Composite material, solar cell and preparation method and application thereof

Abstract

The invention relates to a composite material, a solar cell and a preparation method and application of the solar cell. The composite material comprises a metal organic framework and polyimide in coordination connection with the metal organic framework, preparation raw materials of the polyimide comprise aromatic dianhydride and aromatic diamine, and at least one of the aromatic dianhydride and the aromatic diamine contains a fluorine group and carboxyl. The composite material is applied between a perovskite layer and an electron transport layer of a solar cell, the stability and the electron transport capacity are improved, interface defects are reduced, and therefore the photoelectric conversion efficiency and the carrier mobility of the solar cell are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, in particular to a composite material, a solar cell and a preparation method and application thereof. BACKGROUND

[0002] With the increasing consumption of traditional fossil energy and the increasingly serious environmental pollution, actively developing and utilizing new energy has become an important task at present. Solar energy has attracted widespread attention due to its advantages of being clean and renewable. Among them, the solar cell is a device that can effectively absorb solar energy and convert it into electrical energy. However, the solar cell such as perovskite solar cell still has problems such as poor stability, easy decomposition in humid environment, poor electron transport capacity and high defect density, thereby affecting the improvement of the photoelectric conversion efficiency of the solar cell and limiting its application to a certain extent. SUMMARY

[0003] Therefore, some embodiments of the present application provide a composite material applied in a solar cell, which is beneficial to improve the stability and electron transport capacity of the cell, reduce the interface defects, and thus improve the photoelectric conversion efficiency and carrier mobility of the solar cell.

[0004] In addition, some other embodiments of the present application also provide a preparation method of the composite material, a solar cell and a preparation method and application thereof.

[0005] A composite material, comprising a metal organic framework and a polyimide coordinated connected with the metal organic framework, raw materials for preparing the polyimide comprising an aromatic dianhydride and an aromatic diamine, at least one of the aromatic dianhydride and the aromatic diamine containing a fluorine group and a carboxyl group.

[0006] In some embodiments, the raw materials for preparing the polyimide comprise hexafluoroisopropylene diphthalic anhydride and 3,5-diaminobenzoic acid.

[0007] In some embodiments, the molar ratio of the hexafluoroisopropylene diphthalic anhydride to the 3,5-diaminobenzoic acid is (1-8):1.

[0008] In some embodiments, the number average molecular weight of the polyimide is 40000 g / mol-50000 g / mol.

[0009] In some embodiments, the metal organic framework comprises one or more of MIL-101, HKUST-1 and IRMOF-1.

[0010] In some embodiments, the metal organic framework comprises one or both of MIL-101(Cr) and MIL-101(Fe).

[0011] In some embodiments, the mass percentage of the polyimide in the composite material is 1% to 5%.

[0012] In some embodiments, the mass percentage of the polyimide in the composite material is 2% to 4%.

[0013] In some embodiments, the specific surface area of the composite material is 3200 m 2 / g to 4200 m 2 / g.

[0014] In some embodiments, the specific surface area of the composite material is 3600 m 2 / g to 4000 m 2 / g.

[0015] In some embodiments, the pore volume of the composite material is 1.6 cm 3 / g to 1.9 cm 3 / g.

[0016] In some embodiments, the pore volume of the composite material is 1.7 cm 3 / g to 1.85 cm 3 / g.

[0017] A method for preparing a composite material, comprising the following steps:

[0018] obtaining a polyimide, a raw material for preparing the polyimide comprising an aromatic dianhydride and an aromatic diamine, at least one of the aromatic dianhydride and the aromatic diamine containing a fluorine group and a carboxyl group;

[0019] connecting the polyimide and a metal organic framework through a coordination bond to prepare a composite material.

[0020] In some embodiments, the step of connecting the polyimide and the metal organic framework through a coordination bond comprises:

[0021] mixing the polyimide with a metal organic framework precursor solution and performing a hydrothermal reaction at 160°C to 180°C for 18h to 24h;

[0022] wherein the metal organic framework comprises MIL-101, and the metal organic framework precursor solution comprises a water-soluble metal salt, sodium hydroxide, terephthalic acid and water, and the water-soluble metal salt comprises one or more of a water-soluble chromium salt and a water-soluble iron salt.

[0023] In some embodiments, the metal organic framework precursor solution comprises a water-soluble metal salt, sodium hydroxide, terephthalic acid and water in a molar ratio of 1:(0.5 to 2):(0.5 to 2):(278 to 300).

[0024] Use of the composite material as described above or prepared by the preparation method as described above in preparation of a solar cell.

[0025] A solar cell comprising a perovskite layer, a medium layer and an electron transport layer, the medium layer being disposed between the perovskite layer and the electron transport layer;

[0026] wherein the material of the medium layer is the composite material as described above or prepared by the preparation method as described above.

[0027] In some embodiments, the thickness of the medium layer is 10 nm to 30 nm.

[0028] In some embodiments, the thickness of the electron transport layer is 20 nm to 40 nm.

[0029] In some embodiments, the material of the electron transport layer comprises one or both of TiO2 and SnO2.

[0030] In some embodiments, the thickness of the perovskite layer is 1000 nm to 1200 nm.

[0031] In some embodiments, the material of the perovskite layer comprises one or more of MAPbI3, MAPbCl3 and MAPbBr3.

[0032] In some embodiments, the solar cell further comprises a transparent conductive substrate, a hole transport layer, a positive electrode and a negative electrode, the hole transport layer, the perovskite layer, the medium layer and the electron transport layer being sequentially stacked on the surface of the transparent conductive substrate, the positive electrode forming ohmic contact with the transparent conductive substrate, and the negative electrode forming ohmic contact with the electron transport layer.

[0033] In some embodiments, the material of the hole transport layer comprises one or both of NiO x and Cu2O.

[0034] In some embodiments, the thickness of the hole transport layer is 15 nm to 20 nm.

[0035] In some embodiments, the thickness of each of the positive electrode and the negative electrode is independently 200 nm to 300 nm.

[0036] A method for preparing a solar cell, comprising the following steps:

[0037] forming a medium layer between a perovskite layer and an electron transport layer to prepare a solar cell;

[0038] The material of the medium layer is the composite material or the composite material prepared by the preparation method.

[0039] In some embodiments, the step of forming the medium layer between the perovskite layer and the electron transport layer comprises:

[0040] applying a solution containing the composite material on the surface of the perovskite layer, annealing to prepare the medium layer;

[0041] The annealing temperature is 100-150℃, and the annealing time is 8-20min.

[0042] In some embodiments, the solvent in the solution containing the composite material comprises one or more of N,N-dimethylformamide, dichloromethane and anhydrous ethanol.

[0043] In some embodiments, the solution containing the composite material is applied on the surface of the perovskite layer by spin coating, the spin coating speed is 4000-6000rpm, and the spin coating time is 15-30s.

[0044] A photovoltaic module comprises an encapsulation structure and the solar cell or the solar cell prepared by the preparation method, and the solar cell is encapsulated by the encapsulation structure.

