Highly reflective black photovoltaic encapsulant film, method of making and photovoltaic module

Abstract

The application relates to the technical field of photovoltaic adhesive films, and discloses a high-reflection black photovoltaic packaging adhesive film, a preparation method thereof and a photovoltaic module. The adhesive film is a multilayer co-extrusion composite structure, comprising an A layer (a black reflection layer), a B layer (an antireflection intermediate layer) and a C layer (a white reflection layer); the A layer comprises a quantitative base resin, a functional black master batch (which comprises a quantitative base resin, carbon black and infrared reflection functional fillers (such as at least one of V02:W, infrared reflection type ITO and ceramic microbeads with surface coating treatment)) and a crosslinking agent; the B layer comprises a quantitative base resin, low-refraction inorganic microspheres and a crosslinking agent; and the C layer comprises a quantitative base resin, a reflective white pigment or master batch and a crosslinking agent. The adhesive film can efficiently reflect light back to the battery piece for secondary absorption and utilization while ensuring a pure black appearance, crosslinking degree and peeling strength, can reduce the interface reflection loss of light in the adhesive film, and can significantly improve the module power and the moisture and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulant technology, specifically to a high-reflectivity black photovoltaic encapsulant film, its preparation method, and a photovoltaic module. Background Technology

[0002] Driven by both the photovoltaic industry's move towards grid parity and building-integrated photovoltaics (BIPV), the market has placed higher demands on photovoltaic modules: they need to have an excellent deep black appearance to meet the aesthetic needs of high-end distributed and building-integrated applications, and they need to continuously break through power bottlenecks to reduce the cost per kilowatt-hour.

[0003] However, the current technology has the following bottlenecks and contradictions: (1) Conflict between aesthetics and power: As shown in CN116494620A, the existing method to achieve black photovoltaic modules is to add carbon black to the photovoltaic film, but this will absorb a large amount of sunlight (especially infrared light), which will cause the operating temperature of the photovoltaic module to rise significantly, resulting in a power loss of 0.3-0.4% per degree Celsius and accelerating material aging, forming an industry pain point of sacrificing performance for aesthetics. (2) Limitations of antireflection technology: The mainstream antireflection technology relies on coating the surface of photovoltaic glass with an antireflection film, which has problems such as poor wear resistance, insufficient durability, and increased cost. Although some studies have tried to add antireflection agents in the film, they face challenges such as easy migration, poor thermal stability, and poor compatibility with the encapsulation system. (3) Uniqueness of reflection function: Ordinary white enhancement films can only provide back reflection, which is difficult to solve the problem of reflection loss of front incident light.

[0004] Therefore, developing a new high-reflectivity black photovoltaic encapsulating film that can solve multiple objectives such as deep black appearance, high reflectivity, high power output and aging resistance in one integrated manner, and whose preparation process is simple and fully compatible with existing production lines, has become a key technological requirement to promote the development of high-end photovoltaic applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module.

[0006] Based on this, the present invention discloses a high-reflectivity black photovoltaic encapsulation film, which is a multi-layer co-extruded composite structure, comprising layer A, layer B, and layer C in sequence; layer A is a black reflective layer, which faces the photovoltaic cell, providing a black appearance and undertaking the primary reflection function; layer B is an anti-reflection intermediate layer, which, as an intermediate layer, mainly provides anti-reflection function, reducing interface reflection loss during the propagation of light from the photovoltaic cell to layer A to layer C, and improving the overall light utilization rate; layer C is a white reflective layer, which faces the photovoltaic backsheet / photovoltaic glass, undertaking the core secondary reflection function, reflecting the light transmitted through layers A and B back to the photovoltaic cell, further improving the power generation gain on the back side.

[0007] The black reflective layer comprises the following raw materials in parts by weight: 80-95 parts of matrix resin, 5-20 parts of functional black masterbatch, and 0.5-1.2 parts of crosslinking agent; the functional black masterbatch comprises the following raw materials in parts by weight: 40-80 parts of matrix resin, 10-25 parts of carbon black, and 20-45 parts of infrared reflective functional filler; the infrared reflective functional filler is at least one of tungsten-doped vanadium dioxide, infrared reflective indium tin oxide, and surface-coated ceramic microspheres; the surface-coated ceramic microspheres are preferably ceramic microspheres (such as SiO2, ZrO2) whose surfaces are coated with silane coupling agent and / or titanate coupling agent.

[0008] The antireflective intermediate layer comprises the following raw materials in parts by weight: 80-100 parts of matrix resin, 2-20 parts of low refractive index inorganic microspheres with a refractive index n≈1.10-1.25, and 0.6-1.5 parts of crosslinking agent.

[0009] The white reflective layer comprises the following raw materials in parts by weight: 65-100 parts of matrix resin, 5-35 parts of reflective white pigment or reflective white masterbatch, and 0.6-1.5 parts of crosslinking agent.

[0010] Preferably, the infrared reflective functional filler accounts for 20-60% of the weight of the functional black masterbatch, which is the key to achieving a black and reflective film.

[0011] Preferably, the infrared reflective filler is at least one of tungsten-doped vanadium dioxide (doping amount of 1-2%) and infrared reflective indium tin oxide (ITO, mass ratio of In2O3 to SnO2 ≈ 90:10).

