Method and apparatus for preparing solar cell grid lines

Abstract

The present application relates to a method for preparing solar cell grid lines and an apparatus therefor, which are intended to reduce material consumption by means of transfer printing technology, and implement stable and efficient preparation of grid lines of a small-sized solar cell. The method comprises: respectively manufacturing conductive paste transfer layers corresponding to a front surface and a back surface of a solar cell on transfer substrates, grid line pattern grooves being provided in the transfer layers; and uniformly filling conductive paste into the grooves, accurately attaching the conductive paste transfer layers for the front surface and the back surface to the corresponding surfaces of the solar cell, and synchronously transferring grid line patterns to the front surface and the back surface of the solar cell by means of simultaneously applying appropriate vertical pressure and temperature. The present application utilizes the technical solution of simultaneous vertical transfer, which effectively balances the force distribution, avoids the problem of cracking of the solar cell, and significantly improves the close fit between the grid lines and the surfaces of the solar cell and the current collection efficiency. In addition, the present application further provides an apparatus for preparing solar cell grid lines, so that an entire preparation process of the solar cell grid lines can be completed in one entire device, thereby improving the integration of a production line.

Description

A method and apparatus for fabricating grid lines in solar cells Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a method and apparatus for fabricating grid lines of a solar cell. Background Technology

[0002] With increasing global awareness of environmental protection and the active promotion of national carbon peaking and carbon neutrality goals, building a new power system based on new energy sources has become an important development direction in the energy sector. As a core component of the new energy field, the photovoltaic industry has seen a significant rise in its status and has ushered in unprecedented development opportunities. Solar cells, as a key component of photovoltaic systems, directly affect the efficiency and stability of the entire system through performance optimization and improvement. Currently, industrial production, primarily using monocrystalline silicon photovoltaic cells, dominates the solar cell market, accounting for over 90% of total output.

[0003] In solar cells, the electrode grid lines are a crucial component, significantly impacting cell performance. The primary function of the electrode grid lines is to collect the current generated by the photovoltaic effect and conduct it to the external circuitry. Therefore, the selection of electrode grid line materials and the optimization of their fabrication processes are essential for improving the photoelectric conversion efficiency of solar cells. Metallic conductive pastes, due to their excellent conductivity and chemical stability, have become one of the most widely used electrode grid line materials.

[0004] However, many technical problems remain to be solved in the fabrication of photovoltaic cells using conductive paste to form grid lines. While traditional screen printing technology is mature and equipment is widely available, its precision is limited by the mesh size and printing pressure, making it difficult to achieve very fine patterns and high-resolution printing. Furthermore, screen printing generates a significant amount of waste, leading to substantial material waste. Simultaneously, the limited lifespan and high cost of screens contribute to the overall high cost. More importantly, screen printing is relatively slow, failing to meet the demands of large-scale production and thus impacting production efficiency.

[0005] Specifically, the screen printing process for grid lines includes printing the front and back main / sub-grid lines, as well as drying and sintering. While these steps enable the fabrication of the front and back main / sub-grid lines for photovoltaic cells, the entire process is cumbersome and inefficient. Each printing requires repositioning and adjusting the screen, increasing operational complexity and extending the production cycle. Therefore, to overcome the shortcomings of existing screen printing technology, developing a novel photovoltaic cell electrode grid line fabrication technology that is simple, low-cost, highly efficient, and has high resolution is particularly important.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a method for fabricating grid lines in a solar cell, which enables the fabrication of micron-level electrode patterns. The fabrication process is simple and can significantly reduce material consumption, thereby lowering production costs. This objective is achieved through the following technical solution: the method for fabricating grid lines in a solar cell includes:

[0008] Conductive paste transfer layers corresponding to the front and back grid lines are respectively fabricated on the transfer substrate, and the conductive paste transfer layers include grid line pattern grooves.

[0009] The grooves of the grid pattern are filled with conductive paste;

[0010] The conductive paste transfer layer corresponding to the front grid line is bonded to the front of the battery cell, and the conductive paste transfer layer corresponding to the back grid line is bonded to the back of the battery cell.

[0011] Pressure is applied to both the front and back of the battery cell simultaneously to transfer the conductive paste in the groove of the grid pattern to the front and back of the battery cell.

[0012] The transferred conductive paste is converted into front and back grid lines.

[0013] In one embodiment, the conductive paste transfer layer is fabricated by coating a water-soluble polymer material onto the transfer substrate, drying it, and controlling the thickness to be within the range of 10-50 μm.

[0014] In one embodiment, the transfer substrate is a soft material.

[0015] In one embodiment, a grid pattern groove is formed on the conductive paste transfer layer by means of an embossing method using a mold.

[0016] In one embodiment, the gate pattern includes a first gate pattern with a groove depth in the range of 10-50 μm and a width in the range of 50-1000 μm, and a second gate pattern with a groove depth in the range of 10-15 μm and a width in the range of 5-50 μm.

[0017] In one embodiment, the step of filling the grid pattern groove with conductive paste includes applying conductive paste to the embossed grid pattern groove and scraping off excess conductive paste.

[0018] In one embodiment, the temperature during transfer is selected in the range of 100-180°C, the applied pressure is selected in the range of 5-15 MPa, and the duration is selected in the range of 2-10 min.

[0019] In one embodiment, the step of transferring the conductive paste in the grid pattern groove to the front and back of the battery cell includes first removing the transfer substrate and then removing the conductive paste transfer layer by liquid dissolution.

