A perovskite film, solar cell device, and preparation method and application thereof

Abstract

The present invention relates to the field of new energy technologies, and in particular to a perovskite film, a solar cell device, and a preparation method and application thereof. The preparation method of the perovskite film comprises the following steps: providing a perovskite precursor solution containing cesium thiocyanate, and forming the perovskite film from the perovskite precursor solution. The present invention introduces cesium thiocyanate molecules and, through an ion exchange reaction, in situ synthesizes a perovskite film having a cesium-rich core-shell structure for use in preparing a solar cell device. The solar cell device not only has a low defect density and superior photoelectric conversion efficiency, but also has the advantages of excellent air, heat, and light stability, which can greatly extend the operating life of the battery.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a perovskite thin film, a solar cell device, and a preparation method and application thereof. Background Art

[0002] With the rapid growth of global industrialization and population, the pursuit of renewable energy has become an urgent challenge. Due to its abundant, clean, and sustainable nature, solar energy is considered a viable alternative to fossil fuels. Over the past decade, photovoltaic technology has made significant progress in power conversion efficiency and applications. Currently, researchers are focusing on emerging photovoltaic technologies targeting diverse applications and potentially lowering costs.

[0003] Perovskite solar cells offer high power conversion efficiency, convenient manufacturing, and low cost, and are expected to further advance the photovoltaic field. Since their introduction in 2009, perovskite solar cells have achieved efficiencies of 25.2%, approaching the peak efficiency of 26.7% for single-crystal silicon solar cells. However, this perovskite material is sensitive to water and oxygen and easily degrades under conditions of sustained sunlight or heat. These stability issues result in poor stability in practical operating environments, hindering commercialization. Summary of the Invention

[0004] In view of the problems in the prior art, the purpose of the present invention is to provide a perovskite film, a solar cell device, and a preparation method and application thereof, which are used to solve the technical problem that conventional metal halide perovskite film components often contain methylammonium and formamidine, which are prone to thermal decomposition or phase separation. In actual operation, they will volatilize and cause degradation of the active layer, thereby reducing device performance. The present invention introduces cesium thiocyanate molecules and, through an ion exchange reaction, in situ synthesizes a perovskite film with a cesium-rich core-shell structure for the preparation of a solar cell device. The solar cell device not only has a low defect density and excellent photoelectric conversion efficiency, but also has the advantages of excellent air, heat and light stability, which can greatly extend the working life of the battery.

[0005] To achieve the above-mentioned and other related objectives, the present invention provides a method for preparing a perovskite thin film in a first aspect, comprising the following steps:

[0006] A perovskite precursor solution containing cesium thiocyanate is provided, and the perovskite thin film is formed by using the perovskite precursor solution.

[0007] Preferably, it also includes at least one of the following technical features:

[0008] 1) coating and anti-solvent treating the perovskite precursor solution, and then annealing the solution to form the perovskite film;

[0009] 2) The perovskite precursor solution includes cesium thiocyanate, a first ion, a second ion and an organic solvent; the first ion is an organic positive ion, or the first ion includes an organic positive ion and an inorganic metal ion; the organic positive ion is selected from at least one of methylammonium ion and formamidine ion, and the inorganic metal ion is selected from at least one of inorganic cesium ion and inorganic rubidium ion; the second ion is selected from at least one of lead ion and tin ion.

[0010] More preferably, it further includes at least one of the following technical features:

[0011] 11) In feature 1), the coating and anti-solvent treatment comprises: during the process of coating the perovskite precursor solution on the substrate, dropping an anti-solvent on the substrate;

[0012] 12) In feature 1), the coating and anti-solvent treatment are performed under an inert atmosphere free of water and oxygen; the inert atmosphere free of water and oxygen may be a nitrogen atmosphere free of water and oxygen;

[0013] 13) In feature 1), the anti-solvent is selected from at least one of toluene, chlorobenzene, diethyl ether, and ethyl acetate;

[0014] 14) In feature 1), the annealing temperature is 80-100°C, such as 80-90°C or 90-100°C;

[0015] 15) In feature 1), the annealing time is 5 to 60 minutes, such as 5 to 10 minutes or 10 to 60 minutes;

[0016] 21) In feature 2), the organic solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and γ-butyrolactone;

[0017] 22) In feature 2), the organic solvent is selected from one of N,N-dimethylformamide and N-methylpyrrolidone;

[0018] 23) In feature 2), the molar ratio of cesium thiocyanate, the first ion, and the second ion is 1-6:90-110:100, such as the molar ratio of cesium thiocyanate to the second ion is 1-2:100, 2-3:100, 3-4:100, or 4-6:100, and the molar ratio of the first ion to the second ion is 90-100:100 or 100-110:100;

[0019] 24) In feature 2), when the first ion comprises an organic positive ion and an inorganic metal ion, the molar ratio of the organic positive ion to the inorganic metal ion is 0.01 to 100:1, such as 0.01:1 to 85:15 or 85:15 to 100:1;

[0020] 25) In feature 2), the concentration of the second ion in the perovskite precursor solution is 0.8 to 1.8 mol / L, such as 0.8 to 1.3 mol / L, 1.3 to 1.4 mol / L, or 1.4 to 1.8 mol / L;

[0021] 26) In feature 2), the cesium thiocyanate is obtained by a preparation method comprising the following steps:

[0022] The cesium carbonate solution is reacted with the ammonium thiocyanate solution to obtain the cesium thiocyanate.

