Photovoltaic module and preparation method thereof

Abstract

The invention relates to the field of photovoltaic technology, and aims to solve the problems of warping, delaminating, light transmission loss and process damage in the packaging of the existing photovoltaic module. Therefore, the photovoltaic module and the preparation method thereof are provided, the photovoltaic module is formed by laminating a front cover plate, a front packaging adhesive layer, a front pre-fixing layer, a battery piece, a back pre-fixing layer, a back packaging adhesive layer and a back cover plate which are stacked in sequence, the back pre-fixing layer is provided with a conductive pre-empty hole, and a first conductor and a second conductor in the hole are electrically connected to export carriers; the preparation method comprises the steps of pre-solid layer forming, conductor laying, laminating and the like. According to the invention, through the dual protection of the pre-solid layer and the design of the precise conductive path, the cooperative improvement of high reliability, high power output and process protection is realized.

Description

TECHNICAL FIELD

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

[0002] Under the background of accelerating low-carbon transformation of global power structure, the demand for electricity in the fields of industry, building and transportation continues to grow, and the proportion of clean energy in terminal consumption is increasing year by year. Photovoltaic power generation has the potential to become one of the largest clean energy forms due to its wide resource distribution and mature application mode. The industry focuses on the back contact cell (such as IBC and HBC) technical route, which can realize high color value and high power output due to the characteristics of no grid line blocking on the front side. However, the existing packaging process still has serious technical bottlenecks that restrict its development.

[0003] Currently, the packaging of back contact cells mainly relies on high-temperature welding or low-temperature bonding schemes. High-temperature welding causes local thermal stress concentration, resulting in cell warping. Low-temperature bonding has three defects: structural failure risk: dense grid lines and insulating glue hinder the flow of glue film, forming a cavity, which causes delamination due to poor thermal stability of the glue film in outdoor thermal cycling; light transmission loss: the light transmission rate of traditional EVA glue film after lamination is only 91-93%, causing power loss of the module; process damage: the front side of the cell lacks a protective layer, which is easily scratched during production.

[0004] Therefore, the traditional packaging structure cannot balance high reliability packaging and efficient current conduction. The glue film cannot fully fill the micron-level grid line gap, and its low Tg (Glass Transition Temperature, which refers to the temperature critical point of the polymer from rigid glass state to elastic high-elasticity state) cannot meet the stringent requirements of back contact cells on thermal stress; while high-temperature welding ensures conductivity, but at the cost of structural stability.

[0005] Therefore, there is an urgent need for an innovative packaging solution that can simultaneously solve the problems of warping, delamination, light transmission loss and process protection. SUMMARY

[0006] The present application aims to solve the above technical problems, that is, at least one of the problems of warping, delamination, light transmission loss and process damage in the packaging process of the existing photovoltaic module.

[0007] To this end, in a first aspect, the present application provides a photovoltaic module, which is laminated by a front cover, a front encapsulation adhesive layer, a front pre-solidification layer, a cell, a back pre-solidification layer, a back encapsulation adhesive layer and a back cover in sequence, wherein the back of the cell is provided with positive and negative fine grids, the back pre-solidification layer is formed with a plurality of arrayed conductive pre-holes, part of the conductive pre-holes correspond to the positive fine grids, and part of the conductive pre-holes correspond to the negative fine grids, a first conductor is laid in the conductive pre-holes, the first conductor is higher than the surface of the back pre-solidification layer and is electrically connected with a second conductor, so that the photo-generated carriers collected by the positive and negative fine grids can be output after being converged by the second conductor.

[0008] In some preferred embodiments of the photovoltaic module, the material of the back pre-solidification layer is organic silicone adhesive.

[0009] In some preferred embodiments of the photovoltaic module, the depth of the conductive pre-hole is the same as the thickness of the back pre-solidification layer.

[0010] In some preferred embodiments of the photovoltaic module, the thickness of the back pre-solidification layer is 20-50 μm.

[0011] In some preferred embodiments of the photovoltaic module, the height of the first conductor is greater than the thickness of the back pre-solidification layer.

[0012] In some preferred embodiments of the photovoltaic module, the difference between the height of the first conductor and the thickness of the back pre-solidification layer is 5-10 μm.

[0013] In some preferred embodiments of the photovoltaic module, the material of the front pre-solidification layer is the same as that of the back pre-solidification layer.

[0014] In some preferred embodiments of the photovoltaic module, the front encapsulation adhesive layer is an organic silicone adhesive layer or adhesive film; and / or

[0015] The back encapsulation adhesive layer is an organic silicone adhesive layer or adhesive film.

[0016] In some preferred embodiments of the photovoltaic module, the edge of the photovoltaic module is further provided with an edge sealing adhesive.

[0017] In some preferred embodiments of the photovoltaic module, the distance between the edge sealing adhesive and the edge of the front encapsulation adhesive layer and the back encapsulation adhesive layer is 1-2 mm; and / or

[0018] The thickness of the edge sealing adhesive is 1-3 mm, and the height is 5-10 mm.