[0020] In addition, this application also provides a solar cell grid line fabrication apparatus, which can realize the aforementioned solar cell grid line fabrication method in a complete set of equipment, thereby improving the integration of the solar cell production line, specifically including:

[0021] Transfer substrate;

[0022] A coating component for coating a conductive paste transfer layer onto the transfer substrate;

[0023] A hot-pressing component is used to form grid pattern grooves on the conductive paste transfer layer;

[0024] A slurry coating component for filling conductive slurry into the grooves of the grid pattern;

[0025] The scraping component is used to scrape and remove excess conductive paste;

[0026] A transfer component is used to attach the conductive paste transfer layer to the surface of the battery cell and transfer the conductive paste in the groove of the grid pattern to the surface of the battery cell.

[0027] The transfer mechanism is used to transfer the battery cells to the station where the transfer unit is located;

[0028] The system includes a transfer substrate corresponding to the front grid lines and the back grid lines, a coating component, a hot pressing component, a slurry coating component, a scraping component, and a transfer component, which simultaneously transfer conductive paste to the front and back of the battery cell.

[0029] In one embodiment, the transfer substrate is a cylindrical roller, and the coating component, the hot pressing component, the slurry coating component, and the leveling component are arranged on the cylindrical roller in the order of rotation of the cylindrical roller.

[0030] In one embodiment, the transfer substrate has a polygonal cross-section, comprising multiple planes, which are sequentially arranged on the surface of the transfer substrate in the order of coating component, hot pressing component, slurry coating component, and scraping component, with the order being the same as the rotation direction of the transfer substrate.

[0031] In one embodiment, a movable component is also included, which synchronously adjusts the height of the upper and lower transfer substrates of the battery cell.

[0032] In one embodiment, a cleaning component is also included, positioned before the coating station, to clean the surface of the transfer substrate.

[0033] In one embodiment, the system further includes a drying component, a cleaning component, and a sintering component. The drying component is used to dry the conductive paste, the cleaning component is used to dissolve and remove the conductive paste transfer layer using a solution, and the sintering component is used to sinter the conductive paste.

[0034] In addition, this application also provides a battery cell, including grid lines on the front and back sides of the battery cell, which are prepared by the aforementioned battery cell grid line preparation method.

[0035] Compared with the prior art, this application has the following beneficial effects:

[0036] By employing a mold-pressing method to form grid pattern grooves on a conductive paste transfer layer, and precisely controlling the depth and width of the grooves (e.g., depth within the range of 10-50 μm and 5-15 μm, width within the range of 50-1000 μm and 3-50 μm), micron-level electrode patterns can be easily fabricated, improving the precision and resolution of the electrode grid lines and laying a solid foundation for further improvements in solar cell efficiency. The method in this application simplifies the preparation process by directly fabricating the conductive paste transfer layer on the transfer substrate and completing the transfer of both front and back grid lines in one step, reducing the need for multiple printing and positioning steps. Simultaneously, the precise filling and scraping of the conductive paste during the transfer process effectively reduces material waste.

[0037] By simultaneously transferring the plating onto the upper and lower parts of the solar cell, the fabrication of front-side grid lines (including main and secondary grid lines) and back-side grid lines (including main and secondary grid lines) can be achieved in one step, significantly improving production efficiency and reducing fabrication steps and time costs. The fabrication method designed in this application employs a simplified process, reducing time investment, lowering production costs, and improving production efficiency by simultaneously transferring the plating onto the upper and lower parts of the solar cell. Specifically, PVA can be used as a carrier to help the silver paste adhere tightly to the solar cell. Simultaneously, it dissolves after transfer, allowing the conductive paste to be transferred onto the solar cell. Combined with hot-press transfer technology, the PVA grooves coated with conductive paste are tightly adhered to the solar cell. After heating and curing, electrode grid lines with a specific pattern are formed. Finally, the PVA is removed using a solvent, achieving high efficiency and stability in fabricating multiple grid lines in a single step.

[0038] The battery cell grid line fabrication apparatus of this application realizes the battery cell grid line fabrication method in a complete set of equipment. Thanks to the highly integrated fabrication apparatus design, including transfer substrate, coating component, hot pressing component, slurry coating component, leveling component, transfer component and transport mechanism, it can simplify the current grid line electrode fabrication production line, reduce equipment complexity, realize full automation from conductive slurry coating to grid line transfer, improve the integration and automation level of the production line, is suitable for industrial production, and is conducive to large-scale production and application. Attached Figure Description

[0039] Figure 1 is a schematic diagram of the structural flow of the battery cell grid line fabrication method in an embodiment of this application;

[0040] Figure 2 is a schematic diagram of the grid line distribution of the battery cell in an embodiment of this application;

[0041] Figure 3 is a cross-sectional schematic diagram of the shape of the battery cell grid lines in an embodiment of this application;

[0042] Figure 4 is a schematic diagram of the structure of a battery cell grid line fabrication apparatus in one embodiment of this application;

[0043] Figure 5 is a schematic diagram of the structure of a battery cell grid line fabrication apparatus in another embodiment of this application.

[0044] Explanation of reference numerals in the attached drawings: 100, transfer substrate; 200, conductive paste transfer layer; 210, coating component; 300, grid pattern groove; 310, hot pressing component; 400, conductive paste; 410, coating component; 420, leveling component; 500, grid line; 600, transfer component; 610, drying component; 620, cleaning component; 630, sintering component. Detailed Implementation

