Method for preparing perovskite solar cells by multi-stage vacuum flash evaporation

Abstract

The present application belongs to the technical field of perovskite solar cell preparation, and relates to a method for preparing a perovskite solar cell through multi-stage vacuum flash evaporation, which comprises the following steps: coating a perovskite precursor solution prepared in advance on the surface of a prepared hole transport layer, removing low-boiling-point solvents in the precursor solution through preliminary drying to form a wet film, sequentially performing multi-stage vacuum flash evaporation drying on the wet film to obtain a perovskite light-absorbing layer, preparing an electron transport layer and a metal electrode on the perovskite light-absorbing layer, and completing the preparation of the perovskite solar cell. Through control of temperature and air pressure, the present application can gradually remove solvents and complexing agents in the perovskite thin film in stages, effectively control the nucleation and crystallization rate of the perovskite, form the required penetrating crystal, and obtain a high-quality perovskite thin film, thereby improving the performance of the perovskite solar cell.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell fabrication technology, and specifically relates to a method for preparing perovskite solar cells through multi-stage vacuum flash evaporation. Background Technology

[0002] Perovskite has an ABX3-type cubic octahedral structure. Perovskite thin-film solar cells made from this material have simple processing, low production costs, are stable, and have high conversion efficiency. Since 2009, the photoelectric conversion efficiency has increased from 3.8% to over 26.6%, which is comparable to commercial crystalline silicon solar cells in terms of efficiency and has a significant cost advantage.

[0003] Although the efficiency and stability of perovskite solar cells have been significantly improved, the long-term stability of the materials has not yet reached the standards required for commercial applications, which is related to the high-density defects generated by the low-cost perovskite thin films. Defects in perovskite solar cell materials are key factors leading to nonradiative recombination and energy dissipation, thus limiting the performance and structural stability of the devices. Therefore, to optimize device performance and gradually move towards the Shockley-Queisser theoretical efficiency limit, while improving the long-term stability of solar cells, it is essential to minimize the nonradiative recombination losses and defect concentrations caused by various defects.

[0004] Vacuum flash evaporation is a commonly used method for perovskite film formation in the industry. It lowers the boiling point of the solvent by reducing the gas pressure, causing the solvent to evaporate rapidly. During this process, the boiling point of the substance decreases as the gas pressure decreases. Therefore, by adjusting the gas pressure, the boiling point of the substance can be changed, causing the liquid phase to vaporize rapidly and crystals to precipitate. However, most existing vacuum flash evaporation processes aim to quickly remove the solvent by rapidly reducing the gas pressure and achieve rapid crystallization and nucleation. This is only a one-step process to quickly remove the organic solvent from the perovskite wet film and reduce the influence of the solvent atmosphere. It fails to specifically remove some of the complexing agents in the wet film and lacks control over crystal crystallization during this process. This makes it difficult to control the perovskite grain size and morphology to form high-quality perovskite films. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing perovskite solar cells by multi-stage vacuum flash evaporation. By controlling the temperature and pressure, solvents, complexing agents and other substances in the perovskite film are gradually removed in stages, which can effectively control the nucleation and crystallization rate of perovskite, form the required through crystals, obtain high-quality perovskite films, and thus improve the performance of perovskite solar cells.

[0006] This invention provides a method for preparing perovskite solar cells using multi-stage vacuum flash evaporation. The internal structure of the perovskite solar cell, from bottom to top, includes a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode. The method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer using ultraviolet ozone; Step 2: Prepare a hole transport layer on the surface of the transparent conductive layer; Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the hole transport layer by any one of spin coating, blade coating, or slot coating. After initial drying to remove the low-boiling-point solvent in the precursor solution, a wet film is formed, and the wet film is then subjected to a cooling and freezing treatment. Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuum for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents to obtain a semi-dry film. Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuumed for 0~3min to further remove low complexing capacity or low boiling point complexing agents to obtain a near-dry film. Step Six: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 Pa~100Pa, continuous vacuuming for 0~3min, used to remove complexing agents with high complexing ability or high boiling point to obtain dry film; Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60min to obtain the perovskite light-absorbing layer. Step 8: Prepare an electron transport layer on the perovskite light-absorbing layer; Step nine: Fabricate metal electrodes on the electron transport layer until the fabrication of the perovskite solar cell is complete; among which, The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-ability or low-boiling-point complexing agent, and at least one high-complexing-ability or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-ability or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-pyrrolidone, with a boiling point below 210°C. At least one of the complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