[0019] In a second aspect, the present application also provides a method for preparing a photovoltaic module, the method comprising:

[0020] applying silicone glue on the cell and pre-curing, wherein at least patterned silicone glue is applied on the back of the cell and pre-cured to form a back pre-cured layer, the back pre-cured layer having an array of a plurality of conductive pre-holes corresponding to the positive and negative fine grids on the back of the cell respectively;

[0021] applying a first conductor in the conductive pre-hole, the first conductor being higher than the surface of the back pre-cured layer;

[0022] applying a second conductor to electrically connect the corresponding first conductor;

[0023] forming a cell string;

[0024] applying an encapsulation glue layer and a cover plate;

[0025] laminating to form a photovoltaic module.

[0026] In some preferred embodiments of the above method for preparing a photovoltaic module, the step of applying silicone glue on the cell and pre-curing further comprises:

[0027] applying silicone glue on the front of the cell and pre-curing to form a front pre-cured layer.

[0028] In some preferred embodiments of the above method for preparing a photovoltaic module, the conductive pre-hole has the same depth as the thickness of the back pre-cured layer; and / or

[0029] the thickness of the back pre-cured layer is 20-50 μm; and / or

[0030] the difference between the height of the first conductor and the thickness of the back pre-cured layer is 5-10 μm.

[0031] In some preferred embodiments of the above method for preparing a photovoltaic module, the step of applying an encapsulation glue layer and a cover plate comprises:

[0032] applying silicone glue on the cover plate and pre-curing, wherein the cover plate comprises a front cover plate and a back cover plate.

[0033] In some preferred embodiments of the above method for preparing a photovoltaic module, the encapsulation glue layer is an encapsulation glue film.

[0034] In some preferred embodiments of the above method for preparing a photovoltaic module, the back pre-solidification layer and the front pre-solidification layer are formed by a pre-solidification mold, the working temperature of the pre-solidification mold is 80-120 DEG C, and the pressing time is 5-10 seconds.

[0035] The pre-solidification mold comprises an upper pressing pre-solidification mold, and the upper pressing pre-solidification mold is provided with a convex structure matching the conductive pre-hole.

[0036] The photovoltaic module provided by the application forms a double protection and structural optimization for the cell sheet by setting the front pre-solidification layer and the back pre-solidification layer. The front pre-solidification layer solves the process damage problem of easy scratching of the cell front in the traditional scheme, and guarantees the appearance integrity. The back pre-solidification layer fills the gap between the grid lines to reduce the cavity rate and resist outdoor thermal cycle deformation to reduce the delamination risk by virtue of the pre-solidified shaped structure and the optional high-Tg material. The two cooperate to form a sandwiched protection structure, disperse thermal stress to reduce warping, and avoid the functional conflict of the traditional single adhesive film through the functional partition design with the encapsulation adhesive layer. Meanwhile, the back pre-solidification layer conductive pre-hole and the conductor realize efficient current output, and the cover plate and the encapsulation adhesive layer strengthen the sealing and light transmission performance, finally solving the problem that the protection and the conductivity, the sealing and the thermal stability cannot be compatible in the traditional scheme, and realizing the synergistic improvement of high reliability, high power output and process protection.

[0037] Further, by using the organic silicone adhesive, the photovoltaic module provided with the organic silicone adhesive pre-solidification layer can effectively resist the thermal stress impact of the outdoor environment and reduce the delamination risk caused by material aging, because the organic silicone adhesive has excellent high and low temperature resistance and weather resistance, and can maintain stable physical and chemical properties in a wide temperature range. At the same time, the organic silicone adhesive has good adhesion and sealing performance, and can be tightly combined with the back of the cell sheet and other encapsulation layers, further improving the structural stability of the photovoltaic module, and solving the defects of the traditional adhesive film in thermal stability.

[0038] Further, because the traditional encapsulation scheme has the problem that the adhesive film is difficult to fully fill the micron-level grid line gap, and is easy to form a cavity to affect current conduction and structural stability. The application can ensure that the laying depth of the first conductor in the conductive pre-hole matches the back pre-solidification layer by setting the depth of the conductive pre-hole to be consistent with the thickness of the back pre-solidification layer, so that the first conductor can not only fully contact the positive and negative fine grids on the back of the cell sheet to ensure the smoothness of current conduction, but also avoid poor contact or structural defects caused by improper depth of the conductive pre-hole, thereby optimizing the current output path and improving the power generation efficiency and structural reliability of the photovoltaic module.

[0039] Further, the conventional packaging structure is difficult to balance the protection performance and the conduction efficiency in the thickness design. The thickness range of the pre-solidification layer provided by the present application can provide sufficient support and protection for the back surface of the battery sheet, effectively isolate the influence of the external environment on the grid line, and reduce the interference of external factors on current collection. On the other hand, the thickness will not be too thick to increase the overall weight and cost of the assembly, nor too thin to fail to effectively protect and insulate, while it can adapt to the laying requirements of the first conductor in the conductive pre-hole, and ensure the balance of the photovoltaic assembly in protection and performance.

[0040] Further, the current conduction path of the conventional packaging may have efficiency loss problems due to insufficient contact of the conductive body with the busbar component. By setting the height of the first conductor to exceed the surface of the back pre-solidification layer, the present application can ensure reliable electrical connection between the first and second conductors, increase the contact area, reduce the contact resistance, reduce the loss of current during conduction, improve the efficiency of the current output of the photo-generated carriers, and solve the power loss problem caused by poor contact of the conductive body in the conventional scheme.

