Perovskite film layer, preparation method and perovskite triple-junction stacked solar cell

Abstract

This invention relates to a perovskite film, its preparation method, and a perovskite triple-junction tandem solar cell. The preparation method includes the following steps: coating a perovskite precursor solution onto a substrate surface, then coating with a polishing agent, and annealing to obtain the perovskite film. The polishing agent comprises a mixed solvent consisting of a first solvent and a second solvent, wherein the first and second solvents have different polarities and solubilities. This invention utilizes a mixed solvent to reconstruct the surface of the perovskite film, thereby obtaining a relatively smooth perovskite film surface. It enables effective surface polishing without damaging the perovskite structure, giving the perovskite film both lateral continuity and longitudinal adhesion, thus improving the quality of the perovskite film and the perovskite triple-junction tandem solar cell.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a perovskite film, its preparation method, and a perovskite triple-junction tandem solar cell. Background Technology

[0002] Effectively integrating multiple light-absorbing layers with different bandgap into multi-junction solar cells can significantly reduce energy loss caused by carrier thermalization, thereby improving photoelectric conversion efficiency (PCE). Perovskite / silicon and all-perovskite double-junction tandem solar cells achieved PCEs as high as 34.9% and 30.1%, respectively, significantly surpassing the performance of traditional single-junction and double-junction cells. According to the Shockley-Queisser theoretical limit, triple-junction solar cells (TJSCs) have both higher theoretical and target conversion efficiencies than single-junction and double-junction cells.

[0003] Perovskite materials with excellent bandgap tunability can achieve perfect spectral matching, making them a preferred material for multi-junction solar cells. For example, an all-perovskite triple-junction solar cell consists of an ultra-wide bandgap perovskite sub-cell (UWBG), an intermediate bandgap perovskite sub-cell, and a narrow bandgap perovskite sub-cell. Due to the heterogeneous crystallization problem between bromine-containing and iodine-containing perovskite phases, bromine-containing substances readily and directly nucleate and form a surface layer during perovskite film formation, while iodine-containing substances beneath the wet film crystallize and shrink more slowly, leading to internal stress concentration and resulting in noticeable wrinkles on the perovskite film surface. This causes significant open-circuit voltage (Voc) and fill factor (FF) losses in the UWBG sub-cell. Achieving completely uniform bromine-iodine mixing, especially during the formation of the perovskite film using anti-solvent treatment methods, remains a technical challenge. Therefore, existing technologies hinder the fabrication of highly efficient and stable UWBG perovskite solar cells through high bromide-to-iodide ratios.

[0004] This wrinkled morphology is a key obstacle to developing high-efficiency perovskite-based multi-junction solar cells because such cells typically require multilayer thin films to achieve core functions such as charge transport, surface passivation, and carrier recombination suppression. Maintaining the smoothness of the perovskite film surface is crucial to ensuring the uniform deposition and structural continuity of subsequent functional layers. Furthermore, the wrinkled morphology of the film surface is often closely related to the non-uniform distribution of halides. This phenomenon inevitably causes local deviations from the ideal stoichiometry, negatively impacting the overall device performance. The dual problems of crystal morphology defects and uneven halide distribution in the perovskite film adversely affect the local chemical potential, defect distribution, and carrier dynamics, ultimately leading to performance degradation in UWBG solar cells.

[0005] To address the aforementioned issues, numerous strategies have been proposed, such as compositional manipulation, bulk doping, and interface passivation, to improve the morphology and compositional uniformity of perovskite films. Despite extensive research in this field, the fundamental understanding and precise control techniques for UWBG perovskite materials with high bromine-to-iodine ratios remain in the exploratory stage, and most technical approaches are not yet mature enough for commercial application. Therefore, further research in this area, and optimization of perovskite film fabrication processes and performance control methods, remains a crucial issue in the current development of triple-junction solar cells. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a perovskite film, a preparation method, and a perovskite triple-junction tandem solar cell. The preparation method provided by the present invention can utilize a mixed solvent to reconstruct the surface of the perovskite film, thereby obtaining a relatively smooth perovskite film surface. It can effectively polish the surface without damaging the perovskite structure, giving the perovskite film both lateral continuity and longitudinal adhesion, thus improving the quality of the perovskite film and the perovskite triple-junction tandem solar cell.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a perovskite film, the method comprising the following steps:

[0009] A perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain the perovskite film.

[0010] The polishing agent comprises a mixed solvent consisting of a first solvent and a second solvent;

[0011] The first solvent includes any one or a combination of at least two of isopropanol (IPA), hexafluoroisopropanol (HFP), methanol, ethanol, perfluoroethanol, n-butanol, ethyl acetate, dichloromethane, chloroform, toluene, anisole, or chlorobenzene;

[0012] The second solvent includes any one or a combination of at least two of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), γ-valerolactone (GVL), N-methylpyrrolidone (NMP), or 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU).

[0013] The preparation method provided by this invention uses a mixed solvent as a polishing agent. The specific selection of the first and second solvents provides suitable polarity and solubility for the mixed solvent, facilitating selective dissolution and reconstruction of the perovskite film surface. This means it can dissolve wrinkles on the perovskite film surface without destroying the integrity of the perovskite crystal structure. The perovskite film obtained by the preparation method of this invention exhibits excellent (100) crystal orientation, and the atomic arrangement of the perovskite film is more regular, which helps to improve the carrier mobility of the perovskite film and reduce carrier recombination, thereby significantly improving its performance when applied to solar cells, especially perovskite triple-junction tandem solar cells.

