Photovoltaic module and preparation method thereof

Abstract

The invention relates to the technical field of photovoltaics, and aims to solve the problems of battery piece warping, welding spot failure, appearance scratching, difficulty in high-density packaging and the like in existing BC battery packaging. Therefore, the photovoltaic module is provided, the photovoltaic module is formed by laminating a front cover plate, a front packaging adhesive film, a plurality of battery pieces, a back packaging adhesive film and a back cover plate which are sequentially stacked, the adjacent battery pieces are in lap joint with each other, the front surfaces of the battery pieces are coated with insulating protective films, electric isolation layers are formed at the lap joint parts of the battery pieces, and the back surfaces of the adjacent battery pieces are connected through welding strips. According to the invention, the isolation and appearance protection of the overlapping part are realized through the front insulating protective film, and the effects of reducing the hidden crack risk and improving the power and appearance quality of the module are realized by combining the imbricated overlapping design.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, and specifically provides a photovoltaic module and a preparation method thereof. BACKGROUND

[0002] In the field of photovoltaic, the mainstream development of the industry has shifted from PERC cells to TOPCon cells or HJT cells, and each leading enterprise is actively laying out HJT cells, BC cells and perovskite cells in the industry trend of cost reduction and efficiency improvement. Among them, the technical scheme of BC cell is mainly divided into high-temperature welding and low-temperature welding. Low-temperature welding is further divided into film coating scheme, dispensing scheme and low-temperature welding scheme, but no matter what scheme, the following problems will inevitably occur in the manufacturing or use process of the cell piece:

[0003] 1. Warping problem: mainly because the metal grid lines of the BC cell are mainly concentrated on the back surface, during the high-temperature welding process, the stress imbalance of the front and back surfaces causes the shrinkage rate of the back surface to be large, thereby causing the warping problem.

[0004] 2. Welding point failure problem: low-temperature welding can easily lead to unreliable connection, and welding point failure problem is prone to occur in reliability aging test.

[0005] 3. Cell appearance problem: the cell has no grid lines on the front surface, and currently the cell piece needs to be placed with isolation paper in each cell piece, but in the process, it is difficult to avoid scratches, resulting in abnormal appearance of the cell.

[0006] 4. Module appearance problem: after the cells are connected in series, the welding ribbon will be exposed in the cell spacing, and the front appearance is poor. The industry currently uses a film plug method, but the process is complex.

[0007] 5. Module utilization problem: due to the absence of grid lines on the front surface, the positive and negative electrodes are concentrated on the back surface, and the inter-string stress is relatively low compared to the TOPCon interconnection of the front and back surfaces. However, due to the very brittle nature of the silicon wafer, it is difficult to control the inter-cell spacing to 0 during the process of shortening the inter-cell spacing, so the high-density packaging of the BC cell is difficult at present.

[0008] Therefore, there is a need in the art for a photovoltaic module scheme that can at least solve one of the above problems. SUMMARY

[0009] The present application aims to solve the above technical problems, that is, at least one of the problems of poor appearance of the existing cell and photovoltaic module, easy failure of the welding point, and easy warping of the cell piece.

[0010] To solve the above problems, the application provides a photovoltaic module, which is formed by laminating a front cover, a front encapsulation adhesive film, a plurality of cell pieces, a back encapsulation adhesive film and a back cover in sequence, wherein adjacent cell pieces are overlapped with each other, the front surface of the cell pieces is provided with an insulating protective film, the insulating protective film forms an electrical isolation layer at the overlapping part, and the back surfaces of adjacent cell pieces are connected by a solder strip.

[0011] In some possible implementation manners of the photovoltaic module, the insulating protective film is applied to the entire area of the front surface of the cell pieces.

[0012] In some possible implementation manners of the photovoltaic module, the insulating protective film is made of one or more of EVA, POE, EPE, PVB or TPO.

[0013] In some possible implementation manners of the photovoltaic module, the thickness of the insulating protective film is 30 μm to 120 μm.

[0014] In some possible implementation manners of the photovoltaic module, the insulating protective film is a non-pre-crosslinked film.

