Laser welding method and system for main-grid-free battery photovoltaic module and module

Abstract

The invention discloses a laser welding method and system for a main-grid-free battery photovoltaic module and the module. The laser welding method comprises the steps that a main-grid-free battery photovoltaic assembly is provided, the main-grid-free battery photovoltaic assembly comprises a main-grid-free battery piece and an auxiliary grid welding strip, and the auxiliary grid welding strip is arranged in an auxiliary grid electrode welding area of the main-grid-free battery piece; strip-shaped light spot irradiation is applied to the auxiliary gate welding strip so that the auxiliary gate welding strip can be welded to the auxiliary gate electrode welding area; wherein the length direction of the strip-shaped light spots is consistent with the length direction of the auxiliary grid welding strips, and the width of the strip-shaped light spots covers the width of a single auxiliary grid welding strip and does not cover a plurality of auxiliary grid welding strips. Through the method, defect expansion caused by traditional laser continuous scanning can be avoided, the hidden crack risk of the battery piece is remarkably reduced, the welding efficiency is greatly improved on the premise that the alloying performance of a welding joint is ensured, and reliable technical support is provided for high-quality and large-scale production of a main-grid-free battery photovoltaic module.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic module production, and in particular to a laser welding method, system and assembly for a photovoltaic module without a main grid cell. Background Art

[0002] With the rapid development of photovoltaic module production technology, busbar-less photovoltaic modules achieve current collection through direct connection of densely distributed secondary grid electrodes with welding ribbons, eliminating the traditional busbar structure, effectively reducing material costs and optical shading, and significantly improving the photoelectric performance of the module. However, it also puts higher requirements on the welding process of connecting the welding ribbons to the grid line electrodes.

[0003] In the welding of traditional main grid-free photovoltaic modules, infrared welding technology is widely used. This technology uses thermal radiation to heat the battery cells as a whole. Although it can achieve rapid welding, due to its imprecise temperature control and uniform energy density distribution, under the current trend of large and thin battery cells, it is very easy to cause cold welding and hidden cracks in the battery cells, resulting in a decline in the performance of the battery cells and a safety hazard. In order to overcome the above problems, laser welding technology has gradually become an alternative. For example, the Chinese invention patent CN118198202A discloses a laser welding method in which a laser is irradiated on a welding strip and scanned along the length of the welding strip to achieve the connection between the welding strip and the auxiliary grid through local heating. After completing a single scan, the laser jumps to the next welding strip and continuously scans along the length of the welding strip until all the welding strips are completed. This method effectively solves the cold welding problem of the prior art. However, the applicant found in the research that this method still has a certain risk of hidden cracks. Summary of the Invention

[0004] The present application mainly provides a laser welding method, system and assembly for a busbar-less photovoltaic module, aiming to solve the technical problem of hidden cracks that are easily caused in the production process of existing busbar-less photovoltaic modules.

[0005] To solve the above-mentioned technical problems, the technical solution adopted in this application is to provide a laser welding method for busbarless photovoltaic modules. The method comprises: providing a group of busbarless photovoltaic modules, each comprising busbarless solar cells and secondary grid welding strips, wherein the secondary grid welding strips are disposed in the secondary grid electrode welding areas of the busbarless solar cells; applying a stripe-shaped light spot to the secondary grid welding strips to weld the secondary grid welding strips to the secondary grid electrode welding areas; wherein the length direction of the stripe-shaped light spot is consistent with the length direction of the secondary grid welding strips, and the width of the stripe-shaped light spot covers the width of a single secondary grid welding strip, and does not cover multiple secondary grid welding strips.

[0006] In some embodiments, the width of a single strip-shaped light spot is 1-1.5 times the width of a single secondary grid welding strip.

[0007] In some embodiments, the length of a single strip light spot is not less than the length of a single auxiliary grid welding strip; applying the strip light spot irradiation to the auxiliary grid welding strip includes: applying the strip light spot irradiation to the auxiliary grid welding strip once, and the strip light spot applied once covers the entire auxiliary grid welding strip along the length direction.

[0008] In some embodiments, the length of a single strip light spot is smaller than the length of a single auxiliary grid welding strip; applying the strip light spot irradiation to the auxiliary grid welding strip includes: applying the strip light spot irradiation to the auxiliary grid welding strip multiple times, the strip light spots applied multiple times are continuously distributed along the length direction, and the spliced ​​light spot pattern of the strip light spots applied multiple times covers the entire auxiliary grid welding strip.

[0009] In some embodiments, the main grid-less solar cell is provided with multiple parallel auxiliary grid electrode welding areas, and multiple auxiliary grid welding strips are arranged at the corresponding auxiliary grid electrode welding areas; applying strip light spot irradiation to the auxiliary grid welding strips includes: applying the strip light spot irradiation to each of the auxiliary grid welding strips at least once in turn.

[0010] In some embodiments, a plurality of parallel secondary grid electrode welding areas are provided on the main grid-less solar cell, and a plurality of the secondary grid welding strips are arranged at the corresponding secondary grid electrode welding areas; applying strip light spot irradiation to the secondary grid welding strips includes: applying the strip light spot irradiation at least once to at least part of the plurality of the secondary grid welding strips at the same time.

[0011] In some embodiments, the power density of the stripe light spot is 5-10W / mm 2 The duration of each irradiation of the strip-shaped light spot is 20-100ms.

