Method for preparing perovskite solar cell by passivating surface of pure-phase two-dimensional perovskite

Abstract

The invention discloses a method for preparing a perovskite solar cell by passivating the surface of pure-phase two-dimensional perovskite, and belongs to the technical field of perovskite solar cells. The method comprises the following steps: synthesizing a pure-phase two-dimensional material by using an amine / ammonium compound, dissolving the pure-phase two-dimensional material in an organic solution, dynamically spin-coating the pure-phase two-dimensional material on the surface of three-dimensional perovskite, and annealing to form a pure-phase two-dimensional perovskite passivation layer. The pure-phase two-dimensional perovskite passivation layer with a wide band gap is applied to the top of the three-dimensional perovskite, so that energy level alignment between the perovskite layer and the charge transport layer can be improved, and electrons are effectively prevented from penetrating through the perovskite and a hole transport layer interface; meanwhile, the pure-phase two-dimensional perovskite passivation layer can effectively passivate surface defects of the three-dimensional perovskite thin film; the two-dimensional material has good hydrophobicity, degradation of the perovskite material caused by moisture can be reduced, and the long-term stability of the device can be improved. According to the method, the photovoltaic performance of the cell can be effectively improved, and the efficient and stable perovskite solar cell is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite solar cells, and relates to a modification method of perovskite and a preparation method of perovskite solar cells. Background Art

[0002] Facing the global energy crisis and the urgent need for environmental protection, perovskite solar cells (PSCs) have attracted wide attention due to their high efficiency, low cost, and environmental friendliness, and have become one of the key technologies to achieve the goal. However, due to the existence of non-radiative recombination, its current PCE is still far lower than the theoretical limit. At the same time, the stability of PSCs under various environmental conditions still cannot meet the commercial use standards. Research shows that the defects existing on the surface and inside of perovskite are important reasons for the non-radiative recombination of carriers, which will lead to a decrease in the open-circuit voltage ( V oc ) and fill factor (FF) of the device, thereby affecting the battery efficiency.

[0003] Due to the diversity of defect types, it is of great significance to study various passivators to modify the defects of perovskite films, reduce non-radiative recombination, and improve the extraction and transport efficiency of charge carriers. In recent years, the method of using pure-phase two-dimensional perovskite as a surface modification material has gradually attracted the attention of researchers. At present, the classic research method for passivating pure-phase two-dimensional perovskite is to spin-coat organic ammonium salt cations on the surface of three-dimensional perovskite to form a heterogeneous two-dimensional phase or an ultrathin wide-bandgap two-dimensional layer. However, this in-situ growth method of two-dimensional perovskite cannot accurately control the phase purity, film thickness, crystal orientation, etc. of the two-dimensional phase, which has certain limitations on its application. Summary of the Invention

[0004] Based on the above analysis, the present invention proposes a method for preparing perovskite solar cells by passivating the surface of pure-phase two-dimensional perovskite. Using the preparation method of the present invention to construct a two-dimensional / three-dimensional perovskite heterostructure can improve the surface hydrophobicity, passivate the defects on the surface and grain boundaries, inhibit non-radiative recombination, and effectively improve the optoelectronic performance of perovskite solar cells.

[0005] The technical solution adopted by the present invention is as follows: A method for preparing perovskite solar cells by passivating the surface of pure-phase two-dimensional perovskite, the structure of the perovskite solar cell from bottom to top includes: a transparent conductive substrate, an electron transport layer, a three-dimensional perovskite photoactive layer, a pure-phase two-dimensional perovskite passivation layer, a hole transport layer, and a metal electrode.

[0006] The transparent conductive substrate is an indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) conductive glass substrate; The electron transport layer is one or more of tin dioxide and titanium dioxide.

[0007] The composition of the three-dimensional perovskite light-absorbing layer is Cs x (FA, MA) 1-x PbI 3-y Br y One of them, where FA is formamidinium cation CH(NH2)2 + , MA is methylammonium cation CH3NH3 + , 0 ≤ x <0.1, 0 ≤ y <0.6.