[0015] In some possible implementation manners of the photovoltaic module, the width of the overlapping part is 0.2 mm to 1.0 mm.

[0016] In a second aspect, the application further provides a preparation method of a photovoltaic module, which comprises the following steps:

[0017] applying an insulating protective film to the front surface of the cell pieces;

[0018] applying an insulating adhesive to the back surface of the cell pieces to isolate the positive grid lines and the negative grid lines;

[0019] applying a solder strip;

[0020] overlapping a plurality of cell pieces in a shingle manner, wherein the overlapping parts of at least adjacent cell pieces are separated by the insulating protective film;

[0021] welding the solder strip and the metal contact points of the cell pieces by a spot tin soldering process;

[0022] applying an encapsulation adhesive film and a cover;

[0023] laminating to form a photovoltaic module.

[0024] In some possible implementation manners of the preparation method of the photovoltaic module, the step of applying an insulating protective film to the front surface of the cell pieces comprises the following steps:

[0025] applying an insulating protective film to the entire area of the front surface of the cell pieces by a hot lamination process.

[0026] slicing the whole cell sheet to form cell sheet for constructing the photovoltaic module,

[0027] The heating temperature of the hot film coating process is 80-120℃.

[0028] In some possible embodiments of the method for preparing the photovoltaic module, the step of "welding the solder strip and the metal contact point of the cell sheet by the spot tin welding process" comprises:

[0029] The tin wire is heated by the heating unit of the spot tin mechanism to form a tin ball, which is formed on the heating unit and at least on one side of the solder strip;

[0030] When the tin feeding amount of the tin feeding unit of the spot tin mechanism reaches the preset tin feeding amount, the heating head of the heating unit is kept in the heating state while descending to a preset height, so that the tin ball can fill the gap between the solder strip and the metal contact point of the cell sheet.

[0031] In some possible embodiments of the method for preparing the photovoltaic module, the heating temperature of the heating unit of the spot tin mechanism is 200-300℃.

[0032] The photovoltaic module provided by the application has the following advantages:

[0033] The application effectively avoids the short circuit risk caused by the direct contact between adjacent cell sheets by laying the insulating protective film on the front surface of the cell sheet and forming an electrical isolation layer at the overlapping part of adjacent cell sheets with the help of the insulating protective film on the front surface. At the same time, the insulating protective film covers the front surface, which can prevent the surface of the cell sheet from being eroded by acidic substances in the encapsulation film, thereby improving the long-term weather resistance of the module. In addition, the insulating protective film is arranged on the front surface, which can improve the arrangement density of the cell sheet, reduce the internal gap of the module, thereby improving the output power, and reduce the scratching problem during the process of arranging the cell sheet in a shingle manner, thereby improving the appearance of the cell sheet and the appearance of the module.

[0034] Further, the insulating protective film fully covers the front surface of the cell sheet, which more comprehensively isolates the direct contact between the encapsulation film and the cell sheet than the partial coverage. In addition, the production process can be simplified, and the alignment accuracy problem that needs to be considered in the partial coverage scheme can be avoided. In addition, the full coverage design can also uniformly disperse the stress during the laminating process, reduce the hot spot effect, and improve the power generation stability.

[0035] Further, EVA, POE, PVB or TPO and the like are selected as the insulating protective film covering the cell sheet. These materials have good fluidity during the laminating process, can effectively fill the gap between the cell sheets, and can ensure the integrity of the insulating layer while protecting the appearance of the cell sheet.

[0036] Further, the thickness of the protective film is controlled in the range of 30-120 μm, which is an optimized choice between insulation performance and optical efficiency, and the range can avoid the cost increase caused by over-thickness and the reliability risk caused by over-thin.

[0037] Further, the use of non-pre-crosslinked film can significantly improve the flowability in the lamination process. The non-pre-crosslinked film can also form flowability matching with the back encapsulation adhesive film (such as pre-crosslinked POE), reduce the stress difference in the lamination, and improve the component yield.

[0038] Further, the lap width is controlled in the range of 0.2-1.0 mm, which can balance the electrical connection reliability and optical loss. In addition, the precise width control can also reduce the edge recombination effect and improve the electrical performance of the battery sheet.

