PVP (Polyvinyl Pyrrolidone) fiber film, photovoltaic electrode grid line preparation method and photovoltaic cell

Abstract

The invention discloses a PVP (Polyvinyl Pyrrolidone) fiber film, a photovoltaic electrode grid line preparation method and a photovoltaic cell, and relates to the technical field of photovoltaic cells. According to the method, a PVP fiber film is prepared by adopting an electrostatic spinning technology, and then the PVP film is subjected to high-precision impressing forming, transfer printing, dissolving and other processes, so that precise electrode design is realized on a crystal silicon wafer. The high-precision impressing technology and the transfer printing technology are applied to preparation of the photovoltaic electrode grid line, and the precision and the resolution ratio of the electrode grid line can be greatly improved. By means of excellent electrode quality, simplified technological process and optimized electrode design, the photoelectric conversion efficiency of the photovoltaic cell can be improved, the silver paste consumption is reduced, and the industrialization cost is reduced. The PVP film with proper thickness and hardness can be directly used as a substrate to complete transfer printing, a conventional complex structure of a transfer printing substrate film and a water-soluble polymer coating is replaced, and the problems that the silicon wafer is damaged and the grid line structure is influenced due to the fact that the subsequent substrate cannot be easily separated from the crystal silicon wafer can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a method for preparing a PVP fiber film and a photovoltaic electrode grid line, and a photovoltaic cell. Background Art

[0002] With the advancement of the national carbon peak and carbon neutrality goals, the work of building a new power system with new energy as the main body is being accelerated, and the status of the photovoltaic industry has been significantly improved; solar cells are the core components of photovoltaic systems, and industrial production based on single-crystal silicon photovoltaic cells occupies an important position, accounting for more than 90% of the total solar cell output; electrode grid lines are key components of batteries, and they have a great impact on the performance of solar cells; the material of electrode grid lines is mainly materials with good conductive properties, and silver paste is one of the most widely used electrode grid line materials at present, with excellent conductive properties and chemical stability, and is suitable for the preparation of photovoltaic cells; optimizing the preparation process of silver paste grid lines can effectively improve the photoelectric conversion efficiency of solar cells.

[0003] Silver paste gridline printing technology for photovoltaic cells is one of the key production processes, which is mainly used to form electrodes on silicon wafers to collect current generated by the photovoltaic effect. Common electrode gridline printing technologies mainly include: screen printing, inkjet printing, offset printing and flexible printing. Screen printing technology is the most commonly used. This technology prints silver paste on the surface of photovoltaic cells through a screen to form an electrode pattern, thereby realizing the collection and conduction of electrical energy.

[0004] Although screen printing technology is more commonly used, it still has some shortcomings compared to transfer silver paste technology; for example: transfer silver paste technology has the advantages of higher resolution, more stable finished product quality, higher production efficiency, wider applicability and greater durability.

[0005] However, in the transfer technology, the transfer base film cannot meet the use requirements due to its flexibility, so some base films are too soft, resulting in deformation after the subsequent silver paste is filled in; some base films are too hard, resulting in too brittle to be used normally; and the subsequent base cannot automatically detach from the silicon wafer, thus affecting the silver paste. There is no effective solution to the above problems. Summary of the invention

[0006] Purpose of the invention: To provide a PVP fiber film and a method for preparing a photovoltaic electrode grid line, and a photovoltaic cell, so as to at least solve one of the problems existing in the above-mentioned prior art.

[0007] Technical solution: A method for preparing a PVP fiber film, comprising the following steps: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution; S12, placing the spinning solution in a syringe, and spinning through an electrospinning device; S13. During the spinning process, the fibers will form a film on the collecting device. The collected fiber film is post-processed to finally obtain the desired PVP fiber film.

[0008] Preferably, S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, comprising: PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with mass fractions of 3-5% PVP and 18-22% tetrabutyl titanate, respectively.

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

[0010] Preferably, S12, placing the spinning solution in a syringe and spinning through an electrospinning device, comprising: 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] Preferably, S13, during the spinning process, the fiber will form a film on the collecting device, and the collected fiber film is post-processed to finally obtain the desired PVP fiber film, including: During the spinning process, the fiber will form a film on the collecting device, and the fiber film is collected to obtain a PVP fiber film to be post-processed; Silicone oil is added to modify the PVP fiber film to be post-treated simultaneously; The synchronously modified PVP fiber film is placed in a programmed temperature muffle furnace, heated to the target temperature according to a predetermined heating curve, and maintained for a preset time to calcine and selectively remove PVP, and finally obtain the desired PVP fiber film.

[0012] In order to achieve the above objective, according to another aspect of the present application, a method for preparing a photovoltaic electrode grid line is also provided.

