A photovoltaic module based on low-temperature welding and low-temperature lamination technology

Abstract

The present invention belongs to the technical field of photovoltaic module structures, and particularly relates to a photovoltaic module based on low-temperature welding and low-temperature lamination technologies. By arranging main grid units, solder blocks, welding rods, fine grid lines, photocurable adhesive films on the battery cells and the front glass, the welding rods can be welded at relatively low temperatures, and the photocurable adhesive films eliminate the need for high-temperature lamination conditions, ultimately ensuring that the performance of the heterojunction is not greatly affected.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic module structures, and particularly relates to a photovoltaic module based on low-temperature welding and low-temperature lamination technologies. Background Art

[0002] The structure of a photovoltaic module, from top to bottom, is as follows: front glass, upper adhesive film, battery string, lower adhesive film, and backsheet. Among them, the most crucial core part that can generate solar power is the battery string, and its structure can be further divided into solar cells, main grid lines, fine grid lines, and solder tapes. On the other hand, the main grid lines and fine grid lines are generally screen-printed, and between the main grid lines and the solder tapes, molten solder needs to be used for connection.

[0003] In addition, in the field of solar cells of photovoltaic modules, the HJT technology is considered by most people to be the third-generation solar cell technology after the BSF and PERC technologies. The corresponding solar cell is the HJT solar cell, or also called the heterojunction solar cell.

[0004] The general principle of the HJT technology is: depositing intrinsic and doped amorphous silicon thin films, as well as transparent conductive oxide film layers, on both sides of an N-type silicon wafer to absorb the generated electricity. Since amorphous silicon has the characteristics of strong light absorption and excellent passivation performance, a higher conversion efficiency of solar cells can be achieved.

[0005] However, the manufacturing process of the heterojunction is a low-temperature process, and in the production process of photovoltaic modules, the two inevitable high-temperature links are the high-temperature welding of the solder tape and the high-temperature lamination forming of the adhesive film. In the prior art, the operating temperature of the former is generally 200 - 400 °C, and the forming temperature of the latter generally also approaches 200 °C. Therefore, this is very dangerous for the heterojunction. In such a high-temperature environment, the heterojunction is relatively prone to edge warping and hidden cracking.

[0006] Regarding the above two "high-temperature problems", the existing mitigation methods mainly include: 1. Using low-temperature curable silver paste (i.e., the main grid material); 2. Using light-curable glue to replace ordinary EVA hot-melt glue, which can completely eliminate the high-temperature lamination operation. However, the mitigation effect of the former is general, the welding temperature cannot be significantly reduced, and the welding duration cannot be significantly shortened.

[0007] The Chinese utility model patent with the patent announcement number CN208256692U and the announcement date of December 18, 2018, discloses a photovoltaic module of a multi-main grid solar cell, which includes coated glass, upper transparent hot-melt adhesive film, solar cell, bottom hot-melt adhesive film, backsheet, and aluminum frame. The coated glass, upper transparent hot-melt adhesive film, solar cell, bottom hot-melt adhesive film, and backsheet are sequentially combined together from top to bottom to form a photovoltaic module body. The aluminum frame is sleeved on the outer surface of the photovoltaic module body. The solar cell is respectively provided with a bus bar and a welding wire, and the backsheet is provided with a junction box.

[0008] In the photovoltaic module of this utility model patent, the shape of the "solder ribbon 4" is improved to a circular shape, so the light utilization rate can be appropriately increased. However, the overall structure of its main grid line and solder ribbon includes a solder ribbon strip, a solder bar, and a main grid line from top to bottom, and its length dimension, height dimension, and width dimension are all relatively large. Therefore, the welding workload is relatively large, and a large amount of welding heat will be directly transferred to the heterojunction of the HJT cell, which is very dangerous.

[0009] Therefore, in summary, it is urgent to improve the overall structure and shape of the main grid line and solder ribbon to reduce the heat generated during welding and further protect the heterojunction performance of the HJT cell. Summary of the Invention

[0010] The present invention provides a photovoltaic module based on low-temperature welding and low-temperature lamination technologies. By arranging a main grid unit, a solder block, a welding rod, a fine grid line, a light-curing adhesive film, and a front glass on the cell, the welding rod can be welded at a relatively low temperature, and the high-temperature lamination condition for the light-curing adhesive film is omitted, ultimately ensuring that the performance of the heterojunction is not greatly affected.

