Double-perovskite thin film material, preparation method thereof and double-perovskite solar cell

Abstract

The invention discloses a double-perovskite thin film material, a preparation method thereof and a double-perovskite solar cell, and relates to the technical field of perovskite materials. The double perovskite thin film material comprises A2BCX6 type double perovskite, A is an alkali metal cation, B is a monovalent metal cation, C is a trivalent metal cation, and X is a halogen anion; the additive is a compound comprising a benzene ring and at least two sulfydryl substituted at different positions of the benzene ring. According to the embodiment, the composite center of the interior and interface of the double-perovskite thin film material can be reduced, the nucleation density in the preparation process of the double-perovskite thin film is reduced, the double-perovskite film layer has high crystallinity and larger grain size, the grain boundary in the film layer is reduced, the grain boundary defect is passivated, and the performance of the double-perovskite thin film is improved. And the photoelectric conversion efficiency of the solar cell containing the double perovskite thin film material can be improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a double perovskite thin film material and its preparation method, and a double perovskite solar cell. Background Technology

[0002] Lead-free halide double perovskites are emerging as promising perovskite materials due to their high stability, low lead toxicity, and high carrier migration efficiency. However, the small grain size and high nucleation density of lead-free halide double perovskites lead to dense grain boundaries. The high surface energy drives the formation of interface defects, resulting in numerous grain boundaries and defects. This leads to poor film quality and crystallinity during the preparation of perovskite films, resulting in higher nonradiative recombination and interfacial resistance, which reduces carrier transport and collection efficiency. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a double perovskite thin film material and its preparation method, as well as a double perovskite solar cell, which can reduce the recombination centers inside and at the interface of the double perovskite thin film material, reduce the nucleation density during the preparation process of the double perovskite thin film, and enable the subsequently formed double perovskite film layer to have high crystallinity and larger grain size.

[0004] To achieve the above objectives, according to one aspect of the present invention, a dual perovskite thin film material is provided, comprising: A2BCX6 type double perovskite, wherein A is an alkali metal cation, B is a monovalent metal cation, C is a trivalent metal cation, and X is a halide anion; Additives are compounds comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring.

[0005] Optionally, the molar ratio of the element corresponding to B in the double perovskite to the additive is 150:(0.5-6).

[0006] Optionally, the benzene ring in the additive has two thiol groups at the para-position.

[0007] Optionally, the additive includes at least one of 1,4-dimercaptobenzene, 2,5-dimercaptoterephthalic acid, benzene hexathiophenol, 2,5-diamino-1,4-benzenedithiophenol dihydrochloride, and 1,4-benzenedimethylthiol.

[0008] Optionally, the alkali metal cation includes one or more of sodium ions, potassium ions, rubidium ions, and cesium ions; And / or, The monovalent metal cation includes one or more of monovalent copper ions, monovalent silver ions, and monovalent gold ions; And / or, The trivalent metal cations include one or more of trivalent bismuth ions, trivalent antimony ions, and trivalent indium ions.

[0009] According to another aspect of the present invention, a method for preparing a double perovskite thin film material is provided, which is used to prepare the double perovskite thin film material of the present invention, comprising: Organic solvents and precursor materials for preparing double perovskites are mixed with additives to prepare a double perovskite precursor solution. The above-mentioned double perovskite precursor solution is coated on the substrate surface and then annealed to form the double perovskite thin film material on the substrate surface.

[0010] Optionally, the precursor materials for the double perovskite include AX, BX, and CX3; And / or, The organic solvent includes dimethyl sulfoxide and / or N,N-dimethylformamide; And / or, The annealing conditions include: an inert gas atmosphere, an annealing temperature of 250℃~300℃, and an annealing time of 5min~20min.

[0011] Optionally, when using AX, BX, and CX3 as precursor materials for preparing the double perovskite, the molar ratio of AX:BX:CX3 is 2:1:1, and the concentration of BX in the double perovskite precursor solution is 0.1 mol / L to 0.8 mol / L.

[0012] According to another aspect of the present invention, a double perovskite solar cell is provided, comprising a substrate, and a first carrier transport layer, a double perovskite film layer and a second carrier transport layer sequentially stacked on the surface of the substrate, wherein the material of the double perovskite film layer is the double perovskite thin film material of the present invention.

[0013] Optionally, the thickness of the double perovskite film is 200 nm to 300 nm.

[0014] One embodiment of the above invention has the following advantages or beneficial effects: it includes an A2BCX6 type double perovskite and an additive, wherein A is an alkali metal cation, B is a monovalent metal cation, C is a trivalent metal cation, and X is a halide anion; the additive is a compound comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring. The sulfur atom of the thiol group in the additive can simultaneously coordinate with B and C, and the hydrogen atom of the thiol group can form a hydrogen bond with X, which can inhibit the migration of metal ions and passivate vacancy defects, inhibiting the nucleation process, thereby reducing the recombination centers inside and at the interface of the double perovskite thin film material, reducing the nucleation density during the preparation of the double perovskite thin film, making the double perovskite film layer have high crystallinity and larger grain size, reducing grain boundaries in the film layer, passivating grain boundary defects, enhancing the applicability of the double perovskite thin film material, and helping to improve the photoelectric conversion efficiency of solar cells containing the above-mentioned double perovskite thin film material.

[0015] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0016] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein: Figure 1 This is a schematic flowchart of a method for preparing a double perovskite thin film material according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a double perovskite solar cell according to an embodiment of the present invention; Figure 3 This is a schematic flowchart of a method for fabricating a double perovskite solar cell according to an embodiment of the present invention; Figure 4(a) is a scanning electron microscope image of the double perovskite solar cell M1 according to Embodiment 1 of the present invention; Figure 4(b) is a scanning electron microscope image of the double perovskite solar cell M2 according to Embodiment 2 of the present invention; Figure 4(c) is a scanning electron microscope image of the double perovskite solar cell M8 according to Comparative Example 1 of the present invention; Figure 5 These are the X-ray diffraction patterns of the double perovskite solar cells M1, M2, and M8; Figure 6 This is a JV curve diagram of dual perovskite solar cells M1~M9 according to an embodiment of the present invention.

[0017] Figure label: 1-Substrate; 11-Base; 12-First carrier transport layer; 2-Double perovskite film layer; 3-Second carrier transport layer; 4-Electrode layer. Detailed Implementation

[0018] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0019] It should be noted that the outer side of the functional film layer involved in the embodiments of the present invention refers to the side away from the substrate.

[0020] It should be noted that, unless otherwise specified, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0021] The double perovskite thin film material of this invention mainly comprises: A2BCX6 type double perovskite and additives. Wherein, A is an alkali metal cation; B is a monovalent metal cation; C is a trivalent metal cation; and X is a halide anion.

[0022] The aforementioned additive is a compound comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring. The benzene ring may include two, three, four, or six thiol groups, etc. As an example, when the benzene ring includes two thiol groups, the two thiol groups can be distributed on the benzene ring at para, ortho, or meta positions; when the benzene ring includes three or four thiol groups, any two thiol groups can be distributed alternately or adjacently on the benzene ring.

