method of the present invention.

[0031] Figure 3 Scanning electron microscope (SEM) image of the surface morphology of CsPbBr3 obtained without passivation treatment;

[0032] Figure 4 SEM image of the surface morphology of CsPbBr3 after CsBr passivation by the method of the present invention;

[0033] Figure 5 This is a schematic diagram comparing the photoluminescence intensity (PL) of the CsPbBr3 mixed thin film before and after CsBr passivation in an embodiment of the present invention;

[0034] Figure 6 SEM image of the all-inorganic perovskite thin film device prepared in this invention;

[0035] Figure 7 The JV curves are for the devices in Embodiments 1-3 of this invention. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] This invention provides a low-cost solution method for preparing all-inorganic perovskite thin films, which is specifically implemented according to the following steps:

[0038] Step 1: Pre-treat the all-inorganic perovskite thin film substrate, specifically as follows:

[0039] The inorganic perovskite thin film substrate was ultrasonically cleaned by sequentially immersing it in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water. The ultrasonically cleaned inorganic perovskite thin film substrate was then purged with nitrogen and thermally annealed to remove surface moisture. Subsequently, it was placed in an ultraviolet ozone UV-zone for pretreatment to obtain the pretreated inorganic perovskite thin film substrate.

[0040] All-inorganic perovskite thin film substrates are made of indium tin oxide (ITO) substrates or fluorine-doped tin oxide (FTO) substrates.

[0041] The ultrasonic cleaning time is 20-30 minutes, and the nitrogen purging time is 1-2 minutes.

[0042] The UV-zone treatment time is 20-30 minutes;

[0043] Step 2: Prepare a lower charge transport layer on the pretreated all-inorganic perovskite thin film substrate;

[0044] Using a spin coater, the precursor solution of the lower charge transport layer is spin-coated onto an all-inorganic perovskite thin film substrate, and then placed on a hot plate for annealing.

[0045] The lower charge transport layer is either a hole transport layer or an electron transport layer. If the lower charge transport layer is a hole transport layer, its precursor solution can be any one of the following: triphenylamine derivative solution, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate PEDOT:PSS solution, poly(3-hexylthiophene)P3HT solution, cuprous thiocyanate solution, or NiO solution.

[0046] If the lower charge transport layer is an electron transport layer, its precursor solution can be any one of TiO2 solution, SnO2 solution, or ZnO solution;

[0047] Step 3: Prepare PbX2 and CsX precursor solutions;

[0048] PbX2 and DMF are mixed and heated to 75°C in a nitrogen atmosphere. The mixture is stirred for 200-500 min to fully dissolve the PbX2 precursor solution and ensure that air and moisture are completely removed from the solution.

[0049] The concentration of the PbX2 precursor solution was 1 mol / mL;

[0050] CsX and H2O are mixed and heated to 55°C in a nitrogen atmosphere. The mixture is stirred continuously for 200-500 min to ensure complete dissolution and removal of air and moisture from the solution, yielding a CsX solution with a concentration of 1 mol / mL.

[0051] CsX and CH3OH are mixed and heated to 55°C in a nitrogen atmosphere. The mixture is stirred continuously for 200-500 min to fully dissolve the CsX precursor solution and ensure that the air in the mixed solution is completely removed.

[0052] The concentration of the CsX precursor solution was 0.005–0.02 mol / mL;

[0053] X is I- , Br - Cl - Any one of them;

[0054] Step 4: Prepare an all-inorganic perovskite thin film (CsPbX3 thin film) using a two-step spin coating method;

[0055] Specifically, the PbX2 precursor solution is spin-coated onto the all-inorganic perovskite thin film substrate after step 2 at a speed of 3000-5000 rpm for 30-40 seconds; the spin-coated all-inorganic perovskite thin film substrate is transferred to a heating stage for annealing at a temperature of 100°C for 30 minutes to obtain the PbX2 thin film.

[0056] CsX solution was spin-coated onto a PbX2 film at a speed of 3000–5000 rpm for 30–40 s. The spin-coated film was then transferred to a heating stage for annealing at 250 °C for 5 min to obtain a CsPbX3 film.

[0057] A CsX precursor solution was spin-coated onto a CsPbX3 thin film at a speed of 3000–5000 rpm for 30–40 s. The spin-coated CsPbX3 thin film substrate was then transferred to a heating stage for annealing at a temperature of 250 °C for 5 min, resulting in a low-defect, dense CsPbX3 thin film.

