High-bifaciality bc photovoltaic module and preparation method and application thereof

Abstract

The present application relates to the field of photovoltaic cells, and more particularly to a high-bifacial BC photovoltaic module and a preparation method and application thereof. The high-bifacial BC photovoltaic module comprises, in sequence, a front glass layer, a front encapsulation adhesive film layer, a BC cell string layer, a back encapsulation adhesive film layer, a directional light condensing microlens array layer and a back plate layer; wherein the back surface of the BC cell string layer is provided with a plurality of non-electrode regions; the directional light condensing microlens array layer comprises a plurality of plano-convex lens structures; the plano-convex lens structures are arranged in the non-electrode regions; the plane side of the plano-convex lens structure faces the back plate layer, and the convex side of the plano-convex lens structure faces the back encapsulation adhesive film layer. The BC photovoltaic module has a high bifacial rate and strong back surface power generation capacity.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cells, and more specifically, to a high bifaciality BC photovoltaic module, its preparation method, and its application. Background Technology

[0002] Back-contact (BC) photovoltaic cells completely eliminate shading losses from the front-side metal grid lines by moving all positive and negative electrodes to the back of the cell, achieving higher front-side conversion efficiency and a more aesthetically pleasing appearance. This makes it one of the most promising high-efficiency technologies in the current photovoltaic industry. However, existing BC modules suffer from the following core technical shortcomings: (1) Low bifaciality and weak back-side power generation: Due to the large area of ​​metal electrodes and doped regions on the back of BC cells, the reflected light incident from the back cannot be effectively utilized. Currently, the bifaciality of mainstream BC modules in the industry is only 65%-75%, which is significantly lower than the 80%-85% of TOPCon modules. In scenarios with abundant reflected light, such as snow, desert, and water surfaces, the overall power generation capacity of BC modules is actually inferior to that of TOPCon modules.

[0003] (2) There is an irreconcilable contradiction between the back-side light utilization efficiency and the front-side efficiency: Existing technologies to improve the bifaciality of BC modules mainly focus on the cell end, such as reducing the width of p-type and n-type doped regions and using transparent conductive films to replace some metal electrodes. However, these technologies either increase carrier recombination losses and reduce the front-side conversion efficiency, or significantly increase manufacturing costs and process complexity, making it difficult to achieve large-scale mass production.

[0004] (3) Large component encapsulation loss: The existing BC module has a simple back-side encapsulation structure and has not been optimized for the propagation characteristics of back-side light. As a result, a large amount of back-side incident light is reflected or absorbed in the electrode area on the back of the battery and cannot participate in photoelectric conversion, resulting in serious optical loss.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] This invention addresses the core pain points of existing BC modules, namely low bifaciality and weak back-side power generation capability. It provides a high bifaciality BC photovoltaic module with an integrated back-side directional concentrating microlens array. Without altering the BC cell structure and manufacturing process, or affecting the front-side conversion efficiency, the directional concentrating microlens array, integrated into the back-side encapsulation layer, precisely focuses back-incident light onto the non-electrode area on the back of the cell, significantly improving the bifaciality and overall power generation capability of the BC module. Furthermore, this invention also solves the following technical problems: (1) How to design the structural parameters of the microlens array so that it can be precisely matched with the electrode pattern on the back of the BC battery to achieve maximum utilization of back light; (2) How to achieve compatibility between the microlens array and the existing BC component packaging process without increasing the additional process complexity and manufacturing cost.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A high bifaciality BC photovoltaic module includes: a front glass layer, a front encapsulating film layer, a BC cell string layer, a back encapsulating film layer, a directional concentrating microlens array layer, and a backsheet layer, which are stacked sequentially. The back side of the BC battery string layer has several non-electrode regions; the directional focusing microlens array layer includes several plano-convex lens structures; the plano-convex lens structures are disposed in the non-electrode regions; the planar side of the plano-convex lens structure faces the backplate layer, and the convex side of the plano-convex lens structure faces the back encapsulation film layer.

[0008] Preferably, the bottom diameter of the plano-convex lens structure is 20-80 μm smaller than the width of the non-electrode region.

[0009] Preferably, the focal length of the plano-convex lens structure is equal to the sum of the thickness of the back encapsulation film layer and the thickness of the directional focusing microlens array layer.

[0010] Preferably, the radius of curvature of the plano-convex lens structure is 150~200μm.

[0011] Preferably, the arrangement of the plano-convex lens structure includes an interdigitated arrangement.