[0012] In some embodiments, after providing a group of the busbar-free cell photovoltaic modules, the method further includes: covering the busbar-free cell photovoltaic modules with a flexible film so that the busbar-free cell sheets and the secondary grid welding strips are located in a closed space; evacuating the closed space so that the flexible film is pressed tightly against the surfaces of the busbar-free cell sheets and the secondary grid welding strips, so that the strip-shaped light spot can illuminate the secondary grid welding strips through the flexible film.

[0013] In order to solve the above technical problems, another technical solution adopted in the present application is: to provide a laser welding system for a main-grid-less photovoltaic module, the system comprising: a workbench for carrying a group of said main-grid-less photovoltaic modules, said main-grid-less photovoltaic modules comprising main-grid-less cell sheets and secondary grid welding strips, said secondary grid welding strips being arranged in the secondary grid electrode welding area of ​​said main-grid-less cell sheets; a laser welding device for applying a strip light spot to said secondary grid welding strips to weld said secondary grid welding strips to said secondary grid electrode welding area; wherein the length direction of said strip light spot is consistent with the length direction of said secondary grid welding strip, and the width of said strip light spot covers the width of a single said secondary grid welding strip, and does not cover multiple said secondary grid welding strips.

[0014] In order to solve the above technical problems, another technical solution adopted in this application is: to provide a busbar-less cell photovoltaic module, which includes: a busbar-less cell sheet with multiple secondary grid electrode welding areas on the surface; a secondary grid welding strip, welded to the secondary grid electrode welding areas of the busbar-less cell sheet, and the welding is achieved based on the steps of the laser welding method of the busbar-less cell photovoltaic module as mentioned above.

[0015] The beneficial effects of the present application are as follows: Different from the prior art, the present application discloses a laser welding method, system and assembly for a busbar-less photovoltaic module. The present application applies a strip-shaped light spot irradiation to the auxiliary grid welding strip provided in the auxiliary grid electrode welding area of ​​the busbar-less cell in the provided busbar-less photovoltaic module to replace the traditional laser continuous scanning scheme, so that the welding strip is welded in a single or divided static irradiation, which can avoid the expansion effect of micro-cracks in the cell during the laser moving scanning process, and ensure that the tinned strip forms a dense alloy layer with the auxiliary grid electrode, effectively avoiding cold welding, while significantly reducing the risk of hidden cracks in the cell and greatly improving the welding efficiency. At the same time, this method can also flexibly adapt to the production needs of busbar-less modules of different sizes and specifications, providing reliable technical support for the high-quality and large-scale production of busbar-less photovoltaic modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0017] Figure 1 This is a flow chart of an embodiment of a laser welding method for a busbar-less photovoltaic module provided by the present application;

[0018] Figure 2 yes Figure 1A schematic diagram of an embodiment of welding a busbar-less photovoltaic module in an embodiment;

[0019] Figure 3 yes Figure 1 A schematic diagram of another embodiment of welding a busbar-less photovoltaic module in the embodiment;

[0020] Figure 4 yes Figure 1 A schematic diagram of another embodiment of welding a busbar-less photovoltaic module in the embodiment;

[0021] Figure 5 It is a structural schematic diagram of an embodiment of a laser welding method for a busbar-less photovoltaic module provided in this application. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In addition, the terms "including" and "having" and any variations thereof are intended to be non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units that are inherent to these processes, methods, products or devices. "Covering" refers to the steps implemented for the purpose of including all or the desired effects. In practice, especially for the coverage of the auxiliary grid welding strip in the welding of the battery cell, the coverage specifications can be slightly larger or slightly smaller than the corresponding specifications of a single auxiliary grid welding strip, such as length and width, etc., as long as it can be ensured that the effects caused by the coverage are not destroyed.

[0024] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] In the laser welding technology of photovoltaic modules without main grid cells, for example, Chinese invention patent CN118198202A discloses a laser welding method in which a laser is irradiated on a welding ribbon and scanned along the length of the welding ribbon, thereby achieving connection between the welding ribbon and the auxiliary grid through local heating. After completing a single scan, the laser jumps to the next welding ribbon and continuously scans along the length of the welding ribbon until all welding ribbons are completed. This method effectively solves the problem of cold welding in the prior art. However, the applicant found in the research that this method still has a certain risk of hidden cracks. Through extensive research, the applicant found that this is due to defects in the battery cell itself. When the laser is used to continuously scan the welding ribbon, when it passes through the defects in the battery cell itself, the defects will be guided to expand along the laser scanning direction, resulting in the problem of hidden cracks after welding.

[0026] This application provides a laser welding method for a photovoltaic module without a main grid cell. Figure 1 , Figure 1 1 is a flow chart of an embodiment of a laser welding method for a busbar-less photovoltaic module provided by the present application. The laser welding method for a busbar-less photovoltaic module comprises:

[0027] Step 10: providing a group of busbar-less photovoltaic modules, wherein the busbar-less photovoltaic modules include busbar-less solar cells and secondary grid welding strips, wherein the secondary grid welding strips are arranged on the secondary grid electrode welding areas of the busbar-less solar cells.

[0028] Step 20: Apply a strip light spot to the auxiliary grid welding strip to weld the auxiliary grid welding strip to the auxiliary grid electrode welding area; wherein the length direction of the strip light spot is consistent with the length direction of the auxiliary grid welding strip, and the width of the strip light spot covers the width of a single auxiliary grid welding strip and does not cover multiple auxiliary grid welding strips.

