A light-transmitting polymer composite material and a preparation method and application thereof

Abstract

This invention provides a light-transmitting polymer composite material, its preparation method, and its application. The down-conversion material used in this invention can be uniformly dispersed within the light-transmitting matrix resin without affecting the light transmittance of the sheet, while maintaining high luminous intensity and stability. Applying this light-transmitting polymer composite material to photovoltaic encapsulation films can improve the responsiveness and external quantum efficiency of photovoltaic modules in the ultraviolet region.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic module material technology, specifically relating to a light-transmitting polymer composite material, its preparation method, and its application in photovoltaic encapsulation films. Background Technology

[0002] Photovoltaic cells generate electricity using solar energy. When the incident wavelength energy matches the bandgap of the photovoltaic cell, the cell's response to that wavelength and its corresponding current output capability are better. When the incident wavelength energy is much higher than the solar bandgap energy (such as ultraviolet light with wavelengths <400nm), the excess energy tends to be converted into heat and promote carrier recombination, affecting current generation. Therefore, commercially available photovoltaic cells such as polycrystalline silicon photovoltaic cells, cadmium telluride (CdTe), copper indium gallium selenide (CIGS) thin-film cells, and perovskite photovoltaic cells have very low response and utilization rates in the ultraviolet light region.

[0003] Furthermore, ultraviolet (UV) radiation can also affect the stability of photovoltaic (PV) modules and reduce their lifespan. Ethylene vinyl acetate (EVA) is the most commonly used encapsulating film material for PV systems. Because this type of film is sensitive to UV radiation, UV absorbers are typically added to the film commercially. Under the action of UV absorbers, UV radiation is converted into heat and is not utilized. If UV light could be converted into lower-energy visible light, it could be effectively used for power generation.

[0004] Existing technologies tend to introduce light-down conversion (LDS) materials above the light-absorbing layer of photovoltaic modules (e.g., on the upper or inner layer of the encapsulating glass, or inside the encapsulating film) to absorb ultraviolet light and emit lower-energy visible light, thereby increasing the stability and utilization of photovoltaic devices in that wavelength range. This utilizes the characteristic of light-conversion materials to absorb short-wavelength light and emit long-wavelength light.

[0005] Traditional photoluminescent downconversion materials (particles) include fluorescent small molecules, rare-earth materials, and inorganic quantum dots. However, fluorescent small molecules and rare-earth materials generally suffer from low stability and are frequently quenched during use, with a lifespan of only about two years. While inorganic quantum dots exhibit good photostability, their low dispersibility in polymers and low quantum efficiency remain intractable problems. Furthermore, all three materials belong to aggregated fluorescence quenching (ACQ) materials—photoluminescent particles typically emit strong light when existing as isolated molecules, but when aggregated (under high concentration / film / solid conditions), nonradiative energy transfer occurs between the closely packed luminescent particles, leading to self-quenching of fluorescence. Therefore, the loading concentration of such luminescent materials in polymers is very limited, the fluorescence intensity emitted by the particles is quite limited, and the resulting increase in photovoltaic efficiency is not significant.

[0006] Compounds exhibiting aggregation-induced emission (AIE) properties show weak luminescence as isolated molecules, but high luminescence efficiency at high concentrations, in film, and in solid states, making them ideal as additives for incorporating into polymer films to enable photo-down conversion. Tetraphenylene and its derivatives, as typical AIE molecules, possess advantages such as high quantum yield, ease of synthesis, ease of functionalization, and high stability. Tetraphenylene and its derivatives exhibit maximum absorption of incident radiation below 400 nm and maximum emission of radiation over a longer wavelength range of 400-900 nm. Therefore, using these compounds as photo-down conversion materials in photovoltaic modules does not result in visible light loss. Although these compounds have been extensively studied in various fields, their application in photovoltaics is still relatively limited. Directly incorporating tetraphenylene molecules into transparent polymer resins can lead to poor uniformity in the luminescence properties of the resulting polymer resin film, resulting in excessively strong localized luminescence. Furthermore, surfactant modification of tetraphenylene can affect the aggregation state of molecules within the polymer, reducing luminescence intensity.