[0008] The pure-phase two-dimensional perovskite passivation layer is prepared by dynamically spin-coating and annealing a pure-phase two-dimensional perovskite solution prepared from an amine / ammonium compound; the concentration of the pure-phase two-dimensional solution is 0.5 - 20 mg mL -1 , and the general structural formula of the amine / ammonium compound is:

[0009] Wherein: R1, R2, R3, R4, and R5 are each any one of hydrogen, an alkyl chain, a hydroxyl group, an alkoxy group, a dimethylamino group, a mercapto group, a halogen atom, a nitro group, a cyano group, a phenyl group, and a naphthyl group; n is an integer from 1 to 12.

[0010] The hole transport layer is prepared from a solution of 2,2',7,7'-tetrakis N , N -bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD).

[0011] The metal electrode is one of gold or silver.

[0012] The preparation method of the perovskite solar cell based on the surface passivation of pure-phase two-dimensional perovskite is as follows: (1) Ultrasonically clean and dry the transparent conductive substrate with different solvents.

[0013] (2) On the basis of step (1), prepare the electron transport layer by chemical bath deposition or thermal spraying method.

[0014] (3) After the substrate with the deposited electron transport layer is treated by plasma cleaning, deposit the three-dimensional perovskite light-absorbing layer.

[0015] (4) Prepare the pure-phase two-dimensional perovskite passivation layer by the pure-phase two-dimensional perovskite solution method.

[0016] (5) On the basis of step (4), spin-coat the hole transport layer solution to prepare the hole transport layer.

[0017] (6) The metal electrode is prepared by depositing gold or silver on the device surface of the hole transport layer using vacuum evaporation, obtaining a perovskite solar cell prepared based on the passivation of pure-phase two-dimensional perovskite.

[0018] In the step (3), the specific steps for depositing the three-dimensional perovskite light absorption layer are as follows: depositing the perovskite precursor solution on the substrate by spin coating and performing annealing treatment (annealing at 50 - 120 °C for 10 - 120 min) to prepare the three-dimensional perovskite layer.

[0019] The preparation method of the perovskite precursor solution is to dissolve lead iodide PbI2, formamidinium iodide FAI, lead bromide PbBr2, methylammonium bromide MABr, and cesium iodide CsI with a specific molar ratio in a solvent (PbI2: FAI: PbBr2: MABr: CsI = 1 - 1.5: 1 - 1.5: 0 - 0.5: 0 - 0.5: 0 - 0.1), and stir at room temperature or 60 °C. The solvent is N , N N,N-dimethylformamide (DMF) and N , N N,N-dimethyl sulfoxide (DMSO) mixed solvent.

[0020] In the step (4), the specific steps of the pure-phase two-dimensional perovskite solution method are as follows: directly spin coating the pure-phase two-dimensional perovskite solution on the three-dimensional perovskite surface, and annealing to obtain a pure-phase two-dimensional perovskite passivation layer.

[0021] The preparation method of the pure-phase two-dimensional perovskite solution is as follows: dissolve lead oxide powder in a mixed solution of hydroiodic acid solution and hypophosphorous acid aqueous solution, continuously stir and heat to 100 °C - 160 °C until the solution becomes bright yellow and clear. Turn off the stirring, slowly add the corresponding amine / ammonium compound and gradually cool down to gradually precipitate pure-phase two-dimensional perovskite crystals, and further filter to separate the solution to obtain pure-phase two-dimensional perovskite solid. Dissolve the pure-phase two-dimensional perovskite crystals in acetonitrile solution to obtain the pure-phase two-dimensional perovskite solution.

[0022] The structure of the amine / ammonium compound for preparing the pure-phase two-dimensional perovskite crystals is:

[0023] In the step (5), the hole transport layer solution includes a hole transport material, an additive, and an organic solvent. The hole transport material is 2,2',7,7'-tetra N , N-Bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD); the additives are lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 4-tert-butylpyridine, and tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt(III) (1,1,1-trifluoro- N -[(trifluoromethyl)sulfonyl]methanesulfonamide salt) (FK209 Co(III)-TFSI); the organic solvent is chlorobenzene or acetonitrile.