[0029] In this embodiment, the main-grid-free photovoltaic module can be provided by upstream equipment transmission of the production line, manual handling or automated transportation device transfer during the photovoltaic module production process, so as to facilitate the subsequent welding of the main-grid-free photovoltaic module. The main-grid-free photovoltaic module specifically includes main-grid-free cell sheets and auxiliary grid welding strips. It can be understood by those skilled in the art that the main-grid-free photovoltaic module can be a string of cells to be welded, or a whole panel of photovoltaic modules to be welded. When it is a whole panel of photovoltaic modules to be welded, the main-grid-free photovoltaic module also includes a photovoltaic substrate. Generally speaking, this substrate includes photovoltaic glass and a heat-sealing layer arranged above the photovoltaic glass, such as POE (Polyolefin Elastomer) or EVA (Ethylene Vinyl Acetate). The main-grid-free cell sheets and auxiliary grid welding strips are arranged on the heat-sealing layer in sequence according to the photovoltaic module layout.

[0030] In this embodiment, multiple fine grids, i.e., secondary grid electrodes, are provided on the busbar-less cell of a busbar-less photovoltaic module. Each secondary grid electrode is used to collect current generated by the photovoltaic effect. The secondary grid electrode welding area on the busbar-less cell refers to the metal area on the busbar-less cell that is connected to the secondary grid electrode. By placing the secondary grid welding ribbon on the secondary grid electrode welding area, the secondary grid welding ribbon can be precisely welded to the secondary grid electrode welding area through a subsequent welding process, thereby establishing an electrical connection between the secondary grid electrodes on the busbar-less cell, thereby enabling power transmission in the photovoltaic module. Those skilled in the art will appreciate that the secondary grid welding ribbon is generally perpendicular to the secondary grid electrodes on the busbar-less cell, connecting multiple secondary grid electrodes on the busbar-less cell.

[0031] In this embodiment, the present application specifically irradiates the auxiliary grid welding strip at least once through a strip light spot to achieve welding. The strip light spot refers to a high energy density light spot shaped like an elongated rectangle or a line. Through optical shaping technology, based on the preset parameter characteristics of the strip light spot such as length, width, energy density, etc., the original laser beam is shaped using optical shaping mechanisms such as diffraction optical devices and optical masks, so that a strip light spot with corresponding parameters can be irradiated. The strip light spot is projected onto the auxiliary grid welding strip, locally heating the welding strip for a holding time to achieve metal fusion between the welding strip and the auxiliary grid electrode welding area. Compared with the continuous laser scanning method in traditional laser welding technology, the irradiation method of the strip light spot is a static irradiation method. The auxiliary grid welding strip is welded in the static irradiation of the strip light spot in a single or multiple splicing, so that the strip light spot covers the entire auxiliary grid welding strip in a single or multiple splicing, so as to avoid the traction and expansion effect of micro cracks in the battery cell during the laser moving scanning process, thereby reducing the risk of hidden cracks in the battery cell.

[0032] In this embodiment, under the conditions of a certain energy density and holding time, the metal between the auxiliary grid welding strip and the auxiliary grid electrode welding area can reach the melting point, thereby forming a strong metal alloy layer after cooling, forming a welding relationship. It should be understood that under the conditions of different energy densities and holding times, the irradiation of the same area of ​​the auxiliary grid welding strip can be one or more times, and as long as the irradiation can form a welding relationship, it can be understood that it is within the scope of protection of this application. However, in order to avoid problems such as over-welding or poor welding, the energy density and holding time of the strip light spot need to be controlled within a certain range. For example, a welding relationship can be formed by a single irradiation with a corresponding energy density and holding time, and there is no need to use more irradiations or maintain a longer holding time. If the energy density and holding time are insufficient or exceeded, the corresponding energy density, holding time or number of irradiations can be appropriately increased or decreased so that the strip light spot irradiation can ensure a good welding relationship between the auxiliary grid welding strip and the auxiliary grid electrode welding area. This application will be described later as completing welding with one irradiation, that is, "the area of ​​the auxiliary grid welding strip irradiated by a single strip light spot can form a welding relationship with the auxiliary grid electrode welding area."

[0033] In this embodiment, to ensure that the applied strip light spot can accurately cover the entire secondary grid welding ribbon and ensure that the welding ribbon is evenly heated during the welding process, thereby avoiding problems such as over-welding, missed welding, and cold welding, it is necessary to accurately set parameters such as its length, width, energy density, and hold time to meet the welding requirements. It should be noted that the setting of these parameters needs to be flexibly adjusted according to the specifications, materials, type of secondary grid welding ribbon, and arrangement spacing of the actual busbar-less solar cell photovoltaic module. For example, the width of the strip light spot cannot be too long to avoid damaging the insulating adhesive provided between the secondary grid electrodes and causing a short circuit; the width cannot be too short to avoid the secondary grid welding ribbon being firmly welded to the secondary grid electrode welding area and causing a cold welding; the energy density and hold time cannot be too high to avoid spattering and over-welding during the welding process, causing thermal damage to the solar cell; and the energy density and hold time cannot be too low to avoid insufficient welding strength and cold welding. Therefore, it is necessary to reasonably set the parameters of the strip light spot to further optimize welding efficiency while ensuring welding quality, making the welding process more stable and reliable.

