B-site Cd-doped two-dimensional perovskite thin film and perovskite / crystalline silicon laminated solar cell

Abstract

The invention provides a B-site Cd-doped two-dimensional perovskite thin film and a perovskite / crystalline silicon laminated solar cell, and belongs to the technical field of solar cells. By regulating and controlling the chemical components of the two-dimensional perovskite, two key targets are achieved: on one hand, Pb is partially replaced by Cd, the band gap is precisely regulated and controlled to be within the range of 1.6-1.8 eV, and the spectral absorption requirement of the laminated top cell is met; and on the other hand, the layered structure is stabilized by R-site and A-site mixed cations, and meanwhile, the charge transport performance is optimized through Cd and Pb orbital hybridization, so that the stability of the film is improved, and the preparation process environment of a silicon substrate is adapted. Finally, the two-dimensional perovskite thin film is used as a top cell light absorption layer of a perovskite / crystalline silicon laminated solar cell, the problems that an existing laminated device is not matched in band gap, insufficient in stability and poor in compatibility with a silicon substrate are solved, and a key material and a preparation method support are provided for industrialization promotion of a laminated photovoltaic technology.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a B-site Cd-doped two-dimensional perovskite thin film and a perovskite / crystalline silicon tandem solar cell. Background Technology

[0002] In the process of upgrading photovoltaic technology towards higher efficiency and higher stability, perovskite / crystalline silicon tandem solar cells, with their synergistic advantage of "perovskite top cell absorbing short-wave visible light + silicon bottom cell absorbing long-wave infrared light," have become a core direction for breaking through the efficiency ceiling of single-junction silicon cells. Currently, the highest efficiency in the laboratory has exceeded 35%, making it a key research and development area for next-generation commercial photovoltaic devices. Among them, the top cell light absorption layer, as a key component of the tandem structure, must simultaneously meet three major requirements: "precise bandgap matching (1.6~1.8 eV, to avoid spectral overlap with the silicon bottom cell)," "high environmental stability (withstanding the medium temperature and humidity conditions during silicon cell fabrication)," and "good compatibility with the silicon substrate." Quasi-two-dimensional perovskites, due to their excellent stability resulting from their layered structure, have become one of the preferred materials for top-mounted cells in perovskite / crystalline silicon tandem solar cells. In existing technologies, lead-based 2DRP perovskites have achieved initial applications in low-to-medium temperature solution preparation and flexible device integration by optimizing the crystallinity of the thin film through the control of the chain length of the organic cation layer (such as butylammonium BA and formamidinium FA). However, for the specific needs of perovskite / crystalline silicon tandem cells, technical bottlenecks such as bandgap mismatch, insufficient stability, and poor compatibility with silicon substrates still exist. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a B-site Cd-doped two-dimensional perovskite thin film and a perovskite / crystalline silicon tandem solar cell. The B-site Cd-doped two-dimensional perovskite thin film provided by this invention has a precisely tuned bandgap to the 1.6~1.8 eV range, exhibits good stability and silicon substrate compatibility, and when used as a light-absorbing layer in a perovskite / crystalline silicon tandem solar cell, it demonstrates high short-circuit current density and high photovoltaic efficiency.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a B-site Cd-doped two-dimensional perovskite thin film, wherein the chemical composition of the B-site Cd-doped two-dimensional perovskite is R2A. n-1 B n X 3n+1 , where n = 1, 2 or 3; The R site is an organic ammonium cation; The A site is one or more of the following: methylamine cation, formamidinium cation, and cesium cation; B position Cd 2+ With Pb 2+The mixture, wherein the molar content of Cd at site B is >0 and <100%; X is I - , or I - With Br - A mixture.

[0005] Preferably, the organic ammonium cation at the R position is one or more of the following: butammonium cation, 2-methoxyethylammonium cation, 2-methylthioethylammonium cation, benzylammonium cation, phenylethylammonium cation, and 2-thiophenemethylammonium cation.

[0006] Preferably, Cd in the B position 2+ With Pb 2+ The molar ratio is 1:1~3.

[0007] This invention provides a method for preparing the above-mentioned B-site Cd-doped two-dimensional perovskite thin film, comprising the following steps: Raw materials with chemical compositions of RX, AX, and BX are mixed with organic solvents to obtain perovskite slurry; The perovskite slurry was coated onto the substrate surface and annealed to obtain a B-site Cd-doped two-dimensional perovskite film.

[0008] Preferably, the annealing temperature is 100~150℃ and the time is 20~40min.