[0023] In this process, the sulfur atom in the thiol group can coordinate with both B and C, while the hydrogen atom in the thiol group can form hydrogen bonds with X. This inhibits the migration of metal ions, passivates vacancy defects, and suppresses the nucleation process, thereby reducing the number of recombination centers inside and at the interface of the double perovskite thin film material. This lowers the nucleation density during the preparation of the double perovskite thin film, resulting in larger grain sizes and lower grain boundary density. Larger grain sizes reduce grain boundaries in the film layer, and the aforementioned coordination and hydrogen bond formation passivate grain boundary defects, thus reducing structural defects in the double perovskite film layer containing the double perovskite material. This helps suppress carrier recombination losses at grain boundaries, promotes carrier transport and separation, and lowers the carrier transport barrier.

[0024] In one optional embodiment, the alkali metal cation includes one or more of sodium ions, potassium ions, rubidium ions, and cesium ions; the monovalent metal cation includes one or more of monovalent copper ions, monovalent silver ions, and monovalent gold ions; the trivalent metal cation includes one or more of trivalent bismuth ions, trivalent antimony ions, and trivalent indium ions; and the halide anion includes one or more of fluoride ions, chloride ions, bromide ions, and iodide ions.

[0025] Preferably, A2BCX6 can be Cs2AgBiBr6. Compared with traditional lead-based halide perovskites, Cs2AgBiBr6 has a long radiative recombination lifetime, long charge diffusion length, high defect tolerance and excellent environmental stability, making it particularly suitable for optoelectronic devices that are sensitive to stability and toxicity.

[0026] In an optional embodiment, the molar ratio of the element corresponding to B in the double perovskite to the above-mentioned additive is 150:(0.5-6).

[0027] As an example, the molar ratio of element B to additive in double perovskites is 150:0.5, 150:1, 150:3, 150:5, or 150:6, etc.

[0028] By adjusting the molar ratio of the element corresponding to B in the double perovskite to the additives, the content of double perovskite and additives in the double perovskite thin film material can be precisely controlled. This avoids the generation of impurities when forming the double perovskite film layer using the double perovskite thin film material. At the same time, it can also avoid excessively small grain size and increased grain boundary defects during the crystallization process, ensuring the formation of uniform, large-sized grains during the crystallization process and reducing grain boundaries and grain boundary defects.

[0029] In an optional embodiment, the additive includes at least one selected from 1,4-dimercaptobenzene, 2,5-dimercaptoterephthalic acid, benzene hexathiophenol, 2,5-diamino-1,4-benzenedithiophenol dihydrochloride, and 1,4-benzenedimethylthiol.

[0030] The aforementioned 1,4-dimercaptobenzene, 2,5-dimercaptoterephthalic acid, benzene hexathiophenol, 2,5-diamino-1,4-benzenedithiophenol dihydrochloride, or 1,4-benzenedimethylthiol contain phenyl groups and are all solid at room temperature. In the preparation of double perovskite thin film materials and double perovskite film layers, they can be used as bulk passivating agents to improve their performance from beginning to end. This avoids the problem of using substances that are liquid at room temperature as bulk passivating agents, which volatilize during the preparation process, leading to a decrease in content and failure to achieve bulk passivation.

[0031] In an optional embodiment, the benzene ring in the above-mentioned additive has two thiol groups at the para-position. The phenyl group and the two thiol groups at the para-position can reduce the intermolecular distance of the perovskite double film, making the perovskite double film more compact and improving its crystallinity. In this case, the above compound may include p-dimercaptobenzene and / or derivatives of p-dimercaptobenzene.

[0032] The para-thiol group coordinates with both B and C in adjacent perovskite molecules, further reducing the spacing between perovskite molecules. Furthermore, the coordinated structure tends towards a flat configuration, avoiding additional steric hindrance and reducing the fill factor of the perovskite solar cell. Through the synergistic bonding of the para-thiol group with B and C in adjacent perovskite octahedra and the X at the octahedron top, ion migration can be significantly suppressed, improving the optical, thermal, and humidity stability of the perovskite thin film material and expanding its application scenarios. This perovskite thin film material can be used to form perovskite films with larger grain sizes and higher crystallinity, improving the photoelectric conversion efficiency and stability of perovskite solar cells containing such films.

[0033] The double perovskite thin film material according to embodiments of the present invention includes an A2BCX6 type double perovskite and an additive, wherein A is an alkali metal cation, B is a monovalent metal cation, C is a trivalent metal cation, and X is a halide anion; the additive is a compound comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring. The sulfur atom of the thiol group in the additive can simultaneously coordinate with B and C, and the hydrogen atom of the thiol group can form a hydrogen bond with X, which can inhibit the migration of metal ions, passivate vacancy defects, and suppress the nucleation process, thereby reducing the number of recombination centers inside and at the interface of the double perovskite thin film material, lowering the nucleation density during the preparation of the double perovskite thin film, giving the double perovskite film layer high crystallinity and larger grain size, reducing grain boundaries in the film layer, passivating grain boundary defects, and helping to improve the photoelectric conversion efficiency of solar cells containing the above-mentioned double perovskite thin film material.

[0034] like Figure 1 As shown, this embodiment of the invention provides a method for preparing a double perovskite thin film material, which includes the following steps A1 to A2: Step A1: Mix the organic solvent and the precursor raw material for preparing double perovskite with the additives to prepare a double perovskite precursor solution; Step A2: The above-mentioned double perovskite precursor solution is coated on the substrate surface, and after annealing, the above-mentioned double perovskite thin film material is formed on the substrate surface.

[0035] The additives can be compounds comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring. These can act as bulk passivating agents to regulate the nucleation and crystallization processes of double perovskite films, providing thiol and phenyl groups. The phenyl groups and at least two thiol groups can reduce the intermolecular distance of the double perovskite film, resulting in a denser double perovskite film and improved crystallinity. All the above-mentioned additives are solid at room temperature. As bulk passivating agents, they can improve the performance of the double perovskite film material from beginning to end, avoiding the problem of using liquid substances at room temperature, which volatilize during preparation, leading to a decrease in content and failure to achieve bulk passivation.

[0036] Preferably, the benzene ring in the additive has two thiol groups at the para-position. These para-thiol groups simultaneously coordinate with the B and C groups in adjacent perovskite molecules. This not only further reduces the spacing between perovskite molecules but also, because the coordinated structure tends towards a flat configuration, avoids additional steric hindrance and prevents a decrease in the fill factor of perovskite solar cells using the aforementioned perovskite thin film material. Through the synergistic bonding of the para-thiol groups with the B and C groups in adjacent perovskite octahedra and the X group at the octahedron top, ion migration can be significantly suppressed, improving the optical, thermal, and humidity stability of the perovskite thin film material, expanding its application scenarios, and giving the perovskite film containing the aforementioned material larger grain size and higher crystallinity, thus enhancing the applicability of the perovskite film.