[0012] Preferably, the material of the directional focusing microlens array layer includes: ethylene-vinyl acetate copolymer and / or polyolefin elastomer.

[0013] Preferably, the thickness of the directional focusing microlens array layer is 45~55μm.

[0014] Preferably, the BC battery string layer comprises: a plurality of BC battery cells connected in series by solder strips.

[0015] A method for preparing the high bifaciality BC photovoltaic module includes the following steps: (a) Laying out a front glass layer, a front encapsulation film layer, a BC battery string layer, a back encapsulation film layer, a directional focusing microlens array layer, and a backsheet layer to obtain a laminated component; (b) subjecting the laminated component to heat lamination treatment.

[0016] A photovoltaic cell includes: the aforementioned high bifaciality BC photovoltaic module.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly improve the bifaciality and back-side power generation capability of BC modules: By using a directional concentrating microlens array to precisely focus the light incident from the back side onto the non-electrode area on the back of the battery, the bifaciality of BC modules can be increased from the current 75% to over 85%, and the back-side power generation gain can be increased by 15%-20%. In scenarios with abundant reflected light, such as snow, desert, and water surfaces, the overall power generation capability can be increased by 8%-12%.

[0018] (2) It does not affect the positive conversion efficiency: The technical solution of the present invention is fully implemented at the component packaging level, without changing the structure and manufacturing process of the BC battery itself, so it will not have any negative impact on the positive conversion efficiency of the battery.

[0019] (3) Good process compatibility and low manufacturing cost: The microlens array is made of the same material as the back-side encapsulation film and can be mass-produced through roll forming process. Only one laying process needs to be added to the existing component encapsulation production line, which will not significantly increase the process complexity and manufacturing cost. According to calculations, the manufacturing cost per watt will only increase by about RMB 0.005 / W.

[0020] (4) High reliability and long service life: The microlens array and the back encapsulation film are made of the same material, which has good weather resistance and UV resistance, and can maintain stable optical performance in long-term outdoor environment without affecting the 25-year service life of the component.

[0021] (5) Perfect integration with existing BC technology of Gaojing: The technical solution of the present invention can be perfectly integrated with Gaojing Solar’s ​​existing BC2.0 technology (such as “I” type welding technology, OBB no main grid technology, copper electroplating technology, etc.) to form a differentiated competitive advantage and further enhance the market competitiveness of Gaojing BC modules. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the high bifaciality BC photovoltaic module provided by the present invention; Figure 2 This is a schematic diagram of the structure of the directional focusing microlens array layer provided by the present invention; Figure 3 A schematic diagram showing the correspondence between the back electrode pattern of the BC battery and the microlens array provided by the present invention; Figure 4This is a schematic diagram of the light-gathering principle of a single plano-convex lens structure provided by the present invention; Figure 5 This is a schematic diagram of the fabrication process of the directional focusing microlens array layer provided by the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] One aspect of the present invention relates to a high bifaciality BC photovoltaic module, such as Figure 1 As shown, it includes: a front glass layer, a front encapsulating film layer, a BC battery string layer, a back encapsulating film layer, a directional focusing microlens array layer, and a backplate layer, which are stacked in sequence. The back side of the BC battery string layer has several non-electrode regions; for example... Figure 2 and Figure 3 As shown, the directional focusing microlens array layer includes: a plurality of plano-convex lens structures; the plano-convex lens structures are disposed in the non-electrode region; The planar side of the plano-convex lens structure faces the backplate layer, and the convex side of the plano-convex lens structure faces the back encapsulation film layer.

[0026] The BC photovoltaic module, without altering the structure and manufacturing process of the BC cells themselves or affecting the front-side conversion efficiency, integrates a directional concentrating microlens array in the back-side encapsulation layer of the module to precisely focus back-incident light onto the non-electrode area on the back of the cell (e.g., ...). Figure 4 As shown in the figure, this significantly improves the bifaciality and overall power generation capacity of the BC module. Simultaneously, the structural parameters of the microlens array are precisely designed to ensure accurate matching with the electrode pattern on the back of the BC cell, maximizing back-side light utilization. The packaging and fabrication process of the microlens array is designed to be compatible with existing BC module packaging processes, without increasing additional process complexity or manufacturing costs.

[0027] The BC photovoltaic module integrates a directional focusing microlens array that precisely matches the pattern of the back electrode of the BC cell between the back encapsulation film and the backsheet. Figure 3As shown, the microlens array consists of multiple microlens units (plano-convex lens structures) that correspond one-to-one with the non-electrode areas on the back of the battery. It can accurately focus parallel light or diffuse light incident from the back onto the non-electrode areas on the back of the battery, thereby significantly improving the utilization efficiency of back light.