[0011] The technical solution adopted by the present invention to solve the above problems is: a photovoltaic module based on low-temperature welding and low-temperature lamination technologies, the structure includes a cell, a light-curing adhesive film, a front glass, and a fine grid line, and further includes a main grid unit with a groove on the upper surface, a solder block arranged in the main grid unit, and a welding rod inserted on the main grid unit and welded to the solder block.

[0012] A further preferred technical solution lies in that: the main grid unit includes a main grid line, a lengthwise through groove arranged on the upper surface of the main grid line, and a vertical groove arranged on the lengthwise through groove and used for arranging the solder block.

[0013] A further preferred technical solution lies in that: the distance between two adjacent vertical grooves is 5-11 mm.

[0014] A further preferred technical solution lies in that: the cross-sectional shape of the main grid line is a minor arc bow, the width of the main grid line is 1.05-1.10 mm, and the maximum height is 0.20-0.25 mm.

[0015] A further preferred technical solution lies in that: the lengthwise through groove is arranged on the highest point axis of the main grid line, the maximum grooving depth of the lengthwise through groove is 30-45% of the maximum thickness of the main grid line, and the grooving depth of the vertical groove is 2-3% of the maximum thickness of the main grid line.

[0016] A further preferred technical solution lies in that: the cross-sectional shape of the welding rod is an ellipse.

[0017] A further preferred technical solution is that the major axis of the elliptical cross-section of the welding rod is perpendicular to the battery cell, and the size of the major axis of the elliptical cross-section is 3.0 - 3.6 times that of the minor axis.

[0018] A further preferred technical solution is that the sum of the vertical heights of the main grid unit and the welding rod is 85 - 95% of the thickness of the photocurable adhesive film.

[0019] A further preferred technical solution is that the material of the main grid unit is low-temperature silver paste.

[0020] A further preferred technical solution is that the material of the photocurable adhesive film is ultraviolet curable adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the present invention.

[0022] Figure 2 It is a schematic diagram of the light reflection usage mode of the main grid unit and the welding rod in the present invention.

[0023] Figure 3 It is a schematic structural diagram of the main grid unit in the present invention.

[0024] Figure 4 It is a schematic diagram of the distribution mode of the solder blocks in the present invention.

[0025] Figure 5 It is a schematic diagram of a positional structure of a common main grid, a solder bar, and a common welding rod in the prior art.

[0026] In the drawings, the meanings represented by the respective reference numerals are as follows.

[0027] Battery cell a, photocurable adhesive film b, front glass c, and fine grid lines d.

[0028] Common main grid A, solder bar B, common welding rod C.

[0029] Main grid unit 1, solder block 2, welding rod 3, main grid line 101, length-direction through slot 102, vertical slot 103. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following is only a preferred embodiment of the present invention, and does not limit the scope of the present invention.

[0031] As shown in the attached Figures 1-5As shown in the figure, a photovoltaic module based on low-temperature welding and low-temperature lamination technology has a structure including a cell a, a light-curing adhesive film b, a front glass c, and fine grid lines d. It also includes a main grid unit 1 with a groove on its upper surface, a solder block 2 arranged in the main grid unit 1, and a welding rod 3 inserted on the main grid unit 1 and welded to the solder block 2.

[0032] The prior art is as shown in the appendix Figure 5 As shown, a common welding rod C with a circular cross-section, although having a certain light reflection effect, is fixed to a common main grid A only through the welding action of a solder strip B. Therefore, the width and thickness dimensions of the latter have to be made larger and continuous to ensure sufficient fixing effect.

[0033] Moreover, the original light reflection effect of the common main grid A is also greatly reduced, and it is largely covered by the solder strip B.

[0034] Therefore, in this embodiment, first, the common EVA hot-melt adhesive is replaced by a light-curing adhesive. The former only needs to be cured at room temperature, and considering the regular curing shape, only a shaping pressure, such as dozens or hundreds of Pa, is required. Compared with the lamination strength of the hot-melt adhesive in the range of 0.3 - 0.5 MPa, the damage to the structure of the cell and heterojunction is minimal. This is the meaning of the above-mentioned "low-temperature lamination".