[0058] The volume ratio of PbX2 precursor solution, CsX solution, and CsX precursor solution is 1:1:1; the thickness of the final CsPbX3 film is 300-500 nm.

[0059] The phase transition suppression emphasized in this invention is achieved by inhibiting the conversion of CsPbBr3 to Cs4PbBr6, a conclusion theoretically verified. Under CsBr·CH3OH treatment conditions, the reaction barriers for the conversion of CsPb2Br5 to CsPbBr3 and CsPbBr3 to Cs4PbBr6 are both negative, at -4.23 eV and 22.88 eV, respectively. This indicates that under CsBr·CH3OH treatment, the conversion of CsPb2Br5 to CsPbBr3 is favorable, requiring a lower energy barrier, thus promoting the formation of CsPbBr3 while inhibiting the formation of OD Cs4PbBr6. Compared to other treatment conditions, this barrier modulation that favors CsPbBr3 formation helps suppress the transformation of CsPbBr3 to the harmful Cs4PbBr6.

[0060] Example 1:

[0061] The substrate is an indium tin oxide (ITO) substrate, the lower charge transport layer is zinc oxide (ZnO), the perovskite light absorption layer is CsPbBr3, the upper charge transport layer is Spiro-OMeTAD, and the top metal electrode is silver (Ag). The perovskite solar cell is obtained using the preparation method of this invention.

[0062] Pretreatment of perovskite solar cell substrate: The indium tin oxide (ITO) substrate was sequentially immersed in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water for ultrasonic cleaning. The ultrasonic cleaning temperature was 50℃, and the ultrasonic cleaning time for each type of cleaning was 20 minutes.

[0063] The ultrasonically cleaned indium tin oxide (ITO) substrate was subjected to UV-zone treatment for 20 minutes to obtain a pretreated indium tin oxide (ITO) substrate.

[0064] Preparation of the lower charge transport layer for perovskite solar cells: 1 g of zinc acetate dihydrate and 0.28 g of ethanolamine were dissolved in 10 mL of dimethoxyethanol solution and stirred thoroughly at room temperature for 12 hours to obtain a zinc oxide precursor solution. The zinc oxide precursor solution was spin-coated onto a pretreated FTO substrate at 3000 rpm for 45 s, and then annealed at 150 °C for 30 min to obtain the electron transport layer of the perovskite solar cell.

[0065] Fabrication of the perovskite light-absorbing layer for perovskite solar cells: A perovskite precursor solution was prepared, and a CsPbBr3 thin film was prepared using a two-step spin-coating method. A 1M PbBr2+DMF solution was stirred uniformly on a hot stage at 75°C. The prepared PbBr2 solution was spin-coated onto the electron transport layer at 2000 rpm for 30 seconds, followed by hot-stage treatment at 100°C for 30 minutes to obtain the PbBr2 thin film. A 250 mg / mL CsBr+H2O solution was stirred uniformly on a hot stage at 55°C. The prepared CsBr solution was spin-coated onto the PbBr2 thin film at 2000 rpm for 30 seconds, and finally annealed at 250°C for 5 minutes to obtain the CsPbBr3 thin film. After cooling, CsBr methanol solutions of different concentrations were spin-coated onto the CsPbBr3 thin film at 2000 rpm for 30 seconds, and finally annealed at 250°C for 5 minutes to obtain the perovskite light-absorbing layer for the perovskite solar cell.

[0066] Preparation of the upper charge transport layer: 90 mg Spiro-OMeTAD was added to 1 ml of chlorobenzene to obtain a Spiro-OMeTAD solution. The prepared Spiro-OMeTAD solution was spin-coated onto the perovskite absorber layer at a speed of 4000 rpm to obtain the hole transport layer.

[0067] Fabrication of the top metal electrode: under a chamber vacuum condition of 10-5 Below Pa, Ag was deposited at a rate of 100 nm to obtain a metal electrode, thus completing the fabrication of a perovskite solar cell.