[0023] More preferably, it further includes at least one of the following technical features:

[0024] 221) In feature 22), the volume ratio of N,N-dimethylformamide to N-methylpyrrolidone is 5:0 to 0:5, such as 5:0 to 4:1 or 4:1 to 0:5;

[0025] 261) In feature 26), the molar ratio of cesium carbonate to ammonium thiocyanate is 0.4:1 to 0.6:1, such as 0.4:1 to 0.5:1 or 0.5:1 to 0.6:1;

[0026] 262) In feature 26), the reaction temperature is 20-80°C, such as 20-60°C or 60-80°C;

[0027] 263) In feature 26), the reaction time is 5 to 60 minutes, such as 5 to 10 minutes or 10 to 60 minutes;

[0028] 264) In feature 26), the preparation method further comprises: evaporating, crystallizing, and drying after the reaction. After the reaction, evaporation can be performed using a rotary evaporator; crystallization can be performed by recrystallization using ethanol one or more times; and drying can be performed in a vacuum oven overnight.

[0029] A second aspect of the present invention provides a perovskite thin film obtained by the above-mentioned perovskite thin film preparation method.

[0030] A third aspect of the present invention provides use of the above-mentioned perovskite film in a solar cell device.

[0031] A fourth aspect of the present invention provides a solar cell device comprising the above-mentioned perovskite film.

[0032] Preferably, from bottom to top, it includes a conductive substrate, a hole transport layer, a perovskite film, an electron transport layer, a hole blocking layer and a metal electrode stacked in sequence.

[0033] More preferably, it further includes at least one of the following technical features:

[0034] 1) The conductive substrate is a tin-doped indium oxide conductive substrate;

[0035] 2) The thickness of the hole transport layer is 20 to 50 nm, such as 20 to 30 nm or 30 to 50 nm;

[0036] 3) The thickness of the perovskite film is 200-700 nm, such as 200-500 nm or 500-700 nm;

[0037] 4) The thickness of the electron transport layer is 20 to 50 nm, such as 20 to 30 nm or 30 to 50 nm;

[0038] 5) The thickness of the hole blocking layer is 4 to 8 nm, such as 4 to 6 nm or 6 to 8 nm;

[0039] 6) The metal electrode is Ag, Cu, Al or Au;

[0040] 7) The thickness of the metal electrode is 80-150 nm, such as 80-120 nm or 120-150 nm.

[0041] A fifth aspect of the present invention provides a method for preparing the above-mentioned solar cell device, comprising the following steps:

[0042] 1) coating the conductive substrate with a hole transport solution, and then performing an annealing treatment to form the hole transport layer on the conductive substrate;

[0043] 2) forming the perovskite film on the hole transport layer using the above-mentioned perovskite film preparation method;

[0044] 3) coating an electron transport solution on the perovskite film, and then performing an annealing treatment to form the electron transport layer on the perovskite film; or evaporating an electron transport organic substance on the perovskite film to form the electron transport layer on the perovskite film;

[0045] 4) coating a hole blocking solution on the electron transport layer to form the hole blocking layer on the electron transport layer; or evaporating a hole blocking organic substance on the electron transport layer to form the hole blocking layer on the electron transport layer;

[0046] 5) Vapor-depositing metal on the hole blocking layer to form the metal electrode.

[0047] Preferably, it includes at least one of the following technical features:

[0048] 11) In step 1), before coating, the conductive substrate is pretreated, and the pretreatment includes cleaning and drying. The pretreatment can be performed by cleaning the conductive substrate with one or more of detergent, deionized water, and isopropyl alcohol, drying with nitrogen after cleaning, and performing ultraviolet ozone cleaning;

[0049] 12) In step 1), the hole transport solution is a nickel oxide solution, a PTAA solution, or a PEDOT:PSS solution;

[0050] 13) In step 1), the annealing temperature is 80-140° C., such as 80-100° C. or 100-140° C.;

[0051] 14) In step 1), the annealing time is 5 to 60 minutes, such as 5 to 10 minutes or 10 to 60 minutes;

[0052] 31) In step 3), the annealing temperature is 80-150° C., such as 80-100° C. or 100-150° C.;

[0053] 32) In step 3), the annealing time is 5 to 150 minutes, such as 5 to 10 minutes or 10 to 150 minutes;