[0012] Preferably, the carbon black is an oxidized high-pigment carbon black variety (such as model C111) with an average particle size of 9-17nm, a blackness value ≤22, a specific surface area >100m² / g, a DBP oil absorption value of 60-98ml / 100g, and a volatile content of 5-8%, in order to improve its surface activity and subsequent processability.

[0013] Preferably, the functional black masterbatch further includes 3-8 parts of a composite dispersion and coupling system, wherein the composite dispersion and coupling system includes 1-2 parts of a low molecular weight dispersant, 1-3 parts of a high molecular weight compatibilizer and 1-3 parts of a reactive coupling agent;

[0014] The low molecular weight dispersant is at least one of polyethylene wax, zinc stearate, etc., used to impregnate and disintegrate carbon black agglomerates; the high molecular weight compatibilizer is at least one of POE-g-MAH (maleic anhydride grafted POE), SEBS-g-MAH (maleic anhydride grafted styrene-ethylene / butene-styrene block copolymer), etc., used to improve the interface between inorganic fillers and resin; the reactive coupling agent is at least one of vinyltrimethoxysilane, titanate coupling agent, etc.

[0015] Preferably, the black reflective layer further includes 0.3-2 parts of anti-aging additives.

[0016] More preferably, the functional black masterbatch includes the following preparation steps:

[0017] S11. The low molecular weight dispersant and carbon black are premixed in a high-speed mixer (stirring speed is 800-1500 rpm) to obtain a carbon black mixture.

[0018] After preheating the infrared reflective functional filler to 90-110°C in a high-speed mixer, the reactive coupling agent diluted with anhydrous ethanol is slowly added in the form of a spray. The mixture is stirred at high speed of 2000-3000 rpm for 5-10 minutes to make the reactive coupling agent uniformly coat the surface of the infrared reflective functional filler, thereby improving its affinity with the resin. This yields the pretreated infrared reflective functional filler.

[0019] S12. The matrix resin, polymer compatibilizer, carbon black mixture, and pretreated infrared reflective functional filler are put into an internal mixer and initially mixed at a low temperature and shear (temperature 100-120°C, time 5-8 minutes, rotor speed 30-50 rpm) to allow the matrix resin melt to fully wet the carbon black and filler. Then, the temperature is raised to 140-160°C and the speed is increased to 70-90 rpm to apply high shear force and internally mix for 10-15 minutes. This forces the carbon black particles and infrared reflective functional filler particles to penetrate and mix evenly in the melt. The shear force is used to form an interpenetrating network structure of carbon black-infrared reflective functional filler-matrix resin at the microscopic level, rather than separate phases. This allows the reactive coupling agent, polymer compatibilizer, carbon black, infrared reflective functional filler, and matrix resin to undergo interfacial reactions or strong interactions to form a strong interface, thus obtaining the well-mixed agglomerated material.

[0020] S13. While the well-mixed agglomerated material is still hot, it is fed into a parallel co-rotating twin-screw extruder and melt-extruded using low temperature and low shear: the temperature of each section is 100-120°C and the screw speed is 100-200 rpm, in order to protect the finely dispersed structure that has been formed and avoid excessive thermomechanical stress that could cause the filler to re-aggregate or the structure to be destroyed. The melt is then pelletized underwater or stretched and cold-cut to obtain black masterbatch with a particle size of 2-3 mm. After being fully dried at 50-60°C, functional black masterbatch is obtained.

[0021] Preferably, the low-refractive-index inorganic microspheres are hollow silica microspheres with an organosilane-modified surface, and / or composite microspheres formed by solid silica with an organosilane-modified surface and hollow polymer microspheres; the average particle size of the low-refractive-index inorganic microspheres is 50 nanometers to 5 micrometers.

[0022] More preferably, the low-refractive-index inorganic microspheres are hollow silica microspheres whose surface is modified with vinyl-containing siloxanes.

[0023] The inorganic microspheres and the matrix resin have a refractive index difference, which together form countless microsphere-resin composite interfaces at the microscopic level. When light passes through the interface of any two media with different refractive indices, it will be reflected (Fresnel reflection), and the reflection loss rate is proportional to the square of the difference in refractive indices between the two media. When light passes through the antireflection intermediate layer where the low-refractive-index inorganic microspheres are located, it will undergo multiple refractions and scatterings at the microsphere-resin interface, which is equivalent to forming a continuous and gently transitioning region inside the film. This significantly reduces the Fresnel reflection loss at the interface, increases the light transmittance, and thus helps to improve the light absorption and utilization rate.

[0024] Preferably, the antireflective intermediate layer further includes 1-3 parts of a surface treatment agent, 0.5-2 parts of an interface stabilizer, and 0.5-1.5 parts of an anti-aging additive. The surface treatment agent is a multifunctional mixture that reacts with both the surface-modifying groups of the low-refractive-index inorganic microspheres and the matrix resin. Its main function is to anchor the low-refractive-index inorganic microspheres to the matrix resin network via chemical bonds, preventing their migration and detachment. The interface stabilizer is a multifunctional acrylate compound, primarily used to enhance the interfacial bonding between the low-refractive-index inorganic microspheres and the matrix resin, preventing migration.