[0035] Secondly, the cross-sectional shape of the common welding rod C is made circular instead of rectangular or triangular. One of the purposes is to avoid excessive stress concentration at the thin upper end of the welding rod during the lamination of the EVA hot-melt adhesive and avoid increasing the risk of cracking inside the adhesive film during the curing process.

[0036] Finally, the welding rod 3 in the light-curing adhesive film b can be "thin and long" without pressing down the cell a, that is, the characteristics of its cross-sectional shape ensure that although the upper part of the welding rod 3 is ""

[0037] In addition, the main grid unit 1 provides a connection structure basis for plugging and engaging the welding rod 3, enabling the subsequent required welding strength to be reduced. This is the reason for the improvement of the soldering method from "continuous" to "point contact".

[0038] The main grid unit 1 includes a main grid line 101, a lengthwise through groove 102 arranged on the upper surface of the main grid line 101, and a vertical groove 103 arranged on the lengthwise through groove 102 and used for arranging the solder block 2.

[0039] In this embodiment, the solder block 2 is first placed at the vertical groove 103, then the welding rod 3 is pressed downward and snapped into the lengthwise through groove 102, and finally hot melt welding is performed. However, at this time, the amount of the solder block 2 is relatively small. Therefore, the temperature required for welding is lower and the time required is shorter, which can protect the heterojunction and the entire cell to the greatest extent. This is the meaning of "low-temperature welding".

[0040] The distance between two adjacent vertical grooves 103 is 5 - 11 mm.

[0041] In the prior art, the interval between the main grid lines is generally 20 - 30 mm. The above density of the vertical grooves 103 enables the welding rod 3 to minimize the usage amount of the solder block 2 on the premise of stable installation.

[0042] The cross-sectional shape of the main grid line 101 is a minor arc bow, and the width of the main grid line 101 is 1.05 - 1.10 mm and the maximum height is 0.20 - 0.25 mm.

[0043] In this embodiment, the solder block 2 is arranged in the lengthwise through groove 102. Therefore, the solder will not cover the arc-shaped upper surface of the main grid line 101. So the main grid line 101 can also reflect light, further improving the power generation efficiency of the cell a, which cannot be achieved by the way of "a large piece" of solder covering the main grid in the prior art.

[0044] The lengthwise through groove 102 is arranged on the axis of the highest point of the main grid line 101. The maximum grooving depth of the lengthwise through groove 102 is 30 - 45% of the maximum thickness of the main grid line 101, and the grooving depth of the vertical groove 103 is 2 - 3% of the maximum thickness of the main grid line 101.

[0045] In this embodiment, the lengthwise through groove 102 together with the welding rod 3 are both located at the highest point on the upper surface of the main grid line 101. The grooving depths of the lengthwise through groove 102 and the vertical groove 103 are appropriately large on the premise of not affecting the self-structural strength and structural integrity of the main grid line 101, so that the former can fully snap and fix the welding rod 3 and the latter can fully accommodate a sufficient amount of solder.

[0046] The cross-sectional shape of the welding rod 3 is an ellipse.

[0047] In this embodiment, if the welding rod 3 is used in the EVA hot melt adhesive, when the adhesive film is hot-pressed at high temperature, the "thin edge" at the upper end of the welding rod is likely to form an overly concentrated stress area in the adhesive film, greatly increasing the risk of internal fragmentation of the adhesive film.

[0048] Therefore, the elliptical shape of the welding rod 3 must be used in combination with the photo-curing adhesive film b.

[0049] Finally, the two sides of the elliptical electrode can reflect more light compared to the circular style.

[0050] The major axis of the elliptical cross-section of the electrode 3 is perpendicular to the cell a, and the size of the major axis of the elliptical cross-section is 3.0 - 3.6 times that of the minor axis.

[0051] In this embodiment, the elliptical cross-section of the electrode 3 should not be too "sharp", so its major axis is vertical and the minor axis is horizontal, and the aspect ratio should not be too large.

[0052] The sum of the vertical heights of the main grid unit 1 and the electrode 3 is 85 - 95% of the thickness of the photocurable adhesive film b.

[0053] In the prior art, also because the EVA hot melt adhesive requires high-temperature lamination, if the height of the upper vertex of the electrode is too high, it will crush the EVA hot melt adhesive film. Therefore, the relative protrusion height of the ordinary electrode C and the cell is very limited, and its light reflection effect is greatly restricted.