[0009] This invention provides the application of the above-mentioned B-site Cd-doped two-dimensional perovskite thin film in the light-absorbing layer of the top cell of a solar cell.

[0010] This invention provides a perovskite / crystalline silicon tandem solar cell, comprising a crystalline silicon bottom cell and a perovskite top cell stacked on the surface of the crystalline silicon bottom cell; The perovskite top solar cell comprises a tunneling composite layer, a hole or electron transport layer, a perovskite layer, an electron or hole transport layer, and a transparent electrode layer stacked sequentially; the perovskite layer is the aforementioned B-site Cd-doped two-dimensional perovskite thin film. The outermost layer of the crystalline silicon bottom cell and the perovskite top cell is provided with a metal gate.

[0011] Preferably, the crystalline silicon bottom cell is one of HJT cell, TOPCon cell, IBC / BC cell, and BSF cell.

[0012] Preferably, in the perovskite top solar cell, the material of the tunneling composite layer includes one or more of IZO, ITO and AZO, and the thickness is 2~100nm; The hole transport layer is made of one or more of SAM, nickel oxide, spiro-OMeTAD, and PTAA. The thickness of the perovskite layer is 400~2000 nm; The electron transport layer is made of PCBM, C 60 One or more of TiO2 and SnO2, wherein the thickness of the electron transport layer is 10~20nm; The transparent electrode layer is made of one or more of IZO, ITO and AZO, and has a thickness of 60~100nm.

[0013] This invention provides a method for fabricating the above-mentioned perovskite / crystalline silicon tandem solar cell, comprising the following steps: A tunneling composite layer, a hole or electron transport layer, a spin-coated perovskite layer, an electron or hole transport layer, and a transparent electrode layer are sequentially deposited on the surface of the crystalline silicon bottom cell to obtain a perovskite top cell. A metal gate is deposited on the outermost layer of the crystalline silicon bottom cell and the perovskite top cell to obtain a perovskite / crystalline silicon tandem solar cell.

[0014] This invention provides a B-site Cd-doped two-dimensional perovskite thin film, wherein the chemical composition of the B-site Cd-doped two-dimensional perovskite is R2A. n-1 B n X 3n+1 Where n = 1, 2, or 3; R site is an organic ammonium cation; A site is one or more of methylamine cation, formamidinium cation, and cesium cation; B site is Cd 2+ With Pb 2+ The mixture, wherein the molar content of Cd at the B site is >0 and <100%; the X site is I. - , or I - With Br - A mixture. This invention achieves two key objectives by controlling the chemical composition of two-dimensional perovskites: firstly, by utilizing Cd to partially replace Pb, Cd... 2+ Partially replaces Pb 2+ At that time, its 5s orbit was in line with I - The 5p orbital hybridization of the perovskite shifts the bottom conduction band energy level upwards, and the difference in ionic radius induces lattice contraction, weakening the quantum confinement effect. These two factors work synergistically to precisely tune the band gap to the 1.6–1.8 eV range, meeting the spectral absorption requirements of the tandem top-cell battery. On the other hand, the layered structure is stabilized through a triple synergistic effect using mixed cations at the R and A sites (such as BA / FA). Specifically, BA… + Long chains provide spatial support and hydrophobic protection, MA +Filling the voids alleviates steric strain, and the two components form a double hydrogen bond network with the inorganic layer, maintaining charge balance and jointly suppressing lattice distortion, ion migration, and moisture erosion. Simultaneously, the charge transport performance is optimized through Cd and Pb orbital hybridization, improving both the film's inherent stability and adapting to the silicon substrate fabrication process environment. Ultimately, this two-dimensional perovskite film is used as the top-cell light-absorbing layer in a perovskite / crystalline silicon tandem solar cell, solving the problems of "bandgap mismatch and insufficient stability" in existing tandem devices, and providing key material support for the industrialization of tandem photovoltaic technology. The results of the examples show that the BA2(FA)(Pb) obtained in this invention... 1 / 2 Cd 1 / 2 The short-circuit current density of 2I7 at a thickness of 1μm ( J sc ) up to 20.5 mA / cm 2 (far higher than the 12.50 mA / cm² of pure lead-based) 2 The bandgap narrows from 2.19 eV to 1.55 eV, limiting the maximum photoelectric efficiency (PEP). η This can be increased to 30%. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the perovskite / crystalline silicon tandem solar cell in Example 1. Detailed Implementation

[0016] This invention provides a B-site Cd-doped two-dimensional perovskite thin film, wherein the chemical composition of the B-site Cd-doped two-dimensional perovskite is R2A. n-1 B n X 3n+1 , where n = 1, 2 or 3; The R site is an organic ammonium cation; The A site is one or more of the following: methylamine cation, formamidinium cation, and cesium cation; B position Cd 2+ With Pb 2+ The mixture, wherein the molar content of Cd at site B is >0 and <100%; X is I - , or I - With Br - A mixture.

