Solar cell and preparation method thereof, laminated cell and photovoltaic module

Abstract

The invention relates to a solar cell and a preparation method thereof, a laminated cell and a photovoltaic module. The preparation method of the solar cell comprises the following steps: providing a substrate; preparing a titanium chalcogenide by adopting a solid-phase synthesis method; the preparation method comprises the following steps: performing ultrasonic treatment on a mixture of a titanium chalcogenide and an oxidizing agent to obtain a titanium dioxide amorphous precursor solution; coating the surface of a substrate with the titanium dioxide amorphous precursor solution, and performing first heat treatment to obtain an electron transfer layer; forming a perovskite layer on the surface of the electron transport layer; forming a hole transport layer on the surface of the titanium ore light absorption layer; and forming an electrode layer on the surface of the hole transport layer. According to the preparation method, the amorphous sol which is low in viscosity, good in flowability and uniform in dispersion is prepared by combining a solid phase method with ultrasonic treatment, then the uniform wet film which is high in wettability and stable in performance is prepared, it can be guaranteed that the film forming thickness is uniform, meanwhile, film liquid can be rapidly and uniformly spread on the surface of a substrate, and the preparation method is suitable for large-area preparation.

Description

Technical Field

[0001] This application relates to the field of photovoltaic cell technology, specifically to a solar cell and its preparation method, a tandem cell, and a photovoltaic module. Background Technology

[0002] Solar energy boasts advantages such as safety, zero pollution, and lack of geographical limitations, making it the most widely used and promising renewable energy source. Among various technologies for effectively utilizing solar energy, photovoltaic power generation is undoubtedly one of the most promising directions. Among numerous new types of solar cells, perovskite solar cells exhibit excellent photoelectric conversion performance and require abundant raw material reserves, making them one of the most promising solar cell technologies.

[0003] Perovskite solar cells consist of a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer. Among these, the electron transport layer is commonly made of metal oxides. How to provide a metal oxide electron transport layer that is simple to fabricate and highly uniform is an urgent problem to be solved in this field. Summary of the Invention

[0004] In view of this, this application proposes a solar cell and its preparation method, a tandem cell and a photovoltaic module. The preparation method of this application is simple and easy to implement, suitable for large-area preparation, and can prepare a high-quality titanium dioxide electron transport layer.

[0005] In a first aspect, embodiments of this application provide a method for preparing a solar cell, comprising the following steps: Provide a base; Chalcogenides of titanium were prepared by solid-phase synthesis. The mixture of the titanium chalcogenide and the oxidant was ultrasonically treated to obtain an amorphous titanium dioxide precursor solution. The amorphous titanium dioxide precursor liquid is coated on the surface of the substrate and subjected to a first heat treatment to obtain an electron transport layer. A perovskite layer is formed on the surface of the electron transport layer; A hole transport layer is formed on the surface of the titanium dioxide light-absorbing layer; An electrode layer is formed on the surface of the hole transport layer.

[0006] Secondly, embodiments of this application provide a solar cell, the solar cell comprising: a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer, wherein the electron transport layer is located between the substrate and the perovskite layer, the hole transport layer is located between the perovskite layer and the electrode layer, and the electron transport layer comprises a plurality of titanium dioxide crystals, the plurality of titanium dioxide crystals being stacked to form a dendritic structure.

[0007] Thirdly, embodiments of this application provide a stacked battery, comprising: a bottom battery, a composite layer, and a top battery stacked sequentially along a preset direction; wherein the top battery is a solar cell formed by the method for preparing a solar cell as described in the first aspect or a solar cell as described in the second aspect.

[0008] Fourthly, embodiments of this application provide a photovoltaic module, the photovoltaic module comprising: A battery string, wherein the battery string is composed of multiple solar cells formed by the preparation method described in the first aspect or solar cells described in the second aspect connected together; An encapsulation layer that covers the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

