Mask plate for laser film opening of battery piece

Abstract

The utility model provides a mask plate for laser film opening of a battery piece and a preparation method of the mask plate, the mask plate comprises a rectangular substrate, N light-transmitting units are arranged on the substrate at intervals in the first direction, and the distance between every two adjacent light-transmitting units is larger than or equal to the width of a main grid line of the battery piece to be produced; each light-transmitting unit comprises M rectangular light-transmitting grooves which are arranged at intervals in the second direction, each light-transmitting groove corresponds to an area between adjacent auxiliary grid lines of a to-be-produced battery piece, the long edge of each light-transmitting groove is smaller than or equal to the length of the auxiliary grid lines of the to-be-produced battery piece, the long edge of each light-transmitting groove is parallel to the first direction, and M is an integer greater than or equal to 2. The short edge of the light-transmitting groove is smaller than or equal to the distance between adjacent auxiliary grid lines of the battery piece to be produced, and the short edge of the light-transmitting groove is parallel to the second direction. Wherein N > = 2, M > = 2, the first direction is parallel to one side edge of the substrate, and the second direction is perpendicular to the first direction. By adopting the mask plate provided by the utility model to perform laser film opening on the to-be-processed battery piece, factors such as galvanometer refresh frequency, response speed of a laser, pulse frequency of the laser and the like do not need to be considered, the edge of the junction of the main and auxiliary grid lines in all film opening areas can be neat, and the film opening precision and efficiency of the battery piece can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of photomasks, and more specifically, to a photomask for laser opening of solar cells. Background Technology

[0002] In the manufacturing of novel photovoltaic cells, such as back-contact (BC) cells and oxide tunneling contact (TOPCon) cells, the removal of the film material on the cell surface by laser ablation has been widely adopted. Unlike the ablation and doping of back-emitter passivated (PERC) cells, the ablation area of ​​BC and TOPCon cells is very large, accounting for about 80% of the total cell area.

[0003] To meet the 1-second CT (Cut-Off Time) requirement for single-cell film opening, a large rectangular laser spot shaped by DOE (Device Optimizer) is needed. This spot reduces the number of scan lines, thereby lowering the CT. However, due to the complex grid structure of TOPCon and BC cells, if an arc-shaped marking method is used to reduce CT during film opening, unevenness can easily occur at the junction of the main and sub-grid lines to be screen-printed or laser-transferred, affecting the subsequent processing results. This unevenness is affected by both the refresh frequency of the galvanometer control card and the frequency of the laser pulse. First, if the galvanometer card refresh frequency is not high enough, the response time is long, and the laser output cannot be quickly turned off and on at the junction of the main and sub-grid lines to be screen-printed or laser-transferred, thus causing unevenness. Second, even if the galvanometer control card response is fast enough, if the laser pulse frequency is not high enough, the dot spacing of the laser pulses hitting the cell will be relatively large. Even one extra or one less pulse will cause obvious unevenness at the junction of the main and sub-grid lines to be screen-printed. While increasing the laser frequency to the 10MHz range is achievable, it's difficult to achieve high single-pulse energy at such high frequencies, which contradicts the high pulse energy required for large-spot laser decoupling. Therefore, an alternative large-spot laser decoupling technology route that can achieve high-precision alignment is needed. Utility Model Content

[0004] To address at least one of the aforementioned technical problems, this application provides a photomask, the specific technical solution of which is as follows:

[0005] A photomask for laser opening of solar cells includes a rectangular substrate, on which N light-transmitting units are spaced apart along a first direction, and the spacing between two adjacent light-transmitting units is greater than or equal to the width of the main grid line of the solar cell to be produced.

[0006] Each light-transmitting unit includes M rectangular light-transmitting slots spaced apart along the second direction. Each light-transmitting slot corresponds to the area between adjacent sub-busbars of the battery cell to be produced. The long side of the light-transmitting slot is less than or equal to the length of the sub-busbar of the battery cell to be produced, and the long side of the light-transmitting slot is parallel to the first direction. The short side of the light-transmitting slot is less than or equal to the spacing between adjacent sub-busbars of the battery cell to be produced, and the short side of the light-transmitting slot is parallel to the second direction.

[0007] Wherein, N≥2, M≥2, the first direction is parallel to one side of the substrate, and the second direction is perpendicular to the first direction.

[0008] The photomask of this application is placed on the solar cell to be processed. Then, a laser beam is controlled by a galvanometer to pass through the light-transmitting grooves on the photomask and scan the solar cell to be processed. The areas between adjacent sub-grid lines and between main and sub-grid lines of the solar cell to be processed are opened. The non-light-transmitting groove areas can effectively block the laser from reaching the areas of the solar cell to be processed that do not need to be opened during the opening process. Therefore, even if the laser scans to the non-light-transmitting groove areas, it will not pass through the non-light-transmitting groove areas to reach the solar cell to be processed. It can be seen that by using the photomask provided in this application to laser open the solar cell to be processed, there is no need to consider factors such as the galvanometer refresh rate, the laser response speed, and the laser pulse frequency. It can achieve neat edges at the junctions of main and sub-grid lines in all opening areas, which can effectively improve the opening accuracy and efficiency of the solar cell.

[0009] In some embodiments, for any two light-transmitting slots located in the same light-transmitting unit, the long side length of the light-transmitting slot farther from the geometric center of the substrate is greater than the long side length of the light-transmitting slot closer to the geometric center of the substrate, and / or, the short side length of the light-transmitting slot farther from the geometric center of the substrate is greater than the short side length of the light-transmitting slot closer to the geometric center of the substrate.

