Photovoltaic cell packaging structure with improved weather resistance and heat dissipation efficiency and preparation method thereof

Abstract

This invention provides a photovoltaic cell encapsulation structure and preparation method for improving weather resistance and heat dissipation efficiency. The photovoltaic cell encapsulation structure includes at least: a photovoltaic cell layer; a first encapsulation layer disposed on the light-receiving side of the photovoltaic cell layer, the first encapsulation layer containing a chemically bonded compound of organosilicon resin and nano-silica; and a second encapsulation layer disposed on the backlight side of the photovoltaic cell layer, the second encapsulation layer containing a blend of a polymer matrix and a thermally conductive filler. This invention achieves significant results in extending module lifespan, improving heat dissipation performance, and maintaining process compatibility through a dual-layer functional design of "weather resistance on top and thermal conductivity on the bottom."

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a photovoltaic cell packaging structure and preparation method for improving weather resistance and heat dissipation efficiency. Background Technology

[0002] As the core component of a solar power generation system, the encapsulation structure of photovoltaic modules directly determines their power generation efficiency, long-term reliability, and service life. Currently, the encapsulation structure of photovoltaic modules generally adopts a stacked form of "cover plate (ultra-white tempered glass) - encapsulating film - photovoltaic cell array - encapsulating film - backsheet". Among them, the encapsulating film is mainly made of ethylene-vinyl acetate copolymer (EVA), and polyolefin elastomer (POE) is also used. However, these encapsulation materials have significant limitations in terms of weather resistance and heat dissipation.

[0003] During long-term outdoor use, EVA film is easily affected by changes in ultraviolet radiation, humidity, and temperature, resulting in yellowing, decreased cross-linking degree, and weakened adhesion, leading to reduced light transmittance and shortened module life. POE film is superior to EVA in some weather resistance properties, but its long-term resistance to ultraviolet aging is still insufficient, making it difficult to fully meet the long-life requirements of high-efficiency batteries for encapsulation materials.

[0004] Meanwhile, traditional encapsulating films generally have low thermal conductivity. The thermal conductivity of EVA and POE is usually between 0.2 and 0.3 W / (m·K), which makes it difficult to effectively dissipate the heat generated by the solar cells during operation. This results in the solar cells operating at a temperature 20 to 30°C higher than the ambient temperature. As a result, the efficiency of photovoltaic cells decreases with increasing temperature. For every 1°C increase in temperature, the conversion efficiency will decrease by 0.3% to 0.5%. Under extreme high temperatures (such as when the surface temperature of photovoltaic modules is above 70°C in summer), the conversion efficiency can decrease by 15% or more.

[0005] In summary, existing packaging solutions are insufficient to balance long-term weather resistance and efficient heat dissipation. There is an urgent need for a photovoltaic cell packaging structure that can improve both weather resistance and heat dissipation efficiency, thereby enhancing the overall performance of photovoltaic modules. Summary of the Invention

[0006] The purpose of this invention is to provide a photovoltaic cell encapsulation structure and preparation method that improves weather resistance and heat dissipation efficiency, so as to solve the problems in the background art.

[0007] The technical solution adopted in this invention includes: a photovoltaic cell encapsulation structure that improves weather resistance and heat dissipation efficiency, comprising at least:

[0008] Photovoltaic cell layer;

[0009] A first encapsulation layer is disposed on the light-receiving side of the photovoltaic cell layer, and the first encapsulation layer contains a chemical bond of organosilicon resin and nano-silica.

[0010] A second encapsulation layer is disposed on the backlight side of the photovoltaic cell layer, the second encapsulation layer containing a blend of polymer matrix and thermally conductive filler.

[0011] Preferably, the mass ratio of organosilicon resin to nano-silica is (85~95):(5~15).

[0012] Preferably, the silicone resin is an A / B two-component addition-type RTV silicone, where component A is vinyl-terminated polydimethylsiloxane and component B is hydrogen-containing silicone oil. The silicone resin has a transmittance of ≥94% in the 400nm~1100nm wavelength range and a refractive index of 1.41~1.43.

[0013] Preferably, the thickness of the first encapsulation layer is 0.6 mm to 1.0 mm.

[0014] Preferably, the thermally conductive filler accounts for 8% to 20% of the volume in the blend, and includes at least aluminum nitride particles with a particle size of 1 μm to 5 μm.

[0015] Preferably, the polymer matrix includes at least POE.

[0016] Preferably, the thickness of the second encapsulation layer is 0.8mm to 1.2mm.