[0007] This invention is implemented as follows, and also provides a method for preparing perovskite solar cells through multi-stage vacuum flash evaporation. The internal structure of the perovskite solar cell, from bottom to top, includes a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode. The method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer using ultraviolet ozone; Step 2: Prepare an electron transport layer on the surface of the transparent conductive layer; Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the electron transport layer by any one of spin coating, blade coating, or slot coating. Perform preliminary drying to remove the low-boiling-point solvent in the precursor solution to form a wet film. Then, perform a cooling and freezing treatment on the wet film. Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuum for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents to obtain a semi-dry film. Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuumed for 0~3min to further remove low complexing capacity or low boiling point complexing agents to obtain a near-dry film. Step 6: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 Pa~100Pa, continuous vacuuming for 0~3min, used to remove complexing agents with high complexing ability or high boiling point to obtain dry film; Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60min to obtain a perovskite light-absorbing layer. Step 8: Prepare a hole transport layer on the perovskite light-absorbing layer; Step 9: Fabricate a metal electrode on the hole transport layer until the fabrication of the perovskite solar cell is complete; wherein, The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-ability or low-boiling-point complexing agent, and at least one high-complexing-ability or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-ability or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-pyrrolidone, with a boiling point below 210°C. At least one of the complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

[0008] Furthermore, the perovskite precursor solution contains perovskite material with the molecular formula ABX3, wherein A is at least one monovalent cation selected from cesium, rubidium, amino, amidine, and base groups; B is at least one divalent metal cation selected from lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, and polonium; and X is at least one anion selected from iodine, bromine, chloride, astatine, thiocyanate, and acetate.

[0009] Furthermore, the hole transport layer is prepared using at least one of the following materials: SAM molecules, PTAA, BTCV polymer, NiOx, V2O5, PEDOT:PSS, CuO, CuI, CuSCN, PVK:TFB film, and Spiro-OMeTAD.

[0010] Furthermore, the electron transport layer is prepared from at least one of fullerene and its derivatives, SnO2, TiO2, ZnO, and ZnO-ZnS.

[0011] Furthermore, the metal electrode is made of any one of silver, copper, gold, aluminum, composite metals, or transparent conductive electrodes.

[0012] Compared with the prior art, the multi-stage vacuum flash evaporation method for preparing perovskite solar cells of the present invention has the following characteristics: (1) The low-temperature -20℃~70℃ multi-stage temperature-controlled vacuum flash evaporation method provided by the present invention can effectively control the removal rate of low complexing capacity or low boiling point complexing agents, greatly prolong the complexing agent removal time, thereby controlling the growth rhythm of perovskite crystals, significantly delaying perovskite crystallization, uniformly nucleating, increasing the grain size, preparing penetrating crystals in air, improving the quality of perovskite crystals, and thus improving the performance of perovskite solar cells.

[0013] (2) One of the problems that is difficult to solve with large-area perovskite films is the rapid drying of film nucleation. Because large-area perovskites have a large area and a large amount of solvent, it is difficult to remove the solvent quickly at the same time, resulting in inconsistent crystallization rates of perovskites and affecting the overall film quality. This invention greatly widens the crystallization window of perovskites by removing the solvent and complexing agent in stages. After the low-boiling-point solvent and low-boiling-point or low-complexing-ability complexing agent in the entire large-area perovskite film are removed, the high-complexing-ability or high-boiling-point complexing agent is removed in an orderly manner to crystallize and nucleate, thus solving the problem of uniform crystallization of large-area perovskite films. Attached Figure Description

