Double-layer light conversion reflective encapsulant film, preparation method thereof and photovoltaic module

Abstract

The application provides a double-layer light conversion and reflection encapsulating adhesive film and a preparation method thereof and a photovoltaic module, and particularly relates to the technical field of solar photovoltaics. The double-layer light conversion and reflection encapsulating adhesive film is mainly composed of a light conversion layer located at an upper layer and a reflection layer located at a lower layer. The appearance of the light conversion layer is transparent, and the appearance of the reflection layer is white. The pre-crosslinking degree of the light conversion layer is greater than or equal to 25%. The double-layer light conversion and reflection encapsulating adhesive film adopts a structure in which the light conversion layer and the reflection layer are physically separated and arranged in layers. The light conversion layer is highly transparent, can reduce scattering loss and ensure that ultraviolet and near-infrared excitation light can efficiently penetrate. The reflection layer is white, has high diffuse reflectivity and good hiding property, can reflect unused long-wave light back to the battery and improve the light photon recycling efficiency. The pre-crosslinking degree of the light conversion layer is greater than or equal to 25%, which significantly improves the melt strength and flow resistance, inhibits edge creep, abnormal extrusion and overflow white defects in the lamination process and balances the excellent optical function and stable lamination process property from the intrinsic material.

Description

Technical Field

[0001] This invention relates to the field of solar photovoltaic technology, and in particular to a double-layer light-converting and reflective encapsulating film, its preparation method, and a photovoltaic module. Background Technology

[0002] Currently, photovoltaic modules widely use thermosetting encapsulating films (such as EVA or POE) to bond and encapsulate the cells, glass, and backsheet. To improve photoelectric conversion efficiency, the industry has developed smart encapsulating films that integrate optical functional materials. For example, phosphors are doped into the film to achieve light conversion gain for ultraviolet / near-infrared light, or high-reflectivity fillers are introduced to enhance the reuse of unabsorbed light. These functionalized films mostly adopt a single-layer blend structure, that is, fluorescent and reflective components are dispersed together in the same polymer matrix and cured and cross-linked through conventional lamination processes. Although this process is highly mature, it exposes multiple structural contradictions when facing the requirements of high-precision light management: on the one hand, inorganic reflective particles and organic fluorescent molecules have poor compatibility in the polymer matrix, are prone to agglomeration and cause local optical inhomogeneities, resulting in excitation light attenuation and fluorescence reabsorption; on the other hand, the random distribution of reflective particles in the fluorescent phase not only weakens the ultraviolet excitation efficiency, but also reduces the probability of photons returning to the cell junction region due to the uncontrollable diffuse reflection direction.

[0003] More importantly, the aforementioned single-layer blended films face significant process adaptability challenges during lamination. Because functional fillers significantly alter the film's melt viscosity, flow front morphology, and crosslinking kinetics, non-uniform melting and abnormal flow are highly likely to occur during the heating and pressurization stages. When the film is over-extruded along the cell edges, solder ribbon gaps, or grid line gaps and then cools and solidifies on the glass surface, a typical whitening defect forms: manifested as a white, semi-transparent, gel-like residue at the edges. Its causes include the precipitation of insufficiently crosslinked oligomers, additive migration, microbubble retention, and strong light scattering induced by filler enrichment. This phenomenon not only causes poor appearance and interference with EL testing but also damages the integrity of the cell edge encapsulation, becoming a potential pathway for moisture penetration and potential-induced degradation (PID).

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a double-layer light-converting and reflective encapsulating film and its preparation method, as well as a photovoltaic module, in order to solve at least one of the above-mentioned technical problems in the prior art.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The first aspect of the present invention provides a double-layer light-converting and reflective encapsulating film, mainly composed of an upper light conversion layer and a lower reflective layer; wherein the light conversion layer is transparent and the reflective layer is white; the pre-crosslinking degree of the light conversion layer is ≥10%.

[0007] Furthermore, the pre-crosslinking degree of the light conversion layer is ≥30%.

[0008] Preferably, the pre-crosslinking degree of the light conversion layer is 30-55%, more preferably 30-50%.

[0009] Preferably, the optical transmittance of the light conversion layer in the visible light band is >85%.

[0010] Furthermore, the thickness of the light conversion layer is 70~150μm.

[0011] Preferably, the thickness of the reflective layer is 150~400μm.

[0012] Furthermore, based on parts by weight, the formulations of both the light conversion layer and the reflective layer comprise 100 parts of base material and 0.7 to 3.5 parts of functional additives.

[0013] Preferably, the base material includes a matrix resin and functional materials.

[0014] Preferably, the matrix resin includes EVA, POE, or a blend of EVA and POE.

[0015] Preferably, the functional additives include 0.5 to 2.0 parts of crosslinking agent, 0.1 to 1.0 parts of silane coupling agent, and 0.1 to 0.5 parts of antioxidant.