[0014] In some embodiments, the volume ratio of the first solvent to the second solvent is 7:1 to 100:1.

[0015] In some embodiments, the method of applying the polishing agent includes spin coating: spin coating at a speed of 3500 rpm to 4500 rpm for 35 s to 45 s.

[0016] In some embodiments, the annealing process includes a first annealing and a second annealing performed sequentially;

[0017] The temperature of the first annealing is 80℃~90℃, and the time is 3min~8min;

[0018] The second annealing temperature is 130℃~140℃, and the time is 12min~18min.

[0019] In some embodiments, the perovskite precursor solution comprises an ultrawide-bandgap perovskite precursor solution;

[0020] The ultrawide bandgap of the perovskite precursor solution corresponds to an ultrawide bandgap perovskite material with a bandgap of 1.65 eV to 2.10 eV, preferably 1.9 eV to 2.1 eV.

[0021] In some embodiments, the method of coating the perovskite precursor solution includes an antisolvent method.

[0022] In a second aspect, the present invention provides a perovskite film layer, which is prepared by the preparation method described in the first aspect.

[0023] In some embodiments, the perovskite material in the perovskite film layer includes an ultrawide-bandgap perovskite material;

[0024] The band gap of the ultrawide bandgap perovskite material is 1.65 eV to 2.10 eV, preferably 1.9 eV to 2.1 eV.

[0025] Thirdly, the present invention provides a perovskite triple-junction tandem solar cell, the perovskite triple-junction tandem solar cell comprising, stacked as follows: a first conductive layer, a first hole transport layer, a first interface modification layer, an ultrawide bandgap perovskite film layer, a first electron transport layer, a first electron blocking layer, a second conductive layer, a second hole transport layer, a second interface modification layer, a mid-bandgap perovskite film layer, a second electron transport layer, a second electron blocking layer, a third conductive layer, a third hole transport layer, a narrow bandgap perovskite film layer, a third electron transport layer, a third electron blocking layer, and a fourth conductive layer;

[0026] The ultrawide bandgap perovskite film, the medium bandgap perovskite film, or the narrow bandgap perovskite film are each independently the perovskite film described in the second aspect.

[0027] The perovskite triple-junction tandem solar cell containing the perovskite film layer provided in the second aspect of the present invention has excellent photoelectric conversion efficiency and significantly improved damp heat stability. This is because the perovskite film layer provided in the second aspect of the present invention has good interface quality, which makes the contact between the layers in the perovskite triple-junction tandem solar cell closer, reduces the negative impact of interface defects on the stability of the cell, and provides a strong guarantee for the stability of the perovskite triple-junction tandem solar cell in practical applications.

[0028] In some embodiments, the perovskite material in the ultrawide bandgap perovskite film is an ultrawide bandgap perovskite material with a bandgap of 1.65 eV to 2.10 eV, preferably 1.9 eV to 2.1 eV.

[0029] In some embodiments, the perovskite material in the medium bandgap perovskite film is a medium bandgap perovskite material with a bandgap of 1.6 eV to 1.8 eV;

[0030] In some embodiments, the perovskite material in the narrow bandgap perovskite film is a narrow bandgap perovskite material with a bandgap of 1.2~1.25 eV.

[0031] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The preparation method provided by this invention uses a mixed solvent as a polishing agent. The specific selection of the first and second solvents provides suitable polarity and solubility for the mixed solvent, facilitating selective dissolution and reconstruction of the perovskite film surface. This means it can dissolve wrinkles on the perovskite film surface without destroying the integrity of the perovskite crystal structure. The perovskite film obtained by the preparation method of this invention exhibits excellent (100) crystal orientation, and the atomic arrangement of the perovskite film is more regular, which helps to improve the carrier mobility of the perovskite film and reduce carrier recombination, thereby significantly improving its performance when applied to solar cells, especially perovskite triple-junction tandem solar cells. Attached Figure Description

[0034] Figure 1 The surface morphology diagrams are of the perovskite films provided in the comparative example, Example 1, and Example 2.

[0035] Figure 2 XRD patterns of the perovskite films provided in the comparative example, Example 1, and Example 2;

[0036] Figure 3 This is a schematic diagram of the structure of the perovskite triple-junction tandem solar cell provided by the present invention;

[0037] Figure 4 The photoelectric conversion efficiency diagrams of the perovskite triple junction tandem solar cells provided in the comparative application examples, application example 1, and application example 2 are shown.

[0038] Figure 5 The damp heat stability test diagrams are provided for the perovskite triple junction tandem solar cells in the comparison application examples, application example 1, and application example 2.

[0039] Wherein, 101 is the first conductive layer; 102 is the first hole transport layer; 103 is the first interface modification layer; 104 is the ultrawide wide bandgap perovskite film layer; 105 is the first electron transport layer; 106 is the first electron blocking layer; 201 is the second conductive layer; 202 is the second hole transport layer; 203 is the second interface modification layer; 204 is the mid-bandgap perovskite film layer; 205 is the second electron transport layer; 206 is the second electron blocking layer; 301 is the third conductive layer; 302 is the third hole transport layer; 303 is the narrow bandgap perovskite film layer; 304 is the third electron transport layer; 305 is the third electron blocking layer; and 306 is the fourth conductive layer. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0042] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0044] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0045] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0047] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0048] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0049] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0050] In a first aspect, an embodiment of the present invention provides a method for preparing a perovskite film, the method comprising the following steps:

[0051] A perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain the perovskite film.

