Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a solar cell, a preparation method thereof and a photovoltaic module. The preparation method of the solar cell comprises the following steps: heating and melting divalent cation halide at a first temperature to enable the divalent cation halide to be in a solid-liquid mixed state; cooling the divalent cation halide to a second temperature, wherein the second temperature is the lowest temperature capable of keeping the divalent cation halide in a solid-liquid mixed state; at a second temperature, evaporating the divalent cation halide on the substrate to prepare a skeleton layer; and coating a monovalent cation solution on the skeleton layer, and annealing to prepare the perovskite layer. According to the preparation method of the solar cell, the film forming quality of the perovskite film can be improved while the evaporation rate of the framework layer is improved, and then the photoelectric conversion efficiency of the cell is improved.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] The two-step process for preparing perovskite thin films includes: transferring the battery substrate to a deposition area, depositing a divalent cationic halide, such as PbI2, as a framework layer on the substrate, then spin-coating a monovalent cationic solution onto the framework layer, followed by annealing to prepare the perovskite thin film. Because the deposition rate of divalent cationic halides, such as PbI2, is relatively slow, the process time is long to achieve the desired framework layer thickness, limiting mass production. Furthermore, the prolonged high-temperature deposition of the framework layer can result in poor perovskite film quality, thus affecting the improvement of the device's photoelectric conversion efficiency. Summary of the Invention

[0003] Based on this, some embodiments of this application provide a method for preparing a solar cell that can improve the perovskite thin film quality while increasing the evaporation rate of the framework layer, thereby improving the photoelectric conversion efficiency of the cell.

[0004] In addition, some other embodiments of this application also provide a solar cell and a photovoltaic module.

[0005] A method for fabricating a solar cell includes the following steps:

[0006] The divalent cationic halide is heated and melted at a first temperature, so that the divalent cationic halide is in a solid-liquid mixed state;

[0007] The divalent cation halide is cooled to a second temperature, which is the lowest temperature at which the divalent cation halide can maintain a solid-liquid mixed state.

[0008] At the second temperature, the divalent cation halide is vapor-deposited onto the substrate to prepare a framework layer;

[0009] A monovalent cation solution is coated onto the framework layer, and then annealed to prepare a perovskite layer.

[0010] In some embodiments, the step of heating and melting the divalent cationic halide at a first temperature includes: holding the divalent cationic halide at the first temperature for 5 min to 20 min, wherein the first temperature is the melting temperature of the divalent cationic halide + (0 to 48) °C; and / or,

[0011] The second temperature is the melting temperature of the divalent cation halide - (52~150) °C; and / or,

[0012] The divalent cationic halides include one or more of lead halides and tin halides.

[0013] In some embodiments, the divalent cationic halide includes lead iodide;

[0014] The first temperature is 402℃~450℃, and / or the second temperature is 300℃~350℃.

[0015] In some embodiments, the framework layer further includes an alkali metal halide, and the preparation steps of the framework layer further include:

[0016] The alkali metal halide is heated and melted at a third temperature to bring the alkali metal halide into a solid-liquid mixed state;

[0017] The alkali metal halide is cooled to a fourth temperature; wherein the fourth temperature is the lowest temperature at which the alkali metal halide can maintain a solid-liquid mixed state.

[0018] The substrate is co-evaporated with the divalent cation halide and the alkali metal halide at the second temperature and the fourth temperature to prepare the framework layer.

[0019] In some embodiments, the third temperature is the melting temperature of the alkali metal halide + (0~24) °C; and / or,

[0020] The fourth temperature is the melting temperature of the alkali metal halide - (186–260) °C; and / or,

[0021] The alkali metal halides include cesium halides.

[0022] In some embodiments, the alkali metal halide includes cesium bromide;

[0023] The third temperature is 636℃~660℃, and / or the fourth temperature is 400℃~450℃.

[0024] In some embodiments, the divalent cation halide and the alkali metal halide are co-distilled on the substrate for 35 min to 160 min.

[0025] In some embodiments, the grain size of the framework layer is 30nm~50nm.

[0026] In some embodiments, the solute in the monovalent cation solution includes one or more of FAI, FABr, FACl, MAI, MABr, and MACl.

[0027] In some embodiments, before the step of preparing the skeleton layer, a step of stacking a hole transport layer on the substrate is included;

[0028] The hole transport layer is made of NiO. x .

[0029] In some embodiments, the preparation method further includes the step of forming a hole-modifying layer between the hole transport layer and the perovskite layer, wherein the hole-modifying layer is made of a self-assembled monomolecular material.

[0030] In some embodiments, the substrate includes a bottom cell and a composite layer disposed on the bottom cell, wherein the perovskite layer is disposed on the side of the composite layer away from the bottom cell;

[0031] The method for preparing the solar cell further includes:

[0032] An electron transport layer is formed on the side of the perovskite layer away from the substrate;

[0033] A first transparent conductive layer is formed on the side of the electron transport layer away from the perovskite layer;

[0034] A first electrode is formed on the first transparent conductive layer, such that the first electrode is in ohmic contact with the first transparent conductive layer.

[0035] A second electrode is formed on the second transparent conductive layer of the bottom battery, so that the second electrode is in ohmic contact with the second transparent conductive layer.

[0036] A solar cell is prepared by the above-described preparation method.

[0037] A photovoltaic module includes the aforementioned solar cell and encapsulation structure, wherein the encapsulation structure is used to encapsulate the solar cell.

[0038] The solar cell fabrication method of some embodiments of this application first heats and melts a divalent cation halide at a first temperature, placing it in a solid-liquid mixed state. Then, the temperature is lowered to a second temperature. Since the divalent cation halide is still in a solid-liquid mixed state at this time, it can maintain a high evaporation rate. Evaporation is then performed on the substrate, significantly increasing the deposition rate of the framework layer. Simultaneously, because the divalent cation halide has a lower second temperature, the temperature on the substrate is reduced, resulting in a framework layer with a smaller grain size. This effectively increases the surface area, increasing the contact area between the framework layer and subsequent monovalent cations, which is more conducive to the full reaction between the framework layer and the monovalent cations. This achieves better perovskite film formation, thereby improving the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a process flow for the fabrication method of a solar cell according to some embodiments of this application;

[0041] Figure 2 This is a schematic diagram of a process flow for the fabrication method of a solar cell according to other embodiments of this application;

[0042] Figure 3 This is a schematic diagram of the structure of a solar cell according to some embodiments of this application.

