Photovoltaic module

Abstract

The invention belongs to the field of photovoltaic technology, and particularly relates to a photovoltaic module, which can reduce the stress concentration coefficient of a through hole matched with a mounting bolt, and comprises a battery string; the first adhesive film and the second adhesive film are respectively positioned on two sides of the battery string; the front packaging structure is arranged on the side face, away from the battery string, of the first adhesive film; the cover plate glass is arranged on the side face, away from the battery string, of the second adhesive film, the cover plate glass comprises a first surface and a second surface which are arranged back to back in the thickness direction, and a through hole is formed in the cover plate and comprises a first transition area, a middle round hole area and a second transition area which are communicated in sequence. The aperture of the first transition area is expanded from the middle round hole area and then is opened in the first surface, and the aperture of the second transition area is expanded from the middle round hole area and then is opened in the second surface.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic module. Background Technology

[0002] Currently, most photovoltaic module backsheet glass mounting holes adopt the traditional circular hole design, which results in severe stress concentration at the hole edges. The stress peak can reach 3-5 times the average stress, which can easily lead to glass breakage.

[0003] Traditional circular holes, with a constant diameter, penetrate the entire thickness of the glass. The hole edge abruptly changes direction at a 90-degree angle to the glass body, causing a sharp contraction of stress flow lines at the hole edge. In particular, the superposition of contact stress and thermal stress creates a double stress concentration point. Failure analysis shows that 95% of cracks originate at the hole edge, propagating radially for 5-15 mm before causing the entire plate to fracture.

[0004] Existing stress reduction measures, such as simple chamfering of circular holes, integral tempering, and metal sleeves, suffer from limited effectiveness, high cost, or complex processes. Furthermore, these technologies primarily originate from stress optimization concepts in aerospace, building facades, and mechanical engineering, but are insufficient to meet the comprehensive requirements of photovoltaic applications. Summary of the Invention

[0005] Therefore, it is necessary to provide a photovoltaic module that addresses the stress concentration problem in the mounting holes of the back glass.

[0006] A photovoltaic module includes: a battery string; a first encapsulating film and a second encapsulating film, respectively located on both sides of the battery string; a front encapsulation structure disposed on the side of the first encapsulating film opposite to the battery string; and a cover glass disposed on the side of the second encapsulating film opposite to the battery string. The cover glass includes a first surface and a second surface disposed opposite to each other in the thickness direction. The cover glass has a through hole, which includes a first transition region, a central circular hole region, and a second transition region connected in sequence. The aperture of the first transition region opens onto the first surface after being enlarged from the central circular hole region, and the aperture of the second transition region opens onto the second surface after being enlarged from the central circular hole region.

[0007] In some embodiments, the width of the first transition zone is 1.75 mm to 3 mm in the radial direction of the central circular hole area.

[0008] In some embodiments, the width of the second transition zone is 1.25 mm to 2 mm in the radial direction of the central circular hole area.

[0009] In some embodiments, the first transition region is a frustum region with an inclination angle of 15°-25°.

[0010] In some embodiments, the second transition region is a frustum region with an inclination angle of 15°-25°.

[0011] In some embodiments, the difference between the tilt angle of the first transition region and the tilt angle of the second transition region is within 3°.

[0012] In some embodiments, the length of the second transition region is less than the length of the first transition region in the thickness direction.

[0013] In some embodiments, the thickness of the cover glass is 2.5 mm to 3.2 mm.

[0014] In some embodiments, the cover glass includes a first glass, an adhesive layer, and a second glass layer stacked sequentially, with the central circular hole area penetrating the adhesive layer and passing through the first and second glass layers.

[0015] In some embodiments, the first glass and the second glass have the same thickness, and the first transition region and the second transition region are centrally symmetrical about the thickness direction of the cover glass.

[0016] In some embodiments, the thickness of both the first glass and the second glass is 2.5mm-3.2mm.