[0052] The polishing agent comprises a mixed solvent consisting of a first solvent and a second solvent;

[0053] The first solvent includes any one or a combination of at least two of isopropanol (IPA), hexafluoroisopropanol (HFP), methanol, ethanol, perfluoroethanol, n-butanol, ethyl acetate, dichloromethane, chloroform, toluene, anisole, or chlorobenzene;

[0054] The second solvent includes any one or a combination of at least two of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), γ-valerolactone (GVL), N-methylpyrrolidone (NMP), or 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU).

[0055] The preparation method provided by this invention uses a mixed solvent as a polishing agent. The specific selection of the first and second solvents provides suitable polarity and solubility for the mixed solvent, facilitating selective dissolution and reconstruction of the perovskite film surface. This means it can dissolve wrinkles on the perovskite film surface without destroying the integrity of the perovskite crystal structure. The perovskite film obtained by the preparation method of this invention exhibits excellent (100) crystal orientation, and the atomic arrangement of the perovskite film is more regular, which helps to improve the carrier mobility of the perovskite film and reduce carrier recombination, thereby significantly improving its performance when applied to solar cells, especially perovskite triple-junction tandem solar cells.

[0056] In some embodiments, the mixed solvent may be a combination of IPA and DMF, and / or a combination of HFP and DMF.

[0057] In some embodiments, the volume ratio of the first solvent to the second solvent is 7:1 to 200:1, for example, it can be 7:1, 10:1, 20:1, 40:1, 50:1, 60:1, 80:1, 100:1, 120:1, 150:1, 160:1, 180:1 or 200:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, the method of applying the polishing agent includes spin coating: spin coating at a speed of 3500 rpm to 4500 rpm for 35 s to 45 s.

[0059] The spin coating speed is 3500rpm~4500rpm, for example, it can be 3500rpm, 3600rpm, 3800rpm, 4000rpm, 4200rpm, 4400rpm or 4500rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] The spin coating time can be 35s to 45s, for example, 35s, 36s, 38s, 40s, 42s, 44s or 45s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the annealing process includes a first annealing and a second annealing performed sequentially;

[0062] The temperature of the first annealing is 80℃~90℃, and the time is 3min~8min;

[0063] The second annealing temperature is 130℃~140℃, and the time is 12min~18min.

[0064] The temperature of the first annealing is 80℃~90℃, for example, it can be 80℃, 81℃, 82℃, 84℃, 85℃, 86℃, 88℃ or 90℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] The first annealing time is 3 to 8 minutes, for example, it can be 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes or 8 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0066] The temperature for the second annealing is 130℃~140℃, for example, it can be 130℃, 131℃, 132℃, 134℃, 135℃, 136℃, 138℃ or 140℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] The second annealing time is 12 to 18 minutes, for example, it can be 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes or 18 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the perovskite precursor solution comprises an ultrawide-bandgap perovskite precursor solution;

[0069] The band gap of the ultrawide bandgap perovskite material corresponding to the ultrawide bandgap perovskite precursor solution is 1.65 eV to 2.10 eV, for example, it can be 1.65 eV, 1.9 eV, 1.95 eV, 2 eV, 2.05 eV or 2.1 eV, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1.9 eV to 2.1 eV.

[0070] In some embodiments, the method of coating the perovskite precursor solution includes an antisolvent method.

[0071] An exemplary antisolvent method for coating an ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 800 rpm to 1200 rpm for 8 s to 10 s with an acceleration of 800 rpm / s to 1200 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 3500 rpm to 4500 rpm for 35 s to 45 s with an acceleration of 1500 rpm / s to 2500 rpm / s; and 15 s to 20 s before the end of the second spin-coating step, dropping 100 μL to 300 μL of anisole onto the substrate.

[0072] For example, the preparation method of the ultrawide bandgap perovskite precursor solution can be as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 3:1 to 5:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) with a molar ratio of (0.6 to 0.8):(0.2 to 0.4):1 are added, and the solution is filtered using a polytetrafluoroethylene membrane to obtain an ultrawide bandgap perovskite precursor solution with a concentration of 0.8 mol / L to 1 mol / L.

[0073] For example, the anti-solvent method for coating the mid-bandgap perovskite precursor solution includes: spin-coating the mid-bandgap perovskite precursor solution at a speed of 1800 rpm to 2200 rpm for 8 s to 12 s with an acceleration of 180 rpm / s to 220 rpm / s; then spin-coating the mid-bandgap perovskite precursor solution at a speed of 5500 rpm to 6500 rpm for 25 s to 35 s with an acceleration of 1500 rpm / s to 2500 rpm / s; and 8 s to 12 s before the end of the second spin-coating step, dropping 100 μL to 300 μL of anisole onto the substrate.

[0074] For example, the preparation method of the mid-bandgap perovskite precursor solution can be as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 3:1 to 5:1, add formamidinium iodide (FAI), cesium iodide (CsI), lead iodide (PbI2), and lead bromide (PbBr2) in a molar ratio of (0.75 to 0.85):(0.15 to 0.25):(0.8 to 0.9):(0.1 to 0.2), and filter using a polytetrafluoroethylene membrane to obtain a mid-bandgap perovskite precursor solution with a concentration of 1.2 mol / L to 1.6 mol / L.

[0075] An exemplary anti-solvent method for coating a narrow bandgap perovskite precursor solution includes: spin-coating the narrow bandgap perovskite precursor solution at a speed of 800 rpm to 1200 rpm for 8 s to 12 s with an acceleration of 180 rpm / s to 220 rpm / s; then spin-coating the narrow bandgap perovskite precursor solution at a speed of 3500 rpm to 4500 rpm for 35 s to 45 s with an acceleration of 800 rpm / s to 1200 rpm / s; and then, 15 s to 20 s before the end of the second spin-coating step, dropping 100 μL to 300 μL of ethyl acetate onto the substrate.

