Light conversion type ETFE film for photovoltaic packaging and preparation method thereof

Abstract

The invention relates to the technical field of preparation of tetrafluoroethylene copolymer films, and provides a light conversion type ETFE film for photovoltaic packaging and a preparation method thereof, the ETFE film comprises the following raw materials by weight: 100 parts of an ethylene-tetrafluoroethylene copolymer; 0.1-1 part of a light conversion agent; the chemical general formula of the light conversion agent is A2BXO6: Ln < 3 + >, A is at least one of Ca < 2 + >, Sr < 2 + > and Ba < 2 + >, B is Zn < 2 + > or Mg < 2 + >, X is Ti < 2 + > or Si < 2 + >, and Ln < 3 + > is one or more of Sm < 3 + >, Tb < 3 + > and Eu < 3 + >; the weight part of the compatilizer is 20%-50% of the weight part of the light conversion agent, and the compatilizer is a phosphate ester surfactant or a siloxane compound containing perfluoroalkyl. Compared with the prior art, the ETFE film has the advantages that the use of auxiliaries such as a light stabilizer and an antioxidant can be avoided, the potential risk caused by the compatibility of various auxiliaries is avoided, the complexity and the cost of the formula are reduced, and the mechanical property and the photoelectric conversion property of the ETFE film are improved.

Description

Technical Field

[0001] This invention belongs to the field of tetrafluoroethylene copolymer film preparation technology, and particularly relates to a light-converting ETFE film for photovoltaic encapsulation and its preparation method. Background Technology

[0002] Currently, encapsulation materials for solar photovoltaic modules, such as ethylene-vinyl acetate copolymer (EVA) films or fluoropolymer backsheets, are crucial for protecting the cells and ensuring the long-term stable operation of the modules. These materials need to possess high light transmittance, excellent weather resistance, and resistance to ultraviolet aging. The industry commonly uses ultraviolet absorbers (UVA) in the encapsulation materials to block ultraviolet light and slow down the photo-oxidative aging of the polymer materials. However, this passive defense strategy has inherent flaws: approximately 5% of the energy in the solar spectrum—ultraviolet light (wavelength 300-400nm)—is simply absorbed or reflected, its energy not being effectively utilized by the photovoltaic cells, essentially wasting solar energy. Furthermore, UVA itself may fail under long-term ultraviolet radiation, leading to yellowing, powdering, and other deterioration of the encapsulation materials, which in turn accelerates the power degradation of the modules.

[0003] Ethylene-tetrafluoroethylene copolymer (ETFE) is considered an ideal material for next-generation high-performance photovoltaic encapsulation, especially for flexible photovoltaics and building-integrated photovoltaics, due to its inherent high light transmittance (>94%), excellent chemical corrosion resistance, wide operating temperature range, and excellent weather resistance. However, pure ETFE film also lacks the ability to actively utilize ultraviolet light, and photovoltaic modules encapsulated with it still face the problem of approximately 5% ultraviolet energy loss.

[0004] To improve light energy utilization, existing technologies have proposed the concept of "light conversion," which involves adding a light-converting agent (usually a rare-earth-doped inorganic phosphor) to the encapsulation material. The core principle is the "down-conversion" luminescence effect: after the light-converting agent absorbs high-energy (short-wavelength) ultraviolet photons, the rare-earth ions within it undergo electronic energy level transitions, subsequently emitting lower-energy (long-wavelength) visible light photons. Through this wavelength conversion, ultraviolet light, which is originally ineffective for crystalline silicon cells, is converted into visible light (such as blue, green, and red light) with high spectral responsivity, thereby improving the module's short-circuit current and final power generation efficiency.

