Preparation method of perovskite thin film, perovskite / silicon laminated cell and preparation method of perovskite / silicon laminated cell

Abstract

The invention provides a preparation method of a perovskite thin film, a perovskite / silicon laminated cell and a preparation method. The method comprises the following steps: depositing lead iodide and cesium bromide on a crystal silicon bottom cell through thermal evaporation to obtain an inorganic composite film, processing the inorganic composite film by using a fused bis-heterocyclic compound solution to obtain a mesoporous structure composite film, preparing an ammonium salt layer on the mesoporous structure composite film, and annealing to form a perovskite film. The solution can promote recrystallization of lead iodide, bicyclic sulfur / nitrogen atoms are coordinated with lead ions to form a five-membered ring chelate, nucleation of lead iodide is delayed, layered stacking is hindered by a bicyclic rigid structure, and vertically-oriented nano-channels are synergistically formed to assist ammonium salt diffusion. R2 long-chain alkyl groups are orderly stacked on a perovskite (001) crystal face to reduce surface energy, the crystal is promoted to preferentially nucleate on the (001) face and vertically and orderly grow, an R1 group, perovskite A-site cations and halide ions form hydrogen bonds, ion escape during annealing is inhibited, defects are reduced, and finally the quality of the perovskite thin film and the performance of the laminated cell are improved.

Description

Technical Field

[0001] This application relates to the field of perovskite solar cells, and more particularly to a method for preparing a perovskite thin film, a perovskite / silicon tandem solar cell, and a method for preparing the same. Background Technology

[0002] To achieve carbon neutrality, new energy technologies are developing rapidly, with solar cells receiving significant attention as a crucial field. Perovskite, with its high absorption coefficient, tunable bandgap, low fabrication cost, and high theoretical efficiency, has become a research hotspot in the photovoltaic field and has been widely explored. Given the tunable bandgap of perovskite, perovskite solar cells can be connected in series with crystalline silicon cells to form tandem cells, enhancing sunlight absorption and improving the photoelectric conversion efficiency. The theoretical limit of photoelectric conversion efficiency for perovskite-crystalline silicon tandem cells can reach 45%, and currently, in the laboratory, 1cm... 2 The perovskite-crystalline silicon tandem solar cell has achieved a photoelectric conversion efficiency of 34.85%, breaking the theoretical limit of single-cell perovskite and crystalline silicon cells, and is regarded as one of the most promising photovoltaic cells.

[0003] However, the fabrication of perovskite / silicon tandem solar cells still faces many challenges. Especially when constructing tandem solar cells on large-textured crystalline silicon substrates, the large textured surface of the untreated substrate makes it difficult to completely cover the surface using traditional one-step solution methods, easily leading to short circuits. Although etching can reduce the texture height, it causes light absorption loss, affecting cell efficiency. To avoid altering the structure of the crystalline silicon substrate, another method involves first preparing an inorganic film on the surface via thermal evaporation, then preparing an organic layer on top of this inorganic film, followed by annealing to form the perovskite film. However, in this method, the inorganic film surface is dense and the organic layer reaction is insufficient, which not only reduces cell performance but also shortens device lifespan. These problems restrict the further development and application of perovskite / silicon tandem solar cells. Summary of the Invention

[0004] This application provides a method for preparing a perovskite thin film, a perovskite / silicon tandem solar cell, and a method for preparing a perovskite thin film. The method involves treating an inorganic composite lead iodide / cesium bromide thin film with a solution of a fused bicyclic compound containing a thiophene-pyrazole bicyclic structure to obtain a mesoporous composite thin film, and then preparing an ammonium salt layer on it to form a perovskite thin film. The fused bicyclic heterocyclic compound solution promotes lead iodide recrystallization. The sulfur / nitrogen atoms of its thiophene-pyrazole bicyclic ring strongly coordinate with lead ions to form a stable five-membered ring chelate, which delays lead iodide nucleation. At the same time, the rigid bicyclic structure hinders layered stacking and synergistically forms vertically oriented nanopores, providing channels for ammonium salt diffusion. The R2 long-chain alkyl group is orderly stacked on the perovskite (001) crystal plane through hydrophobic segments, which significantly reduces the surface energy of the crystal plane. The reduced surface energy makes the (001) plane the preferred nucleation site for crystals, forming an orderly growth of the vertical substrate, thereby effectively improving the quality of perovskite polycrystalline thin films. The R1 group forms hydrogen bonds with the perovskite A-site cations and halide ions, inhibiting ion escape during annealing, reducing defect formation, and optimizing the performance of thin films and tandem batteries.

[0005] In a first aspect, this application provides a method for preparing a perovskite thin film, the method comprising:

[0006] Inorganic composite films were obtained by depositing lead iodide and cesium bromide on crystalline silicon bottom cells via thermal evaporation.

[0007] The inorganic composite film is treated with a first solution to obtain a mesoporous composite film. The first solution comprises a fused bicyclic compound and a first solvent. The general formula of the fused bicyclic compound is: The R1 group is selected from one of amino, phosphonic acid, carboxyl, and fluorine; the R2 is selected from one of C2-10 alkyl carbon chains; and the first solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, 2-methoxyethanol, n-butanol, isobutanol, isopropanol, ethanol, methanol, and acetonitrile.