[0009] The technical solution of this application has at least the following beneficial effects: This application first obtains titanium chalcogenides through solid-state synthesis, then ultrasonically treats a mixture of titanium chalcogenides and an oxidant to prepare a low-viscosity, highly fluid, and uniformly dispersed amorphous titanium dioxide sol without introducing impurity functional groups. The particle size of titanium dioxide can be precisely adjusted by controlling the addition of the titanium chalcogenides and the oxidant. Finally, the amorphous titanium dioxide precursor solution is coated onto the surface of a substrate to obtain a uniform wet film with high wettability and stable performance. A first heat treatment is then performed to prepare a uniform and dense titanium dioxide film. The crystals in the titanium dioxide film have a dendritic structure with a unique three-dimensional branching structure, which can effectively shorten the electron diffusion distance. Moreover, the dendritic structure of the titanium dioxide crystals increases its contact area with the perovskite layer and the substrate, providing more charge extraction sites, allowing electrons generated in the perovskite layer to be quickly captured and transported, thereby enhancing the light-harvesting performance. The preparation method of this application utilizes a solid-state method combined with ultrasonic treatment to prepare a low-viscosity, highly fluid, and uniformly dispersed amorphous sol, thereby preparing a highly wettable, stable, and uniform wet film. This ensures uniform film thickness, and the film solution can spread rapidly and uniformly on the substrate surface, reducing defects such as edge shrinkage and pinholes. The preparation method of this application is simple and easy to implement, suitable for large-area preparation, and can produce highly uniform large-area titanium dioxide crystalline films. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart illustrating the fabrication process of a solar cell provided in an embodiment of this application. Figure 2 This is a schematic diagram of the structure of a solar cell provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application; Figure 4 The XRD pattern of TiS2 prepared in Example 1 of this application; Figure 5 XRD pattern of amorphous silica in the amorphous silica precursor solution prepared in the embodiments of this application; Figure 6 The image shows the XRD pattern of the silicon dioxide crystal in the silicon dioxide electron transport layer prepared in Example 1 of this application. Figure 7 The XRD patterns of amorphous silicon dioxide crystallized at different temperatures are shown in this application.

[0012] Figure label: 1000 - Photovoltaic modules; 100-Solar Cell; 1-Base; 2-Electron transport layer; 3-Perovskite layer; 4-Hole transport layer; 5-Electrode layer; 200 - First cover plate; 300 - First encapsulating adhesive layer; 400 - Second encapsulating adhesive layer; 500 - Second cover plate. Detailed Implementation

[0013] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0014] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0015] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0016] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0017] The structure of a perovskite solar cell includes a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer. Metal oxides, such as titanium dioxide, are commonly used as the electron transport layer material for collecting and transporting photogenerated carriers. In the fabrication process of the electron transport layer, "large-area fabrication" is a key process feature and technological direction.

[0018] In related technologies, the sol-gel method is often used to prepare titanium dioxide electron transport layers. The sol-gel method uses titanium precursors (such as tetrabutyl titanate, tetraisopropyl titanate, etc.) to form a sol through hydrolysis and condensation, and then forms a film through spin coating or drop coating, and finally obtains a titanium dioxide film through curing. However, the sol prepared by the above process has low film-forming efficiency, poor sol stability, and insufficient film performance after low-temperature curing, making it difficult to prepare on a large area, which limits the application of metal oxides in perovskite solar cells.

[0019] In view of this, this application provides a method for preparing a solar cell. Figure 1 A flowchart illustrating the fabrication process of the solar cell of this application is shown, as follows: Figure 1 As shown, the method for fabricating a solar cell includes the following steps: Provide a base; Chalcogenides of titanium were prepared by solid-phase synthesis. A mixture of titanium chalcogenides and an oxidant was ultrasonically treated to obtain an amorphous titanium dioxide precursor solution. Amorphous titanium dioxide precursor solution is coated onto the surface of the substrate and subjected to a first heat treatment to obtain an electron transport layer. A perovskite layer is formed on the surface of the electron transport layer; A hole transport layer is formed on the surface of the titanium dioxide light-absorbing layer; An electrode layer is formed on the surface of the hole transport layer.

[0020] In the above scheme, this application first obtains titanium chalcogenides through solid-state synthesis, and then ultrasonically treats the mixture of titanium chalcogenides and oxidant to prepare a low-viscosity, high-flowability, and uniformly dispersed titanium dioxide amorphous sol without introducing impurity functional groups. The particle size of titanium dioxide can be precisely adjusted by controlling the addition mass of titanium chalcogenides and oxidant. Finally, the titanium dioxide amorphous precursor solution is coated on the surface of the substrate to obtain a uniform wet film with high wettability and stable performance. A uniform and dense titanium dioxide film is prepared by a first heat treatment. The crystals in the titanium dioxide film have a dendritic structure with a unique three-dimensional branching structure, which can effectively shorten the electron diffusion distance. Moreover, the dendritic structure of titanium dioxide crystals can increase its contact area with the perovskite layer and the substrate, providing more charge extraction sites, so that electrons generated in the perovskite layer can be quickly captured and transported, thereby enhancing the light-harvesting performance. The preparation method of this application utilizes a solid-state method combined with ultrasonic treatment to prepare a low-viscosity, highly fluid, and uniformly dispersed amorphous sol, thereby preparing a highly wettable, stable, and uniform wet film. This ensures uniform film thickness, and the film solution can spread rapidly and uniformly on the substrate surface, reducing defects such as edge shrinkage and pinholes. The preparation method of this application is simple and easy to implement, suitable for large-area preparation, and can produce highly uniform large-area titanium dioxide crystalline films.

