Ultra-wide-band-gap perovskite thin film and application thereof

Abstract

The invention discloses an ultra wide band gap perovskite thin film and application thereof, and belongs to the technical field of solar cells. The ultra-wide-band-gap perovskite thin film is prepared by the following steps: coating a perovskite precursor solution, carrying out post-treatment on a perovskite wet film by using an inducer, and then annealing to obtain a perovskite thin film, the inducer is selected from oleylamine chloride, methylamine chloride, formamidine chloride, guanidine chloride, octyl ammonium chloride, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, dimethyl dioctadecyl ammonium chloride and tetradecyl trimethyl ammonium chloride. According to the invention, the chlorine source is introduced as an inducer, and post-treatment is carried out in the wet state of the thin film, so that homogenization of the surface of the thin film is realized, and the process can effectively solve the wrinkle problem of high fluctuation of the surface of the ultra-wide band gap perovskite, and provides a new solution for preparation of an efficient and stable full-perovskite triple-junction solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to an ultrawide wide-bandgap perovskite thin film and its application in all-perovskite triple-junction tandem solar cells. Background Technology

[0002] High-efficiency perovskite-based tandem solar cells are mainly divided into two categories: the first combines perovskite cells with other cells (such as crystalline Si, CIGS, and OPV); the second directly combines perovskite cells with other perovskite cells (all-perovskite). While combining perovskite with other cells can also fabricate high-efficiency tandem devices, the fabrication cost of combining different photovoltaic technologies is high, the process is complex, and compatibility is poor. In contrast, all-perovskite tandem devices combine high efficiency, low cost, and minimal environmental impact, and are considered one of the most promising high-efficiency, low-cost photovoltaic technologies, poised to play a leading role in future photovoltaic power generation. Currently, the certified efficiency of all-perovskite two-junction tandem solar cells has reached 30.1%, far exceeding the certified efficiency of single-junction perovskite solar cells. A simple way to push the efficiency even higher is to add a third sub-cell to the all-perovskite two-junction series device to construct a triple-junction tandem cell, further reducing carrier heat loss. Currently, all-perovskite triple-junction tandem solar cells are an emerging research direction in the field of perovskite solar cells, with relatively few reported research results both domestically and internationally. In practical triple-junction devices, the efficiency improvement gradually decreases. This is mainly due to the increased number of intermediate composite layers and interface layers in the triple-junction structure, as well as the high requirements for current matching between sub-cells, which easily introduces the cumulative effects of optical losses and parasitic absorption, thus limiting the overall performance improvement.

[0003] Currently, perovskites with different bandgap widths can be rationally designed through component engineering. Narrow-bandgap subcells, acting as the bottom cell, are primarily responsible for the efficient utilization of near-infrared light. Intermediate-bandgap subcells, acting as the middle cell, correspond to the visible light band, while the top-layer ultra-wide-bandgap top cell requires an even larger bandgap to effectively absorb high-energy short-wavelength photons. Based on this, the subcells work together in a coordinated manner, constructing a high-efficiency all-perovskite triple-junction tandem solar cell while maintaining structural complexity. In this structure, the performance of the ultra-wide-bandgap perovskite subcell, acting as the top cell, directly affects the spectral matching effect and overall output performance of the triple-junction tandem device. Therefore, how to fabricate stable and high-efficiency ultra-wide-bandgap perovskite subcells has become one of the urgent technical problems to be solved in the field of all-perovskite triple-junction tandem solar cells.