[0037] In one alternative embodiment, the precursor raw materials of the double perovskite include AX, BX, and CX3.

[0038] Preferably, AX can be CsBr; BX can be AgBr; and CX3 can be BiBr3.

[0039] By mixing precursor raw materials with additives and organic solvents, a double perovskite precursor solution is prepared. The sulfur atoms in the thiol groups of the additives can simultaneously coordinate with both B and C, and the hydrogen atoms in the thiol groups can form hydrogen bonds with X. This inhibits the migration of metal ions, passivates vacancy defects, and suppresses the nucleation process. Therefore, using this double perovskite precursor solution to prepare double perovskite thin film materials reduces recombination centers within the double perovskite thin film material and at the interface, lowering the nucleation density during the preparation process. This results in larger double perovskite grains and a lower grain boundary density. Larger grains reduce grain boundaries in the double perovskite thin film material, and the coordination and hydrogen bond formation passivate grain boundary defects, thereby reducing structural defects. This allows the double perovskite film layer to suppress carrier recombination losses at grain boundaries, promote carrier transport and separation, and lower the carrier transport barrier.

[0040] In one optional embodiment, the organic solvents mentioned above include dimethyl sulfoxide and N,N-dimethylformamide, which can effectively dissolve precursor raw materials and additives.

[0041] In an optional embodiment, when using AX, BX, and CX3 as precursor materials for preparing the double perovskite, step A1 above may include: placing AX, BX, CX3, and additives in the aforementioned organic solvent, stirring until completely dissolved, at a stirring temperature of 80℃~120℃, and for a stirring time of 1h~4h, to prepare a double perovskite precursor solution. As an example, the stirring temperature may be 80℃, 90℃, 95℃, 100℃, 110℃, or 120℃, etc.; the stirring time may be 1h, 1.8h, 2.5h, 3h, or 4h, etc.

[0042] The molar ratio of AX:BX:CX3 can be 2:1:1; the concentration of BX in the above-mentioned double perovskite precursor solution is 0.1 mol / L to 0.8 mol / L. For example, the concentration of BX in the double perovskite precursor solution can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, or 0.8 mol / L, etc.

[0043] By setting the stirring conditions within an appropriate range, a more uniform and stable solution can be obtained. Furthermore, by setting the molar concentrations of various substances in the double perovskite precursor solution within an appropriate range, the content of each substance can be precisely controlled, avoiding impurities during the preparation of double perovskite thin film materials. This also prevents excessively small grain sizes and increased grain boundary defects during crystallization, ensuring the formation of uniform, large-sized grains and reducing grain boundaries and defects.

[0044] In one optional embodiment, the coating method of the double perovskite precursor solution includes, but is not limited to, spin coating, blade coating, etc.

[0045] When the double perovskite precursor solution is coated by spin coating, the spin coating speed is 2000 rpm to 5000 rpm, and the spin coating time is 30 s to 50 s. As an example, the spin coating speed can be 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, or 5000 rpm, etc.; the spin coating time can be 30 s, 34 s, 38 s, 40 s, 45 s, or 50 s, etc.

[0046] By controlling the spin coating time and spin coating speed within a suitable range, the spreading uniformity of the double perovskite precursor solution can be improved, and the thickness of the double perovskite thin film material formed on the substrate surface can be adjusted.

[0047] In one optional embodiment, the annealing conditions in step A2 include: an inert gas atmosphere, an annealing temperature of 250°C to 300°C, and an annealing time of 5 min to 20 min. As examples, the annealing temperature can be 250°C, 260°C, 270°C, 275°C, 285°C, or 300°C, etc.; the annealing time can be 5 min, 7 min, 10 min, 13 min, 15 min, 18 min, or 20 min, etc.

[0048] Inert gas atmospheres include nitrogen atmospheres, argon atmospheres, etc.

[0049] Annealing removes residual solvents, drives the crystallization process, and orders the crystal structure. By controlling the annealing conditions, the crystallization rate and defect control can be balanced, resulting in a double perovskite thin film material with high crystallinity and low defect density formed on the substrate surface.

[0050] In one alternative embodiment, the substrate includes a base and a first carrier transport layer formed on a main surface of the base. The double perovskite thin film material is coated on the outside of the first carrier transport layer, thereby forming a double perovskite thin film material on the outside of the first carrier transport layer.

[0051] According to an embodiment of the present invention, a method for preparing a double perovskite thin film material involves mixing an organic solvent and a precursor raw material for preparing the double perovskite with additives to prepare a double perovskite precursor solution. This solution is then coated onto a substrate surface, followed by annealing to form a double perovskite thin film material on the substrate surface. The additives act as bulk passivating agents to regulate the nucleation and crystallization processes of the double perovskite film. The sulfur atom in the thiol group can simultaneously coordinate with both B and C, and the hydrogen atom in the thiol group can form hydrogen bonds with X, inhibiting the migration of metal ions and passivating vacancy defects. This suppresses the nucleation process, reduces the nucleation density during the preparation of the double perovskite thin film, increases the size of the double perovskite grains, reduces the grain boundary density, and yields a double perovskite thin film material with larger grain size and higher crystallinity. This reduces the number of recombination centers within and at the interfaces of the double perovskite thin film material. Large grain size reduces grain boundaries and passivates grain boundary defects through coordination and hydrogen bonding, thereby reducing structural defects in the double perovskite thin film material. This allows the double perovskite film containing the above-mentioned double perovskite thin film material to suppress carrier recombination loss at grain boundaries, promote carrier transport and separation, and reduce the carrier transport barrier.

[0052] like Figure 2As shown, the dual perovskite solar cell of this embodiment may include: a substrate, and a first carrier transport layer 12, a dual perovskite film layer 2 and a second carrier transport layer 3 sequentially stacked on the surface of the substrate 11; wherein, the material of the dual perovskite film layer 2 is the dual perovskite thin film material of this embodiment.

[0053] The double perovskite film layer 2 in the double perovskite solar cell is used to absorb sunlight and generate photogenerated carriers. The double perovskite film layer 2 of the double perovskite thin film material used in this embodiment of the invention has a larger grain size, higher crystallinity, and reduced grain boundaries and grain boundary defects. Therefore, the aforementioned double perovskite solar cell exhibits higher photoelectric conversion efficiency due to the use of the aforementioned double perovskite film layer 2.

[0054] The substrate 11 can serve as a physical support for the entire double perovskite solar cell, thus maintaining the stability of the cell structure.

[0055] The first carrier transport layer 12 is used to absorb first carriers from the double perovskite film layer 2 and transport the first carriers to the substrate 11, while simultaneously blocking the diffusion of second carriers to the substrate 11. The first and second carriers have opposite conductivity types; that is, when the first carrier is an electron, the second carrier is a hole; and when the first carrier is a hole, the second carrier is an electron.

[0056] The substrate 11 may include one of the following: indium tin oxide conductive glass, fluorine-doped tin oxide conductive glass, aluminum-doped zinc oxide conductive glass, graphite-based conductive glass, and crystalline silicon solar cell.