[0025] More preferably, the surface treatment agent is a silane coupling agent system containing peroxide components. For example, the surface treatment agent is preferably a vinylsiloxane system containing peroxide components, such as DCP (dicumyl peroxide) and vinylsiloxanes such as vinyltriethoxysilane (VTES). The preparation process of this surface treatment agent includes: using toluene as a solvent and a methanol solution of sodium methoxide as a catalyst (slowly added under nitrogen protection and a continuous ice-water bath (0-5°C)), DCP (dicumyl peroxide) and excess vinyltriethoxysilane (VTES) are continuously stirred and reacted at room temperature for 8-12 hours. Toluene and unreacted VTES are removed by vacuum distillation below 35°C (strictly controlling the low temperature to prevent peroxide decomposition), resulting in a pale yellow viscous liquid, which is the surface treatment agent. (In the preparation process of the surface treatment agent, under strictly controlled low temperature (<10°C) conditions, DCP is very stable, and the final pale yellow viscous liquid is a mixture of unreacted DCP, VTES, and VTES self-condensation / alcoholization products.) This surface treatment agent can be referred to as a silane coupling agent system containing peroxide components. DCP is usually used as a free radical initiator to initiate the grafting reaction between VTES and the main chain of polymers (such as EVA, POE, etc.). In subsequent processing, through melt co-extrusion, DCP decomposes to generate free radicals, which abstract hydrogen atoms from the polymer chain. The generated polymer free radicals then react with the vinyl groups of VTES, thereby achieving the grafting of VTES and polymers. This can anchor low-refractive-index inorganic microspheres in the matrix resin network, preventing the migration and detachment of low-refractive-index inorganic microspheres.

[0026] Preferably, the reflective white pigment is rutile titanium dioxide; the content of reflective white pigment in the reflective white masterbatch is 40-60%.

[0027] Preferably, the white reflective layer further includes 0.5-1.5 parts of an anti-aging additive.

[0028] More preferably, the anti-aging additive is one or more of ultraviolet absorbers (such as UV-531, UV-234) and light stabilizers (such as Tinuvin 783, Tinuvin 791).

[0029] Preferably, the crosslinking agent is one or more of TAEC (2-ethylhexyl peroxide tert-amyl carbonate), TBEC (tert-butyl peroxide 2-ethylhexyl carbonate), and DCP (diisopropylbenzene peroxide).

[0030] Preferably, the matrix resin is a blend of one or more of EVA (ethylene-vinyl acetate copolymer), POE (polyolefin elastomer), and PVB (polyvinyl butyral). A high-flow grade (MI: 5-25 g / 10 min) is preferred to facilitate processing in highly filled systems.

[0031] Preferably, the thicknesses of the black reflective layer, the antireflective intermediate layer, and the white reflective layer account for 10-25%, 50-70%, and 20-30% of the total thickness of the high-reflectivity black photovoltaic encapsulating film, respectively; the total thickness of the high-reflectivity black photovoltaic encapsulating film is 0.2-0.6 mm (preferably 0.45 mm).

[0032] This invention also discloses a method for preparing a high-reflectivity black photovoltaic encapsulating film, comprising the following preparation steps:

[0033] Step 1: According to the raw material formulas of layers A, B, and C, put the raw materials of each layer into a high-speed mixer and mix them evenly to obtain layer A mixture, layer B mixture, and layer C mixture respectively.

[0034] Step 2: The A-layer mixture, B-layer mixture, and C-layer mixture are fed into three independent single-screw extruders for melt plasticization. The temperature of each extruder is precisely controlled (feed section 80-110℃, melting section 120-150℃, metering section 140-170℃). The three-layer molten material (i.e., A-layer molten material, B-layer molten material, and C-layer molten material) is co-extruded and composite-formed through a composite T-die with a precision flow channel design (die temperature 155-165℃, melt pressure 10-18Mpa to ensure the dispersion and gradient formation of functional fillers and microspheres), thus obtaining a three-layer composite melt structure.

[0035] Step 3: The three-layer composite melt structure is cast from the T-die to the mirror cooling roller (temperature 15-35℃) for rapid cooling and shaping to form the initial film; then, after online thickness measurement, it is drawn at a uniform speed by the traction system and finally wound up to obtain the high-reflectivity black photovoltaic encapsulation film.

[0036] The preparation method of the high-reflectivity black photovoltaic encapsulating film of the present invention is based on a mature multilayer co-extrusion process, which is simple and efficient. It solves the power loss and reliability problems caused by heat absorption in traditional black photovoltaic modules, and is particularly suitable for high-end distributed photovoltaic and building-integrated photovoltaic applications.

[0037] This invention also discloses a photovoltaic module, comprising, from top to bottom, a photovoltaic front panel, a front encapsulating film, a photovoltaic cell, a back encapsulating film, and a photovoltaic backsheet; the back encapsulating film is the high-reflectivity black photovoltaic encapsulating film described above in this invention; the black reflective layer is close to the photovoltaic cell, while the white reflective layer is close to the photovoltaic backsheet. This high-reflectivity black photovoltaic encapsulating film can be applied to single-glass or double-glass photovoltaic modules, and correspondingly, the photovoltaic module can be a single-glass or double-glass photovoltaic module.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] This invention integrates a black reflective layer (layer A), an antireflective intermediate layer (layer B), and a white reflective layer (layer C) into a high-reflectivity black photovoltaic encapsulating film. A specific amount of infrared-reflective filler (preferably at least one of tungsten-doped vanadium dioxide, infrared-reflective indium tin oxide, or surface-coated ceramic microspheres) is introduced into the functional black masterbatch of layer A; a specific amount of low-refractive-index inorganic microspheres is introduced into layer B; and a specific amount of reflective white pigment or reflective white masterbatch is introduced into layer C. Thus, a synergistic effect is achieved in this high-reflectivity black photovoltaic encapsulating film.