[0014] Figure 1 This is a SEM comparison diagram of the cross-section of the perovskite light-absorbing layer film prepared by the multi-stage vacuum flash evaporation method of the present invention and the cross-section of the perovskite light-absorbing layer film prepared by conventional vacuum flash evaporation. Figure 2a and Figure 2b The images show a planar SEM comparison of perovskite mesophase films prepared using the multi-stage vacuum flash evaporation method of this invention and perovskite mesophase films prepared using conventional vacuum flash evaporation. Figure 2c and Figure 2d These are the grain size distribution diagrams for each grain; Figure 3 This is a schematic diagram comparing the IV performance of the perovskite solar cell prepared in Example 3 of the present invention with that of the perovskite solar cell prepared by conventional vacuum flash evaporation. Figure 4 This is a comparison of XRD patterns at different times during the preparation of perovskite light-absorbing thin films using Example 3 of the present invention and conventional vacuum flash evaporation. Figure 5 This is a schematic diagram comparing the XRD patterns of perovskite light-absorbing layer films prepared using the multi-stage vacuum flash evaporation method of this invention with those prepared using conventional vacuum flash evaporation. Detailed Implementation

[0015] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0016] Example 1

[0017] A first embodiment of the multi-stage vacuum flash evaporation method for preparing perovskite solar cells according to the present invention, wherein the internal structure of the perovskite solar cell, from bottom to top, includes a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode, and the method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer using ultraviolet ozone.

[0018] Step 2: Prepare a hole transport layer on the surface of the transparent conductive layer.

[0019] Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the hole transport layer by any of the following methods: spin coating, blade coating, or slot coating. After initial drying to remove the low-boiling-point solvent from the precursor solution, a wet film is formed. The wet film is then subjected to a cooling and freezing treatment to "freeze" or "fix" the current state of the wet film.

[0020] Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 The vacuum is continuously applied at Pa~100Pa for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents, resulting in a semi-dry film.

[0021] Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 The vacuum is continuously pumped at Pa~100Pa for 0~3min to further remove complexing agents with low complexing capacity or low boiling point, resulting in a near-dry film.

[0022] Step Six: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 A vacuum of 100 Pa for 0-3 minutes is used to remove complexing agents with high complexing capacity or high boiling point to obtain a dry film.

[0023] Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60 minutes to obtain the perovskite light-absorbing layer.

[0024] Step 8: Prepare an electron transport layer on the perovskite light-absorbing layer.

[0025] Step 9: Fabricate metal electrodes on the electron transport layer until the fabrication of the perovskite solar cell is complete.

[0026] The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-capacity or low-boiling-point complexing agent, and at least one high-complexing-capacity or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-capacity or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-ethylpyrrolidone, with a boiling point below 210°C. - At least one of the following pyrrolidone complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

[0027] Specifically, the perovskite precursor solution contains perovskite material with the molecular formula ABX3, wherein A is at least one monovalent cation selected from cesium, rubidium, amino, amidine, and base groups; B is at least one divalent metal cation selected from lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, and polonium; and X is at least one anion selected from iodine, bromine, chloride, astatine, thiocyanate, and acetate.

[0028] Specifically, the hole transport layer is prepared using at least one of the following materials: SAM molecules, PTAA, BTCV polymer, NiOx, V2O5, PEDOT:PSS, CuO, CuI, CuSCN, PVK:TFB film, and Spiro-OMeTAD.

[0029] Specifically, the electron transport layer is prepared from at least one of fullerene and its derivatives, SnO2, TiO2, ZnO, and ZnO-ZnS.

[0030] Specifically, the metal electrode is made of any one of silver, copper, gold, aluminum, composite metals, or transparent conductive electrodes.

[0031] Example 2

[0032] A second embodiment of the method for preparing perovskite solar cells using multi-stage vacuum flash evaporation of the present invention, wherein the internal structure of the perovskite solar cell, from bottom to top, includes a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode, and the method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer with ultraviolet ozone.

[0033] Step 2: Prepare an electron transport layer on the surface of the transparent conductive layer.

[0034] Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the electron transport layer by any of the following methods: spin coating, blade coating, or slot coating. After initial drying to remove the low-boiling-point solvent from the precursor solution, a wet film is formed. The wet film is then subjected to a cooling and freezing treatment to "freeze" or "fix" the current state of the wet film.