[0004] However, current research on ultrawide-bandgap perovskite sub-solar cells still has shortcomings, mainly in the following three aspects: First, photoinduced halogen phase separation. Photoinduced halogen phase separation is common in wide-bandgap iodine (I) and bromine (Br) mixed perovskite absorber layers with band gaps greater than 1.65 eV. Especially for ultrawide-bandgap perovskite absorber layers with a band gap of approximately 2.0 eV, halogen phase separation is highly likely due to their typically higher than 60% Br content, resulting in I-rich regions with lower band gaps, which become recombination centers, enhancing nonradiative recombination of charge carriers. Second, a large open-circuit voltage (… V oc Loss. Actual ultrawide bandgap cell V oc There is usually a significant difference between the actual ultra-wide bandwidth and its theoretical value. V oc Significant losses are often observed, primarily because the high-Br-content perovskite absorber layer is prone to lattice strain and halogen vacancies, leading to defects and reduced carrier lifetime. Furthermore, photoinduced phase separation can also cause large losses exceeding 700 mV. V oc Losses directly lead to a decline in the final device performance. Finally, there is the issue of current mismatch and interconnection losses in all-perovskite triple-junction tandem solar cells, constructed by combining ultra-wide bandgap sub-cells with intermediate and narrow bandgap sub-cells. Because all-perovskite triple-junction tandem solar cells employ a series connection structure for each sub-cell, the final output short-circuit current (… J sc The current of the sub-cell with the smallest current in the triple junction is limited. Therefore, how to adjust the ultra-wide bandgap sub-cell to achieve current matching with the intermediate and narrow bandgap sub-cells is also a key issue. In addition, it is also important to select an interconnect layer that can minimize reflection loss and parasitic absorption and protect the underlying layer from solvent erosion used in subsequent deposition layers. Summary of the Invention

[0005] To address the issue of surface morphology inhomogeneity when depositing all-perovskite triple-junction solar cells on ultra-wide bandgap perovskite films, this invention provides an ultra-wide bandgap perovskite preparation strategy based on competitive nucleation technology and its application in all-perovskite triple-junction tandem solar cells. The key point is the innovative proposal to introduce an inducing agent (such as oleoamine chloride) for post-treatment of the perovskite wet film.

[0006] One objective of this invention is to provide a perovskite thin film, which is prepared by the following method: The perovskite precursor solution is coated, the perovskite wet film is post-treated with an inducing agent, and then annealed to obtain a perovskite thin film. The inducing agent is selected from oleylamine chloride (OAmCl), methylamine chloride (MACl), formamidinium chloride (FACl), guanidine chloride (GACl), octylammonium chloride (OACl), dodecyltrimethylammonium chloride (DTAC), hexadecyltrimethylammonium chloride (CTAC), octadecyltrimethylammonium chloride (ETAC), dimethyl dioctadecylammonium chloride (DMAC), and tetradecyltrimethylammonium chloride (TTAC).

[0007] Furthermore, the perovskite precursor liquid comprises a precursor of a perovskite structural material and a solvent, wherein the band gap of the perovskite structural material is 1.9-2.2 eV.

[0008] Further, the chemical formula of the perovskite structure is ABX3; A is a monovalent cation selected from one or more of cesium ions, rubidium ions, methylamine ions, and formamidinium ions; B is a divalent cation selected from one or more of lead ions, copper ions, zinc ions, gallium ions, tin ions, calcium ions, and lanthanides; X is a monovalent anion selected from one or more of iodide ions, bromide ions, chloride ions, fluoride ions, and thiocyanate ions.

[0009] Furthermore, the solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, 2-methoxyethanol and N-methylpyrrolidone.

[0010] Furthermore, the coating is performed by spin coating, slot coating, or scraping.

[0011] Furthermore, the annealing temperature is 85-135℃, and the time is 10-30 minutes.

[0012] A second objective of this invention is to provide a solar cell comprising the aforementioned perovskite thin film.

[0013] Furthermore, the solar cell is an all-perovskite triple-junction tandem solar cell.

[0014] Compared with existing technologies, this invention innovatively introduces a chlorine source (such as OAmCl) as an inducer for the post-treatment of ultrawide bandgap perovskite wet films. Its advantages are: (1) It effectively solves the problem of highly undulating wrinkles on the surface of ultrawide bandgap perovskite, providing a smoother substrate for subsequent functional layer deposition; (2) The introduction of a chlorine source (such as OAmCl) balances the I and Br crystallization processes, and chloride ions (Cl... - (3) The inducing agent is introduced through post-processing. This technology is simple and efficient. It only requires one step of operation on the wet film. It does not require additional complicated equipment or steps to achieve homogenization of the film surface, which is very cost-effective. Attached Figure Description

[0015] Figure 1 A schematic diagram of the structure of an ultrawide-bandgap perovskite single-junction solar cell.