[0034] In this embodiment, the length of the stripe light spot is generally required to be equivalent to that of a single secondary grid welding ribbon. For example, if the length of a single secondary grid welding ribbon is 182 mm, then the length of the corresponding stripe light spot is specifically set to the same 182 mm. Alternatively, it can be set to a similar length of 181 mm or 183 mm. When the stripe light spot is slightly less than or slightly greater than the length of a single secondary grid welding ribbon, the stripe light spot can still effectively cover the main portion of the secondary grid welding ribbon and achieve welding. When the length of the stripe light spot is selected to be equivalent to that of a single secondary grid welding ribbon, only a single irradiation of the single secondary grid welding ribbon is required. Therefore, to ensure welding efficiency, the length of a single stripe light spot is generally set to be no less than that of a single secondary grid welding ribbon. Under this condition, only a single stripe light spot needs to be applied to the single secondary grid welding ribbon, and the single stripe light spot can cover the entire secondary grid welding ribbon along its length, completing the welding of the single secondary grid welding ribbon. After the stripe light spot is applied to all secondary grid welding ribbons, the welding of the photovoltaic module without busbar cells is completed.

[0035] In this embodiment, there may be some situations where the length of a single strip light spot cannot cover the entire single auxiliary grid welding strip due to limitations of the optical module or welding process, or there may be actual business needs to weld a single auxiliary grid welding strip multiple times. In these cases, that is, when the length of a single strip light spot is less than the length of a single auxiliary grid welding strip, the entire single auxiliary grid welding strip can be welded by applying strip light spots to the auxiliary grid welding strip multiple times, so that the spliced ​​light spot pattern of the multiple applied strip light spots covers the entire auxiliary grid welding strip. In this case, the multiple applied strip light spots need to be continuously distributed along the length direction of the auxiliary grid welding strip to ensure that the spliced ​​light spot pattern of the strip light spots can cover the entire single auxiliary grid welding strip, thereby achieving complete welding. For example, for an 182mm-long secondary grid ribbon, its secondary grid electrode welding area can be considered as two equally divided adjacent areas of 91mm, that is, areas that are half the length of the secondary grid ribbon. Therefore, when welding, a strip light spot can be applied to each of the two adjacent 91mm areas. The length of the strip light spot can be set to 90mm, 91mm, or 92mm, etc., to cover the two adjacent areas in two steps, thereby achieving a complete weld. It should be noted that when the strip light spot moves from one area to the adjacent area, it is in a light-off state to avoid the occurrence of cracks caused by the scanning effect caused by the movement of the strip light spot.

[0036] In this embodiment, for a single secondary grid welding strip, it can also be regarded as more adjacent areas that are evenly divided, and then strip light spots are applied to each adjacent area separately, or it can be regarded as multiple irregular adjacent areas that are irregularly divided. The length of the irradiated strip light spots can be adjusted during each irradiation to meet the requirements of adjacent distribution and coverage. During this irradiation process, the positions of the strip light spots are preferably tangent during two adjacent irradiations. However, in actual operation, in order to avoid poor welding quality in a certain length area at the intersection of adjacent areas, the strip light spots can be overlapped to a certain extent in the length direction of the secondary grid welding strip during two adjacent irradiations, such as 1%-5%, to ensure the welding quality in the intersection area. The overlapping length can be flexibly adjusted according to parameters such as the material and thickness of the secondary grid welding strip and the energy density of the strip light spots to achieve the best welding effect. In addition, during the welding process, optical modulation can be used to make the energy density distribution of the strip light spots more uniform, thereby avoiding local high temperatures generated during welding and further reducing the risk of hidden cracks in the battery cell.

[0037] In this embodiment, the setting of the width of the strip light spot also needs to take into account the width of the auxiliary grid welding strip and the energy distribution required for welding. The width of the strip light spot needs to be set to ensure that it can fully cover the width of a single auxiliary grid welding strip and will not cover multiple auxiliary grid welding strips, so as to avoid an excessively wide irradiation range that may adversely affect adjacent auxiliary grid electrodes or insulating materials. Specifically, the width of a single strip light spot can be set to 1-1.5 times the width of a single auxiliary grid welding strip. For example, if the width of a single auxiliary grid welding strip is 2 mm, the width of the strip light spot can be set to slightly larger than 2 mm, such as 2.1 mm or 2.2 mm, to ensure uniform heating and welding in the width direction of the welding strip and achieve a good welding effect. This avoids the problem of cold welding that may be caused by the width of the strip light spot being too narrow, and the hidden danger of short circuit that may be caused by its width being too wide. By reasonably setting the width of the strip light spot, not only can the welding quality be guaranteed, but also the energy distribution during the welding process can be effectively controlled, further reducing the risk of thermal damage to the battery cell.

[0038] In this embodiment, as a form of static welding, the energy density and holding time of the strip light spot are the key to ensuring welding strength, avoiding cold joints and avoiding hidden cracks. The above-mentioned welding effect can only be achieved by maintaining a certain energy density range and a certain time. Unlike the continuous scanning of the prior art, the technical solution of the present application is consistent in the irradiation time of the entire secondary grid welding strip, that is, the power density and holding time of the laser irradiation are equal at the welding point position and the non-welding point position. Therefore, if the power density is too high, it will not only lead to problems such as over-welding of the welding point, solder splashing and thermal damage to the battery cell, but the welding strip at the non-welding point will also be irradiated with excessive power density, which will cause damage to the insulating glue and cause short circuit problems. It will also shrink after cooling, causing residual stress to be concentrated at the welding point position, causing the battery cell to bend, and also cause hidden cracks. After a large number of experiments, the applicant found that the energy density of the strip light spot is 5-10W / mm 2 When the holding time is 20-100ms, good welding tension can be achieved, without voids and avoiding hidden cracks.