[0024] The present invention has the following beneficial effects: This method uses amine / ammonium compounds to synthesize a pure-phase two-dimensional material and dissolve it in an organic solution, dynamically spin-coat it on the surface of three-dimensional perovskite, and anneal it to form a pure-phase two-dimensional perovskite passivation layer. The pure-phase two-dimensional perovskite passivation layer with a wide bandgap is applied on the top of the three-dimensional perovskite, which can improve the energy level alignment between the perovskite layer and the charge transport layer, and effectively prevent electrons from passing through the interface between the perovskite and the hole transport layer; at the same time, the pure-phase two-dimensional perovskite passivation layer can effectively passivate the surface defects of the three-dimensional perovskite thin film.

[0025] The hydrophobic organic spacer layer of the pure-phase two-dimensional perovskite can effectively block moisture, reduce the degradation of the perovskite thin film, and enhance the long-term stability of the device; at the same time, it shows great potential in defect passivation. The present invention provides a passivation method for directly constructing a two-dimensional / three-dimensional heterojunction on the surface of three-dimensional perovskite by a pure-phase two-dimensional solution method. On the one hand, it can combine the high carrier mobility of three-dimensional perovskite and the surface passivation advantages of two-dimensional perovskite, improve the charge extraction efficiency and inhibit non-radiative recombination, thereby enhancing the optoelectronic performance of the device. On the other hand, the preparation process of the pure-phase two-dimensional perovskite solution method is to prepare pure-phase two-dimensional perovskite crystals with a determined n value in advance, dissolve them in an organic solution and then coat them on the three-dimensional perovskite, which can effectively solve the problems in the in-situ passivation method that cannot control the phase purity, film thickness, orientation, etc. of the two-dimensional perovskite layer, and optimize the carrier migration ability of the two-dimensional perovskite layer; at the same time, the in-situ passivation method is more sensitive to process conditions (spin-coating speed, annealing gradient) and it is difficult to passivate uniformly in large-area devices. The pure-phase two-dimensional perovskite solution method has a simple process, excellent light / wet / thermal stability for the prepared devices, is suitable for large-scale production, and helps to accelerate the commercialization process of perovskite solar cells. Description of the Drawings

[0026] Figure 1 Is the current-voltage curve of a perovskite solar cell passivated and modified with pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 Figure 2 Is the X-ray diffraction pattern of the pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 thin film Figure 3Schematic diagram of the water contact angle of perovskite thin films passivated with pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 or not.

[0027] Figure 4 Current-voltage curves of perovskite solar cells passivated with pure-phase two-dimensional perovskite (PEA)2PbI4 or not.

[0028] Figure 5 X-ray diffraction pattern of pure-phase two-dimensional perovskite (PEA)2PbI4 thin film. Detailed implementation manners

[0029] The following specific examples and accompanying drawings are intended to illustrate in detail the preparation method and its application of the present invention. Professionals familiar with the relevant technical fields can easily understand other advantages and effects of the present invention based on the content described in this specification.

[0030] Example 1 Using pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 to passivate perovskite solar cells and its preparation method: The amine / ammonium compound used to prepare pure-phase two-dimensional perovskite is:

[0031] The structure of the perovskite solar cell is: FTO / SnO2 / FAPbI3 / (OCF3-PEA)2PbI4 / Spiro-OMeTAD / Au.

[0032] The preparation process of the above perovskite solar cell is as follows: (1) The FTO (fluorine-doped tin dioxide) conductive glass was ultrasonically cleaned for 30 min each with four solutions of deionized water containing dish detergent, ultrapure water, acetone, and absolute ethanol, and then dried.

[0033] (2) The electron transport layer was prepared by chemical bath deposition. The treated FTO conductive glass was immersed in the chemical bath deposition precursor solution, which was a mixed solution of 137.5 mg of tin(II) chloride dihydrate, 625 mg of urea, 12.5 mL of thioglycolic acid, 625 mL of concentrated hydrochloric acid, and 50 ml of deionized water. The deposition solution was heated at 90°C for 4 h, then ultrasonically treated with deionized water and isopropyl alcohol for 10 min each, dried, annealed on a hot plate at 170°C for 1 h, and then cooled naturally.

