A photovoltaic cell module and its connection process

Abstract

The present invention discloses a photovoltaic cell module and its connection process. In this photovoltaic cell module, the cells are arranged alternately and parallelly according to the positive and negative polarities. Between every two adjacent cells, a welding tape is placed along the length direction of the cells. Conductive adhesive is selectively coated at the center of the overlapping area between the main grid of the cell and the welding tape. Organosilicon rubber is coated at the center of the overlapping area between the cell and the welding tape or at a position relatively closer to the inner side of the cell. The welding tape and the cell are bonded and fixed through the cooperation of the organosilicon rubber or the organosilicon rubber and the conductive adhesive, realizing the series connection between the cells. The present invention uses a conductive adhesive and an organosilicon rubber both based on silicone to achieve the micro-elastic connection between the cell and the welding tape, enabling the internal stress to be dispersed to each adhesive position, reducing the risk of hidden cracks, and having a high yield rate for the cells in series. The conductive adhesive is arranged according to the need for conduction, forming several conduction positions between the welding tape and the cell, with a free conduction method, capable of achieving the inter-cell connection with zero spacing and negative spacing, and the photovoltaic conversion efficiency of the module is higher and more aesthetically pleasing.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cells, and particularly relates to a photovoltaic cell component and its connection process. Background Art

[0002] Currently, the series connection of IBC cells in the photovoltaic industry is achieved by laser welding for the hard connection between the solder tape and the pad point of the cell, or by coating the main grids on both sides of the IBC cell with conductive adhesive to bond with the solder tape.

[0003] In the hard connection method (such as laser welding, electromagnetic induction welding, etc.), cracks are likely to occur at the connection between the cell and the solder tape, and the internal stress is relatively large, so the cell is prone to warp along the direction of the solder tape. Usually, special-shaped solder tapes are required to release stress, and the process is complex and costly.

[0004] The soft connection method (such as conductive adhesive bonding) can effectively relieve the warping of the cell, but the connection strength is weak, and it is prone to de-welding in subsequent processes. In addition, using a whole section of conductive adhesive to bond the main grid of the cell and the solder tape also has the problem of high cost. Summary of the Invention

[0005] In order to solve the technical problems in the prior art that the welding process of IBC cells is difficult, costly, and has potential risks such as hidden cracks or de-welding, the purpose of the present invention is to provide a photovoltaic cell component and its connection process.

[0006] To achieve the above purpose and reach the above technical effects, the technical solution adopted by the present invention is as follows:

[0007] A photovoltaic cell component, in which the cells in the photovoltaic cell component are alternately arranged in parallel in the order of positive and negative polarities. A solder tape is placed between every two adjacent cells along the length direction of the cell. Conductive adhesive is selectively coated in the center of the overlapping area between the main grid of the cell and the solder tape, and silicone rubber is coated in the center of the overlapping area between the cell and the solder tape or at a position relatively close to the inner side of the cell. The solder tape and the cell are bonded and fixed through the cooperation of silicone rubber or silicone rubber and conductive adhesive to achieve the series connection between cells. The conductive adhesive and the silicone rubber are independently dispensed and jointly play a bonding role.

[0008] Furthermore, both the conductive adhesive and the silicone rubber are based on silicone to achieve the effect of micro-elastic connection. The silicone rubber has no conductivity, and the viscosity range of the silicone rubber is 50000 - 80000 cps, and the viscosity range of the conductive adhesive is 50000 - 60000 cps.

[0009] Furthermore, both the conductive adhesive and the silicone rubber are thermosetting adhesives, which can be preliminarily cured at 130°C to ensure the basic structural strength, and are completely cured after subsequent lamination and with the extension of the placement time.