[0010] The short edge of the light-transmitting groove will block some light. By setting the long side length of the light-transmitting groove farther from the geometric center of the substrate to be greater than the long side length of the light-transmitting groove closer to the geometric center of the substrate, it can be ensured that the actual film opening length through the light-transmitting groove farther from the geometric center of the substrate is consistent with the target length in the first direction. Similarly, the long edge of the light-transmitting groove will also block some light. By setting the short side length of the light-transmitting groove farther from the geometric center of the substrate to be greater than the short side length of the light-transmitting groove closer to the geometric center of the substrate, it can be ensured that the actual film opening width through the light-transmitting groove farther from the geometric center of the substrate is consistent with the target width in the second direction.

[0011] In some embodiments, the photomask is used in conjunction with the galvanometer and laser system to perform laser delamination on the solar cell to be processed, wherein:

[0012] The geometric center of the substrate is aligned with the geometric center of the cell to be processed, and the zero point of the beam emitted by the laser system is aligned with the geometric center of the substrate.

[0013] The length of the long side of the light-transmitting groove is determined based on the following formula:

[0014] L=l+d*tan(Θ y -η y );

[0015] η y =tan -1 ((n-n0) / 2f));

[0016] The length of the shorter side of the light-transmitting groove is determined based on the following formula:

[0017] W = w + d * tan(Θ) x -η x );

[0018] η x =tan -1 ((m-m0) / 2f));

[0019] Where L is the length of the long side of the light-transmitting groove; W is the length of the short side of the light-transmitting groove; l is the length of the long side of the standard light-transmitting groove; w is the length of the short side of the standard light-transmitting groove; Θ y Θ is the angle between the component of the centerline of the light beam in the second direction and the normal to the substrate when it sweeps through the light-transmitting groove; x η is the angle between the component of the centerline of the light beam in the first direction and the normal to the substrate when the beam passes through the light-transmitting groove; y η is the cone angle of the component of the beam in the second direction; x denoted by , where is the cone angle of the component of the beam in the first direction; is the initial width of the beam spot in the second direction; is the initial width of the beam spot in the first direction; is the width of the focused beam spot in the second direction; is the width of the focused beam spot in the first direction; is the focal length of the laser system; and is the thickness of the substrate.

[0020] Due to factors such as substrate thickness, the angle at which the beam sweeps across the light-transmitting groove, the size of the beam spot before and after focusing, and the focal length of the laser system, only the standard light-transmitting groove centered at the geometric center of the quasi-substrate has no shadow at its edge facing the galvanometer; shadows exist at the edges of the light-transmitting grooves facing the galvanometer at other locations. The size of the shadowed area can be calculated based on parameters such as substrate thickness, the angle at which the beam sweeps across the light-transmitting groove, the size of the beam spot before and after focusing, and the focal length of the laser system. After obtaining the dimensions of the shadowed areas along the long and short sides of the light-transmitting groove, compensation can be applied to the lengths of the long and short sides of the light-transmitting groove, ultimately ensuring that the actual mold opening length and width after passing through each light-transmitting groove on the substrate are consistent with the target length and width.

[0021] In some embodiments, the thickness of the substrate satisfies:

[0022] d≤min(n / tan(Θ y -η y ), m / tan(Θ x -η x )).

[0023] By adjusting the thickness of the substrate, it is ensured that there are no gaps between adjacent scan lines in the shadow area of ​​the light-transmitting groove.

[0024] In some embodiments, within the same light-transmitting unit, light-transmitting slots located on the same side of the geometric center of the substrate are continuously divided into P groups, wherein: each light-transmitting slot group includes at least one light-transmitting slot, and the specified side lengths of each light-transmitting slot within the same light-transmitting slot group are equal, the specified side being the long side and / or short side of the light-transmitting slot; the specified side length of the light-transmitting slots in the light-transmitting slot group farther from the geometric center of the substrate is greater than the specified side length of the light-transmitting slots in the light-transmitting slot group closer to the geometric center of the substrate;

[0025] Where P≥2.

[0026] Due to the influence of shadow areas, to ensure that the actual opening length and width of each light-transmitting groove in the same light-transmitting unit are the same, it is necessary to accurately calculate the shadow of each light-transmitting groove, then determine the long and short side dimensions of each light-transmitting groove based on the calculation results, and finally carry out precise fabrication of each light-transmitting groove. This process increases the workload and cost of mask fabrication. However, by continuously dividing the light-transmitting grooves located on the same side of the geometric center of the substrate in the same light-transmitting unit into P groups, and setting the specified side length of each light-transmitting groove in each group to be equal, the actual opening length and / or thickness of each light-transmitting groove in the same light-transmitting unit can be kept within an acceptable range, while reducing the workload and cost of mask fabrication.

[0027] In some embodiments, each group of light-transmitting slots includes at least two consecutively arranged light-transmitting slots, and the number of light-transmitting slots included in each group of light-transmitting slots may be equal or unequal.

[0028] Each group of light-transmitting slots contains at least two consecutively arranged light-transmitting slots, which can further reduce the workload and cost of mask fabrication.

[0029] In some embodiments, the short edges of the light-transmitting grooves in the same light-transmitting unit that are away from the geometric center of the substrate are aligned.

[0030] This configuration allows the short edges of multiple open-film areas generated by the same light-transmitting unit on the solar cell to be aligned, away from the center of the solar cell.

[0031] If the dimensions of each light-transmitting groove in the same light-transmitting unit are precisely calculated and set using the shadow compensation formula, the short edges of multiple open-film areas generated by the same light-transmitting unit on the solar cell near the center of the solar cell can also be aligned, preventing over-etching of the solar cell to be processed during the subsequent cleaning process and avoiding affecting the power generation efficiency of the solar cell to be produced due to over-etching.