[0039] In this embodiment, the secondary grid electrode welding area on the main grid-less cell photovoltaic module is usually not set independently. There will be multiple parallel secondary grid electrode welding areas on the main grid-less cell sheet, and multiple secondary grid welding strips are set in the corresponding secondary grid electrode welding areas. Therefore, it is usually necessary to consider the welding of multiple secondary grid welding strips during the welding process.

[0040] In this embodiment, when welding this type of busbar-less photovoltaic module, one method of applying a stripe-shaped light spot to the secondary grid welding ribbons includes sequentially applying at least one stripe-shaped light spot to each secondary grid welding ribbon. Specifically, the stripe-shaped light spot can be applied to the first secondary grid welding ribbon first, and after the welding is completed, the stripe-shaped light spot can be applied to the next adjacent secondary grid welding ribbon, and so on, until all the secondary grid welding ribbons are welded.

[0041] This embodiment can be found in Figure 2 , Figure 2 yes Figure 1 Schematic diagram of an embodiment of welding a busbar-less photovoltaic module. Reference numeral 31 represents a busbar-less cell, reference numeral 32 represents a secondary grid welding strip covering the secondary grid electrode welding area of ​​the busbar-less cell, and reference numeral 33 represents the area illuminated by the stripe light spot. In this diagram, the stripe light spot 33 covers the entire secondary grid welding strip 32 in a single pass, enabling precise welding of the secondary grid welding strip 32.

[0042] This embodiment can also refer to Figure 3 , Figure 3 yes Figure 1 Schematic diagram of another embodiment of welding a photovoltaic module without a main grid cell in the embodiment, and its reference numerals are the same as those in the embodiment. Figure 2 The same, no further description is needed here, the difference is that the irradiation method is a static irradiation splicing method. Figure 3 Taking the example of irradiating the same auxiliary grid welding strip twice, the strip light spot 33 is applied twice along the length direction of the auxiliary grid welding strip. First, half of the auxiliary grid welding strip 32 is irradiated by the strip light spot 33a, and then the other half of the same auxiliary grid welding strip 32 is irradiated by the strip light spot 33b, thereby covering the entire auxiliary grid welding strip 32, and similarly achieving precise welding of the auxiliary grid welding strip 32.

[0043] This welding method in this embodiment can avoid the effect of laser scanning on the expansion of micro cracks in the cell, ensuring that the tin in the solder strip forms a dense alloy layer with the auxiliary grid electrode, effectively avoiding cold solder joints, while significantly reducing the risk of hidden cracks in the cell and greatly improving the welding efficiency. At the same time, this method is simple to operate and easy to control the welding sequence and quality. However, due to Figure 2 and Figure 3 The welding method illustrated in the example is to apply at least one laser irradiation to a single auxiliary grid welding strip one by one to achieve welding, which requires a long total time during the welding process, especially when there are a large number of auxiliary grid welding strips. Therefore, in order to improve welding efficiency and save welding time, this embodiment can also adopt a spectroscopic welding method to irradiate multiple strip-shaped light spots at a time, thereby irradiating multiple auxiliary grid welding strips at the same time.

[0044] In this embodiment, when welding this type of busbar-less photovoltaic module, another method of applying strip-shaped light spots to the secondary grid ribbons includes: simultaneously applying at least one strip-shaped light spot to at least a portion of the multiple secondary grid ribbons. Specifically, during each strip-shaped light spot irradiation, multiple strip-shaped light spots are irradiated onto a corresponding number of the secondary grid ribbons to achieve synchronous welding of the multiple secondary grid ribbons. After welding the corresponding number of secondary grid ribbons, the process can be moved to the next group of secondary grid ribbons to be welded, and the above steps can be repeated until all the secondary grid ribbons are welded. The multiple strip-shaped light spots can also be obtained by optically shaping the original laser beam and irradiating them simultaneously. Compared with the method of welding one by one, this method can significantly improve welding efficiency and is particularly suitable for situations where there are a large number of secondary grid ribbons in busbar-less photovoltaic modules.

[0045] This embodiment can be found in Figure 4 , Figure 4 yes Figure 1 A schematic diagram of another embodiment of welding a main grid-free photovoltaic module in the embodiment, the reference numerals thereof are the same as those in the embodiment. Figure 2 and Figure 3 The same, no need to repeat here, the difference is that the irradiation method is a spectroscopic welding method, Figure 4 Taking the simultaneous illumination of two auxiliary grid welding strips as an example, in this schematic diagram, the strip-shaped light spots 33c and 33d simultaneously cover the two auxiliary grid welding strips 32, achieving synchronous welding of the two auxiliary grid welding strips 32, thereby effectively improving welding efficiency and shortening the overall welding time, which is particularly suitable for large-scale busbar-free photovoltaic module production line operations. It should be understood that Figure 4 The method is single-shot spectral welding, which can also be combined with Figure 3 The stepwise welding method shown realizes split-way welding. For example, after simultaneously welding the first part of each auxiliary grid welding strip in a group of auxiliary grid welding strips, the other unwelded parts of each auxiliary grid welding strip in the group are split-way welding at the same time, until all the auxiliary grid welding strips in a group are welded, and then the welding of the next group is carried out.