[0017] In this invention, the organic ammonium cation at the R position is preferably one or more of butammonium cation, 2-methoxyethylammonium cation, 2-methylthioethylammonium cation, benzylammonium cation, phenylethylammonium cation and 2-thiophenemethylammonium cation.

[0018] In this invention, the structural formula of the organic ammonium cation is shown below: .

[0019] In this invention, the A site is one or more of methylamine cation, formamidinium cation and cesium cation, preferably formamidinium cation.

[0020] In this invention, the B-position Cd 2+ With Pb 2+ The mixture, wherein the molar content of Cd at the B site is >0 and <100%. In this invention, the Cd content at the B site... 2+ With Pb 2+ The preferred molar ratio is 1:1 to 3, specifically 1:1, 1:2 or 1:3.

[0021] In this invention, the X bit is I. - , or I - With Br - The mixture, the I - With Br - In the mixture, Br - The preferred molar content is ≤5%.

[0022] In this invention, the chemical composition of the B-site Cd-doped two-dimensional perovskite is further preferably R2A(Cd) x Pb 1-x )2I7, x is 1 / 4 to 1 / 2.

[0023] This invention provides a method for preparing the above-mentioned B-site Cd-doped two-dimensional perovskite thin film, comprising the following steps: Raw materials with chemical compositions of RX, AX, and BX are mixed with organic solvents to obtain perovskite slurry; The perovskite slurry was coated onto the substrate surface and annealed to obtain a B-site Cd-doped two-dimensional perovskite film.

[0024] This invention involves mixing raw materials with chemical compositions of RX, AX, and BX with an organic solvent to obtain a perovskite slurry. In this invention, the raw materials with chemical compositions of RX, AX, and BX, where RX represents an organic ammonium halide, specifically one or more of the following: butylamine hydroiodide, butylamine hydrobromide, 2-methoxyethylamine hydroiodide, 2-methoxyethylamine hydrobromide, 2-methylthioethylamine hydroiodide, 2-methylthioethylamine hydrobromide, benzylamine hydroiodide, benzylamine hydrobromide, phenylethylamine hydroiodide, phenylethylamine hydrobromide, 2-thiophenemethylamine hydroiodide, and 2-thiophenemethylamine hydrobromide.

[0025] AX represents one of methylamine iodine, formamidinium iodine, and cesium iodide; BX represents one or both of lead iodide and cadmium iodide.

[0026] In this invention, the organic solvent is preferably one or both of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), more preferably a DMF-DMSO mixture, wherein the volume ratio of DMF to DMSO in the DMF-DMSO mixture is preferably 4:1. In this invention, the concentration of perovskite in the perovskite slurry is preferably 1.6~2M.

[0027] After obtaining the perovskite slurry, the present invention coats the perovskite slurry onto the surface of a substrate and anneals it to obtain a B-site Cd-doped two-dimensional perovskite film. In this invention, the coating is preferably spin-coating, more preferably two-step spin-coating. The spin-coating speed of the first step is preferably 1000-2000 rpm, and the spin-coating time is preferably 5-10 s. The spin-coating speed of the second step is preferably 4000-6000 rpm, and the spin-coating time is preferably 30-40 s. In this invention, the spin-coating time for each step is determined based on the thickness of the B-site Cd-doped two-dimensional perovskite film.

[0028] In this invention, the annealing temperature is preferably 100°C, and the annealing time is preferably 20-40 min, more preferably 20-30 min. In this invention, the annealing atmosphere is preferably nitrogen.

[0029] In this invention, the thickness of the B-site Cd-doped two-dimensional perovskite film is preferably 400~2000 nm, more preferably 600~1000 nm, and even more preferably 700~800 nm.

[0030] This invention provides the application of the above-mentioned B-site Cd-doped two-dimensional perovskite thin film in the light-absorbing layer of the top cell of a solar cell.

[0031] This invention provides a perovskite / crystalline silicon tandem solar cell, comprising a crystalline silicon bottom cell and a perovskite top cell stacked on the surface of the crystalline silicon bottom cell; The perovskite top solar cell comprises a tunneling composite layer, a hole or electron transport layer, a perovskite layer, an electron or hole transport layer, and a transparent electrode layer stacked sequentially; the perovskite layer is the aforementioned B-site Cd-doped two-dimensional perovskite thin film. The outermost layer of the crystalline silicon bottom cell and the perovskite top cell is provided with a metal gate.