[0041] Further, the difference range between the first conductor and the back pre-solidification layer provided by the present application not only ensures sufficient contact between the first and second conductors, ensuring the stability and efficiency of current conduction, but also avoids excessive extrusion of the first conductor during lamination and other processes due to excessive difference, or poor contact due to insufficient difference, further improving the reliability of current conduction of the photovoltaic assembly.

[0042] Further, the front and back pre-solidification layers of the same material can make the protection performance and physical and chemical properties of the front and back surfaces of the battery sheet consistent, and the deformation degree of the front and back surfaces similar under the influence of environmental factors such as temperature changes, reducing the internal stress caused by material differences and reducing the risk of battery sheet warping. At the same time, it is convenient for material management and process control in the production process, and improves the overall stability and production efficiency of the photovoltaic assembly.

[0043] Further, the organic silicone adhesive layer has good weather resistance and sealing property, and is suitable for scenes with high reliability requirements (its light transmittance is usually 92-94%); the adhesive film has more advantages in light transmittance (such as POE adhesive film with light transmittance of 94-96%), and is suitable for scenes with high power output requirements. This flexible choice can make the photovoltaic assembly better adapt to different use environments and performance requirements, and improve the applicability of the product.

[0044] It should be noted that in the present application, the temperature resistance of the organic silicone adhesive used for pre-solidification and the organic silicone adhesive layer used for packaging can be different, which can be realized by adjusting the proportion of cross-linking agent, high-temperature resistant component, etc. in the component, which can ensure the reliability of the key parts and avoid waste of material cost.

[0045] Further, by adopting edge sealing glue, such as butyl glue, the excellent air and water tightness of the edge sealing glue is utilized, which can effectively prevent external water vapor and impurities from entering the inside of the module, prevent the battery sheet and internal circuit from being corroded and polluted, delay the aging speed of the module, improve the long-term reliability and service life of the photovoltaic module, and solve the deficiency of traditional packaging in edge sealing.

[0046] Further, by setting a spacing of 1-2mm, the mutual interference of the edge sealing glue and the packaging glue layer during lamination can be avoided, ensuring the smooth progress of the lamination process; the thickness of 1-3mm and the height of 5-10mm can ensure that the edge sealing glue has sufficient sealing performance and structural strength, effectively plays a sealing role, and further optimizes the edge sealing effect of the module.

[0047] The preparation method provided by the present application can precisely construct the protective structure and the conductive path by pre-applying and pre-solidifying the silicone glue on the battery sheet to form a pre-solid layer, ensuring the close combination of the pre-solid layer and the battery sheet; the first conductor is applied in the conductive pre-hole and connected to the second conductor, ensuring the reliability of current conduction; the subsequent lamination and other steps firmly combine the layers, and the overall process solves the problems of warping, delamination, process damage and the like in the traditional preparation method, improving the preparation quality and performance of the photovoltaic module.

[0048] Further, by setting the front pre-solid layer, the battery sheet front is directly physically protected, which can effectively avoid scratches and other process damage during production, and the stable structure of the pre-solid layer helps to maintain the integrity and light transmittance of the battery sheet front, ensuring the high color value and high power output of the photovoltaic module, and making up for the defects of the traditional scheme in front protection.

[0049] Further, the depth of the conductive pre-hole is the same as the thickness of the back pre-solid layer, ensuring good contact between the conductive body and the grid line; the back pre-solid layer thickness of 20-50um balances protection and performance; the difference of 5-10um ensures the reliability of the conductive body connection. The optimization of these parameters makes the structure of the photovoltaic module more reasonable and the performance more stable, improving the current conduction efficiency and the reliability of the module.

[0050] Further, the cover plate is pre-solidified with a silicone glue layer, which can enhance the adhesion between the cover plate and the packaging glue layer and other structures, making the cover plate and the module body more firmly combined, improving the structural strength and sealing performance of the module, reducing the performance decline caused by loose cover plate, and further improving the reliability of the photovoltaic module.

[0051] Further, the packaging glue film has high light transmittance, which can allow more sunlight to pass through the packaging layer to reach the battery sheet, improve the solar energy absorption efficiency, and thus improve the power output of the photovoltaic module, solving the problem of large light transmittance loss of traditional packaging materials.