[0034] (3) Lead iodide, formamidinium iodide, methylammonium chloride, and methylammonium tribromide were accurately weighed in a molar ratio of 1:1:0.35:0.008 and dissolved in 1 ml of a mixed organic solvent, which was composed ofN , N -dimethylformamide and N , N -dimethyl sulfoxide are prepared in a volume ratio of 8:1. Stir for 2 - 3 hours under the condition of constant temperature at 60 °C to ensure that all components are fully dissolved. Subsequently, a three-dimensional perovskite layer is prepared on the surface of the electron transport layer by a continuous one-step spin-coating process. The spin-coating process is divided into two stages: rotate at 2000 rpm for 10 s and at 6000 rpm for 30 s. 20 s before the end of the second-stage spin-coating, 200 mL of chlorobenzene is dropped onto the substrate on which the perovskite precursor solution has been spin-coated. Finally, the spin-coated substrate is annealed on a hot plate at 100 °C for 1 h.

[0035] (4)On the three-dimensional perovskite layer, 50 mL of a (OCF3-PEA)2PbI4 acetonitrile solution with a concentration of 5 mg mL -1 is dynamically spin-coated at 5000 rpm for 20 s and then annealed on a hot plate at 80 °C for 5 min to construct a pure-phase two-dimensional perovskite passivation layer.

[0036] The preparation method of the (OCF3-PEA)2PbI4 acetonitrile solution is as follows: Dissolve 10 mmol of lead oxide powder in a mixed solution of 57% w / w hydroiodic acid solution and 1.7 mL (15.5 mmol) of 50% hypophosphorous acid aqueous solution, continuously stir and heat to 160 °C until the solution becomes clear and bright yellow. Turn off the stirring, slowly add 10 mmol of OCF3-PEA solution and gradually cool down to gradually precipitate (OCF3-PEA)2PbI4 crystals. Further filter the solution to separate the pure-phase two-dimensional perovskite solid. Dissolve the pure-phase two-dimensional perovskite crystals in an acetonitrile solution to obtain the (OCF3-PEA)2PbI4 acetonitrile solution.

[0037] (5)A hole transport layer precursor solution composed of 50 mg of Spiro-OMeTAD, 19.5 mL of 4-tert-butylpyridine ( t BP), 5 mL of Co (III)TFSI solution (0.25 M acetonitrile solution), 11.5 mL of Li-TFSI solution (1.8 M acetonitrile solution) and 547 mL of chlorobenzene is spin-coated on the surface of the two-dimensional / three-dimensional perovskite heterojunction film at 3000 rpm for 30 s to form a hole transport layer.

[0038] (6)Gold or silver is deposited on the device processed in step (5) by vacuum evaporation, and the thickness of the metal electrode is about 100 nm to obtain a perovskite solar cell passivated by pure-phase two-dimensional perovskite.

[0039] Comparative Example 1 Preparation method of unmodified perovskite solar cell: (1)The FTO conductive glass was ultrasonically cleaned with four solutions of deionized water containing dishwashing liquid, ultrapure water, acetone, and absolute ethanol for 30 min each, and then dried.

[0040] (2)The electron transport layer was prepared by chemical bath deposition. The treated FTO conductive glass was immersed in a chemical bath deposition precursor solution, which was a mixed solution of 137.5 mg of stannous chloride dihydrate, 625 mg of urea, 12.5 mL of mercaptoacetic acid, 625 mL of concentrated hydrochloric acid, and 50 ml of deionized water. Under the constant temperature condition of 90°C, the FTO conductive glass was kept in the deposition solution for 4 hours, and then the deposited FTO conductive glass was ultrasonically cleaned with deionized water and isopropanol in turn, dried, and annealed at 170°C for 1 h.

[0041] (3)Lead iodide, formamidinium iodide, methylammonium chloride, and methylammonium tribromide were dissolved in N , N -dimethylformamide and N , N -dimethyl sulfoxide (volume ratio 8:1) in 1 ml of a mixed organic solvent, and stirred at 60°C for 2 - 3 hours. A perovskite thin film was prepared on the electron transport layer by a continuous one-step spin-coating process. The spin-coating process was divided into two stages: rotating at 2000 rpm for 10 s and at 6000 rpm for 30 s. At the 10th s of rotating at 6000 rpm, 200 mL of chlorobenzene was dynamically spin-coated on the substrate and annealed on a hot plate at 100°C for 1 h.