[0076] For example, the preparation method of the narrow bandgap perovskite precursor solution can be as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 1.5:1 to 2.5:1, formamidine iodide (FAI), methylamine iodide (MAI), lead iodide (PbI2), and tin iodide (SnI2) are added in a molar ratio of (0.65~0.75):(0.25~0.35):(0.45~0.55):(0.45~0.55), and SnF2 is added at 10% of the molar amount of SnI2. Tin powder (5 mg / mL), formamidine sulfinic acid (1 mg / mL), and CF3-PACl (1 mg / mL) are also added. The solution is filtered using a polytetrafluoroethylene membrane to obtain a narrow bandgap perovskite precursor solution with a concentration of 2.2 mol / L to 2.5 mol / L.

[0077] In a second aspect, an embodiment of the present invention provides a perovskite film layer, which is prepared by the preparation method described in any embodiment of the first aspect.

[0078] In some embodiments, the perovskite material in the perovskite film layer includes an ultrawide-bandgap perovskite material;

[0079] The band gap of the ultrawide bandgap perovskite material is 1.65 eV to 2.10 eV, for example, it can be 1.65 eV, 1.9 eV, 1.95 eV, 2 eV, 2.05 eV or 2.1 eV, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] Thirdly, an embodiment of the present invention provides a perovskite triple-junction tandem solar cell, the perovskite triple-junction tandem solar cell comprising a first conductive layer, a first hole transport layer, a first interface modification layer, an ultrawide bandgap perovskite film layer, a first electron transport layer, a first electron blocking layer, a second conductive layer, a second hole transport layer, a second interface modification layer, a mid-bandgap perovskite film layer, a second electron transport layer, a second electron blocking layer, a third conductive layer, a third hole transport layer, a narrow bandgap perovskite film layer, a third electron transport layer, a third electron blocking layer, and a fourth conductive layer;

[0081] The ultrawide bandgap perovskite film, the medium bandgap perovskite film, or the narrow bandgap perovskite film are each independently the perovskite film described in the second aspect.

[0082] The perovskite triple-junction tandem solar cell containing the perovskite film layer provided in the second aspect of the present invention has excellent photoelectric conversion efficiency and significantly improved damp heat stability. This is because the perovskite film layer provided in the second aspect of the present invention has good interface quality, which makes the contact between the layers in the perovskite triple-junction tandem solar cell closer, reduces the negative impact of interface defects on the stability of the cell, and provides a strong guarantee for the stability of the perovskite triple-junction tandem solar cell in practical applications.

[0083] In some embodiments, the material of the first conductive layer may be ITO and / or FTO.

[0084] The material of the first hole transport layer can be any one or a combination of at least two of nickel oxide, PTAA, or PEDOT:PSS.

[0085] The material of the first interface modification layer can be any one or a combination of at least two of Me-4PACz, MeO-2PACz, or Me-4PACz / MeO-2PACz.

[0086] The material of the first electron transport layer can be C. 60And / or PCBM.

[0087] The material of the first electron blocking layer can be tin oxide.

[0088] The material of the second conductive layer can be ITO and / or IZO.

[0089] The material of the second hole transport layer can be any one or a combination of at least two of nickel oxide, PTAA, or PEDOT:PSS.

[0090] The material of the second interface modification layer can be any one or a combination of at least two of Me-4PACz, MeO-2PACz, or Me-4PACz / MeO-2PACz.

[0091] The material of the second electron transport layer can be C. 60 And / or PCBM.

[0092] The material for the second electron blocking layer can be tin oxide.

[0093] The material of the third conductive layer can be gold (Au).

[0094] The material of the third hole transport layer can be any one or a combination of at least two of nickel oxide, PTAA, or PEDOT:PSS.

[0095] The material of the third electron transport layer can be C. 60 And / or PCBM.

[0096] The material for the third electron blocking layer can be tin oxide.

[0097] The material of the fourth conductive layer can be any one of copper (Cu), silver (Ag), or Au, or a combination of at least two of them.

[0098] In some embodiments, the perovskite material in the ultrawide bandgap perovskite film is an ultrawide bandgap perovskite material with a bandgap of 1.65 eV to 2.10 eV, preferably 1.9 eV to 2.1 eV.

[0099] For example, the perovskite material in the ultrawide bandgap perovskite film can be FA. 0.7 Cs 0.3 PbIBr2.

[0100] In some embodiments, the perovskite material in the medium bandgap perovskite film is a medium bandgap perovskite material with a bandgap of 1.6 eV to 1.8 eV;

[0101] For example, the perovskite material in the mid-bandgap perovskite film can be FA. 0.8 Cs 0.2 Pb(I0.8 Br 0.2 3.

[0102] In some embodiments, the perovskite material in the narrow bandgap perovskite film is a narrow bandgap perovskite material with a bandgap of 1.2~1.25 eV.

[0103] For example, the narrow bandgap perovskite material in the narrow bandgap perovskite film can be FA. 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3.

[0104] control group

[0105] This control group provides a method for preparing a perovskite film, including the following steps:

[0106] An ultrawide-bandgap perovskite precursor solution was coated onto the substrate surface and then annealed to obtain a perovskite film.