[0046] In this embodiment, the above steps need to be completed after a group of auxiliary grid welding strips and the corresponding optical module is turned off for irradiating the strip light spot, and then the position and irradiation angle of the corresponding optical module are moved, and after aligning with the next group of auxiliary grid welding strips, the irradiation of the strip light spot is turned on again to weld the corresponding auxiliary grid welding strips and the auxiliary grid electrode welding area, so as to avoid the occurrence of hidden cracks caused by the irradiation effect similar to scanning during the movement, effectively avoid unnecessary damage to the welding area or affect the welding accuracy, and ensure the accuracy and efficiency of welding.

[0047] In this embodiment, the movement control of the corresponding optical module can specifically be performed by first obtaining the position coordinates and angular deviation data of the auxiliary grid welding ribbon to be welded, then moving the position of the strip light spot according to the position coordinates, and finally adjusting the angle of the strip light spot according to the angular deviation data, thereby ensuring that the strip light spot can be accurately aligned with the auxiliary grid welding ribbon to be welded for welding. Specifically, the position coordinates and angular deviation data of the unfinished auxiliary grid welding ribbon can be obtained by a coaxial positioning camera. The coaxial positioning camera can obtain the horizontal coordinate, vertical coordinate and angular deviation data of a specific positioning point in the corresponding area by photographing the area corresponding to the auxiliary grid welding ribbon to be welded. The horizontal coordinate and vertical coordinate can then be sent to the drive motor to move the corresponding optical module to the position corresponding to the horizontal coordinate and vertical coordinate. Finally, the angular deviation data is sent to the deflection motor to adjust the deflection angle of the reflector inside the light source, thereby effectively adjusting the irradiation angle of the strip light spot so that the strip light spot can be accurately aligned with the auxiliary grid welding ribbon to be welded.

[0048] In this embodiment, in some preferred implementations, after providing a group of busbar-free cell photovoltaic modules, the method further includes: covering the busbar-free cell photovoltaic modules with a flexible film so that the busbar-free cell sheets and the secondary grid welding strips are located in a closed space; and evacuating the closed space so that the flexible film is pressed tightly against the surfaces of the busbar-free cell sheets and the secondary grid welding strips so that the strip-shaped light spot can pass through the flexible film to illuminate the secondary grid welding strips.

[0049] In this embodiment, the flexible film is a transparent, flexible film material. Materials such as polyester film, polyimide film, and polyethylene film can be used. These materials offer excellent light transmittance and heat resistance, maintaining stable performance during laser welding and preventing deformation or cracking due to high temperatures. The flexible film forms a closed space within the busbarless photovoltaic module. After evacuating the closed space, the flexible film adheres tightly to the surfaces of the busbarless solar cells and the secondary grid ribbon, ensuring that the strip-shaped light spot can penetrate the flexible film and accurately illuminate the secondary grid ribbon. This approach effectively mitigates the effects of air flow and dust on welding quality, improving welding accuracy and stability. Furthermore, the compressive force of the flexible film ensures a closer fit between the secondary grid ribbon and the busbarless solar cells, facilitating heat transfer and enhancing fusion during welding. After welding is complete, the flexible film can be easily removed without affecting the performance and usability of the busbarless photovoltaic module. By covering the flexible film with a vacuum seal, the ribbon and solar cells adhere closely to each other, preventing cold welds and improving welding quality.

[0050] Experimental data shows that the laser welding method implemented using this embodiment reduces the hidden crack rate by 10-30% compared to infrared welding and by 10-20% compared to traditional laser scanning welding. Furthermore, this method can flexibly adapt to the production needs of busbarless modules of varying sizes, providing reliable technical support for the high-quality, large-scale production of busbarless photovoltaic modules.

[0051] See Figure 5 , Figure 5 The present invention is a schematic structural diagram of an embodiment of a laser welding system for busbarless photovoltaic modules provided herein. The laser welding system 40 comprises: a workbench 41 for supporting a group of busbarless photovoltaic modules, each comprising a busbarless cell and a secondary grid welding ribbon, the secondary grid welding ribbon being disposed in the secondary grid electrode welding region of the busbarless cell; and a laser welding device 42 for applying a stripe-shaped light spot to the secondary grid welding ribbon to weld the secondary grid welding ribbon to the secondary grid electrode welding region. The length of the stripe-shaped light spot is aligned with the length of the secondary grid welding ribbon, and the width of the stripe-shaped light spot covers the width of a single secondary grid welding ribbon, but does not cover multiple secondary grid welding ribbons.

[0052] Optionally, in some embodiments, the width of a single strip-shaped light spot is 1-1.5 times the width of a single auxiliary grid welding strip.

[0053] Optionally, in some embodiments, the length of a single strip light spot is not less than the length of a single auxiliary grid welding strip; the laser welding device 42 is also used to: apply a strip light spot to the auxiliary grid welding strip, and the strip light spot applied once covers the entire auxiliary grid welding strip along the length direction.

[0054] Optionally, in some embodiments, the length of a single strip light spot is less than the length of a single auxiliary grid welding strip; the laser welding device 42 is also used to: apply strip light spots to the auxiliary grid welding strip in multiple times, the multiple applied strip light spots are continuously distributed along the length direction of the auxiliary grid welding strip, and the spliced ​​light spot pattern of the multiple applied strip light spots covers the entire auxiliary grid welding strip.

[0055] Optionally, in some embodiments, a plurality of parallel secondary grid electrode welding areas are provided on the main grid-less solar cell, and a plurality of secondary grid welding strips are arranged in the corresponding secondary grid electrode welding areas; the laser welding device 42 is also used to: apply at least one strip spot irradiation to each secondary grid welding strip in turn.