[0032] In some embodiments, the substrate is a substrate of a soft material that can be laser-etched, or a substrate of a hard material that can be laser-cut.

[0033] Soft material substrates are lightweight and highly flexible, allowing them to be placed directly on photovoltaic cells. Rigid material substrates are highly rigid, less prone to deformation, and offer guaranteed precision.

[0034] In some embodiments, a reflective film is deposited on the upper surface of the substrate and the inner wall of the light-transmitting groove. The thickness of the reflective film is 10-100 nanometers, and the reflectivity of the reflective film is 30%-99.5%.

[0035] By depositing a reflective film on the upper surface of the substrate and the inner wall of the light-transmitting groove, the substrate material is protected against oxidation, and light loss is reduced. This allows the light emanating from the inner wall of the light-transmitting groove to pass through the groove and reach the solar cell as much as possible after reflection, thereby improving the film removal efficiency.

[0036] In some embodiments, the reflective film is a chromium film or a titanium film.

[0037] Both chromium thin films and titanium thin films have excellent reflective properties and can be firmly attached to the substrate surface. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the mask plate structure in the embodiments of this application;

[0039] Figure 2 This is a schematic diagram of a parallel beam scanning the edge of a light-transmitting groove.

[0040] Figure 3 A schematic diagram illustrating the process of focusing a light beam to scan the edge of a light-transmitting groove.

[0041] Figure 4 A schematic diagram of the shadow cast when a light beam sweeps across a portion of the edge of a light-transmitting groove on a mask plate in an embodiment of this application;

[0042] Figure 5 This is a schematic diagram of the mask plate in another embodiment of this application;

[0043] Figure 6 This is a simplified schematic diagram of the main and auxiliary busbars of a solar cell to be manufactured. Detailed Implementation

[0044] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0046] The manufacturing process of photovoltaic cells mainly includes several steps such as silicon wafer cleaning, diffusion junction formation, coating, and laser grooving. Among these steps, laser grooving is usually performed after the formation of the surface passivation layer. It utilizes the instantaneous pulse thermal effect of a laser to selectively remove the passivation film layer on the cell surface. Its main purpose is to remove the passivation film from the cell surface, allowing the silver-aluminum paste to fully contact the silicon substrate, thereby improving the fill factor and open-circuit voltage of the cell and enhancing its overall performance.

[0047] Main grid lines and sub-grid lines are important components of the solar cell electrodes. Main grid lines are typically thicker, used to collect current from the inside of the cell to the external leads, while sub-grid lines are thinner, primarily used to collect photogenerated carriers and transfer them to the main grid lines. Main grid lines are usually located above the surface of the solar cell, while sub-grid lines are distributed between them, forming a grid structure. In the production process from silicon wafer to solar cell, the raw silicon wafer undergoes a series of processing steps. The term "solar cell to be produced" in this application refers to a solar cell product with main grid lines and sub-grid lines, ultimately formed after screen printing or laser transfer. "Solar cell to be processed" refers to a wafer that has undergone one or more processing steps in the process from silicon wafer to solar cell, or at least a wafer that has not yet undergone screen printing or laser transfer.

[0048] As described in the background section, existing cell film-opening processes are prone to unevenness at the junction of the main grid lines and sub-grid lines to be screen-printed or laser-transferred, which affects the effect of subsequent processes.

[0049] To address this issue, this application provides a mask for laser decoupling of solar cells. It can be used in conjunction with a galvanometer and a laser system to perform laser decoupling on the solar cells to be processed, thereby removing the film layer outside the areas where the main grid lines and sub-grid lines to be screen-printed or laser-transferred are located on the surface of the solar cells.

[0050] Figure 1 The structure of a mask plate for laser film cutting of battery cells according to an embodiment of this application is shown. It is necessary to explain here that... Figure 1 All subsequent structural diagrams of photomasks are merely illustrative, intended only to demonstrate the main structural features of the photomask. They are not actual, usable photomask diagrams. For example, the relative area ratio of the light-transmitting groove to the blocking area between adjacent light-transmitting grooves, and the length-to-width ratio of the light-transmitting groove, differ from actual photomasks.

[0051] The areas on the substrate surface shown by dashed lines and dashed frames, corresponding to the sub-grid lines and main grid lines on the solar cell to be produced, and the geometric center of the substrate shown by dots, are all auxiliary markings to help those skilled in the art better understand the structure of the mask; they are not actual patterns existing on the substrate of the mask. Furthermore, before the film-opening operation in this application is performed, the sub-grid lines and main grid lines have not yet been screen-printed or laser-transferred onto the solar cell; that is, the film-opening operation in this application is for the solar cell to be processed.

[0052] like Figure 1 As shown, the mask plate for laser opening of battery cells (hereinafter referred to as mask plate) in the embodiment of this application includes a rectangular substrate 1. N light-transmitting units 2 are arranged at intervals along a first direction (such as the X direction) on the substrate 1, and the spacing between two adjacent light-transmitting units is greater than or equal to the width of the main grid line of the battery cell to be produced.

[0053] Each light-transmitting unit 2 includes M rectangular light-transmitting slots 3 spaced apart along a second direction (such as the Y direction). Each light-transmitting slot 3 corresponds to the area between adjacent sub-busbars of the solar cell to be produced. The long side of the light-transmitting slot is less than or equal to the length of the sub-busbar of the solar cell to be produced. The long side of the light-transmitting slot 3 is parallel to the first direction. The short side of the light-transmitting slot is less than or equal to the spacing between adjacent sub-busbars of the solar cell to be produced. The short side of the light-transmitting slot is parallel to the second direction.