[0017] The technical solution of the present invention also includes: a method for preparing the above-mentioned photovoltaic cell packaging structure with improved weather resistance and heat dissipation efficiency, which includes the following steps:

[0018] Organosilicon resin and nano-silica are mixed in a certain proportion, a coupling agent is added, and a hybridization reaction is carried out to obtain a chemically bonded slurry.

[0019] The polymer matrix and thermally conductive filler are mixed in a certain proportion and then thermally processed to obtain a blend preform film.

[0020] The photovoltaic cell encapsulation structure is obtained by stacking and laminating the cover plate, chemical bond slurry, photovoltaic cell layer, blend preform film and back sheet in that order, so that the chemical bond slurry is bonded and cured to form the first encapsulation layer, and the blend preform film is bonded to form the second encapsulation layer.

[0021] Preferably, the coupling agent accounts for 0.5% of the total mass of the organosilicon resin and nano-silica.

[0022] Preferably, during lamination, the temperature is 120℃, the pressure is 0.8MPa, and the time is 15min.

[0023] The beneficial effects of this invention include: Addressing the common problems of poor weather resistance and insufficient heat dissipation in traditional photovoltaic cell encapsulation structures, this invention achieves comprehensive improvement through an integrated "weather resistance upper layer and thermal conductivity lower layer" design. The chemical bonding between silicone resin and nano-silica in the first encapsulation layer significantly enhances the module's resistance to ultraviolet aging and interface durability, extending the overall lifespan of the module to over 20 years, matching the long-term reliability requirements of high-efficiency cells. The high thermal conductivity composite system in the second encapsulation layer increases the thermal conductivity to 5-10 times that of traditional EVA films, reducing the cell operating temperature by 10-15°C, corresponding to a 3%-7.5% increase in power generation efficiency and an approximately 5% increase in annual power generation, effectively suppressing efficiency degradation caused by module temperature rise. This invention, through synergistic material and structural design, resolves the technical contradiction of simultaneously achieving both weather resistance and heat dissipation while remaining compatible with existing processes. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0025] This invention provides a photovoltaic cell encapsulation structure and preparation method that improves weather resistance and heat dissipation efficiency. In order to fully disclose this invention and facilitate a clear and concise introduction of its technical solution, the following description will focus on the preparation method and combine it with the product structural features to provide a detailed description of the embodiments of this invention.

[0026] The photovoltaic cell encapsulation structure provided in this embodiment of the invention includes a cover plate, a first encapsulation layer, a photovoltaic cell layer, a second encapsulation layer, and a backplate stacked along the thickness direction. The photovoltaic cell layer is an array of at least 20 high-efficiency heterojunction photovoltaic cells connected in series and parallel. The cell size is preferably 166mm × 166mm, with a gap of 0.5mm to 1mm between adjacent cells to avoid inter-cell compression due to thermal expansion. The materials of the cover plate and backplate can be selected according to conventional methods in the art; for example, the cover plate can be made of ultra-white tempered glass, and the backplate can be made of TPT, etc. The specific selection does not affect the implementation of the technical solution of this invention and is not further limited here. The first encapsulation layer is located on the light-receiving side of the photovoltaic cell layer and contains a chemically bonded compound of organosilicon resin and nano-silica. The second encapsulation layer is located on the backlight side of the photovoltaic cell layer and contains a blend of a polymer matrix and a thermally conductive filler.

[0027] This invention employs a composite structure design with different functional encapsulation layers on the light-receiving and backlighting sides of the battery. Without altering existing mainstream processes, it synergistically optimizes weather resistance and heat dissipation performance. Specifically, by constructing a chemical bonding system of organosilicon resin and nano-silica in the first encapsulation layer, the weather resistance of the photovoltaic module is significantly improved, extending its service life. By introducing thermally conductive fillers in the second encapsulation layer, the heat dissipation performance of the photovoltaic module is greatly enhanced. By reducing the battery operating temperature, the degradation of photovoltaic conversion efficiency is avoided, providing a comprehensive and reliable encapsulation solution for high-efficiency photovoltaic modules.

[0028] The fabrication method of the above-mentioned photovoltaic cell encapsulation structure includes the following steps:

[0029] (1) Mix organosilicon resin and nano-silica in proportion, add coupling agent, and hybridize to obtain chemically bonded slurry.