[0010] Further, the conductive adhesive can be applied according to the requirement of the current distribution between the battery cells. The conductive adhesive can be fully coated in the center of the overlapping area between the main grid of the battery cell and the solder strip to achieve full-area conduction between the main grid of the battery cell and the solder strip, so as to adapt to the situation of large current. Or the conductive adhesive can be applied in segments in the center of the overlapping area between the main grid of the battery cell and the solder strip, so as to form several conduction areas between the main grid of the battery cell and the solder strip, reduce the amount of conductive adhesive while ensuring electrical performance, and save costs. The conductive adhesive and the silicone adhesive are alternately applied. The conductive adhesive with a specific quantity and size is applied according to the number of conduction points and the surface current density. The silicone adhesive is applied in the gaps of the conductive adhesive to increase the bonding strength, achieving a relatively small amount of conductive adhesive and a relatively narrow bonding width. The silicone adhesive is applied in the center of the overlapping area between the battery cell and the solder strip or at a position relatively close to the inner side of the battery cell. The silicone adhesive can overflow appropriately from the edge of the solder strip to achieve semi-wrapping of the solder strip, so as to further increase the bonding strength. Or the conductive adhesive can not be applied on the battery cell, and the main grid directly contacts the solder strip to form contact conduction, so as to achieve the maximum cost reduction.

[0011] Further, the distance between two adjacent battery cells is -0.3 to 0.6 mm. The battery cell is a back-contact solar cell, on which p+-doped regions and n+-doped regions are alternately arranged. There is one main grid on each of the two sides along the long side direction of the back of the battery cell. A plurality of sub-grids are arranged along the short side direction between the main grids. The sub-grids are arranged on the p+-doped regions and n+-doped regions of the battery cell and alternately lead to the two main grids on both sides. The main grid and the sub-grid are tin-plated copper grid lines.

[0012] Further, the main grid can be designed in a grid shape to further enhance the bonding effect with the glue.

[0013] Further, the solder strip is a tin-plated copper solder strip, a common copper solder strip or an aluminum solder strip with a rectangular cross-section, and can be a whole-section straight solder strip, a segmented solder strip or a special-shaped solder strip with holes or slots, so as to further release the internal stress generated by welding and improve the warpage of the component.

[0014] The present invention discloses a connection process for a photovoltaic cell module, including the following steps:

[0015] (1) Select a back-contact solar cell with p+-doped regions and n+-doped regions alternately arranged on the back and the current is respectively collected to the two main grids on both sides through the sub-grids;

[0016] (2) Selectively apply conductive adhesive in the center of the preset overlapping area between the main grid of the battery cell and the solder strip;

[0017] (3) Apply silicone adhesive in the center of the preset overlapping area between the battery cell and the solder strip or at a position relatively close to the inner side of the battery cell. The conductive adhesive and the silicone adhesive are applied independently.

[0018] (4) Arrange the battery wafers with glue applied in parallel in turn according to the positive and negative electrode polarities, and place a solder strip along the length direction of the battery wafer between every two adjacent battery wafers;

[0019] (5) Place a heat-insulating pressing block with elastic pressing needles on the battery wafers processed in step (4) to make the solder strip adhere to the battery wafers and ensure the flatness of the battery wafers;

[0020] (6) Pass the battery wafers with the heat-insulating pressing blocks placed in step (5) through the heating zone in turn to achieve local heating of the solder strip position, heat at a temperature of 130 °C for 30 s, and achieve the preliminary bonding of the solder strip and the battery wafers;

[0021] (7) Before and after the curing in step (6), set multiple heating zones to achieve a gentle heating and cooling curve, avoid stress accumulation, and reduce the warpage degree after stringing;

[0022] (8) Finally, connect multiple battery wafers in series through micro-elastic connections to obtain a photovoltaic cell module, with a maximum warpage degree less than 1.5 mm and a solder strip peel strength greater than 1.5 N.