[0052] Further, the working temperature of 80-120℃ and the pressing time of 5-10 seconds can make the silicone glue pre-cured rapidly under suitable conditions to form a stable pre-cured layer structure; the matching of the upper pressing pre-cured mold and the protruding structure of the conductive pre-hole ensures the accurate forming of the conductive pre-hole. The process setting ensures the quality and precision of the pre-cured layer and lays a foundation for the high performance of the photovoltaic module. BRIEF DESCRIPTION OF DRAWINGS

[0053] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. In the drawings:

[0054] Figure 1 The schematic diagram of the back structure of the battery piece provided for the embodiments of the present application is shown in the figure;

[0055] Figure 2 The schematic diagram of the structure of the battery piece after the back pre-cured layer is applied to the back of the battery piece provided for the embodiments of the present application is shown in the figure;

[0056] Figure 3 The schematic diagram of the structure of the battery piece after the back pre-cured layer and the first conductive body are applied to the back of the battery piece provided for the embodiments of the present application is shown in the figure;

[0057] Figure 4 The schematic diagram of the structure of the battery piece after the second conductive body is connected to the back of the battery piece provided for the embodiments of the present application is shown in the figure;

[0058] Figure 5 The cross-sectional view of the film when the front pre-cured layer and the back pre-cured layer of the battery piece are pre-cured to form the front pre-cured layer and the back pre-cured layer provided for the embodiments of the present application is shown in the figure;

[0059] Figure 6 The cross-sectional view of the photovoltaic module provided for the embodiments of the present application is shown in the figure.

[0060] LIST OF REFERENCE NUMERALS

[0061] 1. battery piece; 2. back pre-cured layer; 21. conductive pre-hole; 3. first conductive body; 4. second conductive body; 5. front pre-cured layer; 6. pre-cured mold; 61. upper pressing pre-cured mold; 611. pre-hole filling mold; 62. lower pressing pre-cured mold; 7. back encapsulation part; 71. back encapsulation glue layer; 72. back cover plate; 8. front encapsulation part; 81. front encapsulation glue layer; 82. front cover plate; 9. edge encapsulation glue. DETAILED DESCRIPTION

[0062] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application and are not used to limit the protection scope of the present application. Those skilled in the art can make adjustments according to the needs in order to adapt to specific application occasions.

[0063] To better illustrate the invention, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that the invention can be practiced without certain specific details.

[0064] In the description of this invention, terms such as "upper," "lower," "inner," "outer," "front," and "rear," which indicate direction or positional relationships, are based on the illustrated directions or positional relationships and are used merely for ease of description. They do not indicate or imply that the device to be protected must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the orientations in the following embodiments should not be construed as limitations on this invention. Furthermore, ordinal numbers such as "first" and "second" are used only for convenience of explanation and are not used to indicate or imply relative importance.

[0065] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0066] This invention addresses the encapsulation challenges of back-contact batteries (such as IBC and HBC) by proposing a photovoltaic module structure and fabrication method that integrates pre-solidification layer protection and precise conductive path, aiming to simultaneously solve the problems of warpage, delamination, light transmission loss, and process damage in traditional encapsulation.

[0067] The following is combined with Figures 1 to 6 The photovoltaic module and its preparation method provided by the present invention will be described using the packaging of a gridless back contact cell as an example.

[0068] like Figure 6 As shown, the photovoltaic module provided by this invention has an overall structure composed of multiple layers of functional materials stacked sequentially and cured through a lamination process. From the light-receiving surface to the back surface (from bottom to top in the figure), the layers are: front cover plate 82, front encapsulating adhesive layer 81, front pre-curing layer 5, solar cell 1, back pre-curing layer 2, back encapsulating adhesive layer 71, and back cover plate 72. The edges are sealed with edge sealing adhesive 9. The synergistic effect of each layer ensures both the high-efficiency power generation of the solar cell 1 and improves the long-term reliability of the module.

[0069] Specifically, in this embodiment of the invention, the solar cell 1 adopts a back-contact structure (such as IBC or HBC), with no grid lines obstructing its front side, maximizing sunlight reception and improving light absorption efficiency; the back side is densely covered with mutually insulated positive and negative fine grids for collecting photogenerated carriers (holes and electrons). These fine grids are arranged in an interdigitated or arrayed manner, directly contacting the PN junction region inside the solar cell 1, shortening the carrier transport path and reducing losses. Figure 1 As shown in the illustration, this embodiment uses the arrangement of positive and negative electrode fine grids as an example. The positive and negative electrode fine grids extend continuously along the first direction and are alternately arranged along the second direction. The first and second directions are perpendicular to each other in the plane where the battery cell 1 is located. The positive electrode fine grids specifically collect holes, while the negative electrode fine grids collect electrons, laying the foundation for subsequent current extraction.

[0070] In the encapsulated component structure, the back pre-bonding layer 2 is crucial for achieving high-efficiency conductivity and structural stability. In this invention, the back pre-bonding layer 2 is made of silicone rubber with a thickness of 20μm to 50μm, and together with the front pre-bonding layer 5, it ensures balanced stress on the solar cell 1. Figure 2 As shown, the surface of the back pre-bonding layer 2 has multiple arrayed conductive pre-holes 21. The positions of these conductive pre-holes 21 correspond one-to-one with the positive and negative electrode grids on the back of the battery cell 1, and their depth is the same as the thickness of the back pre-bonding layer 2 (i.e., completely penetrating the pre-bonding layer). This design fundamentally solves the cavity problem of traditional encapsulants: in traditional encapsulation, the encapsulant film is difficult to fill the micron-level gaps due to the obstruction of dense grid lines, easily forming cavities, which are prone to delamination due to stress concentration during thermal cycling. However, the conductive pre-holes 21 in this invention are pre-formed by a mold, which can accurately expose the grid lines and avoid the situation of unfilled gaps. Experimental data shows that this design can reduce the cavity rate to below 0.1%, significantly reducing the risk of delamination.