[0107] The coating of the ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 1000 rpm for 10 s with an acceleration of 1000 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 4000 rpm for 40 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 20 s before the end of the second spin-coating step.

[0108] The preparation method of the ultrawide-bandgap perovskite precursor solution is as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 4:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) at a molar ratio of 0.7:0.3:1 are added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain the ultrawide-bandgap perovskite material (FAI). 0.7 Cs 0.3 A solution of ultrawide-bandgap perovskite precursor with a concentration of 0.9 mol / L (PbIBr2).

[0109] The annealing process includes a first annealing and a second annealing performed sequentially; wherein the temperature of the first annealing is 85°C and the time is 5 min; and the temperature of the second annealing is 135°C and the time is 15 min.

[0110] Example 1

[0111] This embodiment provides a method for preparing a perovskite film, including the following steps:

[0112] An ultrawide-bandgap perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain a perovskite film.

[0113] The coating of the ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 1000 rpm for 10 s with an acceleration of 1000 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 4000 rpm for 40 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 20 s before the end of the second spin-coating step.

[0114] The preparation method of the ultrawide-bandgap perovskite precursor solution is as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 4:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) at a molar ratio of 0.7:0.3:1 are added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain the ultrawide-bandgap perovskite material (FAI). 0.7 Cs 0.3 A solution of ultrawide-bandgap perovskite precursor with a concentration of 0.9 mol / L (PbIBr2).

[0115] The polishing agent is IPA and DMF in a volume ratio of 30:1; the method of applying the polishing agent is spin coating at a speed of 4000 rpm for 40 seconds.

[0116] The annealing process includes a first annealing and a second annealing performed sequentially; wherein the temperature of the first annealing is 85°C and the time is 5 min; and the temperature of the second annealing is 135°C and the time is 15 min.

[0117] Example 2

[0118] This embodiment provides a method for preparing a perovskite film, including the following steps:

[0119] An ultrawide-bandgap perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain a perovskite film.

[0120] The coating of the ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 1000 rpm for 10 s with an acceleration of 1000 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 4000 rpm for 40 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 20 s before the end of the second spin-coating step.

[0121] The preparation method of the ultrawide-bandgap perovskite precursor solution is as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 4:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) at a molar ratio of 0.7:0.3:1 are added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain the ultrawide-bandgap perovskite material (FAI). 0.7 Cs 0.3 A solution of ultrawide-bandgap perovskite precursor with a concentration of 0.9 mol / L (PbIBr2).

[0122] The polishing agent is a mixture of HFP and DMF in a volume ratio of 30:1; the polishing agent is applied by spin coating at a speed of 4000 rpm for 40 seconds.

[0123] The annealing process includes a first annealing and a second annealing performed sequentially; wherein the temperature of the first annealing is 85°C and the time is 5 min; and the temperature of the second annealing is 135°C and the time is 15 min.

[0124] The surface morphology of the perovskite films provided in the comparative example, Example 1, and Example 2 are as follows: Figure 1 As shown, by Figure 1 It is known that the surface of the perovskite film after antisolvent extraction has obvious wrinkles, which still exist after annealing. However, after treatment with polishing agent (IPA / DMF) in Example 1 or polishing agent (HFP / DMF) in Example 2, the wrinkles on the surface of the perovskite film after antisolvent extraction disappear. Effective surface polishing is achieved without damaging the surface integrity of the perovskite film, and the wrinkles are effectively alleviated after annealing.

[0125] The XRD patterns of the perovskite films provided in the comparative example, Example 1, and Example 2 are as follows: Figure 2 As shown, by Figure 2It is evident that after treatment with the polishing agent (IPA / DMF) in Example 1 or the polishing agent (HFP / DMF) in Example 2, the perovskite film exhibits a superior (100) crystal orientation compared to the perovskite film obtained in the control example. This indicates that the preparation method of the present invention not only effectively improves the surface morphology of the perovskite film but also significantly enhances the crystal quality of the film. The crystal orientation of perovskite materials has a crucial impact on their electronic and optical properties, especially in applications such as solar cells, where crystal quality directly affects the efficiency and stability of the device. A superior (100) crystal orientation means that the atomic arrangement inside the perovskite film is more regular. This regular arrangement helps to improve the carrier mobility of the perovskite film and reduce carrier recombination, thereby significantly improving the overall performance of the device. The preparation method provided by the present invention optimizes the surface structure of the perovskite film, removes surface defects and irregular crystals, and thus enhances the crystal integrity of the film, laying a more solid foundation for the application of perovskite materials in optoelectronic devices.

[0126] Example 3

[0127] This embodiment provides a method for preparing a perovskite film, including the following steps:

[0128] An ultrawide-bandgap perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain a perovskite film.

[0129] The coating of the ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 1000 rpm for 10 s with an acceleration of 1000 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 4000 rpm for 40 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 20 s before the end of the second spin-coating step.

[0130] The preparation method of the ultrawide-bandgap perovskite precursor solution is as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 4:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) at a molar ratio of 0.7:0.3:1 are added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain the ultrawide-bandgap perovskite material (FAI). 0.7 Cs 0.3 A solution of ultrawide-bandgap perovskite precursor with a concentration of 0.9 mol / L (PbIBr2).

[0131] The polishing agent is a mixture of IPA and DMF in a volume ratio of 7:1; the polishing agent is applied by spin coating at a speed of 3500 rpm for 45 seconds.

[0132] The annealing process includes a first annealing and a second annealing performed sequentially; wherein the temperature of the first annealing is 80°C and the time is 8 min; and the temperature of the second annealing is 130°C and the time is 18 min.