[0039] The control method provided by the application has the following beneficial effects:

[0040] The precise control of the tin ball filling gap through the spot tin soldering process can significantly improve the solder joint quality, ensure that the tin ball completely fills the gap between the solder strip and the metal contact point of the battery sheet, and avoid the problems of false welding or short circuit. In addition, the imbricated lap joint combined with the spot tin soldering can reduce the thermal stress by more than 80% compared with the traditional soldering, thereby greatly reducing the hidden cracking rate of the battery sheet.

[0041] Further, the hot lamination process is carried out at 80-120 ℃, which can make the insulation protective film (such as EVA) melt and adhere to the battery sheet, and also avoid damage to the battery sheet caused by high temperature. In this temperature range, the insulation protective film can effectively wet the surface of the battery sheet and form a firm bond. In addition, after full coverage hot lamination, the integrity of the insulation layer of each battery sheet can be ensured, and the edge leakage problem that may occur in the traditional single piece lamination can be avoided.

[0042] Further, compared with the traditional soldering process, the spot tin soldering has a smaller heat-affected zone, which can avoid thermal damage to other areas of the battery sheet, reduce the amount of solder (more than 30% saved compared with the traditional soldering), and reduce the cost. The precise tin feeding amount control (accuracy ±0.02 g) can also avoid the problems of short circuit caused by excessive tin amount and poor contact caused by insufficient tin amount.

[0043] Further, the heating unit temperature is controlled in the range of 200-300 ℃, which can ensure that the tin wire is quickly melted and wetted on the metal contact point, and also avoid overheating damage to the battery sheet. BRIEF DESCRIPTION OF DRAWINGS

[0044] The preferred embodiments of the application will be described below with reference to the accompanying drawings, in which:

[0045] Figure 1 The BC battery sheet back grid line structure schematic diagram provided for the embodiments of the application is shown in the figure.

[0046] Figure 2 As Figure 1 Structure schematic diagram after adding insulating glue and solder strip;

[0047] Figure 3 Battery film lamination schematic diagram provided by the embodiment of the application;

[0048] Figure 4 Cross-sectional schematic diagram of a photovoltaic module provided by the embodiment of the application;

[0049] Figure 5 Principle schematic diagram of spot tin soldering provided by the embodiment of the application.

[0050] List of reference signs:

[0051] 1, battery piece; 2, positive main grid; 3, positive auxiliary grid; 4, negative main grid; 5, negative auxiliary grid; 6, insulating glue; 7, solder strip; 8, insulating protective film; 9, front encapsulation glue film; 10, front cover plate; 11, back encapsulation glue film; 12, back cover plate; 13, heating head; 14, tin feeding unit; 15, tin wire; 16, tin ball. DETAILED DESCRIPTION

[0052] The preferred embodiments of the application are described below with reference to the accompanying drawings. Those skilled in the art will understand that these embodiments are only used to explain the technical principles of the application, and are not used to limit the protection scope of the application. Those skilled in the art can make adjustments to them as needed in order to adapt to specific application occasions.

[0053] In order to better illustrate the application, numerous specific details are given in the specific embodiments below. Those skilled in the art will understand that the application can also be implemented without certain specific details.

[0054] In the description of the application, the terms "upper", "lower", "inner", "outer", "front", "back", and the like, which indicate the direction or positional relationship, are based on the illustrated direction or positional relationship, which is only for the convenience of description, and is not intended to indicate or imply that the device to be protected must have a specific orientation, be constructed and operated in a specific orientation, therefore the orientation in the following embodiments cannot be understood as a limitation on the application. In addition, the ordinal numbers "first", "second", etc. are only for the convenience of description, and are not used to indicate or imply relative importance.

[0055] In addition, it needs to be explained that in the description of the present application, unless otherwise specified and limited, the terms "mounting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0056] The photovoltaic module and the preparation method of the photovoltaic module provided by the present application will be described below in combination with the drawings.

[0057] Before the photovoltaic module and the preparation method of the photovoltaic module are described, the cell used to form the photovoltaic module is described first.