[0017] In some embodiments, the aperture of the opening of the first transition region on the first surface is 10-12 mm, and the length in the thickness direction is 0.8 mm-1.2 mm.

[0018] In some embodiments, the diameter of the central circular hole area is 6.5mm-7mm with a tolerance of ±0.05mm, and the length in the thickness direction is 1.0mm-1.5mm.

[0019] In some embodiments, the aperture of the opening of the second transition region on the second surface is 9mm-11mm, and the length in the thickness direction is 0.5mm-1mm.

[0020] In some embodiments, the inner wall surface of the through hole is provided with a chemical tempering layer, which penetrates into the cover glass.

[0021] The aforementioned photovoltaic module divides the through-hole into three parts along the thickness direction of the cover glass. A first transition zone is formed between the central circular hole area and the first surface, and a second transition zone is formed between the central circular hole area and the second surface. This creates a radially varying transition band of a certain width between the central circular hole area and the first surface, and also between the central circular hole area and the second surface, allowing stress to "spread outwards in three dimensions." Both the first and second transition zones form stress buffer zones. This design creates a "double funnel" shaped three-dimensional structure in the thickness direction, no longer a single inclined plane, but a segmented three-dimensional shape with varying depths. Stress testing shows that this solution reduces the stress concentration factor, increases the static load, and thus prevents the cover glass from breaking. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a photovoltaic module according to some embodiments of this application.

[0023] Figure 2 This is a schematic diagram of the cover glass structure in a photovoltaic module according to an embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the cover glass structure in a photovoltaic module according to another embodiment of this application.

[0025] Figure 4 This is a schematic diagram of the cover glass structure in a photovoltaic module according to another embodiment of this application.

[0026] Figure 5 A schematic diagram showing that the inner wall surface of the mounting hole has a chemically tempered layer.

[0027] Figure label:

[0028] 100. Photovoltaic module; 10. Battery string; 20. First encapsulant film; 30. Second encapsulant film; 40. Front encapsulation structure; 50. Cover glass; 510. First surface; 520. Second surface; 530. Through hole; 531. First transition zone; 532. Central circular hole area; 533. Second transition zone; 501. First glass; 502. Second glass; 503. Adhesive layer; 540. Chemical tempering layer. Detailed Implementation

[0029] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0030] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0031] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0034] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0035] As described in the background section, traditional photovoltaic modules suffer from stress concentration issues in their mounting holes, and traditional solutions are ineffective in addressing this problem.

[0036] In response to the above requirements, refer to Figure 1 and Figure 2 This application proposes a photovoltaic module 100, including a battery string 10, a first encapsulating film 20, a second encapsulating film 30, a front encapsulation structure 40, and a cover glass 50. The first encapsulating film 20 and the second encapsulating film 30 are located on opposite sides of the battery string 10. The front encapsulation structure 40 is disposed on the side of the first encapsulating film 20 facing away from the battery string 10. The cover glass 50 is disposed on the side of the second encapsulating film 30 facing away from the battery string 10. The cover glass 50 includes a first surface 510 and a second surface 520 arranged opposite to each other in the thickness direction. The cover glass has a through hole 530, which includes a first transition region 531, a central circular hole region 532, and a second transition region 533 connected in sequence. The aperture of the first transition region 531 opens onto the first surface 510 after being enlarged from the central circular hole region 532. The aperture D2 of the second transition region 533 opens onto the first surface 510 after being enlarged from the central circular hole region 532.

[0037] The battery string 10 includes at least one photovoltaic cell. This embodiment does not limit the structure of the cell, and the types of photovoltaic cells include, but are not limited to, passivated emitter rear cell (PERC), tunnel oxide passivated contact (TOPCon), intrinsic thin-film heterojunction (HJT), interdigitated back contact (IBC), perovskite cells, etc.