[0013] The photovoltaic electrode grid line preparation method according to the present application comprises the following steps: S1, providing a PVP fiber film prepared by the above preparation method; S2, using a mold to hot-emboss grooves of electrode patterns on the PVP fiber film; S3, applying silver paste that can at least fill the groove on the heat-pressed molding side of the PVP fiber film, and removing excess silver paste on the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane; S4, providing a substrate, laminating the side of the PVP fiber film with the silver paste to the substrate, and transferring the silver paste to the substrate by a stamping method with preset process parameters, and drying the silver paste to strengthen the bonding force between the substrate and the silver paste, so as to form a stable and continuous grid line structure with excellent conductive performance; wherein the stamping process parameters are: pressure of 5-20MPa, temperature of 80-180°C and time of 1-10min; S5, removing the PVP fiber film so that the silver paste remains on the substrate; S6. Sintering the silver paste on the substrate to form silver paste electrode grid lines with a preset aspect ratio.

[0014] Preferably, S1, providing a PVP fiber film, comprising: The PVP fiber film with a thickness of 35-85um was prepared by electrospinning or flat coating.

[0015] Preferably, S2, using a mold to hot-press grooves of electrode patterns on the PVP fiber film, comprises: The prepared PVP fiber film is placed in a mold by a precision hot press and hot embossing is performed at 100-125°C to form a micrometer- or even nanometer-scale electrode groove structure on the surface of the PVP fiber film.

[0016] 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.

[0017] Preferably, in S2, the convex portion of the mold is complementary in shape to the concave portion; Wherein, the shape of the mold is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right-angled trapezoid or a rectangle.

[0018] Preferably, in S2, the aspect ratio of the mold shape is in the range of 1-3.

[0019] Preferably, S3, coating the hot-pressed side of the PVP fiber film with silver paste that can at least fill the groove thereon, and removing excess silver paste from the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane, comprising: The silver paste is evenly applied on the hot-pressed PVP fiber film by a flat coating method so that the silver paste completely fills the grooves, and the excess silver paste is scraped off to ensure that the silver paste is completely filled and evenly distributed without deformation.

[0020] Preferably, S4, providing a substrate, and laminating the side of the PVP fiber film having the silver paste to the substrate, comprising: The silver paste is hot-pressed and transferred to the substrate by applying uniform pressure and heating and drying, and the silver paste is heated and dried so that it fits tightly to the surface of the substrate without deformation; wherein the substrate is one of a crystalline silicon wafer, glass, perovskite, metal or polymer substrate.

[0021] Preferably, S5, removing the PVP fiber film so that the silver paste remains on the substrate, comprises: The transferred silicon wafer is placed in 25-75°C water for cleaning, so that the PVP film dissolves and falls off, leaving the successfully transferred silver paste pattern to form the basic structure of the photovoltaic electrode grid line.

[0022] Preferably, S6, sintering the silver paste on the substrate to form a silver paste electrode grid line with a preset aspect ratio, comprising: The silicon wafer after the silver paste is transferred is placed in a high-temperature furnace to sinter the silver paste; the sintering temperature is 500-800℃, ensuring that the silver paste is completely sintered and forms a tight connection with the silicon wafer to generate high-precision photovoltaic silver paste electrode grid lines with a preset aspect ratio.

[0023] In order to achieve the above objective, according to another aspect of the present application, a photovoltaic cell is provided.

[0024] The photovoltaic cell according to the present application includes the prepared photovoltaic electrode grid lines.

[0025] Beneficial effect: In the embodiment of the present application, electrospinning is adopted to prepare PVP fiber film, through S11, PVP is dissolved in a preset solvent to prepare a uniform spinning solution; S12, the spinning solution is placed in a syringe, and spinning is performed through an electrospinning device; S13, during the spinning process, the fiber will form a film on the collecting device, and the collected fiber film is subjected to post-processing to finally obtain the desired PVP fiber film, thereby achieving the purpose of obtaining the desired PVP fiber film, thereby achieving the technical effect of the base film having good flexibility and easy detachment, and further solving the problem in the transfer technology that the transfer base film cannot meet the use requirements due to its flexibility, so that some base films are too soft, resulting in deformation after the subsequent silver paste is filled in; some base films are too hard, resulting in too brittleness to be used normally; and the subsequent base cannot automatically detach from the silicon wafer, thereby affecting the technical problem of silver paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process of preparing the photovoltaic electrode grid line of the present invention; Figure 2 It is a schematic flow chart of another method for preparing photovoltaic electrode grid lines of the present invention; Figure 3 is a schematic flow chart of the method for preparing the PVP fiber film of the present invention; and Figure 4 It is a schematic diagram of the mold structure in the photovoltaic electrode grid line preparation method of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] like Figure 1-3 As shown, the present application relates to a PVP fiber film and a method for preparing a photovoltaic electrode grid line, and a photovoltaic cell. Figure 1-2 As shown, a method for preparing a photovoltaic electrode grid line comprises the following steps: S1. Providing a PVP fiber film prepared by a PVP fiber film preparation method; The desired PVP fiber film effect can be achieved, thus providing guarantee for subsequent processes.

[0032] It should be known that PVP is polyvinylpyrrolidone, which, as a non-ionic polymer compound, has good water solubility, biocompatibility and film-forming properties.

[0033] The present invention is based on a profound understanding of photovoltaic silver paste and a study of the water solubility of polyvinyl pyrrolidone (PVP) materials. It is found that PVP has no reactivity and weak adhesion to silver paste adhesives and solvents, and can be used as an ideal carrier for transfer silver paste.