[0045] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0046] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0047] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0048] Traditionally, screen printing technology is widely used to fabricate solar cell grid lines. Although this technology is mature and widely applied, its limitations in precision, material waste, and low production efficiency make it difficult to meet the current photovoltaic industry's demands for high efficiency, low cost, and large-scale production. Therefore, this application aims to explore a novel method and apparatus for fabricating solar cell grid lines to achieve precise fabrication of micron-level electrode patterns, simplify the fabrication process, reduce material consumption, and improve production efficiency. By combining mold imprinting and transfer printing technologies, this method can improve fabrication efficiency and reduce costs while maintaining high precision and high quality. Please refer to Figure 1, which is a schematic diagram of the structural flow of the battery cell grid line preparation method. The battery cell grid line preparation method in a preferred embodiment of this application can significantly reduce material consumption and thus reduce production costs, and can stably form small-sized battery cell grid lines. The method specifically includes: fabricating conductive paste transfer layers 200 corresponding to the front grid lines and the back grid lines on a transfer substrate 100, respectively. The conductive paste transfer layer 200 includes grid line pattern grooves 300. The grid line pattern grooves 300 are filled with conductive paste 400. The conductive paste transfer layer 200 corresponding to the front grid lines is attached to the front of the battery cell, and the conductive paste transfer layer 200 corresponding to the back grid lines is attached to the back of the battery cell. Pressure is applied to the front and back of the battery cell simultaneously to transfer the conductive paste 400 in the grid line pattern grooves 300 to the front and back of the battery cell, and the transferred conductive paste 400 is converted into front and back grid lines.

[0049] This application first fabricates conductive paste transfer layers 200 on a transfer substrate 100, corresponding to the front and back grid lines of the solar cell, respectively. This step uses two transfer substrates 100, each with a finely designed grid line pattern groove 300 serving as a carrier for the conductive paste 400. The shape, size, and distribution of these grooves are precisely calculated to ensure optimal conductivity and photoelectric conversion efficiency of the final grid lines 500. Next, a filling technique is used to uniformly and fully fill the grid line pattern grooves 300. The specific filling method can be selected as needed. This step ensures that the conductive paste 400 completely covers the bottom and sidewalls of the grooves while avoiding unnecessary paste accumulation outside the grooves. This minimizes material waste while maintaining the quality of the grid lines 500. A specific method can be the coating and scraping technique described below. Subsequently, the prepared front grid conductive paste transfer layer 200 is precisely bonded to the front of the solar cell, while the back grid conductive paste transfer layer 200 is bonded to the back of the solar cell. In this step, by controlling the positioning accuracy and bonding degree, the contact resistance between the grid line 500 and the surface of the solar cell is minimized, thereby improving the current collection efficiency.

[0050] After bonding, by simultaneously applying appropriate pressure and temperature, and utilizing the properties of the transfer substrate 100 and the conductive paste 400, the conductive paste 400 within the grid pattern grooves 300 is precisely and uniformly transferred to the front and back sides of the solar cell. This step enables high-precision replication of the grid pattern. Furthermore, by optimizing pressure and temperature conditions, the flow and curing process of the conductive paste 400 can be further controlled, resulting in a more uniform and dense grid structure 500. Through methods such as heat treatment, the transferred conductive paste 400 is transformed into front and back grid lines with good conductivity and stability. Specifically, conventional sintering methods can be used. This improves the mechanical strength and durability of the grid lines 500, and by optimizing processing conditions, the microstructure and electrical properties of the grid lines 500 can be further adjusted to meet the needs of different application scenarios.

[0051] It is particularly important to emphasize that this application employs a simultaneous top-and-bottom transfer technology, which not only achieves synchronous transfer of the grid line pattern on the front and back of the solar cell, but also demonstrates technological advantages in terms of balanced force distribution, reduced production steps, and improved overall manufacturing efficiency. Through precisely designed imprinting equipment and process parameters, it is ensured that the pressure on the front and back of the solar cell is uniform and consistent during the imprinting process. This balanced force distribution not only avoids microcracks in the solar cell caused by uneven pressure, but also ensures a tight fit between the grid lines 500 and the solar cell surface, thereby reducing contact resistance and improving current collection efficiency. Furthermore, the balanced force distribution helps reduce stress concentration during the imprinting process. Traditional solar cell grid line manufacturing processes often require separate fabrication of the front and back grid lines 500, which not only increases production steps and complexity but may also lead to inconsistencies between the front and back grid lines during fabrication. The simultaneous top-and-bottom imprinting process, however, allows for the simultaneous application of multiple steps, such as alignment, in a single operation, simplifying the production process and improving production efficiency and consistency. The innovative process of simultaneous top and bottom imprinting has shown significant technical advantages in the fabrication of battery cell grid lines. It not only balances the distribution of force and saves production steps, but also improves the overall fabrication efficiency.

[0052] Specifically, the fabrication of the conductive paste transfer layer 200 includes coating a water-soluble polymer material onto the transfer substrate 100, drying it, and controlling the thickness to within the range of 10-50 μm. Water-soluble polymer materials include, but are not limited to, PVA, PVP, and PEG. This application involves simultaneous transfer on both the upper and lower portions of the battery cell. In a specific embodiment, PVA can be used as the main material for the metal paste transfer layer. The solubility of PVA allows the silver paste to be successfully transferred onto the battery cell, while the hot-press transfer technology ensures a tight bond between the silver paste and the battery cell, forming stable electrode grid lines. PVA has a glass transition temperature of 75-85°C. When heated to above 100°C in air, it slowly discolors and becomes brittle. The inherent properties of PVA ensure that it does not spring back or change shape after hot pressing. PVA is insoluble in organic solvents such as gasoline, kerosene, vegetable oil, benzene, toluene, dichloroethane, carbon tetrachloride, acetone, ethyl acetate, methanol, and ethylene glycol. PVA is incompatible with and non-reactive to the binder in the silver paste. It should be noted that PVA is a specific material selection and a preferred technical solution. Other materials with similar properties can also be used as the material for the conductive paste transfer layer 200. The main selection principle is to select a water-soluble polymer material that is incompatible with and non-reactive to the substances in the paste. The selection is based on the different paste compositions. Under this selection principle, the transfer layer can be removed by aqueous solution without affecting the distribution of the conductive paste. Combined with the method flow of this application, the removal method of the transfer layer can be simplified, thereby improving the integration of the entire process on the production equipment.

