Multi-layer structure composite transfer printing film, manufacturing method and application of multi-layer structure composite transfer printing film

Abstract

The invention relates to a multi-layer structure composite transfer printing film, a manufacturing method and application of the multi-layer structure composite transfer printing film. The transfer film comprises a patterned layer, a reinforcing layer and a demolding layer, the patterned layer is provided with grooves corresponding to the grid lines; the reinforcing layer continuously covers the surfaces of the patterned layer and the grooves and is used for mechanically reinforcing and inhibiting thermal deformation of the patterned layer; the demolding layer covers the surface of the reinforcing layer, the reinforcing layer physically isolates the demolding layer from the patterned layer, and stable demolding can be achieved after high-temperature transfer printing. Optionally, the membrane structure further comprises a self-healing glue layer and a supporting layer which are arranged on the back surface of the patterned layer. The manufacturing method comprises the following steps: coating a PVA (Polyvinyl Alcohol) solution on the surface of a mold with a convex structure and curing to form a patterned layer; and forming a reinforcing layer and / or a demolding layer on the surface of the patterned layer after demolding. According to the photovoltaic cell grid line manufacturing method, the transfer printing film is utilized, and grid line preparation is completed through the steps of slurry filling, hot pressing transfer printing, film tearing and sintering. According to the transfer printing scheme, the structure is simplified, and the transfer printing precision and the demolding performance are improved.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a multilayer composite transfer film, its fabrication method, and its application. Background Technology

[0002] In the field of photovoltaic cell manufacturing, high-precision cell grid lines are prepared using conductive pastes (such as silver paste and silver-coated copper paste). To reduce pollution and energy consumption in wet processes, dry transfer printing technology has gained attention as an alternative. Among these advancements, achieving fully dry fabrication using a transfer-and-peel method is a recent technological breakthrough. In this approach, a typical multilayer composite transfer film structure includes a polyimide (PI) support layer, a self-healing adhesive layer, and a patterned polyvinyl alcohol (PVA) layer.

[0003] However, this existing structure still faces some problems in practical applications. First, due to the high viscosity of the adhesive layer itself, wrinkles and bubbles are easily introduced when it is bonded to the solar cell over a large area (e.g., the number of bubbles is more than 5 per square meter as observed under a microscope). These interface defects can lead to grid line breaks during subsequent transfer processes, with a grid breakage rate that may reach 8% or higher. Second, the presence of the PI support layer and the adhesive layer increases the total thickness of the composite film (e.g., greater than 100 micrometers), which reduces heat conduction efficiency and affects process uniformity during hot pressing transfer. Furthermore, if the PI layer and adhesive layer are removed to simplify the structure and improve heat conduction, and only a thinner (e.g., less than 25 micrometers thick) pure PVA patterned layer is used, its insufficient mechanical properties become apparent. Its tensile strength is significantly reduced, and during the film peeling process, the pure PVA layer may undergo deformation of more than 15%, thereby affecting the morphology of the transferred grid lines and reducing the final retention rate of the grid lines on the silicon wafer. Furthermore, after the high-temperature transfer process, the force between the composite film and the silicon wafer surface is relatively large, making peeling difficult and increasing the difficulty of large-scale industrial application of this technology. Summary of the Invention The purpose of this application is to provide an improved multilayer composite transfer film, optimizing the dry transfer process for photovoltaic cell grid line fabrication, simplifying the film structure, reducing interface defects, and simultaneously improving the mechanical properties and release effect of the transfer film. This purpose is achieved through the following technical solution: the multilayer composite transfer film of this application includes a patterned layer, a reinforcing layer, and a release layer. The patterned layer includes grooves corresponding to the grid lines of the battery cells; The reinforcement layer is continuously formed on the surface of the patterned layer and the groove; The release layer covers the surface of the reinforcing layer; The reinforcement layer isolates the release layer from the patterning layer.

[0004] In one embodiment, the invention further includes a healing adhesive layer and a support layer, the healing adhesive layer being formed on the side of the patterned layer opposite to the reinforcing layer, and the support layer being formed on the side of the healing adhesive layer opposite to the patterned layer.

[0005] In one embodiment, the thickness of the enhancement layer is in the range of 1 nm to 100 nm, and the thickness of the patterned layer is in the range of 20 μm to 70 μm.