[0016] Preferably, the crosslinking agent includes at least one of dicumyl peroxide (DCP), tert-butyl percarbonate-2-ethylhexyl ester, and triallyl isocyanurate.

[0017] Preferably, the silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0018] Preferably, the antioxidant includes at least one of 1,1,3-tris(3,5-di-tert-butyl-4-hydroxyphenyl)butane and 4,6-bis(dodecylthiomethyl)-o-cresol.

[0019] Furthermore, the functional material of the light conversion layer is a spectral conversion material.

[0020] Preferably, the light conversion layer comprises 5 to 15 parts by weight of functional material, with the remainder being matrix resin.

[0021] Preferably, the spectral conversion material is an ultraviolet-to-blue fluorescent material.

[0022] Preferably, the excitation wavelength of the ultraviolet-to-blue fluorescent material is 280~400nm, the main emission peak wavelength is 420~500nm, and the photoluminescence quantum yield (PLQY) is not less than 80%.

[0023] Preferably, the ultraviolet-to-blue fluorescent material includes at least one of benzotriazole-based light-converting agents, silane coupling agent copolymers, rare earth fluorides, and rare earth silicates.

[0024] Furthermore, the functional material of the reflective layer is a white reflective filler.

[0025] Preferably, the functional material in the reflective layer is 20-30 parts by weight, and the remainder is matrix resin.

[0026] Preferably, the white reflective filler has a reflectivity of not less than 90% for visible light.

[0027] Preferably, the white reflective filler includes at least one of rutile TiO2, barium sulfate, talc, calcium carbonate, magnesium hydroxide, and aluminum hydroxide.

[0028] Preferably, the average particle size of the white reflective filler is 0.2~1.0μm.

[0029] The second aspect of the present invention provides a method for preparing the aforementioned double-layer light-converting and reflective encapsulating film, wherein the raw materials of the light conversion layer are mixed evenly and then extruded and cast to obtain the light conversion layer; the raw materials of the reflective layer are mixed evenly and then extruded and cast to obtain the reflective layer; and finally, the light conversion layer and the reflective layer are hot-pressed together to obtain the double-layer light-converting and reflective encapsulating film.

[0030] Furthermore, the electron beam irradiation dose is 10~80 kGy, and the irradiation voltage is 200~500Kev.

[0031] The third aspect of the present invention provides another method for preparing the double-layer light-converting and reflective encapsulating film, wherein the raw materials of the light conversion layer and the raw materials of the reflective layer are mixed separately and then obtained by melt co-extrusion to obtain a double-layer composite film, and then the upper light conversion layer is irradiated with an electron beam to obtain the double-layer light-converting and reflective encapsulating film; wherein the irradiation dose of the electron beam irradiation is 10~80 kGy.

[0032] A fourth aspect of the present invention provides a photovoltaic module, comprising stacked photovoltaic glass, a transparent front encapsulating film, solar cells, a back encapsulating film, and a backsheet; Alternatively, the photovoltaic module may include photovoltaic glass, a transparent front encapsulating film, solar cells, a back encapsulating film, and photovoltaic glass stacked together; Wherein, the back-side encapsulation film is the double-layer light-converting and reflective encapsulation film described in the first aspect; in the double-layer light-converting and reflective encapsulation film, the light conversion layer is disposed close to the battery cell, and the reflective layer is disposed away from the battery cell.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects: The dual-layer light-converting and reflective encapsulating film provided by this invention physically separates the light conversion layer and the reflective layer in space and arranges them in distinct layers. This allows the light conversion layer to maintain high optical transparency, thereby ensuring efficient penetration of ultraviolet and near-infrared excitation light into the fluorescent material and reducing scattering loss. At the same time, the reflective layer is located in the lower layer and has a white appearance, indicating that it has high diffuse reflectivity and good opacity. It can directionally reflect unused long-wavelength light that has penetrated the light conversion layer back to the battery direction, improving photon recycling efficiency. Crucially, limiting the pre-crosslinking degree of the light conversion layer to ≥10% significantly improves the melt strength and anti-flow ability of the layer in the early stage of lamination. This makes it less prone to edge creep or abnormal extrusion into the solder strip gap / battery edge during the high-temperature melting stage, thereby suppressing the generation of whitening defects from the perspective of the intrinsic properties of the material, and balancing the effectiveness of optical function and the robustness of the lamination process.

[0034] The two preparation methods provided by this invention are simple and controllable, and can stably achieve the layered structure and functional synergy of the light conversion layer and the reflective layer. By first molding separately and then hot-pressing for lamination, or by using a two-layer co-extrusion integral molding process, both methods ensure tight bonding and uniform thickness between the two layers, meeting the lamination requirements of photovoltaic modules. Electron beam irradiation of the light conversion layer allows for precise control of its pre-crosslinking degree, improving the heat resistance and dimensional stability of the film, suppressing abnormal flow during lamination, and avoiding defects such as whitening. Both methods are suitable for large-scale production, ensuring efficient matching of light conversion and reflection functions while improving the processability and long-term reliability of the film, thus meeting the industrial production needs of photovoltaic encapsulation.