[0028] The precise matching design between the directional focusing microlens array layer and the back electrode pattern of the BC battery is the core of this invention for achieving efficient back-side light utilization. Based on the back electrode pattern of the BC battery (including the width, spacing, and arrangement of p-type and n-type doped regions), the unit size, focal length, and arrangement of the microlens array need to be precisely designed to ensure that the focused light spot falls entirely within the non-electrode area.

[0029] Furthermore, the BC battery string layer includes: a plurality of BC battery cells connected in series by solder strips.

[0030] Furthermore, the plano-convex lens structure is configured in a one-to-one correspondence with the non-electrode region.

[0031] Furthermore, the bottom diameter of the plano-convex lens structure is 20-80 μm smaller than the width of the non-electrode region, including but not limited to a point value or a range between any two of 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm. The bottom dimension of the plano-convex lens structure matches the dimension of the non-electrode region on the back of the BC battery, and is slightly smaller than the dimension of the non-electrode region, ensuring that the focused light spot falls entirely within the non-electrode region. For example, for the Gaojing Solar BC2.0 battery, the width of its back non-electrode region is approximately 150-200 μm, therefore the bottom diameter of the plano-convex lens structure is designed to be 120-180 μm.

[0032] Furthermore, the focal length of the plano-convex lens structure is equal to the sum of the thickness of the back encapsulation film layer and the thickness of the directional focusing microlens array layer. This focal length ensures that the light emitted from the microlens can be accurately focused on the back surface of the BC battery. For a conventional 300μm thick EVA encapsulation film and a 50μm thick microlens array layer, the focal length of the microlens unit is designed to be 350μm.

[0033] Furthermore, the radius of curvature of the plano-convex lens structure is 150~200μm, including but not limited to a point value or a range between any two of 150μm, 160μm, 170μm, 180μm, 190μm, or 200μm. The radius of curvature is calculated based on the focal length and the refractive index of the microlens material. For example, for EVA material with a refractive index of 1.5, the radius of curvature of a plano-convex lens with a focal length of 350μm is approximately 175μm.

[0034] The microlens of this invention is a single-sided plano-convex lens: the planar side is attached to the back plate, the convex side faces the film / battery, the working medium is the EVA / POE encapsulation film (the refractive index is uniformly denoted as n), air only exists on the outside of the back plate, the refractive index inside the lens is almost the same as that of the encapsulation film, and the single spherical refractive focal length formula is adopted (simplified for thin lenses).

[0035] Core formula: The formula for the focal length of a thin lens in the same medium is: f = R / (n-1). Symbol definition: f: Microlens focal length (unit μm); R: Radius of curvature of the convex spherical surface (unit: μm); n: Refractive index of the lens material EVA / POE, industry standard n=1.50.

[0036] Given the design objective: As determined above, the total optical path distance = back film thickness 300μm + microlens film total thickness 50μm = 350μm. Therefore, the focal length of the microlens design must be f=350μm to ensure that the light is just focused on the back of the BC battery.

[0037] Complete substitution calculation process Given: f = 350 μm, n = 1.50, The radius of curvature R is calculated using the transformation formula: R = f * (n-1); R = 350 * (1.50 - 1) = 175 μm; Conclusion: The radius of curvature of the convex surface of the microlens is R = 175 μm.

[0038] The height of the lens spherical cap is determined from the radius of curvature (related to a 50μm thin film thickness). In the patent, the bottom aperture of the microlens unit is D=150μm (matching the width of the non-electrode region of the BC battery, which is 120~180μm, taking the middle value of 150μm). Formula for calculating the height h of a spherical cap: ; Given R = 175 micrometers and the half-width of the aperture D / 2 = 75 micrometers, the calculated height h of the spherical cap is approximately 16.89 μm.

[0039] The formula for a medium-thickness lens in air cannot be used: the lens is made of EVA / POE at both the top and bottom, the refractive index of the medium is consistent, there is no air interface refraction interference, and the formula for a thin single spherical lens perfectly fits the internal optical path of the component. The focal length must be equal to the total thickness of the film and lens: parallel incident light from the back enters the lens perpendicularly to the back plate and propagates along the optical axis. Only when the focal length is equal to the optical path distance can the light spot accurately fall on the non-electrode area on the back of the battery. The radius of curvature directly constrains the height of the lens protrusion, which in turn determines the total thickness of the microlens film, which is 50 μm. This forms a closed-loop linkage parameter system, which is the core distinguishing technical feature that differentiates it from existing front-facing microlens assemblies.