[0038] For example, the first film 20 and the second film 30 can be one of the following materials: ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), polyvinyl butyral (PVB), EVA-POE-EVA co-extruded film (EPE), EVA-POE co-extruded film (EP).

[0039] For example, the front-side encapsulation structure 40 can be one of rigid materials such as tempered glass, polyethylene terephthalate (PET), and polycarbonate (PC), or one of flexible materials such as polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF). These materials have high light transmittance, which can improve the photoelectric conversion efficiency of the photovoltaic module 100 and ensure the power output of the photovoltaic module 100. When the photovoltaic module 100 is operating, the front-side encapsulation structure 40 faces the sun.

[0040] In this application, the cover glass 50 is used to form the back-side encapsulation structure of the photovoltaic module 100. When the photovoltaic module 100 is operating, the cover glass 50 faces away from the sun. The first surface 510 is located on the outside of the photovoltaic module 100, facing away from the cell string 10. The thickness direction of the cover glass 50 is also the thickness direction of the photovoltaic module 100, and also the stacking direction of the various components.

[0041] The through hole 530 penetrates the cover glass 50 in the thickness direction and is divided into three parts in the thickness direction. Figure 2Regarding the placement direction of the cover glass 50 as shown, the upper end of the first transition region 531 is connected to the lower edge of the through hole 530, and the lower end of the first transition region 531 penetrates the first surface 510 of the cover glass 50. The lower end of the second transition region 533 is connected to the upper edge of the central circular hole region 532, and the upper end of the second transition region 533 penetrates the second surface 520 of the cover glass 50.

[0042] The central circular hole region 532 is a circular hole with a constant diameter. In the thickness direction, and pointing from the second surface 520 towards the first surface 510, the diameter of the hole in the first transition region 531 tends to increase; the diameter at the junction of the first transition region 531 and the central circular hole region 532 is smaller than the diameter at the center of the first transition region 531, and the diameter at the center of the first transition region 531 is smaller than the diameter of the opening of the first transition region 531 on the first surface 510. In the thickness direction, and pointing from the first surface 510 towards the second surface 520, the diameter of the hole in the second transition region 533 tends to increase; the diameter at the junction of the second transition region 533 and the central circular hole region 532 is smaller than the diameter at the center of the second transition region 533, and the diameter at the center of the second transition region 533 is smaller than the diameter of the opening of the second transition region 533 on the second surface 520.

[0043] In traditional techniques, a bevel is formed around the edge of the mounting hole. However, this method has significant limitations: it is a single-plane treatment, usually only a simple 45° or other angle bevel is made on the glass surface (or one side); it only considers the stress dispersion of the hole edge on a certain plane.

[0044] In this application, by dividing the through-hole 530 into three parts along the thickness direction of the cover glass 50, and simultaneously setting a first transition zone 531 between the central circular hole area 532 and the first surface 510, and a second transition zone 533 between the central circular hole area 532 and the second surface 520, a gradually changing transition zone with a certain width in the radial direction of the central circular hole area 532 is formed between the central circular hole area 532 and the first surface 510, and a gradually changing transition zone with a certain width in the radial direction of the central circular hole area 532 is also formed between the central circular hole area 532 and the second surface 520, allowing stress to "diffuse outward in three dimensions." Both the first transition zone 531 and the second transition zone 533 form stress buffer zones. This design of this application creates a "double funnel" shaped three-dimensional structure in the thickness direction, no longer a single inclined plane, but a segmented three-dimensional shape with varying depths. Stress tests show that using the solution of this application can reduce the stress concentration factor and increase the static load, thereby preventing the cover glass 50 from breaking.

[0045] In addition, when installing bolts through the through hole 530, the bolts are inserted into the through hole 530 from one side of the first surface 510. Transition zones are provided on both sides of the central circular hole area 532, forming a "double-hole" stress transmission channel. External loads are distributed from the first transition zone 531 to the central through hole area 530, and then further distributed through the second transition zone 533, achieving two stress gradient transitions.