[0006] In one embodiment, the reinforcing layer is made of SiO2.

[0007] In one embodiment, the enhancement layer includes two or more sub-enhancement layers.

[0008] In one embodiment, the enhancement layer further includes a transition layer.

[0009] This application also provides a method for manufacturing a multilayer composite transfer film, including: Provide a mold, which includes protrusions corresponding to the grid lines of the solar cell; A PVA solution is applied to a mold including raised sections, and the PVA solution is cured to form a patterned layer. Demolding: Removing the patterned layer from the mold. After demolding, a reinforcing layer and / or a release layer are formed on the surface of the patterned layer; A multi-layered composite transfer film is formed, comprising a patterning layer, a reinforcement layer, and a release layer.

[0010] In one embodiment, the steps of applying a self-healing adhesive layer and a support layer are also included.

[0011] In one embodiment, the reinforcing layer is deposited using PVD after demolding or the reinforcing layer is formed on the mold before applying the PVA solution.

[0012] This application further provides a method for fabricating photovoltaic cell grid lines, which uses the aforementioned multilayer composite transfer film and includes the following steps: A conductive paste is applied to the patterned layer of a multilayer composite transfer film and then smoothed out. A multi-layer composite transfer film, including conductive paste, is placed on the battery cell. The conductive paste is transferred to the surface of the battery cell by hot pressing transfer. The conductive paste on the surface of the battery cell is dried and sintered.

[0013] Compared with the prior art, this application has the following beneficial effects: This application forms a simplified film structure by directly bonding an enhancement layer with a thickness of 1nm-100nm onto the patterned layer. This structure allows the elimination of the traditional polyimide support layer and self-healing adhesive layer, and can eliminate interface bubbles and wrinkles that may be caused by adhesive layer bonding, thereby helping to reduce the breakpoint rate of gate line transfer and improving the heat conduction efficiency during hot pressing transfer.

[0014] The reinforcing layer is continuously formed on the entire surface of the patterned layer and its grooves, and is bonded to the patterned layer. This enhances the overall mechanical properties of the composite film, increases the tensile strength of the patterned layer, and reduces the deformation rate during the film removal process. This helps maintain the morphology of the transfer gate lines and improves the gate line retention rate. By physically isolating the release layer from the patterned layer through the reinforcing layer, the adverse effects of thermal softening of the patterned layer on the function of the release layer during high-temperature transfer are mitigated. This allows the release layer to maintain more stable low surface energy characteristics at high temperatures, which helps reduce the peel force between the film and the silicon wafer after transfer, making the film removal operation easier, reducing film damage, and increasing the process window and the number of times the film can be reused.

[0015] Regarding the manufacturing method, the patterned layer (PVA solution) can be directly coated and cured in the mold, and a reinforcing layer that is tightly bonded to the patterned layer can be combined with it. This helps to ensure the uniformity and adhesion of the reinforcing layer on the surface of the micron-level grooves, providing a foundation for obtaining a transfer film with high precision and consistent mechanical properties. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a multilayer composite transfer film in one embodiment of this application; Figure 2 This is a schematic diagram of the manufacturing process of a multilayer composite transfer film in one embodiment of this application; Figure 3 This is a schematic diagram of the steps in the method for manufacturing a multilayer composite transfer film according to one embodiment of this application; Figure 4 This is a schematic diagram of a photovoltaic cell grid line fabrication method in one embodiment of this application; Figure 5 This is a schematic diagram of the steps in the photovoltaic cell grid line fabrication method according to one embodiment of this application.

[0017] Explanation of reference numerals in the attached drawings: 100, patterned layer; 110, groove; 120, mold; 200, reinforcement layer; 300, release layer; 400, healing adhesive layer; 500, support layer; 600, conductive paste; 700, battery cell. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Existing dry transfer composite film structures employing a PI support layer, a self-healing adhesive layer, and a patterned PVA layer suffer from numerous interface defects, structural redundancy leading to low heat conduction efficiency, and insufficient mechanical properties of the PVA layer itself resulting in large tear deformation and difficulty in peeling at high temperatures. To address these issues, this application proposes an improved multilayer composite transfer film, its fabrication method, and its applications. This application optimizes the film structure, enhances mechanical properties, and improves the demolding effect by introducing a continuous reinforcing layer disposed between the patterned layer and the release layer. The following detailed description, in conjunction with specific embodiments, details different structural configurations of the proposed transfer film (e.g., embodiments including or excluding traditional support and adhesive layers), its specific fabrication process, and the method for fabricating photovoltaic cell grid lines using this transfer film.