[0054] Wherein, N≥2, M≥2, the first direction is parallel to one side of substrate 1, and the second direction is perpendicular to the first direction. It should be noted that the substrate in this application can be square or rectangular, without specific limitation.

[0055] It should be noted that, please refer to... Figure 6The sub-gate lines are set perpendicular to the main gate line 51. In this application, the "spacing between adjacent sub-gate lines" refers to the vertical distance between the opposite sides of two adjacent sub-gate lines, that is, the vertical distance between the side of sub-gate line 41 facing sub-gate line 42 and the side of sub-gate line 42 facing sub-gate line 41, rather than the vertical distance between the central axis of sub-gate line 41 and the central axis of sub-gate line 42.

[0056] Figure 1 In the illustrated embodiment, four light-transmitting units 2 are spaced apart on the substrate 1, i.e., N=4. Each light-transmitting unit 2 includes 16 light-transmitting slots 3, i.e., M=16. Of course, in other embodiments, the substrate 1 may also have 2, 3, 5, 6, or other numbers of light-transmitting units 2, and each light-transmitting unit 2 may also include 2, 3, 4, 5, 6, 15, 17, 18, or other numbers of light-transmitting slots 3.

[0057] The mask in this embodiment can be used with a galvanometer and a laser system to perform laser cutting on the battery cell to be processed. That is, the mask is placed on the battery cell to be processed, and then the laser beam emitted by the laser system is controlled by the galvanometer to pass through the light-transmitting groove 3 on the substrate 1 to scan and groove the battery cell to be processed.

[0058] Figure 1 The areas where the dashed lines 4 on the substrate 1 are located correspond to the areas where the sub-busbars are located on the solar cell to be produced. Figure 1 The areas marked by dashed frames 5 on the substrate 1 correspond to the areas where the main grid lines are located on the solar cell to be produced. A light beam passes through the light-transmitting groove 3 and illuminates the solar cell to be processed, removing the film layer from the irradiated area. The film layer in the areas not covered by the light-transmitting groove, i.e., the areas where the sub-grid lines and main grid lines corresponding to the solar cell to be produced are located, is retained. Subsequently, metal material will be printed onto these areas where the film layer is retained through screen printing or laser transfer to form the sub-grid lines and main grid lines.

[0059] The mask, in conjunction with a galvanometer and laser system, of this application embodiment performs laser decoupling on the solar cell to be processed. Since the non-decoupling areas (the areas where the sub-grid lines and main grid lines to be screen-printed) on the solar cell are blocked by the non-transparent groove areas of the mask, these non-transparent groove areas effectively prevent the laser from reaching the areas of the solar cell that do not require decoupling during the decoupling process. Therefore, even if the laser scans to the non-transparent groove areas, it will not pass through them to reach the solar cell. It is evident that the mask prepared using the method described in this application, when performing laser decoupling on the solar cell, eliminates the need to consider factors such as the galvanometer refresh rate, laser response speed, and laser pulse frequency. This ensures neat edges at the junctions of the main and sub-grid lines in all decoupling areas, effectively improving the decoupling accuracy of the solar cell.

[0060] like Figure 2As shown, when the light beam 6 sweeps across the light-transmitting groove 3 on the substrate 1 under the control of the galvanometer, and performs laser film opening on the solar cell, there will be an angle θ less than 90° between the center line 61 of the light beam 6 and the normal of the substrate 1. This causes a shadow Se to appear at the edge of the light-transmitting groove 3 facing the galvanometer (i.e., the side of the light-transmitting groove 3 away from the geometric center of the substrate). The presence of the shadow Se causes the light-transmitting size of the light-transmitting groove 3 (i.e., the size through which the light beam can pass) to be smaller than the actual size of the light-transmitting groove 3 (i.e., the actual physical size of the light-transmitting groove 3).

[0061] Without considering the taper of beam 6, that is, assuming that the outermost ray 62 of beam 6 is parallel to the center line 61 of beam 6, beam 6 is a parallel beam. In this case, as... Figure 2 As shown, the size of the shadow Se can be calculated from the substrate thickness d and the aforementioned included angle θ, specifically:

[0062] Se = d * tanθ.

[0063] However, as Figure 3 As shown, the beam 6 used for opening the film is generally a focused beam converged by a laser system. Beam 6 has a certain taper; therefore, when calculating the size of the shadow Se, the influence of the taper on the size of the shadow Se must also be considered. The taper is defined as the angle between the outermost ray 62 of beam 6 and the centerline 61 of beam 6, as shown below. Figure 2 The included angle η. This included angle η can be calculated from the initial width b of the beam 6 spot, the width a of the focused spot, and the focal length f of the laser system, specifically as follows:

[0064] η = tan -1 ((ba) / 2f)).

[0065] After taking the taper into account, the formula for calculating the size of the shadow Se is revised as follows:

[0066] Se = d*tan(θ-η).

[0067] From the formula for calculating the size of the shadow Se, it can be seen that for any two light-transmitting slots 3 in the same light-transmitting unit 2, the shadow of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 is larger than that of the light-transmitting slot 3 closer to the geometric center 11 of the substrate 1. That is, as Figure 4 As shown, the size of the shadow Se in the light-transmitting groove 3 that is farther from the geometric center 11 of the substrate 1 is larger than the size of the shadow Se in the light-transmitting groove 3 that is closer to the geometric center 11 of the substrate 1.