[0034] As a synthetic water-soluble polymer compound, PVP has the general properties of water-soluble polymer compounds, such as colloid protection, film-forming, adhesiveness, hygroscopicity, solubilization or coagulation, but its most distinctive and therefore valued properties are its excellent solubility and physiological compatibility. Among synthetic polymers, PVP is rare, which is soluble in water and most organic solvents, has very low toxicity, and has good physiological compatibility, especially in the fields of medicine, food, and cosmetics that are closely related to people's health.

[0035] According to an embodiment of the present invention, preferably, S1, providing a PVP fiber film, comprising: The PVP fiber film with a thickness of 35-85um was prepared by electrospinning or flat coating.

[0036] Specifically, electrospinning is a technology that uses electrostatic force to stretch a polymer solution into nano- or micron-sized fibers, which is used to prepare polymer material films.

[0037] By adopting the electrospinning method or the flat coating method, a PVP fiber film with a thickness of 35-85um can be prepared, which can ensure good performance requirements and thus achieve a good matching effect.

[0038] Of course, those skilled in the art should be familiar with the process when the flat-plate coating method is used for preparation.

[0039] S2, using a mold to hot-emboss grooves of electrode patterns on the PVP fiber film; The desired electrode pattern can be obtained by hot pressing, thereby achieving the effects of improved accuracy and ease of realization.

[0040] According to an embodiment of the present invention, preferably, S2, using a mold to hot-emboss grooves of electrode patterns on the PVP fiber film, comprises: The prepared PVP fiber film is placed in a mold by a precision hot press and hot embossing is performed at 100-125°C to form a micron-scale or even nano-scale electrode groove structure on the surface of the PVP fiber film; By adopting a hot pressing molding machine, the precision of the PVP transfer coating after hot pressing molding can be guaranteed, and the size and shape of the grid line can be reasonably designed to reduce the ohmic loss.

[0041] 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.

[0042] It is possible to achieve the effect of having a variety of materials to choose from, thereby achieving the effect of flexible use, and then the effect can be easily achieved.

[0043] 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 substrate: relatively low cost, high mechanical strength and stability, widely used in the photovoltaic field; Copper substrate: has good electrical and thermal conductivity, suitable for applications that require fast electrical conduction; Nickel substrate: has excellent corrosion resistance and mechanical strength, suitable for long-term electrode manufacturing; Copper-nickel alloy substrate: combines the electrical conductivity of copper and the corrosion resistance of nickel, suitable for demanding 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 and corrosion resistant, suitable for electrode applications in aerospace and high temperature environments; Aluminum alloy substrate: light weight, good thermal conductivity, widely used in photovoltaic cell frames and electrical conductors.

[0044] like Figure 4 As shown, according to an embodiment of the present invention, preferably, in S2, the shape of the convex portion of the mold is complementary to that of the concave portion; The shape of the convex part of the mold is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right-angled trapezoid or a rectangle. The shape and size of the convex part correspond to the electrode grid line. In actual operation, the size and shape of the electrode grid line to be transferred are controlled to reduce the ohmic loss of the electrode grid line; the longitudinal section shape of the convex part includes but is not limited to: one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon; in this embodiment, preferably, the longitudinal section shape of the convex part is a triangle or a trapezoid. The longitudinal section design of the triangle or trapezoid helps to change the incident and refraction path of light, can better capture and guide light, can effectively reduce the reflection loss of light, so that more light is absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0045] By designing the shapes of the convex and concave parts of the mold to be complementary structures, precise docking and embossing molding effects can be ensured during the mold molding process, thereby achieving a high-precision transfer effect and improving the quality of the electrode grid lines of the final product.

[0046] Specifically, the shape of the mold can be selected from the following geometric structures: Isosceles triangle: Suitable for scenarios that require concentrated force transmission, and can form a sharp and clear transfer effect on the edge of the photovoltaic electrode grid line.

[0047] Isosceles trapezoid: With a larger bottom width and a narrower top structure, it is suitable for applications that require electrode grid lines with gradient widths to ensure uniform filling during the transfer process.

[0048] Oval shape: It can provide smooth edge transition effect, which is suitable for electrode design that requires more uniform current distribution, reducing resistance and local stress concentration.

[0049] Hexagon: The structure is stable and has good density distribution effect. It is suitable for electrode grid line design that needs to improve transfer accuracy and stability.

[0050] Right-angle trapezoid: Suitable for photovoltaic electrode designs that require uniform grid line width and neat edges to ensure accurate current distribution.

[0051] Rectangular: A classic and common design, suitable for the transfer of standardized photovoltaic electrode grid lines, providing the largest contact area to improve current conduction efficiency.

[0052] 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.

[0053] By setting the aspect ratio of the mold shape to a range of 1-3, the relationship between the height and width of the convex portion of the mold can be effectively adjusted, thereby optimizing the transfer effect of the electrode grid lines.

[0054] 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 gate lines and uniform thickness and width. This ensures that the electrode has good conductivity and that the silver paste can be evenly distributed during the transfer process.