[0022] Please see Figure 1In a preferred embodiment of this application, the multilayer composite transfer film includes a patterned layer 100, a reinforcing layer 200, and a release layer 300. The patterned layer 100 includes grooves 110 corresponding to the grid lines of the battery cell 700. The reinforcing layer 200 is continuously formed on the surface of the patterned layer 100 and the grooves 110. The release layer 300 covers the surface of the reinforcing layer 200, wherein the reinforcing layer 200 isolates the release layer 300 from the patterned layer 100.

[0023] The patterned layer 100 of this application is typically made of polyvinyl alcohol (PVA) and has micron-sized grooves 110 that complement the grid pattern of the target solar cell 700. These grooves are used to form and accommodate conductive paste 600 (such as silver paste). If a thin pure PVA layer is used alone, its mechanical strength is insufficient, and it is prone to excessive deformation during the subsequent film removal process, thereby affecting the morphological accuracy of the transferred grid lines. This application provides a reinforcement layer 200 that is directly and continuously formed on the entire surface of the patterned layer 100 and its grooves 110. The reinforcement layer 200 can be made of inorganic nanomaterials, such as silicon dioxide (SiO2) deposited by physical vapor deposition (PVD). The reinforcement layer 200 and the patterned layer 100 (such as PVA) are combined to form an organic-inorganic composite structure, which improves the macroscopic mechanical properties of the composite film, such as increasing tensile strength and reducing the deformation rate during the film removal process, thus helping to maintain the fidelity of the transferred pattern and the grid line retention rate.

[0024] The reinforcing layer 200 physically isolates the release layer 300 from the patterned layer 100 below. Under high-temperature transfer conditions, the PVA substrate may soften, causing the release agent directly attached to it to lose its function or change its interface state, thereby increasing the tear resistance. In this application, the reinforcing layer 200 (such as a dense nano-SiO2 layer) serves as an isolation and stabilizing interface, providing the release layer 300 with an attachment substrate that is relatively independent from the easily deformable PVA substrate. On the other hand, it can maintain structural rigidity at high temperatures, allowing the release layer 300 (such as an organic compound layer containing fluorinated silanes) covering the surface of the reinforcing layer 200 to maintain its low surface energy characteristics over a wider temperature range, achieving stable release function and helping to obtain lower tear force after high-temperature transfer.

[0025] The technical solution of this application may also include a traditional support structure. Specifically, in the embodiments, the multilayer composite transfer film further includes a healing adhesive layer 400 and a support layer 500. The healing adhesive layer 400 is formed on the surface of the patterned layer 100 opposite to the reinforcing layer 200, i.e., the back side of the patterned layer 100. The support layer 500 is further formed on the side of the healing adhesive layer 400 opposite to the patterned layer 100, typically serving as the outermost basic support. The support layer 500 may be made of polyimide (PI) film, which can provide additional mechanical support and dimensional stability for the entire transfer film, especially when dealing with large-area film materials or coping with strong external tension, helping to reduce the overall deformation risk of the film material. The healing adhesive layer 400, disposed between the patterned layer 100 and the support layer 500, uses an adhesive layer with certain self-healing properties to absorb or compensate for minor interface unevenness during the lamination process, promoting a tight bond between the patterned layer 100 and the rigid support layer 500.

[0026] The introduction of this healing adhesive layer 400 and support layer 500 also brings corresponding technical trade-offs. For example, the addition of the adhesive layer may introduce the risk of interface bubbles or wrinkles due to high viscosity or curing shrinkage, which is considered one of the potential factors leading to grid line breakage (grid breakage rate ≥8%). At the same time, the addition of support layer 500 and adhesive layer inevitably increases the total thickness of the composite film (e.g., total thickness > 100 μm), which may reduce the heat conduction efficiency in the subsequent hot pressing transfer process to some extent. Therefore, this application includes the structure containing this healing adhesive layer 400 and support layer 500 as an optional embodiment to adapt to different process conditions and application scenarios with different requirements for the mechanical strength of the film material.