[0016] Figure 2 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements were performed on ultrawide wide-bandgap perovskite thin films before and after treatment.

[0017] Figure 3 This is a top view of the ultrawide wide-bandgap perovskite film before and after treatment using a scanning electron microscope (SEM).

[0018] Figure 4 The images show the X-ray diffraction (XRD) spectra of ultrawide wide-bandgap perovskite films before and after treatment.

[0019] Figure 5 The current density-voltage (JV) curves of ultrawide wide-bandgap perovskite single-junction cells before and after treatment are shown.

[0020] Figure 6 This is a SEM cross-sectional view of a fully perovskite triple-junction tandem solar cell and a corresponding structural schematic diagram.

[0021] Figure 7 The JV curves are shown for the all-perovskite triple junction tandem solar cells before and after treatment.

[0022] Figure 8 Maximum power point (MPP) tracking tests were conducted on all-perovskite triple-junction tandem solar cells before and after treatment, up to T 90 . Detailed Implementation

[0023] Ultra-wide bandgap solar cells, as the top cell in triple-junction solar cells, typically have a high Br / I ratio. However, Br and I... - The crystallization rates of perovskite films are not uniform. During crystallization, a Br-rich phase forms rapidly first, followed by an I-rich phase, leading to localized stress concentration. Ultimately, this results in large, undulating wrinkles on the film surface, with the Br-rich phase distributed at the wrinkle tips and the I-rich phase at the wrinkle bottoms. The highly undulating surface morphology of perovskite films hinders the continuous and uniform deposition of subsequent functional layers, thus impeding efficient carrier transport and causing significant interfacial losses. Ultimately, this manifests as significant device defects. V oc The loss of fill factor (FF) leads to a decrease in device efficiency. In addition, the uneven distribution of Br and I on the surface wrinkles can also cause the local surface of the thin film to deviate from the ideal stoichiometry, generating more defects and ultimately leading to a decrease in device performance.

[0024] To address these issues, researchers have proposed various solutions, such as compositional tuning, bulk phase treatment, and interfacial passivation, aimed at improving the uniformity and stability of perovskite films. Despite significant progress in these areas, the fundamental understanding and precise control of high Br / I wide-bandgap perovskite materials remain in the exploratory stage, and many technologies have not yet reached the level of mature commercial application.

[0025] This invention relates to a strategy for preparing ultrawide-bandgap perovskite based on competitive nucleation technology and its application in all-perovskite triple-junction tandem solar cells. The key focus is the innovative introduction of an inducing agent for post-treatment of the perovskite wet film. This technology primarily aims to address the surface morphology inhomogeneity problem encountered when depositing all-perovskite triple-junction solar cells on ultrawide-bandgap perovskite films.

[0026] The inducing agent in this invention can be, but is not limited to, OAmCl. It can be other chlorine-containing materials, such as methylamine chloride (MACl), formamidinium chloride (FACl), guanidine chloride (GACl), octylammonium chloride (OACl), dodecyltrimethylammonium chloride (DTAC), hexadecyltrimethylammonium chloride (CTAC), octadecyltrimethylammonium chloride (ETAC), dimethyl dioctadecylammonium chloride (DMAC), tetradecyltrimethylammonium chloride (TTAC), etc.

[0027] Specifically, by employing a competitive nucleation mechanism and using OAmCl as an inducing agent, post-processing was performed in a wet state to achieve homogenization of the film surface. This process effectively solves the problem of highly undulating wrinkles on the ultra-wide bandgap perovskite surface, providing a smoother substrate for subsequent functional layer deposition. During the preparation of ultra-wide bandgap perovskite films, the different crystallization rates of Br and I often lead to highly wrinkled surfaces. This surface inhomogeneity severely affects the deposition of subsequent functional layers, particularly negatively impacting lateral continuity and longitudinal adhesion, thus affecting the overall performance of the battery, especially carrier transport efficiency.