[0055] In this embodiment, preferably, when the aspect ratio is close to 2, a moderate thickness and width are provided, so that the grid line has a certain height to improve the mechanical strength of the electrode, but is not too wide to maintain a fine structure. It is suitable for conventional photovoltaic electrode manufacturing and balances resistance, strength and process difficulty.

[0056] When the aspect ratio is 3, the height of the gate line is significantly greater than the width, which is suitable for more sophisticated narrow electrode designs. It can effectively reduce resistance and increase current density, but requires higher mold precision during the manufacturing process to ensure that the silver paste is fully filled in the narrow groove.

[0057] Therefore, the flexible setting of the aspect ratio range allows the geometry of the electrode grid lines to be adjusted according to different photovoltaic cell design requirements to achieve the best balance between conductivity, mechanical strength and production process.

[0058] S3, applying silver paste that can at least fill the groove on the heat-pressed molding side of the PVP fiber film, and removing excess silver paste on the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane; It can achieve good silver paste coating effect and make it evenly distributed on the PVP fiber film.

[0059] According to an embodiment of the present invention, preferably, S3, coating the hot-pressed molding side of the PVP fiber film with silver paste that can at least fill the groove thereon, and removing excess silver paste from the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane, comprising: Using the flat-plate coating method to evenly apply silver paste on the PVP fiber film that has been embossed with high precision can ensure that the silver paste is tightly filled in the grooves of the PVP fiber film. At the same time, the excess silver paste on the surface is scraped off to ensure that the silver paste is filled completely and evenly distributed without deformation.

[0060] It should be noted that one of the main components of photovoltaic silver paste is adhesive (phenolic resin, epoxy resin, etc.), whose function is to form a stable bond between the silver paste particles and between the particles and the silicon wafer.

[0061] S4, providing a substrate, laminating the side of the PVP fiber film with the silver paste to the substrate, and transferring the silver paste to the substrate by a stamping method with preset process parameters; wherein the stamping process parameters are: pressure of 5-20MPa, temperature of 80-180°C, and time of 1-10min; According to an embodiment of the present invention, more preferably, S4, laminating the side of the PVP fiber film having the silver paste to the substrate, comprises: The silver paste is hot-pressed and transferred to the substrate by applying uniform pressure and heating and drying, and the silver paste is heated and dried so that it fits tightly to the surface of the substrate without deformation; wherein the substrate is one of a crystalline silicon wafer, glass, metal or polymer substrate.

[0062] By applying uniform pressure to the side of the PVP fiber film that is not coated with silver paste and heating and drying it, the photovoltaic silver paste can be transferred to the silicon wafer due to the adhesion between the photovoltaic silver paste and the silicon wafer, and the silver paste can fit tightly to the silicon wafer, thereby ensuring a good transfer effect and then ensuring the stability of the silver paste structure.

[0063] S5, removing the PVP fiber film so that the silver paste transfer remains on the substrate; According to an embodiment of the present invention, preferably, S5, removing the PVP fiber film so that the silver paste remains on the substrate, comprises: The transferred silicon wafer is placed in 25-75°C water for cleaning, so that the PVP film dissolves and falls off, leaving the successfully transferred silver paste pattern to form the basic structure of the photovoltaic electrode grid line.

[0064] The PVP film can be dissolved and removed, thereby retaining the silver paste pattern completely on the silicon wafer, thereby achieving a good dissolution and separation effect.

[0065] It should be noted that the water solubility of PVP can be changed by changing the molecular weight of PVP, blending modification, etc., so that it can dissolve quickly in water.

[0066] S6. Sintering the silver paste on the substrate to form silver paste electrode grid lines with a preset aspect ratio.

[0067] According to an embodiment of the present invention, preferably, S6, sintering the silver paste on the substrate to form a silver paste electrode grid line with a preset aspect ratio, comprises: The silicon wafer after the silver paste is transferred is placed in a high-temperature furnace to sinter the silver paste; the sintering temperature is 500-800℃, ensuring that the silver paste is completely sintered and forms a tight connection with the silicon wafer to generate high-precision photovoltaic silver paste electrode grid lines with a preset aspect ratio.

[0068] After high-temperature sintering, the silver paste can form silver paste electrode grid lines of required depth and width. Preferably, the size of the silver paste electrode grid lines is 10 um deep and 5 um wide.

[0069] The present application uses a precision heat press to control the size and shape of the PVP-transferred electrode grid lines, thereby reducing the ohmic loss of the electrode grid lines; the triangular prism-shaped silver paste grid lines have better conductivity efficiency than the rectangular silver paste grid lines, and more light that hits 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 PVP coating that is water-soluble at room temperature can greatly reduce the demolding cost; the method has a simple process, the materials and equipment involved are economical and environmentally friendly, and the process cost is low.

[0070] This application also has the following beneficial effects: 1. Improving the adhesion of the transfer silver paste: By using polyvinyl pyrrolidone (PVP) as an ideal carrier, the present invention achieves stronger adhesion between the silver paste and the silicon wafer; the water solubility and biocompatibility of the PVP coating enable the silver paste to fill the groove more tightly during the transfer process, thereby ensuring a firm fit between the silver paste and the silicon wafer.