[0040] Incident sunlight passes through the gaps between the solar cells and first reaches layer A. The visible light portion is selectively absorbed by layer A, resulting in a black appearance. Layer A can also reflect some of the light passing through the gaps back to the solar cells, improving the light absorption and utilization rate of the solar cells. Some of the light passing through layer A enters layer B. Layer B incorporates low-refractive-index inorganic microspheres to reduce interface reflection loss, maximizing the transmission of this portion of light to layer C. That is, the portion of light that is not completely absorbed by the solar cells and that passes through the gaps between the solar cells passes through layers A and B in sequence, is strongly reflected by layer C, and then refracts back through layer B (passing through the anti-reflection intermediate layer a second time) and layer A before entering the solar cells again, where it is absorbed and utilized.

[0041] Therefore, the high-reflectivity black photovoltaic encapsulating film of the present invention achieves full-path synergistic management of surface light loss reduction, mid-path light transmission enhancement, and back-side reflection enhancement. The synergistic effect of the three layers A, B, and C ensures a deep black aesthetic appearance, the degree of cross-linking of the film, and the peel strength with the photovoltaic glass, while greatly improving the reflectivity of the film, resulting in a significant power gain for the photovoltaic module, and effectively reducing power attenuation after damp heat aging. Detailed Implementation

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides a high-reflectivity black photovoltaic encapsulation film, which is a multi-layer co-extruded composite structure, comprising a black reflective layer (layer A), an anti-reflection intermediate layer (layer B), and a white reflective layer (layer C).

[0045] Layer A (black reflective layer), by weight, comprises the following raw materials:

[0046] Matrix resin POE (melt index 14 g / 10 min): 85 parts;

[0047] Functional black masterbatch: 15 parts;

[0048] Crosslinking agent TBEC (tert-butyl percarbonate-2-ethylhexyl ester): 0.8 parts;

[0049] Anti-aging adjuvant: 1.2 parts (0.7 parts UV-531 + 0.5 parts Tinuvin 783).

[0050] The functional black masterbatch is prepared by premixing high-pigment carbon black with infrared-reflective functional filler (which accounts for 20-60% of the weight of the functional black masterbatch) through a special dispersion process. This functional black masterbatch, by weight, comprises the following raw materials:

[0051] Matrix resin POE (melt index 14 g / 10 min): 55 parts;

[0052] High-pigment carbon black (model C111): 15 parts;

[0053] Infrared reflective functional filler (vanadium dioxide doped with tungsten, abbreviated as VO2:W, doping amount 1.5%): 25 parts;

[0054] Composite dispersion and coupling system: 5 parts (including: 1 part low molecular weight dispersant - polyethylene wax, 2 parts high molecular weight compatibilizer - SEBS-g-MAH and 2 parts reactive coupling agent - vinyltrimethoxysilane).

[0055] Specifically, the preparation process of this functional black masterbatch includes the following steps:

[0056] S11. Premix 15 parts of high-pigment carbon black and 1 part of low molecular weight dispersant in a high-speed mixer at a stirring speed of 1000 rpm to obtain a carbon black mixture. Preheat 25 parts of infrared reflective functional filler to 100°C in a high-speed mixer. Slowly add 2 parts of reactive coupling agent (dissolved in anhydrous ethanol) in the form of a spray. React for 10 minutes under high-speed stirring at 2500 rpm to uniformly coat the surface of the infrared reflective functional filler with the reactive coupling agent, thereby improving its affinity with the matrix resin. This yields the pretreated infrared reflective functional filler.

[0057] S12. Using a intensive mixer, add 55 parts of matrix resin POE and 2 parts of polymer compatibilizer SEBS-g-MAH, along with the prepared carbon black mixture and pretreated infrared reflective functional filler. Under low temperature and shear (temperature: 100°C; time: 5 minutes; rotor speed: 30 rpm), the components are initially mixed. Then, increase the temperature and speed, and apply high shear force (temperature: 150°C; time: 15 minutes; rotor speed: 90 rpm) to use shear force to form an interpenetrating network structure of carbon black-infrared reflective functional filler-matrix resin at the microscopic level, thus obtaining the well-mixed agglomerated material.

[0058] S13. While the well-mixed agglomerated material is still hot, it is fed into a parallel co-rotating twin-screw extruder and melt extruded using low temperature and low shear: the screw speed is 150 rpm, and the temperature of each section is set to 100°C-105°C-105°C-110°C-120°C-115°C-110°C-105°C. The melt is cold-cut by the strand to obtain uniform black masterbatch with a particle size of 2-3 mm. It is then fully dried at 55°C to obtain functional black masterbatch.

[0059] Layer B (antireflective intermediate layer) comprises, by weight, the following raw materials:

[0060] Matrix resin EVA (melt index 25 g / 10 min): 90 parts;

[0061] Low-refractive-index inorganic microspheres (hollow silica microspheres with an average particle size of 1 micrometer and a refractive index n≈1.25) 10 parts;

[0062] Surface treatment agent (a siloxane VTES containing peroxide DCP (dicumyl peroxide): vinyltriethoxysilane. This surface treatment agent is a multifunctional mixture with siloxane ends and free radical initiation ends): 2 parts;

[0063] Interface stabilizer (trimethylolpropane triacrylate): 1 part;

[0064] Crosslinking agent TBEC: 0.9 parts;

[0065] Anti-aging adjuvant: 1.2 parts (0.7 parts UV-531 + 0.5 parts Tinuvin 783).