[0023] In step (7), the process parameters of the heating and cooling curve are:

[0024] 50 °C ~ 70 °C ~ 90 °C ~ 110 °C ~ 130 °C ~ 110 °C ~ 90 °C ~ 70 °C ~ 50 °C, stay at 130 °C for 30 s, and stay at the other temperatures for 2 s each.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The present invention uses a conductive adhesive and an organosilicon rubber both based on silicone to achieve a micro-elastic connection between the battery cell and the solder strip. The organosilicon rubber has no electrical properties and mainly serves to increase the bonding strength and resistance to deformation, realizing a stable welding of the battery cell and the solder strip with low internal stress. The conductive adhesive is arranged at specific positions of the main grid of the battery cell according to the need for conduction, forming several conduction positions between the solder strip and the battery cell. The conductive adhesive can be independently dispensed according to the need of surface current distribution, which can be in the form of scattered points, segmented shapes, complementary to the organosilicon rubber, or in the form of continuous lines, arranged in parallel with the organosilicon rubber, providing more freedom in the conduction mode, with controllable glue volume, controllably meeting the conduction requirements, and lower cost. The organosilicon rubber and the conductive adhesive can play a micro-elastic role while curing and bonding, respectively strengthening the conductivity of the conductive adhesive and the adhesiveness of the organosilicon rubber, thus achieving a perfect match of the process. Compared with the existing hard connection method, the micro-elastic connection process proposed by the present invention has micro-elasticity, enabling the internal stress to be dispersed to each adhesive position, effectively reducing the risk of hidden cracks, with a high yield rate of the battery cells in series, and benefiting from this connection method, the overlapping width between the solder strip and the battery cell can reach less than 1 mm, and even a negative-spacing inter-chip connection can be achieved, thereby increasing the effective area of the module and obtaining better power generation benefits. In the aging test, the micro-elastic structure can disperse the stress caused by temperature changes to each connection position, effectively avoiding local stress accumulation and making the module have better weather resistance. Compared with the existing soft connection method, the micro-elastic connection process proposed by the present invention mainly relies on the insulating organosilicon rubber to provide structural strength, with a significant reduction in the amount of conductive adhesive used, lower cost, higher module strength, and a significantly reduced risk of de-soldering in subsequent processes, being adaptable to the needs of various battery cells and manufacturing processes, with higher photoelectric conversion efficiency and more aesthetic appearance of the module. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of the present invention;

[0028] Figure 2 is a schematic structural diagram of the battery cells in series after being connected in series according to the present invention;

[0029] Wherein, 1 - battery cell; 2 - main grid; 3 - sub-grid; 4 - conductive adhesive; 5 - organosilicon rubber; 6 - solder strip. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0031] A brief overview of one or more aspects is given below to provide a basic understanding of these aspects. This overview is not an exhaustive survey of all contemplated aspects and is neither intended to identify key or decisive elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to a more detailed description given later.

[0032] As Figure 1-2 shown, a photovoltaic cell assembly. In this photovoltaic cell assembly, the cells 1 are arranged in parallel in turn with alternating positive and negative polarities. Between every two adjacent cells 1, a welding strip 6 is placed along the long side direction of the cell 1. Each welding strip 6 is bonded between two adjacent cells 1. At the center of the overlapping area between the main grid 2 of each cell 1 and the welding strip 6, a conductive adhesive 4 is selectively coated. At the center of the overlapping area between each cell 1 and the welding strip 6 or at a position relatively close to the inner side of the cell 1, a silicone rubber 5 is coated. The silicone rubber 5 has no conductivity. Through the cooperation of the silicone rubber 5 or the silicone rubber 5 and the conductive adhesive 4, the welding strip 6 is bonded and fixed to two adjacent cells 1, thereby realizing the series connection between two adjacent cells 1. The conductive adhesive 4 and the silicone rubber 5 are coated independently and jointly play a bonding role.

[0033] Both the conductive adhesive 4 and the silicone rubber 5 are based on silicone to achieve the effect of micro-elastic connection, and the silicone rubber 5 has no conductivity.