[0068] To improve the consistency of light transmission dimensions of each light-transmitting groove 3 in the first and second directions within the same light-transmitting unit 2, an optional solution is to select the dimensions of the light-transmitting groove 3 according to the actual film-opening requirements as follows:

[0069] For any two light-transmitting slots 3 in the same light-transmitting unit 2, the long side length of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be set to be greater than the long side length of the light-transmitting slot closer to the geometric center 11 of the substrate 1. In this way, the partial light blocking by the short side edge of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be compensated, and the consistency of the light transmission size of each light-transmitting slot 3 in the same light-transmitting unit 2 in the first direction can be improved, ensuring that the actual film opening length after the film opening process of each light-transmitting slot 3 in the same light-transmitting unit 2 is consistent with the target length.

[0070] For any two light-transmitting slots 3 in the same light-transmitting unit 2, the shorter side length of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be set to be greater than the shorter side length of the light-transmitting slot 3 closer to the geometric center 11 of the substrate 1. In this way, the partial light blocking by the long side edge of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be compensated, ultimately improving the consistency of the light transmission size of each light-transmitting slot 3 in the same light-transmitting unit 2 in the second direction, and ensuring that the actual film-opening width after the film-opening treatment of each light-transmitting slot 3 in the same light-transmitting unit 2 is consistent with the target width.

[0071] For any two light-transmitting slots 3 in the same light-transmitting unit 2, the long side length of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be set to be greater than the long side length of the light-transmitting slot 3 closer to the geometric center 11 of the substrate 1, and the short side length of the light-transmitting slot 3 farther from the geometric center 11 of the substrate 1 can be set to be greater than the short side length of the light-transmitting slot 3 closer to the geometric center 11 of the substrate 1. In this way, the consistency of the light transmission dimensions of each light-transmitting slot 3 in the same light-transmitting unit 2 in the first direction and the second direction can be improved, ensuring that the actual film opening length and width after the film opening process of each light-transmitting slot 3 in the same light-transmitting unit 2 are consistent with the target length and width.

[0072] Optionally, when using the mask plate, galvanometer, and laser system in this embodiment to perform laser film opening on the battery cell to be processed, the geometric center 11 of the substrate 1 is aligned with the geometric center of the battery cell to be processed, and the zero point of the beam 6 emitted by the laser system is aligned with the geometric center 11 of the substrate.

[0073] Optionally, in the embodiments of this application, the dimensions of each light-transmitting groove 3 on the flooding plate are precisely set according to the modified shadow Se size calculation formula mentioned above. Specifically:

[0074] The length of the long side of the light-transmitting groove 3 is determined based on the following formula:

[0075] L=l+d*tan(Θ y -η y );

[0076] ηy =tan -1 ((n-n0) / 2f));

[0077] The length of the short side of the light-transmitting groove 3 is determined based on the following formula:

[0078] W = w + d * tan(Θ) x -η x );

[0079] η x =tan -1 ((m-m0) / 2f));

[0080] Where L is the length of the long side of the light-transmitting groove; W is the length of the short side of the light-transmitting groove; l is the length of the long side of the standard light-transmitting groove; w is the length of the short side of the standard light-transmitting groove; Θ y Θ is the angle between the component of the centerline of the light beam in the second direction and the normal to the substrate when it sweeps through the light-transmitting groove 3; x η is the angle between the component of the centerline of the light beam in the first direction and the normal to the substrate when the beam passes through the light-transmitting groove; y η is the cone angle of the component of the beam in the second direction; x denoted by , where is the cone angle of the component of the beam in the first direction; is the initial width of the beam spot in the second direction; is the initial width of the beam spot in the first direction; is the width of the focused beam spot in the second direction; is the width of the focused beam spot in the first direction; is the focal length of the laser system; and is the thickness of the substrate.

[0081] The standard light-transmitting groove refers to the light-transmitting groove whose center is aligned with the zero point of the laser beam 6 emitted by the laser system. When the laser beam 6 scans the standard light-transmitting groove, it will not cast shadows at its edges. Therefore, the light-transmitting area of ​​the standard light-transmitting groove is exactly equal to its actual area. Of course, when the main and auxiliary grid lines of the solar cell to be produced are arranged differently, the standard light-transmitting groove is not necessarily the actual light-transmitting groove to be formed on the photomask; it can also be a reference standard groove.

[0082] The length l of the long side and the length w of the short side of the standard light-transmitting groove can be predetermined by the specific dimensions of the film-opening area. The length and short side dimensions of each light-transmitting groove 3 on the substrate can be obtained by performing shadow compensation on the length and short side dimensions of the standard light-transmitting groove. The compensation amount is the size of the shadow Se at the corresponding edge of the light-transmitting groove 3.

[0083] After performing shadow size compensation on each light-transmitting groove 3 on the substrate 1, the light-transmitting groove 3 is then fabricated. This ensures that the light-transmitting size of all light-transmitting grooves 3 on the substrate 1 is consistent with the light-transmitting size of the standard light-transmitting groove, thereby maximizing the film-opening accuracy. This solves the problem of unevenness at the junction of the main and secondary grid lines, and makes the shape and size of the film-opening area generated by all light-transmitting grooves 3 consistent.

[0084] Furthermore, to ensure that no gaps appear between adjacent scan lines near the shadow area of ​​the light-transmitting groove 3 under extreme conditions, the substrate thickness may optionally meet the following requirements:

[0085] d≤min(n / tan(Θ y -η y ), m / tan(Θ x -η x That is, the thickness of the substrate is less than or equal to n / tan(Θ). y -η y ), m / tan(Θ x -η x The minimum of the two.