[0008] An ammonium salt layer was prepared on the mesoporous composite film and then annealed to obtain the perovskite film.

[0009] In some embodiments, the first solvent includes at least one of 2-methoxyethanol, n-butanol, isobutanol, isopropanol, ethanol, methanol, and N-methylpyrrolidone, and the concentration of the first solution is 0.1-100 mg / ml.

[0010] In some embodiments, the R1 group comprises a phosphonic acid group, the R2 comprises a C8 alkyl carbon chain, the first solvent is a mixed solvent of n-butanol and N-methylpyrrolidone in a volume ratio of 7:3, and the concentration of the first solution is 1.5 mg / ml.

[0011] In some embodiments, the inorganic composite film is prepared by vapor deposition, wherein the ratio of lead iodide to cesium bromide in the inorganic composite film is 3:1-9:1, and the thickness of the inorganic composite film is 100-600 nm.

[0012] In some embodiments, treating the inorganic composite film with the first solution includes: applying the first solution onto the inorganic composite film using any one of spin coating, blade coating, spray coating, or slot coating; and performing gradient annealing on the inorganic composite film coated with the first solution.

[0013] In some embodiments, the gradient annealing process includes: annealing at 70°C for 3 minutes, followed by annealing at 150°C for 10 minutes.

[0014] In some embodiments, the preparation of the ammonium salt layer on the mesoporous composite film includes: dissolving formamidine iodoformidium, formamidine bromoformidium, and methylammonium chloride in a second solvent in a predetermined ratio to obtain a second solution, wherein the second solvent is selected from at least one of ethanol, isopropanol, N,N-dimethylformamide, and dimethyl sulfoxide; applying the second solution onto the mesoporous composite film using any one of spin coating, slot coating, or blade coating; and annealing the mesoporous composite film coated with the second solution.

[0015] In some embodiments, before applying the second solution to the mesoporous composite film, the method further includes filtering out impurities in the second solution using a polytetrafluoroethylene filter head with a diameter of 0.22 micrometers.

[0016] Secondly, this application provides a method for fabricating a perovskite / silicon tandem solar cell, the method comprising:

[0017] A hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, an electrode layer, and an antireflection layer are sequentially fabricated on a crystalline silicon bottom cell. The electrode layer includes a top electrode layer and a bottom electrode layer. The top electrode layer is disposed above the buffer layer, and the bottom electrode layer is disposed below the crystalline silicon bottom cell. The perovskite thin film is fabricated using any of the perovskite thin film fabrication methods described in the first aspect.

[0018] Thirdly, embodiments of this application provide a perovskite / silicon tandem solar cell, which includes a bottom electrode layer, a crystalline silicon bottom cell, a hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, a top electrode layer, and an antireflection layer stacked sequentially. The perovskite thin film is prepared using any of the perovskite thin film preparation methods described in the first aspect.

[0019] As can be seen in the embodiments of this application, an inorganic composite lead iodide / cesium bromide film is obtained by treating an inorganic composite lead iodide / cesium bromide film with a fused bicyclic compound solution containing a thiophene-pyrazole bicyclic structure. An ammonium salt layer is then prepared on the composite film and annealed to form a perovskite film. The fused bicyclic heterocyclic compound solution can promote the recrystallization of lead iodide. The sulfur / nitrogen atoms of the thiophene-pyrazole bicyclic ring strongly coordinate with lead ions to form a stable five-membered ring chelate, which delays the nucleation of lead iodide. At the same time, the rigid structure of the bicyclic ring hinders the layered stacking and synergistically forms vertically oriented nanopores, providing channels for the diffusion of ammonium salt. The R2 long-chain alkyl group is orderly stacked on the perovskite (001) crystal plane through hydrophobic segments, which significantly reduces the surface energy of the crystal plane. The reduced surface energy makes the crystal nucleation preferentially select the (001) plane, forming an orderly growth of the vertical substrate, thereby effectively improving the quality of the perovskite polycrystalline film. The R1 group forms hydrogen bonds with the perovskite A-site cations and halide ions, which inhibits ion escape during annealing, reduces defect formation, and optimizes the performance of the film and the tandem battery. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart of a method for preparing a perovskite thin film according to an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the composition structure of a perovskite / silicon tandem solar cell provided in an embodiment of this application;

[0023] Figure 3 This is a schematic flowchart of a method for fabricating a perovskite / silicon tandem solar cell provided in an embodiment of this application;

[0024] Figure 4 These are X-ray diffraction data images of a perovskite thin film of Example 1 and Comparative Example 1 provided in this application.