[0027] The thickness of the patterned layer 100 is set between 20 micrometers and 70 micrometers, primarily to balance pattern formability, mechanical support, and process applicability. When the thickness of the patterned layer 100 is less than 20 micrometers, its structure may become too thin and undergo excessive deformation during subsequent film removal processes, affecting the transfer accuracy of the supported grid pattern. Setting the upper limit to 70 micrometers is to prevent excessive thickness of this layer, thereby helping to control the overall thickness of the composite film, providing sufficient mechanical support, and improving the heat transfer efficiency during the transfer process. The thickness of the reinforcing layer 200 is limited to the nanoscale range of 1 nanometer to 100 nanometers, continuously covering the patterned layer 100 and the surface of its grooves 110. This avoids the potential for brittleness introduced by an excessively thick inorganic layer, ensuring that the reinforcing layer 200 provides effective mechanical support and stable interface functions while maintaining the overall flexibility and process reliability of the composite film.

[0028] The reinforcing layer 200 described in this application is made of silicon dioxide (SiO2), which can be formed on the surface of the patterned layer 100 (such as PVA) using a magnetron sputtering method, for example, in physical vapor deposition (PVD), at low temperatures (e.g., ≤60°C). This low-temperature process condition is compatible with the thermal sensitivity of the PVA layer as a substrate (whose glass transition temperature is approximately 70°C), preventing softening and deformation of the substrate due to high temperatures, thus ensuring the morphological integrity of the precise microgrooves 110 on its surface. The formed nanoscale SiO2 layer is rich in hydroxyl groups (-OH) on its surface, which helps to form a good interfacial bond with the underlying PVA material, which also contains hydroxyl groups, through interactions such as hydrogen bonding, improving interlayer adhesion. This is the basis for achieving effective mechanical reinforcement. Under the high-temperature environment of the transfer process, the SiO2 reinforcing layer 200 can act as a rigid framework to suppress excessive thermal motion of the PVA molecular chains, thereby helping to maintain the overall dimensional stability and modulus of the composite film, which plays a role in reducing the high-temperature tearing force. Furthermore, the dense SiO2 layer also possesses certain barrier properties, reducing the penetration of ambient moisture into the PVA layer, thereby potentially improving the environmental stability of the transfer film during storage and use. Other metal oxides (such as Al2O3) are also used as materials for the reinforcing layer 200 due to their similar properties.

[0029] In some embodiments, the reinforcement layer 200 is configured to include two or more sub-reinforcement layers 200. The first sub-reinforcement layer 200 can be directly deposited on the surface of the patterned layer 100 (such as PVA). Its material selection or process parameters can prioritize good interfacial bonding with the underlying organic substrate. Plasma pretreatment or the introduction of specific transition elements (such as Cr, Ti) in the early stages of sputtering can be used to construct an interfacial transition sub-layer, enhancing adhesion to the PVA substrate and preventing the overall reinforcement layer 200 from peeling off. Based on this, the subsequently deposited second or more sub-reinforcement layers 200 may focus on achieving the main function, such as using SiO2 as the main material to provide the required mechanical modulus and thermal stability. This sub-layer combination of "transition layer + functional layer" can balance interfacial bonding reliability and bulk functional integrity without significantly increasing the total thickness. Furthermore, by alternating the deposition of different materials or adjusting deposition conditions (such as power and atmosphere), a multilayer sub-reinforcement layer 200 with a certain composition or structural gradient is formed. This helps to alleviate the internal stress caused by the large difference in thermal expansion coefficients between a single material and the substrate, improves the durability and reusability of the composite film, and enables the reinforcement layer 200 to more precisely adapt to the complex three-dimensional morphology of the patterned layer 100 microgrooves 110, ensuring uniform and firmly bonded coverage on both the groove walls and the groove bottom.