[0058] Figure 1 The structure schematic diagram of the back surface grid line of the BC cell is shown in FIG. 1, which mainly includes a positive main grid 2, a positive auxiliary grid 3, a negative main grid 4 and a negative auxiliary grid 5. Figure 1 The positive main grid 2 and the negative main grid 4 serve as the "main road" of current collection and transmission, and bear the functions of current collection and conduction. Specifically, the core role of the positive main grid 2 is to transmit the current collected by the positive auxiliary grid 3 to the external solder strip 7 after the current is concentrated and collected; the negative main grid 4 corresponds to the positive main grid 2, and is responsible for collecting the current collected by the negative auxiliary grid 5 and transmitting the current to the solder strip 7, and the two together form the key channel for the output of the current from the back surface of the cell.

[0059] In this embodiment, the positive auxiliary grid 3 and the negative auxiliary grid 5 in the BC cell 1 are arranged in an interdigital manner and directly contact the photogenerated carriers (including holes and electrons) generated inside the cell due to illumination. Among them, the positive auxiliary grid 3 collects holes and the negative auxiliary grid 5 collects electrons. The interdigital staggered arrangement enables the two auxiliary grids to maximize the coverage of the back surface area of the cell, shortens the transmission distance of the carriers, and reduces the loss, so as to ensure that more photogenerated carriers are effectively captured. After the photogenerated carriers are collected by the corresponding auxiliary grid, they are transmitted to the main grid line along the auxiliary grid line - the positive carrier flows to the positive main grid 2, and the negative carrier flows to the negative main grid 4, and finally the current is exported outward through the connection of the main grid and the solder strip 7.

[0060] It needs to be explained that although the BC cell 1 with main grid is taken as an example for description, this is not restrictive, and the number of main grids is not limited in the present application. In addition, the present application is also applicable to the BC cell 1 without main grid structure, in which the insulating glue 6 directly isolates the adjacent positive and negative auxiliary grids, and the solder strip 7 is directly connected with the auxiliary grid.

[0061] Figure 2 The structure schematic diagram after adding the insulating glue 6 and the solder strip 7 is shown in FIG. 2. Figure 1 It can be seen from FIG. 2 that the insulating glue 6 is arranged between the positive auxiliary grid 3 and the negative auxiliary grid 5, and the solder strip 7 is arranged on the positive auxiliary grid 3 and the negative auxiliary grid 5.Figure 2 As shown, the insulating glue 6 is mainly arranged near the end of the sub-gate opposite to the main gate, and the main role is to prevent the contact with the gate line opposite to the polarity to cause local short circuit during the process of laying the solder strip 7. The main body of the insulating glue 6 is an epoxy resin system, which is formed on the back of the BC battery sheet 1 by printing or inkjet printing process. The thickness needs to be determined according to the height of the gate line, and it is usually appropriate to exceed the height of the gate line by about 30 μm to ensure that the insulation requirement is met; the width and length of the insulating glue 6 have no fixed limit, and it can be made into an integral strip or processed into a split structure as shown in the figure. The main function of the solder strip 7 is to collect the current generated by the PAD point and the main gate, and the preferred is a pure copper wire solder strip 7 (since there is no need to use the tin layer on the conductor in the solder strip 7 for welding, so the pure copper solder strip 7 is used), and the shape has no specific limit, which can be a flat solder strip 7 or a triangular solder strip 7, etc., and the diameter of the solder strip 7 ranges from 0.16 mm to 0.3 mm.

[0062] The photovoltaic module formed by the above battery sheet 1 and the preparation method of the photovoltaic module will be described in detail below with reference to the accompanying drawings.

[0063] As shown in Figure 3 and Figure 4 , the present application provides a photovoltaic module. The photovoltaic module is laminated by a front cover plate 10, a front encapsulation glue film 9, a plurality of battery sheets 1, a back encapsulation glue film 11, and a back cover plate 12 in sequence, wherein adjacent battery sheets 1 in the plurality of battery sheets 1 are overlapped with each other, and the overlapping manner is referred to Figure 3 As shown, the insulating protection film 8 is arranged on the front of the battery sheet 1, and the insulating protection film 8 forms an electrical isolation layer at the overlapping part, and the back of the adjacent battery sheet 1 is connected by the solder strip 7.