[0056] Optionally, in some embodiments, a plurality of parallel secondary grid electrode welding areas are provided on the main grid-less solar cell, and a plurality of secondary grid welding strips are arranged in the corresponding secondary grid electrode welding areas; the laser welding device 42 is also used to: simultaneously apply at least one strip light spot irradiation to at least part of the plurality of secondary grid welding strips.

[0057] Optionally, in some embodiments, the power density of the stripe light spot is 5-10 W / mm 2 .

[0058] Optionally, in some embodiments, the duration of each irradiation of the strip-shaped light spot is 20-100 ms.

[0059] Optionally, in some embodiments, the laser welding device 42 includes an optical shaping module, which is used to shape the original laser beam into a strip-shaped light spot.

[0060] Optionally, in some embodiments, the laser welding device 42 also includes a motion control module and an optical module, wherein the motion control module specifically includes a coaxial positioning camera, a drive motor and a deflection motor, wherein the coaxial positioning camera is used to obtain the position coordinates and angle deviation data of the secondary grid welding strip to be welded; the drive motor is used to move the position of the strip light spot irradiation in a direction parallel to the main grid-free solar cell according to the position coordinates; and the deflection motor is used to adjust the angle of the strip light spot irradiation according to the angle deviation data.

[0061] Optionally, in some embodiments, the laser welding device 42 is also used to cover a flexible film on the main-grid-free photovoltaic module, so that the main-grid-free cell pieces and the secondary grid welding strips are located in a closed space; the closed space is evacuated to press the flexible film tightly against the surface of the main-grid-free cell pieces and the secondary grid welding strips, so that the strip light spot can pass through the flexible film to irradiate the secondary grid welding strips.

[0062] Since the embodiments of the system part correspond to the embodiments of the above-mentioned method, please refer to the above-mentioned method embodiments for the introduction of the laser welding system 40 provided in the embodiments of the present invention. The embodiments of the present invention will not be repeated here, and it has the same beneficial effects as the above-mentioned laser welding method.

[0063] The present application also provides a busbar-free photovoltaic module, which includes: a busbar-free cell sheet with a plurality of secondary grid electrode welding areas on its surface; a secondary grid welding strip welded to the secondary grid electrode welding areas of the busbar-free cell sheet, the welding being based on the following Figures 1 to 4 The steps of the laser welding method for busbar-less photovoltaic modules are described.

[0064] The structure of each component in the busbar-free photovoltaic module can be found in Figures 2 to 4 , which will not be described in detail in this application. The feature that distinguishes this photovoltaic module from existing busbar-free photovoltaic modules is that this photovoltaic module adopts the above-mentioned Figures 1 to 4The laser welding method described above achieves welding between the secondary grid ribbon and the secondary grid electrode welding area. The busbar-less photovoltaic module can specifically be a heterojunction cell, a tunneling oxide passivation contact cell, a cross-back contact cell, or other busbar-less cell types. This application does not impose specific restrictions on this type of cell, as long as the aforementioned laser welding method can be used to weld the secondary grid ribbon to the secondary grid electrode welding area.

[0065] Since the embodiments of the component part correspond to the embodiments of the above-mentioned method, please refer to the above-mentioned method embodiments for the introduction of the main-grid-free cell photovoltaic component provided by the embodiment of the present invention. The embodiment of the present invention will not be repeated here, and it has the same beneficial effects as the above-mentioned laser welding method.

[0066] Different from the existing technology, the present application discloses a laser welding method, system and assembly for busbar-free photovoltaic modules. By applying strip-shaped light spot irradiation to the auxiliary grid welding strip set in the auxiliary grid electrode welding area of ​​the busbar-free cell in the provided busbar-free photovoltaic module, the traditional laser continuous scanning scheme is replaced, so that the welding strip is welded in a single or divided static irradiation, which can avoid the expansion effect of micro-cracks in the cell during the laser moving scanning process. While ensuring that the tinned strip forms a dense alloy layer with the auxiliary grid electrode, effectively avoiding cold welding, it significantly reduces the risk of hidden cracks in the cell and greatly improves the welding efficiency. At the same time, this method can also flexibly adapt to the production needs of busbar-free modules of different sizes and specifications, providing reliable technical support for the high-quality and large-scale production of busbar-free photovoltaic modules.

[0067] The various embodiments in this specification are described in a progressive manner. Similar portions between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from the other embodiments. In particular, the embodiments of the laser welding system for busbarless photovoltaic modules and the embodiments of busbarless photovoltaic modules are generally similar to the embodiments of the laser welding method for busbarless photovoltaic modules, so the descriptions are relatively simplified. For relevant details, refer to the description of the embodiments of the laser welding method for busbarless photovoltaic modules.

[0068] In the several embodiments provided herein, it should be understood that the disclosed methods, systems, and components may be implemented in other ways. For example, the above-described embodiment of a laser welding system for busbar-less photovoltaic modules is merely illustrative. For example, the division of modules or units in the system is merely a logical functional division, and actual implementation may employ other division methods, such as combining or integrating multiple units or components into another system, or omitting or disabling certain features.

[0069] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of this embodiment.