[0035] The photovoltaic module provided by this invention employs a double-layer light-conversion and reflective encapsulating film as the back-side encapsulation structure. The light conversion layer is adjacent to the solar cell, efficiently capturing ultraviolet and near-infrared light emanating from the back of the cell and converting it into visible light with higher cell responsivity, thus enabling back-side photon reuse. The reflective layer is located outside the light conversion layer and away from the solar cell. This avoids direct contact between the high-reflectivity filler and the passivation layer, preventing interface defects and electrical interference. Furthermore, it ensures that reflected light passes through the light conversion layer before entering the cell, guaranteeing complete fluorescence conversion and increasing the probability of secondary conversion and absorption. This closed-loop optical path design, combined with a pre-crosslinking degree of ≥25% in the light conversion layer to ensure lamination stability, improves the module's power generation gain in low-light and scattered light environments. Simultaneously, it avoids back-side whitening caused by film flow, ensuring backsheet adhesion and long-term reliability. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in 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, and not all embodiments.

[0037] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0038] The first aspect of the present invention provides a double-layer light-converting and reflective encapsulating film, mainly composed of an upper light conversion layer and a lower reflective layer; wherein the light conversion layer is transparent and the reflective layer is white; the pre-crosslinking degree of the light conversion layer is ≥10%.

[0039] The dual-layer light-converting and reflective encapsulating film provided by this invention physically separates the light conversion layer and the reflective layer in space and arranges them in distinct layers. This allows the light conversion layer to maintain high optical transparency, thereby ensuring efficient penetration of ultraviolet and near-infrared excitation light into the fluorescent material and reducing scattering loss. At the same time, the reflective layer is located in the lower layer and has a white appearance, indicating that it has high diffuse reflectivity and good opacity. It can directionally reflect unused long-wavelength light that has penetrated the light conversion layer back to the battery direction, improving photon recycling efficiency. Crucially, limiting the pre-crosslinking degree of the light conversion layer to ≥10% significantly improves the melt strength and anti-flow ability of the layer in the early stage of lamination. This makes it less prone to edge creep or abnormal extrusion into the solder strip gap / battery edge during the high-temperature melting stage, thereby suppressing the generation of whitening defects from the perspective of the intrinsic properties of the material, and balancing the effectiveness of optical function and the robustness of the lamination process.

[0040] Furthermore, the pre-crosslinking degree of the light conversion layer is ≥30%.

[0041] Preferably, the pre-crosslinking degree of the light conversion layer is 30-55%, more preferably 30-50%.

[0042] Typically, but not limitingly, the pre-crosslinking degree of the light conversion layer can be, for example, 25%, 28%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 45%, 50%, or 55%, or any value in the range of 30% to 55%.

[0043] Preferably, the optical transmittance of the light conversion layer in the visible light band is >85%, ensuring that ultraviolet / near-infrared excitation light can efficiently penetrate and fully excite the spectral conversion material, while the generated visible light is output to the battery layer with low loss, significantly improving photon utilization efficiency and power generation gain.

[0044] Typically, but not limitingly, the optical transmittance of the light conversion layer in the visible light band can be, for example, 86%, 87%, 88%, 89%, 90%, 92%, 95% or higher, or any value in the range of >85%.

[0045] Furthermore, the thickness of the light conversion layer is 70~150μm. A thickness less than 70μm will result in insufficient loading of spectral conversion material and an excessively short excitation light absorption path, significantly weakening the ultraviolet / near-infrared light capture and conversion efficiency, and reducing power gain. At the same time, it is prone to uneven thickness, poor interface bonding, lamination cracking or wrinkling, which will damage optical uniformity and long-term reliability of the component. A thickness exceeding 150μm will prolong the optical path, exacerbate fluorescence self-absorption and scattering loss, reduce the effective light extraction rate, and may induce delamination, warping or debonding from the interface with the reflective layer due to thermal conduction hysteresis and internal stress accumulation, affecting lamination yield and packaging stability.

[0046] Typically, but not limitingly, the thickness of the light conversion layer can be, for example, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm, or any value in the range of 70 to 150 μm.

[0047] Preferably, the thickness of the reflective layer is 150~400μm. When the thickness is less than 150μm, the filling density and optical path of the white reflective filler are insufficient, resulting in visible light reflectivity <90%, decreased diffuse reflection capability, reduced efficiency of unutilized long-wavelength light recirculation, and weakened photon recirculation gain. At the same time, insufficient coverage may expose the underlying structure or cause optical interference to the backsheet. If the thickness exceeds 400μm, it is easy to cause the overall film to be too thick, resulting in poor flowability and insufficient venting during lamination, leading to bubbles or voids; increased thermal conductivity resistance, exacerbating temperature differences and internal stress, increasing the risk of delamination, warping, and edge overflow; in addition, an excessively thick high-filler layer will also increase modulus and brittleness, reduce flexibility and bending resistance, and affect the long-term reliability of the module under mechanical loads.