[0021] Compared to traditional titanium dioxide amorphous sols prepared using organic titanium precursors (such as tetrabutyl titanate, tetraisopropyl titanate, etc.), solvents, and catalysts, the titanium chalcogenides prepared by the solid-phase synthesis method in this application, as raw materials for preparing amorphous titanium dioxide precursor solutions, do not require the addition of solvents and catalysts. This avoids the influence of impurities and functional groups on the quality of titanium dioxide films. Moreover, during large-area wet film preparation, the influence of external temperature, humidity, and airflow is relatively small (the hydrolysis of tetrabutyl titanate is extremely sensitive to temperature, humidity, water content, and reaction rate). This is beneficial for improving the quality of the prepared electron transport layer, enhancing the extraction of photogenerated electrons from the electron transport layer, and thus improving the efficiency of the prepared solar cells.

[0022] The preparation method of the solar cell of this application is described in detail below.

[0023] S100 provides a substrate.

[0024] In some embodiments, the substrate includes a rigid substrate or a flexible substrate, and the preparation method of this application is applicable to both rigid and flexible substrates. For example, the rigid substrate includes, but is not limited to, at least one of indium tin oxide, indium tin oxide, aluminum-doped zinc oxide, and antimony-doped tin oxide. The flexible substrate includes at least one of polyethylene terephthalate, polyimide, and polyethylene naphthalate.

[0025] In some embodiments, the thickness of the substrate is 80nm to 200nm, specifically 80nm, 90nm, 100nm, 120nm, 130nm, 150nm, 160nm, 180nm, 190nm, 200nm, or any two of the above values. Controlling the substrate thickness within the above range allows for a balance between conductivity and transmittance.

[0026] In some embodiments, after providing the substrate, the process further includes ultrasonically cleaning the substrate sequentially with deionized water, acetone, and ethanol for 15 to 30 minutes.

[0027] S200, a titanium dioxide electron transport layer is formed on the substrate surface.

[0028] S201. Preparation of titanium chalcogenides by solid-phase synthesis.

[0029] Specifically, the preparation of titanium chalcogenides by solid-state synthesis includes: mixing elemental titanium and chalcogenides in a molar ratio of 1:(2.0~2.2) and then subjecting the mixture to a second heat treatment to obtain titanium chalcogenides.

[0030] In some embodiments, the molar ratio of elemental titanium to chalcogenide is 1:(2.0~2.2), specifically 1:2.0, 1:2.05, 1:2.1, 1:2.15, 1:2.2, or any two of the above values. Controlling the molar ratio of elemental titanium to chalcogenide within this range pre-compensates for sulfur volatilization during the second heat treatment process, which is beneficial for obtaining high-purity titanium sulfides. Depending on the choice of chalcogenide, the titanium sulfide is at least one of titanium disulfide, selenium disulfide, and tellurium disulfide.

[0031] It is understood that the purity of the titanium in this application is greater than or equal to 99%, and the purity of the chalcogenide elements is greater than or equal to 99%, in order to avoid the generation of impurities in the product.

[0032] In some embodiments, the chalcogenides include at least one of elemental sulfur, elemental selenium, and elemental tellurium. This application uses chalcogenides as raw materials for the reaction with elemental titanium, which offers low raw material costs, a direct reaction pathway, and superior environmental friendliness. Especially in large-scale industrial production, it avoids the high cost and complex processes of traditional organotitanium precursors (such as tetrabutyl titanate), while utilizing the high reactivity of titanium sulfide to achieve efficient conversion. The following explanation uses elemental sulfur as an example of chalcogenides.

[0033] In some embodiments, the mixing is carried out in a ball mill, through which the titanium and chalcogen elements are thoroughly and uniformly mixed.

[0034] In some embodiments, the temperature of the second heat treatment is 700°C to 1200°C, specifically 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or any two of the above values. Controlling the temperature of the second heat treatment within the above range is beneficial for the full bonding of the atoms of the chalcogenide and titanium elements, and is conducive to the formation of high-purity titanium disulfide.

[0035] Preferably, the second heat treatment employs a segmented heating process: first, the temperature is raised to 400℃~600℃ and held for 1h~10h, then raised to 700℃~1200℃ and held for 15h~24h, followed by slow cooling to room temperature. The segmented heating process at 400℃~600℃ avoids rapid volatilization of chalcogens due to localized overheating, while simultaneously removing moisture and volatile impurities from the raw materials. The treatment at 700℃~1200℃ promotes the full bonding of chalcogens and titanium, resulting in sufficient grain growth in the product.

[0036] In some embodiments, the heating rate of the second heat treatment is 1°C / min to 10°C / min, specifically 1°C / min, 3°C / min, 5°C / min, 7°C / min, 9°C / min, 10°C / min, or any two of the above values. Controlling the heating rate of the second heat treatment within this range ensures that the raw material particles are heated evenly and avoids localized overheating that could cause them to stick together. Preferably, the heating rate of the second heat treatment is 5°C / min to 10°C / min.