[0035] Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 The vacuum is continuously applied at Pa~100Pa for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents, resulting in a semi-dry film.

[0036] Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 The vacuum is continuously pumped at Pa~100Pa for 0~3min to further remove complexing agents with low complexing capacity or low boiling point, resulting in a near-dry film.

[0037] Step 6: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 A vacuum of 100 Pa for 0-3 minutes is used to remove complexing agents with high complexing capacity or high boiling point to obtain a dry film.

[0038] Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60min to obtain the perovskite light-absorbing layer.

[0039] Step 8: Prepare a hole transport layer on the perovskite light-absorbing layer.

[0040] Step 9: Fabricate a metal electrode on the hole transport layer until the fabrication of the perovskite solar cell is complete.

[0041] The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-capacity or low-boiling-point complexing agent, and at least one high-complexing-capacity or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-capacity or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-ethylpyrrolidone, with a boiling point below 210°C. - At least one of the following pyrrolidone complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

[0042] Other conditions and requirements are the same as in Example 1, and will not be repeated here.

[0043] The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation according to the present invention is further illustrated below through specific embodiments.

[0044] Example 3

[0045] A third embodiment of the method for preparing perovskite solar cells using multi-stage vacuum flash evaporation of the present invention includes the following steps: Step 11: Clean the 5×5cm FTO conductive glass substrate sequentially with deionized water, acetone, and isopropanol, each for 30 minutes using ultrasonic cleaning. After drying with N2, treat with ultraviolet ozone for 10 minutes.

[0046] Step 12: Prepare NiO on the cleaned FTO conductive glass substrate. x As a hole transport layer.

[0047] Step 13: Preparation of perovskite precursor solution: Dissolve 1 mmol of PbI2, 0.95 mmol of FAI, and 0.05 mmol of CsI in 1 ml of a mixed solvent of N,N-dimethylformamide (DMF):N-methylpyrrolidone (NMP):tetramethylene sulfoxide (TMSO) = 4:1:1 (v / v), heat and stir at 60 °C for 2 h, and set aside for use after complete mixing.

[0048] Step 14: Stepwise drying to obtain a perovskite mesophase film: Take 500 μl of perovskite precursor solution and spin-coat it onto NiO at a speed of 4500 r / min for 30 s. xAfter spin coating, the wet film is pre-cooled to below 0°C. Then, the substrate is placed in a vacuum flash evaporation device with the substrate temperature set to -15°C and the gas pressure set to 10 Pa. After 1 min, DMF and some NMP are removed. Then, the substrate temperature is set to 20°C and the gas pressure is set to 10 Pa. After 2 min, NMP is removed. Finally, the substrate temperature is set to 60°C and the gas pressure is set to 5 Pa. After 3 min, TMSO is removed. The substrate is then taken out to obtain a perovskite mesophase film.

[0049] Step 15: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain the perovskite light-absorbing layer.

[0050] Step 16: Prepare PCBM as an electron transport layer on the perovskite light-absorbing layer.

[0051] Step 17: Deposit Ag onto the electron transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

[0052] Example 4

[0053] A fourth embodiment of the method for preparing perovskite solar cells using multi-stage vacuum flash evaporation of the present invention includes the following steps: Step 21: Clean the 30×40cm FTO conductive glass substrate sequentially with deionized water, acetone and isopropanol, each for 30 minutes using ultrasonic cleaning. After drying with N2, treat with ultraviolet ozone for 10 minutes.

[0054] Step 22: Prepare NiO on the cleaned FTO conductive glass substrate. x As a hole transport layer.

[0055] Step 23: Preparation of perovskite precursor solution: Dissolve 0.1 mol of PbI2, 0.095 mol of FAI, 0.005 mol of CsI, and 0.015 mol of MACl in 100 ml of a mixed solvent of N,N-dimethylformamide (DMF):N-methylpyrrolidone (NMP):1-vinyl-2-pyrrolidone (NVP) = 4:1:0.5 (v / v), heat and stir at 30 °C for 2 h, and set aside for use after complete mixing.