[0054] 33) In step 3), the electron transport solution is a PCBM solution or C 60 solution;

[0055] 34) In step 3), the electron transport organic compound is C 60 powder;

[0056] 35) In step 3), the vacuum degree is 10 -6 ~10 -8 Performed in Torr environment;

[0057] 41) In step 4), the hole blocking solution is a BCP solution;

[0058] 42) In step 4), the hole-blocking organic compound is BCP powder;

[0059] 43) In step 4), at a vacuum degree of 10 -6 ~10 -8 Performed in Torr environment;

[0060] 51) In step 5), the vacuum degree is 10 -6 ~10 -8 Torr environment, such as 10 -6 ~10 -7 Torr or 10 -7 ~10 -8 Torr.

[0061] The above technical solution has the following beneficial effects:

[0062] 1. The present invention forms a perovskite film by using a perovskite precursor solution containing cesium thiocyanate. During annealing, cesium thiocyanate will participate in the phase change process of the perovskite crystal film, and undergo an ion exchange reaction with methylammonium and / or formamidine on the surface of the perovskite grains to generate methylamine gas and / or formamidine gas, as well as thiocyanate gas. The grain surface is coated with cesium ions, ultimately forming a perovskite film with a cesium-rich core-shell structure. The perovskite film can effectively improve the quality of the perovskite film, reduce the defect density, and increase the carrier lifetime, thereby improving the photoelectric conversion efficiency of the perovskite solar cell device. Currently, the photoelectric conversion efficiency of the inverse structure is generally 17-19%. Compared with the prior art, the photoelectric conversion efficiency of the present application is 1-2% higher, and the present application can be well implemented using traditional processes.

[0063] 2. This invention utilizes an in-situ cesium-rich core-shell structure, creating a surface inorganic shell that effectively isolates water and oxygen, significantly enhancing the solar cell device's air stability. Furthermore, the surface shell effectively inhibits ion migration, significantly improving the solar cell device's light stability and significantly extending its operating life at high temperatures.

[0064] 3. The preparation method of the present invention is simple and has important research significance for improving the stability and commercial feasibility of solar cell devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of the structure of the solar cell device of Examples 1, 2, 3 and Comparative Example 1.

[0066] Figure 2 The X-ray diffraction patterns and Fourier transform infrared spectra of the CsSCN powders synthesized in Examples 1, 2, and 3 are shown.

[0067] Figure 3 X-ray diffraction patterns of the perovskite films of Examples 1, 2, 3 and Comparative Example 1.

[0068] Figure 4 Scanning electron microscope images of the perovskite films of Examples 1, 2, 3 and Comparative Example 1.

[0069] Figure 5 Time-of-flight secondary ion mass spectrometry data of the perovskite film before and after heat treatment of Example 2.

[0070] Figure 6 FTIR-AFM images of the perovskite films of Example 2 and Comparative Example 1.

[0071] Figure 71 is a dark-field transmission electron microscope image of the perovskite film of Example 1 and the corresponding energy spectrum line scan map.

[0072] Figure 8 These are the steady-state and transient fluorescence spectra of the perovskite films of Examples 1, 2, 3 and Comparative Example 1.

[0073] Figure 9 The JV curves of the solar cell devices of Examples 1, 2, 3 and Comparative Example 1 under a standard solar simulator are shown.

[0074] Figure 10 Graph showing the stability data of the solar cell devices of Example 2 and Comparative Example 1.

[0075] Figure 11 The UV-visible absorption spectra of the toluene solutions and the X-ray diffraction spectra of the corresponding films of the solar cell devices of Example 2 and Comparative Example 1 were respectively immersed in toluene and continuously irradiated with light.

[0076] Figure 12 Theoretical simulation calculations of the structures and corresponding defect formation energies for Example 2 and Comparative Example 1.

[0077] Reference numerals

[0078] 1 Conductive substrate

[0079] 2 Hole transport layer

[0080] 3 Perovskite thin films

[0081] 4 Electron transport layer

[0082] 5 Hole blocking layer

[0083] 6 Metal electrodes DETAILED DESCRIPTION

[0084] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0085] In the following examples, all reagents, materials and instruments used are commercially available unless otherwise specified.

[0086] Example 1

[0087] (1) Dissolve 3.0 g of NH4SCN and 6.42 g of Cs2CO3 in deionized water. Then, add the cesium carbonate solution dropwise to the ammonium thiocyanate solution and stir at 60°C for 10 minutes. Then, rotary evaporation is performed to obtain a white crude product. The crude product is recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0088] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0089] (3) Formamidine iodide (FAI), lead iodide (PbI2) and cesium iodide (CsI) were dissolved in a molar ratio of 0.85:1:0.15 in a mixed solution of N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) with a volume ratio of 4:1, and cesium thiocyanate (CsSCN) with a molar mass of 1 mol% (i.e., the molar ratio of cesium thiocyanate to lead ions is 1:100) was added. The mixture was stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a lead ion concentration of 1.4 mol / L.