[0064] As shown in Figure 3 , adjacent battery sheets 1 in the plurality of battery sheets 1 are overlapped with each other to form an overlapping part, and the insulating protection film 8 is arranged on the front of the battery sheet 1. The size of the battery sheet 1 is 210x105 mm, and the size of the coated insulating protection film 8 is 210x105 mm. The insulating protection film 8 fully covers the front of the battery sheet 1, and the purpose is that the battery sheet 1 can have a film layer to pad at the overlapping part during the module process without distinguishing the direction. In this embodiment, the insulating protection film 8 is arranged on the whole area of the front of the battery sheet 1. It can be understood that the insulating protection film 8 can be arranged only at the overlapping part or extended by a certain size from the overlapping part. The material of the insulating protection film 8 can be one or more of EVA / POE / EPE / PVB / TPO, and the thickness of the insulating protection film 8 can be 30 μm to 120 μm, so as to reduce the thickness of the front encapsulation glue film 9. The width of the overlapping part is 0.2 mm to 1.0 mm.

[0065] As shown in Figure 4As shown in the figure, for example, the left edge of the right battery piece 1 is overlapped on the right edge of the left battery piece 1, and the two are isolated by the insulating protective film 8 on the front of the left battery piece 1 at the overlapping position, so as to realize the inter-piece negative spacing connection. In addition, the back of each battery piece 1 is connected by the solder strip 7.

[0066] The preparation method of the photovoltaic module in the above example will be described in detail below.

[0067] The preparation method of the photovoltaic module provided by the application comprises the following steps:

[0068] S1, laying an insulating protective film 8 on the front of the battery piece 1.

[0069] Specifically, the front of the battery piece 1 is a light receiving surface, which needs to realize multiple functions through the insulating protective film 8: one is physical protection, avoiding the front of the battery piece 1 being mechanically scratched in subsequent processes, affecting the appearance; the other is electrical insulation, preventing the front of the battery piece 1 from forming a short circuit loop with other metal parts inside the module. The insulating protective film 8 is preferably PET (polyethylene terephthalate) or modified EVA (ethylene-vinyl acetate copolymer) material, wherein the PET film needs to meet the requirements of long-term temperature resistance ≥ 120℃, tensile strength ≥ 150MPa, and the modified EVA film needs to have initial adhesion (peeling strength ≥ 0.3N / cm at 23℃) to assist positioning. The thickness of the insulating protective film 8 is controlled between 30μm and 120μm, preferably between 50-100μm. The insulating protective film 8 described in the application is a non-pre-crosslinked film, which will undergo a melt crosslinking reaction with the encapsulation adhesive film in the lamination process to form a more firm overall encapsulation structure. The insulating protective film 8 needs to be cleaned before laying on the front of the battery piece 1 to remove the surface oxide layer and organic contaminants.

[0070] Further, the insulating protective film 8 can be laid on the entire area of the front of the entire battery piece 1 by a hot lamination process first, and then the entire battery piece 1 is cut to form the battery piece 1 used to construct the photovoltaic module, wherein the heating temperature of the hot lamination process is 80℃-120℃.

[0071] Specifically, the hot lamination process needs to use a precision roller lamination machine. When laminating, the cut insulating protective film 8 (the size is consistent with the battery piece 1) is aligned with the front of the battery piece 1, and is conveyed to the heating roller group (the temperature is set to 80-120℃, and the pressure is 0.2-0.5MPa) through the feeding roller, so as to make the protective film and the front of the battery piece 1 tightly adhere to each other by roller pressing, to exclude air bubbles and ensure no wrinkles and no deviation.

[0072] S2, laying an insulating adhesive 6 on the back of the battery piece 1 to isolate the positive grid lines and the negative grid lines.