[0056] Step 24: Stepwise drying to obtain a perovskite mesophase film: This film is coated onto NiO through a slit. xA perovskite precursor solution was coated onto the substrate. After spin coating, the wet film was pre-cooled to below 0°C. The substrate was then placed in a vacuum flash evaporator with the substrate temperature set to -15°C and the gas pressure set to 10 Pa. After 1 min, DMF and some NMP were removed. The substrate temperature was then set to 20°C and the gas pressure set to 10 Pa. After 2 min, NMP was removed. Finally, the substrate temperature was set to 70°C and the gas pressure set to 5 Pa. After 3 min, NVP was removed, and the substrate was taken out to obtain a perovskite mesophase film.

[0057] Step 25: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain the perovskite light-absorbing layer.

[0058] Step 26: Prepare C60 and BCP as electron transport layers on the perovskite light-absorbing layer.

[0059] Step 27: Deposit Ag onto the electron transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

[0060] Example 5

[0061] A fifth embodiment of the method for preparing perovskite solar cells using multi-stage vacuum flash evaporation of the present invention includes the following steps: Step 31: Clean the 5×5cm FTO conductive glass substrate sequentially with deionized water, acetone and isopropanol, each for 30 minutes using ultrasonic cleaning. After drying with N2, treat with ultraviolet ozone for 10 minutes.

[0062] Step 32: Prepare TiO2 as an electron transport layer on the cleaned FTO conductive glass substrate.

[0063] Step 33: Preparation of perovskite precursor solution: Dissolve 0.8 mmol of PbI2, 0.2 mmol of PbBr2, 1 mmol of FAI, and 0.1 mmol of MACl in 1 ml of a mixed solvent of DMF:NMP:CHP (N-cyclohexyl-2-pyrrolidone) = 7:2:1 (v / v), stir for 2 h, and set aside for use after complete mixing.

[0064] Step 34: Stepwise drying to obtain perovskite mesophase film: Take 500 μl of perovskite precursor solution and spin-coat it onto the TiO2 layer at a speed of 4500 r / min for 30 s. Immediately after spin-coating, place the substrate in a vacuum flash evaporation device with the substrate temperature set to -5℃ and the gas pressure set to 10 Pa. After 3 min, remove DMF and some NMP. Then, set the substrate temperature to 30℃ and the gas pressure to 5 Pa, and place it for 3 min to further remove NMP. Finally, set the substrate temperature to 70℃ and the gas pressure to 5 Pa, and place it for 3 min to remove CHP. Then take out the substrate to obtain perovskite mesophase film.

[0065] Step 35: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain the perovskite light-absorbing layer.

[0066] Step 36: Prepare Spiro-OMeTAD as a hole transport layer on the perovskite light-absorbing layer.

[0067] Step 37: Deposit Au onto the hole transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

[0068] Please refer to Figure 1 The image shows a microscopic view of the cross-section of a perovskite light-absorbing layer film prepared using the multi-stage vacuum flash evaporation method of this invention, and a microscopic view of the cross-section of a perovskite light-absorbing layer film prepared using conventional vacuum flash evaporation. Figure 1 It can be observed that the perovskite light-absorbing layer film prepared in air by this invention is dense, with large grains, and is a through-crystal; while the perovskite light-absorbing layer film prepared by conventional vacuum flash evaporation has many small fragmented crystals on its surface and is not a through-crystal. Figures 2a-2d It can be seen that, by comparing the grain size of the intermediate phase plane, the grain size of the perovskite light-absorbing layer thin film prepared by multi-stage vacuum flash evaporation is more uniform, while the grain size of the perovskite light-absorbing layer thin film crystal prepared by conventional vacuum flash evaporation is uneven and there are more fragmented grains.