[0025] Figure 5 These are photoluminescence spectra of Embodiment 1 and Comparative Example 1 provided in this application;

[0026] Figure 6 This is a JV curve diagram of a battery device of Embodiment 2 and Comparative Example 2 provided in this application. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0028] In a first aspect, embodiments of this application provide a method for preparing a perovskite thin film, which can be specifically used to prepare such a perovskite thin film. Figure 2 The perovskite thin film in the perovskite solar cell shown may specifically include a bottom electrode layer 17, a crystalline silicon bottom cell 10, a hole transport layer 11, a perovskite thin film 12, a passivation layer 13, an electron transport layer 14, a buffer layer 15, a top electrode layer 16, and an antireflection layer 18, which are stacked sequentially. Please refer to... Figure 1 The preparation method of this perovskite thin film may specifically include the following steps S101-S103:

[0029] In step S101, lead iodide and cesium bromide are deposited on a crystalline silicon bottom cell by thermal evaporation to obtain an inorganic composite film.

[0030] Specifically, in step S101, a conformal deposition process can be used to form an inorganic composite thin film.

[0031] In some embodiments, the ratio of lead iodide to cesium bromide in the inorganic composite film is 3:1 to 9:1, and the thickness of the inorganic composite film is 100-600 nm.

[0032] Specifically, in the preparation of inorganic composite thin films, the ratio of lead iodide to cesium bromide and the thickness of the inorganic composite thin film can be controlled by adjusting the evaporation rates of lead iodide and cesium bromide. For example, the evaporation rate of lead iodide can be controlled at 8 Å / s, and the evaporation rate of cesium bromide at 2 Å / s, and the evaporation can be stopped when the thickness of the inorganic composite thin film reaches 300 nm.

[0033] Of course, in practical applications, the evaporation rates of lead iodide and cesium bromide can also be set to other evaporation rates. For example, the evaporation rates of lead iodide and cesium bromide can be set to 6 Å / s and 2 Å / s, respectively, so that the ratio of lead iodide to cesium bromide is 3:1. The thickness of the inorganic composite film can also be set to other values ​​different from 300 nm, such as 600 nm. No specific restrictions are imposed here.

[0034] It is evident that by controlling the ratio of lead iodide and cesium bromide, as well as the thickness of the inorganic composite film, the requirements for subsequent mesoporous structure formation can be met, providing a suitable base film for the function of fused bicyclic compounds, which helps to reduce the problem of incomplete reaction caused by improper composition or thickness.

[0035] Specifically, in combination Figure 2Regarding the perovskite solar cell structure shown, when preparing the perovskite solar cell, a hole transport layer can be prepared first on a crystalline silicon substrate, and then an inorganic composite film can be prepared on the hole transport layer. The inorganic composite film is then processed through subsequent steps S102 and S103 to obtain a perovskite film. Subsequently, a passivation layer, an electron transport layer, a buffer layer, an electrode layer, and an antireflection layer are prepared sequentially on the perovskite film to obtain a perovskite / silicon tandem solar cell.

[0036] Step S102: The inorganic composite film is treated with a first solution to obtain a mesoporous composite film.

[0037] The first solution comprises a fused bicyclic compound and a first solvent, wherein the fused bicyclic compound has the following general structural formula: The R1 group is selected from one of amino (-NH2), phosphonic acid (-PO3H2), carboxyl (-COOH), and fluorine (-F), and the R2 is selected from one of C2-10 alkyl carbon chains. The first solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), 2-methoxyethanol (2-Me), n-butanol, isobutanol, isopropanol, ethanol, methanol, and acetonitrile.

[0038] The fused bicyclic heterocyclic compound solution (i.e., the first solution) can partially dissolve lead iodide and promote its recrystallization. Specifically, the sulfur / nitrogen atoms of the thiophene-pyrazole bicyclic ring are strongly coordinated with lead ions to form a stable five-membered ring chelate, which slows down the nucleation rate of lead iodide. At the same time, the rigid bicyclic structure can prevent the layered stacking of lead iodide and form vertically oriented nanopores, providing diffusion channels for subsequent ammonium salts, promoting the reaction between ammonium salts and lead iodide, and thus optimizing the final perovskite film formation quality.

[0039] In some embodiments, the first solvent may specifically include at least one of 2-methoxyethanol, n-butanol, isobutanol, isopropanol, ethanol, methanol, and N-methylpyrrolidone, and the concentration of the first solution is 0.1-100 mg / ml.

[0040] In other words, the first solvent can specifically be a mixture of NMP and an alcohol. Of course, in other embodiments, the first solvent can be other forms of solvent, such as a mixture of DMF and an alcohol; no specific limitation is made here. By selecting the components and solution concentration in the first solvent, it is beneficial to ensure the full dissolution of the fused bicyclic compound, optimize its interaction with the inorganic composite film, provide a suitable basic environment for the uniform formation of the mesoporous structure, and ensure the stability of subsequent processing effects.

[0041] In some embodiments, treating the inorganic composite film with the first solution includes: applying the first solution onto the inorganic composite film using any one of spin coating, blade coating, spray coating, or slot coating; and performing gradient annealing on the inorganic composite film coated with the first solution.

[0042] Specifically, the gradient annealing process can be: first annealing at 70°C for 3 minutes, then annealing at 150°C for 10 minutes.