[0043] Explanation of reference numerals in the attached figures: bottom cell 100, top cell 200, composite layer 300, silicon substrate 110, first intrinsic amorphous silicon layer 120, second intrinsic amorphous silicon layer 130, N-type doped layer 140, P-type doped layer 150, second transparent conductive layer 160, second electrode 170, hole transport layer 210, hole modification layer 220, perovskite layer 230, passivation layer 240, electron transport layer 250, buffer layer 260, first transparent conductive layer 270, antireflection layer 280, and first electrode 290. Detailed Implementation

[0044] To facilitate understanding of this application, a more comprehensive description of the application will be provided below in conjunction with specific embodiments. Preferred embodiments of the application are given in the specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0047] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0048] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0049] In this application, "one or more" refers to any one, two, or more of the listed items. "Multiple" refers to any two or more of the listed items.

[0050] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0051] In this application, terms such as "further," "even more," "particularly," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later, but should not be construed as limiting the preceding technical solution or restricting the scope of protection herein. Unless otherwise specified herein, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0052] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.

[0053] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0054] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0055] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this application, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.

[0056] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. 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 application can be combined with other embodiments.

[0057] In the flowchart of this application, although the steps are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps. They can be executed in other orders. Moreover, at least some of the steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or in turn with at least some of other steps or other sub-steps or stages.

[0058] As described in the background section, traditional framework layer fabrication processes are time-consuming. To address the slow deposition rate of the framework layer, researchers often increase the deposition rate by raising the evaporation temperature of evaporation sources such as PbI2 and CsBr. However, this increased temperature leads to larger grain sizes in the framework layer film, hindering the full reaction between the framework layer and the monovalent cation solution, resulting in poor perovskite film quality. Therefore, increasing the deposition temperature only solves the mass production problem but also reduces photoelectric efficiency. In another related technology, researchers increase the deposition rate of the framework layer by increasing the number of evaporation sources. For example, doubling the number of evaporation sources halves the process time. This method enables mass production. but Increasing the number of evaporation sources increases equipment investment and costs. Another related technology involves lowering the evaporation temperature of evaporation sources such as PbI2 and CsBr to achieve a smaller grain size in the framework layer. However, this method further reduces the film formation rate of the framework layer due to the lower evaporation temperature, leading to a further increase in process time and making mass production more difficult.

[0059] Therefore, the current method of evaporating the framework layer is difficult to improve the photoelectric conversion efficiency and reduce the cost at the same time as increasing the deposition rate and facilitating mass production, which limits the industrial application of high-efficiency perovskite solar cells.

[0060] Based on this, the first aspect of this application provides a method for fabricating a solar cell; please refer to [link to relevant documentation]. Figure 1 It includes the following steps:

[0061] Step S110: The divalent cationic halide is heated and melted at a first temperature, so that the divalent cationic halide is in a solid-liquid mixed state.

[0062] Step S120: Cool the divalent cation halide to a second temperature, which is the lowest temperature at which the divalent cation halide can maintain a solid-liquid mixed state.

[0063] Step S130: At the second temperature, divalent cation halides are vapor-deposited onto the substrate to prepare a framework layer.

[0064] Step S140: Coat the framework layer with a monovalent cation solution, anneal, and prepare a perovskite layer.

[0065] The solar cell fabrication method of some embodiments of this application first heats and melts a divalent cation halide at a first temperature, placing it in a solid-liquid mixed state. Then, the temperature is lowered to a second temperature. Since the divalent cation halide is still in a solid-liquid mixed state at this time, it can maintain a high evaporation rate. Evaporation is then performed on the substrate, significantly increasing the deposition rate of the framework layer. Simultaneously, because the divalent cation halide has a lower second temperature, the temperature on the substrate is reduced, resulting in a framework layer with a smaller grain size. This effectively increases the surface area, increasing the contact area between the framework layer and subsequent monovalent cations, which is more conducive to the full reaction between the framework layer and the monovalent cations. This achieves better perovskite film formation, thereby improving the photoelectric conversion efficiency of the solar cell.

[0066] Furthermore, the solar cell fabrication method using some embodiments of this application, compared to the traditional method of adding an evaporation source, enables rapid film formation of the framework layer without increasing equipment costs, thus saving equipment costs. Using this framework layer deposition method, even with the same evaporation source temperature and unidirectional heating, the substrate temperature remains the same. However, the new method effectively reduces the time the substrate spends at this temperature, thereby reducing the grain size of the framework layer and facilitating perovskite film formation.

[0067] In some embodiments, the step of heating and melting the divalent cationic halide at a first temperature includes: holding the divalent cationic halide at the first temperature for 5 min to 20 min, wherein the first temperature is the melting temperature of the divalent cationic halide + (0 to 48) °C. For example, the difference between the first temperature and the melting temperature of the divalent cationic halide (i.e., the first temperature - the melting temperature of the divalent cationic halide) may be, but is not limited to, 0 °C, 2 °C, 5 °C, 8 °C, 10 °C, 12 °C, 15 °C, 18 °C, 20 °C, 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, 36 °C, 38 °C, 40 °C, 42 °C, 44 °C, 46 °C, 48 °C, or any combination of these values. The holding time may be, but is not limited to, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, or any combination of these values.