[0090] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then 30 mg / mL of nickel oxide (NiO x ) aqueous solution, rotated at a rotation speed of 2000 rpm for 30 seconds, and then annealed at a temperature of 140° C. for 10 minutes to obtain a hole transport layer with a thickness of 30 nm.

[0091] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 150 μL of chlorobenzene antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 100 °C for 10 minutes to obtain a perovskite thin film layer with a thickness of 500 nm.

[0092] (6) A PCBM chlorobenzene solution (20 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 100°C for 10 minutes to obtain an electron transport layer with a thickness of 30 nm.

[0093] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a rotation speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 6 nm.

[0094] (8) Using the thermal evaporation method, the vacuum degree is 10 -7 Under a Torr environment, a Cu electrode was evaporated on the hole blocking layer with a thickness of 120 nm.

[0095] Example 2

[0096] (1) Dissolve 3.0 g of NH4SCN and 6.42 g of Cs2CO3 in deionized water. Then, add the cesium carbonate solution dropwise to the ammonium thiocyanate solution and stir at 60°C for 10 minutes. Then, rotary evaporation is performed to obtain a white crude product. The crude product is recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0097] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0098] (3) Formamidine iodide (FAI), lead iodide (PbI2) and cesium iodide (CsI) were dissolved in a molar ratio of 0.85:1:0.15 in a mixed solution of N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) with a volume ratio of 4:1, and cesium thiocyanate (CsSCN) with a molar mass of 2 mol% (i.e., the molar ratio of cesium thiocyanate to lead ions is 2:100) was added. The mixture was stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a lead ion concentration of 1.4 mol / L.

[0099] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then 30 mg / mL of nickel oxide (NiO x ) aqueous solution, rotated at a rotation speed of 2000 rpm for 30 seconds, and then annealed at a temperature of 140° C. for 10 minutes to obtain a hole transport layer with a thickness of 30 nm.

[0100] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 150 μL of chlorobenzene antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 100 °C for 10 minutes to obtain a perovskite thin film layer with a thickness of 500 nm.

[0101] (6) A PCBM chlorobenzene solution (20 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 100°C for 10 minutes to obtain an electron transport layer with a thickness of 30 nm.

[0102] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a rotation speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 6 nm.

[0103] (8) Using the thermal evaporation method, the vacuum degree is 10 -7 Under a Torr environment, a Cu electrode was evaporated on the hole blocking layer with a thickness of 120 nm.

[0104] Example 3

[0105] (1) Dissolve 3.0 g of NH4SCN and 6.42 g of Cs2CO3 in deionized water. Then, add the cesium carbonate solution dropwise to the ammonium thiocyanate solution and stir at 60°C for 10 minutes. Then, rotary evaporation is performed to obtain a white crude product. The crude product is recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0106] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0107] (3) Formamidine iodide (FAI), lead iodide (PbI2) and cesium iodide (CsI) were dissolved in a molar ratio of 0.85:1:0.15 in a mixed solution of N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) with a volume ratio of 4:1, and cesium thiocyanate (CsSCN) with a molar mass of 6 mol% (i.e., the molar ratio of cesium thiocyanate to lead ions is 6:100) was added. The mixture was stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a lead ion concentration of 1.4 mol / L.

[0108] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then 30 mg / mL of nickel oxide (NiO x ) aqueous solution, rotated at a rotation speed of 2000 rpm for 30 seconds, and then annealed at a temperature of 140° C. for 10 minutes to obtain a hole transport layer with a thickness of 30 nm.

[0109] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 150 μL of chlorobenzene antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 100 °C for 10 minutes to obtain a perovskite thin film layer with a thickness of 500 nm.

[0110] (6) A PCBM chlorobenzene solution (20 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 100°C for 10 minutes to obtain an electron transport layer with a thickness of 30 nm.

[0111] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a rotation speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 6 nm.

[0112] (8) Using the thermal evaporation method, the vacuum degree is 10 -7 Under a Torr environment, a Cu electrode was evaporated on the hole blocking layer with a thickness of 120 nm.

[0113] Comparative Example 1

[0114] (1) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0115] (2) Formamidine iodide (FAI), lead iodide (PbI2) and cesium iodide (CsI) were dissolved in a mixed solution of N, N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) in a molar ratio of 0.85:1:0.15, with a volume ratio of 4:1, and stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a lead ion concentration of 1.4 mol / L.

[0116] (3) The ITO substrate was treated with UV ozone for 20 minutes, and then 30 mg / mL of nickel oxide (NiO x ) aqueous solution, rotated at a rotation speed of 2000 rpm for 30 seconds, and then annealed at a temperature of 140° C. for 10 minutes to obtain a hole transport layer with a thickness of 30 nm.