[0073] Specifically, if the cell piece is a multi-main grid cell piece, after the insulating protective film 8 is applied to the front surface of the cell piece 1, the insulating glue 6 needs to be applied to the back surface of the cell piece 1 to isolate the positive main grid 2 and the positive auxiliary grid 3 from the negative main grid 4 and the negative auxiliary grid 5. If the cell piece is a cell piece without main grid, after the insulating protective film 8 is applied to the front surface of the cell piece 1, the insulating glue 6 needs to be applied to the back surface of the cell piece 1 to isolate the positive auxiliary grid 3 from the negative auxiliary grid 5. Taking the cell piece without main grid as an example, because the spacing between the positive and negative auxiliary grids on the back surface is usually only 0.5-2 mm, the insulating glue 6 needs to achieve high insulation and precise isolation. The main body of the insulating glue 6 is an epoxy resin system (such as adding 5-8% silane coupling agent to improve the adhesion to the silicon wafer, and adding 3-5% aluminum hydroxide flame retardant to achieve UL94V-0 level). The application process adopts screen printing or inkjet printing: when screen printing is adopted, a 300-500 mesh stainless steel screen is selected to ensure that the roughness of the glue line edge is ≤5 μm, and the wet glue thickness is controlled to be 100-150 μm (70-120 μm after drying); when inkjet printing is adopted, a piezoelectric nozzle (resolution 1200 dpi) is adopted to realize non-contact coating through CAD paper positioning, which is suitable for split insulating glue 6 patterns. After printing, it needs to be dried by hot air at 80-120°C for 30-60s (gel rate ≥60%), to avoid deformation of the glue layer and pollution of the grid line in the subsequent process.

[0074] S3, applying the solder strip 7.

[0075] Specifically, the solder strip 7 needs to form effective electrical connection with the back surface main grid line and the bus PAD point as the core carrier for current transmission. Since the point soldering process is adopted in the present application, a pure copper solder strip 7 is preferred, and a 0.5-1 μm nickel layer can be plated if it is necessary to improve the oxidation resistance; the diameter range is 0.16-0.3 mm. In addition, the cross section of the solder strip 7 can also be flat or triangular. When the solder strip 7 is applied, the visual positioning system (CCD camera + image processing algorithm, positioning accuracy ±0.05 mm) is used to guide the mechanical arm operation, to ensure that the solder strip 7 is aligned with the main grid line with a deviation of ≤0.1 mm and an overlapping length of ≥0.5 mm; the tension of the solder strip 7 needs to be stably controlled to be 5-10 cN (tension fluctuation ≤±1 cN), to avoid hidden cracks of the cell piece 1 caused by excessive tension or solder strip 7 relaxation caused by too small tension. In addition, the temporary fixation of the solder strip 7 adopts low-viscosity organic silicone glue (viscosity 800±200 cP), and the silicone glue is applied at both ends of the solder strip 7 (glue point diameter 0.8±0.2 mm), so as not to affect the soldering reliability, and the silicone glue will be completely cured in the subsequent lamination process.

[0076] S4, a plurality of cell pieces 1 are overlapped in a shingle manner, wherein at least the overlapping parts of the adjacent cell pieces 1 are separated by the insulating protective film 8.

[0077] Specifically, the shingling lapping can reduce the invalid space inside the assembly, improve the overall effective light receiving area of the assembly, and thus improve the power density of the assembly, by arranging the edges of adjacent battery pieces 1 in overlapping manner instead of the traditional gap arrangement. The lapping parameters need to be accurately controlled: the back edge of the previous battery piece 1 overlaps the front edge of the next battery piece 1, the width of the lapping part is set to 0.2mm-1.0mm according to the size of the battery piece 1, and the electrical isolation of the overlapping area is borne by the insulating protective film 8 laid in step S1, the thickness of the protective film in this area needs to be ≥30μm and ≤120μm. For example, as shown in Figure 3 and Figure 4 the left edge of the right battery piece 1 overlaps the right edge of the left battery piece 1, this lapping method makes the adjacent battery pieces 1 form a "negative gap" arrangement. The insulating protective film 8 acts as an essential electrical insulation layer in this lapping area.