[0068] Experiments have shown that optimizing the initial temperature and holding time is beneficial for obtaining a suitable evaporation rate and grain size, thereby improving the quality of perovskite film formation. Specifically, using an appropriate initial temperature and holding time helps to ensure a suitable amount of material melted from the evaporation source, reducing the risk of a low evaporation rate after subsequent cooling due to a small amount of melted material. Simultaneously, it reduces the risk of material waste and a small grain size due to excessive melted material before deposition, or a rapid evaporation rate. If the grain size is small, the framework layer is denser with fewer gaps, making subsequent monovalent cation penetration difficult, resulting in a decrease in perovskite film quality.

[0069] In some embodiments, the second temperature is the melting temperature of the divalent cationic halide minus (52 to 150) °C. For example, the difference between the melting temperature of the divalent cationic halide and the second temperature (i.e., the melting temperature of the divalent cationic halide minus the second temperature) may be, but is not limited to, 52 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, or a range of any two of these values.

[0070] In some embodiments, the divalent cationic halide includes one or more of lead halide and tin halide. Specifically, the divalent cationic halide includes one or more of lead chloride, lead bromide, lead iodide, tin chloride, tin bromide, and tin iodide. In some embodiments, the divalent cationic halide includes lead iodide.

[0071] In some embodiments, the divalent cationic halide includes lead iodide, the first temperature is 402°C to 450°C, and the second temperature is 300°C to 350°C.

[0072] In some embodiments, the framework layer further includes an alkali metal halide, and the preparation step of the framework layer further includes:

[0073] The alkali metal halide is heated and melted at a third temperature, so that the alkali metal halide is in a solid-liquid mixed state;

[0074] The alkali metal halide is cooled to a fourth temperature; where the fourth temperature is the lowest temperature at which the alkali metal halide can maintain a solid-liquid mixed state.

[0075] At the second and fourth temperatures, the divalent cation halide and alkali metal halide are co-evaporated onto the substrate to prepare the framework layer.

[0076] Adding alkali metal halides to the framework layer helps to adjust the band gap of the perovskite layer and improve its stability.

[0077] In some embodiments, the third temperature is the melting temperature of the alkali metal halide + (0~24) °C. For example, the difference between the melting temperature of the alkali metal halide and the second temperature (i.e., the melting temperature of the alkali metal halide - the second temperature) may be, but is not limited to, 0 °C, 2 °C, 5 °C, 8 °C, 10 °C, 12 °C, 15 °C, 18 °C, 20 °C, 22 °C, 24 °C, or a range of any two of these values. Specifically, the step of heating and melting the alkali metal halide at the third temperature to bring it into a solid-liquid mixed state includes: holding the alkali metal halide at the third temperature for 5 min to 20 min.

[0078] In some embodiments, the fourth temperature is the melting temperature of the alkali metal halide minus (186–260) °C. For example, the difference between the melting temperature of the alkali metal halide and the fourth temperature (i.e., the melting temperature of the alkali metal halide minus the fourth temperature) may, but is not limited to, 186 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, or a range of any two of these values.

[0079] In some embodiments, the alkali metal halide includes cesium halide. Specifically, the alkali metal halide includes one or more of cesium chloride, cesium bromide, and cesium iodide. In some embodiments, the alkali metal halide includes cesium bromide.

[0080] In some embodiments, the alkali metal halide includes cesium bromide, the third temperature is 636°C to 660°C, and the fourth temperature is 400°C to 450°C.

[0081] In some embodiments, the divalent cationic halide includes lead iodide, the alkali metal halide includes cesium bromide, and the preparation steps of the framework layer include:

[0082] The lead iodide evaporation source is heated to 402℃~450℃ and held for 5min~20min, and the cesium bromide evaporation source is heated to 636℃~660℃ and held for 5min~20min, so that both lead iodide and cesium bromide are in a solid-liquid mixed state.

[0083] The lead iodide evaporation source is cooled to 300℃~350℃, and the cesium bromide evaporation source is cooled to 400℃~450℃, so that lead iodide and cesium bromide are kept in a solid-liquid mixed state. At this temperature, the lead iodide evaporation source and the cesium bromide evaporation source are co-evaporated on the substrate to prepare the framework layer.

[0084] First, the temperature of the evaporation source is raised above the melting points of PbI2 and CsBr, specifically 402℃~450℃ for PbI2 and 636℃~660℃ for CsBr. This temperature is maintained for 5-20 minutes, causing partial melting of PbI2 and CsBr, resulting in a solid-liquid mixture. Then, the PbI2 and CsBr evaporation sources are cooled to 300℃~350℃ for PbI2 and 400℃~450℃ for CsBr. This temperature maintains the solid-liquid mixture, allowing for a high evaporation rate. After the evaporation rate stabilizes, the substrate is transferred to the multi-source evaporation chamber for framework layer deposition. The resulting framework layer has a grain size between 30nm and 50nm. The smaller grain size increases the contact area with monovalent cations, facilitating the reaction between the framework layer and the monovalent cations and achieving better perovskite film formation.

[0085] In some embodiments, the grain size of the framework layer is 30 nm to 50 nm. For example, the grain size of the framework layer can be, but is not limited to, 30 nm, 32 nm, 35 nm, 36 nm, 38 nm, 40 nm, 42 nm, 45 nm, 46 nm, 48 nm, 50 nm, or any combination of these values. If the grain size of the framework layer is small, the framework layer is dense with small gaps, making it difficult for subsequent monovalent cations to penetrate, resulting in a decrease in the quality of the perovskite film. If the grain size of the framework layer is large, the larger grains reduce the contact area between the framework layer and the monovalent cation solution, which is not conducive to the reaction between the framework layer and the monovalent cations, resulting in incomplete and insufficient reaction, and thus a poor crystallinity of the perovskite film. The framework layer prepared by the preparation methods of some embodiments of this application has a suitable grain size, which can react fully and uniformly with monovalent cations, improving the film quality of the perovskite layer. Optionally, the grain size of the framework layer is 32 nm to 48 nm.

[0086] In some embodiments, the co-evaporation time of the divalent cationic halide and the alkali metal halide on the substrate is 35 min to 160 min. For example, the co-evaporation time may be, but is not limited to, 35 min, 40 min, 45 min, 50 min, 60 min, 80 min, 100 min, 120 min, 140 min, 150 min, 160 min, or any combination of these values.