[0032] In this invention, the crystalline silicon bottom cell is preferably one of HJT cell, TOPCon cell, IBC / BC cell, and BSF cell.

[0033] In one specific embodiment of the present invention, the crystalline silicon bottom cell is an HJT cell, comprising a silicon wafer, an n-plane passivation layer deposited on one side of the silicon wafer, a p-plane passivation layer deposited on the other side of the silicon wafer, and a transparent conductive oxide layer located on the surface of the p-plane passivation layer. In this invention, the crystalline silicon bottom cell comprises a silicon wafer, preferably an N-type monocrystalline silicon wafer, and the thickness of the silicon wafer is preferably 100-200 μm, more preferably 150 μm. In this invention, the silicon wafer is preferably a texturized silicon wafer.

[0034] In this invention, the material of the n-plane passivation layer is preferably intrinsic amorphous silicon (a-Si:H) and n-type microcrystalline silicon (μc-Si:H). The thickness of the intrinsic amorphous silicon (a-Si:H) is preferably 5~15nm, more preferably 5~10nm, and the thickness of the n-type microcrystalline silicon (μc-Si:H) is preferably 5~10nm.

[0035] In this invention, the p-plane passivation layer is preferably an intrinsic amorphous silicon (a-Si:H) layer and a p-type microcrystalline silicon (μc-Si:H) layer. In this invention, the thickness of the intrinsic amorphous silicon (a-Si:H) layer is preferably 5~15 nm, more preferably 5~10 nm; the thickness of the p-type microcrystalline silicon (μc-Si:H) layer is preferably 5~10 nm.

[0036] In this invention, the material of the transparent conductive oxide layer preferably includes one or more of ITO, IZO and AZO, and the thickness is preferably 20~100nm, more preferably 50~100nm.

[0037] In this invention, the perovskite top solar cell comprises a tunneling composite layer, a hole or electron transport layer, a perovskite layer, an electron or hole transport layer, and a transparent electrode layer stacked sequentially, i.e., tunneling composite layer-hole transport layer-perovskite layer-electron transport layer-transparent electrode layer, or tunneling composite layer-electron transport layer-perovskite layer-hole transport layer-transparent electrode layer. In this invention, the material of the tunneling composite layer preferably includes one or more of IZO, ITO, and AZO, and the thickness is preferably 2~100 nm, more preferably 2~30 nm.

[0038] In this invention, the hole transport layer is preferably made of one or more of SAM, nickel oxide, spiro-OMeTAD, and PTAA. The SAM is preferably (2-(9H-carbazole-9-yl)ethyl)phosphonic acid (2PACz) and / or 4-(3,6-dimethoxy-9H-carbazole-9-yl)butylphosphonic acid (MeO-4PACz). In this invention, the thickness of the hole transport layer is preferably a monolayer thickness.

[0039] In this invention, the perovskite layer is the above-mentioned B-site Cd-doped two-dimensional perovskite film, and the thickness of the perovskite layer is preferably 400~2000nm, more preferably 600~1000nm; In this invention, the preferred material for the electron transport layer is PCBM or C. 60 The electron transport layer is preferably 10-20 nm thick, more preferably 15 nm thick, and contains one or more of TiO2 and SnO2.

[0040] In this invention, the material of the transparent electrode layer preferably includes one or more of IZO, ITO and AZO, and the thickness is preferably 60~100nm, more preferably 80nm.

[0041] In this invention, the outermost layer of the crystalline silicon bottom cell and the calcium and titanium ore top cell is further provided with a metal gate, which is preferably a silver electrode, and the thickness of the metal gate is preferably 200~1000nm.

[0042] In this invention, the method for fabricating the perovskite / crystalline silicon tandem solar cell includes the following steps: A tunneling composite layer, a hole or electron transport layer, a spin-coated perovskite layer, an electron or hole transport layer, and a transparent electrode layer are sequentially deposited on the surface of the crystalline silicon bottom cell to obtain a perovskite top cell. A metal gate is deposited on the outermost layer of the crystalline silicon bottom cell and the perovskite top cell to obtain a perovskite / crystalline silicon tandem solar cell.