[0071] like Figure 3As shown in FIG. 1, the first conductive body 3 is arranged in the conductive pre-hole 21, and the material of the first conductive body 3 can be bismuth-containing low-temperature tin such as tin bismuth lead, tin bismuth silver, and tin bismuth silver lead. The main function of the first conductive body 3 is to serve as a conductive medium to conduct the photo-generated carriers collected by the positive fine grid and the negative fine grid to the second conductive body 4 electrically connected thereto. If it is a back contact cell with a main grid, the size of the conductive pre-hole 21 can be adjusted according to the number of main grid lines designed. To ensure the reliability of the connection as a medium, the first conductive body 3 needs to completely fill the conductive pre-hole 21, and the height exceeds the surface 5 μm-10 μm of the back pre-solidification layer 2. This height difference design is the key to ensuring the reliability of the electrical connection. This is because the shape and height of the conductive pre-hole 21 after pre-solidification are fixed, and in the lamination process, the bismuth-containing low-temperature tin is in a softened state at the lamination temperature, and under the pressure of the second conductive body 4 (solder strip in this embodiment), the high part will be plastically deformed and flattened, and the fluidity can fill the small bumps and bumps on the surface of the solder strip (such as the rough surface of the copper base and the shape deviation of the foil), so that the two form a large area of close contact. In addition, the solder strip and the first conductive body 3 are compatible in composition (both contain low-temperature tin), and the flattened interface can realize low-resistance connection through metallurgical bonding. If the first conductive body 3 does not protrude from the pre-hole, the solder strip will move down after lamination, and it is easy to form a gap with the first conductive body 3, and the low-temperature tin is limited in softening degree, and it is difficult to fill the gap by itself, which ultimately leads to poor contact. Therefore, this height design is the key optimization to ensure that the solder strip and the first conductive body 3 realize reliable electrical connection during the lamination process.

[0072] In this embodiment, the second conductive body 4 is a solder strip, and the core structure takes copper as the base (to ensure high conductivity), and the surface is plated with a bismuth-containing low-temperature tin layer (such as tin bismuth lead, tin bismuth silver, and tin bismuth silver lead) consistent in composition with the first conductive body 3. Foil solder strip without plating layer can also be used. The shape is flexible, and flat solder strip can be selected to increase the contact area, or original wire solder strip can be used to adapt to different spatial layouts. The solder strip is directly arranged above the first conductive body 3 and precisely docks with the first conductive body 3 of the corresponding polarity. As shown in FIG. 2, the solder strip is arranged in the conductive pre-hole 21. Figure 4 As shown in FIG. 1, in the column direction, all the first conductive bodies 3 in communication with the positive fine grid are electrically connected with the same positive solder strip, and all the first conductive bodies 3 in communication with the negative fine grid are electrically connected with the same negative solder strip. After connection, the positive solder strip and the negative solder strip are alternately arranged along the first direction. Under this design, the holes collected by the positive fine grid flow into the positive solder strip through the first conductive body 3, and the electrons collected by the negative fine grid flow into the negative solder strip through the first conductive body 3, and finally form a closed loop to output current through the series and parallel connection of the solder strip. By using the metallurgical bonding characteristics of the solder strip and the first conductive body 3 with the same low-temperature tin, low-resistance and efficient current collection is realized.

[0073] As shown in FIG. 2, the solder strip is arranged in the conductive pre-hole 21. Figure 5As shown in the drawings, in the embodiment of the present application, the front surface of the battery piece 1 is also provided with a front surface pre-solidification layer 5, which forms a sandwich type protection structure with the back surface pre-solidification layer 2. The material of the front surface pre-solidification layer 5 is consistent with that of the back surface pre-solidification layer 2, both of which are organic silicone glue, and the thickness is controlled within 20-50 microns. The organic silicone glue has excellent high and low temperature resistance (stable within the temperature range of -50-200℃) and high Tg characteristics (Tg≥150℃), which are much better than those of traditional glue film (Tg is usually 80-100℃), and can maintain structural stability in long-term outdoor thermal cycling. The core function of the front surface pre-solidification layer 5 is to solve the process damage problem: in traditional packaging, the front surface of the battery piece 1 lacks protection and is easy to be scratched in handling and lamination processes, while the front surface pre-solidification layer 5 forms a dense film through pre-solidification, which can directly provide physical protection, and its light transmittance can reach more than 97% (higher than 91-93% of traditional EVA glue film), which almost does not affect light absorption. In addition, the relatively symmetrical design structure of the front surface pre-solidification layer 5 (without conductive pre-hole 21) and the back surface pre-solidification layer 2 can balance the stress on both sides of the battery piece 1, reduce the warping problem caused by uneven stress on one side, and experimental verification shows that the warping degree of the battery piece 1 in the traditional high-temperature welding scheme is usually more than 2mm / m, while the double-sided pre-solidification layer structure provided by the present application can control the warping degree within 0.5mm / m.