[0030] The reinforcement layer 200 employs a multi-layer sub-layer structure and can further encompass specific sub-layer configurations, namely, the reinforcement layer 200 also includes a transition layer. Since the patterned layer 100 (e.g., PVA) has a certain degree of chemical inertness, directly depositing functional inorganic reinforcement materials such as SiO2 on it may result in insufficient interfacial adhesion. This weak adhesion, under the mechanical stress of subsequent transfer printing, film removal, etc., may cause the reinforcement layer 200, or even the entire functional layer, to peel off from the substrate and fail. To solve this problem, a transition layer is introduced into the reinforcement layer 200 system. This transition layer can serve as the first sub-reinforcement layer 200 directly in contact with the patterned layer 100. Its material selection can prioritize substances with better compatibility or stronger interaction with the organic substrate, such as certain metallic elements (e.g., chromium, titanium) or their initial oxides. By first depositing an extremely thin (e.g., several nanometers thick) transition layer using physical vapor deposition (PVD), the chemical state and energy of the patterned layer 100 surface can be altered, providing a more active interface for the deposition of the host reinforcement layer 200 material (e.g., SiO2), thereby enhancing the bonding strength between the entire reinforcement layer 200 system and the patterned layer 100.

[0031] Please see Figure 2 , Figure 3 This application also provides a method for manufacturing a multilayer composite transfer film, including providing a mold 120, having protrusions on the mold 120 corresponding to the grid lines of the battery cell 700, coating the mold 120 with a PVA solution, curing the PVA solution to form a patterned layer 100, demolding, removing the patterned layer 100 from the mold 120, and after demolding, forming a reinforcing layer 200 and / or a release layer 300 on the surface of the patterned layer 100, thereby forming a multilayer composite transfer film including the patterned layer 100, the reinforcing layer 200, and the release layer 300.

[0032] This application also provides a manufacturing method corresponding to the aforementioned multilayer composite transfer film. The core steps can be either forming an organic patterned layer 100 first, followed by applying an inorganic reinforcing layer 200, or directly forming the reinforcing layer 200 on a mold first, followed by forming the organic patterned layer 100. Specifically, this includes: first, providing a mold 120 with corresponding grid line protrusions on its surface, and manufacturing based on the mold 120 including the protrusions. Alternatively, the organic patterned layer 100 can be formed first and demolded, followed by forming the reinforcing layer 200 via PVD. In another approach, the reinforcing layer 200 is directly fabricated on the raised surface of the mold 120; then, a polyvinyl alcohol (PVA) solution is coated onto the surface of the mold 120 covered with the reinforcing layer 200, and after curing, a patterned layer 100 is formed; subsequently, demolding is performed to separate the cured PVA patterned layer 100, along with the reinforcing layer 200 on its surface, from the mold 120; finally, a release layer 300 is formed on the surface of the exposed reinforcing layer 200 after demolding, thereby completing the preparation of the multilayer composite transfer film including the patterned layer 100, the reinforcing layer 200, and the release layer 300.

[0033] Since the reinforcing layer 200 (e.g., a nano-SiO2 layer formed by physical vapor deposition (PVD)) is directly constructed on the raised surface of the mold 120, it ensures that the lower surface of the reinforcing layer 200 can perfectly replicate the geometry of the mold 120. When the PVA solution is coated and cured, the liquid PVA precursor will wet and fill the surface of the mold 120 that has been covered by the reinforcing layer 200. After curing, the upper surface of the PVA patterned layer 100 (i.e. the interface in contact with the reinforcing layer 200) can indirectly and with high fidelity replicate the pattern of the mold 120 through the reinforcing layer 200, thereby forming a patterned layer 100 with the required microgrooves 110.

[0034] After the PVA is cured, it is demolded. At this time, the reinforcing layer 200 is sandwiched between the mold 120 and the PVA layer. The reinforcing layer 200 is usually an inorganic material (such as SiO2). Under controllable process conditions, its adhesion to the surface of the mold 120 is designed to be less than its bonding force with the cured PVA layer. This allows the demolding operation to successfully peel the "PVA layer + reinforcing layer 200" as a whole off the mold 120, obtaining a patterned PVA layer 100 with microgrooves 110, while simultaneously completing the pre-positioning of the reinforcing layer 200 on the surface of the PVA layer.

[0035] The step of forming the release layer 300 on the surface of the reinforcing layer 200 is performed on the reinforcing layer 200, which has a stable solid surface. Since the reinforcing layer 200 has completely covered the structured surface of the patterned layer 100, forming the release layer 300 on this substrate (e.g., by spraying a fluorinated silane) ensures that the release layer 300 continuously and uniformly covers all areas, including the inner surface of the microgrooves 110, thereby providing comprehensive and consistent release functionality for subsequent transfer processes.