[0043] As a specific embodiment of the present invention, the method for preparing the crystalline silicon bottom solar cell preferably includes the following steps: The silicon wafers are cleaned and texturized to obtain pretreated silicon wafers; Passivation layers are deposited on both sides of the pretreated silicon wafer to obtain an n-plane passivation layer and a p-plane passivation layer, respectively. A transparent conductive oxide layer is deposited on the p-side passivation layer to obtain a crystalline silicon bottom cell.

[0044] This invention involves cleaning and texturing silicon wafers to obtain pretreated silicon wafers. In this invention, the cleaning is preferably ultrasonic cleaning, and the cleaning reagents are preferably acetone, ethanol, and deionized water in that order, with each reagent preferably being used for 15 minutes. In this invention, the texturing process is preferably performed by immersing the cleaned silicon wafer in an alkaline solution to conduct a texturing reaction. In this invention, the alkaline solution is preferably an alkaline solution containing 2 wt% NaOH and 0.5 wt% Na₂SiO₃, and the solvent of the alkaline solution is preferably deionized water. In this invention, the temperature of the texturing reaction is preferably 70-90°C, more preferably 80°C, and the time is preferably 15-25 minutes, more preferably 20 minutes. Through this texturing process, this invention can form a pyramidal textured surface structure on the silicon wafer, enhancing light absorption.

[0045] After obtaining the pretreated silicon wafer, the present invention deposits passivation layers on both sides of the pretreated silicon wafer to obtain an n-side passivation layer and a p-side passivation layer, respectively. In the present invention, the preferred method for depositing the passivation layer is plasma-enhanced chemical vapor deposition (PECVD), the preferred reaction gases are SiH4 and H2, and the preferred deposition temperature is 180~250℃, more preferably 200℃.

[0046] This invention involves depositing a transparent conductive oxide layer on the p-side passivation layer to obtain a crystalline silicon bottom solar cell. In this invention, the deposition of the transparent conductive oxide is preferably performed by magnetron sputtering, with the magnetron sputtering power preferably being 80-150W, more preferably 100-120W, and the argon gas flow rate preferably being 15-25 sccm, more preferably 20 sccm.

[0047] In this invention, a tunneling composite layer, a hole or electron transport layer, a spin-coated perovskite layer, an electron or hole transport layer, and a transparent electrode layer are sequentially deposited on the surface of a crystalline silicon bottom solar cell to obtain a perovskite top solar cell. In this invention, the preferred method for depositing the tunneling composite layer is magnetron sputtering, with the magnetron sputtering power preferably being 80-150W, more preferably 100-120W, and the argon gas flow rate preferably being 15-25 sccm, more preferably 20 sccm.

[0048] In this invention, when depositing the hole transport layer, the hole transport layer material is preferably provided in solution form, and the solvent of the hole transport layer solution is preferably isopropanol, with a concentration preferably of 0.5~1.5 mg / mL, more preferably 1 mg / mL. In this invention, the spin-coating rate is preferably 2000~5000 rpm, more preferably 3000~4000 rpm, and the time is preferably 25~35 s, more preferably 30 s.

[0049] In this invention, the specific operation of the spin-coating perovskite layer is the same as the method for preparing B-site Cd-doped two-dimensional perovskite thin films described above, and will not be repeated here.

[0050] In this invention, the electron transport layer is preferably deposited by vapor deposition, and the vapor deposition rate is preferably 0.5 angstroms / second.

[0051] In this invention, the preferred method for depositing the transparent electrode layer is magnetron sputtering, wherein the magnetron sputtering power is preferably 70-100W, more preferably 80-90W, the preferred sputtering rate is 15-25sccm, more preferably 20sccm, and the preferred atmosphere for magnetron sputtering is argon.

[0052] This invention involves depositing a metal gate on the outermost layer of a crystalline silicon bottom cell and a perovskite top cell to obtain a perovskite / crystalline silicon tandem solar cell. In this invention, the metal gate is preferably deposited by vacuum evaporation at a rate of 1 angstrom / second, with a thickness preferably between 200 and 1000 nm, more preferably between 500 and 800 nm.

[0053] The following detailed description, in conjunction with embodiments, illustrates the B-site Cd-doped two-dimensional perovskite thin film and the perovskite / crystalline silicon tandem solar cell provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1 Perovskite BA2(FA)(Pb 1 / 2 Cd 1 / 2 Preparation of 2I7: The ratio of the organic amine salt at the A-site to the metal halide at the R-site was 1:2, and the Cd at the B-site... 2+ / Pb 2+ Weigh out 1 mmol of methyl iodide, 2 mmol of butyl iodide, 1 mmol of lead iodide, and 1 mmol of cadmium iodide, respectively, using a 1:1 ratio. Then add them to 1 mL of a DMSO: MF: DMSO (volume ratio 4:1) mixed solution and stir until homogeneous to obtain perovskite, denoted as BA2(FA)(Pb). 1 / 2 Cd 1 / 2 )2I7.

