Method for the production of a grid line for a photovoltaic electrode, photovoltaic cell

Abstract

The application discloses a PVP fiber film and a photovoltaic electrode grid line preparation method and a photovoltaic cell, and relates to the technical field of photovoltaic cells. The method adopts electrostatic spinning technology to prepare a PVP fiber film, and then realizes precise electrode design on a crystalline silicon wafer through high-precision compression molding, transfer printing and dissolution processes on the PVP film. The high-precision compression molding technology and the transfer printing technology are applied to the preparation of the photovoltaic electrode grid line, so that the precision and resolution of the electrode grid line can be greatly improved. Excellent electrode quality, simplified process flow and optimized electrode design can improve the photoelectric conversion efficiency of the photovoltaic cell, reduce the amount of silver paste, and reduce the industrialization cost. The PVP film with suitable thickness and hardness can be directly used as a substrate for transfer printing, instead of the complex structure of the conventional transfer substrate film plus the water-soluble polymer coating, and can also solve the problem that the subsequent substrate cannot be easily separated from the crystalline silicon wafer, thereby damaging the silicon wafer and affecting the grid line structure.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a method for preparing photovoltaic electrode grid lines and a photovoltaic cell. Background Technology

[0002] With the advancement of the national carbon peaking and carbon neutrality goals, the construction of a new power system based on new energy sources is being accelerated, significantly enhancing the status of the photovoltaic industry. Solar cells are the core component of photovoltaic systems, with monocrystalline silicon photovoltaic cells playing a crucial role in industrial production, accounting for over 90% of total solar cell production. Electrode grids are a key component of the cell, significantly impacting its performance. Electrode grid materials are primarily those with good conductivity; silver paste is one of the most widely used electrode grid materials, possessing excellent conductivity and chemical stability, making it suitable for photovoltaic cell fabrication. Optimizing the silver paste grid fabrication process can effectively improve the photoelectric conversion efficiency of solar cells.

[0003] Silver paste grid line printing technology is one of the key manufacturing processes for photovoltaic cells. It is mainly used to form electrodes on silicon wafers to collect the current generated by the photovoltaic effect. Common electrode grid line printing technologies include screen printing, inkjet printing, offset printing, and flexographic printing. Screen printing technology is the most commonly used. This technology uses a screen to print silver paste onto the surface of the photovoltaic cell to form electrode patterns, thereby realizing the collection and conduction of electrical energy.

[0004] Although screen printing technology is commonly used, it still has some shortcomings compared to silver transfer technology. For example, silver transfer technology has advantages such as higher resolution, more stable finished product quality, higher production efficiency, wider applicability, and stronger durability.

[0005] However, in transfer printing technology, the flexibility of the transfer substrate film is insufficient for the application requirements. This results in several issues: some substrate films are too soft, causing deformation after the subsequent silver paste is filled in; some substrate films are too hard, becoming too brittle and unusable; and some substrates fail to detach from the silicon wafer automatically, affecting the silver paste application. Currently, no effective solutions have been proposed to address these problems. Summary of the Invention

[0006] Objective of the invention: To provide a method for preparing photovoltaic electrode grid lines and a photovoltaic cell, so as to at least solve one of the problems existing in the prior art.

[0007] Technical solution: A method for preparing PVP fiber films, comprising the following steps: S11. Dissolve PVP in a pre-set solvent to prepare a uniform spinning solution; S12. Place the spinning solution in a syringe and spin it using an electrostatic spinning device; S13. During the spinning process, the fibers will form a film on the collecting device. The collected fiber film is then processed to finally obtain the desired PVP fiber film.

[0008] Preferably, in step S11, PVP is dissolved in a pre-set solvent to prepare a uniform spinning solution, including: PVP and tetrabutyl titanate were dissolved in a mixed solvent of ethanol and acetic acid to prepare precursor solutions with mass fractions of 3-5% PVP and 18-22% tetrabutyl titanate.

[0009] Preferably, S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, further includes: PVP and diphenylalanine were slowly added to a mixed solvent of methanol and N,N-dimethylacetamide while stirring, and stirring was continued until completely dissolved to obtain a transparent polymer solution.

[0010] Preferably, S12 involves placing the spinning solution in a syringe and spinning it using an electrospinning device, including: The prepared spinning solution is placed in a syringe with a preset inner diameter, and electrospinning is performed using a preset working voltage intensity.

[0011] To achieve the above objectives, according to another aspect of this application, a method for preparing photovoltaic electrode grid lines is also provided.

[0012] The photovoltaic electrode grid line fabrication method according to this application includes the following steps: S1. Provide a PVP fiber film prepared by the above preparation method; S2. Using a mold, heat-press the grooves of the electrode pattern onto the PVP fiber film to form a groove. S3. Apply silver paste to the hot-pressed side of the PVP fiber film, enough to fill the grooves thereon, and remove excess silver paste from the surface of the PVP fiber film so that the grooves and the surface of the silver paste are on the same plane. S4. Provide a substrate, attach the side of the PVP fiber film with silver paste to the substrate, and transfer the silver paste onto the substrate by imprinting using preset process parameters. At the same time, the silver paste is dried to enhance the adhesion between the substrate and the silver paste, forming a stable, continuous grid structure with excellent conductivity. The imprinting process parameters are: pressure of 5-20 MPa, temperature of 80-180℃, and time of 1-10 min. S5. Remove the PVP fiber film to allow the silver paste to remain on the substrate; S6. Sinter the silver paste onto the substrate to form silver paste electrode grid lines with a preset aspect ratio.