[0087] In some embodiments, the pressure in the evaporation chamber is 1×10⁻⁶. -3 Below Pa.

[0088] In some embodiments, the solute in the monovalent cation solution includes one or more of FAI, FABr, FACl, MAI, MABr, and MACl. The solvent in the monovalent cation solution includes one or both of anhydrous ethanol and isopropanol.

[0089] It is understood that the specific composition of the monovalent cation solution is not particularly limited in this application and can be any composition commonly used in the field, which will not be elaborated here.

[0090] In some of these embodiments, the concentration of FAI is 0.3 mol / L to 0.6 mol / L, the concentration of FABr is 0 to 0.6 mol / L, the concentration of MAI is 0 to 0.2 mol / L, the concentration of MABr is 0 mol / L to 0.2 mol / L, and the concentration of MACl is 0 mol / L to 0.15 mol / L.

[0091] In some embodiments, prior to the step of preparing the skeleton layer, a step of stacking a hole transport layer on the substrate is included;

[0092] The materials for the hole transport layer include nickel oxide (NiO). x ).

[0093] Specifically, the hole transport layer has a thickness of 20 nm to 30 nm. In some embodiments, the hole transport layer is prepared by physical vapor deposition.

[0094] In some embodiments, a hole modification layer is further provided between the hole transport layer and the perovskite layer. The material of the hole modification layer includes a self-assembled single-molecule material (SAM). Providing a hole modification layer between the perovskite layer and the hole transport layer is beneficial for improving the energy level matching between the hole transport layer and the perovskite layer, and avoids the presence of Ni in the hole transport layer. 3+ Ni 4+ Oxidative decomposition of perovskite thin films. In some embodiments, the hole-modifying layer material includes one or both of 2PACz and 4PACz. It is understood that only two relatively specific single-molecule self-assembly materials are given here, but are not limited thereto.

[0095] In some embodiments, the hole-modified layer is prepared using a solution method. Specifically, the preparation steps of the hole-modified layer include:

[0096] Obtain a self-assembled monomolecular material solution;

[0097] A hole-modified layer is prepared by spin-coating a self-assembled monomolecular material solution onto a hole transport layer and then annealing it.

[0098] Since the evaporation temperature of PbI2 is approximately 350℃ and that of CsBr reaches 440℃, this results in a SAM-coated substrate having a temperature above 120℃. This temperature causes SAM desorption, allowing the NiO hole transport layer to... X Exposed. And exposed NiO X Direct contact with the perovskite thin film causes energy level mismatch and also leads to oxidative decomposition of the perovskite film, resulting in a decrease in the device's open-circuit voltage (V). OC The fill factor (FF) and other properties decrease. In traditional processes, the evaporation rate is increased by raising the temperature of the evaporation source. However, this also increases the substrate temperature, leading to SAM desorption and resulting in more exposed NiO. X The hole transport layer is in direct contact with the subsequent perovskite thin film, causing an energy level mismatch, while the high-cost Ni... 3+ Ni 4+ It can also cause oxidative decomposition of perovskite films, leading to a decrease in the V of the device. OC And FF is further reduced. To address the desorption problem of SAM during the co-evaporation process of the framework layer, researchers have adopted a method of reducing the evaporation source. Although the reduction in evaporation temperature lowers the temperature of the SAM-coated battery substrate, preventing SAM desorption due to high temperatures, this protects the SAM coverage on the battery substrate and achieves V... OC While this method improves the deposition rate and FF (fine particulate air) efficiency, it further reduces the deposition rate of the framework layer and increases the processing time. Therefore, current methods for co-evaporating the framework layer all employ unidirectional heating, making it difficult to simultaneously increase the deposition rate and facilitate mass production while reducing the risk of high-temperature desorption of the SAM layer.

[0099] In some embodiments of this application, by first heating the evaporation source to above its melting point and holding it at that temperature for a certain period of time, and then cooling it down, the substrate is deposited by vapor deposition. Since the evaporation source is in a solid-liquid mixed state at this time, only a lower evaporation source temperature is needed to maintain a high evaporation rate, which can effectively improve the film formation rate of the framework layer. The SAM-coated battery substrate is then transferred to the evaporation source chamber for framework layer deposition. Due to the low temperature at this time, the temperature on the substrate is reduced, protecting the SAM from desorption and achieving better energy level matching with the perovskite film. This also further reduces the Ni... 3+ Ni 4+ The oxidative decomposition of perovskite thin films enabled the realization of device V OC The method for preparing the framework layer using some embodiments of this application achieves the same substrate temperature under the same evaporation source temperature and unidirectional heating conditions. However, the method of this application effectively reduces the time the substrate remains at this temperature, thereby reducing the risk of SAM desorption caused by prolonged high temperature. This results in better contact between SAM and the perovskite film and also avoids the formation of Ni after SAM desorption. 3+ Ni 4+ This causes oxidative decomposition of the perovskite. Therefore, the framework layer evaporation method of some embodiments of this application can effectively improve the film formation rate of the framework layer, while also achieving better energy level matching between SAM and perovskite and reducing oxidative decomposition of the perovskite, thereby improving the Vt of the device. OC And FF, finally realizing a method for mass production of the skeleton layer of high-efficiency devices.

[0100] In some embodiments, the method for fabricating a solar cell further includes the step of forming an electron transport layer on the side of the perovskite layer away from the substrate.

[0101] In some embodiments, the material of the electron transport layer includes C 60 And one or two of PCBMs. Specifically, the thickness of the electron transport layer is 10nm~30nm. Specifically, the electron transport layer is prepared by vapor deposition.

[0102] In some embodiments, a passivation layer is further provided between the perovskite layer and the electron transport layer. Specifically, the material of the passivation layer includes LiF. The thickness of the passivation layer is 1 nm to 5 nm. In some embodiments, the passivation layer is prepared by vapor deposition. By providing a passivation layer, it is beneficial to passivate interface defects between the electron transport layer and the perovskite layer.