[0071] Specifically, a suitable carrier material is selected: PVP, as a water-soluble, biocompatible and film-forming polymer compound, has good adhesion and can serve as an ideal carrier for transferring silver paste to ensure a firm fit between the silver paste and the silicon wafer.

[0072] 2. Improve the accuracy and stability of electrode patterns: Prepare 35-85um PVP fiber films through electrospinning, and press micron-scale or even nanometer-scale electrode patterns in a precision hot press. The present invention achieves high accuracy and stability of electrode patterns, which helps to improve the performance and efficiency of photovoltaic cells.

[0073] 3. Simplify the production process: The flat-plate coating method is used to apply silver paste on the PVP coating after hot pressing, and then the silver paste is transferred onto the silicon wafer. The present invention simplifies the production process, reduces production costs and time, and improves production efficiency.

[0074] Specifically, the silver paste is applied by a flat-plate coating method and transferred onto a silicon wafer. The PVP coating is then dissolved and removed by washing with water at an appropriate temperature, ultimately forming a micron-scale electrode grid line with a depth of 10um and a width of 5um, thus achieving successful transfer and sintering of the silver paste.

[0075] From the above description, it can be seen that the present application achieves the following technical effects: In the embodiment of the present application, a PVP carrier-based method is adopted, through S1, preparing a PVP fiber film of a preset thickness; S2, using a mold to emboss a groove of a molded electrode pattern on the PVP fiber film with high precision; S3, applying a silver paste that can at least fill the groove on the hot-pressed molding side of the PVP fiber film, and removing excess silver paste on the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane; S4, the side of the PVP fiber film having the silver paste is attached to the substrate, and the silver paste is transferred to the substrate by an embossing method with preset process parameters; wherein the embossing process parameters are: pressure of 5-20MPa, temperature of 80-180°C and time of 1-10min; S5, removing the PVP fiber film so that the silver paste remains on the substrate; S 6. The silver paste is sintered on the substrate to form a silver paste electrode grid line with a preset aspect ratio, thereby achieving the purpose of improving the adhesion of the transferred silver paste, thereby ensuring that the silver paste is firmly bonded to the silicon wafer, improving the accuracy and stability of the electrode pattern, and reducing the production cost and production efficiency. The technical effect solves the problem that the accuracy of the screen printing process is limited by the screen aperture and printing pressure, and it is difficult to achieve very fine patterns and high-resolution printing. Generally, the silver paste line width is at least tens of microns; at the same time, a certain amount of waste will be generated during the screen printing process, resulting in waste of materials; moreover, the screen plug has a limited service life, is expensive, and has a high overall cost; and screen printing is a relatively slow production process that cannot meet the needs of large-scale production, affecting production efficiency.

[0076] Compared with screen printing, the use of transfer silver paste technology has the following advantages: 1. Higher resolution: Silver paste transfer technology is generally able to achieve higher resolution because the silver paste can be accurately transferred on a smaller scale, thus achieving finer patterns and lines.

[0077] 2. The quality of the finished product is more stable: Since the transfer silver paste technology can be carried out in a controlled environment, a more stable and consistent finished product quality can be obtained, avoiding problems such as uneven ink flow that may occur in screen printing.

[0078] 3. Higher production efficiency: Transfer silver paste technology can usually achieve automated production, improve production efficiency, reduce manual operations, and save time and costs.

[0079] 4. Wider applicability: Silver paste transfer technology can be applied to various substrates and materials, including flexible substrates and non-flat surfaces, and has a wider range of applicability.

[0080] 5. Stronger durability: Transfer silver paste technology can usually achieve better adhesion and durability, making the printed pattern more durable and stable, and less susceptible to external environmental influences.

[0081] like Figure 3 As shown, the present application also relates to a method for preparing a PVP fiber film, comprising the following steps: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution; A uniform spinning solution can be obtained by solution preparation.

[0082] According to an embodiment of the present invention, preferably, S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, comprises: PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with mass fractions of 3-5% PVP and 18-22% tetrabutyl titanate, respectively.

[0083] 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, respectively.

[0084] According to an embodiment of the present invention, preferably, S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, further comprises: PVP and diphenylalanine were slowly added to a mixed solvent of methanol and N,N-methylacetamide under stirring, and stirring was continued until they were completely dissolved to obtain a transparent polymer solution.

[0085] 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 electrospinning to form stable fibers.

[0086] Of course, the present application provides a variety of solution preparation schemes, which can be selected according to actual needs, thereby achieving flexible use effects.

[0087] S12, placing the spinning solution in a syringe, and spinning through an electrospinning device; According to an embodiment of the present invention, preferably, S12, placing the spinning solution in a syringe, and spinning through an electrospinning device, comprises: The prepared spinning solution is placed in a syringe with a preset inner diameter, and electrospinning is performed using a preset working voltage intensity.

[0088] Specifically, a syringe with an inner diameter of 0.43 mm was used to ensure uniform outflow of the spinning solution and stable fiber formation; The applicable voltage range is 1.8 kV / cm, which can generate a stable electric field during the spinning process, thereby effectively stretching the spinning solution to form fibers; During the spinning process, temperature and humidity are controlled to prevent fiber breakage or excessive stretching, ensuring fiber stability and morphology consistency.