[0117] (4) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution was added dropwise onto the hole transport layer and rotated at 4000 rpm for 40 seconds. 150 μL of chlorobenzene antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 100 °C for 10 minutes to obtain a perovskite thin film layer with a thickness of 500 nm.

[0118] (5) A PCBM chlorobenzene solution (20 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 100°C for 10 minutes to obtain an electron transport layer with a thickness of 30 nm.

[0119] (6) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a rotation speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 6 nm.

[0120] (7) Using the thermal evaporation method, the vacuum degree is 10 -7 Under a Torr environment, a Cu electrode was evaporated on the hole blocking layer with a thickness of 120 nm.

[0121] The solar cell device is obtained by the above preparation method, such as Figure 1 As shown, from bottom to top, it includes a conductive substrate 1, a hole transport layer 2, a perovskite film 3, an electron transport layer 4, a hole blocking layer 5 and a metal electrode 6 stacked in sequence.

[0122] Depend on Figure 2 It can be seen that the diffraction peaks of the CsSCN powders synthesized in Examples 1, 2, and 3 match well with the standard PDF card, and there are no other impurity diffraction peaks, indicating that the synthesized CsSCN is of high purity. In addition, the Fourier transform infrared spectroscopy test shows that the peak at 2020 cm -1A strong absorption peak appears at the position, which corresponds to the C≡N vibration in the thiocyanate.

[0123] Depend on Figure 3 It can be seen that the perovskite films of Comparative Example 1 and Examples 1, 2, and 3 all exhibit cubic phase characteristics. At the same time, the (110) and (220) characteristic diffraction peak positions of Examples 1, 2, and 3 have a higher angle shift relative to Comparative Example 1, which indicates that the interplanar spacing of the crystals of Examples 1, 2, and 3 has become smaller. The reason for the smaller interplanar spacing is that smaller ions have entered the crystal lattice. These ions are Cs ions in the CsSCN additive.

[0124] from Figure 4 As can be seen, the grain sizes of Examples 1, 2, and 3 containing the CsSCN additive are significantly larger than those of Comparative Example 1, indicating that Example 1 has a lower grain boundary density. As the concentration of added CsSCN increases, the grain size also gradually increases. This grain size increase can be attributed to the influence of the SCN functional groups.

[0125] Figure 5 The ToF-SIMS data of Example 2 before and after annealing are shown in Table 2. We found that before annealing, SCN - The signal is evenly distributed in the perovskite film, and after annealing, the surface SCN - The signal is reduced by an order of magnitude. This indicates that the surface SCN - It evaporates during the annealing process. The reaction process is as follows:

[0126]

[0127] Depend on Figure 6 It can be seen that the FA concentration on the grain surface of Example 2 with the CsSCN additive is significantly lower than that inside the grain. Through stoichiometric ratio calculation, it can be seen that the reduced FA concentration will be compensated by the Cs element in the CsSCN additive. Therefore, Example 1 has a cesium-rich core-shell structure.

[0128] Depend on Figure 7 It can be seen that the N element distribution on the grain surface is less than that in the grain interior, while the Cs element is more distributed on the surface, which further proves the cesium-rich core-shell structure of Example 2.

[0129] Depend on Figure 8 It can be seen that the steady-state fluorescence intensity of the perovskite films prepared in Examples 1 and 2 is significantly stronger than that of Comparative Example 1. At the same time, analysis of the transient fluorescence lifetime shows that the carrier lifetimes of Examples 1 and 2 are significantly longer. This indicates that the cesium-rich core-shell films of Examples 1 and 2 have lower non-radiative recombination and lower defect density.

[0130] Depend on Figure 9It can be seen that the prepared solar cell devices all exhibit good photoelectric conversion efficiency, and the device of Example 2 has a higher photoelectric conversion efficiency of 20.7%. Figure 9 The JV curve is obtained by changing the voltage from the open circuit voltage to the short circuit current, recording the corresponding current value, with a point interval of 0.01V and a scan rate of 30ms.

[0131] Depend on Figure 10 It can be seen that the solar cell devices of Comparative Example 1 and Example 2 both exhibit good air, thermal, and operational stability, with the core-shell structure device of Example 2 exhibiting even superior stability. The unencapsulated device retained 80% of its original efficiency after 1000 hours in air, and 82% of its original efficiency after 1000 hours in a nitrogen glove box at 60°C. The encapsulated device retained 95% of its original efficiency after 1000 hours of continuous maximum power point operation at room temperature in the atmosphere, and 90% of its original efficiency after 250 hours of continuous maximum power point operation at 60°C. The efficiency of the unencapsulated device was obtained by measuring the JV curve at a 0.01V interval and a 30ms scan rate. The efficiency of the encapsulated device, maintained at maximum power point, was obtained by running the JV curve every 10 minutes at a 0.01V interval and a 50ms scan rate.