[0040] The microlens of this invention adopts a plano-convex lens structure, with POE or EVA as the lens material and a refractive index n ranging from 1.48 to 1.52, preferably 1.50. Based on the focal length formula of a thin lens in the same medium, f=R / (n-1), where f is the focal length of the microlens, it is set to 350μm, which is the sum of the thickness of the back-side encapsulation film and the thickness of the microlens array layer. The radius of curvature R of the convex surface of the microlens is calculated to be preferably 175μm. Combined with the bottom diameter of the microlens unit of 150μm, the theoretical height of the lens spherical cap is calculated to be approximately 16.89μm through spherical geometry. Considering the mold processing tolerance and lamination compression, the protrusion height of the microlens is set to 20μm in engineering, matching a 30μm planar substrate, so that the total thickness of the microlens array layer is controlled to 50μm, achieving precise focusing of the incident light from the back to the unobstructed area on the back of the BC battery. When the refractive index of the material fluctuates in the range of 1.48 to 1.52, the radius of curvature can be adjusted to 168 to 182 μm to achieve an effective light-gathering effect.

[0041] Furthermore, the plano-convex lens structure is arranged in an interdigitated pattern. Using the same interdigitated pattern as the rear electrode pattern of the BC battery, the spacing between the plano-convex lens structures matches the width of the rear electrode area of ​​the BC battery, ensuring that the microlens units do not cover the electrode area.

[0042] Furthermore, the material of the directional focusing microlens array layer includes ethylene-vinyl acetate copolymer and / or polyolefin elastomer. The directional focusing microlens array is fabricated using the same EVA or POE material as the back-side encapsulating film. This ensures good adhesion and optical matching between the microlens array and the back-side encapsulating film, avoiding interface reflection loss. By optimizing the formulation of the EVA or POE material, the transmittance and refractive index of the directional focusing microlens array layer can be improved, while ensuring its weather resistance and UV resistance, thus ensuring the stable optical performance of the microlens array in long-term outdoor environments.

[0043] Furthermore, the thickness of the directional focusing microlens array layer is 45~55μm.

[0044] The directional focusing microlens array layer consists of multiple microlens units arranged periodically. Each microlens unit is a plano-convex lens structure, with its planar side facing the backplate layer and its convex side facing the back encapsulation film layer.

[0045] In some specific embodiments, the total thickness of the directional focusing microlens array layer is 50 μm, of which the thickness of the thin-film planar substrate is 30 μm and the height of the spherical crown protrusion of the microlens unit is 20 μm. The microlens array layer is made of high-transmittance POE or EVA with a refractive index of 1.48–1.52. The focal length of the microlens unit is designed to be equal to the sum of the thickness of the back-side encapsulating film and the thickness of the microlens array layer, i.e., 350 μm, so that the diffusely reflected light incident from the back panel side is precisely focused onto the non-electrode area on the back of the BC cell without metal obstruction after refraction by the microlens. The thickness of the microlens array layer is controlled in the range of 45–55 μm. Under the premise of meeting the optical focusing performance, it is compatible with the existing photovoltaic module lamination process, avoids the collapse of the microlens structure under high temperature and pressure, and controls the incremental cost of auxiliary materials, while taking into account both mass production yield and long-term weather resistance reliability of the module.

[0046] Another aspect of the present invention relates to a method for preparing the aforementioned high bifaciality BC photovoltaic module, comprising the following steps: (a) Laying out a front glass layer, a front encapsulation film layer, a BC battery string layer, a back encapsulation film layer, a directional focusing microlens array layer and a backsheet layer to obtain a laminated component; (b) The laminated parts are subjected to heat lamination to make the materials of each layer bond together tightly.

[0047] The encapsulation process of the high bifaciality BC photovoltaic module is basically the same as that of the conventional BC module encapsulation process. It only requires an additional step of laying an oriented concentrating microlens array layer after laying the back encapsulation film layer.

[0048] When laying the oriented focusing microlens array layer on the back encapsulation film layer, it is necessary to ensure that the pattern of the oriented focusing microlens array layer is precisely aligned with the electrode pattern on the back of the BC battery.