[0042] (4)A hole transport layer precursor solution composed of 50 mg of Spiro-0MeTAD, 19.5 mL of 4-tert-butylpyridine ( t BP), 5 mL of Co(III)TFSI solution (0.25 M acetonitrile solution), 11.5 mL of Li-TFSI solution (1.8 M acetonitrile solution), and 547 mL of chlorobenzene was spin-coated on the surface of the three-dimensional perovskite thin film at 3000 rpm for 30 s continuously to form a hole transport layer.

[0043] (5)Gold or silver was deposited on the device treated in step (4) by vacuum evaporation, and the metal electrode had a thickness of about 100 nm to obtain an unmodified perovskite solar cell.

[0044] Figure 1The current-voltage curves measured under AM 1.5G simulated sunlight irradiation with an intensity of 100 mW / cm 2 for perovskite solar cells passivated and modified with pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 or not. The best power conversion efficiency (PCE) of Comparative Example 1 is 21.98%, the voltage V oc is 1.15 V, and the current J sc is 25.75 mA cm -2 , and the fill factor (FF) is 74.43%; for Example 1, the cell prepared based on the passivation of pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 V oc has a voltage of 1.19 V and a current J sc of 25.57 mA cm -2 , the fill factor FF is 79.53%, and the best efficiency is 24.26%, which is significantly improved compared with Comparative Example 1, indicating that this passivation material can effectively passivate defects and is more conducive to the transport of carriers.

[0045] Figure 2 is the X-ray diffraction pattern of the pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 film. After spin-coating the pure-phase two-dimensional perovskite material, diffraction peaks at low angles appear in the pattern, indicating the formation of the pure-phase two-dimensional perovskite.

[0046] Figure 3 is a schematic diagram of the water contact angle of perovskite films passivated and modified with pure-phase two-dimensional perovskite (OCF3-PEA)2PbI4 or not. The test results show that the water contact angle of the unpassivated perovskite film is 49.9°, and after passivation, it increases to 74.1°, indicating that the introduction of the pure-phase two-dimensional perovskite material enhances the surface hydrophobicity of the perovskite film, forms an effective protection barrier on the surface of the three-dimensional perovskite, reduces water erosion, and helps to improve the stability of the device.

[0047] Example 2 A perovskite solar cell passivated with pure-phase two-dimensional perovskite (PEA)2PbI4 and its preparation method are provided: The amine / ammonium compound used to prepare the pure-phase two-dimensional perovskite is:

[0048] The structure of the perovskite solar cell is: FTO / SnO2 / FAPbI3 / (PEA)2PbI4 / Spiro-OMeTAD / Au.

[0049] The preparation process of the above perovskite solar cell is as follows: (1) The FTO conductive glass was successively ultrasonically cleaned for 30 min each with four solutions: deionized water containing dishwashing liquid, ultrapure water, acetone, and absolute ethanol, and then dried.

[0050] (2) The electron transport layer was prepared by chemical bath deposition. The treated FTO conductive glass was immersed in the chemical bath deposition precursor solution, which was a mixed solution of 137.5 mg of stannous chloride dihydrate, 625 mg of urea, 12.5 mL of mercaptoacetic acid, 625 mL of concentrated hydrochloric acid, and 50 mL of deionized water. The deposition solution was heated at 90 °C for 4 h, then ultrasonically treated with deionized water and isopropanol for 10 min successively, dried, annealed on a hot plate at 170 °C for 1 h, and then cooled naturally.

[0051] (3) Lead iodide, formamidinium iodide, methylammonium chloride, and methylammonium tribromide were accurately weighed in a molar ratio of 1:1:0.35:0.008 and dissolved in 1 mL of a mixed organic solvent, which was composed of N , N N,N - dimethylformamide and N , N dimethyl sulfoxide prepared in a volume ratio of 8:1. Stirring was carried out at a constant temperature of 60 °C for 2 - 3 h to ensure complete dissolution of each component. Subsequently, a three - dimensional perovskite layer was prepared on the surface of the electron transport layer by a continuous one - step spin - coating process. The spin - coating process was divided into two stages: rotating at 2000 rpm for 10 s and at 6000 rpm for 30 s. 200 mL of chlorobenzene was dropped onto the substrate on which the perovskite precursor solution had been spin - coated 20 s before the end of the second - stage spin - coating. Finally, the spin - coated substrate was annealed on a hot plate at 100 °C for 1 h.