[0046] Optionally, the width of the first transition region 531 in the radial direction of the central circular hole region 532 is 1.75mm-3mm. For example, the width of the first transition region 531 is 1.75mm, 2mm, 2.25mm, 2.4mm, or 3mm. Optionally, the width of the second transition region 533 in the radial direction of the central circular hole region 532 is 1.25mm-2mm. For example, the width of the second transition region 533 is 1.25mm, 1.35mm, 1.5mm, 1.9mm, or 2mm.

[0047] The radial direction of the central circular hole region 532 is specifically the X direction in the figure. The width of the first transition region 531 refers to the width L1 of the inner wall of the first transition region 531 in the radial direction of the central circular hole region 532. The inner wall of the first transition region 531 is annular, and the width of the first transition region 531 is the width of the inner wall of the first transition region 531 in the radial direction of the cross-section of the central circular hole region 532.

[0048] Similarly, the width of the second transition region 533 refers to the radial width L2 of the inner wall of the second transition region 533 in the central circular hole region 532. The inner wall of the second transition region 533 is annular, and the width of the second transition region 533 is the radial width of the inner wall of the second transition region 533 in the central circular hole region 532.

[0049] Based on Griffith's theory of fracture mechanics, the critical stress for crack propagation is inversely proportional to the stress gradient. Finite element analysis shows that a 3mm transition zone reduces the stress gradient from 45MPa / mm in the traditional scheme to 18MPa / mm, which is lower than the glass fatigue crack propagation threshold (25MPa / mm).

[0050] Optionally, the first transition region 531 is a frustum-shaped region with an inclination angle α of 15°-25°. Optionally, the second transition region 533 is a frustum-shaped region with an inclination angle β of 15°-25°. (Reference) Figure 1 The inclination angle of the frustum region is the angle between the generatrix of the frustum region and the top or bottom surface.

[0051] According to stress diffusion theory, the natural diffusion angle of a point load in a brittle body is 30°-45°. Setting the tilt angle to less than 60% of the diffusion angle (i.e., <27°) fully utilizes the diffusion effect. Furthermore, the thickness of the back-side encapsulation structure in the photovoltaic module 100 is limited; for example, the thickness D of the cover glass 50 is 2.5mm-3.2mm. Therefore, in this application, the tilt angle is set within the range of 15°-25°. This avoids the transition zone length exceeding the glass thickness due to an excessively small tilt angle, making it impossible to achieve the desired result. Conversely, it avoids an excessively large or steep tilt angle, which would result in insufficient stress reduction and failure to achieve the stress optimization target. Setting the tilt angles of the first transition zone 531 and the second transition zone 533 to 15°-25° achieves an optimal balance between processing efficiency and stress optimization. For example, the tilt angles of the first transition zone 531 and the second transition zone 533 can be 15°, 18°, 20°, 23°, and 25°, respectively.

[0052] In some embodiments, the difference between the tilt angle of the first transition region 531 and the tilt angle of the second transition region 533 is within 3°. For example, the tilt angle difference is 1°, 1.5°, 2°, or 3°.

[0053] As discussed above, the purpose of setting the first transition zone 531 and the second transition zone 533 is to achieve a smooth three-dimensional transition. External loads are distributed from the first transition zone 531 to the central through-hole 530 area, and then further distributed through the second transition zone 533, achieving a two-stage stress gradient transition. In this application, the difference between the tilt angle of the first transition zone 531 and the tilt angle of the second transition zone 533 is kept within 3°, ensuring that the stress flow lines are continuously distributed at the junction of the frustum and avoiding geometrical abrupt changes in the stress transmission path.