[0034] The conductive adhesive 4 can be coated according to the need of the current distribution between the cells 1. The conductive adhesive 4 can be coated entirely at the center of the overlapping area between the main grid 2 of the cell 1 and the welding strip 6 to achieve full-area conduction between the main grid 2 and the welding strip 6 to adapt to the situation of larger current. Or the conductive adhesive 4 can be coated in segments at the center of the overlapping area between the main grid 2 and the welding strip 6 to form several conduction areas between the main grid 2 and the welding strip 6, reducing the amount of the conductive adhesive 4 while ensuring electrical performance and saving costs. The conductive adhesive 4 and the silicone rubber 5 are coated alternately. According to the number of conduction points and the surface current density, a specific number and size of the conductive adhesive 4 are coated. The silicone rubber 5 is coated in the gap of the conductive adhesive 4 to increase the bonding strength, realizing a relatively small amount of the conductive adhesive 4 used and a relatively narrow bonding width. The silicone rubber 5 is coated at the center of the overlapping area between the cell 1 and the welding strip 6 or at a position relatively close to the inner side of the cell 1. The silicone rubber 5 can overflow appropriately from the edge of the welding strip 6 to achieve semi-wrapping of the welding strip 6 to further increase the bonding strength. Or the conductive adhesive 4 can not be coated on the cell 1, and the main grid 2 directly contacts the welding strip 6 to conduct electricity, thereby achieving the maximum cost reduction.

[0035] The present invention discloses a connection process for photovoltaic cell components, which uses a conductive adhesive and an organosilica gel both based on silica gel to achieve a micro-elastic connection between the cell and the solder strip, and can respectively strengthen the conductivity of the conductive adhesive and the adhesiveness of the organosilica gel, so as to achieve a perfect match of the process. The connection process specifically includes the following steps:

[0036] (1) Select a back-contact solar cell with p+-doped regions and n+-doped regions alternately arranged on the back and respectively converging to the main grids 2 on both sides through the sub-grid 3;

[0037] (2) Selectively apply a conductive adhesive 4 at the center of the preset overlapping area between the main grid 2 of the cell 1 and the solder strip 6;

[0038] (3) Apply an organosilica gel 5 at the center of the preset overlapping area between the cell 1 and the solder strip 6 or at a position relatively close to the inner side of the cell 1. The conductive adhesive 4 and the organosilica gel 5 are applied independently;

[0039] The conductive adhesive 4 of the present invention can be selectively laid according to actual needs, and a good micro-elastic connection between the cell and the solder strip can also be achieved only by relying on the organosilica gel 5;

[0040] (4) Arrange the cells 1 with the applied adhesives alternately and parallelly in sequence according to the positive and negative electrode polarities, and place the solder strip 6 along the length direction of the cell 1 between every two adjacent cells 1;

[0041] (5) Place a heat-insulating pressing block with elastic pressing needles on the cell 1 processed in step (4) to make the solder strip 6 contact the cell 1 and ensure the flatness of the cell 1;

[0042] (6) Make the cell 1 with the heat-insulating pressing block placed in step (5) pass through the heating zone in sequence to achieve local heating of the position of the solder strip 6, and heat at a temperature of 130°C for 30 s to achieve the preliminary bonding between the solder strip 6 and the cell 1;

[0043] (7) Before and after the curing in step (6), set multiple heating zones to achieve a gentle heating and cooling curve, avoid stress accumulation, and reduce the warpage degree after stringing;

[0044] (8) Finally, connect multiple cells 1 in series through micro-elastic connection to obtain a photovoltaic cell component, with a maximum warpage degree less than 1.5 mm and a solder strip peel strength greater than 1.5 N.

[0045] In step (7), the process parameters of the heating and cooling curve are:

[0046] 50°C - 70°C - 90°C - 110°C - 130°C - 110°C - 90°C - 70°C - 50°C, stay at 130°C for 30 s, and stay at the other temperatures for 2 s each.

[0047] Example 1

[0048] As shown Figure 1-2 in the figure, a photovoltaic cell module is provided. In the photovoltaic cell module, the cells 1 are arranged alternately and parallelly in positive and negative polarities. A welding tape 6 is placed between every two adjacent cells 1 along the long side direction of the cell 1. The distance between every two adjacent cells 1 is -0.3 to 0.6 mm. Each welding tape 6 is bonded between two adjacent cells 2. Conductive glue 4 is selectively coated at the center of the overlapping area between the main grid 2 of each cell 1 and the welding tape 6. Organosilicon glue 5 is coated at the center of the overlapping area between each cell 1 and the welding tape 6 or at a position relatively close to the inner side of the cell 1. The welding tape 6 is bonded and fixed to two adjacent cells 1 through the organosilicon glue 5 or the organosilicon glue 5 and the conductive glue 4, thereby realizing the series connection between every two adjacent cells 1. The conductive glue 4 and the organosilicon glue 5 are independently dispensed and jointly play a bonding role.