[0052] (4) On the three - dimensional perovskite layer, 50 mL of a (PEA)2PbI4 acetonitrile solution with a concentration of 5 mg mL -1 was dynamically spin - coated at 5000 rpm for 20 s and annealed on a hot plate at 80 °C for 5 min to construct a pure - phase two - dimensional perovskite passivation layer.

[0053] The preparation method of the (PEA)2PbI4 acetonitrile solution is as follows: 10 mmol of lead oxide powder was dissolved in 57% w / wIn a mixed solution of hydroiodic acid solution and 1.7 mL (15.5 mmol) of 50% aqueous hypophosphorous acid solution, continuously stir and heat to 160 °C. The solution is in a clear yellow and clear state. Turn off the stirring, slowly add 10 mmol of PEA solution and gradually cool down. (PEA)2PbI4 crystals gradually precipitate. Further filter the solution to obtain a pure-phase two-dimensional perovskite solid. Dissolve the pure-phase two-dimensional perovskite crystals in an acetonitrile solution to obtain the (PEA)2PbI4 acetonitrile solution.

[0054] (5)A hole transport layer precursor solution composed of 50 mg of Spiro-0MeTAD, 19.5 mL of 4-tert-butylpyridine ( t BP), 5 mL of Co(III)TFSI solution (0.25 M acetonitrile solution), 11.5 mL of Li-TFSI solution (1.8 M acetonitrile solution) and 547 mL of chlorobenzene was spin-coated on the surface of the two-dimensional / three-dimensional perovskite heterojunction film at a rotation speed of 3000 rpm for 30 s to form a hole transport layer.

[0055] (6)Deposit gold or silver on the device processed in step (5) by vacuum evaporation. The thickness of the metal electrode is about 100 nm to obtain a perovskite solar cell passivated by pure-phase two-dimensional perovskite.

[0056] Comparative Example 2 Preparation method of unmodified perovskite solar cell: (1)The FTO conductive glass was ultrasonically cleaned with four solutions of deionized water containing dishwashing liquid, ultrapure water, acetone, and absolute ethanol for 30 min each, and then dried.

[0057] (2)The electron transport layer was prepared by chemical bath deposition. Immerse the treated FTO conductive glass in the chemical bath deposition precursor solution, which is a mixed solution of 137.5 mg of stannous chloride dihydrate, 625 mg of urea, 12.5 mL of mercaptoacetic acid, 625 mL of concentrated hydrochloric acid, and 50 ml of deionized water. Under the constant temperature condition of 90 °C, keep the FTO conductive glass in the deposition solution for 4 hours, and then ultrasonically clean the deposited FTO conductive glass with deionized water and isopropanol in turn, and dry it at 170 °C and anneal for 1 h.

[0058] (3)Dissolve lead iodide, formamidinium iodide, methylammonium chloride, and methylammonium tribromide in a molar ratio of 1:1:0.35:0.008 in N , N -dimethylformamide and N , NIn 1 ml of a mixed organic solvent of dimethyl sulfoxide (volume ratio 8:1), stir at 60 °C for 2 - 3 hours. The perovskite film is prepared by a continuous one-step spin-coating process on the electron transport layer. The spin-coating process is divided into two stages: rotate at 2000 rpm for 10 s and at 6000 rpm for 30 s. At the 10th s of rotating at 6000 rpm, 200 mL of chlorobenzene is dynamically spin-coated on the substrate and annealed on a hot plate at 100 °C for 1 h.

[0059] (4)Mix 50 mg of Spiro-0MeTAD, 19.5 mL of 4-tert-butylpyridine ( t BP), 5 mL of Co(III)TFSI solution (0.25 M acetonitrile solution), 11.5 mL of Li-TFSI solution (1.8 M acetonitrile solution) and 547 mL of chlorobenzene to form a hole transport layer precursor solution. Spin-coat it on the surface of the three-dimensional perovskite film at 3000 rpm for 30 s to form a hole transport layer.

[0060] (5)Deposit gold or silver on the device processed in step (4) by vacuum evaporation. The thickness of the metal electrode is about 100 nm to obtain an unmodified perovskite solar cell.