[0013] Preferably, S1 provides a PVP fiber film, comprising: PVP fiber films with a thickness of 35-85 μm can be prepared by electrospinning or flat plate coating.

[0014] Preferably, S2, the grooves for forming the electrode pattern on the PVP fiber film by hot pressing with a mold, include: The prepared PVP fiber film is placed in a mold using a precision hot press and hot-pressed at 100-125℃ to form a micron- or even nano-scale electrode groove structure on the surface of the PVP fiber film.

[0015] Preferably, in S2, the mold is one of a single-crystal silicon substrate, a polycrystalline silicon substrate, a copper substrate, a nickel substrate, a copper-nickel alloy substrate, a nickel-iron alloy substrate, an iron-aluminum alloy substrate, or an aluminum alloy substrate.

[0016] Preferably, in S2, the shape of the protrusion of the mold is complementary to the shape of the groove; The shape of the mold is one of the following: isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid, or rectangle.

[0017] Preferably, in S2, the aspect ratio of the mold shape is in the range of 1-3.

[0018] Preferably, step S3 involves coating the hot-pressed side of the PVP fiber film with silver paste sufficient to fill the grooves thereon, and removing excess silver paste from the surface of the PVP fiber film so that the grooves and the surface of the silver paste are on the same plane, including: Silver paste is uniformly applied to the thermo-pressed PVP fiber film using a flat plate coating method, ensuring that the silver paste completely fills the grooves. Excess silver paste is then scraped off to guarantee that the silver paste is completely and evenly distributed without deformation.

[0019] Preferably, S4, a substrate is provided, and the side of the PVP fiber film having silver paste is bonded to the substrate, including: Silver paste is hot-pressed onto a substrate by applying uniform pressure and heating and drying, while simultaneously heating and drying the silver paste to ensure it adheres tightly to the substrate surface without deformation; wherein the substrate is one of crystalline silicon wafers, glass, perovskite, metal or polymer substrates.

[0020] Preferably, step S5, removing the PVP fiber film to leave the silver paste on the substrate, includes: The transferred silicon wafer is then rinsed in water at 25-75℃ to dissolve and remove the PVP film, leaving behind the successfully transferred silver paste pattern, which forms the basic structure of the photovoltaic electrode grid lines.

[0021] Preferably, step S6 involves sintering silver paste onto a substrate to form silver paste electrode grid lines with a predetermined aspect ratio, including: The silicon wafer after silver paste transfer is placed in a high-temperature furnace to sinter the silver paste. The sintering temperature is 500-800℃ to ensure that the silver paste is completely sintered and forms a tight bond with the silicon wafer, generating high-precision photovoltaic silver paste electrode grid lines with a preset aspect ratio.

[0022] To achieve the above objectives, according to another aspect of this application, a photovoltaic cell is also provided.

[0023] The photovoltaic cell according to this application includes fabricated photovoltaic electrode grid lines.

[0024] Beneficial Effects: In this embodiment, PVP fiber films are prepared by electrospinning. The process involves: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution; S12, placing the spinning solution in a syringe and spinning it using an electrospinning device; and S13, during the spinning process, the fibers form a film on a collection device. The collected fiber film undergoes post-processing to obtain the desired PVP fiber film, achieving the goal of obtaining the desired PVP fiber film. This achieves the technical effect of the substrate film possessing good flexibility and easy detachment, thus solving the technical problems in transfer printing technology where the transfer substrate film's flexibility is insufficient, resulting in some substrate films being too soft and deforming after subsequent silver paste filling; some substrate films being too hard and brittle, rendering them unusable; and the substrate failing to automatically detach from the silicon wafer, thus affecting the silver paste. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of the photovoltaic electrode grid line fabrication method of the present invention; Figure 2 This is a schematic flowchart of another photovoltaic electrode grid line fabrication method of the present invention; Figure 3 This is a schematic flowchart of the PVP fiber film preparation method of the present invention; and Figure 4 This is a schematic diagram of the mold structure in the photovoltaic electrode grid line preparation method of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] like Figure 1-3 As shown, this application relates to a method for fabricating photovoltaic electrode grid lines and a photovoltaic cell. Figure 1-2 As shown, the method for fabricating a photovoltaic electrode grid line includes the following steps: S1. Provide a PVP fiber film prepared by a PVP fiber film preparation method; It can achieve the desired PVP fiber film effect, thus providing a guarantee for subsequent processes.

[0031] It is important to know that PVP stands for polyvinylpyrrolidone. As a non-ionic polymer, it has good water solubility, biocompatibility, and film-forming properties.