[0028] To achieve homogenization of the thin film surface, a competitive nucleation technique was innovatively introduced. A chloride source (such as OAmCl) was introduced into the system, where chloride ions preferentially enter the crystal lattice, suppressing the rapid crystallization of bromine and resulting in a more consistent crystallization rate for Br and I. In this way, the surface morphology of the perovskite thin film was significantly improved, and fluctuations were effectively suppressed, thus providing a more uniform surface for the subsequent deposition of multifunctional layers. The innovation of this technology lies in its simple and efficient post-processing method, requiring only a one-step operation on the wet film, without the need for additional complex equipment or steps to achieve film surface homogenization. Compared to traditional complex processes, this simple processing method has a significant cost advantage and is also better compatible with large-scale production.

[0029] This innovative post-processing technology not only provides a new solution for the fabrication of highly efficient and stable all-perovskite triple-junction solar cells, but also demonstrates the potential of perovskite materials in high-performance photovoltaic technology. The ultra-wide bandgap perovskite solar cells fabricated using this technology achieve efficiencies exceeding 15%, such as... Figure 5 As shown, the efficiency is 1% higher than that of the untreated ultra-wide bandgap perovskite solar cell (device reverse scan efficiency of 14.2%). Furthermore, when the ultra-wide bandgap perovskite sub-cells prepared using this inducer-introduction post-treatment technique were applied to an all-perovskite triple-junction tandem solar cell, a photoelectric conversion efficiency exceeding 30% was achieved. Figure 7 As shown, this represents the highest efficiency reported to date for an all-perovskite triple-junction perovskite solar cell.

[0030] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Example 1

[0033] This embodiment provides a method for fabricating an ultrawide-bandgap perovskite single-junction solar cell, employing... Figure 1 The device structure shown consists of ITO / NiO from the light-receiving front to the light-receiving back side. x / SAM / UWBG perovskites / C 60 / ALD-SnO2 / Cu is used for interface tuning of ultrawide bandgap cells with severe performance loss.

[0034] Device fabrication includes the following steps: ① Cleaning of ITO substrate: The ITO substrate was ultrasonically cleaned for 15 minutes in sequence with detergent, deionized water and ethanol. The cleaned substrate was then subjected to ultraviolet ozone for 15 minutes to increase surface wettability.

[0035] ②Preparation of hole transport layer (HTL): NiOx nanoparticles with a concentration of 15 mg / mL were spin-coated onto clean ITO using deionized water as the solvent. The nanoparticles were then spin-coated onto the prepared ITO substrate at 4000 rpm for 10 seconds, followed by annealing at 130°C for 30 minutes.

[0036] ③ Preparation of the interface modification layer (SAM): 100 μL of 1 mmol Me-4PACz solution was spin-coated onto ITO / NiO. x On the substrate, and then post-annealed at 100°C for 5 minutes.

[0037] ④ Preparation of Ultra-Wide Bandgap (UWBG) Perovskite Precursor Solution: A precursor solution (0.9 mol / L) of UWBG perovskite (bandgap approximately 2.0 eV) was prepared using a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1. The molar ratio of formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) was 0.7:0.3:1. The precursor solution was stirred at room temperature for 8 hours, then filtered through a 0.22 μm polytetrafluoroethylene membrane, and subsequently used to prepare perovskite thin films.

[0038] ⑤ Deposition of ultrawide bandgap perovskite films: Perovskite films were prepared using a two-step spin-coating process: (1) spin-coating at 1000 rpm for 10 seconds with an acceleration of 1000 rpm·s; (2) spin-coating at 4000 rpm for 40 seconds with an acceleration of 2000 rpm·s. 20 seconds before the end of the second spin-coating step, 150 μL of anisole was dropped onto the rotating substrate.