[0078] To ensure the shingling accuracy, a high-precision positioning stage is used, and the positioning marks on the edges of the battery pieces 1 are recognized by a machine vision system to guide the mechanical arm to complete the arrangement. A light pressure of 0.05-0.1MPa is applied during the shingling process to ensure that the battery pieces 1 are tightly attached and there is no risk of hidden cracks. Temporary fixation is achieved by using UV curing adhesive (preferably 365nm wavelength acrylate system UV adhesive), which is applied at an interval of 50-100mm in the non-overlapping area (adhesive point diameter 0.5-1mm), and after irradiation with ultraviolet light (intensity ≥80mW / cm 2 ) for 1-3s, the preliminary curing (curing rate ≥90%) is completed, which can effectively resist mechanical disturbance in subsequent processes and completely cure during the final lamination process.

[0079] S5, the solder strip 7 is welded to the metal contact point of the battery piece 1 by a spot tin soldering process.

[0080] Specifically, the surface of the metallized contact point (i.e. PAD point) on the back of the battery piece for connecting with the solder strip 7 needs to be clean before welding: the PAD point can be formed by silver paste printing. For example, Figure 5As shown in FIG. (5a), the spot-tinning mechanism is composed of a heating unit, a tin feeding unit and a positioning platform: the heating unit includes a tungsten alloy heating head 13, the heating temperature is accurately controlled at 200-300℃ (temperature difference ±5℃); the tin feeding unit selects a tin wire 15 with a diameter of 0.3-0.5mm, the tin feeding unit 14 carrying the tin wire 15 realizes quantitative tin feeding control with a precision of ±0.1mm through a precision gear set driven by a stepping motor; the positioning platform is used to carry and accurately position the battery string completed with shingle lap. When welding, as shown in FIG. (5b), the heating head 13 in the heating unit first melts the tin wire 15 to form a tin ball 16 (attached to the end of the heating head) with a diameter of 0.4-0.6mm, then the mechanism is lowered to a distance of 0.1-0.2mm from the surface of the battery sheet 1 (non-contact operation to avoid crushing the silicon wafer), the tin ball 16 fills the gap between the solder strip 7 and the PAD point under the action of surface tension and gravity, after filling, as shown in FIG. (5c), the heating state is maintained for 0.5-1s, after ensuring sufficient infiltration, the heating head 13 is moved upwards to make the tin ball 16 cool naturally, thereby completing the welding of the solder strip 7 and the PAD point. This non-contact spot-tinning welding process accurately controls the amount of tin, forms a reliable hemispherical solder joint, effectively connects the solder strip 7 and the PAD point, and at the same time avoids the large-area thermal shock caused by traditional welding (such as hot air or infrared), significantly reducing the risk of hidden cracks of the battery sheet 1.

[0081] S6, laying encapsulation adhesive film and cover plate.

[0082] Specifically, the encapsulation adhesive film includes a front encapsulation adhesive film 9 and a back encapsulation adhesive film 11. The encapsulation adhesive film needs to realize the bonding and weather protection of each layer of material of the assembly, and is preferably POE (polyolefin elastomer) or EVA (ethylene-vinyl acetate copolymer) material. Among them, the POE adhesive film has a volume resistivity ≥10 14 Ω·cm, has excellent PID (potential induced degradation) performance, and is suitable for high-reliability assemblies; the EVA adhesive film needs to ensure that the crosslinking degree is ≥85% (after lamination) to meet the temperature resistance requirements. The adhesive film thickness is usually 0.3-0.5mm, laid in a double-layer structure of “bottom adhesive film + battery pack + top adhesive film”, and the cutting size needs to be 5-10mm larger than the edge of the shingle battery pack (i.e. the structure formed after a plurality of battery sheets 1 are stacked in a shingle manner). The cover plate includes a front cover plate 10 and a back cover plate 12. The cover plate selects 3.2mm thick super-white tempered glass, the surface is laid with an anti-reflection film, and the edge is rounded to avoid cutting the adhesive film. It should be noted that laying the encapsulation adhesive film and the cover plate is a conventional technical means in the art, which will not be described in more detail here.

[0083] S7, laminating to form a photovoltaic assembly.