[0032] Based on a deep understanding of photovoltaic silver paste and research on the water solubility of polyvinylpyrrolidone (PVP) materials, this invention found that PVP has no reactivity with silver paste binders and solvents and has weak adhesion, making it an ideal carrier for transfer silver paste.

[0033] PVP, as a synthetic water-soluble polymer, possesses the general properties of water-soluble polymers, including colloidal protection, film-forming properties, adhesiveness, hygroscopicity, solubilization, and coagulation. However, its most distinctive and therefore highly valued characteristic is its excellent solubility and physiological compatibility. Among synthetic polymers, PVP is rare due to its high solubility in water and most organic solvents, low toxicity, and excellent physiological compatibility, especially in fields closely related to human health such as pharmaceuticals, food, and cosmetics.

[0034] According to an embodiment of the present invention, preferably, S1, providing a PVP fiber film, comprising: PVP fiber films with a thickness of 35-85 μm can be prepared by electrospinning or flat plate coating.

[0035] Specifically, electrospinning is a technique that uses electrostatic force to stretch a polymer solution into nano- or micro-sized fibers, which is used to prepare polymer film.

[0036] By employing electrospinning or flatbed coating methods, PVP fiber films with a thickness of 35-85 μm can be prepared, ensuring good performance requirements and thus achieving good synergistic effects.

[0037] Of course, those skilled in the art should be familiar with the process when using the plate coating method.

[0038] S2. Use a mold to heat-press grooves of electrode patterns onto a PVP fiber film; The desired electrode pattern can be obtained through hot pressing, thereby improving accuracy and facilitating implementation.

[0039] According to an embodiment of the present invention, preferably, step S2, which involves using a mold to thermo-imprint grooves for electrode patterns onto a PVP fiber film, includes: The prepared PVP fiber film is placed in a mold using a precision hot press and hot-pressed at 100-125℃ to form a micron- or even nano-scale electrode groove structure on the surface of the PVP fiber film. By using a hot press molding machine, the precision of the PVP transfer coating after hot pressing can be guaranteed, and the size and shape of the grid lines can be reasonably designed to reduce ohmic loss.

[0040] According to an embodiment of the present invention, preferably, in S2, the mold is one of a single-crystal silicon substrate, a polycrystalline silicon substrate, a copper substrate, a nickel substrate, a copper-nickel alloy substrate, a nickel-iron alloy substrate, an iron-aluminum alloy substrate, or an aluminum alloy substrate.

[0041] It can achieve the effect of having a variety of materials to choose from, thus achieving a flexible use effect and an easy-to-achieve effect.

[0042] It is important to know that monocrystalline silicon substrates have excellent electrical conductivity and thermal stability, and are often used in the manufacture of high-efficiency photovoltaic cells. Polycrystalline silicon substrates: relatively low cost, high mechanical strength and stability, and widely used in the photovoltaic field; Copper substrate: It has good electrical and thermal conductivity, making it suitable for applications requiring rapid electrical conductivity; Nickel-based substrate: It has excellent corrosion resistance and mechanical strength, making it suitable for manufacturing electrodes for long-term use; Copper-nickel alloy substrate: combines the electrical conductivity of copper and the corrosion resistance of nickel, making it suitable for high-requirement electrical equipment; Nickel-iron alloy substrate: It is magnetic and corrosion resistant, and is often used in the manufacture of electromagnetic devices; Iron-aluminum alloy substrate: lightweight, high temperature resistant and corrosion resistant, suitable for electrode applications in aerospace and high temperature environments; Aluminum alloy substrate: lightweight and with good thermal conductivity, it is widely used in photovoltaic cell frames and electrical conductors.

[0043] like Figure 4 As shown in the embodiment of the present invention, preferably, in S2, the shape of the protrusion of the mold is complementary to the shape of the groove; The protrusion of the mold is shaped as an isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid, or rectangle. The shape and size of the protrusion correspond to the electrode grid lines. In actual operation, the size and shape of the electrode grid lines to be transferred are controlled to reduce the ohmic loss of the electrode grid lines. The longitudinal cross-sectional shape of the protrusion includes, but is not limited to, a triangle, trapezoid, rectangle, rhombus, semicircle, or polygon. In this embodiment, preferably, the longitudinal cross-sectional shape of the protrusion is a triangle or trapezoid. The triangular or trapezoidal longitudinal cross-sectional design helps to change the incident and refraction path of light, better captures and guides light, effectively reduces light reflection loss, and allows more light to be absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0044] By designing the shapes of the protrusions and grooves of the mold as complementary structures, precise alignment and imprinting effects can be ensured during the mold forming process, thereby achieving high-precision transfer effects and improving the quality of the electrode grid lines in the final product.

[0045] Specifically, the shape of the mold can be selected from the following geometric structures: Isosceles triangle: Suitable for scenarios requiring concentrated force transmission, it can create a sharp and clear transfer effect at the edges of photovoltaic electrode grid lines.

[0046] Isosceles trapezoid: With a larger bottom width and a narrower top structure, it is suitable for applications that require gradually wide electrode grid lines, ensuring uniform filling during the transfer process.

[0047] Elliptical shape: It can provide a smooth edge transition effect, which is suitable for electrode designs that require a more uniform current distribution, reducing resistance and local stress concentration.