[0049] The cell 1 used in the present invention is a back-contact solar cell, on which p+ doped regions and n+ doped regions are alternately arranged. There is one main grid 2 on each side of the back of the cell 1 along the long side direction of the cell 1. A plurality of sub-grids 3 are arranged between the main grids 2 along the short side direction of the cell 1. The sub-grids 3 are arranged on the p+ doped regions and n+ doped regions of the cell 1 and alternately lead to the two main grids 2 on both sides. The main grid 2 and the sub-grids 3 are tin-plated copper grid lines. The main grid 2 can further enhance the bonding performance with the glue through a grid-like design.

[0050] As a specific embodiment, a plurality of conductive glues 4 are segmented and coated at the center of the overlapping area between the main grid 2 of the cell 1 and the welding tape 6, and a plurality of organosilicon glues 5 are segmented and coated at the center of the overlapping area between the cell 1 and the welding tape 6 or at a position relatively close to the inner side of the cell 1. The conductive glue 4 and the organosilicon glue 5 are respectively coated in the gaps between each other and are alternately dispensed. The coating of the conductive glue and the organosilicon glue can be formed at one time or independently dispensed by using various methods such as printing and dispensing.

[0051] Both the conductive glue 4 and the organosilicon glue 5 are thermosetting glues, which can be preliminarily cured at 130°C to ensure the basic structural strength, and are completely cured after subsequent lamination and with the extension of the placement time.

[0052] The dosage ratio of the conductive glue 4 and the organosilicon glue 5 can be adjusted according to the needs of conductivity and bonding strength. The organosilicon glue can appropriately overflow from the edge of the welding tape 6 to realize the semi-wrapping of the welding tape 6, thereby further increasing the bonding firmness;

[0053] The organosilicon glue 5 can assist in insulating the welding tape 6 from the sub-grid 3 to avoid short circuit;

[0054] The welding tape 6 can be designed as a segmented welding tape, a special-shaped welding tape, etc., so that the internal stress is fully released, and the warping of the cell along the welding tape direction after welding is further reduced.

[0055] A connection process for a photovoltaic cell module, comprising the following steps:

[0056] (1) Select a back-contact solar cell with p+-doped regions and n+-doped regions alternately arranged on the back and respectively converging to the main grids 2 on both sides;

[0057] (2) Use screen printing to selectively apply a conductive adhesive to the center of the preset overlapping area between the main grid 2 of the cell 1 and the solder strip 6;

[0058] (3) Use a piezoelectric valve to apply an organic silicone adhesive to the center of the preset overlapping area between the cell 1 and the solder strip 6 and at a position relatively close to the inner side of the cell 1. Both the conductive adhesive and the organic silicone adhesive are applied in segments and alternately;

[0059] (4) Align and arrange the cells 1 with the adhesive applied in sequence according to the electrode polarities. The cells 1 are arranged alternately according to the positive and negative polarities to meet the requirements of series connection. Subsequently, place the solder strip 6 between the cells 1 along the direction perpendicular to the module;

[0060] (5) Place a heat-insulating pressing block with elastic pressing pins on the cells 1 processed in step (4) to make the solder strip 6 contact with two adjacent cells 1 and ensure the flatness of the cells 1;

[0061] (6) Pass the cells 1 with the heat-insulating pressing block placed in step (5) through the heating zone in sequence to achieve local heating of the position of the solder strip 6. Heat at a temperature of 130 °C for 30 s to achieve the preliminary bonding between the solder strip 6 and two adjacent cells 1;

[0062] (7) Before and after the curing in step (6), set multiple heating zones to achieve a gentle heating and cooling curve, avoid stress accumulation, and reduce the warpage degree after series production;

[0063] (8) Finally, connect the series cells 1 through micro-elastic connection to obtain a photovoltaic cell module with a maximum warpage degree less than 1.5 mm and a solder strip peel strength greater than 1.5 N.