[0074] The photovoltaic module provided by the present application is also provided with a front surface packaging part 8 and a back surface packaging part 7 on the front surface and the back surface of the sandwich type protection structure. The front surface packaging part 8 includes a front surface packaging glue layer 81 and a front surface cover plate 82, and the back surface packaging part 7 includes a back surface packaging glue layer 71 and a back surface cover plate 72. Figure 6 As shown in the drawings, the front surface packaging glue layer 81 and the back surface packaging glue layer 71 bear the functions of overall sealing and structural bonding, and can select an organic silicone glue layer or a glue film (such as EVA, POE) according to the application scene. The organic silicone glue layer is suitable for scenes with high weather resistance requirements, and its high and low temperature resistance can ensure that the module works stably in an environment of -40-120℃, and the light transmittance is about 92-94%. The glue film has more advantages in light transmittance (such as POE glue film light transmittance 94-96%, EVA glue film 91-93%), and is suitable for scenes pursuing high power output. The thickness of the packaging glue layer is usually 0.3-0.5mm, which forms a functional partition with the pre-solidification layer-the pre-solidification layer is responsible for accurate protection and conductive connection, and the packaging glue layer is responsible for overall sealing, avoiding the functional conflict of traditional single glue film.

[0075] The front cover plate 82 is usually made of 3.2-4 mm thick super white tempered glass, and the surface is usually coated with an anti-reflection film (such as SiO2 / TiO2 multilayer film), with a light transmittance of ≥94% (the light transmittance of uncoated super white glass is about 91-92%). The front cover plate 82 not only protects the internal structure, but also reduces light reflection loss; the back cover plate 72 can be made of glass (double-glass assembly) or weather-resistant back plate (such as TPT, PET, suitable for conventional assemblies) according to requirements, providing mechanical support and water vapor barrier.

[0076] The edge of the assembly is coated with edge sealant 9 (such as butyl rubber), which further enhances the sealing performance. The edge sealant 9 is kept 1-2 mm away from the edges of the front and back encapsulation glue layers to avoid interference during lamination; the edge sealant 9 is 1-3 mm thick and 5-10 mm high, which can effectively block the intrusion of external water vapor and impurities, prevent the internal materials from being damp or contaminated, and thus delay the aging of the assembly. The edge sealant 9 is coated after the assembly is laminated, cured and cooled, and is uniformly coated along the edge of the assembly by a special coating equipment to ensure that it tightly fits the edges of the front cover plate 82 and the back cover plate 72.

[0077] The embodiment of the present application also provides a preparation method of the above-mentioned photovoltaic assembly. The preparation process of the photovoltaic assembly needs to accurately control the process parameters of each link to ensure the structural stability and electrical reliability, and the specific steps are as follows:

[0078] S1, applying organic silicone glue on the cell sheet 1 and pre-curing; wherein, the patterned organic silicone glue is applied on the back of the cell sheet 1 and pre-cured to form the back pre-cured layer 2, and the organic silicone glue is applied on the front of the cell sheet 1 and pre-cured to form the front pre-cured layer 5. The back pre-cured layer 2 has a plurality of arrayed conductive pre-holes 21, and each of the plurality of conductive pre-holes 21 corresponds to a positive fine grid and a negative fine grid on the back of the cell sheet 1.

[0079] Specifically, the preparation of each pre-cured layer is the core of the whole process. Preferably, the front pre-cured layer 5 and the back pre-cured layer 2 are formed at the same time. First, organic silicone glue is coated on the front and back of the cell sheet 1, the front silicone glue covers the entire front of the cell sheet 1, and the back silicone glue covers the area where the positive fine grid and the negative fine grid are located. Then, the cell sheet 1 coated with silicone glue is placed in a pre-curing mold 6 for compression pre-curing. Figure 5As shown in the figure, the mold is composed of an upper compression pre-curing mold 61 and a lower compression pre-curing mold 62. The upper compression pre-curing mold 61 is provided with a protruding structure matching the conductive pre-hole 21, i.e. a pre-hole filling mold 611, the protruding height of which is equal to the thickness of the back pre-curing layer 2 (20-50 μm), for forming the conductive pre-hole 21. The lower compression pre-curing mold 62 is flat, for ensuring the flatness of the front pre-curing layer 5. The working temperature of the mold is set to 80-120 °C, and the compression time is 5-10 seconds, so that the silicone glue reaches a curing degree of 60%-70%, which forms a stable pre-curing layer structure and retains certain adhesion, facilitating the subsequent combination with the encapsulation glue layer or the silicone glue layer used for encapsulation. In this process, the protrusion of the upper compression pre-curing mold 61 will press the conductive pre-hole 21 through the pre-curing layer in the back silicone glue, the position of which accurately corresponds to the positive and negative fine grids on the back of the battery sheet 1, ensuring the effective contact of the conductive body with the grid lines in the subsequent process.

[0080] S2, a first conductive body 3 is laid in the conductive pre-hole 21, and the height of the first conductive body 3 is higher than the surface of the back pre-curing layer 2.