[0055] According to such Figure 1 The perovskite / crystalline silicon tandem solar cell structure shown is fabricated using the following steps: 1. Fabrication of crystalline silicon bottom solar cells (1) Silicon wafer pretreatment: Select an N-type single crystal silicon wafer with a thickness of 200 μm, and place it in acetone, ethanol and deionized water for ultrasonic cleaning for 15 min each to remove surface oil and impurities; then perform texturing treatment by immersing the silicon wafer in a mixed solution of 2% NaOH and 0.5% Na2SiO3 and reacting at 80℃ for 20 min to form a pyramid textured surface structure to enhance light absorption.

[0056] (2) Passivation layer deposition: Plasma-enhanced chemical vapor deposition (PECVD) technology is used to deposit a 5nm intrinsic amorphous silicon (a-Si:H) passivation layer and a 5nm n-type μc-Si:H (denoted as n-side) on one side of the silicon wafer, and a 10nm a-Si:H and a 5nm p-type μc-Si:H double-layer passivation structure (denoted as p-side) is deposited on the other side. The reaction gases are SiH4 and H2, and the deposition temperature is 200℃.

[0057] (3) TCO layer preparation: 80nm ITO transparent electrode was sputtered on the p-side using a magnetron sputtering device with a sputtering power of 150W and an argon flow rate of 20sccm.

[0058] 2. Fabrication of perovskite top solar cells (1) Tunneling composite layer preparation: A 15nm ITO transparent electrode was sputtered on the n-side surface of the crystalline silicon bottom cell using a magnetron sputtering device with a sputtering power of 150W and an argon flow rate of 20sccm.

[0059] (2) Hole transport layer preparation: Weigh 1 mg of 4-(3,6-dimethoxy-9H-carbazole-9-yl) butylphosphonic acid (MeO-4PACz) and dissolve it in 1 mL of isopropanol (IPA), and spin-coat it onto the surface of the tunneling composite layer.

[0060] (3) Preparation of perovskite layer: BA2(FA)(Pb 1 / 2 Cd 1 / 2 )2I7 perovskite was spin-coated onto a solvent-treated substrate in one step, and annealed at 100℃ for 20 min to a thickness of 1000 nm.

[0061] (4) Electron transport layer preparation: C is deposited sequentially 60 SnO2 serves as the electron transport layer, C 60 The thickness is 20nm, and the SnO2 thickness is 20nm.

[0062] (5) Electrode preparation: 80nm IZO transparent electrode was sputtered on the electron transport layer using a magnetron sputtering device, and 200nm silver was deposited on the transparent electrode and silicon bottom cell as a metal gate using a vacuum evaporation device.

[0063] The resulting perovskite / crystalline silicon tandem solar cell is denoted as BA2(FA)(Pb 1 / 2 Cd 1 / 2 )2I7 battery.

[0064] Example 2 Perovskite BA2(FA)(Pb 3 / 4 Cd 1 / 4 Preparation of 2I7: The ratio of the A-site organic amine salt or Cs to the R-site metal halide is 1:2, and the B-site Cd... 2+ / Pb2+ Weigh out 1 mmol of methyl iodide, 2 mmol of butyl iodide, 1.5 mmol of lead iodide, and 0.5 mmol of cadmium iodide, respectively, using a ratio of 1:3. Then add them to 1 mL of a DMSO: MF: DMSO (volume ratio 4:1) mixed solution and stir until homogeneous to obtain perovskite, denoted as BA2(FA)(Pb). 3 / 4 Cd 1 / 4 )2I7.

[0065] According to such Figure 1 The perovskite / crystalline silicon tandem solar cell structure shown is fabricated using the following steps: 1. Fabrication of crystalline silicon bottom solar cells (1) Silicon wafer pretreatment: Select N-type single crystal silicon wafers and ultrasonically clean them in acetone, ethanol and deionized water for 15 min each to remove surface oil and impurities; then perform texturing treatment by immersing the silicon wafers in a mixed solution of 2% NaOH and 0.5% Na2SiO3 and reacting at 80℃ for 20 min to form a pyramid textured surface structure to enhance light absorption.