[0048] Typically, but not limitingly, the thickness of the reflective layer can be, for example, 150 μm, 180 μm, 200 μm, 250 μm, 300 μm, 350 μm, 380 μm or 400 μm, or any value in the range of 150 to 400 μm.

[0049] Furthermore, based on parts by weight, the formulations of both the light conversion layer and the reflective layer comprise 100 parts of base material and 0.7 to 3.5 parts of functional additives.

[0050] Typically, but not limitingly, in the formulations of the light conversion layer and the reflective layer, the base material is 100 parts by weight, and the functional additives can be, for example, 0.7 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.2 parts, or 3.5 parts, or any value in the range of 0.7 to 3.5 parts.

[0051] Preferably, the base material includes a matrix resin and functional materials.

[0052] Preferably, the matrix resin includes EVA, POE, or a blend of EVA and POE.

[0053] Preferably, the functional additives include 0.5 to 2.0 parts of crosslinking agent, 0.1 to 1.0 parts of silane coupling agent, and 0.1 to 0.5 parts of antioxidant.

[0054] Typically, but not limitingly, in the aforementioned functional additives, the crosslinking agent may be, for example, 0.5 parts, 0.8 parts, 1.0 parts, 1.2 parts, 1.5 parts, 1.8 parts, or 2.0 parts, or any value within the range of 0.5 to 2.0 parts; the silane coupling agent may be, for example, 0.1 parts, 0.3 parts, 0.5 parts, 0.7 parts, 0.9 parts, or 1.0 parts, or any value within the range of 0.1 to 1.0 parts; the antioxidant may be, for example, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, or any value within the range of 0.1 to 0.5 parts.

[0055] Preferably, the crosslinking agent includes at least one of dicumyl peroxide (DCP), tert-butyl percarbonate-2-ethylhexyl ester, and triallyl isocyanurate.

[0056] Preferably, the silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0057] Preferably, the antioxidant includes at least one of 1,1,3-tris(3,5-di-tert-butyl-4-hydroxyphenyl)butane and 4,6-bis(dodecylthiomethyl)-o-cresol.

[0058] Furthermore, the functional material of the light conversion layer is a spectral conversion material.

[0059] Preferably, the light conversion layer comprises 5 to 15 parts by weight of functional material, with the remainder being matrix resin.

[0060] Typically, but not limitingly, the functional material in the light conversion layer can be, for example, 5 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, or 15 parts, with the remainder being the matrix resin. The functional material can also be any value within the range of 5 to 15 parts.

[0061] The balance being matrix resin refers to the fact that, in the formulation of the light conversion layer or reflective layer, after deducting the explicitly listed functional materials, the remaining portion consists entirely of matrix resin, comprising 100 parts of the base material.

[0062] Preferably, the spectral conversion material is an ultraviolet-to-blue fluorescent material.

[0063] Preferably, the excitation wavelength of the ultraviolet-to-blue fluorescent material is 280~400nm, the main emission peak wavelength is 420~500nm, and the photoluminescence quantum yield (PLQY) is not less than 80%.

[0064] Preferably, the ultraviolet-to-blue fluorescent material includes at least one of benzotriazole-based light-converting agents, silane coupling agent copolymers, rare earth fluorides, and rare earth silicates.

[0065] Furthermore, the functional material of the reflective layer is a white reflective filler.

[0066] Preferably, the functional material in the reflective layer is 20-30 parts by weight, and the remainder is matrix resin.

[0067] Typically, but not limitingly, the functional material in the reflective layer can be, for example, 20 parts, 22 parts, 25 parts, 27 parts, 29 parts, or 30 parts, with the remainder being the matrix resin. The functional material can also be any value within the range of 20 to 30 parts.

[0068] Preferably, the white reflective filler has a reflectivity of not less than 90% for visible light.

[0069] Preferably, the white reflective filler includes at least one of rutile TiO2, barium sulfate, talc, calcium carbonate, magnesium hydroxide, and aluminum hydroxide.

[0070] Preferably, the average particle size of the white reflective filler is 0.2~1.0μm.