[0048] Hexagonal: Stable structure with good density distribution, suitable for electrode grid line designs that require improved transfer accuracy and stability.

[0049] Right-angled trapezoid: Suitable for photovoltaic electrode designs that require uniform grid line width and neat edges, ensuring accurate current distribution.

[0050] Rectangular: A classic and common design, suitable for transferring standardized photovoltaic electrode grid lines, providing the largest contact area to improve current conduction efficiency.

[0051] According to an embodiment of the present invention, preferably, in S2, the aspect ratio of the mold shape is in the range of 1-3.

[0052] By setting the aspect ratio of the mold shape to a range of 1-3, the relationship between the height and width of the mold protrusion can be effectively adjusted, thereby optimizing the transfer effect of the electrode grid lines.

[0053] Specifically, when the aspect ratio is 1, the height and width of the mold are equal, which is suitable for electrode structures that require relatively flat grid lines with uniform thickness and width. This ensures that the electrodes have good conductivity and that the silver paste can be evenly distributed during the transfer process.

[0054] In this embodiment, preferably, when the aspect ratio is close to 2, a suitable thickness and width are provided, so that the grid lines have a certain height to improve the mechanical strength of the electrode, without being too wide to maintain a fine structure. This is suitable for conventional photovoltaic electrode manufacturing, balancing resistance, strength, and manufacturing difficulty.

[0055] When the aspect ratio is 3, the height of the grid line is significantly greater than its width, which is suitable for narrow electrode designs that require more precision. It can effectively reduce resistance and increase current density, but requires high mold precision during manufacturing to ensure that the silver paste is fully filled in the narrow groove.

[0056] Therefore, the flexible setting of the aspect ratio range allows for the adjustment of the electrode grid geometry according to different photovoltaic cell design requirements, in order to achieve the best balance between conductivity, mechanical strength and manufacturing process.

[0057] S3. Apply silver paste to the hot-pressed side of the PVP fiber film, enough to fill the grooves thereon, and remove excess silver paste from the surface of the PVP fiber film so that the grooves and the surface of the silver paste are on the same plane. It can achieve a good silver paste coating effect, making it evenly distributed on the PVP fiber film.

[0058] According to an embodiment of the present invention, preferably, step S3, applying silver paste to the hot-pressed side of the PVP fiber film to at least fill the grooves thereon, and removing excess silver paste from the surface of the PVP fiber film so that the grooves and the surface of the silver paste are on the same plane, includes: Using a flatbed coating method to uniformly apply silver paste to a PVP fiber film that has been precisely embossed, it is possible to ensure that the silver paste is tightly filled into the grooves of the PVP fiber film. At the same time, excess silver paste on the surface is scraped off, thereby ensuring that the silver paste is completely and evenly distributed without deformation.

[0059] It is important to know that one of the main components of photovoltaic silver paste is a binder (phenolic resin, epoxy resin, etc.), which is used to form a stable bond between the silver paste particles and between the particles and the silicon wafer.

[0060] S4. Provide a substrate, attach the side of the PVP fiber film with silver paste to the substrate, and transfer the silver paste onto the substrate by imprinting using preset process parameters; wherein, the imprinting process parameters are: pressure of 5-20MPa, temperature of 80-180℃, and time of 1-10min. According to an embodiment of the present invention, more preferably, step S4, bonding the side of the PVP fiber film having the silver paste to the substrate, includes: Silver paste is hot-pressed onto a substrate by applying uniform pressure and heating and drying, while simultaneously heating and drying the silver paste to ensure it adheres tightly to the substrate surface without deformation; wherein the substrate is one of crystalline silicon wafers, glass, metal or polymer substrates.

[0061] By applying uniform pressure to the uncoated side of the PVP fiber film and heating it to dry, the photovoltaic silver paste can be transferred onto the silicon wafer due to the adhesion between the photovoltaic silver paste and the silicon wafer. The silver paste can adhere tightly to the silicon wafer, thus ensuring a good transfer effect and thereby ensuring the stability of the silver paste structure.

[0062] S5. Remove the PVP fiber film to allow the silver paste transfer to remain on the substrate; According to an embodiment of the present invention, preferably, step S5, removing the PVP fiber film to leave the silver paste on the substrate, includes: The transferred silicon wafer is then rinsed in water at 25-75℃ to dissolve and remove the PVP film, leaving behind the successfully transferred silver paste pattern, which forms the basic structure of the photovoltaic electrode grid lines.

[0063] It can dissolve and remove the PVP film, thus preserving the silver paste pattern completely on the silicon wafer, thereby achieving a good dissolution and separation effect.

[0064] It is important to know that the water solubility of PVP can be altered by changing its molecular weight and through blending modifications, allowing it to dissolve rapidly in water.

[0065] S6. Sinter the silver paste onto the substrate to form silver paste electrode grid lines with a preset aspect ratio.