[0053] The method described in this application can control the size and shape of PVA transfer composite conductive grid lines by using the parameters (heating temperature, pressure, time, etc.) of the precision hot pressing component 310 and a precision mold, thereby reducing the ohmic loss of the electrode grid lines. PVA, as a biodegradable and environmentally friendly material, has low environmental impact. The room-temperature water-soluble PVA coating can significantly reduce demolding costs. The materials and equipment involved are economical and environmentally friendly, with low process costs. This is a new technology that can change the current printing pattern of silver electrode grid lines in photovoltaic cells.

[0054] The main material of conductive paste 400 is usually silver paste because silver has excellent conductivity and chemical stability, making it an ideal choice for preparing high-efficiency photovoltaic cell grid lines. However, with continuous technological advancements and cost considerations, conductive paste 400 formed from other components can also be selected, such as copper paste and aluminum paste. These materials also exhibit good conductivity under specific conditions. In the technical solution of this application, there are no special requirements for the specific material of conductive paste 400, which can meet the requirements of different scenarios. Furthermore, since this application forms conductive paste 400 simultaneously on both the upper and lower surfaces, it can meet the requirement of using different specific materials independently on the upper and lower surfaces without increasing the complexity of equipment components. For example, silver paste can be used on the front side, while aluminum paste can be used on the back side. One of the main components of photovoltaic silver paste is a binder (phenolic resin, epoxy resin, etc.), which serves to form a stable bond between the silver paste particles and between the particles and the solar cell. A 20±2μm thick PVA flexible film can be stably prepared on a carrier using a flat plate coating method. In addition, the technically mature hot pressing component 310 can ensure the precision of the PVA transfer coating after hot pressing. The size and shape of the grid lines 500 can be reasonably designed so that when PVA needs to be removed, the water solubility of PVA can be changed by changing the degree of hydrolysis of PVA, blending modification and other methods, so that it can be dissolved quickly at room temperature.

[0055] The selection of the transfer substrate 100 has a significant impact on the success rate of the entire transfer process. In this application, the transfer substrate 100 is selected as a soft material, specifically soft PET / PI plastic. Soft materials possess good elasticity and flexibility, enabling them to closely conform to the minute undulations and unevenness of the battery cell surface, thereby ensuring that the conductive paste 400 can accurately replicate the preset grid pattern during the transfer process. The soft substrate can also evenly distribute pressure under pressure, allowing the conductive paste 400 to be evenly distributed on the substrate surface during the transfer process.

[0056] After the conductive paste transfer layer 200 is completely dry and cured, a grid pattern groove 300 with a specific shape and size is formed on its surface using a precision-designed mold and imprinting technology. The mold is typically made of a high-hardness, high-precision material to ensure the accuracy and consistency of the grooves during the imprinting process. During the imprinting process, the mold is in close contact with the conductive paste transfer layer 200, and by applying appropriate pressure and time, the conductive paste 400 is guided by the mold to form the desired grid pattern groove 300. This application uses a mold to form the grid pattern groove 300 on the conductive paste transfer layer 200 by imprinting. Compared with photolithography or etching processes, using a mold for imprinting can greatly simplify the production process. It eliminates the need for complex chemical treatment steps; the grid pattern can be formed solely through physical means. The mold imprinting process is highly efficient and fast, allowing for the production of grid patterns for a large number of solar cells in a short time, which significantly improves production efficiency.

[0057] Please refer to Figures 2 and 3. Figure 2 is a schematic diagram of the distribution of the grid lines in the battery cell in an embodiment of this application. The shape and distribution of the grid lines in the final battery cell can be adjusted according to the design. For example, the front grid lines include the main grid and the fine grid, while the back grid lines only include the main grid. Figure 3 is a cross-sectional schematic diagram of the shape of the grid lines in an embodiment of this application. Using the imprinting method of this application, the shape of the grid line 500 electrode can be changed by changing the shape of the imprinting template. For example, isosceles triangle, rectangle, isosceles trapezoid, ellipse, hexagon, right trapezoid, etc. can be selected.

[0058] In the manufacturing process of photovoltaic cells, the design and fabrication of the grid pattern are crucial, directly affecting the current collection efficiency of the cell. The grid pattern includes a first grid pattern with a groove depth ranging from 10-50 μm and a width ranging from 50-1000 μm, and a second grid pattern with a groove depth ranging from 5-15 μm and a width ranging from 3-50 μm. By precisely controlling the design of the imprinting mold and parameters during the imprinting process (such as pressure, time, and temperature), the method of this application can produce fine grid lines 500 with a groove depth of only 5-15 μm and a width of only 3-50 μm. The realization of these fine grid lines 500 allows the cell to maintain sufficient current collection capacity while significantly reducing light obstruction by the grid lines 500, thereby improving photoelectric conversion efficiency. Compared to screen printing, this application enables dimensional control and manufacturing of the fine grid lines 500.

[0059] In the manufacturing process of this application, filling the grid pattern grooves 300 with conductive paste 400 is a crucial step, directly affecting the efficiency and stability of current transmission in the solar cell. This step can be finely divided into two sub-steps: First, a layer of conductive paste 400 is uniformly applied to the grid pattern grooves 300 formed by embossing; then, using a scraper or similar tool, excess conductive paste 400 is scraped off from the edges and surface of the grooves with precise angle and force. In other words, the step of filling the grid pattern grooves 300 with conductive paste 400 includes applying conductive paste 400 to the embossed grid pattern grooves 300 and scraping off excess conductive paste 400. By uniformly applying conductive paste 400 to the grid pattern grooves 300, it can be ensured that each groove is fully filled, thereby forming a good conductive channel. Precise filling helps reduce the loss of raw materials during the manufacturing process and can avoid failures such as grid wire breakage.