[0054] Specifically, if the difference between the tilt angle of the first transition zone 531 and the tilt angle of the second transition zone 533 is too large, taking the first transition zone 531 as an example, a step-like abrupt change will occur at the junction of the first transition zone 531 and the central circular hole area 532, causing the stress flow lines to fail to transition smoothly and resulting in secondary stress concentration at this interface. If the difference is too small, the gradual diffusion effect cannot be fully utilized, which will also lead to excessive local stress peaks and the formation of new stress concentration points / new weak points. A difference of less than 3° between the tilt angle of the first transition zone 531 and the tilt angle of the second transition zone 533 can effectively avoid the above problems.

[0055] The cover glass 50 can be, for example, ultra-clear tempered glass or low-iron float glass. Additionally, see reference... Figure 2In this embodiment, the cover glass 50 is a single-layer glass with a thickness ranging from 2.5mm to 3.2mm, such as 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, and 3.2mm. In the thickness direction, the lengths of the first transition region 531 and the second transition region 533 are equal. Optionally, the first transition region 531 and the second transition region 533 are centrally symmetrical about the thickness direction of the cover glass 50.

[0056] and Figure 2 The embodiment shown differs from the one described above, except that the reference is... Figure 3 In some embodiments, in the thickness direction, the length H3 of the second transition region 533 is less than the length H1 of the first transition region 531.

[0057] In the photovoltaic module 100, the first transition zone 531 faces the external environment of the photovoltaic module 100, while the second transition zone 533 faces the interior of the photovoltaic module 100. The first transition zone 531 directly bears the contact pressure of the mounting bolts. Studies have found that 85% of cracks originate from the outer pressure surface.

[0058] Therefore, in this embodiment, by having different lengths for the second transition region 533 and the first transition region 531 having a longer length than the second transition region 533, the fracture resistance of the first transition region 531 can be improved. Furthermore, given an effective glass thickness, this differentiated length design of the second transition region 533 and the second transition region 533 can improve the fracture resistance of the first transition region 531 while maintaining the length of the central circular hole region 532; it does not reduce the overall stiffness of the cover glass 50.

[0059] In other embodiments, the cover glass 50 may also be double-glazed. (See reference...) Figure 4 The cover glass 50 includes a first glass 501, an adhesive layer 503, and a second glass 502 stacked sequentially. The central circular hole area 532 penetrates the adhesive layer 503 and is disposed in the first glass 501 and the second glass 502.

[0060] The first glass 501 and the second glass 502 are connected by an adhesive layer 503. The material of the adhesive layer 503 may be, for example, one of the following: ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), polyvinyl butyral (PVB), EVA-POE-EVA co-extruded film (EPE), EVA-POE co-extruded film (EP), etc.

[0061] In this embodiment, the through hole 530 still penetrates the entire cover glass 50. The first transition region 531 is formed in the first glass 501; the second transition region 533 is formed in the second glass 502; and the central circular hole region 532 extends into the first glass 501, the adhesive layer 503, and the second glass 502.

[0062] Figure 4 In the illustrated embodiment, with Figure 2 and Figure 3 In contrast, the composition of the cover glass 50 has changed, while the other structures, such as the length in the thickness direction, the width in the radial direction, and the tilt angle of the first transition zone 531 and the second transition zone 533, can be set in exactly the same way.

[0063] Optionally, the first glass 501 and the second glass 502 have the same thickness, and the first transition region 531 and the second transition region 533 are centrally symmetrically arranged about the thickness direction of the cover glass 50. The thickness of both the first glass 501 and the second glass 502 is 2.5mm-3.2mm, such as 2.5mm, 2.6mm, 2.6mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, or 3.2mm.

[0064] The first transition zone 531 and the second transition zone 533 are symmetrically arranged, which allows the stress to be distributed symmetrically in the two glass pieces. The shear stress at the adhesive layer 503 is greatly reduced, eliminating the sudden change in interface stress and effectively preventing delamination.