[0064] In step (7), the process parameters of the heating and cooling curve are:

[0065] 50 °C - 70 °C - 90 °C - 110 °C - 130 °C - 110 °C - 90 °C - 70 °C - 50 °C, stay at 130 °C for 30 s, and stay at the other temperatures for 2 s each.

[0066] It should be noted that the results of alternately applying the conductive adhesive and the organic silicone adhesive achieved by other means, the alternately applied arrays of the conductive adhesive and the organic silicone adhesive with other similar patterns, and the use of other types of conductive adhesives and organic silicone adhesives are also within the protection scope of the present invention.

[0067] The present invention has at least the following beneficial effects:

[0068] By introducing organic silicone into welding, the micro-elastic connection of photovoltaic cell modules is achieved, which improves the hidden cracking and warping problems of the existing hard connection method and the desoldering problem of the existing soft connection method, improves the efficiency and stability of the module, and reduces the cost;

[0069] Compared with hard connection, micro-elastic connection can effectively release or disperse internal stress and reduce the risk of hidden cracks. Thanks to the absence of special-shaped welding strips, the spacing between cells can be very small, and even negative spacing can be connected in series, thereby increasing the effective area of the component and obtaining better power generation efficiency. In addition, in the aging test, the micro-elastic structure can disperse the stress caused by temperature changes to each connection position, effectively avoiding local stress accumulation and making the component more weather-resistant.

[0070] Compared with the soft connection method, the micro-elastic connection mainly relies on insulating organic silicone to provide structural strength. The amount of conductive glue used is greatly reduced, the cost is lower, and the component strength is higher. The risk of desoldering in subsequent processes is significantly reduced. The conductive glue can be independently applied according to the needs of surface current distribution. It can be scattered points or segments to complement the insulating glue, or it can be continuous lines and arranged in parallel with the insulating glue. Therefore, it is more free in the conduction method and can adapt to the needs of various battery cells and processes;

[0071] The micro-elastic connection can enhance the conductivity of the conductive glue and the adhesion of the organic silicone respectively, thus achieving a perfect match of the process.

[0072] It is not only applicable to the connection between the back contact solar cell and the welding ribbon 6, but also applicable to the shingling of the solar cell 1, the connection between the cells of the module and the string connection.

[0073] Parts or structures not specifically described may adopt existing technologies or existing products and will not be described in detail here.

[0074] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A connection process for a photovoltaic cell module, characterized in that, It includes the following steps: (1) Select a back-contact solar cell with p+-doped regions and n+-doped regions alternately arranged on the back and respectively converging to the main grids on both sides through sub-grids; (2) Apply conductive adhesive at the center of the preset overlapping area between the main grid of the cell and the solder strip; (3) Apply silicone rubber at a position relatively close to the inner side of the cell in the preset overlapping area between the cell and the solder strip. The conductive adhesive and the silicone rubber are applied independently; (4) Arrange the cells with the adhesive applied in parallel alternately in sequence according to the positive and negative electrode polarities, and place a solder strip in the position between every two adjacent cells along the length direction of the cell; (5) Place a heat-insulating pressing block with elastic pressing pins on the cells processed in step (4) to make the solder strip fit with the cells and ensure the flatness of the cells; (6) Make the cells with the heat-insulating pressing block placed in step (5) pass through multiple hot zones in sequence to realize local heating of the solder strip position and realize the preliminary bonding between the solder strip and the cells; (7) After step (6), realize gentle temperature rise and fall again through multiple hot zones to avoid stress accumulation and reduce the warpage degree after series production; (8) Finally, connect multiple cells in series through micro-elastic connections to obtain a photovoltaic cell module with a maximum warpage degree less than 1.5 mm and a solder strip peel strength greater than 1.5 N; The temperature process parameters of the multiple hot zones are as follows: 50°C ~ 70°C ~ 90°C ~ 110°C ~ 130°C ~ 110°C ~ 90°C ~ 70°C ~ 50°C, stay at 130°C for 30 s, and stay at each of the other temperature segments for 2 s.

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