[0039] When preparing ultra-uniform wide-bandgap perovskite films using competitive nucleation technology, after the second spin-coating process, a polishing agent mixed with an inducer is spin-coated onto the wetted ultra-uniform wide-bandgap perovskite surface at 4000 rpm for 40 seconds. Then, it is annealed at 85°C for 5 minutes and at 135°C for 15 minutes. In this embodiment, the polishing agent is a hexafluoroisopropanol (HFP) / N,N-dimethylformamide (DMF) mixed solvent, and the inducer is oleylamine chloride (OAmCl).

[0040] ⑥ Fabrication of the electron transport layer (ETL): C is deposited using thermal evaporation technology.60 The material is then used to grow a layer of SnO2 using ALD.

[0041] ⑦ Electrode preparation: Cu was deposited by vacuum thermal evaporation as the top electrode.

[0042] In this embodiment, a suitable polishing agent (HFP / DMF mixed solvent) was selected for surface polishing, and then OAmCl was used as an inducer to achieve homogenization and crystallization of perovskite. Figure 2 This study demonstrates the distribution of halogen elements (such as Br and I) on the surface of an ultrawide wide-bandgap perovskite thin film before and after using competitive nucleation technology, as determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results show that the distribution of Br and I on the treated perovskite film surface is more uniform, indicating that the composition of the perovskite film surface has been homogenized through competitive nucleation. This process eliminates the inhomogeneity caused by the difference in Br and I crystallization rates on the film surface, thus providing a more uniform substrate for the subsequent deposition of multifunctional layers and contributing to improved performance and stability of all-perovskite triple-junction solar cells.

[0043] Figure 3 Scanning electron microscope (SEM) images of ultrawide bandgap perovskite films before and after treatment are shown. A significant smoothing effect is clearly visible on the treated perovskite film surface. Compared to the untreated film, the treated perovskite film surface is more uniform, with significantly reduced surface undulations, highlighting the homogeneity of the surface morphology. This indicates that the OAmCl-induced competitive nucleation technique effectively optimizes the film surface structure, eliminating inhomogeneities caused by the difference in Br and I crystallization rates, and successfully achieving homogenization of the surface morphology. Specifically, the SEM images clearly show the details of the treated film surface; micron-level wrinkles and undulations are significantly suppressed, and the film surface becomes smoother. This smooth surface structure provides an ideal substrate for subsequent functional layer deposition, reduces interface defects and discontinuities, and lays the foundation for the high efficiency of all-perovskite triple-junction solar cells. Furthermore, the homogenization of the surface morphology not only improves the photoelectric performance of the film but also effectively enhances the mechanical and chemical stability of the device, contributing to improved long-term stability and operating efficiency of the cell.

[0044] Figure 4X-ray diffraction (XRD) spectra of the ultrawide wide-bandgap perovskite thin film before and after treatment are shown. The treated perovskite film exhibits stronger and sharper diffraction peaks, particularly with a significant increase in peak intensity along the (100) crystal plane, indicating a superior (100) crystal orientation and higher crystallinity. This improved crystal orientation suggests a more regular atomic arrangement within the film, which facilitates efficient carrier transport and reduces recombination losses. Competitive nucleation processes suppress the formation of irregular grains during film growth, reducing surface defect density and significantly improving the film's crystal integrity and uniformity. This optimization not only improves the crystal quality of the perovskite film but also provides a reliable guarantee for enhancing the efficiency and operational stability of optoelectronic devices.

[0045] Figure 5 The current density-voltage (JV) curves of ultrawide bandgap perovskite single-junction cells before and after treatment are shown. Compared with the untreated cells, the ultrawide bandgap perovskite single-junction cells treated with OAmCl inducer can improve the photoelectric conversion efficiency from 14.2% to 15.2%. Example 2

[0046] This embodiment 2 provides a method for fabricating an all-perovskite triple-junction tandem solar cell, using... Figure 6 The device structure shown, from the light-receiving front side to the light-receiving back side, consists of: ITO / NiO. x / SAM / UWBG perovskites / C 60 / ALD-SnO2 / ITO / NiO / SAM / MBG perovskites / C 60 / ALD-SnO2 / Au / PEDOT:PSS / NBG perovskites / C 60 / ALD-SnO2 / Cu.