[0069] like Figure 4 The image shows a comparison of XRD patterns at different times during the preparation of perovskite light-absorbing thin films using the method of the present invention (temperature-controlled vacuum flash evaporation) and conventional vacuum flash evaporation. In the conventional vacuum flash evaporation experiment, most of the NMP is removed within 30 seconds; however, in the multi-stage temperature-controlled vacuum flash evaporation, a significant characteristic peak of PbI2-NMP is still visible after 30 seconds, and NMP is gradually removed only within 60 to 120 seconds. The removal time of NMP in the multi-stage temperature-controlled vacuum flash evaporation process is 2 to 3 times that of conventional vacuum flash evaporation. Figure 5As shown, compared with the control group (conventional vacuum flash evaporation), the peak position of the experimental group (multi-stage temperature-controlled vacuum flash evaporation of this invention) shifted to the right by 14.03 from 14.0. According to Bragg's equation, 2dsinθ=nλ, this indicates that after the multi-stage temperature-controlled vacuum flash evaporation treatment of this invention, the d-interval of the perovskite lattice in the experimental group decreased. A smaller lattice spacing may mean a more ordered crystal structure, reduced micro-strain and defects in the crystal, improved crystal quality, and consequently, enhanced photoelectric properties.

[0070] like Figure 3 The diagram shows a comparison of the IV performance of the perovskite solar cell prepared in Example 3 of the present invention (stage-controlled temperature vacuum flash evaporation) with that prepared by conventional vacuum flash evaporation. From... Figure 3 This also confirms Figure 4 The XRD test results show that, compared with perovskite solar cells prepared by conventional vacuum flash evaporation, the perovskite solar cells prepared by multi-stage temperature control in this invention have significantly improved Voc and FF.

[0071] The conventional vacuum flash evaporation method for preparing perovskite solar cells refers to the process of drying the wet perovskite film using an existing one-step vacuum flash evaporation method, as opposed to Example 3 of this invention, while the remaining steps and conditions are the same as in Example 3.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing perovskite solar cells using multi-stage vacuum flash evaporation, wherein the internal structure of the perovskite solar cell, from bottom to top, comprises a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode, characterized in that, The method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer using ultraviolet ozone; Step 2: Prepare a hole transport layer on the surface of the transparent conductive layer; Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the hole transport layer by any one of spin coating, blade coating, or slot coating. After initial drying to remove the low-boiling-point solvent in the precursor solution, a wet film is formed, and the wet film is then subjected to a cooling and freezing treatment. Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuum for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents to obtain a semi-dry film. Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuumed for 0~3min to further remove low complexing capacity or low boiling point complexing agents to obtain a near-dry film. Step Six: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 Pa~100Pa, continuous vacuuming for 0~3min, used to remove complexing agents with high complexing ability or high boiling point to obtain dry film; Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60 min to obtain the perovskite light-absorbing layer. Step 8: Prepare an electron transport layer on the perovskite light-absorbing layer; Step nine: Fabricate metal electrodes on the electron transport layer until the fabrication of the perovskite solar cell is complete; among which, The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-ability or low-boiling-point complexing agent, and at least one high-complexing-ability or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-ability or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-pyrrolidone, with a boiling point below 210°C. At least one of the complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