[0103] In some embodiments, the substrate is a transparent conductive glass, and the method for fabricating the solar cell further includes forming a counter electrode on the side of the electron transport layer away from the substrate. In this case, the solar cell is a single-junction cell. Specifically, the counter electrode can be formed using methods commonly used in the art, such as vapor deposition. The material of the counter electrode can be one or more of silver (Ag), copper (Cu), and aluminum (Al).

[0104] In other embodiments, the substrate includes a bottom battery and a composite layer disposed on the bottom battery, with the hole transport layer disposed on the side of the composite layer away from the bottom battery.

[0105] The methods for preparing solar cells also include:

[0106] A first transparent conductive layer is formed on the side of the electron transport layer away from the perovskite layer;

[0107] A first electrode is formed on the first transparent conductive layer, so that the first electrode is in ohmic contact with the first transparent conductive layer;

[0108] A second electrode is formed on the second transparent conductive layer of the bottom cell, so that the second electrode and the second transparent conductive layer form an ohmic contact.

[0109] Specifically, the bottom cell includes a heterojunction cell. In one embodiment, the bottom cell includes a silicon substrate and intrinsic amorphous silicon layers disposed on opposite sides of the silicon substrate, an N-type doped layer and a P-type doped layer disposed on the side of the intrinsic amorphous silicon layer away from the silicon substrate, and a second transparent conductive layer disposed on the side of the P-type doped layer away from the silicon substrate.

[0110] In some embodiments, the thickness of each intrinsic amorphous silicon layer is independently 5 nm to 12 nm. The thickness of the N-type doped layer is 5 nm to 25 nm. The thickness of the P-type doped layer is 10 nm to 30 nm.

[0111] While perovskite / crystalline silicon tandem solar cells have undergone rapid development and their advantages have become quite apparent, some existing problems have also become increasingly significant as efficiency has gradually improved. During the research process, it was found that in the two-step perovskite film deposition method, the framework layer plays a crucial role in the photoelectric conversion efficiency of perovskite / crystalline silicon tandem solar cells. In some embodiments of this application, optimizing the framework layer fabrication process is beneficial to improving the photoelectric conversion efficiency of perovskite / crystalline silicon tandem solar cells.

[0112] In some embodiments, the composite layer is prepared by magnetron sputtering. Specifically, the material of the composite layer includes one or both of indium tin oxide (ITO) and indium zinc oxide (IZO). It is understood that the material of the composite layer is not limited to these two; other materials commonly used in the art can also be used, as long as they possess high mobility and high transmittance. Specifically, the thickness of the composite layer is 20 nm to 30 nm.

[0113] In some embodiments, the material of the first transparent conductive layer includes one or both of ITO and IZO. Specifically, the thickness of the first transparent conductive layer is 80 nm to 120 nm. In some embodiments, the first transparent conductive layer is prepared by magnetron sputtering.

[0114] In some embodiments, a buffer layer is further provided between the electron transport layer and the first transparent conductive layer. Specifically, the material of the buffer layer includes tin dioxide (SnO2). In some embodiments, the thickness of the buffer layer is 20 nm to 30 nm. In some embodiments, the buffer layer is prepared using atomic layer deposition (ALD).

[0115] In some embodiments, the first electrode is a metal electrode. Specifically, the material of the first electrode includes one or more of silver (Ag), copper (Cu), and aluminum (Al). Specifically, the thickness of the first electrode is 150 nm to 300 nm. In some embodiments, the first electrode is prepared by vapor deposition.

[0116] In some embodiments, the second electrode is a metal electrode. Specifically, the material of the second electrode includes one or more of silver (Ag), copper (Cu), and aluminum (Al). Specifically, the thickness of the second electrode is 150 nm to 300 nm. In some embodiments, the second electrode is prepared by vapor deposition.

[0117] In some embodiments, an antireflection layer is further provided on the side of the first transparent conductive layer away from the electron transport layer. Specifically, the material of the antireflection layer includes one or both of MgF2 and LiF. Specifically, the thickness of the antireflection layer is 100 nm to 120 nm. In some embodiments, the antireflection layer is prepared by vapor deposition.

[0118] In some embodiments, please refer to Figure 2 The fabrication method of solar cells includes the following steps:

[0119] Step S210: Prepare a first intrinsic amorphous silicon layer and a second intrinsic amorphous silicon layer on the light-receiving side and the back-light-receiving side of the silicon substrate, respectively.

[0120] Step S220: An N-type doped layer is prepared on the side of the first intrinsic amorphous silicon layer away from the silicon substrate, and a P-type doped layer is prepared on the side of the second intrinsic amorphous silicon layer away from the silicon substrate.

[0121] Step S230: Prepare a second transparent conductive layer on the side of the P-type doped layer away from the silicon substrate.

[0122] Step S240: Prepare a composite layer on the bottom cell.

[0123] Step S250: Sequentially prepare a hole transport layer and a hole modification layer on the composite layer.

[0124] Step S260: Prepare a framework layer on the hole-modified layer.

[0125] Step S270: Coat the framework layer with a monovalent cation solution, anneal, and prepare the perovskite layer.

[0126] Step S280: A passivation layer, an electron transport layer, a buffer layer, a first transparent conductive layer, and an antireflection layer are sequentially prepared on the perovskite layer.

[0127] Step S290: Prepare a first electrode in ohmic contact with the first transparent conductive layer, and prepare a second electrode in ohmic contact with the second transparent conductive layer.

[0128] Step S260 includes:

[0129] Step S261: Heat the lead iodide evaporation source to 402℃~450℃ and hold for 5min~20min, and heat the cesium bromide evaporation source to 636℃~660℃ and hold for 5min~20min, so that both lead iodide and cesium bromide are in a solid-liquid mixed state.

[0130] Step S262: Cool the lead iodide evaporation source to 300℃~350℃ and the cesium bromide evaporation source to 400℃~450℃, so that lead iodide and cesium bromide are kept in a solid-liquid mixed state.