[0066] According to an embodiment of the present invention, preferably, step S6, sintering silver paste onto a substrate to form silver paste electrode grid lines with a predetermined aspect ratio, includes: The silicon wafer after silver paste transfer is placed in a high-temperature furnace to sinter the silver paste. The sintering temperature is 500-800℃ to ensure that the silver paste is completely sintered and forms a tight bond with the silicon wafer, generating high-precision photovoltaic silver paste electrode grid lines with a preset aspect ratio.

[0067] After being sintered at high temperature, the silver paste can form silver paste electrode grid lines of the required depth and width. Preferably, the silver paste electrode grid lines are 10 μm deep and 5 μm wide.

[0068] This application uses a precision hot press to control the size and shape of the PVP transfer electrode grid lines, thereby reducing the ohmic loss of the electrode grid lines. The triangular prism-shaped silver paste grid lines have better conductivity than the cuboid-shaped silver paste grid lines, and more light incident on the sides of the triangle can be refracted into the solar panel and fully utilized. PVP, as a biodegradable and environmentally friendly material, has low environmental harm, and the room-temperature water-soluble PVP coating can greatly reduce demolding costs. The method is simple, and the materials and equipment involved are economical and environmentally friendly, resulting in low process costs.

[0069] This application also has the following beneficial effects: 1. Improved adhesion of transfer silver paste: By using polyvinylpyrrolidone (PVP) as an ideal carrier, this invention achieves stronger adhesion between silver paste and silicon wafer; the water solubility and biocompatibility of the PVP coating enable the silver paste to fill the grooves more tightly during the transfer process, thereby ensuring a firm bond between the silver paste and the silicon wafer.

[0070] Specifically, select a suitable carrier material: PVP, as a water-soluble, biocompatible, and film-forming polymer compound, has good adhesion and can serve as an ideal carrier for silver transfer paste, ensuring a firm bond between the silver paste and the silicon wafer.

[0071] 2. Improve the precision and stability of electrode patterns: By preparing 35-85um PVP fiber films through electrospinning and pressing micron- or even nano-scale electrode patterns in a precision hot press, this invention achieves high precision and stability of electrode patterns, which helps to improve the performance and efficiency of photovoltaic cells.

[0072] 3. Simplified production process: By using a flat plate coating method to apply silver paste to the PVP coating after hot pressing and then transferring it onto the silicon wafer, this invention simplifies the production process, reduces production costs and time, and improves production efficiency.

[0073] Specifically, silver paste was applied using a flat plate coating method and transferred onto a silicon wafer. The PVP coating was then dissolved and removed by water washing at a suitable temperature, ultimately forming a micron-level electrode grid line with a depth of 10µm and a width of 5µm, thus achieving successful transfer and sintering of the silver paste.

[0074] As can be seen from the above description, this application achieves the following technical effects: In this embodiment, a PVP-based method is adopted, comprising: S1. Preparing a PVP fiber film of a predetermined thickness; S2. Using a mold to precisely imprint grooves for forming electrode patterns onto the PVP fiber film; S3. Coating a silver paste sufficient to fill the grooves on the hot-pressed side of the PVP fiber film, and removing excess silver paste from the surface of the PVP fiber film so that the grooves and the surface of the silver paste are on the same plane; S4. Laying the silver paste side of the PVP fiber film to a substrate, and transferring the silver paste to the substrate through an imprinting method with predetermined process parameters; wherein the imprinting process parameters are: pressure of 5-20 MPa, temperature of 80-180℃, and time of 1-10 min; S5. Removing the PVP fiber film to leave the silver paste on the substrate; 6. Sintering silver paste onto the substrate forms silver paste electrode grid lines with a preset aspect ratio, which improves the adhesion of the transferred silver paste. This ensures a firm bond between the silver paste and the silicon wafer, improves the accuracy and stability of the electrode pattern, and reduces production costs and efficiency. It also solves the technical problems of screen printing, where precision is limited by screen aperture and printing pressure, making it difficult to achieve very fine patterns and high-resolution printing (typically, silver paste linewidths are at least tens of micrometers). Furthermore, screen printing generates a certain amount of waste, leading to material waste; screen plugs have limited lifespan and are expensive, resulting in high overall costs; and screen printing is a relatively slow production process, unable to meet the needs of large-scale production, thus affecting production efficiency.

[0075] Compared to screen printing, silver transfer printing technology has the following advantages: 1. Higher resolution: Transfer silver paste technology can usually achieve higher resolution because it can accurately transfer silver paste on smaller sizes, thus achieving finer patterns and lines.

[0076] 2. More stable finished product quality: Since the silver paste transfer technology can be carried out in a controlled environment, more stable and consistent finished product quality can be obtained, avoiding problems such as uneven ink flow that may occur in screen printing.

[0077] 3. Higher production efficiency: Transfer silver paste technology can usually achieve automated production, improve production efficiency, reduce manual operation, and save time and costs.

[0078] 4. Wider applicability: Transfer silver paste technology can be applied to various substrates and materials, including flexible substrates and non-flat surfaces, thus having a wider range of applicability.

[0079] 5. Enhanced durability: Transfer silver paste technology typically achieves better adhesion and durability, making printed patterns more durable and stable, and less susceptible to external environmental influences.