[0132] Depend on Figure 11 It can be seen that after two days of continuous irradiation in an oxygen-permeable environment, the absorbance of the toluene solution in which the comparative example 1 film was immersed at 500nm was greatly improved. This shows that the comparative example 1 film was significantly degraded. In contrast, the absorbance change of the toluene solution in which Example 2 was immersed was small, indicating that the degradation of the Example 2 film was effectively suppressed. In addition, in the XRD spectrum, we observed the presence of δ-CsPbI3 and PbI2 peaks in the aged comparative example 1 film, while these peaks were not observed in the Example 2 film. This further confirms that the cesium-rich surface inhibits the reaction between oxygen and the perovskite surface and the decomposition of the perovskite structure. Experimental steps: The prepared perovskite film (2.5cm×2.5cm) was immersed in 10mL of toluene and exposed to 30mW cm -2 The xenon lamp provides continuous illumination, and pure oxygen gas is slowly introduced during the illumination process.

[0133] Depend on Figure 12It can be seen that the surface Cs-rich core-shell structure shows higher defect formation energy in PbI2 vacancies and FAI vacancies, which indicates that the Cs-rich core-shell structure does help to reduce Schottky vacancies. This explains the reduced defect density and the suppression of ion migration in the film of Example 2, and explains the source of the excellent performance of Example 2. Calculation steps: The first-principles calculations were performed by using the VASP and PAW methods, and the GGA formulated by PBE was used as the exchange correlation function. A 4*4*4 unit cell was used in the calculation of the defect formation energy of the mixed cation perovskite. The calculated crystal formula is Cs 0.156 FA 0.844 PbI3.

[0134] Example 4

[0135] (1) NH4SCN and Cs2CO3 were dissolved in deionized water at a molar ratio of 0.4:1. The cesium carbonate solution was then added dropwise to the ammonium thiocyanate solution and stirred at 20°C for 60 minutes. A white crude product was then obtained by rotary evaporation. The crude product was recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0136] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0137] (3) Methylamine iodide, tin iodide and rubidium iodide were dissolved in N,N-dimethylformamide (DMF), wherein the total molar ratio of methylamine iodide and rubidium iodide to the molar ratio of tin iodide was 90:100, and the molar ratio of methylamine iodide to rubidium iodide was 100:1; cesium thiocyanate (CsSCN) with a molar mass of 4 mol% (i.e., the molar ratio of cesium thiocyanate to tin ions was 4:100) was added, and the mixture was stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a tin ion concentration of 0.8 mol / L.

[0138] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then a 2 mg / mL PTAA chlorobenzene solution was added dropwise. The substrate was rotated at 2000 rpm for 30 seconds and then annealed at 80°C for 60 minutes to obtain a hole transport layer with a thickness of 50 nm.

[0139] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 200 μL of ethyl acetate antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 80 °C for 60 minutes to obtain a perovskite thin film layer with a thickness of 200 nm.

[0140] (6) On the perovskite film, the vacuum degree is 10 -8 Evaporation of C in a Torr environment60 The electron transport organic material is used to obtain an electron transport layer with a thickness of 50 nm.

[0141] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 8 nm.

[0142] (8) Using the thermal evaporation method, the vacuum degree is 10 -8 Under a Torr environment, an Al electrode was evaporated on the hole blocking layer with a thickness of 150 nm.

[0143] Example 5

[0144] (1) NH4SCN and Cs2CO3 were dissolved in deionized water at a molar ratio of 0.6:1. The cesium carbonate solution was then added dropwise to the ammonium thiocyanate solution and stirred at 80°C for 5 minutes. A white crude product was then obtained by rotary evaporation. The crude product was recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0145] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0146] (3) Methylamine iodide, formamidine iodide, tin iodide, lead iodide, rubidium iodide and cesium iodide are dissolved in N-methylpyrrolidone, wherein the total molar number of methylamine iodide, formamidine iodide, rubidium iodide and cesium iodide: the total molar number of tin iodide and lead iodide is 110:100, the total molar number of methylamine iodide and formamidine iodide: the total molar number of rubidium iodide and cesium iodide is 0.01:1, and the ratio of methylamine iodide to formamidine iodide is 0.01:1. The molar ratio is 1:1, the molar ratio of tin iodide to lead iodide is 1:1, and the molar ratio of rubidium iodide to cesium iodide is 1:1; cesium thiocyanate (CsSCN) with a molar mass of 3 mol% (i.e., the molar number of cesium thiocyanate: the total molar number of tin ions and lead ions is 3:100) is added, and stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a total concentration of lead ions and tin ions of 1.8 mol / L.

[0147] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then a PEDOT:PSS aqueous solution (commercial model 4083) was added dropwise, rotated at 4000 rpm for 30 seconds, and then annealed at 100°C for 5 minutes to obtain a hole transport layer with a thickness of 20 nm.