[0131] Step S263: The substrate with the cavity-modified layer is introduced into the evaporation chamber. Under the conditions of lead iodide evaporation source temperature of 300℃~350℃ and cesium bromide evaporation source temperature of 400℃~450℃, the substrate is co-evaporated to prepare the framework layer.

[0132] The specific processes for each step are as described above and will not be repeated here.

[0133] The second aspect of this application provides a solar cell prepared by the preparation method described in the first aspect.

[0134] The solar cells of some embodiments of this application have improved open-circuit voltage and fill factor, thereby having high photoelectric conversion efficiency.

[0135] In some embodiments, please refer to Figure 3The solar cell includes a bottom cell 100, a top cell 200, and a composite layer 300 disposed between the bottom cell 100 and the top cell 200. The bottom cell 100 includes a silicon substrate 110, a first intrinsic amorphous silicon layer 120 and a second intrinsic amorphous silicon layer 130 disposed on both sides of the silicon substrate, an N-type doped layer 140 disposed on the side of the first intrinsic amorphous silicon layer 120 away from the silicon substrate 110, a P-type doped layer 150 disposed on the side of the second intrinsic amorphous silicon layer 130 away from the silicon substrate 110, a second transparent conductive layer 160 disposed on the side of the P-type doped layer 150 away from the silicon substrate 110, and a second electrode 170 forming an ohmic contact with the second transparent conductive layer 160. The top cell 200 includes a hole transport layer 210, a hole modification layer 220, a perovskite layer 230, a passivation layer 240, an electron transport layer 250, a buffer layer 260, a first transparent conductive layer 270, and an antireflection layer 280, which are sequentially stacked on the side of the composite layer 300 away from the bottom cell 100, and a first electrode 290 that forms an ohmic contact with the first transparent conductive layer 270.

[0136] Understandable, the above Figure 3 A relatively specific solar cell structure is presented, but it is not limited to this. Solar cells containing a perovskite layer and that can be prepared by a two-step method are all within the scope of this application.

[0137] A third aspect of this application provides a photovoltaic module, including the aforementioned solar cell and encapsulation structure, wherein the encapsulation structure is used to encapsulate the solar cell. The photovoltaic module is used to convert received light energy into electrical energy and transmit it to an external load.

[0138] Specifically, the encapsulation structure includes an encapsulating film and a cover plate.

[0139] In one embodiment, the photovoltaic module includes: at least one cell string, an encapsulating film, and a cover plate. The cell string is composed of multiple connected solar cells; the encapsulating film covers the surface of the cell string; and the cover plate covers the surface of the encapsulating film facing away from the cell string.

[0140] To make the objectives and advantages of this application clearer, the solar cell and its effects of this application are further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and should not be used to limit this application. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventional choices in the art. Experimental methods in the embodiments that do not specify specific conditions are implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0141] Example 1

[0142] This embodiment provides a method for fabricating a solar cell, including the following steps:

[0143] (1) An intrinsic amorphous silicon layer with a thickness of 8 nm is prepared on the light-receiving surface and the back-light-receiving surface of an N-type silicon wafer.

[0144] (2) An N-type doped nanocrystalline silicon layer with a thickness of 15 nm and a P-type doped nanocrystalline silicon layer with a thickness of 20 nm are sequentially prepared on the intrinsic amorphous silicon layer on the light-receiving side and the back-light-receiving side of the N-type silicon wafer.

[0145] (3) A 100 nm thick ITO film was prepared on a P-type doped nanocrystalline silicon layer using DC / RF magnetron sputtering.

[0146] (4) A TCO composite layer with a thickness of 20 nm was prepared on an N-type doped crystalline silicon layer, and the material was IZO.

[0147] (5) Prepare a NiO layer with a thickness of 20 nm on the composite layer. x Hole transport layer.

[0148] (6) A hole-modified layer with a thickness of 1 nm is prepared on the hole transport layer, and the material is 2PACz.

[0149] (7) Prepare a framework layer on the hole-modified layer, the steps of which include:

[0150] a. Heat the PbI2 evaporation source to 402℃ and the CsBr evaporation source to 636℃, and keep them at these temperatures for 20 minutes each.

[0151] b. Cool the PbI2 evaporation source to 330℃ and the CsBr evaporation source to 435℃ to maintain the PbI2 and CsBr in a solid-liquid mixed state. In the evaporation chamber, introduce the substrate containing the hole modification layer for co-evaporation to prepare a framework layer with a thickness of 500nm.

[0152] (8) Spin-coat an ethanol solution of monovalent cations FABr, FAI, MABr and MACl onto the framework layer. The concentration of FABr is 0.3 mol / L, the concentration of FAI is 0.45 mol / L, the concentration of MABr is 0.15 mol / L and the concentration of MACl is 0.1 mol / L. Anneal the solution to obtain a perovskite light-absorbing layer with a thickness of 800 nm.

[0153] (9) A passivation layer with a thickness of 1 nm was prepared on the perovskite light-absorbing layer, and the material was LiF.

[0154] (10) A C layer with a thickness of 20 nm was prepared on the passivation layer. 60 Electron transport layer.

[0155] (11) A buffer layer with a thickness of 20 nm is prepared on the electron transport layer, and the material is SnO2.

[0156] (12) A 90 nm thick ITO transparent conductive oxide layer was prepared on the buffer layer using DC / RF magnetron sputtering.

[0157] (13) An optical antireflection layer with a thickness of 100 nm is prepared on the transparent conductive oxide layer on the front light-receiving surface. The material is MgF2.

[0158] (14) Metal grid electrodes are fabricated on the transparent conductive oxide layers on the front and back sides to obtain a solar cell. The front metal electrode is Ag with a thickness of 300 nm, and the back metal electrode is Ag with a thickness of 300 nm.

[0159] Example 2

[0160] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0161] (1) Heat the PbI2 evaporation source to 402℃ and the CsBr evaporation source to 636℃, and keep at this temperature for 20 min.