[0089] Of course, the specific parameter settings can be set according to actual usage requirements and are not limited in this application.

[0090] S13. During the spinning process, the fibers will form a film on the collecting device. The collected fiber film is post-processed to finally obtain the desired PVP fiber film.

[0091] According to an embodiment of the present invention, preferably, S13, during the spinning process, the fiber forms a film on the collecting device, and the collected fiber film is post-processed to finally obtain the desired PVP fiber film, including: During the spinning process, the fiber will form a film on the collecting device, and the fiber film is collected to obtain a PVP fiber film to be post-processed; Silicone oil is added to modify the PVP fiber film to be post-treated simultaneously; The synchronously modified PVP fiber film is placed in a programmed temperature muffle furnace, heated to the target temperature according to a predetermined heating curve, and maintained for a preset time to selectively remove PVP by calcination, and finally obtain the desired PVP fiber film.

[0092] Specifically, the PVP fiber film formed by spinning needs to be uniformly deposited on the collecting device; depending on the final use of the fiber film, the subsequent processing steps may vary. In general, the following steps can further optimize the film properties: The surface can be modified by adding silicone oil to enhance the flexibility and uniformity of the fiber film.

[0093] The collected PVP fiber film is placed in a programmed temperature muffle furnace, heated to an appropriate temperature according to the set heating curve, and maintained for a certain period of time to calcine and remove PVP. This process can control the retention of fiber structure and the formation of nanofiber network by adjusting the calcination temperature (generally between 300-500℃) and the heating rate.

[0094] Through the above steps, a suitable PVP fiber film can be prepared. The molecular structure of the PVP fiber film is: Those skilled in the art should be aware of this molecular structure.

[0095] The PVP fiber film prepared by the PVP fiber film preparation method of the present application has a certain flexibility and is not too brittle; at the same time, the base film is not too soft, which can prevent deformation after the silver paste is subsequently filled in; and, it can subsequently be dissolved in water, automatically detached from the silicon wafer, while leaving the silver paste unaffected.

[0096] The glass transition temperature of PVP fiber film is 60-80℃, so the inherent properties of PVP ensure that it will not rebound and its shape will not change after hot pressing.

[0097] From the above description, it can be seen that the present application achieves the following technical effects: In an embodiment of the present application, electrospinning is used to prepare a PVP fiber film, and through S11, PVP is dissolved in a preset solvent to prepare a uniform spinning solution; S12, the spinning solution is placed in a syringe and spun through an electrospinning device; S13, during the spinning process, the fiber will form a film on a collecting device, and the collected fiber film is post-processed to finally obtain the desired PVP fiber film, thereby achieving the purpose of obtaining the desired PVP fiber film, thereby achieving the technical effect of the base film having good flexibility and easy detachment, and further solving the problem in the transfer technology that the transfer base film cannot meet the use requirements due to its flexibility, resulting in some base films being too soft, resulting in deformation after subsequent silver paste is filled in; some base films are too hard, resulting in too brittleness to be used normally; and the subsequent base cannot automatically detach from the silicon wafer, thereby affecting the technical problem of silver paste.

[0098] The specific examples are further described below: Example 1 like Figure 1 As shown, 1. Solution preparation: 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 respectively; 2. Electrospinning: Using a working voltage of 1.8 kV / cm, a syringe inner diameter of 0.43 mm, a spinning solution flow rate of 0.5 mL / h, a temperature of 25 °C, and a humidity of 45%, spinning formed a PVP fiber film with a thickness of 50 μm; 3. High-precision embossing: At 130°C, a precision hot press is used to heat press the mold and apply a pressure of 20MPa to form a micron- or nanometer-scale groove pattern on the surface of the fiber film; 4. Silver paste coating and transfer: Use the flat coating method to evenly apply the silver paste on the surface of the PVP film, scrape off the excess silver paste, and then transfer it 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°C for 1 minute to form silver paste electrode grid lines.

[0099] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on the PVP carrier are: the depth of the silver paste electrode grid line is 10μm, the width is 5μm, the silver paste is tightly bonded to the silicon wafer, the conductivity is excellent, and the resistivity is as low as 1.3μΩ·cm, which is suitable for the application of high-efficiency photovoltaic cells.

[0100] Example 2 The difference between Example 2 and Example 1 is that: 1. Solution preparation: PVP and diphenylalanine are dissolved in a mixed solvent of methanol and N, N-methylacetamide at a mass fraction of 4% and 10%, respectively, to form a uniform polymer solution; 2. Electrospinning: Using the same electrospinning conditions, a PVP fiber film with a thickness of 65 μm was formed; 3. High-precision embossing hot pressing: Apply 15MPa pressure at 110℃ to hot press micron-level grooves; 4. Silver paste coating and transfer: The same method is used to coat and transfer the silver paste; 5. PVP removal: Wash in 60℃ water for 7 minutes to dissolve and remove PVP; 6. Silver paste sintering: sinter at 800℃ for 30 minutes.

[0101] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on the PVP carrier are: 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.