[0057] Indium tin oxide (ITO) conductive glass, fluorine-doped tin oxide (FTO) conductive glass, and aluminum-doped zinc oxide (ANO) conductive glass are all formed by depositing a transparent conductive film on the surface of a common glass substrate. For example, ITO conductive glass is formed by depositing an ITO transparent conductive film on the surface of a common glass substrate; FTO conductive glass is formed by depositing a FTO transparent conductive film on the surface of a common glass substrate; and ANO conductive glass is formed by depositing an ANO transparent conductive film on the surface of a common glass substrate.

[0058] The substrate 1 includes the aforementioned substrate 11 and a first carrier transport layer 12 disposed on the surface of the aforementioned substrate 11.

[0059] The second carrier transport layer 3 is used to collect second carriers from the double perovskite film layer 2.

[0060] In an optional embodiment, the aforementioned dual perovskite solar cell further includes an electrode layer 4 formed outside the second carrier transport layer 3. The electrode layer 4 serves as a top electrode, collecting the second carriers.

[0061] The second carrier transport layer 3 can transport the collected second carriers to the electrode layer 4 and prevent the first carriers from diffusing into the electrode layer 4. At the same time, when the electrode layer 4 contains metal, the second carrier transport layer 3 can also prevent metal ions in the electrode layer 4 from diffusing into the double perovskite film layer and causing it to degrade.

[0062] Depending on the substrate 11, the material and structure of the electrode layer 4 can be different. For example, when the substrate 11 is a conductive metal grid electrode glass, the electrode layer 4 can include metal materials such as gold and silver, and cover the entire second carrier transport layer 3. When the substrate 11 is a crystalline silicon cell, the electrode material of the electrode layer 4 can include transparent conductive oxides and metals.

[0063] In one optional embodiment, the thickness of the aforementioned double perovskite film 2 can be 200 nm to 300 nm. As an example, the thickness of the double perovskite film 2 can be 200 nm, 220 nm, 250 nm, 270 nm, or 300 nm, etc.

[0064] By adjusting the thickness of the double perovskite film layer 2, the light absorption and carrier recombination can be balanced. An appropriate thickness can increase the absorbed photons while avoiding the aggravation of carrier recombination.

[0065] According to an embodiment of the present invention, the double perovskite solar cell uses a double perovskite thin film material as the material of the double perovskite film layer 2. The double perovskite film layer 2 has high crystallinity and larger grain size. The grain boundaries in the film layer are reduced, and the grain boundary defects are passivated. This can reduce the recombination loss of charge carriers at the grain boundaries, promote the separation and transport of charge carriers, and improve the photoelectric conversion efficiency of the double perovskite solar cell.

[0066] like Figure 3 As shown, the method for fabricating a dual perovskite solar cell according to an embodiment of the present invention includes: Step B1: Using the preparation method of the double perovskite thin film material of the present invention, a double perovskite thin film material is formed on one main surface of the substrate, so as to use the above-mentioned double perovskite thin film material as the material of the double perovskite film layer, and a double perovskite film layer is obtained. The substrate includes a base and a first carrier transport layer disposed on a main surface of the base.

[0067] The first carrier transport layer and the double perovskite film layer are located on the same side of the substrate, that is, the double perovskite film layer is located outside the first carrier transport layer.

[0068] Optionally, the substrate can be preheated before forming the double perovskite film to promote the uniform spreading and wetting of the double perovskite precursor solution on the substrate surface. Specifically, the preheating temperature can be 70°C to 90°C. As an example, the preheating temperature of the substrate before forming the double perovskite film can be 70°C, 75°C, 77.5°C, 80°C, 85°C, or 90°C, etc.

[0069] Step B2: A second carrier transport layer is formed on the outside of the above-mentioned double perovskite film layer.

[0070] In an optional embodiment, step B2 above further includes forming an electrode layer outside the second carrier transport layer.

[0071] In an optional embodiment, the above-mentioned method for fabricating a double perovskite solar cell further includes: pre-treating the substrate.

[0072] When the substrate is conductive glass, the pretreatment of the substrate may specifically include: ultrasonically cleaning the conductive glass sequentially with glass cleaner, deionized water and ethanol for 10-20 minutes, drying it with a nitrogen gun, and treating it under ultraviolet-ozone conditions for 15-30 minutes.

[0073] By pre-treating the conductive glass, impurities and dirt on the surface of the conductive glass are removed to keep its surface clean and avoid affecting the subsequent preparation of the first carrier transport layer due to surface impurities or dirt.

[0074] When the substrate is a crystalline silicon solar cell, the pretreatment of the substrate may specifically include: cleaning the silicon substrate to remove impurities from the surface, then texturing the silicon substrate to improve the light absorption efficiency of the crystalline silicon solar cell; doping the texturized silicon substrate to form an emitter on one of the main surfaces of the silicon substrate, enabling the crystalline silicon solar cell to separate photogenerated carriers; forming a passivation layer on the side of the emitter away from the silicon substrate, and forming a passivation layer and a doped polycrystalline silicon layer on the main surface of the silicon substrate where the emitter is not located, to reduce carrier recombination, thereby obtaining a crystalline silicon solar cell that can be used as a substrate. The conductivity type of the silicon substrate includes N-type and P-type; the conductivity type of the doped polycrystalline silicon layer is the same as that of the silicon substrate.

[0075] In an optional embodiment, the above-mentioned method for fabricating a double perovskite solar cell further includes: step B0, forming a first carrier transport layer on a main surface of a substrate to obtain a substrate.

[0076] Optionally, when the substrate 11 is conductive glass, the first carrier transport layer 12 is an electron transport layer, the first carrier is an electron, and the second carrier transport layer 3 is a hole transport layer, the second carrier is a hole; when the substrate 11 is a crystalline silicon cell, the first carrier transport layer 12 is a hole transport layer, the first carrier is a hole, and the second carrier transport layer 3 is an electron transport layer, the second carrier is an electron.

[0077] Specifically, the formation of the electron transport layer may include: coating a pre-prepared tin oxide precursor solution, and annealing the coated tin oxide precursor solution to form the electron transport layer. Wherein, if the substrate 11 is conductive glass, the pre-prepared tin oxide precursor solution is coated onto the surface of the substrate 11; if the substrate 11 is a crystalline silicon solar cell, the pre-prepared tin oxide precursor solution is coated onto the surface of the double perovskite film layer 2.

[0078] The tin oxide precursor solution is prepared using a tin oxide dispersion and water, wherein the volume ratio of the tin oxide dispersion to water can be 1:(3~6). As an example, when preparing the tin oxide precursor solution, the volume ratio of the tin oxide dispersion to water can be 1:3, 1:4, 1:5, or 1:6, etc.

[0079] Optionally, the tin oxide dispersion can be a commercially available product for preparing electron transport layers, or it can be prepared in-house. The tin oxide dispersion typically uses water as a solvent, and the mass percentage of tin oxide nanoparticles is 10% to 20%. As an example, in the tin oxide dispersion used to prepare the tin oxide precursor solution, the mass percentage of tin oxide nanoparticles can be 10%, 12%, 15%, 18%, or 20%, etc.