[0066] (2) Passivation layer deposition: Plasma-enhanced chemical vapor deposition (PECVD) technology is used to deposit a 5nm intrinsic amorphous silicon (a-Si:H) passivation layer and a 5nm n-type μc-Si:H (denoted as n-side) on one side of the silicon wafer, and a 10nm a-Si:H and a 5nm p-type μc-Si:H double-layer passivation structure (denoted as p-side) is deposited on the other side. The reaction gases are SiH4 and H2, and the deposition temperature is 200℃.

[0067] (3) TCO layer preparation: 80nm ITO transparent electrode was sputtered on the p-side using a magnetron sputtering device with a sputtering power of 150W and an argon flow rate of 20sccm.

[0068] 2. Fabrication of perovskite top solar cells (1) Tunneling composite layer preparation: A 15nm ITO transparent electrode was sputtered on the n-side surface of the crystalline silicon bottom cell using a magnetron sputtering device with a sputtering power of 150W and an argon flow rate of 20sccm.

[0069] (2) Hole transport layer preparation: Weigh 1 mg of 4-(3,6-dimethoxy-9H-carbazole-9-yl) butylphosphonic acid (MeO-4PACz) and dissolve it in 1 mL of isopropanol (IPA), and spin-coat it onto the surface of the tunneling composite layer.

[0070] (3) Preparation of perovskite layer: BA2(FA)(Pb 3 / 4 Cd 1 / 4 )2I7 perovskite was spin-coated onto the surface of the hole transport layer in one step and annealed at 100℃ for 20 min.

[0071] (4) Electron transport layer preparation: C is sequentially deposited on the surface of the perovskite layer. 60 SnO2 serves as the electron transport layer, C 60 The thickness is 20nm, and the SnO2 thickness is 20nm.

[0072] (5) Electrode preparation: 80nm IZO transparent electrode was sputtered on the electron transport layer using a magnetron sputtering device, and 200nm silver was deposited on the transparent electrode and the crystalline silicon bottom cell as a metal gate using a vacuum evaporation device.

[0073] The resulting perovskite / crystalline silicon tandem solar cell is denoted as BA2(FA)(Pb 3 / 4 Cd 1 / 4 )2I7 crystalline silicon tandem solar cell.

[0074] Example 3 Compared to Example 1, the raw materials for preparing the perovskite layer were 0.5 mmol of methylammonium iodide, 0.5 mmol of methylammonium iodide, 2 mmol of butylammonium iodide, 1 mmol of lead iodide, and 1 mmol of cadmium iodide. The resulting perovskite / crystalline silicon tandem solar cell was designated BA2(FA). 0.5 MA 0.5 (Pb) 1 / 2 Cd 1 / 2 )2I7 crystalline silicon tandem solar cell.

[0075] Comparative Example 1 Compared to Example 1, the raw materials for preparing the perovskite layer were 1 mmol of formamide iodine, 2 mmol of butylammonium iodine, and 2 mmol of lead iodide, yielding perovskite BA2FAPb2I7. The resulting perovskite / crystalline silicon tandem solar cell is designated as BA2FAPb2I7 crystalline silicon tandem solar cell.

[0076] Performance testing (1) The perovskites obtained in Examples 1-2 and Comparative Example 1 were used to fabricate perovskite devices with the following structure: ITO / MeO-4PACZ / perovskite layer / C 60 / SnO2 / Ag, the thickness of the perovskite layer is 1µm.

[0077] Short-circuit current density of perovskite devices (J) SC ), open circuit voltage (V) OC The fill factor (FF) and maximum power conversion efficiency (PCE) were tested using the following methods: J - V Tests were conducted under simulated conditions of 25°C, 0~10RH, and 1 Sun. The results are shown in Table 1.

[0078] Table 1. Perovskite device parameters with a perovskite thickness of 1 µm.

[0079] As can be seen from Table 1, BA2(FA)(Pb 1 / 2 Cd 1 / 2 The 2I7 battery (50% cadmium-substituted sample) exhibited a PCE of 19.59% (significantly higher than the 15.46% of the pure lead-based battery) at a experimentally fabricable thickness of 1 μm, and its short-circuit current density increased from 12.50 mA / cm². 2 This can alleviate the current mismatch problem in multilayer devices.

[0080] (2) Short-circuit current density (J) of the perovskite / crystalline silicon tandem solar cells obtained in Examples 1-3 and the comparative examples. SC ), open circuit voltage (V) OC The fill factor (FF) and maximum power conversion efficiency (PCE) were tested using the following methods: J - V Tests were conducted under simulated conditions of 25°C, 0~10RH, and 1 Sun. The results are shown in Table 2.