[0054] For example, for the above-mentioned ratio of height to thickness, in the prior art, with EVA hot melt adhesive and a circular electrode, it can only reach about 60%.

[0055] The material of the main grid unit 1 is low-temperature silver paste.

[0056] In this embodiment, the raw material composition of the low-temperature silver paste mainly includes: conductive silver powder, silver indium alloy, composite epoxy resin, crack growth inhibitor, titanate coupling agent, curing agent, and conventional solvents, etc. It ensures a high contact tensile force between itself and the cell, has a low film resistance after curing, and has high weldability.

[0057] The material of the photocurable adhesive film b is ultraviolet curable adhesive.

[0058] In this embodiment, when selecting the type of ultraviolet curable adhesive, its light transmittance, denseness, and stability under complex environmental conditions are mainly considered.

[0059] Finally, the photovoltaic module in this embodiment has at least the following advantages.

[0060] First, using ultraviolet curable adhesive to replace the ordinary EVA hot melt adhesive eliminates the high-temperature lamination operation during film formation, greatly reducing the harm of high-temperature factors to the heterojunction of the cell. Of course, the ultraviolet curable adhesive also has its own defects in other aspects.

[0061] Second, precisely because the photocuring adhesive film b does not require high-pressure conditions during molding, the cross-sectional shape of the welding rod 3 is improved to an ellipse with the long axis vertical. Compared with the structural style of a circular welding rod, it has a greater light reflection effect, and the risks of stress concentration and extrusion breakage of the photocuring adhesive film b are also within an acceptable range.

[0062] Third, the welding rod 3 has an initial clamping and fixing effect on the main grid unit 1. Therefore, the subsequent welding area can be greatly reduced, ultimately reducing the welding amount and the heat generated during welding, thereby protecting the heterojunction of the battery chip.

[0063] Fourth, after multiple tests and adjustments, a set of optimal numerical parameters for the dimensions and proportions of the overall structure of the main grid unit 1 plus the welding rod 3 are obtained, ensuring that the basic functions of the main grid and the welding rod are optimized, namely relatively low resistivity, relatively high light reflectivity, and sufficient tensile strength of the welding rod.

[0064] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various modifications can be made without departing from the purpose of the present invention. These are all non-creative modifications and are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies, the structure comprising a cell (a), a photocurable adhesive film (b), a front glass (c), and fine grid lines (d), characterized in that: It further includes a main grid unit (1) with a grooved upper surface, a solder block (2) disposed within the main grid unit (1), and a welding rod (3) inserted and disposed on the main grid unit (1) and welded to the solder block (2). The main grid unit (1) includes a main grid line (101), a lengthwise through groove (102) provided on the upper surface of the main grid line (101), and a vertical groove (103) provided on the lengthwise through groove (102) and for setting the solder block (2). The cross-sectional shape of the main grid line (101) is a minor arc bow, the width of the main grid line (101) is 1.05 - 1.10 mm, and the maximum height is 0.20 - 0.25 mm. The cross-sectional shape of the welding rod (3) is oval. The major axis of the oval cross-section of the welding rod (3) is perpendicular to the cell (a), and the major axis dimension of the oval cross-section is 3.0 - 3.6 times that of the minor axis.

2. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies according to claim 1, characterized in that: The distance between two adjacent vertical grooves (103) is 5 - 11 mm.

3. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies according to claim 1, characterized in that: The lengthwise through groove (102) is provided on the highest point axis of the main grid line (101), the maximum grooving depth of the lengthwise through groove (102) is 30 - 45% of the maximum thickness of the main grid line (101), and the grooving depth of the vertical groove (103) is 2 - 3% of the maximum thickness of the main grid line (101).

4. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies according to claim 1, characterized in that: The sum of the vertical heights of the main grid unit (1) and the welding rod (3) is 85 - 95% of the thickness of the photocurable adhesive film (b).

5. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies according to claim 1, characterized in that: The material of the main grid unit (1) is low-temperature silver paste.

6. A photovoltaic module based on low-temperature welding and low-temperature lamination technologies according to claim 1, characterized in that: The material of the photocurable adhesive film (b) is ultraviolet photocurable adhesive.

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