[0045] In view of the problems of poor stability, poor electron transport, and high interface defects of traditional solar cells, which affect the improvement of photoelectric conversion efficiency, some researchers have applied metal organic frameworks to solar cells, but the improvement of photoelectric conversion efficiency of solar cells is limited. The inventors have found that, due to the weak metal-oxygen coordination of metal organic frameworks such as MIL-101, the metal organic frameworks have strong hydrophilicity and are easily attacked by hydroxyl in water molecules, causing the collapse of the framework structure and affecting the performance. Based on this, some embodiments of the present application provide a composite material, which comprises a metal organic framework and a polyimide coordinated with the metal organic framework. The polyimide has a large number of aromatic structures and fluorine groups, has super-hydrophobic performance, and has carboxyl groups, which can be connected with the metal organic framework through coordination bonds, so that the composite material has the large specific surface area, porous structure of the metal organic framework and the super-hydrophobicity of the polyimide, and has high stability in a humid environment. When the composite material is applied to a solar cell, due to its super-hydrophobicity, the stability of the perovskite solar cell is improved, and the composite material can also form a defect passivation structure between the perovskite layer and the electron transport layer, promote the nucleation and crystallization process of the perovskite layer, and improve the crystallinity of the perovskite layer. In addition, the composite material has a large number of unsaturated active sites, which can adsorb impurity ions of the perovskite layer, passivate interface defects, reduce the interface defect density, and improve the electron transport capacity without affecting the electron transport.

[0046] Therefore, when the composite material is applied to a solar cell, the stability and electron transport capacity of the solar cell can be improved, the interface defects can be reduced, and thus the photoelectric conversion efficiency and carrier mobility of the solar cell can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 For some embodiments of the present application, a process flow chart of a preparation method of a composite material is provided.

[0049] Figure 2 For some embodiments of the present application, a structure schematic diagram of a solar cell is provided.

[0050] Figure 3 For some embodiments of the present application, a process flow chart of a preparation method of a solar cell is provided. DETAILED DESCRIPTION

[0051] For the purposes of the present application, a more complete description of which will follow, the present application will now be described more fully hereinafter with reference to the accompanying drawings. Preferred embodiments of the application are given in the detailed description. However, the application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0052] 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 in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0053] Unless otherwise indicated or contradicted by context, the terms or phrases used in this application have the following meanings:

[0054] In this application, "first", "second", etc. are used only for the purpose of description, and should not be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include at least one of the features.

[0055] In the description of the present application, "a plurality of" means at least two, for example two, three, etc., unless otherwise explicitly specified.

[0056] In this application, "one or more" means any one, any two or any two or more of the listed items. Among them, "several" means any two or more.

[0057] In this application, the percentage concentration involved, unless otherwise specified, refers to the final concentration. The final concentration refers to the proportion of the added ingredient in the system after the ingredient is added.

[0058] The word "optionally" and the like in the present application means that in some cases the present application embodiments can provide certain beneficial effects. However, in the same or other cases, other embodiments can also be optional. In addition, the description of one or more optional embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present application.

[0059] When a range of values is disclosed, the disclosure is intended to "cover" the half-way point of that range, as well as every value within the range. Further, where a range of values is provided, it is intended to include every possible subset of the values within the range. In other words, unless the context clearly dictates otherwise, to the extent that the meaning of a term in the disclosure is dependent upon any such range, it will be understood that every

[0060] In the present application, the technical features described in an open way include both the closed technical solutions consisting of the listed features and the open technical solutions containing the listed features.

[0061] The terms "comprises", "comprising", "includes", "including", "has", "having" and their conjugates, as used herein, are intended to cover the inclusions of the listed features, steps or elements, but not to the exclusion of any other features, steps or elements. In other words, the terms "comprises", "comprising", "includes", "including", "has", "having" and their conjugates, as used herein, are intended to be inclusive, rather than exclusive.

[0062] Reference throughout this specification to "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be combined with any of the other embodiments unless explicitly stated otherwise.

[0063] As described in the background, the stability of perovskite solar cells is poor, and they are easily decomposed in a humid environment. The electron transport capacity is poor, and the defect density of the electron transport layer and the perovskite layer is high, thereby affecting the improvement of the photoelectric conversion efficiency and limiting the application of perovskite solar cells. Metal-organic framework materials such as MIL-101 have a super-high specific surface area, mainly in microporous structure, with a small number of mesoporous structures, and the porosity is easy to control. When applied in perovskite solar cells, it can combine with perovskite, improve the electron transport capacity, promote the crystallization of perovskite, and improve the conversion efficiency of perovskite solar cells. However, the improvement of the photoelectric conversion efficiency of the solar cell is limited. The inventors found that metal-organic framework materials such as MIL-101 have strong hydrophilicity, mainly due to the weak metal-oxygen coordination, which is easily attacked by the hydroxyl group in the water molecule, thereby causing the collapse of the framework structure and affecting the performance.

[0064] Based on this, the application provides a composite material, which can solve the problems of poor stability and easy collapse of the framework structure of metal organic framework materials such as MIL-101, and is applied in a solar cell, thereby improving the stability of the perovskite solar cell, and also improving the electron transport property, crystallinity and interface defect density of the solar cell, and further improving the photoelectric conversion efficiency thereof.

[0065] Specifically, in a first aspect, the application provides a composite material, which comprises a metal organic framework and a polyimide coordinated with the metal organic framework, and the raw materials for preparing the polyimide comprise aromatic dianhydride and aromatic diamine, and at least one of the aromatic dianhydride and the aromatic diamine contains a fluorine group and a carboxyl group.

[0066] Metal organic framework is a kind of crystalline material with periodic network structure formed by mutual connection of metal ions or metal clusters and organic ligands, and has the advantages of high specific surface area, porosity and adjustable pore size. Polyimide is a kind of high molecular polymer with aromatic structure, fluorine group and carboxyl group, and has excellent hydrophobic property and coordination group. In some embodiments of the application, the unique pore structure of metal organic framework is combined, the metal organic framework is loaded on the surface of polyimide through coordination bond by taking polyimide as a carrier, a composite material with both the large specific surface area, porous structure of metal organic framework and the superhydrophobicity of polyimide is formed, and the composite material is used between the perovskite layer and the electron transport layer, thereby improving the stability, reducing the interface defect density and enhancing the electron transport rate.

[0067] Specifically, the obtained composite material is applied in a solar cell, and due to the superhydrophobicity, the stability of the perovskite solar cell is improved to a certain extent, and the composite material is used between the perovskite layer and the electron transport layer to form a defect passivation structure, which can promote the nucleation and crystallization process of the perovskite layer and improve the crystallinity. In addition, the composite material has a large number of unsaturated active sites, which can adsorb impurity ions of the perovskite layer, passivate interface defects and reduce the interface defect density, and the composite material is a porous material with a large number of microporous structures, which does not affect the transmission of electrons but improves the transmission capacity of electrons. Therefore, the composite material is applied in a solar cell, and the photoelectric conversion efficiency and carrier mobility of the cell can be improved.

[0068] In addition, compared with the metal organic framework alone, the polyimide introduced in the composite material of some embodiments of the application has a C-F bond and has strong electron-attracting ability, which is conducive to the transmission of electrons. And the composite material is used as a passivation layer between the perovskite layer and the electron transport layer, and since the polyimide contains nitrogen atoms, it can form a covalent N-H bond with the -H dangling bond, which is conducive to enhancing the passivation effect and reducing the interface defects.