[0084] Specifically, the laminating process realizes the densification of the assembly through three stages of "vacuum-pressing-cooling": the vacuum stage needs to extract the vacuum degree in the laminating cavity to ≤100 Pa, and lasts for 3-5 min to completely remove the air between the adhesive film and each layer of material; the pressing stage raises the temperature to a specific temperature (such as POE adhesive film 140-150℃, EVA adhesive film 130-140℃) under a pressure of 0.1-0.2 MPa, and keeps it for 10-20 min to make the adhesive film completely melt and crosslink; the cooling stage controls the cooling rate ≤5℃ / min, and naturally cools to below 60℃ to avoid internal stress of the assembly due to temperature difference. After laminating, it needs to meet: no bubbles, no delamination, adhesive film crosslinking degree ≥85%; the excess adhesive film at the edge is trimmed to a width ≤1mm to ensure the sealing of the assembly.

[0085] By adopting the above preparation method, specifically, by precisely controlling the tin ball 16 to fill the gap through the spot tin soldering process, the quality of the solder joint can be significantly improved, ensuring that the tin ball 16 completely fills the gap of the metal contact point between the solder strip 7 and the battery piece 1, avoiding the problems of virtual welding or short circuit. In addition, the combination of shingle lap and spot tin soldering reduces the thermal stress by more than 80% compared with traditional welding, greatly reducing the hidden cracking rate of the battery piece 1.

[0086] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without deviating from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.

Claims

1. A photovoltaic module, characterized in that, The photovoltaic module is laminated from a front cover plate (10), a front encapsulating film (9), multiple solar cells (1), a back encapsulating film (11), and a back cover plate (12) stacked in sequence. Among the multiple solar cells, adjacent solar cells (1) overlap each other. An insulating protective film (8) is applied to the front of each solar cell (1). The insulating protective film (8) forms an electrical isolation layer at the overlap. The backs of adjacent solar cells (1) are connected by solder strips (7).

2. The photovoltaic module according to claim 1, characterized in that, The insulating protective film (8) is applied to the entire front surface area of ​​the battery cell (1).

3. The photovoltaic module according to claim 2, characterized in that, The insulating protective film (8) is made of one or more of EVA, POE, EPE, PVB, or TPO.

4. The photovoltaic module according to claim 3, characterized in that, The thickness of the insulating protective film (8) is 30μm to 120μm.

5. The photovoltaic module according to claim 3, characterized in that, The insulating protective film (8) is a non-pre-crosslinked film.

6. The photovoltaic module according to claim 1, characterized in that, The width of the overlapping portion is 0.2mm to 1.0mm.

7. A method for manufacturing a photovoltaic module, characterized in that, The preparation method includes: An insulating protective film (8) is applied to the front side of the battery cell (1); Insulating adhesive (6) is applied to the back of the battery cell (1) to isolate the positive grid lines (2, 3) and the negative grid lines (4, 5); Laying welding strip (7); Multiple solar cells (1) are stacked in a shingled manner, wherein at least the overlapping portions of adjacent solar cells (1) are separated by the insulating protective film (8); The solder strip (7) is soldered to the metal contact point of the battery cell (1) by a spot soldering process; Apply the encapsulating film (9, 11) and cover plate (10, 12); Photovoltaic modules are formed by lamination.

8. The method for preparing a photovoltaic module according to claim 7, characterized in that, The "applying an insulating protective film (8) to the front side of the battery cell (1)" includes: An insulating protective film (8) is applied to the entire front surface of the entire battery cell (1) using a thermal coating process; The entire solar cell (1) is sliced ​​to form solar cells (1) used to construct the photovoltaic module. The heating temperature of the heat coating process is 80℃~120℃.

9. The method for preparing a photovoltaic module according to claim 8, characterized in that, The "welding the solder strip (7) to the metal contact point of the battery cell (1) by spot soldering" includes: The solder wire (15) is heated by the heating unit of the soldering mechanism to form a solder ball (16), which is formed on the heating unit and is located at least on one side of the solder strip (7); When the solder feeding unit (14) of the soldering mechanism reaches the preset solder feeding amount, the heating head (13) of the heating unit is kept in a heating state and moves down to a preset height so that the solder ball (16) can fill the gap between the metal contact point of the solder strip (7) and the battery cell (1).

10. The method for preparing a photovoltaic module according to claim 9, characterized in that, The heating temperature of the heating unit is 200℃~300℃.

Images