[0043] It is evident that gradient annealing, employed during the formation of mesoporous structures, promotes the dissolution and recombination of lead iodide in the low-temperature stage and induces directional shrinkage of pores in the high-temperature stage, preventing collapse and enhancing the stability of the mesoporous structure, thus facilitating the subsequent reaction between organic ammonium salts and inorganic composite films.

[0044] Step S103: An ammonium salt layer is prepared on the mesoporous composite film and annealed to obtain the perovskite film.

[0045] In this process, the long-chain alkyl group R2 of the fused bicyclic heterocyclic compound can be orderedly stacked on the perovskite film crystal face (001 face) through hydrophobic segments, reducing the surface energy of the perovskite film crystal face. This reduced surface energy leads to preferential nucleation of the crystal on the 001 face, resulting in ordered growth perpendicular to the substrate and thus improving the quality of the perovskite polycrystalline film. Furthermore, the R1 group forms hydrogen bonds with the perovskite A-site cations and halide ions, suppressing ion escape during annealing and reducing vacancy defects. Simultaneously, the fused bicyclic heterocyclic compound is not easily volatile, and its carboxyl group (C=O) and carbon-sulfur bicyclic ring can coordinate with lead ions, thereby passivating unreacted lead ion defects and further enhancing battery performance.

[0046] In some embodiments, the preparation of the ammonium salt layer on the mesoporous composite film includes: dissolving formamidine iodoformidium (FAI), formamidine bromoformidium (FABr), and methylammonium chloride (MACl) in a second solvent in a predetermined ratio to obtain a second solution, wherein the second solvent is selected from at least one of ethanol, isopropanol, N,N-dimethylformamide, and dimethyl sulfoxide; applying the second solution onto the mesoporous composite film using any one of spin coating, slot coating, or blade coating; and annealing the mesoporous composite film coated with the second solution.

[0047] Specifically, before applying the second solution to the mesoporous composite film, the method further includes filtering out impurities in the second solution using a polytetrafluoroethylene filter head with a diameter of 0.22 micrometers.

[0048] Secondly, embodiments of this application also provide a method for fabricating perovskite / silicon tandem solar cells, please refer to... Figure 3 The fabrication method of this perovskite / silicon tandem solar cell may specifically include the following step S301:

[0049] Step S301: A hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, an electrode layer, and an antireflection layer are sequentially fabricated on a crystalline silicon bottom cell. The electrode layer includes a top electrode layer and a bottom electrode layer. The top electrode layer is disposed above the buffer layer, and the bottom electrode layer is disposed below the crystalline silicon bottom cell. The perovskite thin film is fabricated using the perovskite thin film fabrication method described in the first aspect above.

[0050] Specifically, the top electrode layer may include a transparent electrode layer and a front electrode (specifically, a metal grid line), while the bottom electrode layer may be a metal electrode layer (i.e., a back-contact metal electrode). In fabricating the electrode layers, the transparent electrode layer can be fabricated first on the buffer layer, followed by the metal grid line and the bottom metal electrode layer. Considering the light incident direction, the front electrode is fabricated on top of the transparent electrode layer, and the bottom metal electrode layer is attached to the lower surface of the crystalline silicon base cell. The final perovskite / silicon tandem solar cell may include, from bottom to top, a bottom metal electrode layer, a crystalline silicon base cell, a hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, a transparent electrode layer, metal grid lines, and an anti-reflection layer, stacked sequentially.

[0051] Thirdly, this application also provides a perovskite / silicon tandem solar cell (perovskite / silicon two-terminal tandem solar cell), please refer to... Figure 2 The perovskite solar cell may specifically include a bottom electrode layer 17, a crystalline silicon bottom cell 10, a hole transport layer 11, a perovskite thin film 12, a passivation layer 13, an electron transport layer 14, a buffer layer 15, a top electrode layer 16, and an anti-reflection layer 18 stacked sequentially. The perovskite thin film is prepared by the perovskite thin film preparation method described in the first aspect above.

[0052] Specifically, the top electrode layer 16 may include a transparent electrode layer and a front electrode (i.e., metal grid lines), and the bottom electrode layer may specifically be a metal electrode layer. That is, the perovskite solar cell may specifically include, in sequence, a bottom metal electrode layer, a crystalline silicon bottom cell, a hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, a transparent electrode layer, metal grid lines, and an anti-reflection layer.

[0053] Specifically, the crystalline silicon substrate can be a textured crystalline silicon substrate, and the perovskite solar cell can be a perovskite / crystalline silicon tandem solar cell.

[0054] Furthermore, in specific implementations, the perovskite thin film preparation method and the perovskite / silicon tandem cell preparation method of this application can also be applied to the preparation process of perovskite and other photovoltaic cell tandem cells. For example, they can be applied to the preparation process of perovskite / perovskite tandem cells, perovskite / cadmium telluride tandem cells, perovskite / copper indium gallium selenide tandem cells, and perovskite / gallium arsenide tandem cells, using the perovskite thin film preparation method of this application to prepare the perovskite thin film of each of the aforementioned tandem cells.