[0061] Figure 4 Figure shows the current-voltage comparison diagrams of perovskite solar cells with and without passivation by pure-phase two-dimensional perovskite (PEA)2PbI4. After optimizing the preparation conditions, the best power conversion efficiency of the device in Comparative Example 2 is 22.05%, V oc is 1.13 V, J sc is 25.65 mA cm -2 , FF is 75.84%. After being modified with (PEA)2PbI4, the device shows excellent V oc (1.78 V) and J sc (25.77 mA cm -2 ), FF is 77.65%, and the PCE is increased to 23.56%. The pure-phase two-dimensional perovskite effectively passivates the surface defects of the three-dimensional layer, greatly reducing the defect density, thereby improving the optoelectronic performance of the device.

[0062] Figure 5 Figure shows the X-ray diffraction pattern of the pure-phase two-dimensional perovskite (PEA)2PbI4 film. Near 2θ =5.6°, characteristic diffraction peaks can be observed. This peak position corresponds to the structure of two-dimensional perovskite (PEA)2PbI4, which confirms the successful construction of the pure-phase two-dimensional perovskite structure.

Claims

1. A method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite, characterized in that: The steps include: (1) ultrasonically cleaning and drying the conductive substrate; (2) Preparing a tin dioxide electron transport layer on a conductive substrate by chemical bath deposition; (3) After cleaning the substrate on which the electron transport layer is deposited, spin coating the perovskite precursor solution and annealing the substrate to prepare the perovskite layer; The perovskite layer is composed of Cs x (FA, MA) 1-x PbI 3-y Br y One of the following, wherein FA is a carboxamidinium cation CH(NH2)2 + , MA is methylamine cation CH3NH3 + , 0≤ x <0.1,0≤ y <0.6; (4) spin coating a pure two-dimensional perovskite solution on the surface of the perovskite layer, and annealing to obtain a pure two-dimensional perovskite passivation layer; The method for preparing the pure phase two-dimensional perovskite solution comprises: dissolving lead oxide powder in a mixed solution of hydroiodic acid solution and hypophosphorous acid aqueous solution, and continuously stirring and heating to 100° C.-160° C.; adding amine / ammonium compounds and cooling to precipitate pure phase two-dimensional perovskite crystals; and dissolving the crystals in an organic solution to obtain a pure phase two-dimensional perovskite solution; The concentration of the pure phase two-dimensional perovskite solution is 0.5-20 mg / ml; the general structural formula of the amine / ammonium compound is: ； Wherein: R1, R2, R3, R4, R5 are any one of hydrogen, C1-C5 alkyl, C1-C5 substituted alkyl chain, hydroxyl, alkoxy, dimethylamino, mercapto, halogen atom, nitro, cyano, phenyl, naphthyl; n is an integer of 1-12; (5) spin coating a hole transport layer solution to prepare a hole transport layer; (6) The metal electrode is deposited on the surface of the hole transport layer by vacuum evaporation to obtain a perovskite solar cell.

2. The method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite according to claim 1, characterized in that: The hole transport layer solution includes a hole transport material, an additive and an organic solvent; The hole transport material is 2,2',7,7'-tetra[ N , N -bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene; The additives are lithium bis(trifluoromethane)sulfonyl imide, 4-tert-butylpyridine and tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridinium]cobalt[III](1,1,1-trifluoro- N -[(trifluoromethyl)sulfonyl]methanesulfonamide salt); The organic solvent is chlorobenzene or acetonitrile.

3. The method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite according to claim 1, characterized in that: The structure of the amine / ammonium compound is: 。 4. The method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite according to claim 1, characterized in that: The molar ratio of the amine / ammonium compound to the lead oxide is (1-2):

1.

5. The method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite according to claim 1, characterized in that: In the step (4), the organic solvent is one or more of acetonitrile, tetramethyl sulfone, propylene carbonate, ethylene carbonate, etc.

6. A pure phase two-dimensional perovskite surface passivation method for preparing a perovskite solar cell, characterized in that: The method is prepared by any one of claims 1 to 5.

7. The method for preparing a perovskite solar cell by surface passivation of a pure phase two-dimensional perovskite according to claim 1, characterized in that: The perovskite solar cell comprises a transparent conductive substrate, an electron transport layer, a perovskite photoactive layer, a pure phase two-dimensional perovskite passivation layer, a hole transport layer, and a metal electrode.

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