[0036] The method provided in this application may also include embodiments of conventional support structure construction steps. Specifically, in one embodiment, the fabrication method further includes the step of attaching a self-healing adhesive layer 400 and a support layer 500. This step can typically be performed after the patterned layer 100 (such as a PVA layer) is formed, before demolding, or after demolding. Specifically, the self-healing adhesive layer 400 is attached to the surface of the patterned layer 100 opposite to the reinforcing layer 200, and then the support layer 500 is attached to the self-healing adhesive layer 400. This creates a transfer film variant that includes the support layer 500 and the adhesive layer structure, adapting to different application requirements. Attaching the support layer 500 (e.g., a polyimide film) provides additional mechanical support and overall rigidity to the thinner patterned layer 100, helping to reduce film stretching or twisting caused by external tension during the processing of large-area films or automated transport, and improving alignment accuracy and operational stability during the process. The self-healing adhesive layer 400 is introduced to compensate for the microscopic unevenness of the surfaces of the patterned layer 100 and the support layer 500 through its fluidity or elasticity, promoting initial close contact between the two and subsequent interface stress relaxation. It should be noted that in the manufacturing method of this application, the "step of applying the self-healing adhesive layer 400 and the support layer 500" is an optional process path.

[0037] In further extending the fabrication method, some embodiments also include a step of depositing a reinforcing layer 200 using physical vapor deposition (PVD) after demolding from mold 120. This allows for the selective construction of a composite reinforcing layer system consisting of at least two sublayers. Specifically, after obtaining a composite of the patterned layer 100 and its surface first reinforcing layer, PVD is selectively applied again to deposit a second reinforcing layer on the exposed surface of the first reinforcing layer 200. The material of the second reinforcing layer can be the same as that of the first reinforcing layer (e.g., both being SiO2), potentially resulting in a more uniform or denser overall film through two depositions; alternatively, it can be different from the first reinforcing layer, thus forming a functionally composite or gradient transition structure. Adding the reinforcing layer 200 in a separate step after demolding provides additional process freedom by precisely controlling the total thickness, number of layers, material composition, and interface properties of the reinforcing layer 200 in the final transfer film.

[0038] Please see Figure 4 , Figure 5This application further provides a method for manufacturing photovoltaic cell grid lines. This method is based on the aforementioned multilayer composite transfer film and specifically includes: First, a conductive paste 600 is coated within the microgrooves 110 of the patterned layer 100 of the transfer film, and excess paste on the surface is scraped away and smoothed using a scraper or similar tool. This step utilizes the grooves 110 of the patterned layer 100 to confine the paste, thereby initially defining the pattern, width, and paste volume of the grid lines. Next, the transfer film, with its release layer 300 side facing the surface of the photovoltaic cell 700 (such as a silicon wafer), is placed and aligned. Subsequently, hot-press transfer is performed, i.e., heating is applied while applying a certain pressure to ensure close contact between the transfer film and the cell 700. During this process, heat is transferred through each layer of the transfer film, causing the conductive paste 600 within the groove 110 to heat up and change its fluidity, transferring it from the groove 110 to the surface of the battery cell 700. Simultaneously, the outermost release layer 300, due to its low surface energy, effectively reduces the adhesion between the transfer film and the surface of the battery cell 700 under hot pressing. Meanwhile, the intermediate reinforcing layer 200 provides support for the patterned layer 100 at this temperature, suppressing its thermal softening and deformation, thus creating conditions for the next step. After the hot pressing step is completed, a film peeling operation is performed to detach the entire transfer film from the surface of the battery cell 700. Due to the effect of the release layer 300 and the suppression of deformation of the patterned layer 100 by the reinforcing layer 200, the force required for this peeling process is controlled, facilitating complete demolding and protecting the morphology of the transferred paste pattern. Finally, the conductive paste 600 pattern transferred to the surface of the battery cell 700 is dried and sintered at high temperature to completely remove the organic carrier in the paste and form dense metallized grid lines with excellent conductivity and adhesion.