[0055] Furthermore, each of the aforementioned stacked batteries can be a pair of stacked batteries connected in series, or a single battery, a three-cell battery, or other multiple batteries; no specific restrictions are imposed here.

[0056] As can be seen, in this embodiment, an inorganic composite lead iodide / cesium bromide film is treated with a fused bicyclic compound solution containing a thiophene-pyrazole bicyclic structure to obtain a mesoporous composite film, on which an ammonium salt layer is then prepared and annealed to form a perovskite film. The fused bicyclic heterocyclic compound solution can promote the recrystallization of lead iodide. The sulfur / nitrogen atoms of the thiophene-pyrazole bicyclic ring strongly coordinate with lead ions to form a stable five-membered ring chelate, which delays the nucleation of lead iodide. At the same time, the rigid structure of the bicyclic ring hinders the layered stacking and synergistically forms vertically oriented nanopores, providing channels for the diffusion of ammonium salt. The R2 long-chain alkyl group is orderly stacked on the perovskite (001) crystal plane through hydrophobic segments, which significantly reduces the surface energy of the crystal plane. The reduced surface energy makes the crystal nucleation preferentially select the (001) plane, forming an orderly growth of the vertical substrate, thereby effectively improving the quality of the perovskite polycrystalline film. The R1 group forms hydrogen bonds with the perovskite A-site cations and halide ions, inhibiting ion escape during annealing, reducing defect formation, and optimizing the performance of the film and the tandem battery.

[0057] The following specific embodiments illustrate the solution of this application. It should be noted that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application.

[0058] Example 1 (Preparation method of perovskite thin film):

[0059] Step 1, select a size of 2*2cm 2 For FTO glass, use dish soap to remove stains from the glass surface, rinse the dish soap off with tap water, then sonicate with deionized water, ethanol, and acetone for 20 minutes each, and then bake in a vacuum drying oven at 100°C for 1 hour.

[0060] Step 2: Place the cleaned FTO in a UV ozone generator for 20 minutes. Then, place the treated FTO into a vapor deposition machine with a vacuum level of 10. -4 Evaporation begins when the pressure is below Pa, with the evaporation rate of lead iodide controlled at 8 Å / s and the evaporation rate of cesium bromide at 2 Å / s. Evaporation is stopped when the thickness of the inorganic composite film reaches 300 nm.

[0061] Step 3: Prepare a solution of fused bicyclic heterocyclic compound (R1 group is -PO3H2, R2 is C8 alkyl carbon chain) (i.e., the first solution). The first solvent is a mixed solution of n-butanol and NMP (volume ratio of n-butanol:NMP = 7:3). The concentration of the first solution is 1.5 mg / ml. Then heat to 50°C and stir to dissolve for 2 hours. After the solution is dissolved, filter the solution with a 0.22 μm polytetrafluoroethylene filter. Then take out the inorganic composite film from step 2 and use the first solution to spin-coat the surface of the inorganic composite film. The spin-coating process is 3000 rpm for 20 seconds, first annealing at 70°C for 3 minutes, then annealing at 150°C for 10 minutes to obtain a mesoporous composite film.

[0062] Step 4: Dissolve FAI and FABr in a 6:1 molar ratio, with MACl added at 30% of the molar amounts of FAI and FABr, in the second solvent ethanol to prepare a second solution with a concentration of 0.6 mol / L. Spin-coat the ammonium salt solution (second solution) onto the surface of the mesoporous composite film obtained in Step 3 at a spin speed of 2000-6000 rpm for 10-60 seconds. Immediately after spin-coating, anneal at 150°C for 20 minutes to obtain the perovskite film.

[0063] Comparative Example 1:

[0064] Step 1, select a size of 2*2cm 2 For FTO glass, use dish soap to remove stains from the glass surface, rinse the dish soap off with tap water, then sonicate with deionized water, ethanol, and acetone for 20 minutes each, and then bake in a vacuum drying oven at 100°C for 1 hour.

[0065] Step 2: After cleaning the FTO, place it in a UV ozone generator for 20 minutes, then place it in a vapor deposition machine with a vacuum degree of 10. -4 Evaporation begins when the pressure is below Pa. The evaporation rate of lead iodide is controlled at 8 Å / s, and the evaporation rate of cesium bromide is controlled at 2 Å / s. Evaporation is stopped when the film thickness reaches 300 nm. The film is then removed to obtain the mixed film.

[0066] Step 3: Dissolve FAI and FABr in ethanol at a molar ratio of 6:1, with MACl added at 30% of the molar amounts of FAI and FABr, to prepare a 0.6 mol / L solution. Spin-coat the ammonium salt solution onto the film surface from Step 2 at a spin speed of 2000-6000 rpm for 10-60 seconds. Immediately after spin-coating, anneal at 150°C for 20 minutes to obtain a perovskite film.