[0069] In some embodiments, the raw materials for preparing the polyimide include hexafluoroisopropylene diphthalic anhydride (6FDA) and 3,5-diaminobenzoic acid (DABA).

[0070] In some embodiments, the molar ratio of hexafluoroisopropylene diphthalic anhydride and 3,5-diaminobenzoic acid is (1-8): 1. For example, the molar ratio of 6FDA and DABA can be, but is not limited to, 1:1, 1.2:1, 1.4:1, 1.5:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, or a range formed by any two of these values. By optimizing the molar ratio of hexafluoroisopropylene diphthalic anhydride and 3,5-diaminobenzoic acid, it is beneficial to further ensure the strong hydrophobicity of the composite material.

[0071] In some embodiments, the polyimide is P(6FDA-DABA) obtained by polymerization of monomers (hexafluoroisopropylene diphthalic anhydride) and DABA (3,5-diaminobenzoic acid), and the reaction formula is as follows: .

[0072] In some embodiments, the preparation steps of P(6FDA-DABA) include mixing 6FDA and DABA in m-cresol under an inert atmosphere, heating the reaction at 200°C for 12h to prepare the polyimide. After the reaction is completed, a purification step is further included, the reaction system is poured into methanol, filtered, the obtained solid is recrystallized in THF (tetrahydrofuran), dried, and the purified P(6FDA-DABA) is obtained. In a specific example, vacuum drying at 120°C for 24h. It can be understood that only one specific preparation method of P(6FDA-DABA) is given above, but it is not limited thereto, and those skilled in the art can also prepare P(6FDA-DABA) according to conventional technical means.

[0073] In some embodiments, the number average molecular weight of the polyimide is 40000g / mol-50000g / mol. For example, the number average molecular weight of the polyimide can be, but is not limited to, 40000g / mol, 41000g / mol, 42000g / mol, 44000g / mol, 45000g / mol, 46000g / mol, 48000g / mol, 50000g / mol, or a range formed by any two of these values.

[0074] In some embodiments, the mass percentage of the polyimide in the composite material is 1% to 5%. For example, the mass percentage of the polyimide in the composite material can be, but is not limited to, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of these values. Alternatively, the mass percentage of the polyimide in the composite material is 2% to 4%. Further alternatively, the mass percentage of the polyimide in the composite material is 3%.

[0075] The polyimide can prevent the collapse of the metal-organic framework structure, thereby improving the photoelectric conversion efficiency and electron mobility of the solar cell, but can cause the metal-organic framework part to block the pores, thereby reducing the specific surface area and pore volume of the composite material. With further increase of the mass percentage of the polyimide, the electrical performance and electron mobility of the solar cell are also reduced. Optimizing the mass percentage of the polyimide in the composite material is beneficial to obtaining better photoelectric conversion efficiency and carrier mobility of the solar cell.

[0076] In some embodiments, the metal-organic framework includes one or more of MIL-101, HKUST-1, and IRMOF-1.

[0077] In some embodiments, the MIL-101 includes one or both of MIL-101(Cr) and MIL-101(Fe). MIL-101 is a metal-organic framework formed by connecting a trimer of a metal such as chromium with terephthalic acid to form a tetrahedron, and then connecting the terephthalic acid bridges to form a three-dimensional spatial framework with a topological structure. MIL-101 mainly has a microporous structure with a small amount of mesoporous structure, and has the advantages of adjustable porosity, high specific surface area, good thermal stability, and the like.

[0078] Taking MIL-101 including MIL-101(Cr) as an example, the above composite material has Cr 3+ as the center, forms a coordination bond with the polyimide on one side through the carboxyl group, and forms a coordination bond with the terephthalic acid on the other side, thereby being bridged together to form the composite material.

[0079] The composite material of the present application introduces polyimide on the basis of the metal-organic framework, so that the prepared composite material has excellent pore volume and good gas transmission channels. At the same time, compared with the pure metal-organic framework, a small amount of mesoporous structure is introduced, the pore structure is enriched, and a composite material with hierarchical pore structure is prepared.

[0080] In some embodiments, the specific surface area of the composite material is 3200 m 2 / g to 4200 m 2 / g. For example, the specific surface area of the composite material can be, but is not limited to, 3200 m2 / g, 3200 m 2 / g, 3200 m 2 / g, 3200 m 2 / g, 3200 m 2 / g, 3200 m 2 / g, 3200 m 2 / g, or a range defined by any two of these values. Optionally, the specific surface area of the composite material is 3600 m 2 / g~4000 m 2 / g. Further optionally, the specific surface area of the composite material is 3800 m 2 / g~3900 m 2 / g.

[0081] In some embodiments, the pore volume of the composite material is 1.6 cm 3 / g~1.9 cm 3 / g. For example, the pore volume of the composite material can be, but is not limited to, 1.6 cm 3 / g, 1.62 cm 3 / g, 1.65 cm 3 / g, 1.68 cm 3 / g, 1.7 cm 3 / g, 1.72 cm 3 / g, 1.75 cm 3 / g, 1.78 cm 3 / g, 1.8 cm 3 / g, 1.82 cm 3 / g, 1.85 cm 3 / g, 1.88 cm 3 / g, 1.9 cm 3 / g, or a range defined by any two of these values. Optionally, the pore volume of the composite material is 1.7 cm 3 / g~1.85 cm 3 / g.

[0082] In a second aspect, the present application provides a method for preparing a composite material, comprising the following steps:

[0083] obtaining a polyimide, the raw materials for preparing the polyimide comprising an aromatic dianhydride and an aromatic diamine, at least one of the aromatic dianhydride and the aromatic diamine containing a fluorine group and a carboxyl group;

[0084] connecting the polyimide and the metal-organic framework through a coordination bond to prepare the composite material.

[0085] In some embodiments, the step of connecting the polyimide and the metal-organic framework through a coordination bond comprises:

[0086] The polyimide is mixed with the metal organic framework precursor solution, and a hydrothermal reaction is performed at 160-180°C for 18-24 hours.

[0087] Both the metal organic framework and the polyimide contain carboxyl groups, and the metal source in the metal organic framework acts as a coordination center. The two are bridged together through a hydrothermal reaction. The composite material can be applied to a solar cell to enhance the stability of the perovskite solar cell, improve the electron mobility, promote the nucleation and crystallization of the perovskite, and reduce the interface defect density between the perovskite layer and the electron transport layer, thereby achieving efficiency improvement of the perovskite solar cell. Experimental verification shows that the introduction of the composite material can improve the efficiency of the perovskite solar cell by more than 0.2% compared with a perovskite solar cell without the composite material, and the carrier mobility is also significantly improved.

[0088] In some embodiments, the average particle size of the polyimide is 5-10 μm.

[0089] In some embodiments, the specific surface area of the polyimide is 50-500 m 2 / g, and the pore volume is 0.2-0.8 cm 2 / g. 3 / g. 3 / g.

[0090] In some embodiments, the metal organic framework includes MIL-101, and the metal organic framework precursor solution includes a water-soluble metal salt, sodium hydroxide, terephthalic acid, and water, and the water-soluble metal salt includes one or more of a water-soluble chromium salt and a water-soluble iron salt. Optionally, the metal organic framework precursor solution includes the water-soluble metal salt, sodium hydroxide, terephthalic acid, and water in a molar ratio of 1:1:1: (278-300).