2. A method for preparing perovskite solar cells through multi-stage vacuum flash evaporation, wherein the internal structure of the perovskite solar cell, from bottom to top, comprises a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode, characterized in that, The method includes the following steps: Step 1: Clean and treat the substrate with the transparent conductive layer using ultraviolet ozone; Step 2: Prepare an electron transport layer on the surface of the transparent conductive layer; Step 3: Apply the pre-prepared perovskite precursor solution to the surface of the electron transport layer by any one of spin coating, blade coating, or slot coating. Perform preliminary drying to remove the low-boiling-point solvent in the precursor solution to form a wet film. Then, perform a cooling and freezing treatment on the wet film. Step 4: Place the substrate containing the wet film into the first section of the vacuum flash evaporation equipment, controlling the substrate temperature range to -20~0℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuum for 0~3min to remove low-boiling-point solvents and some low-complexing-ability or low-boiling-point complexing agents to obtain a semi-dry film. Step 5: Place the substrate containing the semi-dry film into the second section of the vacuum flash evaporator, controlling the substrate temperature range to 0℃~20℃ and the gas pressure to 10. -5 Pa~100Pa, continuously vacuumed for 0~3min to further remove low complexing capacity or low boiling point complexing agents to obtain a near-dry film. Step 6: Place the substrate containing the near-dry film into the third section of the vacuum flash evaporation equipment, controlling the substrate temperature range to 20℃~70℃ and the gas pressure to 10. -5 Pa~100Pa, continuous vacuuming for 0~3min, used to remove complexing agents with high complexing ability or high boiling point to obtain dry film; Step 7: Anneal the substrate containing the dry film at a temperature of 85℃~150℃ for 10~60 min to obtain a perovskite light-absorbing layer. Step 8: Prepare a hole transport layer on the perovskite light-absorbing layer; Step 9: Fabricate a metal electrode on the hole transport layer until the fabrication of the perovskite solar cell is complete; wherein, The perovskite precursor solution comprises a low-boiling-point solvent, a low-complexing-ability or low-boiling-point complexing agent, and at least one high-complexing-ability or high-boiling-point complexing agent. The low-boiling-point solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 2-methoxyethanol, δ-valerolactone, and γ-butyrolactone. The low-complexing-ability or low-boiling-point complexing agent is N-methylpyrrolidone, N-vinylpyrrolidone, or 1-ethyl-2-pyrrolidone, with a boiling point below 210°C. At least one of the complexing agents, wherein the complexing agent with high complexing ability or high boiling point is at least one of the following: N-cyclohexyl-2-pyrrolidone, polyvinylpyrrolidone, N-dodecyl-2-pyrrolidone, dimethyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethyl sulfoxide, tetramethylene sulfoxide, hexamethylphosphoric triamine, dithiocarbamate, and γ-aminobutyric acid complexing agent.

3. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1 or 2, characterized in that, The perovskite precursor solution contains perovskite material with the molecular formula ABX3, wherein A is at least one monovalent cation selected from cesium, rubidium, amino, amidine, and base groups; B is at least one divalent metal cation selected from lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, and polonium; and X is at least one anion selected from iodine, bromine, chloride, astatine, thiocyanate, and acetate.

4. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1 or 2, characterized in that, The hole transport layer is prepared from at least one of the following materials: SAM molecules, PTAA, BTCV polymer, NiOx, V2O5, PEDOT:PSS, CuO, CuI, CuSCN, PVK:TFB film, and Spiro-OMeTAD.

5. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1 or 2, characterized in that, The electron transport layer is prepared from at least one of fullerene and its derivatives, SnO2, TiO2, ZnO, and ZnO-ZnS.

6. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1 or 2, characterized in that, The metal electrode is made of any one of the following materials: silver, copper, gold, aluminum, composite metals, or transparent conductive electrodes.

7. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1, characterized in that, Includes the following steps: Step 11: Clean the 5×5cm FTO conductive glass substrate sequentially with deionized water, acetone and isopropanol for 30 minutes each, then dry it with N2 and treat it with ultraviolet ozone for 10 minutes. Step 12: Prepare NiO on the cleaned FTO conductive glass substrate. x As a hole transport layer; Step 13: Preparation of perovskite precursor solution: Dissolve 1 mmol of PbI2, 0.95 mmol of FAI, and 0.05 mmol of CsI in 1 ml of a mixed solvent of N,N-dimethylformamide (DMF):N-methylpyrrolidone (NMP):tetramethylene sulfoxide (TMSO) = 4:1:1 (v / v), heat and stir at 60 °C for 2 h, and set aside for use after complete mixing; Step 14: Stepwise drying to obtain a perovskite mesophase film: Take 500 μl of perovskite precursor solution and spin-coat it onto NiO at a speed of 4500 r / min for 30 s. x After spin coating, the wet film is pre-cooled to below 0°C. Then, the substrate is placed in a vacuum flash evaporation equipment with the substrate temperature set to -15°C and the gas pressure set to 10Pa. After 1 minute, DMF and some NMP are removed. Then, the substrate temperature is set to 20°C and the gas pressure is set to 10Pa. After 2 minutes, NMP is removed. Finally, the substrate temperature is set to 60°C and the gas pressure is set to 5Pa. After 3 minutes, TMSO is removed. The substrate is then taken out to obtain a perovskite mesophase film. Step 15: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain a perovskite light-absorbing layer. Step 16: Fabricate PCBM as an electron transport layer on the perovskite light-absorbing layer; Step 17: Deposit Ag onto the electron transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

8. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 1, characterized in that, Includes the following steps: Step 21: Clean the 30×40cm FTO conductive glass substrate sequentially with deionized water, acetone and isopropanol for 30 minutes each, then dry it with N2 and treat it with ultraviolet ozone for 10 minutes. Step 22: Prepare NiO on the cleaned FTO conductive glass substrate. x As a hole transport layer; Step 23: Preparation of perovskite precursor solution: Dissolve 0.1 mol PbI2, 0.095 mol FAI, 0.005 mol CsI, and 0.015 mol MACl in 100 ml of a mixed solvent of N,N-dimethylformamide (DMF):N-methylpyrrolidone (NMP):1-vinyl-2-pyrrolidone (NVP) = 4:1:0.5 (v / v), heat and stir at 30 °C for 2 h, and set aside for use after complete mixing; Step 24: Stepwise drying to obtain a perovskite mesophase film: This film is coated onto NiO through a slit. x A perovskite precursor solution was coated onto the substrate. After spin coating, the wet film was pre-cooled to below 0°C. The substrate was then placed in a vacuum flash evaporation apparatus with the substrate temperature set to -15°C and the gas pressure set to 10 Pa. After 1 min, DMF and some NMP were removed. Then, the substrate temperature was set to 20°C and the gas pressure set to 10 Pa. After 2 min, NMP was removed. Finally, the substrate temperature was set to 70°C and the gas pressure set to 5 Pa. After 3 min, NVP was removed. The substrate was then removed to obtain a perovskite mesophase film. Step 25: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain a perovskite light-absorbing layer. Step 26: Prepare C60 and BCP as electron transport layers on the perovskite light-absorbing layer; Step 27: Deposit Ag onto the electron transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

9. The method for preparing perovskite solar cells by multi-stage vacuum flash evaporation as described in claim 2, characterized in that, Includes the following steps: Step 31: Clean the 5×5cm FTO conductive glass substrate sequentially with deionized water, acetone and isopropanol, each for 30 minutes using ultrasonic cleaning. After drying with N2, treat with ultraviolet ozone for 10 minutes. Step 32: Prepare TiO2 as an electron transport layer on the cleaned FTO conductive glass substrate; Step 33: Preparation of perovskite precursor solution: Dissolve 0.8 mmol of PbI2, 0.2 mmol of PbBr2, 1 mmol of FAI, and 0.1 mmol of MACl in 1 ml of a mixed solvent of DMF:NMP:CHP (N-cyclohexyl-2-pyrrolidone) = 7:2:1 (v / v), stir for 2 h, and set aside for use after complete mixing; Step 34: Stepwise drying to obtain perovskite mesophase film: Take 500 μl of perovskite precursor solution and spin-coat it onto TiO2 layer at a speed of 4500 r / min for 30 s. Immediately after spin-coating, place the substrate in a vacuum flash evaporation device with the substrate temperature set to -5℃ and the gas pressure set to 10 Pa. After 3 min, remove DMF and some NMP. Then set the substrate temperature to 30℃ and the gas pressure to 5 Pa. After 3 min, further remove NMP. Finally, set the substrate temperature to 70℃ and the gas pressure to 5 Pa. After 3 min, remove CHP and take out the substrate to obtain perovskite mesophase film. Step 35: Anneal the perovskite mesophase film at a temperature of 85℃~150℃ for 10~60 min to obtain a perovskite light-absorbing layer. Step 36: Prepare Spiro-OMeTAD as a hole transport layer on the perovskite light-absorbing layer; Step 37: Deposit Au onto the hole transport layer to obtain a metal electrode, until the fabrication of the perovskite solar cell is complete.

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