[0081] Specifically, the laying of the first conductive body 3 needs to be carried out after the formation of the conductive pre-hole 21. The first conductive body 3 (such as bismuth-containing low-temperature tin) is filled into the hole by screen printing or dispensing process, ensuring complete filling without air bubbles. The height of the first conductive body 3 is controlled by a doctor blade or laser detection, so that it exceeds the surface of the back pre-curing layer 2 by 5-10 μm. Too high may cause hidden cracks of the battery sheet 1 during lamination, and too low may not guarantee reliable contact with the second conductive body 4. After filling, the first conductive body 3 is cured at 120-150 °C for 30-60 seconds, so that the first conductive body 3 forms a firm ohmic contact with the fine grid, while avoiding damage to the battery sheet 1 caused by high temperature. The curing temperature is much lower than the traditional high-temperature welding temperature, which can reduce the accumulation of thermal stress of the battery sheet 1.

[0082] S3, a second conductive body 4 is laid, so that the second conductive body 4 is electrically connected to the corresponding first conductive body 3.

[0083] Specifically, the connection of the second conductive body 4 needs to realize the convergence of the positive and positive, and the negative and negative. The second conductive body 4 in this embodiment is a solder strip, which is laid on the surface of the back pre-curing layer 2, and the alignment with the first conductive body 3 of the corresponding polarity is ensured by a visual positioning system.

[0084] The connection of the solder strip and the first conductive body 3 does not need an additional pre-welding process, and only through accurate positioning and laying, the preliminary butt joint is realized. Specifically, when laying the solder strip, it needs to be completely aligned with the first conductive body 3 of the corresponding polarity (deviation ≤0.1 mm), and the flatness and rigidity of the solder strip itself are used to maintain the preliminary contact with the first conductive body 3. During the subsequent lamination process, under the action of a lamination temperature of 130-150°C and a pressure of 0.1-0.3 MPa, the low-temperature tin plating layer on the surface of the solder strip will partially melt with the first conductive body 3 (containing bismuth low-temperature tin), and a metallurgical bond will be formed by using the compatibility of the material composition, and finally a low-resistance electrical connection is realized. This "pre-welding-free" connection relying on the lamination process can reduce the damage to the battery sheet 1 caused by additional thermal processes, and at the same time simplify the production process.

[0085] S4, forming a battery string.

[0086] The battery string is connected by a plurality of monomer battery sheets 1 through series welding. Specifically, the monomer battery sheets 1 are arranged at a predetermined interval, and the adjacent battery sheets 1 are connected through the cross-over solder strip: that is, the negative electrode solder strip of the previous battery sheet 1 and the positive electrode solder strip of the next battery sheet 1 are connected through the cross-over solder strip. The series welding process adopts a low-temperature welding process (welding temperature ≤180°C), and the local melting of the solder strip is realized through laser welding or infrared heating, so as to avoid the thermal damage to the battery sheet 1 caused by high temperature. After series welding, it is necessary to ensure that there is no false welding, missing welding, and no hidden cracks or fragments in the battery sheet 1.

[0087] S5, laying the encapsulation adhesive layer and the cover plate.

[0088] Specifically, the laying of the encapsulation adhesive layer and the cover plate needs to pretreat the cover plate first: the inner surfaces of the front cover plate 82 (super white glass) and the back cover plate 72 are coated with silicone glue or laid with adhesive film (such as POE), and are pre-cured (80-100°C, 10-20 seconds) to form a preliminary bonding layer. Then, in the order of "front cover plate 82→ front encapsulation adhesive layer 81→ battery string (having been provided with front pre-cured layer 5 and back pre-cured layer 2)→ back encapsulation adhesive layer 71→ back cover plate 72", the alignment of each layer is ensured through positioning tooling, and the edge deviation is ≤0.5 mm.

[0089] S6, laminating to form a photovoltaic module.

[0090] Specifically, laminating and edge sealing are the last steps of the assembly forming. The laminating machine is used to laminate the stacked structure at 130-150℃, 0.1-0.3MPa and ≤10Pa for 30-60 minutes. During the laminating process, the high temperature makes the encapsulation adhesive layer melt completely and fuse with the pre-solidification layer, the pressure ensures the tight combination of each layer, and the vacuum environment eliminates bubbles. After laminating, the assembly needs to be cooled naturally to below 60℃ to avoid internal stress caused by temperature difference. After cooling, the edges of the assembly are trimmed to remove the excess encapsulation adhesive layer and clean the edge surface. Finally, the edge sealing adhesive 9 (butyl adhesive) is applied to the edges of the assembly, and the special coating equipment is used to ensure the continuous and uniform adhesive line. After coating, the edge sealing adhesive 9 is allowed to cure for 2-4 hours to form a sealed edge, and the preparation of the photovoltaic assembly is completed.

[0091] The photovoltaic assembly and the preparation method thereof provided by the present application realize a plurality of technical breakthroughs through structural innovation and process optimization. Firstly, the symmetrical design of the front pre-solidification layer 5 and the back pre-solidification layer 2 balances the stress on both sides of the cell sheet 1, and the high Tg characteristic of the organic silicone adhesive makes the warpage of the assembly controlled within 0.5mm / m, solving the warpage problem of the traditional high-temperature welding. Secondly, the conductive pre-hole 21 of the back pre-solidification layer 2 precisely fills the first conductive body 3, avoiding the cavity defect of the traditional adhesive film. Thirdly, the combination of the front pre-solidification layer 5 (light transmittance >97%) and the high-transmittance encapsulation adhesive layer (such as POE adhesive film 94-96%) improves the overall light transmittance to >95%, and the power of the assembly is increased by 2-3% compared with the traditional EVA adhesive film scheme (91-93%). Fourthly, the physical protection of the front pre-solidification layer 5 greatly reduces the scratch rate of the cell sheet 1 during production, improving the appearance qualification rate.