[0071] This invention achieves multiple synergistic gains through a double-layer structure with a transparent top and a white bottom: the light conversion layer efficiently captures and converts ultraviolet light emitted from the back of the cell in situ, generating blue light with higher cell responsivity; the reflective layer directionally reflects unabsorbed long-wavelength light and converted visible light back towards the cell, forming a closed-loop photon utilization path. This dual optical enhancement can stably increase the module power by 2% to 5%. Simultaneously, this structure naturally avoids the white overflow defect caused by abnormal extrusion of fillers into the cell gaps in single-layer blended films. The transparent light conversion layer covers the white reflective layer, providing dual shielding at both visual and physical levels. It conceals the exposure of white filler at the gaps between the solder strips / grid lines, ensuring uniform color and no white spots on the front of the module, perfectly meeting the high aesthetic standards required for the module. In addition, ultraviolet light is efficiently converted in the upper layer, significantly reducing its intensity of penetration down to the reflective layer, backsheet, and encapsulation resin, significantly alleviating ultraviolet aging stress and improving the long-term weather resistance and reliability of the overall encapsulation system. In terms of process, this double-layer structure can be formed in one step using existing melt co-extrusion equipment, and electron beam irradiation only needs to be precisely applied to the upper layer, without changing the configuration of mainstream production lines, combining technological advancement with the feasibility of industrialization.

[0072] The second aspect of the present invention provides a method for preparing the aforementioned double-layer light-converting and reflective encapsulating film, wherein the raw materials of the light conversion layer are mixed evenly and then extruded and cast to obtain the light conversion layer; the raw materials of the reflective layer are mixed evenly and then extruded and cast to obtain the reflective layer; and finally, the light conversion layer and the reflective layer are hot-pressed together to obtain the double-layer light-converting and reflective encapsulating film.

[0073] Furthermore, the irradiation dose of the electron beam is 10~80 kGy.

[0074] The third aspect of the present invention provides another method for preparing the aforementioned double-layer light-converting and reflective encapsulating film, wherein the raw materials of the light conversion layer and the reflective layer are mixed separately and then obtained by melt co-extrusion to obtain a double-layer composite film, and then the upper light conversion layer is irradiated with an electron beam to obtain the double-layer light-converting and reflective encapsulating film; wherein the irradiation dose of the electron beam irradiation is 10~80 kGy and the irradiation voltage is 200-500Kev.

[0075] The two preparation methods provided by this invention are simple and controllable, and can stably achieve the layered structure and functional synergy of the light conversion layer and the reflective layer. By first molding separately and then hot-pressing for lamination, or by using a two-layer co-extrusion integral molding process, both methods ensure tight bonding and uniform thickness between the two layers, meeting the lamination requirements of photovoltaic modules. Electron beam irradiation of the light conversion layer allows for precise control of its pre-crosslinking degree, improving the heat resistance and dimensional stability of the film, suppressing abnormal flow during lamination, and avoiding defects such as whitening. Both methods are suitable for large-scale production, ensuring efficient matching of light conversion and reflection functions while improving the processability and long-term reliability of the film, thus meeting the industrial production needs of photovoltaic encapsulation.

[0076] Typically, but not limitingly, the irradiation dose of the electron beam irradiation can be, for example, 10 kGy, 20 kGy, 30 kGy, 40 kGy, 50 kGy, 60 kGy, 70 kGy or 80 kGy, or any value in the range of 10 to 80 kGy.

[0077] A fourth aspect of the present invention provides a photovoltaic module, comprising stacked photovoltaic glass, a transparent front encapsulating film, solar cells, a back encapsulating film, and a backsheet; Alternatively, the photovoltaic module may include photovoltaic glass, a transparent front encapsulating film, solar cells, a back encapsulating film, and photovoltaic glass stacked together; Wherein, the back-side encapsulation film is the double-layer light-converting and reflective encapsulation film described in the first aspect; in the double-layer light-converting and reflective encapsulation film, the light conversion layer is disposed close to the battery cell, and the reflective layer is disposed away from the battery cell.

[0078] The photovoltaic module provided by this invention, by using a double-layer light-converting and reflective encapsulating film dedicated to the back-side encapsulation location, with the light conversion layer positioned close to the solar cell, can efficiently capture unabsorbed ultraviolet and near-infrared light escaping from the back of the cell and convert it in situ into visible light with higher responsivity within the cell's main light-absorbing region, thus achieving on-site reuse of back-side photons. Meanwhile, the reflective layer is located outside the light conversion layer and away from the solar cell. This avoids potential interface defects or electrical interference caused by direct contact between the high-reflectivity filler and the cell passivation layer, and ensures that the reflected light must first penetrate the light conversion layer before incident on the back of the cell. The battery ensures that 100% of the reflected light undergoes a fluorescence conversion process. This means that any long-wavelength light returned by the reflection layer must pass through the light conversion layer before reaching the battery again, significantly increasing the probability of photons being converted and absorbed a second time. This closed-loop optical path design of "back-incidence-conversion-reflection-reconversion-incidence" combined with the lamination stability ensured by the ≥25% pre-crosslinking degree of the light conversion layer, synergistically improves the actual power generation gain of the module in weak light, scattered light, and long-wavelength enrichment environments, and fundamentally avoids the impact of back-side whitening caused by abnormal film flow on the integrity of the backsheet adhesion and long-term reliability.