[0037] In some embodiments, the holding time for the second heat treatment is 20h to 48h, specifically 20h, 24h, 28h, 30h, 32h, 36h, 40h, 44h, 48h, or any two of the above values. Controlling the holding time of the second heat treatment within this range ensures complete reaction of the raw materials, reduces the residue of unreacted materials, and allows for sufficient growth of product grains, thereby improving crystallinity.

[0038] S202. A mixture of titanium chalcogenides and an oxidant is ultrasonically treated to obtain an amorphous titanium dioxide precursor solution.

[0039] Specifically: a titanium chalcogenide compound and a solution containing an oxidant are mixed to obtain a premix, which is then subjected to ultrasonic treatment and centrifugation in an oxygen atmosphere.

[0040] This application first mixes titanium chalcogenides with a solution containing an oxidant, then sonicates the mixture in an oxygen atmosphere. This sonication not only promotes uniform dispersion of the components, ensuring thorough mixing of the titanium chalcogenides and oxidant, but also generates heat that accelerates the reaction between the chalcogenides and oxidant. Furthermore, the oxygen atmosphere provides a rich oxygen environment for the reaction of the titanium chalcogenides, promoting uniform dispersion of the titanium sulfides and enhancing their contact reaction with the oxidant. It also enhances the redox ability of the oxidant, thus facilitating the production of high-purity titanium dioxide. This application utilizes both the oxidant and the oxygen atmosphere to provide the oxygen source, ensuring the complete oxidation of the titanium chalcogenides and generating a high-purity amorphous titanium dioxide precursor solution.

[0041] In some embodiments, the solute in the solution containing the oxidant includes hydrogen peroxide. Taking elemental sulfur as an example, hydrogen peroxide can deeply oxidize sulfur ions to form sulfate ions, while titanium ions form an unstable titanium hydrogen peroxide complex with hydrogen peroxide, ultimately transforming into titanium disulfide.

[0042] In some embodiments, the solvent in the solution containing the oxidant includes at least one of deionized water and ethanol. The addition of the solvent promotes thorough mixing of the titanium chalcogenides and the oxidant, and the solvent used in this application is environmentally friendly.

[0043] In some embodiments, the mass ratio of titanium chalcogenides to oxidant is 1:(5~20), specifically 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, or any two of the above values. Controlling the mass ratio of titanium chalcogenides to oxidant within the above range is beneficial for the complete oxidation of titanium ions to form high-purity titanium dioxide.

[0044] This application does not restrict the flow rate of the oxygen atmosphere; it only requires that the ultrasonic treatment be carried out within the oxygen atmosphere.

[0045] In some embodiments, the power of the ultrasonic treatment is 500W to 1000W, specifically 500W, 600W, 700W, 800W, 900W, 1000W, or any two of the above values. The ultrasonic treatment time is 1min to 3min, specifically 1min, 1.5min, 2min, 2.5min, 3min, or any two of the above values. This application controls the power and time of the ultrasonic treatment to provide a strong activation reaction interface for the reaction, promoting the full reaction of titanium chalcogenides and oxidants at a lower temperature, and also improving the uniformity of the reaction products.

[0046] In some embodiments, the ultrasonic treatment further includes a step of mixing the ultrasonically treated product with a hydrolysate, wherein the hydrolysate promotes further hydrolysis-condensation reaction of the ultrasonically treated product to form an amorphous film liquid, thus obtaining an amorphous titanium dioxide precursor liquid. The viscosity of this amorphous titanium dioxide precursor liquid is easily controllable, allowing it to spread uniformly on the substrate surface during coating. Furthermore, this amorphous titanium dioxide precursor liquid can be subsequently used for film formation at lower temperatures, eliminating the need for high-temperature annealing and avoiding the heat resistance limit of the flexible substrate, making it suitable for the preparation of electron transport layers on flexible substrates.

[0047] In some embodiments, the hydrolysate includes at least one of deionized water and an alcohol compound.

[0048] In some embodiments, the volume ratio of the product obtained from ultrasonic treatment to the hydrolysate is 1:(0.2~1), specifically 1:0.2, 1:0.4, 1:0.5, 1:0.6, 1:0.8, 1:1 or any two of the above values.

[0049] This application abandons the conventional solution-based preparation process and adopts a solid-phase synthesis method as the first step in the preparation of raw materials. This allows for precise control of the addition amounts of elemental titanium and chalcogenides to prepare high-purity titanium chalcogenides. The elemental titanium and chalcogenides can be accurately weighed. Furthermore, the titanium chalcogenides are mixed with a solution containing an oxidant and subjected to ultrasonic treatment to obtain an amorphous titanium dioxide precursor solution. During the preparation of the amorphous titanium dioxide precursor solution, environmental temperature and humidity do not significantly affect the purity of the product. The preparation method of this application has low equipment requirements, does not require the use of organic solvents, eliminates waste liquid treatment issues, and avoids the impact of solvent evaporation on the prepared wet film, which is beneficial for obtaining a film solution with low viscosity, good flowability, and uniform dispersion.