[0060] In the heat transfer process, the selection of temperature, pressure, and time is crucial. This application selects a temperature range of 100-180℃, an applied pressure range of 5-15MPa, and a duration range of 2-10 minutes during transfer. These parameters ensure good adhesion between the transfer material (such as heat transfer film) and the transfer substrate 100, while preventing material deformation due to excessively high temperatures. Precise control of temperature, pressure, and duration ensures the accuracy and integrity of the transferred pattern. By optimizing process parameters while maintaining transfer quality, the production cycle can be shortened and production efficiency improved.

[0061] To further control the shape and size of the grid lines 500, the process of transferring the conductive paste 400 within the grid line pattern groove 300 to the front and back of the battery cell includes a two-stage process. This process involves first removing the transfer substrate 100, and then removing the conductive paste transfer layer 200 by liquid dissolution. First, the transfer substrate 100 carrying the conductive paste 400 is removed. Then, a liquid dissolution method is used to gently and effectively remove the conductive paste transfer layer 200 covering the grid line pattern. This process ensures the integrity and positioning accuracy of the conductive paste 400 pattern, avoiding possible displacement or damage in subsequent processing.

[0062] Please refer to Figures 4 and 5. In addition, this application also provides a battery cell grid line preparation apparatus, which can realize the aforementioned battery cell grid line preparation method in a complete set of equipment, improve the integration and automation level of the battery cell production line, specifically including: a transfer substrate 100, which serves as the starting carrier for the transfer of conductive paste 400, and is designed with a high-precision and high-wear-resistant surface, on which a conductive paste transfer layer 200 is prepared to ensure uniform coating and accurate transfer of the paste.

[0063] The coating component 210 is used to coat the conductive paste transfer layer 200 onto the transfer substrate 100 using precision coating techniques such as spraying, roller coating, or slot coating to uniformly coat a layer of conductive paste transfer layer 200 onto the transfer substrate 100. The hot pressing component 310 is used to form grid pattern grooves 300 on the conductive paste transfer layer 200. By precisely controlling the temperature and pressure, fine grid pattern grooves 300 are pressed onto the conductive paste transfer layer 200. This process ensures the accuracy and consistency of the grid line 500 structure.

[0064] The coating component 410 is used to fill the grid pattern grooves 300 with conductive paste 400. The conductive paste 400 is initially filled into the formed grid pattern grooves 300. The main material of the conductive paste 400 is typically silver paste, as silver has excellent conductivity and chemical stability, making it an ideal choice for preparing high-efficiency photovoltaic cell grids. However, with continuous technological advancements and cost considerations, conductive pastes 400 formed from other components, such as copper paste or aluminum paste, can also be selected.

[0065] The scraping component 420 is used to scrape and remove excess conductive paste 400. Using a precision scraper or similar tool, excess metal paste is scraped and removed to ensure that the conductive paste 400 in the groove is completely filled and there is no excess paste outside the groove, thereby ensuring that the size of the grid line 500 after transfer is controllable and the edges are clean.

[0066] The transfer component 600 is used to bond the conductive paste transfer layer 200 to the surface of the battery cell. It transfers the conductive paste 400 in the grid pattern groove 300 to the surface of the battery cell. Through precise alignment and appropriate pressure, the metal paste transfer layer is tightly bonded to the surface of the battery cell. The transfer component 600 is mainly a moving component. It moves the transfer substrate 100 to bond the conductive paste transfer layer 200 to the surface of the battery cell. The moving methods include translation, up and down movement, rotation, etc. It can also provide controllable pressure and temperature. Any method and component that can bond the conductive paste transfer layer 200 to the surface of the battery cell can be considered as the transfer component 600.

[0067] The conveying mechanism is used to transport the battery cells to the station where the transfer unit 600 is located. It is designed with an efficient and stable conveying path, enabling accurate transport of the battery cells (or processed battery cells) to the station where the transfer unit 600 is located, ensuring the continuity and efficiency of the entire production process. The main method used can be a conveying method compatible with existing battery cell production lines, such as belt conveyor for single cells.

[0068] The system includes a transfer substrate 100 corresponding to the front and back grid lines, a coating component 210, a hot-pressing component 310, a slurry coating component 410, a leveling component 420, and a transfer component 600, which simultaneously transfer conductive paste 400 onto the front and back of the solar cell. For the front and back of the solar cell, there is an identical independent component system that performs the back grid line transfer operation using the same process. These two systems are not only independent but also highly collaborative, ensuring that the front and back grid line 500 transfers are performed simultaneously without interference. Through parallel processing design, the front and back grid line transfers of the solar cell can be performed simultaneously, significantly shortening the production cycle. The equipment can make better use of vertical space, resulting in more efficient use of factory space and equipment resources. Furthermore, the number and combination of workstations in this application are not specifically limited; the specific arrangement can include multiple workstations, which can be integrated with other automated equipment in the production line, thus achieving seamless integration without adjusting the existing layout of the automated equipment. The device of this application is equipped with two independent but synchronously operating transfer substrates 100, coating components 210, hot pressing components 310, paste coating components 410, scraping components 420 and transfer components 600 corresponding to the front and back of the battery cell, respectively, and can simultaneously complete the transfer of conductive paste 400 on the front and back of the battery cell in a single device.