[0005] However, successfully applying light conversion technology to ETFE matrices faces two major technical bottlenecks: compatibility and high-temperature stability. ETFE resins are processed at temperatures as high as 270-300℃, and many light conversion agents are prone to aggregation, oxidation, or luminescence quenching at these high temperatures. To address this issue, existing technologies (such as CN117511432B) have to introduce multiple additives, including light stabilizers, antioxidants, and crystallization inhibitors, to form a complex stabilization system. Light stabilizers and antioxidants are used to inhibit free radical degradation reactions during high-temperature processing and subsequent use; crystallization inhibitors are used to prevent light conversion agent particles from becoming heterogeneous nucleation sites, disrupting the crystallization behavior of ETFE, and affecting the film's transparency and mechanical properties. This approach leads to complex formulations, increased costs, and excessive additives may introduce new light absorption centers, thereby reducing transmittance and posing long-term compatibility risks.

[0006] To solve the above-mentioned technical problems, this invention designs a light-converting ETFE thin film for photovoltaic encapsulation and its preparation method. Summary of the Invention

[0007] This invention provides a light-converting ETFE thin film for photovoltaic encapsulation and its preparation method, aiming to solve the problems of complex formulation, increased cost, and compatibility risks associated with multi-agent systems in light conversion technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a light-converting ETFE film for photovoltaic encapsulation, wherein, by weight, the ETFE film is composed of the following raw materials: 100 parts of ethylene-tetrafluoroethylene copolymer; 0.1-1 parts of light-converting agent; the general chemical formula of the light-converting agent is A2BXO6:Ln. 3+ Where A is Ca 2+ 、Sr 2+ Ba 2+ At least one of them, B is Zn 2+ or Mg 2+ X is Ti 2+ or Si 2+ Ln 3+ For Sm 3+ 、Tb 3+ Eu 3+ One or more of the following; the compatibilizer is 20%-50% of the weight of the light-converting agent, and the compatibilizer is a phosphate ester surfactant or a siloxane compound containing perfluoroalkyl groups.

[0009] Based on the above technical solution, the fluorinated siloxane coupling agent is a siloxane compound containing a perfluoroalkyl group, which is one of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0010] Based on the above technical solution, the phosphate ester surfactant is one of the following: potassium dodecyl phosphate, potassium tetradecyl phosphate, potassium hexadecyl phosphate, potassium octadecyl phosphate, fluorinated alkyl phosphate, and lauryl polyoxyethylene ether phosphate; the lauryl polyoxyethylene ether phosphate is preferably lauryl polyoxyethylene ether (3-4)EO phosphate.

[0011] Furthermore, the average particle size of the light-converting agent is 0.5-2 μm.

[0012] Secondly, the present invention provides a method for preparing a light-converting ETFE film for photovoltaic encapsulation, applicable to the preparation of the light-converting ETFE film for photovoltaic encapsulation as described in any of the above embodiments, comprising the following steps: S1, mixing ethylene-tetrafluoroethylene copolymer, light-converting agent and compatibilizer in a high-speed mixer, so that the compatibilizer is pre-coated on the surface of the light-converting agent; S2, feeding the uniformly mixed material from step S1 into a twin-screw extruder, melt-blending, extruding, water-cooling, pelletizing, and drying to obtain a light-converting masterbatch; S3, feeding the light-converting masterbatch obtained in step S2 into a single-screw casting film machine, melting and plasticizing, casting into a film through a die, and then cooling, corona treatment, edge trimming and winding to obtain the light-converting ETFE film.

[0013] Based on the above technical solution, in step S1, the mixing temperature is from room temperature to 50°C, and the mixing time is 5-15 minutes.

[0014] Based on the above technical solution, in step S2, the temperature of melt blending is 270-300℃.

[0015] Furthermore, in step S2, the drying temperature is 80-120℃ and the drying time is 3-5 hours.

[0016] Based on the above technical solution, in step S3, the melting and plasticizing temperature is 285-300℃.