[0086] To reduce the workload and cost of mask fabrication, optionally, within the same light-transmitting unit 2, the light-transmitting grooves 3 located on the same side of the geometric center 11 of the substrate 1 are continuously divided into P groups, wherein: each light-transmitting groove group contains at least one light-transmitting groove 3, and the specified side lengths of each light-transmitting groove 3 within the same light-transmitting groove group are equal, the specified side being the long side and / or short side of the light-transmitting groove 3. The specified side length of the light-transmitting groove 3 in the light-transmitting groove group farther from the geometric center 11 of the substrate 1 is greater than the specified side length of the light-transmitting groove in the light-transmitting groove group closer to the geometric center of the substrate, wherein P≥2.

[0087] It should be noted that the "light-transmitting groove 3 located on the same side of the geometric center 11 of the substrate 1" mentioned above in this application refers to a light-transmitting groove located in the same quadrant of the reference XY coordinate system. The X-axis of the reference XY coordinate system passes through the geometric center 11 and is parallel to the first direction, and the Y-axis passes through the geometric center 11 and is parallel to the second direction.

[0088] For example, Figure 5 In the embodiment shown, in the same light-transmitting unit 2, the eight light-transmitting grooves 3 located on the same side of the geometric center 11 of the substrate 1 are continuously divided into three groups (i.e., P=3), with the designated side being the long side and the short side.

[0089] The first group of light-transmitting grooves includes two consecutive light-transmitting grooves 3, with the long side of both light-transmitting grooves 3 having a length of L1 and the short side of both light-transmitting grooves 3 having a length of W1.

[0090] The second group of light-transmitting grooves includes three consecutive light-transmitting grooves 3, the length of the long side of each of the three light-transmitting grooves 3 is L2, and the length of the short side of each of the three light-transmitting grooves 3 is W2.

[0091] The third group of light-transmitting grooves includes three consecutive light-transmitting grooves 3, the long side of each of the three light-transmitting grooves 3 is L3, and the short side of each of the three light-transmitting grooves 3 is W3.

[0092] Where L1 < L2 < L3, W1 < W2 < W3.

[0093] The specified edge can also be only the long edge, for example, still using Figure 5 Taking substrate 1 in the illustrated embodiment as an example, only the long side is specified, that is:

[0094] The length of the long side of the two light-transmitting slots 3 in the first group is L1.

[0095] The length of the long side of each of the three light-transmitting slots 3 in the second group is L2.

[0096] The length of the long side of each of the three light-transmitting slots 3 in the third group is L3.

[0097] Where L1 < L2 < L3.

[0098] The specified edge can also be only the short edge, for example, still using Figure 5 Taking substrate 1 in the illustrated embodiment as an example, only the short side is specified, that is:

[0099] The length of the long side of the two light-transmitting slots 3 in the first group is W1.

[0100] The length of the long side of each of the three light-transmitting slots 3 in the second group is W2.

[0101] The length of the long side of each of the three light-transmitting slots 3 in the third group is W3.

[0102] Among them, W1 < W2 < W3.

[0103] Optionally, for each group of light-transmitting slots, the specified side length of any one of the light-transmitting slots 3 can be calculated using the shading compensation formula described above. This calculated value then serves as the specified side length for all light-transmitting slots in that group. For example, for the two light-transmitting slots 3 in the first group, the specified side length of the first light-transmitting slot 3-1 can be calculated using the shading compensation formula. In other words, for each group of light-transmitting slots, only the length of the specified side needs to be calculated once, thereby reducing the workload and cost of mask fabrication.

[0104] Of course, instead of using the shadow compensation formula described above to calculate the specified side length corresponding to each group of light-transmitting grooves, the specified side length corresponding to each group of light-transmitting grooves can be determined by experience or other methods, as long as the difference in light transmission size of each light-transmitting groove 3 in the same light-transmitting unit is kept within the predetermined range and the film opening accuracy requirement is met.

[0105] In the same light-transmitting unit 2, the light-transmitting grooves 3 located on the same side of the geometric center 11 of the substrate 1 are continuously divided into P groups. The specified side lengths of each light-transmitting groove 3 in each group are set to be equal, so that the difference in light transmission size on the specified side of each light-transmitting groove 3 in the same light-transmitting unit 2 is kept within a predetermined range, and the workload and cost of mask preparation can be reduced.

[0106] In other embodiments, the number of light-transmitting slots 3 located on the same side of the geometric center 11 of the substrate 1 can be set to 2 groups, 4 groups, 5 groups, etc., depending on the number of light-transmitting slots 3 on the substrate 1. The specific number of light-transmitting slots 3 included in each group can be flexibly set. In order to further reduce the workload and cost of mask fabrication, each group of light-transmitting slots includes at least two consecutively arranged light-transmitting slots 3. The number of light-transmitting slots included in each group of light-transmitting slots can be equal or unequal.

[0107] Optionally, the short edges (i.e., the short edges of the light-transmitting grooves 3 without shadows) of each light-transmitting groove 3 in the same light-transmitting unit 2, away from the geometric center 11 of the substrate 1, are aligned. For example, as Figure 4 As shown, the short edges of the light-transmitting grooves 3 of the first light-transmitting unit 2 located on the first side of the geometric center 11, away from the geometric center 11 of the substrate 1, are all located on the first straight line L1. The short edges of the light-transmitting grooves 3 of the first light-transmitting unit 2 located on the second side of the geometric center 11, away from the geometric center 11 of the substrate 1, are all located on the second straight line L2. The first straight line L1 and the second straight line L2 are both parallel to the second direction.