[0065] Furthermore, the symmetrical arrangement of the first transition zone 531 and the second transition zone 533 enhances thermal cycling adaptability. Specifically, the first transition zone 531 and the second transition zone 533 provide bidirectional strain release space, reducing thermal stress and effectively addressing the differences in thermal expansion coefficients between the first glass 501, the second glass 502, and the adhesive film. The first transition zone 531 and the second transition zone 533 form a symmetrical stress field, ensuring that the load is uniformly transferred through two gradient transitions, thereby improving the overall bending strength.

[0066] The thickness of the adhesive layer 503 is 1.0-1.5mm. Optionally, the thickness of the adhesive layer 503 is 1mm, 1.2mm, 1.3mm, 1.4mm, or 1.5mm.

[0067] In addition, it should be noted that when the cover glass 50 is double-glazed, the first transition zone 531 and the second transition zone 533 can also adopt an asymmetrical design.

[0068] In some embodiments, the opening diameter D1 of the first transition region 531 on the first surface 510 is 10mm-12mm, and its length in the thickness direction is 0.8mm-1.2mm. Optionally, the aperture of the opening of the first transition region 531 is 10mm, 10.5mm, 11mm, or 12mm. The length of the first transition region 531 is 0.8mm, 0.9mm, 1.0mm, 1.1mm, or 1.2mm.

[0069] In some embodiments, the aperture D2 of the central circular hole region 532 is 6.5mm-7mm, with a tolerance of ±0.05mm, and the length H2 in the thickness direction is 1.0mm-1.5mm. Optionally, the aperture D2 of the central circular hole region 532 is 6.5mm, 6.6mm, 6.7mm, 6.8mm, 6.9mm, or 7mm. The length of the central circular hole region 532 is, for example, 1.0mm, 1.1mm, 1.2mm, 1.3mm, or 1.4mm.

[0070] The central circular hole area 532 is used to position and install bolts; the positioning accuracy of the central circular hole area 532 directly affects the stress. In this embodiment, the tolerance is ±0.05mm, that is, the positioning accuracy is ±0.05mm, for example, ±0.01mm, ±0.02mm, ±0.03mm, ±0.04mm, ±0.05mm. Within the above positioning accuracy range, eccentric contact between the bolt and the hole wall of the central circular hole area 532 can be avoided, preventing uneven distribution of local contact stress, ensuring stress surface distribution, and preventing surface stress distribution from degenerating into point contact, thereby reducing the stress concentration factor at the hole edge, improving the stress dispersion effect of the double cone, and reducing the risk of cracking.

[0071] In some embodiments, the opening diameter D3 of the second transition region 533 on the second surface 520 is 9mm-11mm, and its length H3 in the thickness direction is 0.5mm-0.1mm. Preferably, D3 is 9mm-10mm, and H3 is 0.5mm-0.8mm. Optionally, the opening diameter D3 of the second transition region 533 is 9mm, 9.2mm, 9.6mm, 9.8mm, 10mm, 10.5mm, or 11mm, and the length H3 of the second transition region 533 is 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm.

[0072] In some embodiments, the inner wall surface of the through-hole 530 is provided with a chemical tempering layer 540, which penetrates into the cover glass 50. (See reference) Figure 5The inner wall surface of the through hole 530 includes the inner wall surface of the first transition region 531, the inner wall surface of the central circular hole region 532, and the inner wall surface of the second transition region 533. That is, each part of the inner wall surface of the through hole 530 is provided with a chemical tempering layer 540. The chemical tempering layer 540 forms a compressive stress layer on the inner surface of the hole wall, which can improve the static load. The thickness of the chemical tempering layer 540 is 50μm-70μm. Preferably, the thickness of the chemical tempering layer 540 is 55μm-65μm. Optionally, the thickness of the chemical tempering layer 540 is 50μm, 55μm, 60μm, 65μm, or 70μm.

[0073] The method for preparing the cover glass 50 is not limited. Optionally, the cover glass 50 can be formed in the following manner. A method for preparing a cover glass 50 provided in this application includes the following steps.