[0133] Example 4

[0134] This embodiment provides a method for preparing a perovskite film, including the following steps:

[0135] An ultrawide-bandgap perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain a perovskite film.

[0136] The coating of the ultrawide-bandgap perovskite precursor solution includes: spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 1000 rpm for 10 s with an acceleration of 1000 rpm / s; then spin-coating the ultrawide-bandgap perovskite precursor solution at a speed of 4000 rpm for 40 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 20 s before the end of the second spin-coating step.

[0137] The preparation method of the ultrawide-bandgap perovskite precursor solution is as follows: In a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 4:1, formamidinium iodide (FAI), cesium iodide (CsI), and lead bromide (PbBr2) at a molar ratio of 0.7:0.3:1 are added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain the ultrawide-bandgap perovskite material (FAI). 0.7 Cs 0.3 A solution of ultrawide-bandgap perovskite precursor with a concentration of 0.9 mol / L (PbIBr2).

[0138] The polishing agent is IPA and DMF in a volume ratio of 100:1; the method of applying the polishing agent is spin coating at a speed of 4500 rpm for 35 seconds.

[0139] The annealing process includes a first annealing and a second annealing performed sequentially; wherein the temperature of the first annealing is 90°C and the time is 3 min; and the temperature of the second annealing is 140°C and the time is 12 min.

[0140] Comparison of application examples

[0141] This comparative application example provides a perovskite triple-junction tandem solar cell, the schematic diagram of which is shown below. Figure 3 As shown, it includes a first conductive layer 101 (ITO), a first hole transport layer 102 (nickel oxide), a first interface modification layer 103 (Me-4PACz), an ultrawide wide-bandgap perovskite film layer 104, and a first electron transport layer 105 (C) stacked together. 60The structure consists of a first electron blocking layer 106 (SnO2), a second conductive layer 201 (ITO), a second hole transport layer 202 (nickel oxide), a second interface modification layer 203 (Me-4PACz), a mid-bandgap perovskite film layer 204, and a second electron transport layer 205 (C). 60 The structure consists of a second electron blocking layer 206 (SnO2), a third conductive layer 301 (Au), a third hole transport layer 302 (PEDOT:PSS), a narrow bandgap perovskite film layer 303, and a third electron transport layer 304 (C). 60 The preparation method includes the following steps: a third electron blocking layer 305 (SnO2) and a fourth conductive layer 306 (Cu).

[0142] S1. ITO is cleaned sequentially with detergent, deionized water and anhydrous ethanol to obtain the first conductive layer;

[0143] S2. Spin-coat nickel oxide nanoparticles (15 mg / mL nickel oxide slurry prepared with deionized water) onto the surface of the first conductive layer at 4000 rpm for 10 s, and anneal at 100°C for 10 min in air atmosphere to obtain the first hole transport layer.

[0144] S3. Spin-coat Me-4PACz solution onto the surface of the first hole transport layer, and then anneal at 100°C for 5 min to obtain the first interface modification layer;

[0145] S4. Following the preparation method of the control group, an ultrawide-bandgap perovskite precursor solution was coated on the surface of the first interface modification layer, and then annealed to obtain an ultrawide-bandgap perovskite film.

[0146] S5. Thermally evaporate a C film with a thickness of 26 nm onto the surface of the ultrawide wide-bandgap perovskite film. 60 The first electron transport layer is obtained; then SnO2 is deposited at 75°C in an ALD device (Veeco Savannah S200) to obtain the first electron blocking layer; then an ITO film with a thickness of 10 nm is deposited on the surface of the first electron blocking layer by radio frequency magnetron sputtering to obtain the second conductive layer.

[0147] S6. A nickel oxide nanocrystal solution (15 mg / mL, water to isopropanol volume ratio of 3:1) was spin-coated onto the surface of the second conductive layer at 4000 rpm for 10 s, and then annealed at 100 °C for 10 min in air to obtain the second hole transport layer; then Me-4PACz solution was spin-coated onto the surface of the second hole transport layer, and then annealed at 100 °C for 5 min to obtain the second interface modification layer.

[0148] S7. Coat the surface of the second interface modification layer with a medium band gap perovskite precursor solution and anneal at 100°C for 10 min to obtain a medium band gap perovskite film.

[0149] The coating of the mid-bandgap perovskite precursor solution includes: spin-coating the mid-bandgap perovskite precursor solution at 2000 rpm for 10 s with an acceleration of 200 rpm / s; then spin-coating the mid-bandgap perovskite precursor solution at 6000 rpm for 30 s with an acceleration of 2000 rpm / s; and adding 150 μL of anisole 10 s before the end of the second spin-coating step.

[0150] The method for preparing the mid-bandgap perovskite precursor solution is as follows: Formamidinium iodide (FAI), cesium iodide (CsI), lead iodide (PbI2), and lead bromide (PbBr2) are added to a mixed solvent of DMF and DMSO in a volume ratio of 4:1 in a molar ratio of 0.8:0.2:0.85:0.15. The solution is then filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain a mid-bandgap perovskite precursor solution with a concentration of 1.5 mol / L.

[0151] S8. A C film with a thickness of 26 nm is thermally evaporated onto the surface of a mid-bandgap perovskite film. 60 The second electron transport layer is obtained; then SnO2 is deposited at 75°C in an ALD device (Veeco Savannah S200) to obtain the second electron blocking layer; then a gold cluster layer is deposited on the surface of the second electron blocking layer by thermal evaporation to obtain the third conductive layer.