[0049] Furthermore, the method for fabricating the directional focusing microlens array layer is as follows: Figure 5 As shown, it includes the following steps: A metal roller mold with a concave pattern of microlens array is prepared, the pattern of which is precisely matched with the non-electrode area pattern on the back of the BC battery; molten EVA and / or POE are extruded to form a continuous film; the extruded film is rolled through a metal roller with a microlens array pattern to form a microlens array structure on one side of the film; the formed microlens array film is cooled and shaped to obtain the directional focusing microlens array layer.

[0050] The roll forming process for directional focusing microlens array layers requires the development of high-precision metal roller mold preparation technology and roll forming process to ensure the shape accuracy and dimensional consistency of the microlens array, while ensuring production efficiency and yield.

[0051] During the component packaging process, it is necessary to ensure that the pattern of the microlens array is precisely aligned with the position of the BC battery string, with an alignment accuracy requirement within ±20μm. Automatic alignment can be achieved using a machine vision positioning system.

[0052] Furthermore, the method for preparing the high bifaciality BC photovoltaic module further includes: Step (c) involves trimming, framing, and installing the junction box to obtain the finished component.

[0053] Another aspect of the present invention relates to a photovoltaic cell, comprising: a high bifaciality BC photovoltaic module.

[0054] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0055] Example 1 The high bifaciality BC photovoltaic module provided in this embodiment includes: a front glass layer, a front encapsulating film layer, a BC cell string layer, a back encapsulating film layer, a directional concentrating microlens array layer, and a backsheet layer stacked sequentially. The back of the BC battery string layer has several non-electrode areas; the directional focusing microlens array layer includes several plano-convex lens structures; the plano-convex lens structures are set in the non-electrode areas of the BC battery string layer, and the two correspond one-to-one; the planar side of the plano-convex lens structure faces the backplate layer, and the convex side of the plano-convex lens structure faces the back encapsulation film layer. The bottom diameter of the plano-convex lens structure is 50 μm smaller than the width of the non-electrode region; The focal length of the plano-convex lens structure is equal to the sum of the thickness of the back encapsulation film layer and the thickness of the directional focusing microlens array layer; The radius of curvature of the plano-convex lens structure is 180 μm; The arrangement of plano-convex lens structures includes: interdigitated arrangement; The materials of the directional focusing microlens array layer include: ethylene-vinyl acetate copolymer; The thickness of the directional focusing microlens array layer is 50 μm; The BC battery string layer consists of several BC battery cells connected in series by solder strips.

[0056] The preparation method includes the following steps: (a) Laying out a front glass layer, a front encapsulation film layer, a BC battery string layer, a back encapsulation film layer, a directional focusing microlens array layer and a backsheet layer to obtain a laminated component; (b) The laminated parts are subjected to heat lamination.

[0057] Example 2 This embodiment has a basically the same structure as Embodiment 1, with the following differences: The bottom diameter of the plano-convex lens structure is 20 μm smaller than the width of the non-electrode region; The radius of curvature of the plano-convex lens structure is 150 μm; The materials of the directional focusing microlens array layer include: polyolefin elastomer; The thickness of the directional focusing microlens array layer is 55 μm.

[0058] The preparation method is the same as in Example 1.

[0059] Example 3 This embodiment has a basically the same structure as Embodiment 1, with the following differences: The bottom diameter of the plano-convex lens structure is 80 μm smaller than the width of the non-electrode region; The radius of curvature of the plano-convex lens structure is 200 μm; The thickness of the directional focusing microlens array layer is 45 μm.

[0060] The preparation method is the same as in Example 1.

[0061] Comparative Example 1 The only difference between this comparative example and Example 1 is that the directional focusing microlens array layer is not provided.

[0062] Experimental Example The photovoltaic modules prepared in Examples 1-3 and Comparative Example 1 were subjected to multi-dimensional performance comparison tests using uniform equipment and standards. All tested modules used the same batch of BC cells, the same front glass, and a 300μm thick back encapsulating film. The lamination process parameters were completely identical, with the only difference being the microlens array layer structure, parameters, and material. Single-variable comparison ensured the objectivity of the experiment. Five modules were prepared for parallel testing of each sample group, and the arithmetic mean was taken as the final test data. The test method is as follows: Bifaciality test: In accordance with the GB / T 39753-2021 bifacial photovoltaic module testing standard, a dual-source IV tester was used to collect the maximum power of the front side of the module under standard irradiance of 1000W / m² and the power generation of the back side under diffuse reflection irradiance of 200W / m². The bifaciality of the module was calculated to characterize the module's ability to utilize the reflected light from the back side.