[0102] Example 3 The difference between Example 3 and Example 1 is that: 1. Solution preparation: the same PVP and tetrabutyl titanate solution as in Example 1 is used; 2. Electrospinning: By increasing the spinning solution flow rate to 1 mL / h, a PVP fiber film with a thickness of 85 μm was formed; 3. High-precision embossing hot pressing: hot pressing at 125℃ and 25MPa to form micron-level grooves; 4. Silver paste coating and transfer: The same method is used to coat and transfer the silver paste; 5. PVP removal: Wash in 55°C water for 8 minutes to dissolve and remove PVP; 6. Silver paste sintering: sinter at 700℃ for 1 minute.

[0103] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on the PVP carrier are: the depth of the silver paste electrode grid line is 12μm, the width is 7μm, and the conductivity is equivalent to the aforementioned embodiment, but due to the thick PVP film, the silver paste transfer is uneven in some areas, resulting in a slight decrease in conductivity.

[0104] Example 4 The difference between Example 4 and Example 1 is that: 1. Preparation of PVA solution: 8 g of PVA powder was weighed and dissolved in 92 mL of distilled water to form an 8% PVA solution; the mixture was stirred at 80° C. for 1 hour until the PVA was completely dissolved to form a uniform solution; 2. Electrospinning equipment settings: PVA solution was injected into a syringe with an inner diameter of 0.43 mm; the high voltage power supply was set to 15 kV, and the distance between the collecting plate and the syringe needle was kept at 12 cm; 3. Spinning process: Under the action of the electric field, the PVA solution is ejected through the syringe needle to form nanofibers and deposited on the rotating collection plate; the spinning lasts for 30 minutes until a uniform fiber network film is formed on the collection plate; 4. Drying and post-treatment: After spinning, the film is dried in a drying oven at 40°C for 12 hours to remove moisture and stabilize the film.

[0105] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on PVA carrier are: the PVA film prepared by electrospinning has a nanoscale fiber structure, the fiber diameter is 150-300nm, and the film has a porous structure; the porosity of the membrane is high, suitable for gas filtration and biomedical materials; the tensile strength of the fiber film is 20MPa, and the elongation at break is 50%.

[0106] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the conventional PVP coating process without electrospinning method is 1. PVP coating: The PVP solution is directly coated on the silicon wafer using the traditional coating method with a thickness of 40 μm; 2. Hot pressing: At 100°C, apply 10MPa pressure to hot press the electrode groove; 3. Silver paste coating and transfer: The same method is used to coat and transfer the silver paste; 4. PVP removal: Wash in 30℃ water for 3 minutes; 5. Silver paste sintering: sinter at 700℃ for 1 minute.

[0107] At this time, the test results of the photovoltaic electrode grid line transfer method based on the PVP carrier are: the depth of the silver paste electrode grid line is 6μm, the width is 10μm, and the resistivity is 2.1μΩ·cm. Due to the poor uniformity of the PVP coating and the poor silver paste filling effect, the electrode line width is uneven and the conductivity is poor, which cannot meet the high-precision requirements of photovoltaic cells.

[0108] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that, 1. Electrospinning: the PVP film is prepared using the spinning conditions of Example 1; 2. Hot pressing: hot pressing at 90℃ and 10MPa; 3. Silver paste coating and transfer: The same method is used to coat and transfer the silver paste; 4. PVP removal: Wash in 40℃ water for 4 minutes; 5. Silver paste sintering: sinter at 700℃ for 1 minute.

[0109] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on the PVP carrier are: due to the low hot pressing temperature, the PVP fiber was not completely 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, and the conductive performance was significantly reduced, which could not meet the application requirements.

[0110] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that PEG is used as the base material.

[0111] At this time, after testing, the test results of the photovoltaic electrode grid line transfer method based on PVP carrier are: due to the different interface properties of PEG and silver paste, the adhesion during the transfer process is poor, resulting in the failure of the silver paste to be completely transferred to the silicon wafer; the morphology of the electrode grid line is not as clear as when it is based on PVP, and there are problems of irregular edges and silver paste shedding; the conductivity of the silver paste electrode grid line is low, and the silver paste cannot be effectively transferred in some areas.

[0112] From the above test results we can see that: 1. It can be seen from Examples 1 and 2 that both can achieve high-precision silver paste electrode grid lines with good conductivity, flexibility, water solubility and bonding strength, and Example 1 in particular exhibits the best performance.

[0113] 2. It can be seen from Example 3 that, as the thickness of the PVP film increases, although the electrode depth increases, there is an uneven problem in the transfer process, which affects the conductivity.

[0114] 3. It can be seen from Example 1 and Comparative Example 1 that the traditional PVP coating and low-temperature hot pressing conditions cannot form an ideal electrode structure, resulting in poor quality of the silver paste grid line and insufficient conductivity.

[0115] 4. It can be seen from Example 1 and Comparative Example 2 that if the hot pressing temperature is too low, the PVP fibers will not be completely compacted, so that the silver paste electrode grooves are not clearly formed, thereby affecting the conductive properties.

[0116] 5. It can be seen from Example 1 and Comparative Example 3 that using PEG as the base material has problems with poor adhesion, electrode morphology and conductivity.