[0091] In some embodiments, the water-soluble chromium salt includes chromium nitrate nonahydrate.

[0092] In some embodiments, the metal organic framework precursor solution includes chromium nitrate nonahydrate, sodium hydroxide, terephthalic acid, and water in a molar ratio of 1:1:1: (278-300).

[0093] In a specific example, the temperature of the hydrothermal reaction can be, but is not limited to, 160°C, 162°C, 164°C, 166°C, 168°C, 170°C, 172°C, 174°C, 176°C, 178°C, 180°C, or a range formed by any two of these values. The time of the hydrothermal reaction can be, but is not limited to, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, or a range formed by any two of these values.

[0094] In some embodiments, the metal-organic framework includes MIL-101; see [link to relevant documentation]. Figure 1 The preparation steps of the composite material include:

[0095] Step S110: Mix water-soluble metal salt, alkaline reagent, terephthalic acid and water to prepare MIL-101 precursor solution.

[0096] Step S120: Mix the MIL-101 precursor solution with polyimide to prepare the composite material precursor solution.

[0097] Step S130: The composite material precursor solution is subjected to a hydrothermal reaction at 160℃~180℃ for 18h~24h to prepare the composite material.

[0098] Figure 1 This is a schematic flowchart of a method for preparing a composite material according to an embodiment of this application. It should be understood that, although Figure 1 The steps in the flowchart shown are displayed sequentially according to the arrows. However, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order requirement for the execution of these steps; they can be executed in other orders. Figure 1 At least some of the steps in the process 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 executed in turn or alternately with at least some of other steps or other sub-steps or stages.

[0099] It is understood that in some embodiments, a purification step is included after the hydrothermal reaction. Specifically, N,N-dimethylformamide and hot ethanol are added to the reaction system, followed by filtration, washing, and drying. The washing is performed with distilled water and ethanol, respectively. After the reaction, the pores of the prepared composite material contain unreacted terephthalic acid, which blocks the pores. Therefore, purification is required to remove the unreacted terephthalic acid using N,N-dimethylformamide and hot ethanol.

[0100] It is understandable that the mass percentage of polyimide in the composite material can be adjusted by controlling the mass of water-soluble metal salt, terephthalic acid, and polyimide in the composite precursor solution. Specifically, the mass percentage of polyimide in the composite material = mass of polyimide / (mass of polyimide + mass of water-soluble metal salt + mass of terephthalic acid) × 100%.

[0101] The third aspect of this application provides the application of the composite material of the first aspect above or the composite material prepared by the preparation method of the second aspect above in the preparation of solar cells.

[0102] The composite material includes a metal organic framework and a polyimide coordinated connected with the metal organic framework, the polyimide has a large number of aromatic structures and fluorine groups, has super-high hydrophobicity, the metal organic framework has super-high specific surface area and porosity, and the two are matched, the obtained composite material has both the huge specific surface area, the porous structure of the metal organic framework and the super-hydrophobicity of the polyimide, the composite material is applied between the perovskite layer and the electron transport layer of the solar cell to form a defect passivation structure, which can promote the nucleation and crystallization process of the perovskite layer, in addition, the composite material has a large number of unsaturated active sites, the unsaturated active sites can adsorb impurity ions of the perovskite layer, passivate interface defects, reduce the interface defect density, and due to the super-hydrophobicity of the introduced composite material, the stability of the perovskite solar cell is improved to a certain extent, the passivation structure is a porous material with a large number of microporous structures, which does not affect the transmission of electrons, but improves the transmission capacity of electrons. Therefore, the application of the composite material in the solar cell is beneficial to improve the photoelectric conversion efficiency and the carrier mobility of the solar cell.

[0103] The fourth aspect of the present application provides a solar cell, comprising a perovskite layer, a medium layer and an electron transport layer, the medium layer is arranged between the perovskite layer and the electron transport layer.

[0104] The material of the medium layer includes the composite material of the first aspect or the composite material prepared by the preparation method of the second aspect.

[0105] The medium layer can enhance the stability of the perovskite solar cell, improve the electron mobility, promote the nucleation and crystallization of the perovskite, and reduce the interface defect density of the perovskite layer and the electron transport layer, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. It has been verified through experiments that the introduction of the medium layer makes the efficiency of the perovskite solar cell increase by more than 0.2% compared with the efficiency of the perovskite solar cell without the medium layer, and the carrier mobility is also obviously improved.

[0106] In some embodiments, the thickness of the medium layer is 10nm-30nm. For example, the thickness of the medium layer can be, but is not limited to, 10nm, 12nm, 14nm, 15nm, 16nm, 18nm, 20nm, 22nm, 24nm, 25nm, 26nm, 28nm, 30nm or a range consisting of any two of these values.

[0107] In some embodiments, the thickness of the electron transport layer is 20 nm to 40 nm. For example, the thickness of the electron transport layer can be, but is not limited to, 20 nm, 22 nm, 24 nm, 25 nm, 26 nm, 28 nm, 30 nm, 32 nm, 34 nm, 35 nm, 36 nm, 38 nm, 40 nm, or a range between any two of these values.

[0108] In some embodiments, the material of the electron transport layer includes one or both of TiO2and SnO2.

[0109] In some embodiments, the thickness of the perovskite layer is 1000 nm to 1200 nm. For example, the thickness of the perovskite layer can be, but is not limited to, 1000 nm, 1020 nm, 1050 nm, 1080 nm, 1100 nm, 1120 nm, 1150 nm, 1180 nm, 1200 nm, or a range between any two of these values.

[0110] In some embodiments, the material of the perovskite layer includes one or more of MAPbI3, MAPbCl3, and MAPbBr3.

[0111] In some embodiments, the solar cell is a single-junction cell. Specifically, referring to Figure 2 , the solar cell 200 includes a transparent conductive substrate 210, a hole transport layer 220, a perovskite layer 230, a dielectric layer 240, an electron transport layer 250, a positive electrode 260, and a negative electrode 270. The hole transport layer 220, the perovskite layer 230, the dielectric layer 240, and the electron transport layer 250 are sequentially stacked on the surface of the transparent conductive substrate 210. The positive electrode 260 forms an ohmic contact with the transparent conductive substrate 210, and the negative electrode 270 forms an ohmic contact with the electron transport layer 250.

[0112] In some embodiments, the thickness of the transparent conductive substrate is 800 nm to 1000 nm. For example, the thickness of the transparent conductive substrate can be, but is not limited to, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, or a range between any two of these values.

[0113] In some embodiments, the material of the transparent conductive substrate includes one or more of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), and fluorine-doped tin oxide (FTO).

[0114] In some embodiments, the thickness of the hole transport layer is 15 nm to 20 nm.

[0115] In some embodiments, the material of the hole transport layer includes one or both of NiO x and Cu2O.

[0116] In some embodiments, the thickness of the positive electrode and the negative electrode is independently 200 nm to 300 nm. For example, the thickness of the positive electrode and the negative electrode is independently 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, or a range between any two of these values.

[0117] In some embodiments, the positive electrode and the negative electrode are independently a metal electrode. It can be understood that the materials of the positive electrode and the negative electrode can be the same or different.

[0118] It can be understood that the above only gives some common materials in each layer and their commonly used thickness, but is not limited thereto.