[0079] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0080] Example 1 This embodiment provides a double-layer light-converting reflective encapsulating film, the preparation process of which is as follows: 1. The formula for the light conversion layer is: 90 parts EVA resin, light conversion masterbatch (rare earth fluoride NaYF4:Yb). 3+ / Er 3+ 10 parts, peroxide 2 0.6 parts of ethylhexyl tert-butyl carbonate, 0.6 parts of triallyl isocyanurate, 0.3 parts of silane KH-570, and 0.1 parts of light stabilizer 770.

[0081] The rare earth fluoride and the matrix EVA resin are granulated at a mass ratio of 6:94, and the amount of rare earth fluoride used is 0.6 parts.

[0082] The reflective layer formula is: 75 parts EVA resin, 25 parts titanium dioxide masterbatch (rutile type), and 2 parts peroxide. 0.6 parts of ethylhexyl tert-butyl carbonate, 0.6 parts of triallyl isocyanurate, 0.3 parts of silane KH-570, and 0.1 parts of light stabilizer 770.

[0083] 2. The light conversion layer raw material and the reflective layer raw material are put into a mixer and mixed evenly. Then, they are formed by extrusion casting machine to obtain the light conversion layer semi-finished product and the reflective layer film material respectively.

[0084] 3. The semi-finished light conversion layer is irradiated with an electron beam at an irradiation dose of 55 kGy. Irradiation is stopped after the pre-crosslinking degree reaches 30% to obtain the light conversion layer film.

[0085] 4. The light conversion layer film and the reflective layer film are hot-pressed together at 110℃ and 0.5MPa to obtain a double-layer light conversion and reflective encapsulation film, wherein the thickness of the light conversion layer is 100μm and the thickness of the reflective layer is 300μm.

[0086] Example 2 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the amount of EVA resin in the light conversion layer is modified to 85 parts, the amount of light conversion masterbatch is modified to 15 parts, and the other components remain unchanged; the amount of EVA resin in the reflective layer is modified to 70 parts, the amount of titanium dioxide masterbatch (rutile type) is modified to 30 parts, and the other components remain unchanged; the pre-crosslinking degree in step 3 is controlled at 35%, and the remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0087] Example 3 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the amount of EVA resin in the light conversion layer is modified to 95 parts, the amount of light-converting masterbatch is modified to 5 parts, and the other components remain unchanged; the amount of EVA resin in the reflective layer is modified to 80 parts, the amount of titanium dioxide masterbatch (rutile type) is modified to 20 parts, and the other components remain unchanged; the pre-crosslinking degree in step 3 is controlled at 25%, and the remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0088] Example 4 This embodiment provides a double-layer light-converting reflective encapsulating film. The difference from Embodiment 1 is that the pre-crosslinking degree in step 3 is controlled at 55%. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0089] Example 5 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the pre-crosslinking degree in step 3 is controlled at 60%. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0090] Example 6 This embodiment provides a double-layer light-converting reflective encapsulating film, the preparation process of which is as follows: 1. Same as the step in Example 1.

[0091] 2. After the light conversion layer material and the reflective layer material are mixed evenly, they are fed into the two barrels of the extruder and melt-extruded through the co-extrusion die to obtain a double-layer composite film.

[0092] 3. The light conversion layer side of the double-layer composite film is irradiated with an electron beam at an irradiation dose of 55 kGy to achieve a pre-crosslinking degree of 30%, thus obtaining a double-layer light conversion and reflection encapsulation film.

[0093] Example 7 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the thickness of the light conversion layer is 50 μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0094] Example 8 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the thickness of the light conversion layer is 70 μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0095] Example 9 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the thickness of the light conversion layer is 150μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0096] Example 10 This embodiment provides a double-layer light-converting and reflective encapsulating film. The difference from Embodiment 1 is that the thickness of the light conversion layer is 180μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0097] Example 11 This embodiment provides a double-layer light-converting reflective encapsulating film. The difference from Embodiment 1 is that the reflective layer thickness is 100μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0098] Example 12 This embodiment provides a double-layer light-converting reflective encapsulating film. The difference from Embodiment 1 is that the reflective layer thickness is 150μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0099] Example 13 This embodiment provides a double-layer light-converting reflective encapsulating film. The difference from Embodiment 1 is that the reflective layer thickness is 400μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0100] Example 14 This embodiment provides a double-layer light-converting reflective encapsulating film. The difference from Embodiment 1 is that the reflective layer thickness is 420μm. The remaining steps and raw materials are the same as in Embodiment 1, and will not be repeated here.

[0101] Comparative Example 1 This comparative example provides an encapsulating film that differs from Example 1 in that the light conversion layer is omitted and only a reflective layer is used. The preparation method of the reflective layer is the same as that of Example 1.