[0092] 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 departing from the principles of the present application, and the technical solutions after the changes or replacements will 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 (82), a front encapsulating layer (81), a front pre-fixing layer (5), a cell (1), a back pre-fixing layer (2), a back encapsulating layer (71), and a back cover plate (72) stacked in sequence. The back of the cell (1) is provided with a positive electrode grid and a negative electrode grid. The back pre-fixing layer (2) forms a plurality of arrayed conductive pre-holes (21). Some of the conductive pre-holes (21) correspond to the positive electrode grid, and some of the conductive pre-holes (21) correspond to the negative electrode grid. A first conductor (3) is laid in the conductive pre-holes (21). The height of the first conductor (3) exceeds the surface of the back pre-fixing layer (2) and is electrically connected to a second conductor (4) so ​​that the photogenerated carriers collected by the positive electrode grid and the negative electrode grid can be output after being combined through the second conductor (4).

2. The photovoltaic module according to claim 1, characterized in that, The back pre-curing layer (2) is made of silicone.

3. The photovoltaic module according to claim 1, characterized in that, The depth of the conductive pre-hole (21) is the same as the thickness of the back pre-solidification layer (2).

4. The photovoltaic module according to claim 3, characterized in that, The thickness of the back pre-curing layer (2) is 20μm to 50μm.

5. The photovoltaic module according to claim 1, characterized in that, The height of the first conductor (3) is greater than the thickness of the back pre-reinforced layer (2).

6. The photovoltaic module according to claim 5, characterized in that, The difference between the height of the first conductor (3) and the thickness of the back pre-curing layer (2) is 5 μm to 10 μm.

7. The photovoltaic module according to claim 1, characterized in that, The material of the front pre-curing layer (5) is the same as that of the back pre-curing layer (2).

8. The photovoltaic module according to claim 1, characterized in that, The front encapsulation layer (81) is an organic silicone layer or film; and / or the back encapsulation layer (71) is an organic silicone layer or film.

9. The photovoltaic module according to any one of claims 1 to 8, characterized in that, The edges of the photovoltaic module are also sealed with edge-sealing adhesive (9).

10. The photovoltaic module according to claim 9, characterized in that, The distance between the edge sealing adhesive (9) and the edges of the front sealing adhesive layer (81) and the back sealing adhesive layer (71) is 1-2 mm; and / or the thickness of the edge sealing adhesive (9) is 1-3 mm and the height is 5-10 mm.

11. A method for preparing a photovoltaic module, characterized in that, The preparation method includes: applying silicone rubber to a solar cell (1) and pre-curing it; wherein, at least a patterned silicone rubber is applied to the back side of the solar cell (1) and pre-cured to form a back pre-curing layer (2), the back pre-curing layer (2) having a plurality of conductive pre-holes (21) arranged in an array, the plurality of conductive pre-holes (21) corresponding to the positive and negative grids on the back side of the solar cell (1); applying a first conductor (3) in the conductive pre-holes (21), the height of the first conductor (3) being higher than the surface of the back pre-curing layer (2); applying a second conductor (4) so ​​that the second conductor (4) is electrically connected to the corresponding first conductor (3); forming a battery string; applying an encapsulating adhesive layer and a cover plate; and laminating to form a photovoltaic module.

12. The method for preparing a photovoltaic module according to claim 11, characterized in that, The "applying silicone to the battery cell (1) and pre-curing it" also includes: applying silicone to the front side of the battery cell (1) and pre-curing it to form a front pre-curing layer (5).

13. The method for preparing a photovoltaic module according to claim 11, characterized in that, The depth of the conductive pre-hole (21) is the same as the thickness of the back pre-curing layer (2); and / or the thickness of the back pre-curing layer (2) is 20μm to 50μm; and / or the difference between the height of the first conductor (3) and the thickness of the back pre-curing layer (2) is 5μm to 10μm.

14. The method for preparing a photovoltaic module according to claim 11, characterized in that, The "applying of encapsulating adhesive layer and cover plate" includes: applying organic silicone to the cover plate and pre-curing it, wherein the cover plate includes a front cover plate (82) and a back cover plate (72).

15. The method for preparing a photovoltaic module according to claim 11, characterized in that, The encapsulating adhesive layer is an encapsulating adhesive film.

16. The method for preparing a photovoltaic module according to claim 12, characterized in that, The back pre-curing layer (2) and the front pre-curing layer (5) are formed by a pre-curing mold (6). The working temperature of the pre-curing mold (6) is 80-120°C and the pressing time is 5-10 seconds. The pre-curing mold (6) includes an upper pressing pre-curing mold (61). The upper pressing pre-curing mold (61) is provided with a protrusion structure that matches the conductive pre-hole (21). The protrusion height of the protrusion structure is equal to the thickness of the back pre-curing layer (2).

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