[0017] Compared with related technologies, the beneficial effects of the present invention are as follows: This invention incorporates phosphate ester surfactants or perfluoroalkyl siloxane compounds into ethylene-tetrafluoroethylene copolymer (ETFE) and a light-converting agent. Firstly, the silanol or phosphate groups in the compatibilizer form strong chemical bonds or strong adsorption with the hydroxyl groups on the surface of the light-converting agent particles. Secondly, the fluorocarbon chains in the compatibilizer exhibit excellent compatibility with the ETFE matrix, effectively embedding themselves into the ETFE molecular chain. Furthermore, the polyether segments in the compatibilizer (such as lauryl polyoxyethylene ether phosphate) are key structural units enhancing the system's hydrophilicity and compatibility, providing steric hindrance at the interface to prevent the light-converting agent particles from agglomerating during high-stress processing. The added compatibilizer constructs a robust molecular bridge between the light-converting agent and the ETFE matrix, achieving efficient stress transfer and interfacial stability from the inorganic light-converting agent to the organic ETFE matrix. Compared with existing technologies, it can avoid the use of additives such as light stabilizers and antioxidants, avoid the potential risks caused by the compatibility of multiple additives, reduce formulation complexity and cost, and improve the mechanical properties and photoelectric conversion performance of ETFE film. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0021] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0022] The ethylene-tetrafluoroethylene copolymer is from Chemours, Inc., USA, and its brand name is Tefzel™ETFE HT-2184. Light conversion agent A2BXO6:Ln 3+ Purchased from Ganzhou Ansheng Inorganic Materials Co., Ltd. The perfluoroalkyl siloxane compounds (1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane) were purchased from Dow Chemical Company, USA. Phosphate surfactants (potassium dodecyl phosphate, potassium tetradecyl phosphate, potassium hexadecyl phosphate, potassium octadecyl phosphate, fluorinated alkyl phosphate, lauryl polyoxyethylene ether phosphate) were purchased from Solvay.

[0023] Example 1 This disclosure provides a light-converting ETFE film for photovoltaic encapsulation. By weight, the ETFE film is composed of the following raw materials: 100 parts of ethylene-tetrafluoroethylene copolymer; and a light-converting agent Sr2ZnTiO6:Tb. 3+ 0.5 parts, 0.15 parts of 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0024] The method for preparing the photovoltaic encapsulation light-converting ETFE thin film described in Example 1 includes the following steps: S1, the ethylene-tetrafluoroethylene copolymer, the light conversion agent and the compatibilizer are mixed in a high-speed mixer at 40°C for 10 min, so that the compatibilizer is pre-coated on the surface of the light conversion agent; S2, the material that was mixed evenly in step S1 is fed into a twin-screw extruder, and the temperature of each zone is set to 270℃, 280℃, 285℃ and 290℃. The mixture is melt-blended, extruded, water-cooled and pelletized, and dried at 100℃ for 4 hours to obtain the bright masterbatch. S3. The light-converting masterbatch obtained in step S2 is fed into a single-screw casting film machine, melted and plasticized at 295°C, and cast into a film through a die head. Then, after cooling, corona treatment, edge trimming and winding, the light-converting ETFE film with a thickness of 25μm is obtained.

[0025] Example 2 This disclosure provides a light-converting ETFE film for photovoltaic encapsulation, wherein the ETFE film is composed of the following raw materials by weight: 100 parts of ethylene-tetrafluoroethylene copolymer; light-converting agent Ba2MgSiO6:Eu 3+ 0.5 parts, perfluoroalkyl phosphate 0.2 parts.

[0026] The method for preparing the photovoltaic encapsulation light-converting ETFE thin film described in Example 2 includes the following steps: S1, the ethylene-tetrafluoroethylene copolymer, the light conversion agent and the compatibilizer are mixed in a high-speed mixer at 40°C for 10 min, so that the compatibilizer is pre-coated on the surface of the light conversion agent; S2, the material that was mixed evenly in step S1 is fed into a twin-screw extruder, and the temperature of each zone is set to 270℃, 280℃, 285℃ and 290℃. The mixture is melt-blended, extruded, water-cooled and pelletized, and dried at 100℃ for 4 hours to obtain the bright masterbatch. S3. The light-converting masterbatch obtained in step S2 is fed into a single-screw casting film machine, melted and plasticized at 295°C, and cast into a film through a die head. Then, after cooling, corona treatment, edge trimming and winding, the light-converting ETFE film with a thickness of 25μm is obtained.