[0068] Figures 1-4 This is a schematic diagram comparing the surface morphology of the CsPbBr3 mixed film before and after CsBr passivation in Example 1 of the present invention. As can be seen from the figure, the surface morphology and roughness of the CsPbBr3 film passivated by CsBr+CH3OH are significantly improved. Figure 5 This is a comparison of the photoluminescence intensity spectra of the CsPbBr3 mixed thin film before and after CsBr passivation in Example 1 of the present invention. As can be seen from the figure, the fluorescence intensity of the CsPbBr3 thin film passivated by CsBr+CH3OH increased by a factor of 2. This indicates that the perovskite thin film passivated by CsBr+CH3OH has better crystallinity and a smoother surface, which helps to reduce defects at the perovskite grain boundaries, increase the carrier concentration of the film, and enhance the photoluminescence intensity of the film.

[0069] Example 2

[0070] The substrate is a fluorine-doped tin oxide (FTO) substrate, the lower charge transport layer is titanium dioxide (TiO2), the perovskite light absorption layer is CsPbBr3, the upper charge transport layer is P3HT, and the top metal electrode is gold (Au). The perovskite solar cell is prepared using the method of this invention.

[0071] Pretreatment of perovskite solar cell substrates: Fluorine-doped tin oxide (FTO) substrates were sequentially immersed in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water for ultrasonic cleaning. The ultrasonic cleaning temperature was 50℃, and the ultrasonic cleaning time for each step was 20 minutes. The ultrasonically cleaned fluorine-doped tin oxide (FTO) substrates were then subjected to UV-zone treatment for 30 minutes to obtain pretreated fluorine-doped tin oxide (FTO) substrates.

[0072] Preparation of the lower charge transport layer of perovskite solar cells: First, prepare a titanium dioxide precursor solution. Add 10 mL of titanium tetrabutoxide to 100 mL of deionized water and stir vigorously at room temperature for 30 min to obtain a dehydrated and filtered powder. Add 10 mL of acetic acid and 0.8 mL of nitric acid to the powder and stir at 80 °C for 15 min. Then add 160 mL of deionized water. When the reactant solution becomes translucent, perform hydrothermal treatment at 200 °C for 12 h. Then add 0.4 g of P25 and sonicate for 30 min. Heat at 200 °C for 12 h. Mix the obtained colloid with 0.8 g of polyethylene glycol and 1 mL of OP emulsifier and concentrate at 80 °C to 40 mL to obtain a TiO2 precursor solution.

[0073] A 0.15 mol / L titanium dioxide precursor solution was spin-coated onto an FTO substrate at 4000 rpm for 45 seconds, followed by annealing at 125 °C for 5 minutes. The substrate was then treated twice with a 0.3 mol / L titanium dioxide precursor solution, and the resulting thin film was sintered at 450 °C for 15 minutes. After cooling to room temperature, the coated TiO2 film was immersed in a 40 mmol / L TiCl4 aqueous solution at 70 °C for 45 minutes, and then heat-treated at 450 °C for 15 minutes to obtain the electron transport layer of the perovskite solar cell.

[0074] Fabrication of the perovskite light-absorbing layer for perovskite solar cells: A perovskite precursor solution was prepared, and a CsPbBr3 thin film was prepared using a two-step spin-coating method. A 1M PbBr2+DMF solution was stirred uniformly on a hot stage at 75°C. The prepared PbBr2 solution was spin-coated onto the electron transport layer at 2000 rpm for 30 seconds, followed by hot-stage treatment at 100°C for 30 minutes to obtain the PbBr2 thin film. A 250 mg / mL CsBr+H2O solution was stirred uniformly on a hot stage at 55°C. The prepared CsBr solution was spin-coated onto the PbBr2 thin film at 2000 rpm for 30 seconds, and finally annealed at 250°C for 5 minutes to obtain the CsPbBr3 thin film. After cooling, CsBr methanol solutions of different concentrations were spin-coated onto the CsPbBr3 thin film at 2000 rpm for 30 seconds, and finally annealed at 250°C for 5 minutes to obtain the perovskite light-absorbing layer for the perovskite solar cell.

[0075] Preparation of the upper charge transport layer: 15 mg / mL of P3HT was dissolved in CB and then stirred evenly on a hot plate at 75 °C. The P3HT solution was rotated at 2000 rpm for 30 s and then annealed on a hot plate at 90 °C for 15 minutes to obtain a P3HT layer, which serves as the hole transport layer of the perovskite solar cell.