[0080] like Figure 3 As shown, this application also relates to a method for preparing a PVP fiber film, comprising the following steps: S11. Dissolve PVP in a pre-set solvent to prepare a uniform spinning solution; It enables the preparation of a uniform spinning solution.

[0081] According to an embodiment of the present invention, preferably, step S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, includes: PVP and tetrabutyl titanate were dissolved in a mixed solvent of ethanol and acetic acid to prepare precursor solutions with mass fractions of 3-5% PVP and 18-22% tetrabutyl titanate.

[0082] According to an embodiment of the present invention, more preferably, PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with mass fractions of 4% PVP and 20% tetrabutyl titanate.

[0083] According to an embodiment of the present invention, preferably, step S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, further includes: PVP and diphenylalanine were slowly added to a mixed solvent of methanol and N,N-dimethylacetamide while stirring, and stirring was continued until completely dissolved to obtain a transparent polymer solution.

[0084] Specifically, in order to obtain a suitable PVP fiber film, it is first necessary to prepare a uniform spinning solution. The key to this process is to select appropriate solvents and precursors to ensure that the spinning solution has suitable viscosity and uniformity, which is conducive to the formation of stable fibers by electrospinning.

[0085] Of course, this application provides a variety of solution preparation schemes, which can be selected according to actual needs, thereby achieving the effect of flexible use.

[0086] S12. Place the spinning solution in a syringe and spin it using an electrostatic spinning device; According to an embodiment of the present invention, preferably, step S12, placing the spinning solution in a syringe and spinning it using an electrospinning device, includes: The prepared spinning solution is placed in a syringe with a preset inner diameter, and electrospinning is performed using a preset working voltage intensity.

[0087] Specifically, a syringe with an inner diameter of 0.43 mm is used to ensure uniform flow of spinning solution and stable fiber formation; The applicable voltage range is 1.8kV / cm, which can generate a stable electric field during the spinning process, thereby effectively stretching the spinning solution and forming fibers; During the spinning process, temperature and humidity are controlled to prevent fiber breakage or excessive stretching, ensuring fiber stability and morphological consistency.

[0088] Of course, specific parameter settings can be configured according to actual usage requirements, and are not limited in this application.

[0089] S13. During the spinning process, the fibers will form a film on the collecting device. The collected fiber film is then processed to finally obtain the desired PVP fiber film.

[0090] As can be seen from the above description, this application achieves the following technical effects: In this embodiment, PVP fiber films are prepared by electrospinning. The process involves: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution; S12, placing the spinning solution in a syringe and spinning using an electrospinning device; and S13, during the spinning process, the fibers form a film on a collection device. The collected fiber film undergoes post-processing to obtain the desired PVP fiber film, achieving the goal of obtaining the desired PVP fiber film. This achieves the technical effect of the substrate film having good flexibility and easy detachment, thus solving the technical problems in transfer printing technology where the transfer substrate film's flexibility is insufficient, resulting in some substrate films being too soft and deforming after subsequent silver paste filling; some substrate films being too hard and brittle, making them unusable; and the substrate failing to automatically detach from the silicon wafer, thus affecting the silver paste.

[0091] The following examples further illustrate this point: Example 1 like Figure 1 As shown, I. Solution preparation: PVP and tetrabutyl titanate were dissolved in a mixed solvent of ethanol and acetic acid to prepare precursor solutions with mass fractions of 4% PVP and 20% tetrabutyl titanate. II. Electrospinning: Using a working voltage of 1.8kV / cm, an inner diameter of 0.43mm for the syringe, a flow rate of 0.5mL / h for the spinning solution, a temperature of 25℃, and a humidity of 45%, a PVP fiber film with a thickness of 50μm is formed by spinning. III. High-precision embossing: At 130℃, a precision hot press is used to hot press the fiber film using a mold, applying a pressure of 20MPa to form micron- or nano-scale groove patterns on the surface of the fiber film. IV. Silver paste coating and transfer: Using the flat plate coating method, the silver paste is evenly coated on the surface of the PVP film, and after scraping off the excess silver paste, it is transferred to the surface of the silicon wafer. 5. PVP Removal: Wash in 50℃ water for 5 minutes to completely dissolve and remove the PVP film; 6. Silver paste sintering: The transferred silicon wafer is sintered at 700℃ for 1 minute to form silver paste electrode grid lines.

[0092] At this point, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier are as follows: the depth of the silver paste electrode grid line is 10μm and the width is 5μm. The silver paste is tightly bonded to the silicon wafer, has excellent conductivity, and the resistivity is as low as 1.3μΩ·cm, making it suitable for high-efficiency photovoltaic cell applications.

[0093] Example 2 The difference between Example 2 and Example 1 is as follows: 1. Solution preparation: PVP and diphenylalanine are dissolved in a mixed solvent of methanol and N,N-dimethylacetamide at a mass fraction of 4% and 10% respectively to form a homogeneous polymer solution. II. Electrospinning: Using the same electrospinning conditions, a PVP fiber film with a thickness of 65μm was spun. III. High-precision hot pressing: Applying 15MPa pressure at 110℃, hot pressing is used to form micron-level grooves; IV. Silver paste coating and transfer: Apply and transfer silver paste using the same method; V. PVP Removal: Rinse in 60℃ water for 7 minutes to dissolve and remove PVP; VI. Silver paste sintering: Sinter at 800℃ for 30 minutes.