[0108] With this configuration, the short edges of multiple open-film areas generated by the same light-transmitting unit 2 on the solar cell can be aligned away from the center of the solar cell.

[0109] Of course, if the dimensions of each light-transmitting groove 3 in the same light-transmitting unit 2 are precisely calculated and set according to the shadow compensation formula in the above embodiment, then the short edges of the multiple open-film areas generated by the same light-transmitting unit 2 on the solar cell near the center of the solar cell can also be aligned, that is, the two short edges of the multiple open-film areas generated by the same light-transmitting unit 2 on the solar cell are aligned respectively. This prevents the solar cell to be processed from being over-etched during the subsequent cleaning process, and avoids affecting the power generation efficiency of the solar cell to be produced due to over-etching.

[0110] If the dimensions of each light-transmitting groove 3 in the same light-transmitting unit 2 are set according to the grouping method (P group) in the above embodiment, then the short edges of the multiple open film areas generated by the same light-transmitting unit 2 on the battery cell are staggered near the center of the battery cell, and the staggered distance meets the predetermined requirements.

[0111] In this embodiment, the substrate 1 of the photomask can be a substrate of a flexible material that can be laser-etched. The light-transmitting grooves 3 can be fabricated on the substrate 1 using a laser etching process to obtain the photomask. The photomask made from the flexible material substrate is lightweight and highly flexible, and can be directly placed on photovoltaic cells.

[0112] In this embodiment, the substrate 1 of the mask can also be a substrate of a rigid material that can be directly cut by a laser. The light-transmitting grooves 3 can be directly etched into the substrate 1 using a laser to obtain the mask. Masks made from rigid material substrates have high rigidity, are not easily deformed, and ensure precision.

[0113] Optionally, a reflective film is deposited on the upper surface of the substrate 1 and the inner wall of the light-transmitting groove 3. The thickness of the reflective film is 10-100 nanometers, and the reflectivity of the reflective film is 30%-99.5%. For example, the thickness of the reflective film is 10 nanometers, 20 nanometers, 30 nanometers, 90 nanometers, 100 nanometers, etc., and the reflectivity of the reflective film is 30%, 40%, 60%, 95%, 99.5%, etc.

[0114] By depositing a reflective film on the upper surface of the substrate 1 and the inner wall of the light-transmitting groove, the substrate of the substrate 1 is protected against oxidation, and light loss is reduced. This allows the light emanating from the inner wall of the light-transmitting groove 3 to pass through the light-transmitting groove 3 as much as possible after reflection and reach the solar cell, thereby improving the film removal efficiency.

[0115] Optionally, the reflective film can be a chromium film or a titanium film. Both types of reflective films have excellent reflective properties and can be firmly attached to the surface of the substrate 1.

[0116] Based on the same inventive concept, this application also provides a method for preparing a mask for laser laser encapsulation of battery cells (hereinafter referred to as the preparation method), which includes:

[0117] A rectangular substrate is provided.

[0118] N light-transmitting units are fabricated on a substrate using a laser, wherein:

[0119] N light-transmitting units are arranged at intervals along a first direction on the substrate, and the distance between two adjacent light-transmitting units is greater than or equal to the width of the main grid line of the cell to be produced; each light-transmitting unit includes M rectangular light-transmitting slots arranged at intervals along a second direction, each light-transmitting slot corresponding to the area between adjacent sub-grid lines of the cell to be produced, the long side of the light-transmitting slot is less than or equal to the length of the sub-grid line of the cell to be produced, the long side of the light-transmitting slot is parallel to the first direction, the short side of the light-transmitting slot is less than or equal to the distance between adjacent sub-grid lines of the cell to be produced, and the short side of the light-transmitting slot is parallel to the second direction;

[0120] Wherein, N≥2, M≥2, the first direction is parallel to one side of the substrate, and the second direction is perpendicular to the first direction.

[0121] The mask prepared in this embodiment can be used in conjunction with a galvanometer and a laser system to perform laser decoupling on the solar cell to be processed. Since the non-decoupling areas of the solar cell to be processed are blocked by the non-transparent groove area of ​​the mask, the edges at the junctions of the main and auxiliary grid lines in all decoupling areas are neat, avoiding unevenness.

[0122] Compared to existing solar cell opening processes, the use of the mask prepared in this application embodiment, in conjunction with a galvanometer and a laser system, to perform laser opening on the solar cell can effectively improve the opening accuracy and efficiency of the solar cell.

[0123] The preparation method of this application embodiment can be used to prepare the mask plate in the various embodiments or any combination of embodiments described above. Since the various optional structures of the mask plate have been described in detail above, they will not be repeated here.

[0124] Optionally, the preparation method in this application embodiment further includes: depositing a reflective film on the upper surface of the substrate and the inner wall of the light-transmitting groove, wherein the thickness of the reflective film is 10-100 nanometers and the reflectivity of the reflective film is 30%-99.5%. For example, the thickness of the reflective film is 10 nanometers, 20 nanometers, 30 nanometers, 90 nanometers, 100 nanometers, etc., and the reflectivity of the reflective film is 30%, 40%, 60%, 95%, 99.5%, etc.

[0125] By depositing a reflective film on the upper surface of substrate 1 and the inner wall of the light-transmitting groove, the substrate material is protected against oxidation, and light loss is reduced. This allows the light emanating from the inner wall of the light-transmitting groove to pass through the groove and reach the solar cell as much as possible after reflection, thereby improving the film removal efficiency.

[0126] One optional coating method involves first processing N light-transmitting units on a substrate using a laser, and then coating a reflective film on the upper surface of the substrate and the inner wall of the light-transmitting groove. This allows for the coating of the upper surface of the substrate and the inner wall of the light-transmitting groove to be completed in a single operation, improving coating efficiency.