[0148] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 600 μL of ether antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 90 °C for 5 minutes to obtain a perovskite thin film layer with a thickness of 700 nm.

[0149] (6) A PCBM chlorobenzene solution (15 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 80°C for 5 minutes to obtain an electron transport layer with a thickness of 20 nm.

[0150] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 4 nm.

[0151] (8) Using the thermal evaporation method, the vacuum degree is 10 -6 Under a Torr environment, an Ag electrode was evaporated on the hole blocking layer with a thickness of 80 nm.

[0152] Example 6

[0153] (1) NH4SCN and Cs2CO3 were dissolved in deionized water at a molar ratio of 0.6:1. The cesium carbonate solution was then added dropwise to the ammonium thiocyanate solution and stirred at 80°C for 5 minutes. A white crude product was then obtained by rotary evaporation. The crude product was recrystallized twice from ethanol and dried in a vacuum oven at 60°C overnight to obtain CsSCN as a white powder.

[0154] (2) Provide a tin-doped indium oxide (ITO) transparent conductive substrate and perform standardized cleaning.

[0155] (3) Methylamine iodide and lead iodide were dissolved in N-methylpyrrolidone, wherein the molar ratio of methylamine iodide to lead iodide was 110:100; cesium thiocyanate (CsSCN) with a molar mass of 3 mol% (i.e., the molar ratio of cesium thiocyanate to lead ions was 3:100) was added, and stirred at room temperature for 1 hour to obtain a perovskite precursor solution with a lead ion concentration of 1.3 mol / L.

[0156] (4) The ITO substrate was treated with UV ozone for 20 minutes, and then a PEDOT:PSS aqueous solution (commercial model 4083) was added dropwise, rotated at 4000 rpm for 30 seconds, and then annealed at 100°C for 5 minutes to obtain a hole transport layer with a thickness of 20 nm.

[0157] (5) In an anhydrous and oxygen-free nitrogen glove box, the perovskite precursor solution with CsSCN added was added dropwise to the hole transport layer and rotated at 4000 rpm for 40 seconds. 600 μL of ether antisolvent was added dropwise in the 5th second before the end, and then annealed on a hot plate at 90 °C for 5 minutes to obtain a perovskite thin film layer with a thickness of 500 nm.

[0158] (6) A PCBM chlorobenzene solution (15 mg / mL) was spin-coated on the perovskite film at a speed of 1500 rpm for 30 seconds, and then annealed on a hot plate at 80°C for 5 minutes to obtain an electron transport layer with a thickness of 20 nm.

[0159] (7) A BCP saturated isopropyl alcohol solution was spin-coated on the electron transport layer at a speed of 5000 rpm for 30 seconds to obtain a hole blocking layer with a thickness of 4 nm.

[0160] (8) Using the thermal evaporation method, the vacuum degree is 10 -6 Under a Torr environment, an Ag electrode was evaporated on the hole blocking layer with a thickness of 80 nm.

[0161] The solar cell device is obtained by the above preparation method, such as Figure 1 As shown, from bottom to top, it includes a conductive substrate 1, a hole transport layer 2, a perovskite film 3, an electron transport layer 4, a hole blocking layer 5 and a metal electrode 6 stacked in sequence.

[0162] The prepared solar cell devices were tested using a JV curve, showing a photoelectric conversion efficiency of 6% for Example 4, 17% for Example 5, and 19% for Example 6. The JV curve was generated by varying the voltage from the open-circuit voltage to the short-circuit current, recording the corresponding current values, with a sampling interval of 0.01 V and a scan rate of 30 ms.

[0163] The solar cell devices of Examples 4 and 5 were packaged. Example 4 was able to operate continuously at maximum power point (MPP) for up to 50 hours at room temperature in the atmosphere. Example 5 was able to operate continuously at MPP for up to 150 hours at room temperature in the atmosphere. Example 6 was able to operate continuously at MPP for up to 200 hours at room temperature in the atmosphere. The packaged devices were maintained operating at MPP, and their efficiencies were measured by running JV curves every 10 minutes, with a sampling interval of 0.01 V and a scan rate of 50 ms.

[0164] By analyzing the transient fluorescence lifetime, it is known that the carrier lifetimes of Examples 4, 5, and 6 are longer, which indicates that the cesium-rich core-shell structure films of Examples 4, 5, and 6 have lower non-radiative recombination and lower defect density.

[0165] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a perovskite thin film, characterized in that: The steps include: A perovskite precursor solution containing cesium thiocyanate is provided, the perovskite precursor solution is coated and anti-solvent treated, and then annealed to form a perovskite film with a cesium-rich core-shell structure; the perovskite precursor solution includes cesium thiocyanate, a first ion, a second ion, and an organic solvent; the first ion is an organic positive ion, or the first ion includes an organic positive ion and an inorganic metal ion; the organic positive ion is selected from at least one of methylammonium ions and formamidine ions, and the inorganic metal ion is selected from at least one of inorganic cesium ions and inorganic rubidium ions; and the second ion is selected from at least one of lead ions and tin ions.