[0074] S100, providing an intermediate body for the cover glass 50, the intermediate body including a first surface 510 and a second surface 520 disposed opposite to each other in the thickness direction.

[0075] S200, a through hole 530 is formed at a predetermined position, penetrating the first surface 510 and the second surface 520. The through hole 530 includes a first transition region 531, a central circular hole region 532 and a second transition region 533 connected in sequence. The diameter of the hole in the first transition region 531 increases from the central circular hole region 532 and opens into the first surface 510. The diameter of the hole in the second transition region 533 increases from the central circular hole region 532 and opens into the first surface 510.

[0076] In S200, a through hole 530 is formed at a predetermined position, penetrating the first surface 510 and the second surface 520, including:

[0077] S210, forming the first transition zone 531.

[0078] S220, The circular hole area is formed at the bottom of the first transition region 531.

[0079] S230, A second transition region 533 is formed at the end of the circular hole region.

[0080] For example, in a specific implementation, a positioning mark is made on the first surface 510 of the intermediate body. Then, layer processing is performed using waterjet cutting / ultrasonic drilling to form a first transition zone 531, a central circular hole zone 532, and a second transition zone 533. For example, during multi-layer waterjet cutting, the depth of cut can be 0.3-0.5 mm per layer.

[0081] The method for preparing the cover glass 50 described above also includes:

[0082] S300: Grind and polish the inner wall of the through hole 530.

[0083] S400, the inner wall surface of the through hole 530 is tempered to form a chemical tempering layer 540 that penetrates into the cover glass 50.

[0084] In S300, the surface roughness Ra of the inner wall of the through hole 530 is ≤0.8μm. For example, the inner wall surface of the through hole 530 is finely ground and polished using methods such as diamond grinding or laser cutting. The inner wall surface of the through hole 530 includes the inner wall surface of the first transition zone 531, the inner wall surface of the central circular hole region 532, and the inner wall surface of the second transition zone 533. Fine grinding and polishing ensure that the surface roughness Ra is ≤0.8μm, eliminating microcrack sources.

[0085] S400, the thickness of the chemically tempered layer 540 is 60 μm. For example, the processed cover glass 50 is placed in a salt bath of molten potassium nitrate (KNO3), and after a set time, it is removed and cooled.

[0086] Furthermore, it also includes inspection steps. Specifically, a polarizing stress meter is used for quality inspection, and a stress of 60 MPa in the first transition zone 531 and the second transition zone 533 is considered acceptable.

[0087] The technical effects of this application will be further explained below with reference to some of the above embodiments and related comparative examples.

[0088] In this study, cover glass 50 was prepared using both single-layer and double-layer glass, employing the design of this application. In the comparative study, cover glass 50 was prepared using single-layer glass with a constant-diameter circular hole design. Stress tests were performed on the cover glass 50 obtained by the above methods to compare stress concentration factors. Simultaneously, static load tests were conducted to compare static loads.

[0089] The stress testing method specifically involves measuring the stress distribution around the hole using a polarizing stress meter and comparing the stress concentration factors of a traditional circular hole with those of a double transition zone structure. The static load testing method involves applying axial pressure to the mounting hole using a universal testing machine, recording the failure load value, and comparing the increase in load. Multiple samples were tested in the comparative examples and various embodiments of this application to obtain their respective stress concentration factor ranges and static load variations.

[0090] The results are shown in Table 1 below.

[0091] Table 1

[0092]

[0093] illustrate:

[0094] The units for all dimensions in Table 1 are mm. In Examples 1-5, the thicknesses of the cover glass 50 are 2.5 mm, 3 mm, 3 mm, 3.2 mm, and 3.2 mm, respectively. In Examples 6-9, the thicknesses of the first glass 501 are 3.2 mm, 2.6 mm, 2.8 mm, and 3 mm, respectively; and the thicknesses of the second glass 502 are 3.2 mm, 2.6 mm, 2.8 mm, and 3 mm, respectively.