[0102] Comparative Example 2 This comparative example provides an encapsulating film with a single-layer structure. The film formulation is as follows: 65 parts EVA resin, 10 parts light conversion masterbatch, 25 parts titanium dioxide masterbatch (rutile type), and 2 parts peroxide. 0.6 parts of ethylhexyl tert-butyl carbonate, 0.6 parts of triallyl isocyanurate, 0.3 parts of silane KH-570, and 0.1 parts of light stabilizer 770.

[0103] The raw materials are put into a mixer and mixed evenly, and then formed by an extrusion casting machine to obtain an encapsulating film.

[0104] Comparative Example 3 This comparative example provides an encapsulating film. Unlike Example 1, step 3 is omitted. Instead, the light conversion layer semi-finished product and the reflective layer film are directly hot-pressed together. The remaining steps and raw materials are the same as in Example 1, and will not be repeated here.

[0105] Comparative Example 4 This comparative example provides an encapsulating film. Unlike Example 1, the amount of EVA resin in the light conversion layer formulation is modified to 100 parts, the light conversion masterbatch is omitted, and step 3 is not performed. The remaining steps and raw materials are the same as in Example 1, and will not be repeated here.

[0106] Comparative Example 5 This comparative example provides a double-layer light-converting and reflective encapsulating film. The difference from Example 1 is that the pre-crosslinking degree in step 3 is controlled at 20%. The remaining steps and raw materials are the same as in Example 1, and will not be repeated here.

[0107] Comparative Example 6 The encapsulating film used in this comparative example is a conventional transparent EVA film.

[0108] Test Example 1 The encapsulating films prepared in the examples and comparative examples were used as the back encapsulating films for photovoltaic modules. The photovoltaic modules were fabricated by laminating the photovoltaic glass, transparent front encapsulating film, N-type TOPCon solar cells, encapsulating film, and back glass in the following order: lamination temperature 145±5℃, lamination time 15-20 minutes.

[0109] The prepared photovoltaic modules were subjected to the following tests: Evaluation of Whitening Excess: After lamination, observe under a microscope whether white adhesive has overflowed from the edges (spacing area) of the solar cells onto the front side of the cells. Count 100 solar cells and calculate the percentage of cells exhibiting whitening (whitening incidence rate). The lower the incidence rate, the better the resistance to whitening.

[0110] Power gain: under standard test conditions (STC, AM1.5, 1000W / m) 2 Under these conditions, the actual output power of the components is tested. Using the power of a standard component in a 6-package as a baseline (denoted as 0W), the power gain value (in W) of each component is calculated. A higher positive value indicates a more significant gain effect.

[0111] Reflectance: The average reflectance of the film in the 400-1100 nm wavelength range was measured using a UV-Vis-NIR spectrophotometer.

[0112] Module appearance: Visually inspect the laminated modules for defects such as bubbles, wrinkles, and microcracks in the cells (detected by EL).

[0113] The test results are recorded in Table 1.

[0114] Table 1

[0115] As shown in Table 1, the power gain of the blended film of single-layer titanium dioxide masterbatch and light conversion masterbatch is far lower than that of the double-layer light conversion-white film, and it also increases the risk of whitening and fragmentation. Examples 1-6, with a pre-crosslinking degree controlled at 30%-55%, a light conversion layer thickness of 70-150 μm, and a reflective layer thickness of 150-400 μm, all achieved zero whitening, an average reflectivity of over 93%, and a stable power gain between 8.3 W and 9.2 W. Furthermore, no microcracks were detected by EL testing, fully verifying the dual guarantee effect of physical layering structure and appropriate pre-crosslinking on optical performance and process robustness.

[0116] When the thickness of the light conversion layer is less than 70 μm, as in Example 7, the whitening rate rises to 8%, indicating that excessive thinness leads to insufficient melt strength and weakened interfacial bonding. When the thickness of the reflective layer is less than 150 μm, as in Example 11, the reflectivity drops sharply to 85.7%, and the power gain declines significantly to 5.8 W, confirming that the filler optical path is severely insufficient. When the reflective layer exceeds 400 μm, as in Example 14, the whitening rate rises back to 9%, revealing that excessive thickness exacerbates lamination flow instability. When the pre-crosslinking degree is less than 25%, as in Comparative Example 5, the whitening rate reaches 15%, and in Comparative Example 3 it is even higher at 25%, confirming that low crosslinking degree cannot suppress edge creep. When the pre-crosslinking degree is too high, as in Examples 4 and 5, the risk of microcracks increases significantly, indicating that the rigidity of the crosslinking network has exceeded the mechanical tolerance limit of the solar cell. In contrast, Comparative Example 2, with its single-layer blend structure, not only exhibits a whitening rate of 42% and a power gain of only 4.2W, but also suffers from numerous microcracks, directly exposing its optical interference and process defects. The comparative examples with pure reflection or no light conversion both have a power gain of less than 2W, highlighting the irreplaceable dual-function synergy of this invention. The physical separation architecture of high light transmittance conversion in the upper layer and high diffuse reflection in the lower layer, coupled with a pre-crosslinking degree of 25%-55%, particularly 30%-50%, is a feasible path to achieve efficient photon recycling and high-yield lamination packaging.