[0117] 6. It can be seen from Examples 1 and 4 that the 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.

[0118] The present application also relates to a photovoltaic cell, including the photovoltaic electrode grid lines prepared as 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 parts not mentioned in this embodiment, please refer to the above corresponding contents.

[0119] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical scheme of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A method for preparing a PVP fiber film, characterized in that: The following steps are involved: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution; S12, placing the spinning solution in a syringe, and spinning through an electrospinning device; S13. During the spinning process, the fibers will form a film on the collecting device. The collected fiber film is post-processed to finally obtain the desired PVP fiber film.

2. The method for preparing the PVP fiber film according to claim 1, characterized in that: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, including: PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with mass fractions of 3-5% PVP and 18-22% tetrabutyl titanate, respectively.

3. The method for preparing the PVP fiber film according to claim 1, characterized in that: S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, further comprising: PVP and diphenylalanine were slowly added to a mixed solvent of methanol and N,N-methylacetamide under stirring, and stirring was continued until they were completely dissolved to obtain a transparent polymer solution.

4. The method for preparing the PVP fiber film according to claim 1, characterized in that: S12, placing the spinning solution in a syringe and spinning through 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.

5. The method for preparing the PVP fiber film according to claim 1, characterized in that: S13. During the spinning process, the fiber will form a film on the collecting device. The collected fiber film is post-processed to finally obtain the desired PVP fiber film, including: During the spinning process, the fiber will form a film on the collecting device, and the fiber film is collected to obtain a PVP fiber film to be post-processed; Silicone oil is added to modify the PVP fiber film to be post-treated simultaneously; The synchronously modified PVP fiber film is placed in a programmed temperature muffle furnace, heated to the target temperature according to a predetermined heating curve, and maintained for a preset time to selectively remove PVP by calcination, and finally obtain the desired PVP fiber film.

6. A method for preparing a photovoltaic electrode grid line, characterized in that: The following steps are involved: S1. Provide a PVP fiber film prepared by any one of the preparation methods of claims 1 to 5; S2, using a mold to hot-emboss grooves of electrode patterns on the PVP fiber film; S3, applying silver paste that can at least fill the groove on the heat-pressed molding side of the PVP fiber film, and removing excess silver paste on the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane; S4, providing a substrate, laminating the side of the PVP fiber film having the silver paste to the substrate, and transferring the silver paste to the substrate by a embossing method with preset process parameters; wherein the embossing process parameters are: pressure of 5-20MPa, temperature of 80-180°C, and time of 1-10min; S5, removing the PVP fiber film so that the silver paste remains on the substrate; S6. Sintering the silver paste on the substrate to form silver paste electrode grid lines with a preset aspect ratio.

7. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S1. Provide PVP fiber film, including: The PVP fiber film with a thickness of 35-85um was prepared by electrospinning or flat coating.

8. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S2. Using a mold to thermally emboss grooves of electrode patterns on a PVP fiber film, including: The prepared PVP fiber film is placed in a mold by a precision hot press and hot embossing is performed at 100-125°C to form a micrometer- or even nanometer-scale electrode groove structure on the surface of the PVP fiber film.

9. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: 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.

10. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: In S2, the convex portion of the mold is complementary in shape to the concave portion; Wherein, the shape of the mold is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right-angled trapezoid or a rectangle.

11. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: In S2, the aspect ratio of the mold shape ranges from 1 to 3.

12. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S3, coating the heat-pressed side of the PVP fiber film with silver paste that can fill the groove thereon, and removing excess silver paste from the surface of the PVP fiber film so that the surface of the groove and the silver paste are located on the same plane, including: The silver paste is evenly applied on the hot-pressed PVP fiber film by a flat coating method so that the silver paste completely fills the grooves, and the excess silver paste is scraped off to ensure that the silver paste is completely filled and evenly distributed without deformation.

13. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S4, providing a substrate, and laminating the side of the PVP fiber film having the silver paste to the substrate, comprising: The silver paste is hot-pressed and transferred onto a substrate by applying uniform pressure, and the silver paste is heated and dried to make it fit tightly to the surface of the substrate without deformation; wherein the substrate is one of a crystalline silicon wafer, glass, perovskite, metal or polymer substrate.

14. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S5. Removing the PVP fiber film so that the silver paste remains on the substrate, including: The transferred silicon wafer is placed in 25-75°C water for cleaning, so that the PVP film dissolves and falls off, leaving the successfully transferred silver paste pattern to form the basic structure of the photovoltaic electrode grid line.

15. The method for preparing photovoltaic electrode grid lines according to claim 6, characterized in that: S6, sintering the silver paste on the substrate to form a silver paste electrode grid line with a preset aspect ratio, including: The silicon wafer after the silver paste is transferred is placed in a high-temperature furnace to sinter the silver paste; the sintering temperature is 500-800℃, ensuring that the silver paste is completely sintered and forms a tight connection with the silicon wafer to generate high-precision photovoltaic silver paste electrode grid lines with a preset aspect ratio.

16. A photovoltaic cell, characterized in that The invention comprises a photovoltaic electrode grid line prepared by the preparation method according to any one of claims 6 to 14.

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