[0030] Organosilicon resin itself has certain resistance to ultraviolet aging and high light transmittance. This step, by adding nano-silica and coupling agent, can further improve the weather resistance and mechanical properties of the material. Specifically, the hydrolyzable siloxane groups of the coupling agent condense with the hydroxyl groups on the surface of nano-silica to form Si-O-Si bonds. At the same time, the organic functional groups of the coupling agent react with the active groups on the molecular chain of organosilicon resin to form covalent bonds or strong hydrogen bonds. Through the above chemical bonding, a stable chemical bridge is established between the inorganic phase and the organic phase, forming a chemical hybrid structure with synergistic performance enhancement.

[0031] This chemical hybrid structure brings about multiple performance improvements: First, the silica is uniformly dispersed and chemically anchored, effectively transferring stress through Si-O-Si bonds, thus improving the tensile strength, toughness, and wear resistance of the material. In addition, multiple tight chemical bonds fill the interfacial voids between the organic and inorganic phases, significantly enhancing the material's ability to block moisture and ultraviolet rays, thereby synergistically improving the material's resistance to damp heat aging and ultraviolet aging. Furthermore, the aforementioned chemical bridging significantly increases the contact area at the interface between the two phases, not only adding interfacial coordination effects but also enhancing van der Waals forces, making the thermal expansion behavior of the two phases more coordinated, improving the material's dimensional stability, and greatly enhancing the adhesion to the photovoltaic cell layer, effectively suppressing problems such as delamination and edge lifting caused by thermal mismatch.

[0032] Preferably, the mass ratio of organosilicon resin to nano-silica is (85~95):(5~15). This ratio range has been experimentally verified to maintain a comprehensive balance between the optical, mechanical and process properties of the composite system while achieving multiple functions such as mechanical reinforcement, environmental barrier and interface bonding.

[0033] When the proportion of nano-silica is less than 5%, its volume as a reinforcing and barrier phase is insufficient, making it difficult to effectively improve the mechanical strength of the material and unable to form a dense shielding network to block water vapor and ultraviolet rays, resulting in limited improvement on the material's weather resistance. When the proportion of nano-silica is higher than 15%, the high content of nano-silica will significantly increase the scattering and reflection of light by the material, directly leading to a decrease in light transmittance and photoelectric conversion efficiency. At the same time, the high content of nano-silica is more likely to agglomerate, and the agglomerates formed will become stress defects inside the material, exacerbating brittleness and reducing toughness. In addition, the high content of nano-silica will also increase the viscosity of the system, posing challenges to coating, molding and other processing technologies, and increasing production costs.

[0034] Preferably, the silicone resin is an A / B two-component addition-curing RTV silicone resin, where component A is vinyl-terminated polydimethylsiloxane and component B is hydrogen-containing silicone oil. The silicone resin has a transmittance ≥94% in the 400nm~1100nm wavelength range and a refractive index of 1.41~1.43, such as Wacker SOLAR 2202 silicone resin. The advantages of using this type of silicone resin are: the addition-curing mechanism ensures no by-products and low shrinkage, guaranteeing dimensional stability and interface reliability; high transmittance and moderate refractive index can effectively reduce light loss and optimize interface light matching, which is beneficial to improving module efficiency; at the same time, its inherent weather resistance and regular cross-linked network are synergistically enhanced after chemical bonding with nano-silica, so that the first encapsulation layer not only has good optical performance, but also achieves comprehensive improvement in mechanical, barrier and adhesive properties, thus providing a core guarantee for the long-term reliability of the module.

[0035] During implementation, the amount of coupling agent added accounts for 0.5% of the total mass of organosilicon resin and nano-silica. The coupling agent is a silane coupling agent, such as γ-aminopropyltriethoxysilane (KH-550). The amino group at one end of its molecule can form a strong hydrogen bond with polar groups such as hydroxyl groups in organosilicon resin, while the hydrolyzable ethoxy group at the other end undergoes a condensation reaction with the hydroxyl groups on the surface of nano-silica to form Si-O-Si bonds, thereby establishing a chemical bridge between the inorganic and organic phases. Alternatively, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) can undergo a ring-opening reaction with the epoxy group at one end of its molecule to form a covalent bond with the active hydrogen (such as hydroxyl and amino groups) in organosilicon resin, while the hydrolyzable methoxy group at the other end undergoes a condensation reaction with the hydroxyl groups on the surface of nano-silica to form Si-O-Si bonds, thereby achieving a chemical bridge between the inorganic and organic phases. The above-mentioned hybridization reaction is carried out under heating conditions, and the preferred reaction temperature is 80~120℃. The setting of this temperature range is a well-known technical common sense in the field for hybridization reactions based on the selected material system, and can be optimized according to actual process requirements.

[0036] (2) The polymer matrix and thermally conductive filler are mixed in proportion and thermally processed to obtain a preformed blend film.