[0039] As described above, this application provides a multilayer composite transfer film, its fabrication method, and its application in photovoltaic cell grid line preparation. The core structure of the transfer film includes a patterned layer, a reinforcement layer, and a release layer. The patterned layer has microgrooves complementary to the target grid lines, used to accommodate conductive paste. The reinforcement layer continuously covers the patterned layer and its groove surfaces, providing mechanical reinforcement, suppressing thermal deformation of the patterned layer, and stabilizing the interface. The release layer covers the surface of the reinforcement layer, physically isolating it from the patterned layer. This allows the release layer to maintain effective low surface energy characteristics under high-temperature transfer conditions, thereby helping to reduce the tearing force.

[0040] The technical solution of this application covers optional embodiments that include a conventional support structure, namely, a self-healing adhesive layer and a support layer are sequentially disposed on the other side of the patterned layer to provide additional mechanical support. In specific embodiments of the reinforcing layer, it may include two or more sub-reinforcing layers, and may include a transition layer specifically used to improve the interface bonding with the patterned layer.

[0041] The manufacturing method provided in this application includes: applying a PVA solution to a mold with a raised structure and curing it to form a patterned layer; after demolding, forming a release layer and / or a reinforcement layer on the exposed surface of the reinforcement layer. The method may also optionally include the steps of bonding a self-healing adhesive layer to a support layer, and the step of re-depositing a second reinforcement layer after demolding.

[0042] This application further provides a method for fabricating photovoltaic cell grid lines using the aforementioned transfer film, comprising: filling the grooves of the transfer film with conductive paste; aligning the transfer film with the solar cell and performing hot-press transfer; peeling off the transfer film; and finally drying and sintering the paste transferred to the solar cell. Through the optimization of the above structure and method, this application provides a transfer scheme that helps reduce interface defects and improves mechanical and release properties, making it suitable for the dry fabrication of photovoltaic cell grid lines.

[0043] 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 multilayer composite transfer film, characterized in that, This includes a patterning layer, a reinforcement layer, and a release layer; The patterned layer includes grooves corresponding to the grid lines of the battery cells; The reinforcement layer is continuously formed on the surface of the patterned layer and the groove; The release layer covers the surface of the reinforcing layer; The reinforcement layer isolates the release layer from the patterning layer.

2. The multilayer composite transfer film according to claim 1, characterized in that, It also includes a healing adhesive layer and a support layer, wherein the healing adhesive layer is formed on the side of the patterned layer opposite to the reinforcing layer, and the support layer is formed on the side of the healing adhesive layer opposite to the patterned layer.

3. The multilayer composite transfer film according to claim 1, characterized in that, The thickness of the enhancement layer is in the range of 1nm-100nm, and the thickness of the patterned layer is in the range of 20μm-70μm.

4. The multilayer composite transfer film according to claim 1, characterized in that, The reinforcing layer is made of SiO2.

5. The multilayer composite transfer film according to claim 1, characterized in that, The reinforcement layer includes two or more sub-reinforcement layers.

6. The multilayer composite transfer film according to claim 5, characterized in that, The enhancement layer also includes a transition layer.

7. A method for manufacturing a multilayer composite transfer film, characterized in that, include: Provide a mold, which includes protrusions corresponding to the grid lines of the solar cell; A PVA solution is applied to a mold including raised sections, and the PVA solution is cured to form a patterned layer. Demolding: Removing the patterned layer from the mold. After demolding, a reinforcing layer and / or a release layer are formed on the surface of the patterned layer; A multi-layered composite transfer film is formed, comprising a patterning layer, a reinforcement layer, and a release layer.

8. The method for manufacturing a multilayer composite transfer film according to claim 7, characterized in that, It also includes the steps of applying a self-healing adhesive layer and a support layer.

9. The method for manufacturing a multilayer composite transfer film according to claim 7, characterized in that, After demolding, a reinforcing layer can be deposited using PVD or formed on the mold before applying the PVA solution.

10. A method for manufacturing photovoltaic cell grid lines, characterized in that, It uses the multilayer composite transfer film as described in claims 1-6, and includes the following steps: A conductive paste is applied to the patterned layer of a multilayer composite transfer film and then smoothed out. A multi-layer composite transfer film, including conductive paste, is placed on the battery cell. The conductive paste is transferred to the surface of the battery cell by hot pressing transfer. The conductive paste on the surface of the battery cell is dried and sintered.

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