[0162] (2) The PbI2 evaporation source was cooled to 350°C and the CsBr evaporation source was cooled to 450°C. The substrate containing the SAM layer was then evaporated to prepare the framework layer.

[0163] The other layers are the same as in Example 1, and will not be described again.

[0164] Example 3

[0165] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0166] a. Heat the PbI2 evaporation source to 450℃ and the CsBr evaporation source to 660℃, and keep them at these temperatures for 5 minutes.

[0167] b. The PbI2 evaporation source is cooled to 325℃, the CsBr evaporation source is cooled to 430℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0168] The other layers are the same as in Example 1, and will not be described again.

[0169] Example 4

[0170] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0171] a. Heat the PbI2 evaporation source to 450℃ and the CsBr evaporation source to 660℃, and keep them at these temperatures for 5 minutes.

[0172] b. The PbI2 evaporation source is cooled to 350℃, the CsBr evaporation source is cooled to 450℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0173] The other layers are the same as in Example 1, and will not be described again.

[0174] Example 5

[0175] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0176] a. Heat the PbI2 evaporation source to 430℃ and the CsBr evaporation source to 650℃, and keep them at these temperatures for 15 minutes.

[0177] b. The PbI2 evaporation source is cooled to 310℃, the CsBr evaporation source is cooled to 415℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0178] The other layers are the same as in Example 1, and will not be described again.

[0179] Example 6

[0180] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0181] a. Heat the PbI2 evaporation source to 430℃ and the CsBr evaporation source to 650℃, and keep them at these temperatures for 15 minutes.

[0182] b. The PbI2 evaporation source is cooled to 350℃, the CsBr evaporation source is cooled to 450℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0183] The other layers are the same as in Example 1, and will not be described again.

[0184] Example 7

[0185] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0186] a. Heat the PbI2 evaporation source to 450℃ and the CsBr evaporation source to 660℃, and keep them at these temperatures for 20 minutes.

[0187] b. The PbI2 evaporation source is cooled to 300℃, the CsBr evaporation source is cooled to 400℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0188] The other layers are the same as in Example 1, and will not be described again.

[0189] Example 8

[0190] This embodiment provides a method for fabricating a solar cell, which is similar to the method in Embodiment 1, except that the method for fabricating the framework layer in step (7) includes the following steps:

[0191] a. Heat the PbI2 evaporation source to 450℃ and the CsBr evaporation source to 660℃, and keep them at these temperatures for 20 minutes.

[0192] b. The PbI2 evaporation source is cooled to 350℃, the CsBr evaporation source is cooled to 450℃, and a substrate containing a SAM layer is introduced for evaporation to prepare a framework layer.

[0193] The other layers are the same as in Example 1, and will not be described again.

[0194] Examples 9-11

[0195] Examples 9-11 provide a method for preparing a solar cell, which is similar to the method in Example 1. The difference is that the method for preparing the framework layer in step (7) is different. The parameters in the method for preparing the framework layer in Examples 9-11 are shown in Table 1.

[0196] Comparative Example 1

[0197] Comparative Example 1 provides a method for preparing a solar cell, which is similar to the method in Example 1, except that the preparation method of the framework layer in step (7) includes the following steps:

[0198] A one-step unidirectional heating method was adopted, with the PbI2 evaporation source temperature raised to 350℃ and the CsBr evaporation source temperature raised to 450℃. The evaporation rate of PbI2 was 4 Å / s, and the evaporation rate of CsBr was 0.4 Å / s. At these evaporation source temperatures and rates, the framework layer was deposited. During film deposition, the substrate temperature reached 110℃. The process time was 160 min.

[0199] The other layers are the same as in Example 1, and will not be described again.

[0200] Comparative Example 2

[0201] Comparative Example 2 provides a method for preparing a solar cell, which is similar to the method in Example 1, except that the preparation method of the framework layer in step (7) includes the following steps:

[0202] A one-step unidirectional heating method was adopted, further increasing the temperature of the evaporation source compared to Comparative Example 1, thereby improving the deposition rate of the framework layer. Specifically, the PbI2 evaporation source was heated to 370°C, and the CsBr evaporation source was heated to 460°C. The evaporation rate of PbI2 was 8 Å / s, and the evaporation rate of CsBr was 0.8 Å / s. Framework layer deposition was performed at these evaporation source temperatures and rates. During film deposition, the substrate temperature reached 120°C. Due to the doubled evaporation rate, the process time was reduced by half to 80 min compared to Comparative Example 1.

[0203] The other layers are the same as in Example 1, and will not be described again.

[0204] Comparative Example 3

[0205] Comparative Example 3 provides a method for preparing a solar cell, which is similar to the method in Example 1, except that the preparation method of the framework layer in step (7) is different. In Comparative Example 3, the preparation method of the framework layer includes the following steps:

[0206] A one-step unidirectional heating method was adopted, increasing the number of evaporation sources and improving the deposition rate of the framework layer compared to Comparative Example 1. Two PbI2 evaporation sources were used, with the temperature raised to 350℃; two CsBr evaporation sources were used, with the CsBr temperature raised to 450℃. The evaporation rate of PbI2 was 4 Å / s, and the evaporation rate of CsBr was 0.4 Å / s. Framework layer deposition was performed at these evaporation source temperatures and rates. During film deposition, the substrate temperature reached 110℃. Due to the use of double the number of evaporation sources, the process time was reduced by half to 80 min compared to Comparative Example 1.

[0207] The other layers are the same as in Example 1, and will not be described again.

[0208] The process parameters for preparing the framework layer in the above embodiments and comparative examples are shown in Table 1 below. The open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the solar cells in each embodiment and comparative example were tested under the following conditions: AM 1.5G standard solar spectrum, irradiance of 1000 W / m². 2 The test results are shown in Table 2. PCE represents photoelectric conversion efficiency, expressed as %, V. oc Represents open-circuit voltage, in units of V and J. sc Represents short-circuit current density, with units of mA / cm². 2 FF represents the fill factor, expressed as a percentage. The grain sizes of the framework layer in Table 2 were obtained by XRD.