[0067] Please refer to Figure 4 , Figure 4 The images show X-ray diffraction (XRD) data of the perovskite thin films of Example 1 and Comparative Example 1, provided by [the relevant authority / organization]. Figure 4 It can be seen that, compared with Comparative Example 1, after treatment with the first solution, there is no diffraction peak of lead iodide in the perovskite film of Example 1, that is, lead iodide has been converted into perovskite. In other words, the perovskite film preparation method provided by the present application is conducive to promoting the reaction of lead iodide and ammonium salt in the inorganic composite film. In contrast, Comparative Example 1 has a strong diffraction peak at 12.7° (the diffraction peak of lead iodide), indicating that there is more lead iodide remaining in the perovskite film. Moreover, the diffraction peak intensity of Example 1 at 14.07° on the 001 crystal plane is greater than that of Comparative Example 1, indicating that the 001 plane orientation crystallization of the perovskite film of Example 1 is stronger, which is beneficial to improving the photovoltaic performance of the device.

[0068] Additionally, please refer to Figure 5 , Figure 5 The photoluminescence spectra of Example 1 and Comparative Example 1 are provided by... Figure 5 It can be seen that, compared with Comparative Example 1, the photoluminescence intensity of Example 1 is much higher than that of Comparative Example 1, indicating that after the first solution treatment, the defects of the perovskite film are reduced and the quality is improved.

[0069] Example 2 (Preparation method of perovskite / silicon tandem solar cell):

[0070] Step 1: Cut the commercially available textured silicon substrate into 2*2cm pieces. 2 The substrates of various sizes were cleaned with deionized water and ethanol, and then dried.

[0071] Step 2: Place the cleaned substrate in a UV ozone generator for 20 minutes, then transfer the substrate to a PVD environment and sputter a nickel oxide hole transport layer (HTL) at a sputtering power of 30W. The vacuum level should be less than 2*10⁻⁶. -4 Pre-sputtering begins at Pa for 10 minutes, then the metal baffle is opened, and nickel oxide is sputtered to a thickness of 8-20 nm. After sputtering is completed, the substrate is removed and annealed at 200 °C for 30 minutes.

[0072] Step 3: Place the substrate with the hole transport layer prepared in Step 2 into a vapor deposition machine, and achieve a vacuum level of 10. -4 Evaporation begins when the pressure is below Pa, with the evaporation rate of lead iodide controlled at 8 Å / s and the evaporation rate of cesium bromide at 2 Å / s. Evaporation is stopped when the inorganic composite film thickness reaches 300 nm, and then the battery device with the prepared inorganic composite film is taken out.

[0073] Step 4: Prepare a solution of fused bicyclic heterocyclic compound (R1 is PO3H2, R2 is an 8-carbon alkyl chain) (i.e., the first solution). The first solvent is a mixture of n-butanol and NMP (volume ratio of n-butanol:NMP = 7:3). The concentration of the first solution is 1.5 mg / ml. Then heat to 50°C and stir to dissolve for 2 hours. After the fused bicyclic heterocyclic compound is dissolved, filter it with a 0.22 μm polytetrafluoroethylene filter head. Use the filtered first solution to spin coat the surface of the inorganic composite membrane obtained in step 3. The spin coating process is 3000 rpm for 20 s, anneal at 70°C for 3 min, and then anneal at 150°C for 10 min to obtain a mesoporous composite film.

[0074] Step 5: Dissolve FAI and FABr in a 6:1 molar ratio, with MACl added at 30% of the molar amounts of FAI and FABr, in the second solvent ethanol to prepare a second solution with a concentration of 0.6 mol / L. Spin-coat the ammonium salt solution (i.e., the second solution) onto the surface of the mesoporous composite film obtained in Step 4 at a spin speed of 2000-6000 rpm for 10-60 seconds. Immediately after spin-coating, anneal at 150°C for 20 minutes to obtain the perovskite film.

[0075] Step 6: Prepare a 2 mg / ml phenethylamine iodine solution in isopropanol. After dissolving, filter the solution and spin-coat the filtrate onto the surface of the perovskite film obtained in Step 5. Then anneal at 100°C for 5 min.

[0076] Step 7: Transfer the thin-film battery device obtained in Step 6 to an evaporation machine and evaporate C. 60 Electron transport layer, C 60 The vapor deposition process conditions are as follows: the vacuum degree required for vapor deposition is below 10. -4 Pa, evaporation rate of 0.1-0.5 Å / s, film thickness of 15-30 nm, and after evaporation, the cavity is broken to remove the thin film battery structure.

[0077] Step 8: Transfer the thin-film battery device obtained in Step 7 to the ALD to prepare a tin dioxide (SnO2) buffer layer. The tin source is tetramethylaminotin (TDMASn), and the oxygen source is deionized water. The deposition is carried out at 85°C. The preparation process is as follows: tin source purging for 0.2s, nitrogen purging for 3s, water source purging for 0.2s, and nitrogen purging for 3s constitute one cycle. The total deposition thickness is 10nm.

[0078] Step 9: Transfer the thin-film battery device obtained in Step 8 to PVD to fabricate a transparent conductive electrode. The sputtering conditions are: when the vacuum degree reaches 5*10 -3 Sputtering begins at Pa, with a sputtering power of 50W and a sputtering temperature of room temperature. Pre-sputtering is performed for 5 minutes before sputtering, and the sputtering time is 40 minutes, with a sputtering thickness of 60nm.