[0080] The coating methods for the aforementioned tin oxide precursor solution can include spin coating, blade coating, etc. When the coating method is spin coating, the spin coating speed can be 3000 rpm to 5000 rpm, and the spin coating time can be 20 s to 60 s. As an example, the spin coating speed can be 3000 rpm, 3250 rpm, 3500 rpm, 4000 rpm, 4500 rpm, or 5000 rpm, etc.; the spin coating time can be 20 s, 25 s, 30 s, 40 s, 45 s, 55 s, or 60 s, etc.

[0081] The annealing conditions for the coated tin oxide precursor solution include: an annealing time of 30 min to 60 min and an annealing temperature of 100 °C to 180 °C. For example, the annealing time for the coated tin oxide precursor solution can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min, and the annealing temperature can be 100 °C, 120 °C, 130 °C, 140 °C, 160 °C, or 180 °C.

[0082] The thickness of the electron transport layer can be 30nm to 50nm. For example, the thickness of the electron transport layer can be 30nm, 35nm, 40nm, 45nm, or 50nm, etc.

[0083] It should be noted that when the above-mentioned substrate is a crystalline silicon cell, the surface of the crystalline silicon cell that forms the electron transport layer is the main surface of the crystalline silicon cell in which the emitter is disposed.

[0084] By controlling the preparation conditions and thickness of the electron transport layer, electron transport efficiency can be improved, interfacial recombination can be suppressed, and when the substrate 11 is conductive glass, hole diffusion into the substrate 11 can be effectively blocked. When the substrate 11 is a crystalline silicon cell, hole diffusion into the electrode layer 4 can be effectively blocked, which is beneficial to improving the photoelectric conversion efficiency of the double perovskite solar cell.

[0085] The method for preparing the hole transport layer includes: preparing a hole transport precursor solution using lithium bis(trifluoromethanesulfonyl)imide, D2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, and 4-tert-butylpyridine; and coating the hole transport precursor solution to obtain the hole transport layer. Specifically, when the substrate 11 is conductive glass, the pre-prepared hole transport precursor solution is coated onto the surface of the double perovskite film layer 2; when the substrate 11 is a crystalline silicon solar cell, the pre-prepared hole transport precursor solution is coated onto the surface of the substrate 11.

[0086] Preferably, the thickness of the hole transport layer can be 100nm to 300nm. As an example, the thickness of the hole transport layer can be 100nm, 130nm, 150nm, 170nm, 200nm, 250nm, or 300nm, etc.

[0087] Optionally, the method for preparing the hole transport precursor solution includes: dissolving lithium bis(trifluoromethanesulfonyl)imide in a first solvent to obtain a first solution; wherein the first solvent is acetonitrile. The mass concentration of lithium bis(trifluoromethanesulfonyl)imide in the first solution can be 500 mg / mL to 600 mg / mL. As an example, the mass concentration of lithium bis(trifluoromethanesulfonyl)imide in the first solution can be 500 mg / mL, 520 mg / mL, 540 mg / mL, 550 mg / mL, 570 mg / mL, or 600 mg / mL, etc. Dissolving D2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene in a second solvent to obtain a second solution; wherein the second solvent includes chlorobenzene and / or toluene. The mass concentration of D2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene in the second solution can be 60 mg / mL to 100 mg / mL. As an example, the mass concentration of D2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene in the second solution can be 60 mg / mL, 65 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, or 100 mg / mL, etc. The first solution and 4-tert-butylpyridine are added to the second solution and mixed thoroughly to obtain a hole transport precursor solution. The mass concentration of lithium bis(trifluoromethanesulfonyl)imide in the hole transport precursor solution can be 5 mg / mL to 15 mg / mL. As an example, the mass concentration of lithium bis(trifluoromethanesulfonyl)imide in the hole transport precursor solution can be 5 mg / mL, 7 mg / mL, 9 mg / mL, 10 mg / mL, 12 mg / mL, or 15 mg / mL, etc.

[0088] The mass concentration of 4-tert-butylpyridine in the aforementioned hole transport precursor solution is 25 mg / mL to 40 mg / mL. As an example, the mass concentration of 4-tert-butylpyridine in the hole transport precursor solution can be 25 mg / mL, 27 mg / mL, 30 mg / mL, 35 mg / mL, or 40 mg / mL, etc.

[0089] Optionally, the coating method for the aforementioned hole transport precursor solution includes spin coating, blade coating, etc. When spin coating is used, the spin coating speed can be 2000 rpm to 4500 rpm, and the spin coating time can be 20 s to 45 s. As an example, the spin coating speed can be 2000 rpm, 2300 rpm, 2650 rpm, 3250 rpm, 3500 rpm, 4000 rpm, or 4500 rpm, etc. The spin coating time can be 20 s, 22 s, 25 s, 30 s, 35 s, 40 s, or 45 s, etc.

[0090] By controlling the thickness of the hole transport layer and the fabrication process conditions within a suitable range, the hole transport efficiency can be improved. When the substrate 11 is conductive glass, it effectively blocks the diffusion of electrons to the electrode layer 4. When the substrate 11 is a crystalline silicon cell, it effectively blocks the diffusion of electrons to the substrate 11, which is beneficial to improving the photoelectric conversion efficiency of the double perovskite solar cell.

[0091] In an optional embodiment, when the substrate is conductive glass, the method for preparing the electrode layer in step B2 includes: under a vacuum degree of 1×10⁻⁶. -4 Pa ~ 1×10 -5 Under conditions of Pa, a metallic material is deposited on the outer side of the second carrier transport layer at an evaporation rate of 0.5 Å / s to 1 Å / s to form an electrode layer. As an example, the vacuum degree for preparing the electrode layer can be 1 × 10⁻⁶. - 4 Pa, 3×10 -5 Pa, 5×10 -5 Pa, 7×10 -5 Pa or 1×10 -5 Pa, etc.; the evaporation rate can be 0.5 Å / s, 0.6 Å / s, 0.7 Å / s, 0.8 Å / s, 0.9 Å / s or 1.0 Å / s, etc.

[0092] Preferably, when the substrate is conductive glass, the thickness of the electrode layer can be 70nm to 120nm. As an example, when the substrate is conductive glass, the thickness of the electrode layer can be 70nm, 80nm, 90nm, 100nm, 110nm, or 120nm, etc.

[0093] When the substrate is a crystalline silicon solar cell, the method for preparing the electrode layer in step B2 includes: [the process is described in the original text, but the provided text is incomplete and requires further context.] -4 Pa ~ 1×10 -5 Under conditions of Pa, electrode material is deposited on the outer side of the second carrier transport layer using a high-precision mask at an evaporation rate of 0.5 Å / s to 1 Å / s to form an electrode layer. As an example, the vacuum degree for preparing the electrode layer can be 1 × 10⁻⁶. -4 Pa, 3×10 -5 Pa, 5×10 -5 Pa, 7×10 -5 Pa or 1×10 -5 Pa, etc.; the evaporation rate can be 0.5 Å / s, 0.6 Å / s, 0.7 Å / s, 0.8 Å / s, 0.9 Å / s or 1.0 Å / s, etc.