[0027] Example 3 The composition and preparation method of the photovoltaic encapsulation light-converting ETFE film provided in this embodiment are similar to those in Example 1. The similarities will not be repeated here. The difference is that 0.05 parts of 1H,1H,2H,2H-perfluorooctyltriethoxysilane are used.

[0028] Example 4 The composition and preparation method of the photovoltaic encapsulation light-converting ETFE film provided in this embodiment are similar to those in Example 1, and the similarities will not be repeated. The difference is that 0.25 parts of 1H,1H,2H,2H-perfluorooctyltriethoxysilane are used.

[0029] Example 5 The composition and preparation method of the photovoltaic encapsulation light-converting ETFE film provided in this embodiment are similar to those in Example 1, and the similarities will not be repeated. The difference is that 0.6 parts of 1H,1H,2H,2H-perfluorooctyltriethoxysilane are used.

[0030] Example 6 The ETFE film obtained in Example 1 was placed in a UV aging chamber and aged under a UVA-340 lamp at a temperature of 0.68 W / m². 2 Under conditions of 340nm and a black panel temperature of 60℃, continuous irradiation for 3000 hours was performed. After irradiation, the transmittance remained above 91.5%, the transmittance retention rate was greater than 96.5%, the yellowing index was less than 1.5, and the tensile strength retention rate was greater than 90%. This demonstrates that the ETFE film prepared in Example 1 exhibits extremely excellent resistance to ultraviolet aging, with a lifespan far exceeding that of conventional EVA encapsulation films, meeting the 25-year warranty requirements for photovoltaic modules.

[0031] Example 7 The ETFE film obtained in Example 1 was aged in a constant temperature and humidity chamber at 85°C and 85% relative humidity for 1000 hours. After aging, the light transmittance remained ≥93%, and the tensile strength remained ≥91%. This demonstrates that the ETFE film obtained in Example 1 of this invention exhibits excellent hydrolysis resistance and high temperature and humidity stability.

[0032] Comparative Example 1 This disclosure provides a common ETFE film with a composition and preparation method similar to that of Example 1. The similarities will not be repeated here. The difference is that no light conversion agent or compatibilizer is added.

[0033] Comparative Example 2 This disclosure provides a common ETFE film with a composition and preparation method similar to that of Example 1. The similarities will not be repeated here. The difference is that no compatibilizer is added.

[0034] Comparative Example 3 This disclosure provides a common ETFE film with a composition and preparation method similar to that of Example 1. The similarities will not be repeated here. The difference is that, based on the composition of Example 1, 0.4 parts of light stabilizer 770, 0.6 parts of antioxidant 1010, 0.6 parts of antioxidant 168, and 0.6 parts of crystallization inhibitor poly(perfluorohexadecyl methacrylate) are added.

[0035] Example 8 Monocrystalline silicon solar cells from the same batch were encapsulated using the light-converting ETFE films prepared in Examples 1-5 and the ordinary ETFE films prepared in Comparative Examples 1-3, respectively, to fabricate standard test modules. Under standard test conditions of AM1.5G spectrum, 1000 W / m² irradiance, and a cell temperature of 25°C, the electrical performance parameters of the modules were measured using a solar simulator and an IV meter, and the photoelectric conversion efficiency was calculated.

[0036] The transmittance and mechanical properties of the ETFE films prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the compatibility of the light-converting agents was observed. The results are shown in Table 1 below.