[0119] It can be understood that in some other embodiments, the solar cell can also be a stacked cell. Specifically, the solar cell comprises: a bottom cell, a hole transport layer, a perovskite layer, a dielectric layer, an electron transport layer, a positive electrode and a negative electrode; wherein the hole transport layer, the perovskite layer, the dielectric layer and the electron transport layer are sequentially stacked on the surface of the bottom cell, the positive electrode forms an ohmic contact with the bottom cell, and the negative electrode forms an ohmic contact with the electron transport layer.

[0120] When the solar cell is a stacked cell, the bottom electrode can be, for example but not limited to, a silicon cell. The materials and thicknesses of the hole transport layer, the perovskite layer, the electron transport layer, the positive electrode and the negative electrode are the same as when the solar cell is a single-junction cell, and will not be repeated here.

[0121] The fifth aspect of the present application provides a method for preparing a solar cell, comprising the following steps:

[0122] A dielectric layer is formed between the perovskite layer and the electron transport layer to prepare the solar cell. The material of the dielectric layer is the composite material of the first aspect or the composite material prepared by the method of the second aspect.

[0123] In some embodiments, the step of forming a dielectric layer between the perovskite layer and the electron transport layer comprises:

[0124] A solution containing the composite material is applied to the surface of the perovskite layer, and annealing is performed to prepare the dielectric layer. The annealing temperature is 100°C to 150°C, and the annealing time is 8 min to 20 min.

[0125] For example, the annealing temperature can be, but is not limited to, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or a range between any two of these values. The annealing time can be, but is not limited to, 8 min, 10 min, 12 min, 14 min, 15 min, 16 min, 18 min, 20 min, or a range between any two of these values.

[0126] In some embodiments, the solvent in the solution containing the composite material includes one or both of DMF (N,N-dimethylformamide), dichloromethane, and anhydrous ethanol.

[0127] In some embodiments, the solution containing the composite material is applied to the surface of the perovskite layer by spin coating. Specifically, the spin coating speed is 4000 rpm to 6000 rpm, and the spin coating time is 15 s to 30 s. For example, the spin coating speed can be, but is not limited to, 4000 rpm, 4200 rpm, 4500 rpm, 4800 rpm, 5000 rpm, 5200 rpm, 5500 rpm, 5800 rpm, 6000 rpm, or a range between any two of these values. The spin coating time can be, but is not limited to, 15 s, 18 s, 20 s, 22 s, 25 s, 28 s, 30 s, or a range between any two of these values. Further, the ambient humidity during the spin coating process is 5% to 10%.

[0128] In some embodiments, the thickness of the medium layer is 10 nm to 30 nm.

[0129] In some embodiments, the step of forming the medium layer between the perovskite layer and the electron transport layer includes: spin coating a dichloromethane solution containing the composite material on the surface of the perovskite layer at a spin coating speed of 4000 rpm to 6000 rpm and a spin coating time of 15 s to 30 s in an ambient humidity of 5% to 10%, and then annealing at 100°C to 150°C for 8 min to 20 min to form a medium layer with a thickness of 10 nm to 30 nm.

[0130] In some embodiments, the solar cell is a single-junction cell, such as Figure 2 As shown in FIG. 2, the solar cell 200 includes a transparent conductive substrate 210, a hole transport layer 220, a perovskite layer 230, a medium layer 240, an electron transport layer 250, a positive electrode 260, and a negative electrode 270. The hole transport layer 220, the perovskite layer 230, the medium layer 240, and the electron transport layer 250 are sequentially stacked on the surface of the transparent conductive substrate 210. The positive electrode 260 forms an ohmic contact with the transparent conductive substrate 210, and the negative electrode 270 forms an ohmic contact with the electron transport layer 250.

[0131] At this time, please refer to Figure 3The method for preparing the solar cell comprises the following steps:

[0132] Step S310: forming a hole transport layer on the transparent conductive substrate.

[0133] Step S320: forming a perovskite layer on the side surface of the hole transport layer away from the transparent conductive substrate.

[0134] Step S330: forming a dielectric layer on the side surface of the perovskite layer away from the transparent conductive substrate.

[0135] Step S340: forming an electron transport layer on the side surface of the dielectric layer away from the transparent conductive substrate.

[0136] Step S350: forming a negative electrode on the side surface of the electron transport layer away from the transparent conductive substrate.

[0137] Step S360: forming a positive electrode on the side surface of the transparent conductive substrate away from the hole transport layer, thereby preparing the solar cell.

[0138] In some embodiments, the transparent conductive substrate is prepared by magnetron sputtering. Specifically, the transparent conductive substrate is formed by a PVD device (physical vapor deposition device).

[0139] In some embodiments, the hole transport layer is formed by evaporation. Specifically, the hole transport layer is formed by a PVD device (physical vapor deposition device).

[0140] In some embodiments, the perovskite layer is formed by a solution method.

[0141] In some embodiments, the electron transport layer is formed by plasma deposition. Specifically, the electron transport layer is formed by an RPD device (reactive plasma deposition device).

[0142] In some embodiments, the positive electrode and the negative electrode are formed by evaporation. For example, evaporation is performed in an evaporation instrument.

[0143] The specific preparation process of each layer can be obtained according to the conventional knowledge in the art, and is not particularly limited herein.

[0144] The sixth aspect of the present application provides a photovoltaic module, comprising an encapsulation structure and the above-mentioned solar cell or comprising a solar cell prepared by the above-mentioned preparation method, and the solar cell is encapsulated by the encapsulation structure.

[0145] The encapsulation structure comprises an encapsulation frame.

[0146] In some embodiments, the photovoltaic assembly further comprises a photovoltaic glass and a photovoltaic back sheet. The photovoltaic glass is arranged on the upper surface of the solar cell to protect the solar cell. The photovoltaic back sheet is arranged on the lower surface of the solar cell to further protect the solar cell. The photovoltaic glass and the solar cell, the photovoltaic back sheet and the solar cell are connected by an encapsulating adhesive film.

[0147] It can be understood that the photovoltaic back sheet arranged on the lower surface of the solar cell can also be replaced by a photovoltaic glass.

[0148] In order to make the purposes and advantages of the present application more clear, the composite material and its effects of the present application are further described in detail below in combination with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and should not be used to limit the present application. The following examples do not include other components except for unavoidable impurities, if not otherwise specified. In the examples, the drugs and instruments are selected according to the conventional selection in the art, if not otherwise specified. The experimental methods in the examples are implemented according to the conventional conditions, for example, the conditions described in the literature, books or the methods recommended by the manufacturers.

[0149] Example 1

[0150] The present example provides a composite material, and the preparation steps are as follows:

[0151] (1) 2.22 g of 6FDA, 0.76 g of DABA and 0.27 g of m-cresol were added into a double-necked round-bottom flask under an inert atmosphere (N2), and then heated to 200°C for 12 h to make the reaction complete. Then, the reaction system was cooled, poured into 10 mL of methanol to obtain P(6FDA-DABA) powder containing impurities. The P(6FDA-DABA) powder containing impurities was re-precipitated from THF to remove residual impurities, and then the powder after removing impurities was dried in a vacuum drying oven at 120°C for 24 h to obtain purified P(6FDA-DABA) powder, and the structural formula is as follows: .