[0050] S203. Amorphous titanium dioxide precursor liquid is coated on the surface of the substrate and subjected to a first heat treatment to obtain an electron transport layer.

[0051] In some embodiments, the coating includes spin coating. The low-viscosity, high-flowability, and uniformly dispersed amorphous titanium dioxide precursor liquid prepared in this application can be spin-coated over a large area onto the surface of the substrate, enabling the fabrication of a large-area titanium dioxide electron transport layer.

[0052] In some embodiments, the spin coating speed is 3000 rpm to 6000 rpm, specifically 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm, 6000 rpm or any two of the above values.

[0053] In some embodiments, the spin coating time is 10s to 50s, specifically 10s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, or any two of the above values. Preferably, the spin coating time is 20s to 35s.

[0054] In some embodiments, the temperature of the first heat treatment is greater than or equal to 200°C, specifically 200°C, 250°C, 300°C, 350°C, 400°C, 500°C, 600°C, or any two of the above values. The titanium dioxide amorphous precursor liquid of this application can crystallize at lower temperatures (300°C and below) and at higher temperatures (above 300°C), thus meeting the needs of preparing titanium dioxide electron transport layers with various requirements.

[0055] In some embodiments, the first heat treatment time is 1 min to 3 min, specifically 1 min, 1.5 min, 2 min, 2.5 min, 3 min, or any two of the above values.

[0056] In some embodiments, the heating rate of the first heat treatment is 1℃ / min to 10℃ / min, specifically 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any two of the above values.

[0057] In some embodiments, the thickness of the electron transport layer is 100nm to 300nm, specifically 100nm, 150nm, 200nm, 250nm, 300nm, or any two of the above values. The electron transport layer of this application has a suitable thickness, enabling close contact between the electron transport layer and the perovskite layer, effectively improving the extraction of photogenerated electrons.

[0058] S300, a perovskite layer is formed on the surface of the electron transport layer.

[0059] Specifically: A perovskite precursor solution is coated onto the surface of the electron transport layer, spin-coated at 3000-5000 rpm for 20-30 seconds, and then annealed at 90-100℃ for 10 minutes to obtain the perovskite layer. The solute in the perovskite precursor solution is 3-bromobenzylammonium iodide or 3-chlorobenzylammonium iodide, methylammonium chloride, and lead iodide. The solvent in the perovskite precursor solution is N-dimethylformamide and dimethyl sulfoxide.

[0060] In some embodiments, the thickness of the perovskite layer is 300nm to 800nm. Specifically, the thickness of the perovskite layer can be 300nm, 350nm, 420nm, 480nm, 500nm, 600nm, 630nm, 700nm, 720nm, 750nm, 800nm, or any two of the above values. Controlling the thickness of the perovskite layer within the above range is beneficial for light absorption and suppresses carrier recombination.

[0061] S400, a hole transport layer is formed on the surface of the titanium dioxide light-absorbing layer.

[0062] Specifically: An organic material containing at least one of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] and poly3-hexylthiophene, or an inorganic material containing at least one of CuI, CuSCN, TiO2 and SnO2, is dissolved in a solvent (e.g., chlorobenzene) to obtain a mixed solution. The mixed solution is coated onto the surface of a perovskite layer and spin-coated at a speed of 4000 rpm to 5000 rpm for 20 to 30 seconds, followed by annealing at 90°C to 100°C for 10 minutes to obtain a hole transport layer.

[0063] In some embodiments, the thickness of the hole transport layer is 1nm to 200nm. Specifically, the thickness of the hole transport layer can be 1nm, 10nm, 20nm, 50nm, 100nm, 120nm, 156nm, 170nm, 180nm, 195nm, 200nm, or any two of the above values. Controlling the thickness of the hole transport layer within the above range is beneficial to improving the open-circuit voltage and fill factor.

[0064] S500, an electrode layer is formed on the surface of the hole transport layer.

[0065] Specifically: The product obtained in S400 is placed in a vacuum evaporation chamber, and a metal material (such as at least one of gold, silver, copper, aluminum and chromium) is deposited on the surface of the hole transport layer to obtain an electrode layer.

[0066] Based on the same inventive concept, embodiments of this application also provide solar cells prepared by the above-described preparation method. Figure 2 A schematic diagram of the structure of the solar cell provided in this application is shown, as follows: Figure 2 As shown, it includes: a substrate 1, an electron transport layer 2, a perovskite layer 3, a hole transport layer 4, and an electrode layer 5. The electron transport layer 2 is located between the substrate 1 and the perovskite layer 3, and the hole transport layer 4 is located between the perovskite layer 3 and the electrode layer 5. The electron transport layer 2 includes multiple titanium dioxide crystals, which are stacked to form a dendritic structure.