[0094] At this point, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier are as follows: the depth of the silver paste electrode grid line is 8μm, the width is 6μm, the resistivity is 1.4μΩ·cm, and the silver paste transfer quality is good.

[0095] Example 3 The difference between Example 3 and Example 1 is that, firstly, the solution preparation: the same PVP and tetrabutyl titanate solution as in Example 1 is used; II. Electrospinning: By increasing the spinning solution flow rate to 1 mL / h, a PVP fiber film with a thickness of 85 μm is formed; III. High-precision hot pressing molding: forming micron-level grooves by hot pressing at 125℃ and 25MPa; IV. Silver paste coating and transfer: Apply and transfer silver paste using the same method; V. PVP Removal: Rinse in 55℃ water for 8 minutes to dissolve and remove PVP; VI. Silver paste sintering: Sinter at 700℃ for 1 minute.

[0096] At this point, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier are as follows: the depth of the silver paste electrode grid line is 12μm and the width is 7μm. The conductivity is comparable to that of the aforementioned embodiment. However, due to the thickness of the PVP film, the silver paste transfer is uneven in some areas, resulting in a slight decrease in conductivity.

[0097] Example 4 The difference between Example 4 and Example 1 is as follows: 1. Preparation of PVA solution: Weigh 8g of PVA powder and dissolve it in 92mL of distilled water to form an 8% PVA solution; stir at 80°C for 1 hour until the PVA is completely dissolved and a homogeneous solution is formed. II. Electrospinning equipment setup: Inject the PVA solution into a syringe with an inner diameter of 0.43 mm; set the high voltage power supply to 15 kV, and maintain the distance between the collecting plate and the syringe needle at 12 cm; III. Spinning process: Under the action of an electric field, the PVA solution is sprayed through the syringe needle to form nanofibers, which are then deposited on a rotating collecting plate; spinning continues for 30 minutes until a uniform fiber network film is formed on the collecting plate; IV. Drying and Post-treatment: After spinning, the film is dried in a drying oven at 40℃ for 12 hours to remove moisture and stabilize the film.

[0098] At this time, the test results of the photovoltaic electrode grid line transfer method based on PVA carrier are as follows: the PVA film prepared by electrospinning has a nanoscale fiber structure with a fiber diameter of 150-300nm and a porous structure; the film has high porosity and is suitable for gas filtration and biomedical materials; the tensile strength of the fiber film is 20MPa and the elongation at break is 50%.

[0099] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the traditional PVP coating process did not employ electrospinning. 1. PVP Coating: Using the traditional coating method, the PVP solution is directly coated onto the silicon wafer to a thickness of 40μm; II. Hot pressing: Apply 10MPa pressure at 100℃ to hot press and form the electrode groove; III. Silver paste coating and transfer: Apply and transfer silver paste using the same method; IV. PVP Removal: Rinse in 30℃ water for 3 minutes; 5. Silver paste sintering: Sinter at 700℃ for 1 minute.

[0100] At this point, the test results for the photovoltaic electrode grid line transfer method based on PVP carrier were as follows: the depth of the silver paste electrode grid lines was 6 μm, the width was 10 μm, and the resistivity was 2.1 μΩ·cm. Due to the poor uniformity of the PVP coating and the poor filling effect of the silver paste, the electrode line width was uneven, the conductivity was poor, and it could not meet the high precision requirements of photovoltaic cells.

[0101] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that, firstly, electrospinning: PVP films were prepared using the spinning conditions of Example 1; II. Hot pressing: Hot pressing is performed at 90℃ and 10MPa; III. Silver paste coating and transfer: Apply and transfer silver paste using the same method; IV. PVP removal: Rinse in 40℃ water for 4 minutes; 5. Silver paste sintering: Sinter at 700℃ for 1 minute.

[0102] At this point, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier were as follows: due to the low hot pressing temperature, the PVP fiber was not fully compacted, the silver paste electrode groove was not clearly formed, and the final electrode grid line depth was 4μm, the width was 12μm, the resistivity was 2.4μΩ·cm, the conductivity was significantly reduced, and it could not meet the application requirements.

[0103] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that PEG is used as the base material.

[0104] At this point, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier are as follows: due to the different interface characteristics between PEG and silver paste, the adhesion during the transfer process is poor, resulting in the silver paste not being completely transferred to the silicon wafer; the morphology of the electrode grid lines is not as clear as that of the PVP substrate, with irregular edges and silver paste falling off; the conductivity of the silver paste electrode grid lines is low, and the silver paste in some areas is not effectively transferred.

[0105] The test results above show that: 1. As can be seen from Examples 1 and 2, both can achieve high-precision silver paste electrode grid lines with good conductivity, flexibility, water solubility and bonding strength, especially Example 1, which shows the best performance.

[0106] 2. As can be seen from Example 3, although the electrode depth is increased due to the increase in the thickness of the PVP film, there is an unevenness problem during the transfer process, which affects the conductivity.