[0152] (2) 0.028 g of P(6FDA-DABA), 2 g of chromium nitrate nine hydrate, 0.2 g of sodium hydroxide, 0.83 g of terephthalic acid and 25 mL of ionized water were mixed and ultrasonicated to make the mass percentage of P(6FDA-DABA) in the composite material to be prepared to be 1%, to obtain a precursor solution B, i.e. a MIL-101 / P(6FDA-DABA) precursor solution.

[0153] (3) Pouring precursor solution B into a polytetrafluoroethylene hydrothermal reactor, and keeping it in an oven at 170°C for 24 hours to obtain an unpurified MIL-101 / P(6FDA-DABA) composite material. Adding N,N-dimethylformamide and hot ethanol to the obtained unpurified MIL-101 / P(6FDA-DABA) composite material to obtain a purified MIL-101 / P(6FDA-DABA) composite material. Washing and drying the above purified MIL-101 / P(6FDA-DABA) composite material with distilled water and ethanol to obtain a MIL-101 / P(6FDA-DABA) composite material for perovskite solar cells.

[0154] The embodiment also provides a solar cell, which comprises a transparent conductive substrate, a hole transport layer, a perovskite layer, a dielectric layer, an electron transport layer, a positive electrode and a negative electrode, the hole transport layer, the peroviskite layer, the dielectric layer and the electron transport layer are sequentially stacked on the surface of the transparent conductive substrate, the positive electrode forms an ohmic contact with the transparent conductive substrate, and the negative electrode forms an ohmic contact with the electron transport layer.

[0155] The preparation steps of the solar cell are as follows:

[0156] (1) Depositing ITO on a transparent conductive substrate by using a PVD device and a magnetron sputtering method to obtain a transparent conductive substrate with a thickness of 900 nm.

[0157] (2) Depositing Cu2O on the surface of the transparent conductive substrate by using a PVD device and an evaporation method to obtain a hole transport layer with a thickness of 18 nm.

[0158] (3) Forming MAPbI3 on the surface of the hole transport layer by using a coating machine to obtain a peroviskite layer with a thickness of 1100 nm.

[0159] (4) Dissolving the above MIL-101 / P(6FDA-DABA) composite material in dichloromethane, coating it on the peroviskite layer by a spin coating method, and then annealing it in an annealing furnace at 130°C for 15 minutes to obtain a dielectric layer with a thickness of 20 nm.

[0160] (5) Depositing SnO2 on the surface of the dielectric layer by using an RPD device to obtain an electron transport layer material with a thickness of 30 nm.

[0161] (6) Evaporating a negative electrode on the surface of the electron transport layer and a positive electrode on the surface of the transparent conductive substrate by using an evaporation instrument to obtain a solar cell. The thickness of the positive electrode is 260 nm, and the thickness of the negative electrode is 260 nm.

[0162] Example 2

[0163] The embodiment provides a composite material, and the preparation steps are similar to those in the embodiment 1, and the difference is that the mass percentage of P(6FDA-DABA) in the composite material is different, and in the embodiment, the mass percentage of P(6FDA-DABA) in the composite material is 2%, which is embodied in that the mass of the added P(6FDA-DABA) is different, and the step (2) of the embodiment is as follows:

[0164] 0.058g P(6FDA-DABA), 2g chromium nitrate nine hydrates, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonically treated, so that the mass percentage of P(6FDA-DABA) in the composite material to be prepared is 2%, and a precursor solution B, namely, a MIL-101 / P(6FDA-DABA) precursor solution, is obtained.

[0165] The other steps of the composite material are the same as those in the embodiment 1, and details are not described herein again.

[0166] The embodiment also provides a solar cell, and the difference from the embodiment 1 is that the material of the medium layer is the composite material prepared in the embodiment. The preparation steps of the solar cell are the same as those in the embodiment 1, and details are not described herein again.

[0167] Embodiment 3

[0168] The embodiment provides a composite material, and the preparation steps are similar to those in the embodiment 1, and the difference is that the mass percentage of P(6FDA-DABA) in the composite material is different, and in the embodiment, the mass percentage of P(6FDA-DABA) in the composite material is 3%, which is embodied in that the mass of the added P(6FDA-DABA) is different, and the step (2) of the embodiment is as follows:

[0169] 0.088g P(6FDA-DABA), 2g chromium nitrate nine hydrates, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonically treated, so that the mass percentage of P(6FDA-DABA) in the composite material to be prepared is 3%, and a precursor solution B, namely, a MIL-101 / P(6FDA-DABA) precursor solution, is obtained.

[0170] The other steps of the composite material are the same as those in the embodiment 1, and details are not described herein again.

[0171] The embodiment also provides a solar cell, and the difference from the embodiment 1 is that the material of the medium layer is the composite material prepared in the embodiment. The preparation steps of the solar cell are the same as those in the embodiment 1, and details are not described herein again.

[0172] Embodiment 4

[0173] The embodiment provides a composite material, and the preparation steps are similar to those in the embodiment 1, and the difference is that the mass percentage of P(6FDA-DABA) in the composite material is different, and in the embodiment, the mass percentage of P(6FDA-DABA) in the composite material is 4%, which is embodied in that the mass of the added P(6FDA-DABA) is different, and the step (2) of the embodiment is as follows:

[0174] 0.118g P(6FDA-DABA), 2g chromium nitrate nine hydrates, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonically treated, so that the mass percentage of P(6FDA-DABA) in the composite material to be prepared is 4%, and a precursor solution B, namely, a MIL-101 / P(6FDA-DABA) precursor solution, is obtained.

[0175] The other steps of the composite material are the same as those in the embodiment 1, and details are not described herein again.

[0176] The embodiment also provides a solar cell, and the difference from the embodiment 1 is that the material of the medium layer is the composite material prepared in the embodiment. The preparation steps of the solar cell are the same as those in the embodiment 1, and details are not described herein again.

[0177] Embodiment 5

[0178] The embodiment provides a composite material, and the preparation steps are similar to those in the embodiment 1, and the difference is that the mass percentage of P(6FDA-DABA) in the composite material is different, and in the embodiment, the mass percentage of P(6FDA-DABA) in the composite material is 5%, which is embodied in that the mass of the added P(6FDA-DABA) is different, and the step (2) of the embodiment is as follows:

[0179] 0.149g P(6FDA-DABA), 2g chromium nitrate nine hydrates, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonically treated, so that the mass percentage of P(6FDA-DABA) in the composite material to be prepared is 5%, and a precursor solution B, namely, a MIL-101 / P(6FDA-DABA) precursor solution, is obtained.

[0180] The other steps of the composite material are the same as those in the embodiment 1, and details are not described herein again.

[0181] The embodiment also provides a solar cell, and the difference from the embodiment 1 is that the material of the medium layer is the composite material prepared in the embodiment. The preparation steps of the solar cell are the same as those in the embodiment 1, and details are not described herein again.

[0182] Embodiment 6

[0183] The present example provides a composite material, the preparation steps are similar to those of Example 1, the difference is that the metal used in MIL-101 is iron. Specifically, in step (2), the step (2) of the present example is as follows:

[0184] (2) 0.028g P(6FDA-DABA), 2g iron chloride, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonic is applied, so that the mass percentage of P(6FDA-DABA) in the composite material to be prepared is 1%, and a precursor solution B, i.e. a MIL-101 / P(6FDA-DABA) precursor solution, is obtained.