[0037] Preferably, the thermally conductive filler is aluminum nitride particles with a particle size of 1μm to 5μm, accounting for 8% to 20% of the volume in the blend, and the polymer matrix is ​​polyolefin elastomer (POE). This preferred scheme, through the synergistic design of materials and parameters, enables the second encapsulation layer to simultaneously achieve efficient heat dissipation, reliable adhesion, and long-term stability: the aluminum nitride particles with a suitable particle size, at the aforementioned volume ratio, are easily dispersed in POE and form an effective thermally conductive network, significantly increasing the thermal conductivity of the second encapsulation layer to 1.5 to 3.0 W / (m·K); the good flexibility, adhesion, and inherent aging resistance and moisture barrier properties of POE, when compatible with this proportion of thermally conductive filler, ensure the processing feasibility of the blend preform film, the interfacial bonding strength after lamination, and long-term environmental reliability. Thus, the second encapsulation layer, with POE as the matrix, constructs a stable structure with high thermal conductivity, forming an integrated encapsulation system of "weather-resistant upper layer and thermally conductive lower layer" together with the aforementioned first encapsulation layer.

[0038] (3) Stack and laminate the cover plate, chemical bond slurry, photovoltaic cell layer, blend preformed film and back plate in sequence, so that the chemical bond slurry is bonded and cured to form the first encapsulation layer, and the blend preformed film is bonded to form the second encapsulation layer, thus obtaining the photovoltaic cell encapsulation structure.

[0039] Preferably, the lamination temperature is 120℃, the pressure is 0.8MPa, the time is 15min, the design thickness of the first encapsulation layer is 0.6mm~1.0mm, and the design thickness of the second encapsulation layer is 0.8mm~1.2mm.

[0040] This preferred solution, through matching lamination parameters and structural design, simultaneously achieves the curing and interfacial bonding of two functional materials under mild conditions, ensuring that the first encapsulation layer is fully cross-linked and the second encapsulation layer is tightly bonded, while avoiding excessive thermal stress damage; the thickness range setting takes into account the protection effect, heat conduction path and component lightweight requirements, optimizing production efficiency and overall cost while ensuring long-term reliability.

[0041] The following are specific embodiments of the present invention.

[0042] Example 1

[0043] (1) Preparation of photovoltaic cell layer: Select 60 heterojunction photovoltaic cells with a size of 166mm×166mm, and interconnect them in a 5-string 12-parallel manner to form a photovoltaic cell layer, with a 0.8mm gap between adjacent cells; use anhydrous ethanol to clean the grid line surface of the cells to remove oil and oxide layer, and set aside for later use.

[0044] (2) Preparation of the slurry for the first encapsulation layer: Mix Wacker SOLAR 2202 type silicone resin and nano silica at a mass ratio of 9:1, add coupling agent KH-550 accounting for 0.5% of the total mass of the two, stir in a disperser at a speed of 3000 rpm for 30 min, and the reaction temperature is 80~120℃ to allow the components to fully react and disperse, forming a uniform and stable chemical bond slurry.

[0045] (3) Preparation of the preformed film of the second encapsulation layer: POE particles and aluminum nitride particles are mixed at a volume ratio of 9:1 and extruded into a preformed film of 1.0 mm thickness by a twin-screw extruder at a temperature of 160~180℃;

[0046] (4) Integrated packaging: 3.2mm thick ultra-white tempered glass (cover plate), chemical bonding slurry obtained in step (2), photovoltaic cell layer obtained in step (1), blend preform film obtained in step (3), and TPT (back sheet) are stacked and laminated in a laminator in sequence. The lamination process parameters are set as follows: temperature 120℃, pressure 0.8MPa, time 15min.

[0047] During the lamination process, the chemically bonded slurry is heated and cured to form a first encapsulation layer with a thickness of 0.8 mm; at the same time, the blend preformed film is heated and softened, and tightly bonded to the photovoltaic cell layer and backsheet to form a second encapsulation layer with a thickness of 1.0 mm, resulting in a photovoltaic cell encapsulation structure with a thickness of 3.4 mm.

[0048] Example 2

[0049] The only difference from Example 1 is that the thickness of the first encapsulation layer in Example 2 is 0.6 mm, and the total thickness of the resulting photovoltaic cell encapsulation structure is 3.2 mm.

[0050] Comparative Example

[0051] The only difference from Example 1 is that in the comparative example, conventional EVA encapsulation films are used between the photovoltaic cell layer and the cover plate, and between the photovoltaic cell layer and the back plate.