[0066] The preparation process of low-refractive-index inorganic microspheres includes the following steps:

[0067] 10g of hollow SiO2 microspheres were dried in a vacuum oven at 120°C for 12 hours to completely remove physically adsorbed water and activate the surface silanol groups (-Si-OH). The hollow SiO2 microspheres were then stirred with 200mL of dry toluene and 0.1mL of glacial acetic acid under nitrogen protection to form a suspension. 15mL of VTMS (vinyltrimethoxysilane, in excess) was added to the suspension slowly in a constant pressure dropping funnel. The system was heated to 110°C (the reflux temperature of toluene) and reacted for 24 hours under nitrogen protection and continuous stirring. After the reaction was completed, the mixture was cooled to room temperature, and the solid microspheres were recovered by centrifugation. The average particle size of the microspheres was 1 micrometer, thus obtaining low-refractive-index inorganic microspheres.

[0068] The preparation process of the surface treatment agent includes the following steps: 10g (0.037mol) of DCP (dicumyl peroxide) and 80mL of anhydrous toluene are added to a flask. The DCP is completely dissolved under cooling and stirring in an ice-water bath. Under nitrogen protection and a continuous ice-water bath (0°C), 0.5mL of a methanol solution of sodium methoxide is slowly added as a catalyst using a syringe. Subsequently, 12g (0.063mol, excess) of VTES is added to a constant-pressure dropping funnel and slowly added dropwise to the reaction solution, controlling the dropping rate to keep the reaction temperature below 10°C. After the addition is complete... Afterward, the ice-water bath was removed, and the reaction system was allowed to naturally warm to room temperature. The reaction was then continued with stirring at room temperature for 10 hours. After the reaction was complete, toluene and unreacted VTES were removed by vacuum distillation at below 35°C (strictly controlled low temperature to prevent peroxide decomposition) using a rotary evaporator, yielding a pale yellow viscous liquid, which is the surface treatment agent. (In the preparation process of the surface treatment agent, under strictly controlled low temperature (<10°C) conditions, DCP is very stable, and the final pale yellow viscous liquid is a mixture of unreacted DCP, VTES, and VTES self-condensation / alcoholization products). This surface treatment agent can be referred to as a silane coupling agent system containing peroxide components. DCP is typically used as a free radical initiator to initiate the grafting reaction between VTES and the main chain of polymers (such as EVA, POE, etc.). In subsequent processing, through melt co-extrusion, DCP decomposes to generate free radicals, which abstract hydrogen atoms from the polymer chain. The resulting polymer free radicals then react with the vinyl groups of VTES, thereby achieving the grafting of VTES to the polymer. This can anchor low-refractive-index inorganic microspheres in the matrix resin network, preventing the migration and detachment of low-refractive-index inorganic microspheres.

[0069] The C layer (white reflective layer) comprises, by weight, the following raw materials:

[0070] Matrix resin EVA (melt index 25 g / 10 min): 85 parts;

[0071] Reflective white pigment (rutile titanium dioxide): 15 parts;

[0072] Crosslinking agent TBEC: 0.8 parts;

[0073] Anti-aging adjuvant: 1.2 parts (0.7 parts UV-531 + 0.5 parts Tinuvin 783).

[0074] This embodiment describes a method for preparing a high-reflectivity black photovoltaic encapsulating film, comprising the following preparation steps:

[0075] Step 1: Raw material pretreatment and masterbatch preparation: Functional black masterbatch, low refractive index inorganic microspheres and surface treatment agent are prepared respectively.

[0076] Step 2, Ingredient Mixing: According to the raw material formulas for layers A, B, and C, put the raw materials of each layer into a high-speed mixer and mix them evenly to obtain three-layer mixtures (i.e., layer A mixture, layer B mixture, and layer C mixture).

[0077] Step 3, Melt Co-extrusion: The three-layer compound is fed into three independent single-screw extruders. The temperature of each extruder is precisely controlled (feed section temperature 80℃-90℃-110℃, melt section temperature 120℃-130℃-140℃-150℃-140℃, metering section temperature 140℃-150℃-170℃). The three-layer molten material (i.e., layer A, layer B, and layer C) is co-extruded and compounded into an A / B / C three-layer composite melt structure through a composite T-die with a precision flow channel design. The T-die temperature is 165℃ and the melt pressure is 15MPa.

[0078] Step 4: Casting, Cooling and Shaping: The three-layer composite melt structure is cast from the T-die to the mirror cooling roller (temperature 15℃) for rapid cooling and shaping, forming the initial film. The thickness of layer A is controlled to be 0.09mm, layer B to be 0.27mm, and layer C to be 0.09mm.

[0079] Step 5, Post-processing: After online thickness measurement, the total thickness is controlled to 0.45mm. The film is then pulled at a constant speed by the traction system and finally wound up to obtain the finished film (which is a high-reflectivity black photovoltaic encapsulation film in this embodiment).