[0069] Please refer to Figure 4, which is a schematic diagram of the structure of a battery cell grid line preparation apparatus in one embodiment of this application. The transfer substrate 100 is a cylindrical roller, with the coating component 210, the hot-pressing component 310, the slurry coating component 410, and the leveling component 420 arranged sequentially on the roller along the rotation direction of the roller. In this embodiment, the cylindrical roller design of the transfer substrate 100 utilizes the continuous rotation characteristics of the roller to arrange the components (coating component 210, hot-pressing component 310, slurry coating component 410, and leveling component 420) used in a series of key processing steps sequentially and compactly along the circumference of the roller, following the rotation direction of the roller. In the figure, A represents the rotation direction, and B represents the battery cell transport direction. The coating component 210 first contacts the roller-type transfer substrate 100, and is responsible for uniformly coating a thin layer of conductive paste 400 on its surface. A slot coating method can be selected. Next, the hot-pressing component 310 uses preset temperature and pressure conditions to precisely form the required grid pattern grooves 300 on the conductive paste 400 layer. This process requires high precision and stability. This component can also use a roller method, pressing the surface of two rollers at the same surface speed. By changing the template in the hot-pressing component 310, the structural parameters such as electrode pattern and size can be changed, making it suitable for different battery cell designs and exhibiting good compatibility. Subsequently, the coating component 410 fills these fine grooves with additional conductive paste 400, and the scraping component 420 scrapes away excess paste with set force and angle, making the grid pattern clearer and more complete. Finally, the transfer component 600 is used to adhere the conductive paste transfer layer 200 to the surface of the battery cell, transferring the conductive paste 400 within the grid pattern grooves 300 to the surface of the battery cell. In this method, the roller-type transfer substrate 100 only needs to rotate, without needing to move up and down. The continuous rotation design of the roller-type transfer substrate 100 allows for seamless connection between each processing step. By compactly arranging the components along the circumference of the roller, it effectively saves floor space, making the production line layout more compact and reasonable, while also facilitating daily maintenance and operation.

[0070] Please refer to Figure 5, which is a schematic diagram of the structure of a battery cell grid line fabrication apparatus in another embodiment of this application. In this embodiment, the transfer substrate 100 has a polygonal cross-section and includes multiple planes, which are sequentially arranged on the surface of the transfer substrate 100 in the order of coating component 210, hot pressing component 310, slurry coating component 410, and leveling component 420. The order is the same as the rotation direction of the transfer substrate 100. In the figure, A is the rotation direction and B is the battery cell transport direction. The transfer substrate 100 is designed with a polygonal cross-section structure, which can make full use of the geometric characteristics of polygons. The polygonal cross-section transfer substrate 100 includes multiple planes, which provide a stable working surface for each processing component. It can also continuously adjust the working position by rotation, ensuring the continuity and stability of the processing.

[0071] Specifically, the coating component 210, hot pressing component 310, slurry coating component 410, and leveling component 420 are sequentially arranged on each plane of the transfer substrate 100, with their arrangement consistent with the direction of rotation of the transfer substrate 100, ensuring smooth connection and operation of the processing steps. The coating component 210 first acts on one plane of the transfer substrate 100, uniformly coating a layer of conductive slurry transfer layer 200. At the next station, the hot pressing component 310 precisely presses the grid pattern on the second plane. By changing the template in the hot pressing component 310, the structural parameters such as electrode pattern and size can be changed, making it suitable for battery cells of different designs. The slurry coating component 410 fills the grooves of the grid pattern with conductive slurry 400 on the third plane. The leveling component 420 removes excess slurry on the fourth plane with a fine scraping action. The transfer station corresponds to the fifth plane. This arrangement allows five operations to be performed at five different locations simultaneously, forming good continuity. The design of the polygonal cross-section transfer substrate 100 allows each processing step to be performed simultaneously on different planes. Each processing component is correspondingly positioned on a specific plane of the transfer substrate 100, ensuring the stability and consistency of the processing. In addition, the polygon is preferably hexagonal, which can provide an extra workstation position to add other steps (such as cleaning) or facilitate maintenance.

[0072] In a further embodiment, at the coating station, the surface of the transfer substrate 100 is horizontal. In this state, the flat-plate coating method ensures uniform paste distribution and facilitates the recovery of excess paste, thereby stably preparing a 20±2μm thick PVA flexible film on the carrier. On the horizontally positioned transfer substrate 100, the flat-plate coating method is used to uniformly distribute the paste. In this horizontal state, the paste can be more evenly and stably distributed on the transfer substrate 100, avoiding paste flow and accumulation caused by gravity or tilt angle, thus ensuring the uniformity and consistency of the conductive paste 400.

[0073] Because polygons have planes, the distances from each position to the center of the rotation axis are not consistent. Therefore, this method also includes a moving component that synchronously adjusts the height of the upper and lower transfer substrates 100 of the battery cell. By adjusting the relative height of the rotation axis center, the upper and lower transfer substrates 100 apply pressure and transfer the battery cell. Other components located around the battery cell can also be equipped with corresponding moving components as needed to create space for the movement of the transfer substrates.

[0074] In conventional rotary screen printing, only one side of the grid lines 500 can be produced. Furthermore, due to size differences, the main grid and sub-grids require separate screen printing using different screens, and an additional cell flipping structure is also needed. This application eliminates the rotary structure, allowing it to work only with a horizontal transport device and with related components arranged in the vertical space. This enables simultaneous imprinting of both the upper and lower surfaces, allowing for the simultaneous production of front and back grid line electrodes, particularly all grid lines (including main and sub-grids) on both the front and back of the cell. In this specific implementation, a transfer workpiece can be used as an auxiliary component to place the cell onto the transfer substrate 100 below. After imprinting, a suction cup is used to reposition the cell onto a transport component, such as a conveyor belt, for transport to subsequent stations, such as suction cups. Buffer stations, including upstream and downstream buffer stations, can be provided.