[0107] 3. As can be seen from Example 1 and Comparative Example 1, traditional PVP coating and low-temperature hot pressing conditions cannot form an ideal electrode structure, resulting in poor quality of silver paste grid lines and insufficient conductivity.

[0108] 4. As can be seen from Example 1 and Comparative Example 2, if the hot pressing temperature is too low, the PVP fiber will not be fully compacted, resulting in unclear formation of the silver paste electrode groove, which in turn affects the conductivity.

[0109] 5. As can be seen from Example 1 and Comparative Example 3, using PEG as a substrate material results in poor adhesion, electrode morphology, and conductivity.

[0110] 6. As can be seen from Examples 1 and 4, fiber films prepared using PVP and PVA can achieve high-precision silver paste electrode grid lines and have good conductivity, flexibility, water solubility and bonding strength.

[0111] This application also relates to a photovoltaic cell, including the photovoltaic electrode grid lines prepared as described above. The photovoltaic cell using the photovoltaic electrode grid lines provided in this embodiment has the same basic principle and technical effects as the above embodiments. For any parts not mentioned in this embodiment, please refer to the corresponding content above.

[0112] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and all such equivalent transformations fall within the protection scope of the present invention.

Claims

1. A method for fabricating photovoltaic electrode grid lines, characterized in that, Includes the following steps: S1. Provide a PVP fiber film, wherein the PVP fiber film is prepared by the following method, including the following steps: S11. Prepare a uniform spinning solution, wherein the spinning solution has any of the following compositions: (a) Dissolve PVP and tetrabutyl titanate in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a PVP mass fraction of 3%-5% and a tetrabutyl titanate mass fraction of 18%-22%; or, (b) PVP and diphenylalanine were slowly added to a mixed solvent of methanol and N,N-dimethylacetamide under stirring, and stirring was continued until completely dissolved to obtain a transparent polymer solution with a PVP mass fraction of 4% and a diphenylalanine mass fraction of 10%. S12. Place the spinning solution in a syringe and perform electrospinning under the conditions of a working electric field strength of 1.8 kV / cm, a spinning solution flow rate of 0.5 mL / h, a temperature of 25°C and a humidity of 45%. S13. Collect a PVP fiber film with a thickness of 35-85 μm on a collection device; S2. Using a mold, hot-press printing is performed on the PVP fiber film at 100-125°C to form grooves for the electrode pattern. S3. Apply silver paste to the hot-pressed side of the PVP fiber film using a flat plate coating method, so that the silver paste completely fills the groove, and scrape off the excess silver paste on the surface of the PVP fiber film, so that the surface of the silver paste in the groove is on the same plane as the surface of the PVP fiber film. S4. The side of the PVP fiber film with silver paste is bonded to the silicon wafer. The silver paste is hot-pressed onto the silicon wafer by applying uniform pressure and heating and drying. The hot-pressing pressure is 5-20 MPa, the temperature is 80-180℃, and the time is 1-10 min. S5. Place the transferred silicon wafer in water at 25-75℃ to clean it, so that the PVP in the PVP fiber film dissolves and the PVP fiber film falls off, leaving the silver paste pattern on the silicon wafer. S6. Place the silicon wafer with the silver paste pattern in a high-temperature furnace and sinter the silver paste at 500-800℃ to form photovoltaic electrode grid lines.

2. The method for fabricating photovoltaic electrode grid lines according to claim 1, characterized in that, The spinning solution has composition (a), wherein the mass fraction of PVP is 4% and the mass fraction of tetrabutyl titanate is 20%, and the thickness of the resulting PVP fiber film is 50 μm.

3. The method for preparing photovoltaic electrode grid lines according to claim 1, characterized in that, The spinning solution uses composition (b), and the resulting PVP fiber film has a thickness of 65 μm.

4. The method for preparing photovoltaic electrode grid lines according to claim 1, characterized in that, The mold is one of the following: monocrystalline silicon substrate, polycrystalline silicon substrate, copper substrate, nickel substrate, copper-nickel alloy substrate, nickel-iron alloy substrate, iron-aluminum alloy substrate, or aluminum alloy substrate.

5. The method for fabricating photovoltaic electrode grid lines according to claim 1, characterized in that, The shape of the protrusion of the mold is complementary to that of the groove. The longitudinal cross-sectional shape of the protrusion is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right trapezoid, or a rectangle, and the height-to-width ratio of the protrusion is 1-3.

6. The method for fabricating photovoltaic electrode grid lines according to claim 1, characterized in that, S1 provides a PVP fiber film with a thickness of 65 μm as described in claim 3; S2 involves hot embossing at 110°C and 15 MPa; S5 involves washing in water at 60°C for 7 min; and S6 involves sintering at 800°C for 30 min.

7. The method for fabricating photovoltaic electrode grid lines according to claim 1, characterized in that, The photovoltaic electrode grid lines formed have a depth of 10 μm and a width of 5 μm.

8. A photovoltaic cell, characterized in that, This includes photovoltaic electrode grid lines prepared by the preparation method according to any one of claims 1-7.

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