[0080] A photovoltaic module according to this embodiment includes, from top to bottom, photovoltaic glass, a front high-transparency encapsulating film (a commercially available film with a transmittance of ≥85% in the 280-380nm range and ≥91% in the 380-1100nm range), a photovoltaic cell, a back encapsulating film, and a photovoltaic backsheet; wherein, the back encapsulating film is a high-reflectivity black photovoltaic encapsulating film as described above in this embodiment (specifically, layer A is close to the photovoltaic cell, and layer C is close to the photovoltaic backsheet).

[0081] Example 2

[0082] This embodiment provides a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Embodiment 1, the difference between this embodiment and Embodiment 1 is:

[0083] In layer A of this embodiment, the infrared reflective filler of the functional black masterbatch is infrared reflective indium tin oxide (ITO, mass ratio of In2O3 to SnO2 ≈ 90:10); the composition of other raw materials and preparation steps are the same as in Example 1.

[0084] Example 3

[0085] This embodiment provides a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Embodiment 1, the difference between this embodiment and Embodiment 1 is:

[0086] In layer C of this embodiment, 15 parts of reflective white pigment in Example 1 are replaced with 25 parts of reflective white masterbatch (the reflective white masterbatch includes white pigment titanium dioxide and matrix resin EVA, and the mass ratio of titanium dioxide in the reflective white masterbatch is 60%), and the matrix resin EVA in layer C is changed to 75 parts; the composition of other raw materials and preparation steps are the same as in Example 1.

[0087] Comparative Example 1

[0088] This comparative example describes a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Example 1, the difference between this example and Example 1 is:

[0089] In this comparative example, the functional black masterbatch of layer A does not contain any infrared reflective filler (and the infrared reflective filler in the functional black masterbatch of layer A in Example 1 is replaced with the same weight of matrix resin POE. Therefore, the weight of matrix resin POE in the functional black masterbatch of layer A in this comparative example is 80 parts); the composition of other raw materials and preparation steps are the same as in Example 1.

[0090] Comparative Example 2

[0091] This comparative example describes a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Example 1, the difference between this example and Example 1 is:

[0092] In this comparative example, layer B does not contain low-refractive-index inorganic microspheres (and the low-refractive-index inorganic microspheres in layer B of Example 1 are replaced with the same weight parts of matrix resin EVA. Therefore, the weight parts of matrix resin EVA in layer B of this comparative example are 100 parts); the composition of other raw materials and preparation steps are the same as in Example 1.

[0093] Comparative Example 3

[0094] This comparative example describes a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Example 1, the difference between this example and Example 1 is:

[0095] No reflective white pigment was added to layer C of this comparative example (and the reflective white pigment in layer C of Example 1 was replaced with the same amount of matrix resin EVA. Therefore, the amount of matrix resin EVA in layer C of this comparative example is 100 parts by weight); the composition of other raw materials and preparation steps are the same as in Example 1.

[0096] Comparative Example 4

[0097] This comparative example presents a high-reflectivity black photovoltaic encapsulating film, its preparation method, and a photovoltaic module. Referring to Comparative Example 1, the difference between this and Comparative Example 1 is:

[0098] In Comparative Example B, no low-refractive-index inorganic microspheres were added (and the low-refractive-index inorganic microspheres in Layer B of Example 1 were replaced with the same weight parts of matrix resin EVA. Therefore, the weight parts of matrix resin EVA in Layer B of Comparative Example B are 100 parts). Furthermore, in Comparative Example C, no reflective white pigment was added (and the reflective white pigment in Layer C of Example 1 was replaced with the same weight parts of matrix resin EVA. Therefore, the weight parts of matrix resin EVA in Layer C of Comparative Example C are 100 parts). The remaining raw material composition and preparation steps are the same as in Comparative Example 1.

[0099] Performance testing

[0100] The high-reflectivity black photovoltaic encapsulating films (hereinafter referred to as films) and photovoltaic modules prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the test results are shown in Table 1 below:

[0101] (1) Reflectivity (780-1100nm), tested according to method B in standard GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics".

[0102] (2) Peel strength with photovoltaic glass, the test shall be conducted in accordance with the standard GB / T 2790-1995 "Test method for peel strength of adhesives at 180°, flexible materials to rigid materials".

[0103] (3) Crosslinking degree, the test shall be conducted in accordance with the provisions of Clause 5.5.3 of GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation".

[0104] (4) Power gain was measured under standard test conditions (STC: irradiance 1000W / m², AM1.5 spectrum, cell temperature 25°C) using the photovoltaic module prepared with encapsulant film in Comparative Example 4 as the benchmark. Power gain and power decay after DH2000h were measured with reference to standard IEC 61215-2:2021 "Ground-mounted photovoltaic modules - design qualification and type approval - Part 2: test procedures".

[0105] Table 1

[0106]

[0107] Compared to Comparative Examples 1-4, the encapsulant films of Examples 1-3 of this invention have higher reflectivity, resulting in higher power gain for their photovoltaic modules and less power degradation after damp heat aging (DH2000h). In contrast, the encapsulant films of Comparative Examples 1-4 show significantly lower reflectivity, resulting in lower power gain for their photovoltaic modules and greater power degradation after damp heat aging. Therefore, the encapsulant film with the A / B / C three-layer co-extruded composite structure of this invention can effectively improve reflectivity across the entire spectrum, increase the power conversion efficiency of photovoltaic cells, improve the power gain of photovoltaic modules, and reduce power degradation of photovoltaic modules after damp heat aging.