[0075] Specifically, it also includes a cleaning component, which is installed before the coating station to clean the surface of the transfer substrate 100. In the cleaning station, physical brushing methods can be used to remove residues from the surface of the transfer substrate 100. The addition of the cleaning station is an important supplement and optimization to the coating process, fundamentally improving the quality and efficiency of the coating operation and laying the foundation for producing high-quality products.

[0076] Specifically, it also includes a drying component 610, a cleaning component 620, and a sintering component 630. The drying component 610 is used to dry the conductive paste 400, the cleaning component 620 is used to dissolve and remove the conductive paste transfer layer 200 using a solution method, and the sintering component 630 is used to sinter the conductive paste 400. Through these supplementary components, the entire process is fully integrated.

[0077] In addition, this application also provides a battery cell, including grid lines 500 on the front and back sides of the battery cell, which are prepared by the aforementioned battery cell grid line preparation method.

[0078] A specific embodiment is described below to illustrate the technical solution of this application. In this specific embodiment, PVA is used as the material for the conductive paste transfer layer. Silver paste is selected as the conductive paste. Based on the understanding of photovoltaic silver paste and the research on the new hydrogen bonding mechanism in polyvinyl alcohol (PVA) material, it has been found that PVA has no reactivity with silver paste adhesives and solvents and has weak adhesion, making it an ideal carrier for transferring silver paste. Referring to Figure 1, a layer of PVA is coated on soft PET / PI plastic and dried at 100-150℃ to obtain a 10-50μm PVA coating. Using imprinting technology, electrode pattern grooves with a depth of 10-50μm and a width of 50 to 500μm required for the main grid lines are pressed out using a custom mold in a precision hot press device. Fine grid grooves with a height of 10-15μm and a width of 5μm are also pressed out in the direction perpendicular to the fine grid. On the other hand, electrode pattern grooves with a depth of 10-50μm and a width of 50 to 500μm required for the back grid lines are pressed out using another mold in a precision hot press device. Simultaneously, silver paste is applied to the two hot-pressed PVA grooves, ensuring they are tightly filled. Excess silver paste is scraped off, and the paste is then smoothly applied to the solar cell, adhering to one side of the front / side grid lines and the other side to the back grid lines. Due to the adhesion between the photovoltaic silver paste and the solar cell, the transfer process is performed at 100-180℃ with a pressure of 5-15 MPa for 2-10 minutes. The two PI films are then peeled off, allowing the silver paste and PVA coating to adhere tightly to the solar cell. The PVA coating is then dissolved by frequent warm water washing, successfully transferring the silver paste onto the solar cell. After high-temperature sintering, the silver paste forms the specific patterned electrode grid lines on the front and back sides.

[0079] Based on the embossing and PVA transfer processes, the process further adopts simultaneous transfer on the upper and lower parts of the battery cell, achieving the three steps of screen printing in one step. This greatly improves production efficiency and reduces production costs. The transfer film process is very simple, and transferring it onto the battery cell is also very easy, which is conducive to industrial production.

[0080] Imprint lithography offers several advantages: it enables nanoscale pattern fabrication with higher resolution and precision than traditional methods, contributing to improved photovoltaic cell performance and efficiency. It exhibits excellent reproducibility, stably producing high-quality electrode patterns and ensuring the stability and reliability of photovoltaic cells. Compared to other micro / nano fabrication technologies, imprint lithography is less expensive and suitable for large-area fabrication, helping to reduce production costs and improve efficiency. It can fabricate various functional patterns, such as optical structures and surface-enhanced Raman scattering structures, providing more possibilities for optimizing photovoltaic cell performance. Imprint lithography typically does not require organic solvents, resulting in lower environmental impact, aligning with green manufacturing requirements, and promoting sustainable development. By highlighting these advantages, the innovativeness and practicality of the technology can be further emphasized, demonstrating its superiority and potential in photovoltaic cell electrode fabrication.

[0081] First, this high-resolution composite silver paste transfer film fabrication process based on imprintable polymeric material carriers (such as PVA carriers) can achieve micron- or even nanometer-scale electrode patterns, offering higher resolution compared to traditional screen printing techniques, thus contributing to improved photovoltaic cell performance and efficiency. Using PVA carriers as the transfer substrate results in a relatively simple and convenient fabrication process, suitable for large-scale production. PVA materials are also relatively inexpensive, and this method reduces waste and material waste, thereby lowering production costs.

[0082] PVA exhibits no reactivity with silver paste adhesives and solvents and has weak adhesion, making it an ideal carrier for transferring silver paste and facilitating close adhesion between the silver paste and the solar cells. Compared to screen printing, this method offers higher production efficiency, meeting the demands of large-scale production and improving productivity. The PVA carrier can be easily dissolved by warm water washing, making it environmentally friendly and sustainable, thus reducing environmental impact.

[0083] As described above, this application proposes a novel method for fabricating grid lines in solar cells. This method reduces material consumption through precise transfer printing technology, thereby effectively reducing production costs and successfully achieving stable fabrication of grid lines in small-sized solar cells. The specific steps include: First, conductive paste transfer layers corresponding to the front and back sides of the solar cell are fabricated on a transfer substrate. These transfer layers contain grooves with grid line patterns. The conductive paste is uniformly filled into the grooves, and unnecessary paste accumulation is avoided by controlling the filling method. Next, the conductive paste transfer layers on the front and back sides are precisely adhered to the front and back sides of the solar cell, respectively. By simultaneously applying appropriate pressure and temperature, the conductive paste in the grid line pattern grooves is transferred to the surface of the solar cell. Finally, the transferred conductive paste is transformed into front and back grid lines with good conductivity and stability through heat treatment or other methods.