[0076] Fabrication of the top metal electrode: under a chamber vacuum condition of 10 -5 Below Pa, Au was deposited at a rate of 100 nm to obtain a metal electrode, thus completing the fabrication of a perovskite solar cell.

[0077] Example 3

[0078] The substrate is a fluorine-doped tin oxide (FTO) substrate, the lower charge transport layer is tin dioxide (SnO2), the perovskite light absorption layer is CsPbBr3, the upper charge transport layer is P3HT, and the top metal electrode is carbon C. The perovskite solar cell is obtained using the preparation method of this invention.

[0079] Pretreatment of perovskite solar cell substrates: Fluorine-doped tin oxide (FTO) substrates were sequentially immersed in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water for ultrasonic cleaning. The ultrasonic cleaning temperature was 50℃, and the ultrasonic cleaning time for each step was 20 minutes. The ultrasonically cleaned fluorine-doped tin oxide (FTO) substrates were then subjected to UV-zone treatment for 30 minutes to obtain pretreated fluorine-doped tin oxide (FTO) substrates.

[0080] Preparation of the lower charge transport layer of perovskite solar cells: 1 mL of tin dioxide (15%) was dropped into 2 mL of deionized water to obtain a tin dioxide precursor solution (5%). The tin dioxide precursor solution was spin-coated onto a pretreated FTO substrate at 5000 rpm for 30 s, and then annealed at 150 °C for 30 min to obtain the electron transport layer of the perovskite solar cell.

[0081] Fabrication of the perovskite light-absorbing layer for perovskite solar cells: A perovskite precursor solution was prepared, and a CsPbBr3 thin film was prepared using a two-step spin-coating method. A 1M PbBr2+DMF solution was stirred uniformly on a hot stage at 75°C. The prepared PbBr2 solution was spin-coated onto the electron transport layer at 2000 rpm for 30 s, followed by hot-stage treatment at 100°C for 30 min to obtain the PbBr2 thin film. A 250 mg / mL CsBr+H2O solution was stirred uniformly on a hot stage at 55°C. The prepared CsBr solution was spin-coated onto the PbBr2 thin film at 2000 rpm for 30 seconds, and finally annealed at 250°C for 5 min to obtain the CsPbBr3 thin film. After cooling, CsBr methanol solutions of different concentrations were spin-coated onto the CsPbBr3 thin film at 2000 rpm for 30 s, and finally annealed at 250°C for 5 min to obtain the perovskite light-absorbing layer for the perovskite solar cell.

[0082] Preparation of the upper charge transport layer: 15 mg / mL of P3HT was dissolved in CB and then stirred evenly on a hot plate at 75 °C. The P3HT solution was rotated at 2000 rpm for 30 s and then annealed on a hot plate at 90 °C for 15 minutes to obtain a P3HT layer, which serves as the hole transport layer of the perovskite solar cell.

[0083] Metal electrode for perovskite solar cell fabrication: Carbon electrode is printed onto P3HT thin film using screen printing to obtain metal electrode, thus completing the fabrication of perovskite solar cell.

[0084] Figure 6 The image shows a scanning electron microscope (SEM) image of the FTO / SnO2 / CsPbBr3 / C device in Example 3 of this invention. As can be seen from the image, the thickness of the all-inorganic perovskite thin film prepared by this invention is 351 nm.

[0085] Figure 7 The figures show the JV curves of the FTO / ZnO / CsPbBr3 / Spiro-OMeTAD / Ag, FTO / TiO2 / CsPbBr3 / P3HT / Au, and FTO / SnO2 / CsPbBr3 / C devices in Examples 1-3 of this invention. As can be seen from the figures, the short-circuit current (JV) of the FTO / ZnO / CsPbBr3 / Spiro-OMeTAD / Ag device in Example 1 is... sc The value is 6.44 mA / cm. 2 Open circuit voltage (V) oc The voltage is 1.09V, the fill factor (FF) is 45.53%, and the photoelectric conversion efficiency (Eff) is 3.16%. The short-circuit current (J / L) of the FTO / TiO2 / CsPbBr3 / P3HT / Au device in Example 2 is... sc The value is 7.80 mA / cm. 2 Open circuit voltage (V) oc The voltage is 1.52V, the fill factor (FF) is 79.02%, and the photoelectric conversion efficiency (Eff) is 9.37%. The short-circuit current (J / L) of the FTO / SnO2 / CsPbBr3 / C device in Example 3 is... sc The value is 7.49 mA / cm. 2 Open circuit voltage (V) oc The voltage is 1.34V, the fill factor (FF) is 76.01%, and the photoelectric conversion efficiency (Eff) is 7.63%.