[0081] Table 2. Parameters of perovskite-silicon multilayer devices with a perovskite thickness of 1 µm.

[0082] As can be seen from Table 2, BA2(FA)(Pb 1 / 2 Cd 1 / 2 The 2I7 battery (50% cadmium-substituted sample) exhibited a PCE of 28.74% (significantly higher than the 18.51% of the pure lead-based battery) at a experimentally fabricable thickness of 1 μm, and its short-circuit current density increased from 12.30 mA / cm². 2 This improves compatibility with silicon substrates and solves the stability issues of existing multilayer devices.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A B-site Cd-doped two-dimensional perovskite thin film, characterized in that, The chemical composition of the B-site Cd-doped two-dimensional perovskite is R2A. n-1 B n X 3n+1 , where n = 1, 2 or 3; The R site is an organic ammonium cation; The A site is one or more of the following: methylamine cation, formamidinium cation, and cesium cation; B position Cd 2+ With Pb 2+ The mixture, wherein the molar content of Cd at site B is >0 and <100%; X is I - , or I - With Br - A mixture.

2. The B-site Cd-doped two-dimensional perovskite thin film according to claim 1, characterized in that, The organic ammonium cation at the R position is one or more of the following: butammonium cation, 2-methoxyethylammonium cation, 2-methylthioethylammonium cation, benzylammonium cation, phenylethylammonium cation, and 2-thiophenemethylammonium cation.

3. The B-site Cd-doped two-dimensional perovskite thin film according to claim 1 or 2, characterized in that, Cd in position B 2+ With Pb 2+ The molar ratio is 1:1~3.

4. The method for preparing a B-site Cd-doped two-dimensional perovskite thin film according to any one of claims 1 to 3, characterized in that, Includes the following steps: Raw materials with chemical compositions of RX, AX, and BX are mixed with organic solvents to obtain perovskite slurry; The perovskite slurry was coated onto the substrate surface and annealed to obtain a B-site Cd-doped two-dimensional perovskite film.

5. The preparation method according to claim 4, characterized in that, The annealing temperature is 100~150℃ and the time is 20~40min.

6. The application of the B-site Cd-doped two-dimensional perovskite thin film according to any one of claims 1 to 3 or the B-site Cd-doped two-dimensional perovskite thin film prepared by the preparation method according to claim 4 or 5 in the light absorption layer of the top cell of a solar cell.

7. A perovskite / crystalline silicon tandem solar cell, characterized in that, It includes a crystalline silicon bottom cell and a perovskite top cell stacked on the surface of the crystalline silicon bottom cell; The perovskite top solar cell comprises a tunneling composite layer, a hole or electron transport layer, a perovskite layer, an electron or hole transport layer, and a transparent electrode layer stacked sequentially; the perovskite layer is a B-site Cd-doped two-dimensional perovskite thin film as described in any one of claims 1 to 3 or a B-site Cd-doped two-dimensional perovskite thin film prepared by the preparation method described in claim 4 or 5. The outermost layer of the crystalline silicon bottom cell and the perovskite top cell is provided with a metal gate.

8. The perovskite / crystalline silicon tandem solar cell according to claim 7, wherein the crystalline silicon base cell is one of HJT cell, TOPCon cell, IBC / BC cell, and BSF cell.

9. The perovskite / crystalline silicon tandem solar cell according to claim 7, characterized in that, In the perovskite top solar cell, the tunneling composite layer is made of one or more of IZO, ITO and AZO, and has a thickness of 2~100nm. The hole transport layer is made of one or more of SAM, nickel oxide, spiro-OMeTAD, and PTAA. The thickness of the perovskite layer is 400~2000 nm; The electron transport layer is made of PCBM, C 60 One or more of TiO2 and SnO2, wherein the thickness of the electron transport layer is 10~20nm; The transparent electrode layer is made of one or more of IZO, ITO and AZO, and has a thickness of 60~100nm.

10. The method for preparing the perovskite / crystalline silicon tandem solar cell according to any one of claims 7 to 9, characterized in that, Includes the following steps: A tunneling composite layer, a hole or electron transport layer, a spin-coated perovskite layer, an electron or hole transport layer, and a transparent electrode layer are sequentially deposited on the surface of the crystalline silicon bottom cell to obtain a perovskite top cell. A metal gate is deposited on the outermost layer of the crystalline silicon bottom cell and the perovskite top cell to obtain a perovskite / crystalline silicon tandem solar cell.

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