[0095] The results show that, using the design of this application, the stress concentration factor of the mounting hole of the cover glass 50 can be reduced from 30.-3.5 to 1.6-2.0. The static load can be increased to 120%-138% of the reference value (e.g., 500N). The design concept of this application can effectively reduce the stress concentration factor of the mounting hole and improve the static load.

[0096] Furthermore, finite element analysis or strain gauge testing of the contact compressive stress at the hole edge revealed that the contact stress in the first and second transition zones of this application is reduced by 38-47% compared to the prior art. Specifically, the contact stress in the comparative example is 150 MPa, while the contact stress in each embodiment of this application is 80-90 MPa. In addition, three-point bending tests or dynamic impact tests showed that the crack propagation resistance of the cover glass 50 of this application can be improved by 28-37%.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A photovoltaic module, characterized in that, include: Battery string; The first adhesive film and the second adhesive film are located on both sides of the battery string, respectively; A front-side encapsulation structure, wherein the front-side encapsulation structure is disposed on the side of the first adhesive film opposite to the battery string; and A cover glass is disposed on the side of the second adhesive film opposite to the battery string. The cover glass includes a first surface and a second surface disposed opposite to each other in the thickness direction. A through hole is provided in the cover glass. The through hole includes a first transition area, a central circular hole area and a second transition area connected in sequence. The diameter of the hole in the first transition area opens onto the first surface after being enlarged from the central circular hole area. The diameter of the hole in the second transition area opens onto the second surface after being enlarged from the central circular hole area.

2. The photovoltaic module according to claim 1, characterized in that, In the radial direction of the central circular hole area, the width of the first transition zone is 1.75mm-3mm.

3. The photovoltaic module according to claim 1, characterized in that, In the radial direction of the central circular hole area, the width of the second transition zone is 1.25mm-2mm.

4. The photovoltaic module according to claim 1, characterized in that, The first transition zone is a frustum-shaped region with an inclination angle of 15°-25°.

5. The photovoltaic module according to claim 1, characterized in that, The second transition zone is a frustum-shaped region with an inclination angle of 15°-25°.

6. The photovoltaic module according to claim 1, characterized in that, The difference between the tilt angle of the first transition zone and the tilt angle of the second transition zone is within 3°.

7. The photovoltaic module according to claim 1, characterized in that, In the thickness direction, the length of the second transition region is less than the length of the first transition region.

8. The photovoltaic module according to claim 1, characterized in that, The thickness of the cover glass is 2.5mm-3.2mm.

9. The photovoltaic module according to claim 1, characterized in that, The cover glass comprises a first glass, an adhesive layer, and a second glass layer stacked sequentially, with the central circular hole area penetrating the adhesive layer and passing through the first and second glass layers.

10. The photovoltaic module according to claim 9, characterized in that, The first glass and the second glass have the same thickness, and the first transition zone and the second transition zone are centrally symmetrical about the thickness direction of the cover glass.

11. The photovoltaic module according to claim 9, characterized in that, The thickness of both the first glass and the second glass is 2.5mm-3.2mm.

12. The photovoltaic module according to claim 1 or 11, characterized in that, The aperture of the opening in the first transition zone on the first surface is 10-12 mm, and the length in the thickness direction is 0.8 mm-1.2 mm.

13. The photovoltaic module according to claim 1 or 11, characterized in that, The diameter of the central circular hole area is 6.5mm-7mm, with a tolerance of ±0.05mm, and the length in the thickness direction is 1.0mm-1.5mm.

14. The photovoltaic module according to claim 1 or 11, characterized in that, The second transition zone has an opening with a diameter of 9mm-11mm on the second surface and a length of 0.5mm-1mm in the thickness direction.

15. The photovoltaic module according to claim 1, characterized in that, The inner wall surface of the through hole is provided with a chemical tempering layer, which penetrates into the cover glass.

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