[0052] After preparation, the photovoltaic cell encapsulation structures prepared in Example 1 and the comparative example were subjected to the following performance tests and accelerated aging evaluations: First, initial performance characterization was carried out under standard test conditions, and then accelerated aging tests were carried out in the laboratory simulating harsh outdoor environments, specifically, continuous irradiation in the ultraviolet aging environment for 1000 hours. After aging, the key performance parameters were retested and compared with the initial values.

[0053] Test results show that the photovoltaic cell encapsulation structure prepared by this invention has significant advantages in weather resistance, heat dissipation, and power generation performance.

[0054] Weather resistance: After accelerated UV aging (equivalent to long-term outdoor exposure) test, the light transmittance of Example 1 decreased from 92.5% to 91.8%, a decrease of 0.7%, while the light transmittance of the comparative example decreased significantly from 91.2% to 85.3%, a decrease of 5.9%. In terms of interfacial bonding reliability, the bonding strength of Example 1 decreased slightly from 65 N / cm before aging to 62 N / cm, with a retention rate of 95.4%, while the bonding strength of the comparative example decreased significantly from 68 N / cm to 42 N / cm, with a retention rate of only 61.8%, and the appearance showed slight yellowing and local delamination. No such aging phenomenon was observed in Example 1.

[0055] Heat dissipation performance: Under standard test conditions (AM1.5, 1000W / m) 2 At an ambient temperature of 25°C, the battery operating temperature of Example 1 was 42°C, which was 16°C lower than the 58°C of the comparative example, and the heat dissipation efficiency was improved by 32.8%.

[0056] Power generation efficiency: Under standard test conditions, the module conversion efficiency of Example 1 is 23.5%, which is 1.5 percentage points higher than the comparative example's 22.0%.

[0057] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the claims, or equivalent forms of such scope and boundaries.

Claims

1. A photovoltaic cell packaging structure that improves weather resistance and heat dissipation efficiency, characterized in that, At least including: Photovoltaic cell layer; A first encapsulation layer is disposed on the light-receiving side of the photovoltaic cell layer, and the first encapsulation layer contains a chemical bond of organosilicon resin and nano-silica. A second encapsulation layer is disposed on the backlight side of the photovoltaic cell layer, the second encapsulation layer containing a blend of polymer matrix and thermally conductive filler.

2. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to claim 1, characterized in that, The mass ratio of organosilicon resin to nano-silica is (85~95):(5~15).

3. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to claim 2, characterized in that, The silicone resin is an A / B two-component addition-type RTV silicone resin. Component A is vinyl-terminated polydimethylsiloxane, and component B is hydrogen-containing silicone oil. The silicone resin has a transmittance of ≥94% in the 400nm~1100nm wavelength range and a refractive index of 1.41~1.

43.

4. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to claim 2, characterized in that, The thickness of the first encapsulation layer is 0.6mm to 1.0mm.

5. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to any one of claims 1-4, characterized in that, The thermally conductive filler accounts for 8% to 20% of the volume in the blend and includes at least aluminum nitride particles with a particle size of 1 μm to 5 μm.

6. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to claim 5, characterized in that, The polymer matrix includes at least POE.

7. The photovoltaic cell packaging structure for improving weather resistance and heat dissipation efficiency according to any one of claims 1-4 and 6, characterized in that, The thickness of the second encapsulation layer is 0.8mm to 1.2mm.

8. A method for preparing a photovoltaic cell encapsulation structure with improved weather resistance and heat dissipation efficiency as described in any one of claims 1-7, characterized in that, Including the following steps: Organosilicon resin and nano-silica are mixed in a certain proportion, a coupling agent is added, and a hybridization reaction is carried out to obtain a chemically bonded slurry. The polymer matrix and thermally conductive filler are mixed in a certain proportion and then thermally processed to obtain a blend preform film. The photovoltaic cell encapsulation structure is obtained by stacking and laminating the cover plate, chemical bond slurry, photovoltaic cell layer, blend preform film and back sheet in that order, so that the chemical bond slurry is bonded and cured to form the first encapsulation layer, and the blend preform film is bonded to form the second encapsulation layer.

9. The method for improving the weather resistance and heat dissipation efficiency of a photovoltaic cell packaging structure according to claim 8, characterized in that, The coupling agent accounts for 0.5% of the total mass of the silicone resin and nano-silica.

10. The method for improving the weather resistance and heat dissipation efficiency of a photovoltaic cell packaging structure according to claim 8, characterized in that, During lamination: temperature 120℃, pressure 0.8MPa, time 15min.