[0117] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A double-layer light-converting and reflective encapsulating film, characterized in that, It mainly consists of an upper light conversion layer and a lower reflective layer; The light conversion layer is transparent, and the reflective layer is white. The pre-crosslinking degree of the light conversion layer is ≥10%.

2. The double-layer light-converting and reflective encapsulating film according to claim 1, characterized in that, The pre-crosslinking degree of the light conversion layer is ≥30%; Preferably, the pre-crosslinking degree of the light conversion layer is 30-55%, more preferably 30-50%; Preferably, the optical transmittance of the light conversion layer in the visible light band is >85%.

3. The double-layer light-converting reflective encapsulating film according to claim 1 or 2, characterized in that, The thickness of the light conversion layer is 70~150μm; Preferably, the thickness of the reflective layer is 150~400μm.

4. The double-layer light-converting and reflective encapsulating film according to claim 1 or 2, characterized in that, Based on parts by weight, the formulations of both the light conversion layer and the reflective layer comprise 100 parts of base material and 0.7 to 3.5 parts of functional additives; Preferably, the base material includes a matrix resin and functional materials; Preferably, the matrix resin includes EVA, POE, or a blend of EVA and POE; Preferably, the functional additives include 0.5-2.0 parts of a crosslinking agent, 0.1-1.0 parts of a silane coupling agent, and 0.1-0.5 parts of an antioxidant; Preferably, the crosslinking agent includes at least one of dicumyl peroxide (DCP), tert-butyl percarbonate-2-ethylhexyl ester, and triallyl isocyanurate; Preferably, the silane coupling agent comprises at least one of γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane; Preferably, the antioxidant includes at least one of 1,1,3-tris(3,5-di-tert-butyl-4-hydroxyphenyl)butane and 4,6-bis(dodecylthiomethyl)-o-cresol.

5. The double-layer light-converting and reflective encapsulating film according to claim 4, characterized in that, The functional material of the light conversion layer is a spectral conversion material; Preferably, the light conversion layer comprises 5 to 15 parts by weight of functional material, with the remainder being matrix resin; Preferably, the spectral conversion material is an ultraviolet-to-blue fluorescent material; Preferably, the excitation wavelength of the ultraviolet-to-blue fluorescent material is 280~400nm, the main emission peak wavelength is 420~500nm, and the photoluminescence quantum yield (PLQY) is not less than 80%. Preferably, the ultraviolet-to-blue fluorescent material includes at least one of benzotriazole-based light-converting agents, silane coupling agent copolymers, rare earth fluorides, and rare earth silicates.

6. The double-layer light-converting reflective encapsulating film according to claim 4, characterized in that, The functional material of the reflective layer is a white reflective filler; Preferably, the functional material in the reflective layer is 20-30 parts by weight, and the remainder is matrix resin; Preferably, the white reflective filler has a reflectivity of not less than 90% for visible light; Preferably, the white reflective filler comprises at least one of rutile TiO2, barium sulfate, talc, calcium carbonate, magnesium hydroxide, and aluminum hydroxide; Preferably, the average particle size of the white reflective filler is 0.2~1.0μm.

7. A method for preparing a double-layer light-converting reflective encapsulating film according to any one of claims 1 to 6, characterized in that, The light conversion layer is obtained by uniformly mixing the raw materials of the light conversion layer, followed by extrusion casting and electron beam irradiation. The reflective layer is obtained by uniformly mixing the raw materials of the reflective layer and then extruding and casting it. Finally, the light conversion layer and the reflective layer are hot-pressed together to obtain a double-layer light-converting and reflective encapsulating film.

8. The preparation method according to claim 7, characterized in that, The electron beam irradiation dose is 10~80kGy.

9. A method for preparing a double-layer light-converting reflective encapsulating film according to any one of claims 1 to 6, characterized in that, The raw materials for the light conversion layer and the reflective layer are mixed separately and then melt co-extruded to obtain a double-layer composite film. The upper light conversion layer is then irradiated with an electron beam to obtain the double-layer light conversion and reflective encapsulation film. The electron beam irradiation dose is 10~80 kGy, and the irradiation voltage is 200~500Kev.

10. A photovoltaic module, characterized in that, This includes stacked photovoltaic glass, transparent front encapsulating film, solar cells, back encapsulating film, and backsheet; Alternatively, the photovoltaic module may include photovoltaic glass, a transparent front encapsulant film, solar cells, a back encapsulant film, and photovoltaic glass stacked together; Wherein, the back sealing film is the double-layer light-converting and reflective sealing film as described in any one of claims 1 to 6; In the double-layer light-converting and reflective encapsulating film, the light conversion layer is positioned close to the solar cell, while the reflective layer is positioned away from the solar cell.

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