[0037] Table 1 Performance test results of the ETFE films prepared in the examples and comparative examples

[0038] Therefore, Examples 1 and 2 demonstrate that both the fluorosiloxane coupling agent and the phosphate ester surfactant can effectively solve the compatibility problem between the ethylene-tetrafluoroethylene copolymer and the light-converting agent during high-temperature processing. This results in excellent dispersion of the light-converting agent in the ethylene-tetrafluoroethylene copolymer matrix, and the ETFE film exhibits high light transmittance, excellent mechanical properties, and a photoelectric conversion efficiency significantly superior to Comparative Examples 1 and 2. This fully demonstrates the light conversion and dispersion effects of the light-converting agent and the compatibilizer. The photoelectric conversion efficiency is also superior to Comparative Example 3, indicating that the present invention can achieve better performance by replacing a complex auxiliary agent system with a single structured compatibilizer, while also reducing costs and simplifying the process. In Examples 3-5, the amounts of compatibilizer were less than, within, and greater than the scope of this invention, respectively. As seen in Example 3, when the amount of compatibilizer was small, the light-converting agent was poorly dispersed, affecting performance. As seen in Example 5, when the amount of compatibilizer was large, the surface of the ETFE film was slightly sticky, and the mechanical properties and photoelectric conversion efficiency were not significantly improved. Therefore, keeping the amount of compatibilizer within the range of 20%-50% of the weight of the light-converting agent can ensure the performance of the ETFE film while achieving a balance with cost.

[0039] The present invention has been described above by way of example, but the present invention is not limited to the specific embodiments described above. Any modifications or variations made based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A light-converting ETFE thin film for photovoltaic encapsulation, characterized in that, The ETFE film, by weight, is composed of the following raw materials: 100 parts ethylene-tetrafluoroethylene copolymer; 0.1-1 parts light-converting agent; the general chemical formula of the light-converting agent is A2BXO6:Ln. 3+ Where A is Ca 2+ 、Sr 2+ Ba 2+ At least one of them, B is Zn 2+ or Mg 2+ X is Ti 2+ or Si 2+ Ln 3+ For Sm 3+ 、Tb 3+ Eu 3+ One or more of the following; the compatibilizer is 20%-50% of the weight of the light-converting agent, and the compatibilizer is a phosphate ester surfactant or a siloxane compound containing perfluoroalkyl groups.

2. The photovoltaic encapsulation light-converting ETFE thin film according to claim 1, characterized in that, The siloxane compound containing a perfluoroalkyl group is one of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

3. The photovoltaic encapsulation light-converting ETFE thin film according to claim 1, characterized in that, The phosphate ester surfactant is selected from one of the following: potassium dodecyl phosphate, potassium tetradecyl phosphate, potassium hexadecyl phosphate, potassium octadecyl phosphate, fluorinated alkyl phosphate, and lauryl alcohol polyoxyethylene ether phosphate.

4. The photovoltaic encapsulation light-converting ETFE thin film according to claim 1, characterized in that, The average particle size of the light-converting agent is 0.5-2 μm.

5. A method for preparing a light-converting ETFE thin film for photovoltaic encapsulation, applicable to the preparation of the light-converting ETFE thin film for photovoltaic encapsulation as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1, the ethylene-tetrafluoroethylene copolymer, the light conversion agent and the compatibilizer are mixed in a high-speed mixer so that the compatibilizer is pre-coated on the surface of the light conversion agent; S2, the material that was mixed evenly in step S1 is fed into a twin-screw extruder, melt-blended, extruded, water-cooled, pelletized, and dried to obtain a brightening masterbatch; S3. The light-converting masterbatch obtained in step S2 is fed into a single-screw casting film machine, melted and plasticized, and cast into a film through a die head. Then, after cooling, corona treatment, edge trimming and winding, the light-converting ETFE film is obtained.

6. The preparation method according to claim 5, characterized in that, In step S1, the mixing temperature is from room temperature to 50°C, and the mixing time is 5-15 minutes.

7. The preparation method according to claim 5, characterized in that, In step S2, the temperature of melt blending is 270-300℃.

8. The preparation method according to claim 5, characterized in that, In step S2, the drying temperature is 80-120℃ and the drying time is 3-5 hours.

9. The preparation method according to claim 5, characterized in that, In step S3, the temperature for melting and plasticizing is 285-300℃.

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