[0094] Preferably, when the substrate is a crystalline silicon cell, the thickness of the electrode layer can be 600nm to 800nm. As an example, when the substrate is a crystalline silicon cell, the thickness of the electrode layer can be 600nm, 630nm, 650nm, 680nm, 700nm, 750nm, or 800nm, etc.

[0095] It should be noted that when the substrate is a crystalline silicon cell, the transparent conductive oxide can completely cover the electron transport layer 3; the metal grid lines can partially cover the transparent conductive oxide to avoid the metal grid lines from causing significant light shading to the cell. Therefore, a high-precision mask can be used to form patterned metal grid lines during the fabrication of the metal grid lines.

[0096] By controlling the fabrication process conditions and thickness of the electrode layer within a suitable range, the electrode layer and the second carrier transport layer 3 can be tightly connected, suppressing the recombination loss of the second carrier, ensuring the efficient transport and extraction of the second carrier, and reducing the obstruction of incident light.

[0097] The method for preparing a double perovskite solar cell according to an embodiment of the present invention involves mixing an organic solvent and precursor raw materials and additives for preparing the double perovskite film, preparing a double perovskite precursor solution, coating the double perovskite precursor solution onto a substrate surface, and annealing it to form a double perovskite film material on the substrate surface. This double perovskite film material is then used as the material for the double perovskite film layer, resulting in a double perovskite film layer. A second carrier transport layer 3 is formed on the outer side of the double perovskite film layer. The additives can serve as bulk passivating agents to regulate the nucleation and crystallization process of the double perovskite film layer. The sulfur atom in the thiol group of the additive can coordinate with both B and C, and the hydrogen atom in the thiol group can form hydrogen bonds with X. This can inhibit the migration of metal ions, passivate vacancy defects, suppress the nucleation process, and reduce the nucleation density during the preparation of the double perovskite thin film. This results in an increase in the size of the double perovskite grains, a decrease in grain boundary density, and the formation of a double perovskite film with larger grain size and higher crystallinity. The larger grain size reduces the number of grain boundaries, and the passivation of grain boundary defects through the aforementioned coordination and hydrogen bond formation reduces structural defects in the double perovskite film. This helps to suppress carrier recombination losses at grain boundaries, promotes carrier transport and separation, lowers the carrier transport barrier, and thus improves the performance of the double perovskite solar cell.

[0098] Meanwhile, by adjusting the thickness and process conditions of each film layer, the effect of each film layer can be optimized, thereby improving the photoelectric conversion efficiency of the double perovskite solar cell and enhancing its structural stability.

[0099] The following examples further illustrate the double perovskite thin film material, its preparation method, and the double perovskite solar cell.

[0100] Example 1

[0101] Conductive glass is provided and ultrasonically treated with glass cleaner, deionized water and ethanol for 15 minutes in sequence, dried with a nitrogen gun and treated under ultraviolet-ozone conditions for 15 minutes.

[0102] A tin oxide precursor solution was prepared using a tin oxide dispersion and water at a volume ratio of 1:4. The tin oxide dispersion contained 15% tin oxide nanoparticles by mass. The prepared tin oxide precursor solution was spin-coated onto a main surface of a treated conductive glass and then annealed to form an electron transport layer with a thickness of 40 nm. The spin-coating conditions included a spin speed of 3000 rpm and a spin time of 30 s; the annealing conditions included an annealing time of 30 min and an annealing temperature of 120 °C.

[0103] 1,4-Dimercaptobenzene was used as an additive. CsBr, AgBr, BiBr3, and 1,4-dimercaptobenzene were dissolved in dimethyl sulfoxide and stirred at 85 °C for 2 h to obtain a bis-perovskite precursor solution. In the bis-perovskite precursor solution, the molar ratio of CsBr:AgBr:BiBr3 was 2:1:1, the molar concentration of AgBr was 0.5 mol / L, and the molar concentration of 1,4-dimercaptobenzene was 7.04 × 10⁻⁶. -3 The substrate, including the electron transport layer and conductive glass, was preheated at 85°C. A double perovskite precursor solution was then spin-coated onto the outer side of the electron transport layer and annealed to form a 300 nm thick double perovskite film on the outer side of the electron transport layer. The spin-coating conditions included: a spin speed of 2000 rpm and a spin time of 45 s; the annealing conditions included: an argon atmosphere, an annealing temperature of 285°C, and an annealing time of 10 min.

[0104] Lithium bis(trifluoromethanesulfonyl)imide was dissolved in acetonitrile to obtain a first solution. 73 mg of D2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene was dissolved in 1 mL of chlorobenzene to obtain a second solution. 18 μL of the first solution and 26.8 mg of 4-tert-butylpyridine solution were added to the second solution and mixed thoroughly to obtain a hole transport precursor solution. The mass concentration of lithium bis(trifluoromethanesulfonyl)imide in the first solution was 520 mg / mL. The hole transport precursor solution was spin-coated onto the outer side of a double perovskite film to form a hole transport layer with a thickness of 200 nm on the outer side of the double perovskite film. The spin-coating conditions included a spin-coating speed of 3000 rpm and a spin-coating time of 30 s.

[0105] The battery semi-finished product, which has formed a double perovskite film layer and a hole transport layer, was placed in a coating machine at a vacuum degree of 5×10⁻⁶. -5After Pa, a metallic material is deposited on the outer side of the hole transport layer at an evaporation rate of 0.7 Å / s to form an electrode layer with a thickness of 80 nm, thereby obtaining the double perovskite solar cell M1. The electrode layer material includes gold.

[0106] Example 2

[0107] The difference compared to Example 1 is that the molar concentration of 1,4-dimercaptobenzene in the bis-perovskite precursor solution is 3.52 × 10⁻⁶. -3 mol / L.

[0108] With the same preparation process and parameters, a double perovskite solar cell M2 was prepared.

[0109] Example 3

[0110] The difference from Example 1 is that the additive used in preparing the double perovskite precursor solution is m-dimercaptobenzene.

[0111] With the same preparation process and parameters, a double perovskite solar cell M3 was prepared.

[0112] Example 4

[0113] The difference compared to Example 3 is that the molar concentration of m-dimercaptobenzene in the bis-perovskite precursor solution is 3.52 × 10⁻⁶. -3 mol / L.

[0114] With the same preparation process and parameters, a double perovskite solar cell M4 was prepared.

[0115] Example 5

[0116] The difference from Example 1 is that the additive used in preparing the double perovskite precursor solution is o-dimercaptobenzene.

[0117] With the same preparation process and parameters, a double perovskite solar cell M5 was prepared.

[0118] Example 6

[0119] The difference from Example 1 is that the additive used in preparing the double perovskite precursor solution is 2,5-dimercaptoterephthalic acid.