[0108] Comparing Example 1 and Comparative Example 1, it was found that: in Comparative Example 1, the reflectivity of the film decreased slightly because no infrared reflective filler was added to the functional black masterbatch of layer A (equivalent to layer A being only a black encapsulant layer), while its peel strength and crosslinking degree remained largely unaffected. This demonstrates that adding infrared reflective filler to the functional black masterbatch of layer A significantly enhances the power output of the photovoltaic module in Example 1 and effectively suppresses power degradation after damp heat aging. Furthermore, it should be noted that excessive addition of infrared reflective filler can increase the cost of the encapsulant film several times compared to conventional products; for example, ITO (indium tin oxide) contains the precious metal indium, which has an extremely high market price; and VO2:W has a complex synthesis process and high cost. Moreover, excessive addition of infrared reflective filler can make the film brittle, reduce tensile strength, and drastically decrease elongation at break, leading to easy breakage during photovoltaic module lamination and resulting in a low yield of photovoltaic modules. Therefore, the preferred weight percentage of infrared reflective filler in the functional black masterbatch of layer A is 20-60%.

[0109] Comparing Example 1 and Comparative Example 2, it was found that: In Comparative Example 2, no low-refractive-index inorganic microspheres were added to layer B. This allowed light transmitted from layer A to pass directly through layer B into layer C, and then be reflected back to layer A via layer C. During this process, the interface reflection loss could not be reduced. Therefore, compared to Example 1, the film in Comparative Example 1 tended to reduce light transmittance and overall reflectivity, resulting in lower power gain of the photovoltaic module and greater power decay after 2000 hours of DH. Furthermore, it should be noted that excessive addition of low-refractive-index inorganic microspheres leads to thin shells of hollow silica microspheres and excessively small spacing between them. During mixing and extrusion, these microspheres are easily crushed and broken, and the resulting fragments become scattering centers, compromising the anti-reflection effect. Simultaneously, excessive addition of low-refractive-index inorganic microspheres introduces numerous voids and defects into the matrix resin, making the film brittle and prone to breakage with slight bending. The amount of low-refractive-index inorganic microspheres added to layer B must be appropriate.

[0110] Comparing Example 1, Comparative Example 3, and Comparative Example 4, it was found that in Comparative Example 4, no substances that help improve the reflectivity of the film were added to layers A, B, and C. In other words, Comparative Example 4 is equivalent to a regular black film. Therefore, compared to Example 1, the reflectivity of the film in Comparative Example 4 is only 40.1%, and its photovoltaic module exhibits the most severe power degradation. In Comparative Example 3, no reflective white pigment or masterbatch was added to layer C. Only a portion of the light was reflected by the infrared reflective filler in layer A, resulting in a significantly reduced reflectivity. Its photovoltaic module power was only 1.8W higher than that of Comparative Example 4. Furthermore, it should be noted that excessive addition of reflective white pigment or masterbatch makes the film brittle, leading to uneven adhesive overflow at the edges during photovoltaic module lamination, and even wrinkling of the photovoltaic backsheet. After UV aging, the yellowing index increases, resulting in excessive power degradation. Extruder screw and barrel wear intensifies, requiring frequent filter replacements and increasing equipment maintenance costs in long-term production. Therefore, the amount of reflective white pigment or masterbatch added to layer C must be appropriate.

[0111] In summary, the high-reflectivity black photovoltaic encapsulating film of the present invention is co-extruded and composited with a black reflective layer (layer A), an antireflective intermediate layer (layer B), and a white reflective layer (layer C). A certain amount of infrared reflective functional filler is introduced into the functional black masterbatch of layer A, a certain amount of low-refractive-index inorganic microspheres are introduced into layer B, and a certain amount of reflective white pigment or reflective white masterbatch is introduced into layer C. Thus, through the synergistic effect of each layer, while ensuring the black appearance, the degree of cross-linking of the film, and the peel strength with photovoltaic glass, the reflectivity of the film can be greatly improved, resulting in a significant power gain for the photovoltaic module and effectively reducing power degradation after damp heat aging.

[0112] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0113] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A high-reflectivity black photovoltaic encapsulating film, characterized in that, It has a multi-layer co-extruded composite structure, which includes layer A, layer B and layer C in sequence. Layer A is a black reflective layer, layer B is an anti-reflective intermediate layer and layer C is a white reflective layer. The black reflective layer comprises the following raw materials in parts by weight: 80-95 parts of matrix resin, 5-20 parts of functional black masterbatch, and 0.5-1.2 parts of crosslinking agent; the functional black masterbatch comprises the following raw materials in parts by weight: 40-80 parts of matrix resin, 10-25 parts of carbon black, and 20-45 parts of infrared reflective functional filler; the infrared reflective functional filler is at least one of tungsten-doped vanadium dioxide, infrared reflective indium tin oxide, and ceramic microspheres whose surface is coated with silane coupling agent and / or titanate coupling agent; The antireflective intermediate layer comprises the following raw materials in parts by weight: 80-100 parts of matrix resin, 2-20 parts of low refractive index inorganic microspheres with a refractive index n of 1.10-1.25, and 0.6-1.5 parts of crosslinking agent. The low-refractive-index inorganic microspheres are hollow silica microspheres with organosilane-modified surfaces, and / or composite microspheres formed by solid silica with organosilane-modified surfaces and hollow polymer microspheres; the average particle size of the low-refractive-index inorganic microspheres is 50 nanometers to 5 micrometers. The white reflective layer comprises the following raw materials in parts by weight: 65-100 parts of matrix resin, 5-35 parts of reflective white pigment or reflective white masterbatch, and 0.6-1.5 parts of crosslinking agent. The reflective white pigment is rutile titanium dioxide; The content of reflective white pigment in the reflective white masterbatch is 40-60%; The matrix resin is a blend of one or more of EVA, POE, and PVB, and the melt index of the matrix resin is 5-25 g / 10 min.