[0063] Outdoor high-reflectivity scenario power generation test: A unified outdoor test platform was built, and aluminum foil with a reflectivity of 85% was laid on the bottom of the components to simulate the high-reflectivity conditions of snow. The ambient temperature was 25℃ and the installation tilt angle was 30°. The cumulative power generation of each component was collected in real time for 72 consecutive hours. The power generation gain rate of each embodiment was calculated based on the power generation of Comparative Example 1 to verify the actual power generation improvement effect.

[0064] Backside optical loss test: A parallel visible light source is used to incident from the backside of the module. A CCD microscopic imaging system is used to collect the illumination distribution on the backside of the BC cell. The light energy density of the electrode metal area and the non-electrode active area is collected by the optical power detector. The proportion of light energy lost due to being blocked by the metal electrode is calculated to characterize the mechanism by which the microlens directs the light to improve optical loss.

[0065] DH1000 Damp Heat Reliability Test: Damp heat aging tests were conducted at 85℃, 85RH, and 1000h according to IEC 61215 standard. The output power attenuation, interlayer peel strength, and microlens transmittance attenuation of the component before and after aging were tested to evaluate the long-term outdoor adaptability reliability of the microlens array layer and the packaging system.

[0066] Five components were tested in parallel for each sample group, and the arithmetic mean was taken. All samples used the same 182mm BC battery, 300μm backing adhesive, and lamination process.

[0067] Table 1

[0068] In conventional BC modules, a large amount of reflected light from the back is blocked by the back metal electrode, resulting in low bifaciality and power generation, and significant power loss in snow-covered conditions. This invention adds a directional focusing microlens array that corresponds one-to-one with the non-electrode area of ​​the battery, focusing the back light onto the unobstructed active area, increasing the bifaciality by 14.7 percentage points, increasing power generation in high-reflection scenarios by over 11%, and accelerating snow melting.

[0069] The difference in width between the bottom surface of the microlens and the non-electrode area, the radius of curvature, the film thickness, and the encapsulation material form a synergistic constraint. Existing technologies for improving the bifaciality of BC cells all require modifications to the doping and electrode patterns of the BC cells, sacrificing front-side efficiency and increasing battery manufacturing costs while improving bifaciality. This invention only adds an ultra-thin microlens film to the module encapsulation layer, without changing the battery structure, with a cost increase of only 0.005 yuan / W, while simultaneously achieving four major benefits: improved bifaciality, high-reflectivity power generation gain, enhanced efficiency in extreme cold snow melting, and unchanged reliability. This multi-dimensional simultaneous optimization achieves unexpected technical results.

[0070] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high bifaciality BC photovoltaic module, characterized in that, include: The front glass layer, the front encapsulating film layer, the BC battery string layer, the back encapsulating film layer, the directional focusing microlens array layer, and the backplate layer are stacked in sequence. The back side of the BC battery string layer has several non-electrode regions; the directional focusing microlens array layer includes several plano-convex lens structures; the plano-convex lens structures are disposed in the non-electrode regions. The planar side of the plano-convex lens structure faces the backplate layer, and the convex side of the plano-convex lens structure faces the back encapsulation film layer.

2. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The bottom diameter of the plano-convex lens structure is 20-80 μm smaller than the width of the non-electrode region.

3. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The focal length of the plano-convex lens structure is equal to the sum of the thickness of the back-side encapsulating film layer and the thickness of the directional focusing microlens array layer.

4. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The radius of curvature of the plano-convex lens structure is 150~200μm.

5. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The arrangement of the plano-convex lens structure includes: interdigitated arrangement.

6. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The material of the directional focusing microlens array layer includes: ethylene-vinyl acetate copolymer and / or polyolefin elastomer.

7. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The thickness of the directional focusing microlens array layer is 45~55μm.

8. The high bifaciality BC photovoltaic module according to claim 1, characterized in that, The BC battery string layer includes: a plurality of BC battery cells connected in series by solder strips.

9. The method for preparing a high bifaciality BC photovoltaic module according to any one of claims 1 to 8, characterized in that, Includes the following steps: (a) Laying out a front glass layer, a front encapsulation film layer, a BC battery string layer, a back encapsulation film layer, a directional focusing microlens array layer and a backsheet layer to obtain a laminated component; (b) The laminated parts are subjected to heat lamination.

10. A photovoltaic cell, characterized in that, include: The high bifaciality BC photovoltaic module according to any one of claims 1 to 8.

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