[0152] S9. Spin-coat PEDOT:PSS onto the surface of the third conductive layer and anneal it in air at 120°C for 20 min to obtain the third hole transport layer.

[0153] S10. Coat the surface of the third hole transport layer with a narrow bandgap perovskite precursor solution and anneal at 100°C for 10 min to obtain a narrow bandgap perovskite film.

[0154] The coating of the narrow bandgap perovskite precursor solution includes: spin coating the narrow bandgap perovskite precursor solution at 1000 rpm for 10 s with an acceleration of 200 rpm / s; then spin coating the narrow bandgap perovskite precursor solution at 4000 rpm for 40 s with an acceleration of 1000 rpm / s; and 20 s before the end of the second spin coating step, adding 150 μL of ethyl acetate.

[0155] The preparation method of the narrow bandgap perovskite precursor solution is as follows: In a mixed solvent of DMF and DMSO with a volume ratio of 2:1, formamidine iodide (FAI), methylamine iodide (MAI), lead iodide (PbI2), and tin iodide (SnI2) with a molar ratio of 0.7:0.3:0.5:0.5 are added, along with SnF2 at 10% of the SnI2 molar amount. Tin powder (5 mg / mL), formamidine sulfinic acid (1 mg / mL), and CF3-PACl (1 mg / mL) are also added. The solution is filtered through a 0.22 μm polytetrafluoroethylene membrane to obtain a narrow bandgap perovskite precursor solution with a concentration of 2.4 mol / L.

[0156] S11. The EDAI2 post-treatment solution was dropped onto the surface of the narrow bandgap perovskite film, and spin-coated at 4000 rpm for 15 s. Then, a 20 nm thick C layer was thermally evaporated at a rate of 0.2 Å / s. 60 The third electron transport layer is obtained; then, in the ALD device (Veeco Savannah S200), a SnO2 layer with a thickness of 20 nm is deposited at 75 °C to obtain the third electron blocking layer; then, Cu with a thickness of 150 nm is deposited on the surface of the third electron blocking layer by thermal evaporation to obtain the fourth conductive layer.

[0157] The current density of the intermediate bandgap perovskite sub-cell is 23.7 mA / cm². 2 The open-circuit voltage is 1.197V, the fill factor is 83.2%, and the photoelectric conversion efficiency is 23.6%; the current density of the narrow-bandgap perovskite sub-cell is 31.3mA / cm². 2 The open-circuit voltage is 0.882V, the fill factor is 79.9%, and the photoelectric conversion efficiency is 22.1%.

[0158] Application Example 1

[0159] This application example provides a perovskite triple junction tandem solar cell, which is the same as the comparative application example except for step S4.

[0160] Step S4 of this application example is as follows: following the preparation method of Example 1, an ultrawide-bandgap perovskite precursor solution is coated on the surface of the first interface modification layer, and then annealed to obtain an ultrawide-bandgap perovskite film.

[0161] Application Example 2

[0162] This application example provides a perovskite triple junction tandem solar cell, which is the same as the comparative application example except for step S4.

[0163] Step S4 of this application example is as follows: following the preparation method of Example 2, an ultrawide-bandgap perovskite precursor solution is coated on the surface of the first interface modification layer, and then annealed to obtain an ultrawide-bandgap perovskite film.

[0164] Application Example 3

[0165] This application example provides a perovskite triple junction tandem solar cell, which is the same as the comparative application example except for step S4.

[0166] Step S4 of this application example is as follows: following the preparation method of Example 3, an ultrawide-bandgap perovskite precursor solution is coated on the surface of the first interface modification layer, and then annealed to obtain an ultrawide-bandgap perovskite film.

[0167] Application Example 4

[0168] This application example provides a perovskite triple junction tandem solar cell, which is the same as the comparative application example except for step S4.

[0169] Step S4 of this application example is as follows: following the preparation method of Example 4, an ultrawide-bandgap perovskite precursor solution is coated on the surface of the first interface modification layer, and then annealed to obtain an ultrawide-bandgap perovskite film.

[0170] Performance Characterization

[0171] The performance of the perovskite triple-junction tandem solar cells provided in the application examples and application examples 1 to 4 was tested under the following conditions: JV characteristic testing was conducted using a Keithley 2450 source meter at a solar simulator (Enlitech, AAA grade) with a power density of 100 mW / cm². 2 The scan was performed under light intensity, and unless otherwise specified, the JV curve was tested in a nitrogen-filled glove box at a scan rate of 10 mV / s (voltage step of 20 mV and delay time of 10 ms).

[0172] The results are shown in Table 1. Where Jsc is the current density, Voc is the open-circuit voltage, FF is the fill factor, and PCE is the photoelectric conversion efficiency.

[0173] The power conversion efficiency diagrams of perovskite triple-junction tandem solar cells are shown in the following figures: (Comparative Application Example (referred to as the control group), Application Example 1 (referred to as IPA / DMF), and Application Example 2 (referred to as HFP / DMF). Figure 4 As shown, by Figure 4It is evident that the photoelectric conversion efficiency of perovskite triple-junction tandem solar cells is effectively improved when using the perovskite thin film prepared by the method of this invention. This is closely related to the excellent crystal quality and more homogeneous perovskite surface of the perovskite film. The perovskite film obtained after polishing significantly improves photoelectric performance by enhancing the crystal quality and surface uniformity of the perovskite material, thus promoting its application potential in high-efficiency optoelectronic devices. This preparation method provides a new technical approach for achieving high efficiency in the commercial production of perovskite triple-junction tandem solar cells and also opens up new possibilities for improving the performance of other types of perovskite-based devices.