2. The method for preparing a perovskite thin film according to claim 1, wherein: Also includes at least one of the following technical features: The coating and anti-solvent treatment comprises: during the process of coating the perovskite precursor solution on the substrate, dropping an anti-solvent on the substrate; The coating and anti-solvent treatment are carried out in an inert atmosphere free of water and oxygen; The anti-solvent is selected from at least one of toluene, chlorobenzene, ether and ethyl acetate; Annealing temperature is 80~100 o C; The annealing time is 5 to 60 minutes.

3. The method for preparing a perovskite thin film according to claim 1, wherein: Also includes at least one of the following technical features: The organic solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and γ-butyrolactone; The molar ratio of cesium thiocyanate, the first ion, and the second ion is 1-6:90-110:100; When the first ion includes an organic positive ion and an inorganic metal ion, the molar ratio of the organic positive ion to the inorganic metal ion is 0.01-100:1; In the perovskite precursor solution, the concentration of the second ion is 0.8-1.8 mol / L; The cesium thiocyanate is obtained by a preparation method comprising the following steps: The cesium carbonate solution is reacted with the ammonium thiocyanate solution to obtain the cesium thiocyanate.

4. The method for preparing a perovskite thin film according to claim 3, wherein: Also includes at least one of the following technical features: The volume ratio of N, N-dimethylformamide and N-methylpyrrolidone is 5:0~0:5; The molar ratio of cesium carbonate to ammonium thiocyanate is 0.4:1 to 0.6:1; The reaction temperature is 20~80 o C; The reaction time is 5 to 60 minutes; The preparation method of cesium thiocyanate further comprises: evaporation, crystallization and drying after the reaction.

5. The perovskite film obtained by the method for preparing a perovskite film according to any one of claims 1 to 4.

6. Use of the perovskite film according to claim 5 in a solar cell device.

7. A solar cell device, characterized in that: Comprising the perovskite thin film according to claim 5.

8. The solar cell device according to claim 7, wherein: From bottom to top, it includes a conductive substrate (1), a hole transport layer (2), a perovskite film (3), an electron transport layer (4), a hole blocking layer (5) and a metal electrode (6) stacked in sequence.

9. The solar cell device according to claim 8, wherein Also includes at least one of the following technical features: The conductive substrate is a tin-doped indium oxide conductive substrate; The thickness of the hole transport layer is 20-50 nm; The thickness of the perovskite film is 200-700 nm; The thickness of the electron transport layer is 20-50 nm; The thickness of the hole blocking layer is 4-8 nm; The metal electrode is Ag, Cu, Al or Au; The thickness of the metal electrode is 80-150 nm.

10. The method for preparing a solar cell device according to any one of claims 8 to 9, wherein: The steps include: coating the conductive substrate with a hole transport solution, and then performing an annealing treatment to form the hole transport layer on the conductive substrate; Forming the perovskite thin film on the hole transport layer using the preparation method of the perovskite thin film according to any one of claims 1 to 4; coating an electron transport solution on the perovskite film, and then performing an annealing treatment to form the electron transport layer on the perovskite film; Alternatively, an electron transport organic material is evaporated on the perovskite film to form the electron transport layer on the perovskite film; Coating a hole blocking solution on the electron transport layer to form the hole blocking layer on the electron transport layer; or evaporating a hole blocking organic substance on the electron transport layer to form the hole blocking layer on the electron transport layer; The metal electrode is formed by evaporating metal on the hole blocking layer.

11. The method for preparing a solar cell device according to claim 10, wherein: Include at least one of the following technical features: In step 1), before coating, the conductive substrate is pre-treated, and the pre-treatment includes cleaning and drying; In step 1), the hole transport solution is a nickel oxide solution, a PTAA solution or a PEDOT:PSS solution; In step 1), the annealing temperature is 80-140°C; In step 1), the annealing time is 5 to 60 minutes; 31) In step 3), the annealing temperature is 80~150 o C; 32) In step 3), the annealing time is 5 to 150 minutes; 33) In step 3), the electron transport solution is a PCBM solution or C 60 solution; 34) In step 3), the electron transport organic compound is C 60 powder; 35) In step 3), the vacuum degree is 10 -6 ~10 -8 Performed in Torr environment; 41) In step 4), the hole blocking solution is a BCP solution; 42) In step 4), the hole-blocking organic compound is BCP powder; 43) In step 4), at a vacuum degree of 10 -6 ~10 -8 Performed in Torr environment; 51) In step 5), the vacuum degree is 10 -6 ~10 -8 It is performed in Torr environment.

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