[0127] Alternatively, a reflective film can be deposited on the upper surface of the substrate first, and then N light-transmitting units can be processed on the substrate using a laser. Finally, a reflective film is deposited on the inner wall of the light-transmitting groove. In this way, a secondary coating is applied to the upper surface of the substrate, which enhances the coating's adhesion, extends its lifespan, and improves the reflective film's protective effect on the substrate.

[0128] The foregoing has provided a sufficiently detailed and specific description of this application. Those skilled in the art should understand that the descriptions in the embodiments are merely exemplary, and all changes made without departing from the true spirit and scope of this application should fall within the protection scope of this application. The scope of protection claimed in this application is defined by the claims, and not by the above descriptions in the embodiments.

Claims

1. A photomask for laser encapsulation of solar cells, characterized in that, The mask includes a rectangular substrate, on which N light-transmitting units are spaced apart along a first direction, and the spacing between two adjacent light-transmitting units is greater than or equal to the width of the main grid line of the battery cell to be produced. Each of the light-transmitting units includes M rectangular light-transmitting slots spaced apart along the second direction. Each light-transmitting slot corresponds to the area between adjacent sub-busbars of the battery cell to be produced. The long side of the light-transmitting slot is less than or equal to the length of the sub-busbar of the battery cell to be produced. The long side of the light-transmitting slot is parallel to the first direction. The short side of the light-transmitting slot is less than or equal to the spacing between adjacent sub-busbars of the battery cell to be produced. The short side of the light-transmitting slot is parallel to the second direction. Wherein, N≥2, M≥2, the first direction is parallel to one side of the substrate, and the second direction is perpendicular to the first direction.

2. The photomask for laser film cutting of battery cells as described in claim 1, characterized in that, Any two light-transmitting slots located in the same light-transmitting unit The long side length of the light-transmitting groove farther from the geometric center of the substrate is greater than the long side length of the light-transmitting groove closer to the geometric center of the substrate, and / or, the short side length of the light-transmitting groove farther from the geometric center of the substrate is greater than the short side length of the light-transmitting groove closer to the geometric center of the substrate.

3. The photomask for laser film cutting of battery cells as described in claim 2, characterized in that, The mask is used in conjunction with the galvanometer and laser system to perform laser exfoliation on the solar cell to be processed, wherein: The geometric center of the substrate is aligned with the geometric center of the cell to be processed, and the zero point of the beam emitted by the laser system is aligned with the geometric center of the substrate. The length of the long side of the light-transmitting groove is determined based on the following formula: L=l+d*tan(Θ y -η y ); η y =tan -1 ((n-n0) / 2f)); The length of the short side of the light-transmitting groove is determined based on the following formula: W=w+d*tan(Θ x -η x ); or x =tan -1 ((m-m0) / 2f)); Where L is the length of the long side of the light-transmitting groove; W is the length of the short side of the light-transmitting groove; l is the length of the long side of the standard light-transmitting groove; w is the length of the short side of the standard light-transmitting groove; Θ y Θ is the angle between the component of the centerline of the light beam in the second direction and the normal to the substrate when it sweeps through the light-transmitting groove; x η is the angle between the component of the centerline of the light beam in the first direction and the normal to the substrate when the beam passes through the light-transmitting groove; y η is the cone angle of the component of the beam in the second direction; x denoted by , where is the cone angle of the component of the beam in the first direction; is the initial width of the beam spot in the second direction; is the initial width of the beam spot in the first direction; is the width of the focused beam spot in the second direction; is the width of the focused beam spot in the first direction; is the focal length of the laser system; and is the thickness of the substrate.

4. The photomask for laser film cutting of battery cells as described in claim 3, characterized in that, The thickness of the substrate satisfies: d≤min(n / tan(Θ y -or y ), m / tan(Θ x -or x ))。 5. The photomask for laser film cutting of battery cells as described in claim 1, characterized in that, In the same light-transmitting unit, the light-transmitting grooves located on the same side of the geometric center of the substrate are continuously divided into P groups, wherein: Each group of light-transmitting slots includes at least one light-transmitting slot. The designated side lengths of each light-transmitting slot within the same group are equal, and the designated side is the long side and / or short side of the light-transmitting slot. The specified side length of the light-transmitting groove in the light-transmitting groove group farther from the geometric center of the substrate is greater than the specified side length of the light-transmitting groove in the light-transmitting groove group closer to the geometric center of the substrate. Where P≥2.

6. The photomask for laser film cutting of battery cells as described in claim 5, characterized in that, Each group of light-transmitting slots contains at least two consecutively arranged light-transmitting slots, and the number of light-transmitting slots in each group may be equal or unequal.

7. The photomask for laser film cutting of solar cells as described in any one of claims 2 to 6, characterized in that, The short edges of each of the light-transmitting grooves in the same light-transmitting unit, away from the geometric center of the substrate, are aligned.

8. The photomask for laser film cutting of battery cells as described in claim 1, characterized in that, The substrate is a substrate of a soft material that can be laser-etched, or the substrate is a substrate of a hard material that can be laser-cut.

9. The photomask for laser film cutting of battery cells as described in claim 1, characterized in that, The upper surface of the substrate and the inner wall of the light-transmitting groove are coated with a reflective film. The thickness of the reflective film is 10-100 nanometers, and the reflectivity of the reflective film is 30%-99.5%.

10. The photomask for laser film cutting of battery cells as described in claim 9, characterized in that, The reflective film is a chromium thin film or a titanium thin film.

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