[0079] Step 10: Transfer the thin-film battery device obtained in Step 9 to a vapor deposition machine to vapor deposit the front electrode and the back electrode (i.e., the bottom metal electrode layer). The vapor deposition material is silver, the vapor deposition rate is 0.1-1.5 Å / s, the thickness of the silver gate electrode is 300 nm, and the thickness of the back electrode is 150 nm.

[0080] Step 11: Deposit a MgF2 antireflection layer onto the silver grid electrode surface (i.e., the front electrode) of the thin-film battery device obtained in Step 10. The deposition process conditions are: deposition rate of 0.5-1.0 Å / s and deposition film thickness of 120 nm.

[0081] Comparative Example 2:

[0082] Step 1: Cut the commercially available textured silicon substrate into 2*2cm pieces. 2 The substrates of various sizes were cleaned with deionized water and ethanol, and then dried.

[0083] Step 2: Place the cleaned substrate in a UV ozone generator for 20 minutes, then transfer the substrate to a PVD environment and sputter a nickel oxide hole transport layer (HTL) at a sputtering power of 30W. The vacuum level should be less than 2*10⁻⁶. -4 Pre-sputtering begins at Pa for 10 minutes, then the metal baffle is opened, and nickel oxide is sputtered to a thickness of 8-20 nm. After sputtering is completed, the substrate is removed and annealed at 200 °C for 30 minutes.

[0084] Step 3: Place the thin-film battery device prepared in Step 2 into a vapor deposition machine, and ensure the vacuum level reaches 10. -4 Evaporation begins when the pressure is below Pa. The evaporation rate of lead iodide is controlled at 8 Å / s, and the evaporation rate of cesium bromide is controlled at 2 Å / s. Evaporation is stopped when the film thickness reaches 300 nm. The film is then removed to obtain a hybrid film.

[0085] Step 4: Dissolve FAI and FABr in ethanol at a molar ratio of 6:1, with MACl added at 30% of the molar amounts of FAI and FABr, to prepare a 0.6 mol / L solution. Spin-coat the ammonium salt solution onto the film surface from Step 3 at a spin speed of 2000-6000 rpm for 10-60 seconds. Immediately after spin-coating, anneal at 150°C for 20 minutes to obtain a perovskite film.

[0086] Step 5: Prepare a 2 mg / ml phenethylamine iodine solution in isopropanol. After complete dissolution, filter the solution and spin-coat the perovskite film surface from Step 4. Then anneal at 100°C for 5 min.

[0087] Step 6: Transfer the thin-film battery device obtained in Step 5 to an evaporation machine and evaporate C.60 Electron transport layer, C 60 The vapor deposition process conditions are as follows: the vacuum degree required for vapor deposition is below 10. -4 Pa, evaporation rate of 0.1-0.5 Å / s, film thickness of 15-30 nm, and the film is removed after evaporation is completed by breaking the cavity.

[0088] Step 7: Transfer the thin-film battery device obtained in Step 6 to the ALD to prepare a tin dioxide (SnO2) buffer layer. The tin source is tetramethylaminotin (TDMASn), and the oxygen source is deionized water. The deposition is carried out at 85°C. The preparation process is as follows: tin source purging for 0.2s, nitrogen purging for 3s, water source purging for 0.2s, and nitrogen purging for 3s constitute one cycle. The total deposition thickness is 10nm.

[0089] Step 8: Transfer the thin-film battery device obtained in Step 7 to PVD to fabricate a transparent conductive electrode. The sputtering conditions are: when the vacuum degree reaches 5*10 -3 Sputtering begins at Pa, with a sputtering power of 50W and a sputtering temperature of room temperature. Pre-sputtering is performed for 5 minutes before sputtering, and the sputtering time is 40 minutes, with a sputtering thickness of 60nm.

[0090] Step 9: Transfer the thin-film battery device obtained in Step 8 to a vapor deposition machine to vapor deposit the front electrode and the back electrode. The vapor deposition material is silver, the vapor deposition rate is 0.1-1.5 Å / s, the thickness of the silver gate electrode is 300 nm, and the thickness of the back electrode is 150 nm.

[0091] Step 10: Evaporate a MgF2 antireflection layer onto the silver grid electrode surface of the thin-film battery device obtained in Step 9. The evaporation process conditions are: evaporation rate of 0.5-1.0 Å / s and evaporation film thickness of 120 nm.