[0047] Device fabrication includes the following steps: (1) Fabrication of ultrawide bandgap subcells The fabrication of the ultrawide bandgap cell follows steps ①-⑥ in Example 1 above. Based on this, a 10-nanometer thick layer of ITO is magnetron sputtered on the ALD SnO2 tunneling composite layer as the intermediate bandgap cell conductive electrode for subsequent device fabrication.

[0048] (2) Preparation of intermediate bandgap subcells ①Preparation of hole transport layer: NiOx nanoparticles were dispersed at a concentration of 15 mg / mL in a deionized water:isopropanol mixture with a volume ratio of 3:1. The mixture was then spin-coated in air at 4000 rpm for 10 seconds onto a prepared ITO substrate, followed by annealing at 130°C for 30 minutes.

[0049] ② Preparation of the interface modification layer (SAM): 100 μL of 1 mmol Me-4PACz solution was spin-coated onto ITO / NiO. x On the substrate, and then post-annealed at 100°C for 5 minutes.

[0050] ③ Preparation of intermediate bandgap (MBG) perovskite precursor solution: A precursor solution (1.5 mol / L) of MBG perovskite (bandgap approximately 1.6 eV) was prepared using a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1. The molar ratio of formamidinium iodide (FAI), cesium iodide (CsI), lead iodide (PbI2), and lead bromide (PbBr2) was 0.8:0.2:0.85:0.15. The precursor solution was stirred at room temperature for 6 hours, then filtered through a 0.22 μm polytetrafluoroethylene membrane, and subsequently used to prepare perovskite thin films.

[0051] ④ Deposition of intermediate bandgap perovskite films: A two-step spin-coating process was used: spin-coating at 2000 rpm for 10 seconds in a nitrogen-atmospheric glove box with an acceleration of 200 rpm·s; then spin-coating at 6000 rpm for 30 seconds with an acceleration of 2000 rpm·s. Ten seconds before the end of the second spin-coating step, 200 μL of anisole was dropped onto the rotating substrate. Annealing was performed at 100°C for 10 minutes.

[0052] ⑤ Fabrication of the electron transport layer (ETL): C was deposited using thermal evaporation technology. 60 The material is then used to grow a layer of SnO using ALD. 2。

[0053] ⑥ Fabrication of interconnect layer: A 0.5 nm thick ultrathin Au film was deposited using vacuum thermal evaporation for recombination of charge carriers.

[0054] (3) Preparation of narrowband tin battery ①Preparation of hole transport layer: PEDOT-PSS solution was spin-coated onto the tunneling composite layer in air at 4000 rpm for 30 seconds using a solution method. After annealing at 120°C for 20 minutes, it was transferred to a nitrogen atmosphere glove box.

[0055] ② Preparation of narrow bandgap (NBG) perovskite precursor solution: A precursor solution (2.4 mol / L) of NBG perovskite (bandgap approximately 1.22 eV) was prepared using a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 2:1. The molar ratios of formamidine iodide (FAI) / methylamine iodide (MAI) and lead iodide (PbI2) / stannous iodide (SnI2) were 0.7:0.3 and 0.5:0.5, respectively, and the molar ratio of {formamidine iodide (FAI) + methylamine iodide (MAI)} / {lead iodide (PbI2) + stannous iodide (SnI2)} was 1:1. Furthermore, stannous fluoride (SnF2) at a 10 mol% relative to stannous iodide (SnI2) was added to the precursor solution, and the solution was stirred at room temperature for 2 hours. Following this, 5 mg / mL of tin powder and 0.3 mol% imine sulfonic acid were added to the precursor solution to reduce the Sn in the precursor solution. 4+ The precursor solution was then stirred at room temperature for two hours, filtered through a 0.22-micron polytetrafluoroethylene membrane, and then used to prepare perovskite thin films.