[0084] This application employs a unique simultaneous top-and-bottom transfer technology, which not only achieves synchronous transfer of the grid pattern on both the front and back of the solar cell, but also balances the force distribution, avoids microcracks in the solar cell, improves the tightness of the grid lines adhering to the cell surface, and enhances current collection efficiency. In the fabrication of the conductive paste transfer layer, this application selects PVA as the main material; its solubility allows the silver paste to be successfully transferred onto the solar cell, while the hot-press transfer technology ensures a tight bond between the silver paste and the solar cell.

[0085] Furthermore, this application also provides a solar cell grid line fabrication apparatus. This apparatus can realize the aforementioned solar cell grid line fabrication method in a single complete machine, improving the integration and automation level of the solar cell production line. The apparatus includes a transfer substrate, a coating component, a hot pressing component, a slurry coating component, a leveling component, a transfer component, and a transport mechanism, etc., and can simultaneously process the front and back sides of the solar cell, significantly shortening the production cycle. The transfer substrate is designed with a circular roller or polygonal cross-section structure, allowing for seamless connection between each processing step and effectively saving floor space. In summary, the solar cell grid line fabrication method and apparatus of this application have significant advantages such as significantly reducing material consumption, improving production efficiency, and ensuring grid line quality and stability, providing a new solution for the fabrication of photovoltaic solar cell grid lines.

[0086] The above is only one specific implementation of this application, and any other improvements made based on the concept of this application shall be considered within the scope of protection of this application.

Claims

1. A method for fabricating grid lines in a solar cell, characterized in that, include: Conductive paste transfer layers corresponding to the front and back grid lines are respectively fabricated on the transfer substrate, and the conductive paste transfer layers include grid line pattern grooves. The grooves of the grid pattern are filled with conductive paste; The conductive paste transfer layer corresponding to the front grid line is bonded to the front of the battery cell, and the conductive paste transfer layer corresponding to the back grid line is bonded to the back of the battery cell. Pressure is applied to both the front and back of the battery cell simultaneously to transfer the conductive paste in the groove of the grid pattern to the front and back of the battery cell. The transferred conductive paste is converted into front and back grid lines.

2. The method for preparing battery cell grid lines according to claim 1, characterized in that, The process of creating the conductive paste transfer layer involves coating a water-soluble polymer material onto the transfer substrate, drying it, and controlling the thickness to be within the range of 10-50 μm.

3. The method for preparing battery cell grid lines according to claim 2, characterized in that, The transfer substrate is a soft material.

4. The method for preparing battery cell grid lines according to claim 2, characterized in that, A grid pattern groove is formed on the conductive paste transfer layer by means of an embossing method using a mold.

5. The method for preparing battery cell grid lines according to claim 4, characterized in that, The gate pattern includes a first gate pattern with a groove depth in the range of 10-50 μm and a width in the range of 50-1000 μm, and a second gate pattern with a groove depth in the range of 10-15 μm and a width in the range of 5-50 μm.

6. The method for preparing battery cell grid lines according to claim 4, characterized in that, The step of filling the grid pattern groove with conductive paste includes applying conductive paste to the grid pattern groove formed by embossing and scraping off excess conductive paste.

7. The method for preparing battery cell grid lines according to claim 1, characterized in that, During the transfer process, the temperature should be selected within the range of 100-180℃, the applied pressure within the range of 5-15MPa, and the duration within the range of 2-10min.

8. The method for preparing battery cell grid lines according to claim 1, characterized in that, The step of transferring the conductive paste in the groove of the grid pattern to the front and back of the battery cell includes first removing the transfer substrate, and then removing the conductive paste transfer layer by liquid dissolution.

9. A solar cell grid line fabrication apparatus, characterized in that, include: Transfer substrate; A coating component for coating a conductive paste transfer layer onto the transfer substrate; A hot-pressing component is used to form grid pattern grooves on the conductive paste transfer layer; A slurry coating component for filling conductive slurry into the grooves of the grid pattern; The scraping component is used to scrape and remove excess conductive paste; A transfer component is used to attach the conductive paste transfer layer to the surface of the battery cell and transfer the conductive paste in the groove of the grid pattern to the surface of the battery cell. The transfer mechanism is used to transfer the battery cells to the station where the transfer unit is located; The system includes a transfer substrate corresponding to the front grid lines and the back grid lines, a coating component, a hot pressing component, a slurry coating component, a scraping component, and a transfer component, which simultaneously transfer conductive paste to the front and back of the battery cell.

10. The solar cell grid line fabrication apparatus according to claim 9, characterized in that, The transfer substrate is a cylindrical roller, and the coating component, the hot pressing component, the slurry coating component, and the leveling component are arranged on the cylindrical roller in the order of rotation of the roller.

11. The apparatus for fabricating solar cell grid lines according to claim 9, characterized in that, The transfer substrate has a polygonal cross-section, including multiple planes, which are sequentially arranged on the surface of the transfer substrate in the order of coating component, hot pressing component, slurry coating component, and scraping component, with the order being the same as the rotation direction of the transfer substrate.

12. The apparatus for fabricating solar cell grid lines according to claim 11, characterized in that, It also includes a moving component that synchronously adjusts the height of the upper and lower transfer substrates of the battery cell.

13. The apparatus for fabricating solar cell grid lines according to claim 9, characterized in that, It also includes a cleaning component, which is installed before the coating station to clean the surface of the transfer substrate.

14. The apparatus for fabricating solar cell grid lines according to claim 9, characterized in that, It also includes a drying component, a cleaning component, and a sintering component. The drying component is used to dry the conductive paste, the cleaning component is used to dissolve and remove the conductive paste transfer layer using a solution, and the sintering component is used to sinter the conductive paste.

15. A solar cell, comprising grid lines on the front and back sides, characterized in that, The grid lines on the front and back sides are prepared by the method for preparing battery grid lines according to any one of claims 1-8.

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