[0067] In the above-described scheme, the electron transport layer 2 of this application includes dendritic titanium dioxide crystals. These dendritic titanium dioxide crystals possess a unique three-dimensional branching structure, which can effectively shorten the electron diffusion distance. Furthermore, the dendritic titanium dioxide crystals can increase their contact area with the perovskite layer 3, providing more charge extraction sites, allowing electrons generated in the perovskite layer 3 to be quickly captured and transported, thereby enhancing light-harvesting performance. The solar cell of this application exhibits excellent charge separation efficiency and charge transport efficiency, significantly improving the photoelectric conversion efficiency and long-term stability of the solar cell.

[0068] In some embodiments, the thickness of the electron transport layer 2 is 100nm to 300nm, specifically 100nm, 150nm, 200nm, 250nm, 300nm, or any two of the above values. The electron transport layer 2 of this application has a suitable thickness, enabling close contact between the electron transport layer 2 and the perovskite layer 3 and the substrate 1, respectively, effectively improving the extraction of photogenerated electrons.

[0069] In some embodiments, the particle size of the titanium dioxide crystals is 100 nm to 2 μm, specifically 100 nm, 300 nm, 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, or any two of the above values. The titanium dioxide crystals in this application have a particle size in the nanometer and / or micrometer range, which allows the electron transport layer 2 to have both a high specific surface area and good structural stability, thereby synergistically improving the charge extraction efficiency and long-term reliability of the solar cell.

[0070] In some embodiments, the titanium dioxide crystals are rutile or anatase.

[0071] It is understood that the solar cell prepared by the above-described method in this application is a conventional perovskite solar cell. A conventional perovskite solar cell, from top to bottom, consists of a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer. Based on the concept of this invention, those skilled in the art can also prepare inverted perovskite solar cells. Inverted perovskite cells reverse the positions of the electron transport layer and the hole transport layer, and their structure, from bottom to top, typically consists of a substrate, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer.

[0072] Based on the same inventive concept, this application also provides a tandem battery, including: a bottom cell, a composite layer and a top cell stacked sequentially along a preset direction; wherein, the top cell, as a solar cell prepared by the above-described preparation method, can endow the tandem battery with higher photoelectric conversion performance.

[0073] It is understood that tandem solar cells include, but are not limited to, two-terminal tandem solar cells, three-terminal tandem solar cells, and four-terminal tandem solar cells. Further, tandem solar cells include, but are not limited to, perovskite solar cells stacked with crystalline silicon solar cells, perovskite solar cells stacked with perovskite solar cells, and perovskite solar cells stacked with thin-film solar cells. Thin-film solar cells include, but are not limited to, perovskite solar thin-film solar cells, copper indium selenide solar thin-film solar cells, gallium arsenide solar thin-film solar cells, and cadmium sulfide solar thin-film solar cells. Crystalline silicon solar cells include, but are not limited to, PERC cells (passivated emitter and back contact cells), IBC cells (interdigitated back contact cells), TOPCon cells (tunneling oxide passivated contact cells), HJT cells (heterojunction cells), and HBC cells (back contact junction cells).

[0074] Based on the same inventive concept, this application also provides a photovoltaic module, which includes: A battery string is formed by connecting multiple solar cells prepared by the above-described preparation method. Encapsulation layer, which covers the surface of the battery string; Cover plate, used to cover the surface of the encapsulation layer away from the battery string.

[0075] Specifically, please refer to Figure 3 The photovoltaic module 1000 includes a first cover plate 200, a first encapsulating layer 300, a solar cell string, a second encapsulating layer 400, and a second cover plate 500.

[0076] In some embodiments, the solar cell string includes a plurality of solar cells 100 as described above connected by conductive strips. The connection between the solar cells 100 can be partially stacked or spliced.

[0077] In some embodiments, the first cover plate 200 and the second cover plate 500 can be transparent or opaque covers, such as glass covers or plastic covers.

[0078] The first encapsulating adhesive layer 300 is in contact with and bonded to the first cover plate 200 and the battery string on both sides, respectively. The second encapsulating adhesive layer 400 is in contact with and bonded to the second cover plate 500 and the battery string on both sides, respectively. The first encapsulating adhesive layer 300 and the second encapsulating adhesive layer 400 can be ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene coelastomer (POE) film, or polyethylene terephthalate (PET) film, respectively.

[0079] The photovoltaic module 1000 can also be fully encapsulated on the sides, that is, the sides of the photovoltaic module 1000 are completely covered and encapsulated with encapsulating tape to prevent lamination shift during the lamination process.