[0209] Table 1

[0210]

[0211] Table 2 shows the data for the solar cells in each embodiment and comparative example.

[0212]

[0213] As can be seen from Table 2 above, the solar cell fabrication methods of some embodiments of this application can reduce the grain size of the framework layer, improve the photoelectric conversion efficiency, and simultaneously increase the evaporation rate. Furthermore, by optimizing the process parameters in the framework layer fabrication process, it is beneficial to further improve the photoelectric conversion efficiency while obtaining a suitable evaporation rate and grain size.

[0214] Specifically, a comparison of Examples 1, 3, 5, 7, and Comparative Example 1 shows that, with the same process time as Comparative Example 1, the vapor deposition temperatures of Examples 1, 3, 5, and 7 are lower than those of Comparative Example 1, which can reduce the grain size of the framework layer and simultaneously reduce the risk of SAM desorption caused by high temperature. A comparison of Examples 2, 4, 6, 8, and Comparative Example 1 shows that, with the same vapor deposition temperature as Comparative Example 1, the process times of Examples 2, 4, 6, and 8 are significantly shorter, which can also reduce the grain size of the framework layer and simultaneously reduce the risk of SAM desorption caused by prolonged high temperature. A comparison of Examples 2, 4, 6, 8, and Comparative Example 2 shows that, with process times comparable to or even shorter than Comparative Example 2, the vapor deposition temperatures of Examples 2, 4, 6, and 8 are lower, which can reduce the grain size of the framework layer and simultaneously reduce the risk of SAM desorption caused by high temperature. As can be seen from the comparison of Examples 2, 4, 6, and 8 with Comparative Example 3, when the evaporation temperature is the same as that of Comparative Example 3, the above examples use one evaporation source, which reduces the cost, and the process time is comparable to or even lower than that of Comparative Example 3.

[0215] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0216] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for fabricating a solar cell, characterized in that, Includes the following steps: The divalent cationic halide is heated and melted at a first temperature, so that the divalent cationic halide is in a solid-liquid mixed state; The divalent cation halide is cooled to a second temperature, which is the lowest temperature at which the divalent cation halide can maintain a solid-liquid mixed state. At the second temperature, the divalent cation halide is vapor-deposited onto the substrate to prepare a framework layer; A monovalent cation solution is coated onto the framework layer, and then annealed to prepare a perovskite layer.

2. The method for preparing a solar cell according to claim 1, characterized in that, The step of heating and melting the divalent cationic halide at a first temperature includes: holding the divalent cationic halide at the first temperature for 5 min to 20 min, wherein the first temperature is the melting temperature of the divalent cationic halide + (0 to 48) °C; and / or, The second temperature is the melting temperature of the divalent cation halide - (52~150) °C; and / or, The divalent cationic halides include one or more of lead halides and tin halides.

3. The method for preparing a solar cell according to claim 2, characterized in that, The divalent cationic halides include lead iodide; The first temperature is 402℃~450℃, and / or the second temperature is 300℃~350℃.

4. The method for preparing a solar cell according to any one of claims 1 to 3, characterized in that, The framework layer further includes alkali metal halides, and the preparation steps of the framework layer further include: The alkali metal halide is heated and melted at a third temperature to bring the alkali metal halide into a solid-liquid mixed state; The alkali metal halide is cooled to a fourth temperature; wherein the fourth temperature is the lowest temperature at which the alkali metal halide can maintain a solid-liquid mixed state. The substrate is co-evaporated with the divalent cation halide and the alkali metal halide at the second temperature and the fourth temperature to prepare the framework layer.

5. The method for preparing a solar cell according to claim 4, characterized in that, The third temperature is the melting temperature of the alkali metal halide + (0~24) °C; and / or, The alkali metal halide is heated and melted at a third temperature for 5 to 20 minutes; and / or, The fourth temperature is the melting temperature of the alkali metal halide - (186–260) °C; and / or, The alkali metal halides include cesium halides.

6. The method for preparing a solar cell according to claim 5, characterized in that, The alkali metal halide includes cesium bromide; The third temperature is 636℃~660℃, and / or the fourth temperature is 400℃~450℃.

7. The method for preparing a solar cell according to claim 4, characterized in that, The co-evaporation time of the divalent cation halide and the alkali metal halide on the substrate is 35 min to 160 min.

8. The method for preparing a solar cell according to any one of claims 1-3 and 5-7, characterized in that, The grain size of the framework layer is 30nm~50nm.

9. The method for preparing a solar cell according to any one of claims 1-3 and 5-7, characterized in that, The solute in the monovalent cation solution includes one or more of FAI, FABr, FACl, MAI, MABr, and MACl.

10. The method for preparing a solar cell according to any one of claims 1-3 and 5-7, characterized in that, Prior to the step of preparing the skeleton layer, the method also includes a step of stacking a hole transport layer on the substrate; The hole transport layer is made of NiO. x .

11. The method for preparing a solar cell according to claim 10, characterized in that, The preparation method further includes the step of forming a hole modification layer between the hole transport layer and the perovskite layer, wherein the material of the hole modification layer includes a self-assembled monomolecule material.

12. The method for preparing a solar cell according to any one of claims 1-3, 5-7 and 11, characterized in that, The substrate includes a bottom cell and a composite layer disposed on the bottom cell, wherein the perovskite layer is disposed on the side of the composite layer away from the bottom cell; The method for preparing the solar cell further includes: An electron transport layer is formed on the side of the perovskite layer away from the substrate; A first transparent conductive layer is formed on the side of the electron transport layer away from the perovskite layer; A first electrode is formed on the first transparent conductive layer, such that the first electrode is in ohmic contact with the first transparent conductive layer. A second electrode is formed on the second transparent conductive layer of the bottom battery, so that the second electrode is in ohmic contact with the second transparent conductive layer.

13. A solar cell, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 12.

14. A photovoltaic module, characterized in that, Includes the solar cell and encapsulation structure of claim 13, wherein the encapsulation structure is used to encapsulate the solar cell.

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