[0174] The following are the damp heat stability test graphs for perovskite triple-junction tandem solar cells, provided as a comparison of application example (denoted as control group), application example 1 (denoted as IPA / DMF), and application example 2 (denoted as HFP / DMF). Figure 5 As shown, by Figure 5 It is evident that after being placed at 85℃ and 85%RH for 120 hours, the perovskite triple-junction tandem solar cell with the perovskite thin film provided by the method of this invention still maintains an initial efficiency of over 88%, while the efficiency of the control group decreases by nearly 30%. This result highlights the important role of polishing agents in improving the heat and humidity resistance of perovskite cells. Furthermore, the polishing agent optimizes the interface quality of the perovskite film layers, resulting in tighter contact between the cell layers and reducing the negative impact of interface defects on cell stability. Thus, even under high temperature and high humidity environments, the photoelectric conversion efficiency of the cell can still be well maintained, thereby extending the cell's lifespan. This result provides a strong guarantee for the long-term stability of perovskite triple-junction tandem solar cells in practical applications and also provides a more solid technical foundation for the commercialization and large-scale application of perovskite solar cells.

[0175] Table 1

[0176]

[0177] As shown in Table 1, the perovskite film prepared by the method of this invention exhibits increased photoelectric conversion efficiency when used in a perovskite triple-junction tandem solar cell. This is because the use of polishing agent significantly optimizes the quality of the perovskite film, particularly in improving its surface smoothness and crystallinity. By reducing defects and impurities on the surface of the perovskite film, the polishing agent improves the interfacial contact quality between the perovskite film and other photoelectric layers, effectively reducing interfacial impedance and thus enhancing charge separation and transport efficiency.

[0178] In summary, the preparation method provided by this invention uses a mixed solvent as a polishing agent. The specific selection of the first and second solvents provides suitable polarity and solubility for the mixed solvent, facilitating selective dissolution and reconstruction of the perovskite film surface. This means it can dissolve wrinkles on the perovskite film surface without destroying the integrity of the perovskite crystal structure. The perovskite film obtained by the preparation method of this invention exhibits excellent (100) crystal orientation, and the atomic arrangement of the perovskite film is more regular, which helps to improve the carrier mobility of the perovskite film and reduce carrier recombination, thereby significantly improving its performance when applied to solar cells, especially perovskite triple-junction tandem solar cells.

[0179] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a perovskite film, characterized in that, The preparation method includes the following steps: A perovskite precursor solution is coated onto the substrate surface, followed by a polishing agent and annealing to obtain the perovskite film. The polishing agent comprises a mixed solvent consisting of a first solvent and a second solvent; the volume ratio of the first solvent to the second solvent is 7:1 to 100:

1. The first solvent includes any one or a combination of at least two of isopropanol, hexafluoroisopropanol, methanol, ethanol, perfluoroethanol, n-butanol, ethyl acetate, dichloromethane, chloroform, toluene, anisole, or chlorobenzene; The second solvent includes any one or a combination of at least two of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, γ-valerolactone, N-methylpyrrolidone or 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone; The annealing process includes a first annealing and a second annealing performed sequentially. The temperature of the first annealing is 80℃~90℃, and the time is 3min~8min; The second annealing temperature is 130℃~140℃, and the time is 12min~18min.

2. The preparation method according to claim 1, characterized in that, The method of applying the polishing agent includes spin coating: spin coating at a speed of 3500 rpm to 4500 rpm for 35 s to 45 s.

3. The preparation method according to claim 1, characterized in that, The perovskite precursor solution includes an ultrawide-bandgap perovskite precursor solution. The ultrawide bandgap perovskite precursor solution corresponds to an ultrawide bandgap perovskite material with a bandgap of 1.65 eV to 2.10 eV.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The method for coating the perovskite precursor solution includes the antisolvent method.

5. A perovskite film, characterized in that, The perovskite film is prepared by the preparation method according to any one of claims 1 to 4.

6. The perovskite film layer according to claim 5, characterized in that, The perovskite material in the perovskite film includes an ultrawide-bandgap perovskite material. The band gap of the ultrawide bandgap perovskite material is 1.65 eV to 2.10 eV.

7. A perovskite triple-junction tandem solar cell, characterized in that, The perovskite triple-junction tandem solar cell comprises a first conductive layer, a first hole transport layer, a first interface modification layer, an ultrawide bandgap perovskite film, a first electron transport layer, a first electron blocking layer, a second conductive layer, a second hole transport layer, a second interface modification layer, a mid-bandgap perovskite film, a second electron transport layer, a second electron blocking layer, a third conductive layer, a third hole transport layer, a narrow bandgap perovskite film, a third electron transport layer, a third electron blocking layer, and a fourth conductive layer. The ultrawide bandgap perovskite film, the medium bandgap perovskite film, or the narrow bandgap perovskite film are each independently the perovskite film as described in claim 5 or 6.

8. The perovskite triple-junction tandem solar cell according to claim 7, characterized in that, The perovskite material in the ultrawide bandgap perovskite film is an ultrawide bandgap perovskite material with a bandgap of 1.65 eV to 2.10 eV; And / or, the perovskite material in the medium bandgap perovskite film is a medium bandgap perovskite material with a bandgap of 1.6 eV to 1.8 eV; And / or, the perovskite material in the narrow bandgap perovskite film is a narrow bandgap perovskite material with a bandgap of 1.2~1.25eV.

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