Claims

1. A method for low cost solution processable fabrication of all-inorganic perovskite thin films, characterized in that, The specific steps are as follows: Step 1: Pre-treat the all-inorganic perovskite thin film substrate; Step 2: Prepare a lower charge transport layer on the pretreated all-inorganic perovskite thin film substrate; Specifically, the precursor solution of the lower charge transport layer is spin-coated onto an all-inorganic perovskite thin film substrate and then placed on a hot plate for annealing. The lower charge transport layer is either a hole transport layer or an electron transport layer. If the lower charge transport layer is a hole transport layer, its precursor solution is any one of the following: triphenylamine derivative solution, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate solution, poly(3-hexylthiophene)P3HT solution, cuprous thiocyanate solution, or NiO solution. If the lower charge transport layer is an electron transport layer, its precursor solution is any one of the following: TiO2 solution, SnO2 solution, or ZnO solution. Step 3: Prepare PbX2 and CsX precursor solutions and CsX solutions; Specifically: PbX2 and DMF were mixed and heated to 75°C in a nitrogen atmosphere, and stirred for 200-500 min to obtain a PbX2 precursor solution. CsX and H2O are mixed and heated to 55°C in a nitrogen atmosphere, and stirred for 200-500 min to obtain a CsX solution. CsX and CH3OH were mixed and heated to 55°C under a nitrogen atmosphere, and stirred continuously for 200-500 min to obtain a CsX precursor solution. CsX precursor solution has a concentration of 0.005-0.02 mol / mL; X is any one of I - , Br - , Cl - . Step 4: Spin-coat a PbX2 precursor solution onto the all-inorganic perovskite thin film substrate obtained in Step 2, and anneal to obtain a PbX2 thin film; spin-coat a CsX solution onto the PbX2 thin film, and anneal to obtain a CsPbX3 thin film; spin-coat a CsX precursor solution onto the CsPbX3 thin film, and anneal to obtain a low-defect, dense CsPbX3 thin film; specifically: PbX2 precursor solution was spin-coated onto the all-inorganic perovskite thin film substrate after step 2 at a speed of 3000~5000 rpm for 30-40s; the spin-coated all-inorganic perovskite thin film substrate was transferred to a heating stage for annealing at a temperature of 100℃ for 30min to obtain PbX2 thin film. CsX solution was spin-coated onto a PbX2 film at a speed of 3000-5000 rpm for 30-40 seconds. The spin-coated film was then transferred to a heating stage for annealing at 250℃ for 5 minutes to obtain a CsPbX3 film. A CsX precursor solution was spin-coated onto a CsPbX3 thin film at a speed of 3000-5000 rpm for 30-40 seconds. The spin-coated CsPbX3 thin film substrate was transferred to a heating stage for annealing at a temperature of 250°C for 5 minutes. Low-defect dense CsPbX3 films were obtained; the thickness of the low-defect dense CsPbX3 films was 300-500 nm.

2. The method of claim 1, wherein the low-cost solution process for fabricating all-inorganic perovskite thin films is characterized by, In step 1, specifically: The all-inorganic perovskite thin film substrate was sequentially immersed in Decon-90 cleaning agent, deionized water, acetone, alcohol, and deionized water for ultrasonic cleaning, purged with nitrogen, and thermally annealed to remove surface moisture. Then, it was placed in an ultraviolet ozone UV-zone for pretreatment to obtain the pretreated all-inorganic perovskite thin film substrate.

3. A method of low cost solution processable fabrication of all inorganic perovskite thin films according to claim 2, characterized in that, The all-inorganic perovskite thin film substrate is made of indium tin oxide (ITO) substrate or fluorine-doped tin oxide (FTO) substrate.

4. The method of claim 2, wherein the low-cost solution process for fabricating all-inorganic perovskite thin films is characterized by, The ultrasonic cleaning time is 20-30 min, the nitrogen purging time is 1-2 min, and the ultraviolet ozone (UV-zone) treatment time is 20-30 min.

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