2. The high-reflectivity black photovoltaic encapsulating film according to claim 1, characterized in that, The infrared reflective functional filler accounts for 20-60% of the weight of the functional black masterbatch; The infrared reflective filler is at least one of vanadium dioxide doped with tungsten and infrared reflective indium tin oxide with a doping amount of 1-2%.

3. The high-reflectivity black photovoltaic encapsulating film according to claim 1, characterized in that, The carbon black is an oxidized high-pigment carbon black with an average particle size of 9-17nm, a blackness value of ≤22, a specific surface area of ​​>100m² / g, a DBP oil absorption value of 60-98ml / 100g, and a volatile content of 5-8%. The functional black masterbatch also includes 3-8 parts of a composite dispersion and coupling system, wherein the composite dispersion and coupling system includes 1-2 parts of a low molecular weight dispersant, 1-3 parts of a high molecular weight compatibilizer, and 1-3 parts of a reactive coupling agent; the low molecular weight dispersant is at least one of polyethylene wax and zinc stearate; the high molecular weight compatibilizer is at least one of POE-g-MAH and SEBS-g-MAH; and the reactive coupling agent is at least one of vinyltrimethoxysilane and titanate coupling agent. The black reflective layer also includes 0.3-2 parts of anti-aging additives.

4. The high-reflectivity black photovoltaic encapsulating film according to claim 3, characterized in that, The functional black masterbatch includes the following preparation steps: S11. Premix the low molecular weight dispersant with carbon black to obtain a carbon black mixture; After preheating the infrared reflective functional filler to 90-110°C, the diluted reactive coupling agent is slowly added in the form of a spray. The mixture is stirred at 2000-3000 rpm for 5-10 minutes to ensure that the reactive coupling agent is evenly coated on the surface of the infrared reflective functional filler, thus obtaining the pretreated infrared reflective functional filler. S12. The matrix resin, polymer compatibilizer, carbon black mixture and pretreated infrared reflective functional filler are put into a 100-120°C internal mixer and mixed at 30-50 rpm for 5-8 minutes; then the temperature is raised to 140-160°C and the speed is increased to 70-90 rpm to apply shear force and mix for 10-15 minutes to obtain the well-mixed agglomerated material. S13. The well-mixed agglomerated material is melt-extruded while hot, with the temperature of each section being 100-120°C and the screw speed being 100-200 rpm. The melt is then pelletized underwater or cold-cut by stripping to obtain black masterbatch with a particle size of 2-3 mm. After drying, functional black masterbatch is obtained.

5. The high-reflectivity black photovoltaic encapsulating film according to claim 1, characterized in that, The antireflective intermediate layer further includes 1-3 parts of surface treatment agent, 0.5-2 parts of interface stabilizer, and 0.5-1.5 parts of anti-aging additive; the surface treatment agent is a multifunctional mixture that can react with the surface modification groups of low refractive index inorganic microspheres and the matrix resin; the interface stabilizer is a multifunctional acrylate compound.

6. The high-reflectivity black photovoltaic encapsulating film according to claim 5, characterized in that, The low-refractive-index inorganic microspheres are hollow silica microspheres whose surface is modified with vinyl-containing siloxanes. The surface treatment agent is a silane coupling agent system containing peroxide components.

7. The high-reflectivity black photovoltaic encapsulating film according to claim 1, characterized in that, The white reflective layer also includes 0.5-1.5 parts of anti-aging additives.

8. The high-reflectivity black photovoltaic encapsulating film according to claim 1, characterized in that, The thicknesses of the black reflective layer, the antireflective intermediate layer, and the white reflective layer account for 10-25%, 50-70%, and 20-30% of the total thickness of the high-reflectivity black photovoltaic encapsulation film, respectively; the total thickness of the high-reflectivity black photovoltaic encapsulation film is 0.2-0.6 mm.

9. A method for preparing a high-reflectivity black photovoltaic encapsulating film according to any one of claims 1-8, characterized in that, The preparation steps include the following: Step 1: According to the respective raw material formulas of layer A, layer B, and layer C, mix the raw materials of each layer evenly to obtain layer A mixture, layer B mixture, and layer C mixture respectively. Step 2: After melting and plasticizing the A-layer mixture, B-layer mixture, and C-layer mixture respectively, they are compounded and formed through a multi-layer co-extrusion die. The die temperature is 155-165℃ and the melt pressure is 10-18Mpa, thus obtaining a three-layer composite melt structure. Step 3: Cast the three-layer composite melt structure and cool it to obtain a high-reflectivity black photovoltaic encapsulation film.

10. A photovoltaic module, characterized in that, The photovoltaic panel comprises, from top to bottom, a photovoltaic front panel, a front encapsulating film, a photovoltaic cell, a rear encapsulating film, and a photovoltaic backsheet; the rear encapsulating film is a high-reflectivity black photovoltaic encapsulating film as described in any one of claims 1-8; the black reflective layer is close to the photovoltaic cell, while the white reflective layer is close to the photovoltaic backsheet.

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