[0056] ③ Deposition of narrow-band tin (NBG) perovskite films: A two-step spin-coating process was used: spin-coating was performed in a nitrogen-atmospheric glove box at 1000 rpm for 10 seconds with an acceleration of 200 rpm·s; then spin-coating was performed at 4000 rpm for 40 seconds with an acceleration of 1000 rpm·s. Twenty seconds before the end of the second spin-coating step, 200 μL of ethyl acetate was dropped onto the rotating substrate. Annealing was then performed at 100°C for 10 minutes.

[0057] ④ Fabrication of the electron transport layer (ETL): C is deposited using thermal evaporation technology. 60 The material was then processed, and a layer of SnO2 was grown by ALD. ⑤ Electrode fabrication: 150 nm Cu was deposited by vacuum thermal evaporation as the top electrode.

[0058] Figure 7 This paper demonstrates an all-perovskite triple-junction tandem solar cell fabricated using the ultra-wideband tin cell of this embodiment, which successfully achieved a photoelectric conversion efficiency of over 30%. This achievement breaks through the efficiency bottleneck of traditional single-cell cells and reaches the highest efficiency of triple-junction cells to date.

[0059] Figure 8 The maximum power point (MPP) tracking test demonstrates the efficiency degradation of the perovskite solar cell before and after treatment. Figure 8 The results clearly show that the perovskite solar cell treated with competitive nucleation technology experiences an efficiency degradation to 90% of its initial efficiency (T0). 90The time required for degradation to reach T is significantly extended. Specifically, the perovskite solar cell before treatment degrades to T... 90 The initial photostability was reduced to 246 hours, while the treated perovskite solar cell extended to 569 hours, demonstrating a significant improvement in photostability. This result indicates that the treated perovskite film not only achieved a breakthrough in photoelectric conversion efficiency but also significantly enhanced stability under long-term illumination conditions. The optimized perovskite film effectively reduced carrier recombination by improving crystal quality and reducing surface defects, thereby slowing down the rate of efficiency decay and enhancing the long-term stability of the cell. This improvement is of great significance for the commercial application of all-calcium triple-junction tandem solar cells, indicating a significant improvement in their long-term stability and reliability in practical applications.

Claims

1. A perovskite thin film, characterized in that, It is prepared by the following method: The perovskite precursor solution is coated, the perovskite wet film is post-treated with an inducing agent, and then annealed to obtain the perovskite thin film. The inducing agent is selected from oleylamine chloride, methylamine chloride, formamidinium chloride, guanidine chloride, octylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dimethyl dioctadecylammonium chloride, and tetradecyltrimethylammonium chloride.

2. The perovskite thin film according to claim 1, characterized in that, The perovskite precursor solution comprises a precursor of a perovskite structural material and a solvent, wherein the perovskite structural material has a band gap of 1.9-2.2 eV.

3. The perovskite thin film according to claim 2, characterized in that, The chemical formula of the perovskite structure is ABX3; A is a monovalent cation selected from one or more of cesium ions, rubidium ions, methylamine ions, and formamidinium ions; B is a divalent cation selected from one or more of lead ions, copper ions, zinc ions, gallium ions, tin ions, calcium ions, and lanthanides; X is a monovalent anion selected from one or more of iodide ions, bromide ions, chloride ions, fluoride ions, and thiocyanate ions.

4. The perovskite thin film according to claim 2, characterized in that, The solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, 2-methoxyethanol, and N-methylpyrrolidone.

5. The perovskite thin film according to claim 1, characterized in that, The coating is applied by spin coating, slot coating, or scraping.

6. The perovskite thin film according to claim 1, characterized in that, The annealing temperature is 85-135℃, and the time is 10-30 minutes.

7. A solar cell, characterized in that, It includes the perovskite thin film according to any one of claims 1-6.

8. The solar cell according to claim 7, characterized in that, The solar cell is a fully perovskite triple junction tandem solar cell.

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