[0185] The other steps of the composite material are the same as those of Example 1 and will not be repeated.

[0186] The present example also provides a solar cell, which is similar to Example 1, the difference is that the material of the medium layer is the composite material prepared in the present example. The preparation steps of the solar cell are the same as those of Example 1 and will not be repeated.

[0187] In Comparative Example 1, MIL-101 metal organic framework is used to replace the composite material in Example 1, and the preparation steps of MIL-101 metal organic framework are as follows:

[0188] 2g chromium nitrate nonahydrate, 0.2g sodium hydroxide, 0.83g terephthalic acid and 25mL ionized water are mixed and ultrasonic is applied, and a MIL-101 precursor solution is obtained. The MIL-101 precursor solution is poured into a polytetrafluoroethylene hydrothermal reaction kettle, and is kept in an oven at 160°C~180°C for 18h~24h, and an unpurified MIL-101 material is obtained. The obtained unpurified MIL-101 material is added with N,N-dimethylformamide and hot ethanol for purification, and a purified MIL-101 material is obtained. The purified MIL-101 material is washed with distilled water and ethanol, and is dried to obtain a MIL-101 material for perovskite solar cell.

[0189] The solar cell of Comparative Example 1 is similar to Example 1, the difference is that the material of the medium layer in the solar cell of Comparative Example 1 is MIL-101 metal organic framework, and the preparation steps of the medium layer are as follows:

[0190] The MIL-101 metal organic framework is dissolved in dichloromethane, and is coated on the perovskite layer of the perovskite solar cell by spin coating, and then is annealed in an annealing furnace, and is annealed at 130°C for 15min, and a medium layer with a thickness of 20nm is obtained.

[0191] The other layers in the solar cell and the preparation steps are the same as those of Example 1 and will not be repeated.

[0192] Comparative Example 2

[0193] The P(6FDA-DABA) powder of Comparative Example 2 was prepared by replacing the composite material of Example 1 with P(6FDA-DABA) powder, and the preparation steps of the P(6FDA-DABA) powder of Comparative Example 2 were as follows:

[0194] In a two-necked round-bottom flask, 2.22 g of 6FDA, 0.76 g of DABA, and 0.27 g of m-cresol were added under an inert atmosphere (N2), and then heated to 200°C for a period of time to complete the reaction. Then, the reaction system was cooled, poured into 10 mL of methanol, and P(6FDA-DABA) powder containing impurities was obtained. The P(6FDA-DABA) powder containing impurities was reprecipitated from THF to remove residual impurities, and then the powder after removing impurities was dried in a vacuum drying oven at 120°C for 24 h to obtain purified P(6FDA-DABA) powder.

[0195] The solar cell of Comparative Example 2 was similar to that of Example 1, except that the material of the medium layer in the solar cell of Comparative Example 2 was P(6FDA-DABA), and the preparation steps of the medium layer were as follows:

[0196] The above P(6FDA-DABA) powder was dissolved in CH3CH2OH, coated on the perovskite layer by spin coating, and then annealed in an annealing furnace at 130°C for 15 min to obtain a medium layer with a thickness of 20 nm.

[0197] The other layers in the solar cell and the preparation steps were the same as those of Example 1 and will not be described again.

[0198] Comparative Example 3

[0199] Comparative Example 3 did not contain a composite material.

[0200] The solar cell of Comparative Example 3 did not contain a medium layer, and included a transparent conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer, a positive electrode, and a negative electrode. The hole transport layer, the perovskite layer, and the electron transport layer were sequentially stacked on the surface of the transparent conductive substrate, the positive electrode formed ohmic contact with the transparent conductive substrate, and the negative electrode formed ohmic contact with the electron transport layer.

[0201] The preparation steps of the solar cell were as follows:

[0202] (1) ITO was deposited by a PVD device using a magnetron sputtering method to obtain a transparent conductive substrate with a thickness of 900 nm.

[0203] (2) Cu2O was deposited on the surface of the transparent conductive substrate by a PVD device using an evaporation method to obtain a hole transport layer with a thickness of 18 nm.

[0204] (3) Using a coater to form MAPbI3 on the surface of the hole transport layer, to obtain a perovskite layer with a thickness of 1100 nm.

[0205] (4) Using an RPD device to deposit SnO2 on the surface of the perovskite layer, to obtain an electron transport layer material with a thickness of 30 nm.

[0206] (5) Using an evaporation instrument to evaporate a negative electrode on the surface of the electron transport layer and a positive electrode on the surface of the transparent conductive substrate, to obtain a solar cell. The thickness of the positive electrode is 260 nm, and the thickness of the negative electrode is 260 nm.

[0207] The following is the performance test part:

[0208] 1. Open-circuit voltage, short-circuit current density, fill factor test:

[0209] An I-V tester (model: IVS-KA6000, manufacturer: Shengyan Electronic Technology (Shanghai) Co., Ltd.) was used to measure the current (I)-voltage (V) of the solar cells of each example and the comparative example, to obtain the open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) of the solar cells.

[0210] 2. Photoelectric conversion efficiency test:

[0211] An I-V tester (model: IVS-KA6000, manufacturer: Shengyan Electronic Technology (Shanghai) Co., Ltd.) was used to measure the current (I)-voltage (V) of the solar cells of each example and the comparative example, to obtain the photoelectric conversion efficiency (Eta) of the solar cells.

[0212] 3. Electron mobility test:

[0213] A carrier transient characteristic analyzer (model: PTC-TPV, manufacturer: Jilv Technology Co., Ltd.) was used to test the electron mobility of the solar cells of each example and the comparative example.

[0214] 4. Specific surface area and pore volume test:

[0215] An N2-adsorption-desorption instrument (model: ASAP2020, manufacturer: Micromeritics (Shanghai) Instrument Co., Ltd.) was used to test the specific surface area and pore volume of the composite material of each example, MIL-101 and P(6FDA-DABA) of the comparative example.

[0216] The Voc, FF, Jsc, PCE and electron mobility test results of the solar cells of each example and the comparative example are shown in Table 1 below:

[0217] Table 1

[0218]

[0219] The specific surface area and pore volume test results of the composite materials of the above examples, MIL-101 of the comparative examples and P(6FDA-DABA) are shown in Table 2:

[0220] Table 2

[0221]

[0222] As can be seen from the comparison of Examples 1-6 and Comparative Example 3, compared with Comparative Example 3, the conversion efficiency and electron mobility of the perovskite solar cell are obviously improved, the open circuit voltage, short circuit current density and fill factor and other performances are improved or close to, and the water contact angle is obviously increased after some embodiments of the application prepare the medium layer of MIL-101 / P(6FDA-DABA) composite material on the perovskite layer of the perovskite solar cell. It shows that the preparation method of some embodiments of the application can solve the problem of high interface defect density of the perovskite solar cell, improve the electron mobility, and also improve the stability of the perovskite solar cell, and improve the photoelectric conversion efficiency, while keeping other performances unchanged or improved.