[0080] The photovoltaic module 1000 also includes an edge sealing component, which is fixedly encapsulated on a portion of the edge of the photovoltaic module 1000. This edge sealing component can be fixedly encapsulated on the edge of the photovoltaic module 1000 near a corner. The edge sealing component can be a high-temperature resistant tape. This high-temperature resistant tape has excellent high-temperature resistance properties and will not decompose or detach during lamination, ensuring reliable encapsulation of the photovoltaic module 1000. The two ends of the high-temperature resistant tape are respectively fixed to the second cover plate 500 and the first cover plate 200. The two ends of the high-temperature resistant tape can be bonded to the second cover plate 500 and the first cover plate 200 respectively, while the middle portion can limit the side of the photovoltaic module 1000, preventing lamination displacement of the photovoltaic module 1000 during the lamination process.

[0081] The embodiments of this application will be further described below with reference to several examples. However, the embodiments of this application are not limited to the specific embodiments described below. Appropriate modifications and implementations can be made within the scope of protection.

[0082] Example 1 (1) High-purity titanium (purity greater than or equal to 99.9%) and high-purity sulfur (purity greater than or equal to 99.9%) with a molar ratio of 1:2.2 are placed in a ball mill and ball-milled for 5h~6h. After mixing, the resulting material is placed in a vacuum sintering furnace and heated to 1000℃ at a rate of 5℃ / min and held for 24h to obtain titanium disulfide.

[0083] (2) Titanium disulfide, hydrogen peroxide, and deionized water were mixed and ultrasonically treated in an oxygen atmosphere for 2 min. The ultrasonic power was 800 W. The mass ratio of TiS2 to hydrogen peroxide was 1:8, and the mass ratio of hydrogen peroxide to deionized water was 1:1. The ultrasonically obtained product was placed in deionized water for 1 h to hydrolyze and obtain an amorphous titanium dioxide precursor solution.

[0084] (3) Clean the ITO glass slides with deionized water, acetone and ethanol in sequence for 15 min to 20 min, and then dry them.

[0085] (4) The titanium dioxide amorphous precursor liquid obtained in step (2) is spin-coated onto an ITO glass plate at a speed of 3000 rpm for 20 s, and then placed in a vacuum sintering furnace and heated to 500 ℃ at a rate of 5 ℃ / min for 3 min to obtain a white anatase type titanium dioxide electron transport layer with a thickness of 170 nm.

[0086] (5) Cool the product obtained in step (4) to room temperature, preheat it at 130°C for 3 min to 5 min, take 50 μL of perovskite solution (3-chlorobenzyl ammonium iodide, methyl ammonium chloride, lead iodide mixed in N,N-dimethylformamide and dimethyl sulfoxide) spin-coat the electron transport layer surface of the product obtained in step (4) at a speed of 4000 rpm for 20 s, and then anneal it at 90°C for 10 min to prepare the perovskite layer.

[0087] (6) 10 mg of poly(3-hexylthiophene) dissolved in 1 mL of chlorobenzene was dropped onto the surface of the perovskite layer, and then spin-coated onto the surface of the perovskite layer at a speed of 4000 rpm for 20 s. The layer was then annealed at 90 °C for 10 min to prepare the hole transport layer.

[0088] (7) Place the product obtained in step (6) in a vacuum evaporation chamber and deposit copper onto the hole transport layer to obtain a solar cell.

[0089] Figure 4 The XRD pattern of the titanium disulfide prepared in step (1) is shown, as follows: Figure 4 It is evident that this application yielded pure-phase titanium disulfide.

[0090] Figure 5 The SEM image of the amorphous titanium dioxide precursor solution in step (2) is shown, as follows. Figure 5 It can be seen that the titanium dioxide in the amorphous titanium dioxide precursor solution exhibits a nanosheet structure.

[0091] Figure 6 The SEM image of the titanium dioxide electron transport layer prepared in step (4) is shown, as follows. Figure 6 It is known that titanium dioxide has a nano-dendritic structure and a uniform texture, indicating that this application has prepared a titanium dioxide electron transport layer with a large area distribution.

[0092] Example 2 Unlike Example 1, (4) the titanium dioxide amorphous precursor liquid obtained in step (2) was spin-coated onto an ITO glass plate at a speed of 4500 rpm for 25 s, and then placed in a vacuum sintering furnace and heated to 500 ℃ at a rate of 5 ℃ / min for 3 min to obtain a white anatase type titanium dioxide electron transport layer with a thickness of 230 nm.

[0093] Example 3 Unlike Example 1, the titanium dioxide amorphous precursor liquid obtained in step (2) was spin-coated onto an ITO glass plate at a speed of 4500 rpm for 35 s, and then placed in a vacuum sintering furnace and heated to 500 ℃ at a rate of 5 ℃ / min for 3 min to obtain a white anatase type titanium dioxide electron transport layer with a thickness of 250 nm.

[0094] The solar cells prepared in Examples 1-3 above were subjected to photoelectric conversion efficiency (PCE), open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF). The measurement results are shown in Table 1.