[0120] With the same preparation process and parameters, a double perovskite solar cell M6 was prepared.

[0121] Example 7

[0122] The difference compared to Example 6 is that the molar concentration of 2,5-dimercapto-terephthalic acid in the perovskite precursor solution is 3.52 × 10⁻⁶. -3mol / L.

[0123] With the same preparation process and parameters, a double perovskite solar cell M7 was prepared.

[0124] Comparative Example 1

[0125] Compared with Example 1, the difference is that 1,4-dimercaptobenzene is not added during the preparation of the double perovskite precursor solution, thus omitting the step of adding additives to the solution.

[0126] With the same preparation process and parameters, a double perovskite solar cell M8 was prepared.

[0127] Comparative Example 2

[0128] Compared to Example 1, the difference lies in the addition of a phenyl-free solid substance, bis(2-mercaptoethyl) ether, during the preparation of the bis-perovskite precursor solution. The resulting bis-perovskite precursor solution contains an AgBr molar concentration of 0.5 mol / L, with a bis(2-mercaptoethyl) ether molar concentration of 7.04 × 10⁻⁶. -3 mol / L.

[0129] With the same preparation process and parameters, a double perovskite solar cell M9 was prepared.

[0130] Comparative analysis of scanning electron microscope images

[0131] The double perovskite solar cell M1 prepared in Example 1, the double perovskite solar cell M2 prepared in Example 2, and the double perovskite solar cell M8 prepared in Comparative Example 1 were scanned by scanning electron microscopy at the same scale to obtain the scanning electron microscopy images shown in Figures 4(a), 4(b), and 4(c). It can be observed that in battery M8, which was not prepared with additives, the double perovskite film has a smaller grain size and more grain boundaries, leading to a larger carrier recombination loss. However, in batteries M1 and M2, where additives were added during preparation, the double perovskite film's grain size was regulated by the additives, and the grain size of the double perovskite film increased. Furthermore, because the amount of additive added to battery M1 was greater than that to battery M2, the grain size of the double perovskite film in battery M1 was even larger. In other words, the grain size in the double perovskite film increases with the amount of additives added within a certain range. This is because the thiol groups in the additives can coordinate with monovalent silver ions and trivalent bismuth ions, thereby inhibiting the formation of seed crystals and subsequent growth. Within a certain range, the higher the amount of additives added, the fewer seed crystals are formed, the larger the grain size, and the fewer grain boundaries.

[0132] Comparative Analysis of X-ray Diffraction Patterns

[0133] The double perovskite solar cells M1 prepared in Example 1, M2 prepared in Example 2, and M8 prepared in Comparative Example 1 were analyzed using X-ray diffraction, and the results were as follows: Figure 5 The X-ray diffraction pattern shown has the following parameters: The horizontal axis, 2Theta (degree), represents twice the θ angle, in degrees (°). Here, the θ angle refers to the diffraction angle reflecting the interplanar spacing of the crystal. The vertical axis, Intensity (au), represents the diffraction intensity, in arbitrary units. Here, the intensity of the strongest characteristic diffraction peak in the pattern is set to 100 a.u., and the intensities of other characteristic diffraction peaks are relative to the intensity of the strongest characteristic diffraction peak. The baseline of the simulated Cs2AgBiBr6 is the simulated baseline constructed from the diffraction background intensity of Cs2AgBiBr6. FTO refers to fluorine-doped tin oxide in the double perovskite solar cell. The characteristic diffraction peaks of FTO are marked in the curve to distinguish them from the characteristic diffraction peaks of Cs2AgBiBr6. It can be observed that, compared with battery M8 in Comparative Example 1, batteries M1 and M2, which were prepared with additives during the preparation process, have higher characteristic diffraction peaks of Cs2AgBiBr6. Moreover, the peak height of the characteristic diffraction peaks of Cs2AgBiBr6 increases with the increase of additive concentration, indicating that the crystallinity of the double perovskite film layer of batteries M1 and M2 prepared with additives during the preparation process is stronger than that of battery M8 prepared without additives. Furthermore, the crystallinity of the double perovskite film layer increases accordingly with the increase of additive concentration. In addition, there are no other impurity peaks in the spectrum, indicating that the addition of 1,4-dimercaptobenzene during the preparation process will not form other impurity phases. This further proves that additives can be introduced as bulk passivating agents into the preparation process of double perovskite solar cells, and can significantly improve the quality of the double perovskite film layer.

[0134] JV Curve Comparison Analysis

[0135] For the double perovskite solar cells M1~M9 prepared in Examples 1-7 and Comparative Examples 1 and 2, IV tests were performed under the same conditions. The collected data were fitted to a continuous curve with voltage as the abscissa and current density as the ordinate, as shown below. Figure 6 The current density-voltage curve (JV curve) shown is based on... Figure 6The JV curve shown can determine the open-circuit voltage, short-circuit current density, and fill factor for each cell, thereby calculating the photoelectric conversion efficiency for each cell. The open-circuit voltage is the voltage corresponding to a current density of 0 on the JV curve; the short-circuit current density is the current density corresponding to a voltage of 0 on the JV curve; the fill factor is calculated as follows: determine the current density and voltage corresponding to the maximum output power point on the JV curve, calculate the product of the current density and voltage corresponding to the maximum output power point to obtain the cell's maximum output power density, calculate the product of the short-circuit current density and open-circuit voltage to obtain the cell's ideal maximum power density, and the fill factor is equal to the difference between the maximum output power density and the ideal maximum power density.