[0223] As can be seen from the comparison of Examples 1-6 and Comparative Examples 1-2, compared with Comparative Examples 1 and 2, the Eta and electron mobility of the solar cell are obviously improved after some embodiments of the application prepare MIL-101 / P(6FDA-DABA) composite material on the perovskite layer of the perovskite solar cell. In addition, although the open circuit voltage, short circuit current density and other performances of Comparative Example 1 are improved compared with Comparative Example 2, the carrier mobility and fill factor performance are not obviously improved, indicating that only preparing MIL-101 medium layer on the perovskite layer of the perovskite solar cell has limited performance improvement of the perovskite solar cell; although the open circuit voltage, fill factor and other performances of Comparative Example 2 are improved compared with Comparative Example 3, the short circuit current and electron mobility are not obviously improved, indicating that only preparing P(6FDA-DABA) medium layer on the perovskite layer of the perovskite solar cell also has limited performance improvement of the perovskite solar cell.

[0224] As can be seen from Examples 1-5, with the increase of the mass percentage of P(6FDA-DABA) introduced into MIL-101, the specific surface area and pore volume of the composite material show a decreasing trend, and the electrical properties and electron mobility of the perovskite solar cell also decrease, which is due to P(6FDA-DABA) causing partial plugging of MIL-101, indicating that optimizing the introduction amount of P(6FDA-DABA) is beneficial to further improve the carrier mobility and photoelectric conversion efficiency of the solar cell.

[0225] Therefore, the MIL-101 / P(6FDA-DABA) composite material prepared in some embodiments of this application has superhydrophobic properties, as well as a very large specific surface area and excellent porosity. When this composite material is prepared on top of the perovskite layer of a perovskite solar cell, it effectively solves the problems of high interface defect density and low electron mobility. Furthermore, this material can enhance the free energy of perovskite film crystallization, promote the nucleation and crystallization of the perovskite layer, and improve the stability of the perovskite material to a certain extent, thereby significantly improving the photoelectric conversion efficiency of the perovskite solar cell.

[0226] 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.

[0227] 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 composite material, characterized in that, The invention includes a metal-organic framework and a polyimide coordinated to the metal-organic framework, wherein the raw materials for preparing the polyimide include an aromatic dianhydride and an aromatic diamine, and at least one of the aromatic dianhydride and the aromatic diamine contains a fluorine group and a carboxyl group.

2. The composite material according to claim 1, characterized in that, One or more of the following conditions must be met: (1) The raw materials for preparing the polyimide include hexafluoroisopropenylated anhydride and 3,5-diaminobenzoic acid; Optionally, the molar ratio of the hexafluoroisopropenylic anhydride and the 3,5-diaminobenzoic acid is (1~8):1; (2) The number average molecular weight of the polyimide is 40,000 g / mol to 50,000 g / mol; (3) The metal-organic framework includes one or more of MIL-101, HKUST-1 and IRMof-1; Optionally, the metal-organic framework includes one or both of MIL-101(Cr) and MIL-101(Fe); (4) In the composite material, the polyimide has a mass percentage of 1% to 5%; Optionally, in the composite material, the polyimide has a mass percentage of 2% to 4%; (5) The specific surface area of ​​the composite material is 3200 m². 2 / g~4200m 2 / g; Optionally, the specific surface area of ​​the composite material is 3600m². 2 / g~4000m 2 / g; (6) The pore volume of the composite material is 1.6 cm. 3 / g~1.9cm 3 / g; Optionally, the pore volume of the composite material is 1.7cm³. 3 / g~1.85cm 3 / g.

3. A method for preparing a composite material, characterized in that, Includes the following steps: A polyimide is obtained, wherein the raw materials for preparing the polyimide include an aromatic dianhydride and an aromatic diamine, wherein at least one of the aromatic dianhydride and the aromatic diamine contains a fluorine group and a carboxyl group; The polyimide and the metal-organic framework are linked by coordination bonds to prepare a composite material.

4. The method for preparing the composite material according to claim 3, characterized in that, The step of linking the polyimide and the metal-organic framework via coordination bonds includes: The polyimide was mixed with a metal-organic framework precursor solution and subjected to a hydrothermal reaction at 160°C to 180°C for 18 to 24 hours. The metal-organic framework includes MIL-101, and the metal-organic framework precursor solution includes: a water-soluble metal salt, sodium hydroxide, terephthalic acid and water, wherein the water-soluble metal salt includes one or more of water-soluble chromium salt and water-soluble iron salt. Optionally, the metal-organic framework precursor solution comprises a water-soluble metal salt, sodium hydroxide, terephthalic acid, and water in a molar ratio of 1:(0.5~2):(0.5~2):(278~300).

5. The application of the composite material as described in any one of claims 1 to 2 or the composite material prepared by the preparation method as described in any one of claims 3 to 4 in the preparation of solar cells.

6. A solar cell, characterized in that, It includes a perovskite layer, a dielectric layer, and an electron transport layer, wherein the dielectric layer is disposed between the perovskite layer and the electron transport layer; The material of the medium layer is the composite material according to any one of claims 1 to 2 or the composite material prepared by the preparation method according to any one of claims 3 to 4.

7. The solar cell according to claim 6, characterized in that, One or more of the following conditions must be met: (1) The thickness of the dielectric layer is 10 nm to 30 nm; (2) The thickness of the electron transport layer is 20nm~40nm; (3) The material of the electron transport layer includes one or both of TiO2 and SnO2; (4) The thickness of the perovskite layer is 1000 nm to 1200 nm; (5) The material of the perovskite layer includes one or more of MAPbI3, MAPbCl3 and MAPbBr3; (6) The solar cell further includes a transparent conductive substrate, a hole transport layer, a positive electrode and a negative electrode. The hole transport layer, the perovskite layer, the dielectric layer and the electron transport layer are sequentially stacked on the surface of the transparent conductive substrate. The positive electrode forms an ohmic contact with the transparent conductive substrate and the negative electrode forms an ohmic contact with the electron transport layer. Optionally, the material of the hole transport layer includes NiO. x and one or two of Cu2O; Optionally, the thickness of the hole transport layer is 15nm~20nm; Optionally, the thickness of the positive electrode and the negative electrode are each independently 200nm~300nm.

8. A method for preparing a solar cell, characterized in that, Includes the following steps: A dielectric layer is formed between the perovskite layer and the electron transport layer to fabricate a solar cell; The material of the medium layer is the composite material according to any one of claims 1 to 2 or the composite material prepared by the preparation method according to any one of claims 3 to 4.

9. The method for preparing a solar cell according to claim 8, characterized in that, The steps for forming a dielectric layer between the perovskite layer and the electron transport layer include: A solution containing the composite material is applied to the surface of the perovskite layer, and then annealed to prepare the dielectric layer. The annealing temperature is 100℃~150℃, and the annealing time is 8min~20min; Optionally, the solvent in the solution containing the composite material includes one or more of N,N-dimethylformamide, dichloromethane, and anhydrous ethanol; and / or, The solution containing the composite material was applied to the surface of the perovskite layer by spin coating at a spin speed of 4000 rpm to 6000 rpm and a spin coating time of 15 s to 30 s.

10. A photovoltaic module, characterized in that, The solar cell includes a packaging structure and the solar cell as described in any one of claims 6 to 7 or the solar cell prepared by the preparation method described in any one of claims 8 to 9, wherein the solar cell is packaged by the packaging structure.

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