[0092] Please refer to Figure 6 , Figure 6 These are the JV curves of the battery devices in Example 2 and Comparative Example 2. Specifically, Figure 6 The battery devices obtained in Example 2 and Comparative Example 2 were tested under standard sunlight simulation (100mW / cm²). 2 The JV curve obtained from the test under simulated sunlight (AM1.5) is shown in Table 1 below, referring to the test data recorded therein:

[0093] Table 1. Test data for Example 2 and Comparative Example 2

[0094] Open circuit voltage (V) <![CDATA[Short-circuit current density (mA·cm -2 )]]> Fill factor (%) Photoelectric conversion efficiency (%) Comparative Example 2 1.76 19.14 74.12 24.97 Example 2 1.91 20.27 80.67 31.23

[0095] It can be seen that the battery device obtained in Example 2 achieved a photoelectric conversion efficiency of 31.23%, while Comparative Example 2 achieved a photoelectric conversion efficiency of 24.97%. In other words, compared with Comparative Example 2, the electrical performance of Example 2 is significantly improved, that is, after the first solution treatment, the defects of the perovskite thin film are passivated, thereby improving the photoelectric performance of the device.

[0096] In summary, taking an example where R1 is a phosphonic acid group, R2 is a C8 alkyl carbon chain, the first solvent is a mixed solvent of n-butanol and N-methylpyrrolidone in a volume ratio of 7:3, and the first solution concentration is 1.5 mg / ml, this application uses a fused bicyclic compound including the aforementioned groups and structures. By treating the inorganic composite film in the perovskite film preparation process with a first solution based on the aforementioned solvent ratio and solution concentration, it is beneficial to improve the quality of the perovskite film and the battery performance.

[0097] Unless otherwise stated, all terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. All patents and publications referenced in this application are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this application but do not exclude other contents.

[0098] In the description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0099] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes and modifications to the above embodiments within the scope of this application.

Claims

1. A method for preparing a perovskite thin film, characterized in that, The method for preparing the perovskite thin film includes: Inorganic composite films were obtained by depositing lead iodide and cesium bromide on crystalline silicon bottom cells via thermal evaporation. The inorganic composite film is treated with a first solution to obtain a mesoporous composite film. The first solution comprises a fused bicyclic compound and a first solvent. The general formula of the fused bicyclic compound is: The R1 group is selected from one of amino, phosphonic acid, carboxyl, and fluorine; the R2 is selected from one of C2-10 alkyl carbon chains; and the first solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, 2-methoxyethanol, n-butanol, isobutanol, isopropanol, ethanol, methanol, and acetonitrile. An ammonium salt layer was prepared on the mesoporous composite film and then annealed to obtain the perovskite film.

2. The method according to claim 1, characterized in that, The first solvent includes at least one of 2-methoxyethanol, n-butanol, isobutanol, isopropanol, ethanol, methanol, and N-methylpyrrolidone, and the concentration of the first solution is 0.1-100 mg / ml.

3. The method according to claim 1, characterized in that, The R1 group includes a phosphonic acid group, the R2 includes a C8 alkyl carbon chain, the first solvent is a mixed solvent of n-butanol and N-methylpyrrolidone in a volume ratio of 7:3, and the concentration of the first solution is 1.5 mg / ml.

4. The method according to any one of claims 1-3, characterized in that, The ratio of lead iodide to cesium bromide in the inorganic composite film is 3:1 to 9:1, and the thickness of the inorganic composite film is 100-600 nm.

5. The method according to any one of claims 1-3, characterized in that, The treatment of the inorganic composite film with the first solution includes: The first solution is applied to the inorganic composite film using any one of the following methods: spin coating, blade coating, spray coating, or slot coating. The inorganic composite film coated with the first solution is subjected to gradient annealing.

6. The method according to claim 5, characterized in that, The gradient annealing process includes: Anneal at 70℃ for 3 minutes, then anneal at 150℃ for 10 minutes.

7. The method according to any one of claims 1-3, characterized in that, The preparation of the ammonium salt layer on the mesoporous composite film includes: Iodoformamidine, bromamide and methylammonium chloride are dissolved in a second solvent in a predetermined ratio to obtain a second solution. The second solvent is selected from at least one of ethanol, isopropanol, N,N-dimethylformamide and dimethyl sulfoxide. The second solution is applied to the mesoporous composite film using any one of spin coating, slot coating, or blade coating. The mesoporous composite film coated with the second solution is annealed.

8. The method according to claim 7, characterized in that, Before applying the second solution onto the mesoporous composite film, the method further includes: Impurities in the second solution were removed using a polytetrafluoroethylene filter head with a diameter of 0.22 micrometers.

9. A method for fabricating a perovskite / silicon tandem solar cell, characterized in that, The fabrication method of the perovskite / silicon tandem solar cell includes: A hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, an electrode layer, and an antireflection layer are sequentially fabricated on a crystalline silicon bottom cell. The electrode layer includes a top electrode layer and a bottom electrode layer. The top electrode layer is disposed above the buffer layer, and the bottom electrode layer is disposed below the crystalline silicon bottom cell. The perovskite thin film is fabricated using the perovskite thin film preparation method according to any one of claims 1-8.

10. A perovskite / silicon tandem solar cell, characterized in that, The perovskite / silicon tandem solar cell comprises a bottom electrode layer, a crystalline silicon bottom cell, a hole transport layer, a perovskite thin film, a passivation layer, an electron transport layer, a buffer layer, a top electrode layer, and an antireflection layer, which are stacked sequentially. The perovskite thin film is prepared by the method described in any one of claims 1-8.

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