[0095] Table 1. Performance of solar cells prepared in Examples 1-3

[0096] As shown in Table 1, the electron transport layer prepared using the method of this application results in a solar cell with high photoelectric conversion efficiency.

[0097] By changing the sintering temperature in the vacuum sintering furnace in step (4) of Example 1, the crystallization of the titanium dioxide amorphous precursor liquid prepared in this application was observed. Figure 7 The crystallization of titanium dioxide in step (4) of the vacuum sintering furnace at sintering temperatures of 25℃, 50℃, 100℃, 200℃, 300℃, 400℃, and 500℃ is shown. Figure 7 It is known that the amorphous titanium dioxide prepared by the method of this application begins to crystallize at 200℃ and exhibits the characteristic peaks of anatase titanium dioxide until it is fully crystallized at 400℃~500℃. Therefore, this application can achieve the crystallization of titanium dioxide over a wide range of heat treatment temperatures, and different heat treatment temperatures can be selected according to the chosen substrate type, all of which can be used to prepare titanium dioxide electron transport layers over a large area.

[0098] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a solar cell, characterized in that, Includes the following steps: Provide a base; Chalcogenides of titanium were prepared by solid-phase synthesis. The mixture of the titanium chalcogenide and the oxidant was ultrasonically treated to obtain an amorphous titanium dioxide precursor solution. The amorphous titanium dioxide precursor liquid is coated on the surface of the substrate and subjected to a first heat treatment to obtain an electron transport layer. A perovskite layer is formed on the surface of the electron transport layer; A hole transport layer is formed on the surface of the titanium dioxide light-absorbing layer; An electrode layer is formed on the surface of the hole transport layer.

2. The preparation method according to claim 1, characterized in that, The chalcogenides used to prepare titanium by solid-state synthesis include: Titanium and chalcogenide elements in a molar ratio of 1:(2.0~2.2) are mixed and then subjected to a second heat treatment.

3. The preparation method according to claim 2, characterized in that, Prior to the second heat treatment, the process further includes a step of ball milling the mixture of the titanium and chalcogenides.

4. The preparation method according to claim 2, characterized in that, The chalcogenides include at least one of elemental sulfur, elemental selenium, and elemental tellurium.

5. The preparation method according to claim 2, characterized in that, The temperature of the second heat treatment is 700℃~1200℃, the heating rate of the second heat treatment is 1℃ / min~10℃ / min, and the holding time of the second heat treatment is 20h~48h.

6. The preparation method according to claim 1, characterized in that, The ultrasonic treatment of the mixture of the titanium chalcogenide and oxidant includes: A premix is ​​obtained by mixing a chalcogenide of titanium with a solution containing an oxidant, and the premix is ​​subjected to ultrasonic treatment in an oxygen atmosphere. The ultrasonic treatment is followed by a centrifugation step.

7. The preparation method according to claim 6, characterized in that, The ultrasonic treatment power is 500W~1000W, and the ultrasonic treatment time is 1min~3min; The oxidant includes hydrogen peroxide; The solvent of the solution containing the oxidant includes at least one of deionized water and ethanol; The mass ratio of the titanium chalcogenide to the oxidant is 1:(5~20).

8. The preparation method according to claim 1, characterized in that, The process of ultrasonically treating the mixture of the titanium chalcogenide and oxidant further includes: The step of mixing the product obtained from the ultrasonic treatment with a hydrolysate, wherein the hydrolysate comprises at least one of deionized water and an alcohol compound.

9. The preparation method according to claim 1, characterized in that, The coating includes spin coating, the coating rotation speed is 3000rpm~6000rpm, and the coating time is 10s~50s; The temperature of the first heat treatment is greater than or equal to 200℃, the time of the first heat treatment is 1 min to 3 min, and the heating rate of the first heat treatment is 1℃ / min to 10℃ / min.

10. A solar cell, characterized in that, The solar cell includes: a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer. The electron transport layer is located between the substrate and the perovskite layer, and the hole transport layer is located between the perovskite layer and the electrode layer. The electron transport layer includes a plurality of titanium dioxide crystals, which are stacked to form a dendritic structure.

11. The solar cell according to claim 10, characterized in that, The thickness of the electron transport layer is 100nm~300nm.

12. The solar cell according to claim 10, characterized in that, The titanium dioxide crystals have a particle size of 100 nm to 2 μm.

13. The solar cell according to claim 10, characterized in that, The titanium dioxide crystals are rutile or anatase.

14. A stacked battery, characterized in that, include: A bottom cell, a composite layer, and a top cell are stacked sequentially along a predetermined direction; wherein the top cell is a solar cell formed by the method for preparing a solar cell as described in any one of claims 1 to 9 or a solar cell as described in any one of claims 10 to 13.

15. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string, wherein the battery string is formed by connecting a plurality of solar cells formed by the preparation method according to any one of claims 1 to 9 or solar cells according to any one of claims 10 to 13; An encapsulation layer that covers the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

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