[0070] In addition, in the several embodiments provided in this application, it is also understood that the above-mentioned laser welding method, system, and assembly are mainly described in the production process of busbar-free photovoltaic modules. In actual application, the laser welding method only needs to replace the target object with a busbar-based photovoltaic module and transplant the welding method of the secondary grid electrode and the corresponding welding ribbon to the grid line and corresponding welding ribbon of the busbar-based photovoltaic module, and can also achieve effective welding of the corresponding photovoltaic module. However, due to the mechanical support of the busbar in the busbar-based photovoltaic module, the risk of hidden cracks is smaller than that of the busbar-free photovoltaic module of this application. Moreover, due to the presence of the busbar structure, the number of busbar weld points is smaller and generally more concise. Traditional spot welding can effectively reduce the risk of hidden cracks. Therefore, the efficiency gain brought by the laser welding method of the same solution is limited. Therefore, this embodiment does not limit the application of the laser welding method to other types of photovoltaic modules. Similar methods in the field that use single or multiple static irradiation of the light spot instead of scanning to weld the corresponding welding ribbon and grid line are all within the scope of protection of this embodiment.

[0071] In addition, although this embodiment is mainly illustrated using a strip-shaped light spot as an example, it does not mean that the laser welding method of this embodiment is limited to the use of a strip-shaped light spot. Light spots of other shapes, such as circular, elliptical or square, etc., as long as the corresponding light spot is used to irradiate the auxiliary grid welding strip of matching shape at least once to achieve welding, it can meet the welding requirements and avoid continuous scanning of the laser, and can also be regarded as within the scope of protection of this application.

[0072] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A laser welding method for a busbar-less photovoltaic module, characterized in that: include: A group of the busbar-free photovoltaic modules is provided, wherein the busbar-free photovoltaic modules include busbar-free solar cells and secondary grid welding strips, wherein the secondary grid welding strips are arranged in the secondary grid electrode welding area of ​​the busbar-free solar cells; A strip light spot is applied to the auxiliary grid welding strip to weld the auxiliary grid welding strip to the auxiliary grid electrode welding area; wherein the length direction of the strip light spot is consistent with the length direction of the auxiliary grid welding strip, and the width of the strip light spot covers the width of a single auxiliary grid welding strip and does not cover multiple auxiliary grid welding strips.

2. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The width of a single strip-shaped light spot is 1-1.5 times the width of a single auxiliary grid welding strip.

3. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The length of a single strip-shaped light spot is not less than the length of a single auxiliary grid welding strip; The applying a strip-shaped light spot to the auxiliary grid welding strip comprises: The strip-shaped light spot is applied once to the auxiliary grid welding strip, and the strip-shaped light spot applied once covers the entire auxiliary grid welding strip along the length direction.

4. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The length of a single strip-shaped light spot is smaller than the length of a single auxiliary grid welding strip; The applying a strip-shaped light spot to the auxiliary grid welding strip comprises: The strip light spots are applied to the auxiliary grid welding strip for multiple times, the strip light spots applied multiple times are continuously distributed along the length direction, and the spliced ​​light spot pattern of the strip light spots applied multiple times covers the entire auxiliary grid welding strip.

5. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The busbar-less solar cell is provided with a plurality of parallel auxiliary grid electrode welding areas, and a plurality of the auxiliary grid welding strips are provided at the corresponding auxiliary grid electrode welding areas; The applying a strip-shaped light spot to the auxiliary grid welding strip comprises: The strip-shaped light spot is applied to each of the auxiliary grid welding strips at least once in sequence.

6. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The busbar-less solar cell is provided with a plurality of parallel auxiliary grid electrode welding areas, and a plurality of the auxiliary grid welding strips are provided at the corresponding auxiliary grid electrode welding areas; The applying a strip-shaped light spot to the auxiliary grid welding strip comprises: The strip-shaped light spot irradiation is applied at least once to at least part of the plurality of auxiliary grid welding strips simultaneously.

7. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: The power density of the stripe light spot is 5-10W / mm 2 The duration of each irradiation of the strip-shaped light spot is 20-100ms.

8. The laser welding method for busbar-less photovoltaic modules according to claim 1, characterized in that: After providing a group of busbar-free photovoltaic modules, the method further includes: Covering the busbar-less photovoltaic module with a flexible film so that the busbar-less solar cell and the secondary grid welding strip are located in a closed space; The enclosed space is evacuated to press the flexible film tightly against the busbar-free solar cell and the surface of the auxiliary grid welding strip, so that the strip-shaped light spot can pass through the flexible film to irradiate the auxiliary grid welding strip.

9. A laser welding system for busbar-less photovoltaic modules, characterized in that: include: A workbench, used to carry a group of the busbar-less cell photovoltaic assemblies, wherein the busbar-less cell photovoltaic assemblies include busbar-less cell sheets and secondary grid welding strips, wherein the secondary grid welding strips are arranged in the secondary grid electrode welding areas of the busbar-less cell sheets; A laser welding device is used to apply a strip-shaped light spot to the auxiliary grid welding strip to weld the auxiliary grid welding strip to the auxiliary grid electrode welding area; wherein the length direction of the strip-shaped light spot is consistent with the length direction of the auxiliary grid welding strip, and the width of the strip-shaped light spot covers the width of a single auxiliary grid welding strip and does not cover multiple auxiliary grid welding strips.

10. A busbar-less photovoltaic module, characterized in that: include: There is no main grid cell, and multiple auxiliary grid electrode welding areas are provided on the surface; The auxiliary grid welding strip is welded to the auxiliary grid electrode welding area of ​​the busbar-free cell sheet, and the welding is achieved based on the steps of the laser welding method of the busbar-free cell photovoltaic module according to any one of claims 1 to 8.

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