[0136] The performance parameters shown in Table 1 are obtained through calculation and analysis. It can be seen that the additives added during the preparation of battery M2 are the same as those added during the preparation of battery M1, both being 1,4-dimercaptobenzene containing para-thiol groups. However, because the molar concentration of 1,4-dimercaptobenzene in the perovskite precursor solution corresponding to battery M2 is lower than that in the perovskite precursor solution corresponding to battery M1, the photoelectric conversion efficiency of battery M2 is lower than that of battery M1. The additives added during the preparation of batteries M3 and M4 are meta-dimercaptobenzene containing meta-thiol groups. Since the steric hindrance of the thiol group at the meta position is greater than that at the para position, the larger steric hindrance will affect the bonding of the perovskite molecules. Therefore, battery M3... The photoelectric conversion efficiency of battery M4 is lower than that of battery M1. Furthermore, since the molar concentration of intermediate dimercaprolactone in the bis-perovskite precursor solution corresponding to battery M3 is greater than that in the bis-perovskite precursor solution corresponding to battery M4, the photoelectric conversion efficiency of battery M4 is lower than that of battery M3. The additive added during the preparation of battery M5 is o-dimercaprolactone containing ortho-thiol groups. The molar concentration of o-dimercaprolactone in the bis-perovskite solution corresponding to battery M5 is the same as that of the additive in the bis-perovskite solutions corresponding to batteries M1 and M3. However, since the steric hindrance of the thiol group when it is located in the ortho position is greater than that when it is located in the meta position, the photoelectric conversion efficiency of battery M5 is lower than that of battery M3.The additive used in the preparation of batteries M6 and M7 is 2,5-dimercapto-terephthalic acid, which contains para-thiol and para-carboxyl groups on its benzene ring. Compared to 1,4-dimercaptobenzene, 2,5-dimercapto-terephthalic acid has greater steric hindrance because it also contains two carboxyl groups on its benzene ring. Therefore, the photoelectric conversion efficiency of batteries M6 and M7 is lower than that of battery M1. Furthermore, the molar concentration of 2,5-dimercapto-terephthalic acid in the perovskite precursor solution corresponding to battery M7 is less than... The molar concentration of 2,5-dimercapto-terephthalic acid in the perovskite precursor solution corresponding to battery M6 is different from that of battery M7. The photoelectric conversion efficiency of battery M7 is lower than that of battery M6. Furthermore, the molar concentration of 2,5-dimercapto-terephthalic acid in the perovskite precursor solution corresponding to battery M7 is the same as that of the intermediate dimercapnzene in the perovskite precursor solution corresponding to battery M4. However, at the same molar concentration, the substituents on the benzene ring of 2,5-dimercapto-terephthalic acid, except for the mercapto group, only include the para-position substituents. With only one carboxyl group, the number of substituents other than the thiol group is relatively small. The two carboxyl groups are located at the para position with the largest spatial distance and the carboxyl group is relatively small. In 2,5-dimercapto-terephthalic acid, the para-position dimercaptos, after coordinating with the adjacent perovskite molecule, still tends to have a flat configuration. The two carboxyl groups at the para position have little effect on the steric hindrance after coordinating with the perovskite molecule. However, the dimercaptos at the intermediate position of the meta-dimercaptobenzene, after coordinating with the adjacent perovskite molecule, has a structure more similar to a "V" shape with greater steric hindrance. Therefore, the photoelectric conversion efficiency of battery M4 is lower than that of battery M7. Battery M8 was not prepared with any additives, and its photoelectric conversion efficiency is 1.56%, which is lower than that of batteries M1 to M7. Battery M9 was prepared with the addition of phenyl-free solid bis(2-mercaptoethyl) ether, and its photoelectric conversion efficiency is 1.22%, which is lower than that of batteries M1 to M7. It can be seen that phenyl-free bis(2-mercaptoethyl) ether cannot act as a bulk passivator. ;

[0137] In summary, batteries M1 to M7, which use compounds containing benzene rings and at least two thiol groups substituted at different positions on the benzene rings as additives during the preparation process, exhibit varying degrees of improved photoelectric conversion efficiency compared to batteries M8 and M9. This is because the thiol groups can coordinate with monovalent silver ions and trivalent bismuth ions, thereby increasing the grain size and improving the crystallinity of the double perovskite film. On the other hand, they can passivate the vacancy defects of monovalent silver ions and trivalent bismuth ions in the double perovskite film, reducing ion migration and thus reducing carrier recombination loss, thereby improving the photoelectric efficiency of the solar cell.

[0138] Among them, the battery with added additives containing para-thiol groups has a higher photoelectric conversion efficiency. This is because the para-thiol structure can coordinate with monovalent silver ions and trivalent bismuth ions in the adjacent double perovskite octahedron, causing the additive to tend to be adsorbed parallel to the surface of the double perovskite film, thereby avoiding the generation of additional steric hindrance and further improving the photoelectric conversion efficiency of the battery.

[0139] For batteries with the same additives, the photoelectric conversion efficiency increases with the increase of the additive concentration in the double perovskite precursor solution. This is because the mercapto groups in the additives can coordinate with monovalent silver ions and trivalent bismuth ions, thereby inhibiting the formation of seed crystals and subsequent growth. The higher the amount of additives added, the fewer seed crystals are formed, the larger the grain size, and the fewer grain boundaries. That is, the grain size in the double perovskite film increases within a certain range with the increase of the amount of additives, which makes the photoelectric conversion efficiency of the battery increase with the increase of the amount of additives added.

[0140] Table 1

[0141] Note: Voc represents open-circuit voltage; Jsc represents short-circuit current density; FF represents fill factor; PCE represents photoelectric conversion efficiency.

[0142] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A double perovskite thin film material, characterized in that, include: A2BCX6 type double perovskite, wherein A is an alkali metal cation, B is a monovalent metal cation, C is a trivalent metal cation, and X is a halide anion; Additives are compounds comprising a benzene ring and at least two thiol groups substituted at different positions on the benzene ring.

2. The double perovskite thin film material according to claim 1, characterized in that, The molar ratio of the element corresponding to B in the double perovskite to the additive is 150:(0.5-6).

3. The double perovskite thin film material according to claim 1, characterized in that, The additive contains two thiol groups at the para-position of the benzene ring.

4. A double perovskite thin film material according to any one of claims 1 to 3, characterized in that, The additives include at least one of 1,4-dimercaptobenzene, 2,5-dimercaptoterephthalic acid, benzene hexathiophenol, 2,5-diamino-1,4-benzene dithiophenol dihydrochloride, and 1,4-benzene dimethyl mercaptan.

5. The double perovskite thin film material according to claim 1, characterized in that, The alkali metal cations include one or more of sodium ions, potassium ions, rubidium ions, and cesium ions; And / or, The monovalent metal cation includes one or more of monovalent copper ions, monovalent silver ions, and monovalent gold ions; And / or, The trivalent metal cations include one or more of trivalent bismuth ions, trivalent antimony ions, and trivalent indium ions.

6. A method for preparing a double perovskite thin film material, characterized in that, The preparation of the double perovskite thin film material according to any one of claims 1 to 5 comprises: Organic solvents and precursor materials for preparing double perovskites are mixed with additives to prepare a double perovskite precursor solution. The double perovskite precursor solution is coated onto the substrate surface, and after annealing, the double perovskite thin film material is formed on the substrate surface.

7. The method for preparing the double perovskite thin film material according to claim 6, characterized in that, The precursor materials for the double perovskite include AX, BX and CX3; And / or, The organic solvent includes dimethyl sulfoxide and / or N,N-dimethylformamide; And / or, The annealing conditions include: an inert gas atmosphere, an annealing temperature of 250℃~300℃, and an annealing time of 5min~20min.

8. The method for preparing the double perovskite thin film material according to claim 7, characterized in that, When AX, BX and CX3 are used as precursor materials for preparing the double perovskite, the molar ratio of AX:BX:CX3 is 2:1:1, and the concentration of BX in the double perovskite precursor solution is 0.1 mol / L to 0.8 mol / L.

9. A double perovskite solar cell, comprising a substrate, and a first carrier transport layer, a double perovskite film layer, and a second carrier transport layer sequentially stacked on the surface of the substrate, characterized in that, The material of the double perovskite film layer is the double perovskite thin film material according to any one of claims 1 to 5.

10. A double perovskite solar cell according to claim 9, characterized in that, The thickness of the double perovskite film is 200nm~300nm.

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