[0007] Existing technologies lack a method that can uniformly disperse light-converting particles in a polymer matrix while maintaining high quantum efficiency and stability. Summary of the Invention

[0008] This invention provides a light-transmitting polymer composite material in which a photoconversion material with long-lasting photoconversion function is added. The photoconversion material used in this invention can be uniformly dispersed within the light-transmitting matrix resin without affecting the light transmittance of the sheet, while maintaining high luminous intensity and stability. This invention also provides a method for preparing the aforementioned light-transmitting polymer composite material, which, when used as a photovoltaic encapsulation film, can improve the external quantum efficiency (EQE) of photovoltaic modules in the ultraviolet region over a long period.

[0009] One objective of this invention is to provide a light-transmitting polymer composite material comprising a photoconversion material and a light-transmitting matrix resin, wherein the photoconversion material is a polymer with a tetraphenylethylene structure in its side chains.

[0010] According to the present invention, the structural formula of the optical down-conversion material is as follows:

[0011]

[0012] In formula (I) or formula (II), R1 is independently a substituted or unsubstituted alkyl group having 2 to 20 carbon atoms, R2 to R4 are independently selected from H, OH, halogen, substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, substituted or unsubstituted aryl or aralkyl group having 6 to 30 carbon atoms, and Y is selected from at least one of substituted or unsubstituted alkyl or aralkyl group having 2 to 30 carbon atoms.

[0013] According to the present invention, the optical down-conversion material has a maximum value of incident radiation absorption below 400 nm and a maximum value of radiation emission at longer wavelengths in the range of 400 to 900 nm.

[0014] According to the present invention, the number-average molecular weight of the photo-down-conversion material is 5,000 to 50,000, preferably 10,000 to 30,000.

[0015] According to the present invention, the light-transmitting matrix resin includes, but is not limited to, at least one of ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate-based multi-component copolymer, ethylene-methyl acrylate-based multi-component copolymer, ethylene-ethyl acrylate-based multi-component copolymer, ethylene-methyl methacrylate-based multi-component copolymer, ethylene-α-olefin copolymer, polyvinyl butyral, polymethyl methacrylate, polyalkyl methacrylate, alkyl acrylate copolymer, hydrogenated styrene-butadiene block copolymer, styrene-ethylene / propylene-styrene block copolymer, polyurethane resin, ionomer, polysiloxane, and epoxy resin, preferably at least one of ethylene-vinyl acetate copolymer (EVA), polymethyl methacrylate (PMMA), and epoxy resin.

[0016] According to the present invention, in the light-transmitting polymer composite material, the down-conversion material is 0.01-5% of the light-transmitting matrix resin, preferably 0.025-1% by mass percentage; the light transmittance of the light-transmitting polymer composite material is 70-99%, preferably 80-95%.

[0017] According to the present invention, the light-transmitting polymer composite material may also contain other commonly used additives in the art. For example, at least one of a crosslinking agent, an antioxidant, and a photoinitiator may be optionally added during the preparation of the light-transmitting polymer composite material. It may also contain other additives known in the art, including crosslinking aids, flow-enhancing additives, compatibilizers, lubricants, dyes, flame retardants, impact modifiers, nucleating agents, anti-blocking agents (e.g., silica), heat stabilizers, dispersants, surfactants, chelating agents, coupling agents, and reinforcing additives (e.g., glass fibers, fillers, etc.).

[0018] A second objective of this invention is to provide a method for preparing the above-mentioned light-transmitting polymer composite material, comprising the step of mixing components including the photoconversion material and the light-transmitting matrix resin. Specifically, the photoconversion material, by mass percentage, is 0.01–5% of the light-transmitting matrix resin, preferably 0.025–1%.

[0019] This invention does not particularly limit the method by which the photoconversion material is added to the transparent matrix resin. Common mixing methods in the art can be used, such as physical blending, melt blending, and solution blending. When using physical blending or melt blending, the blending process conditions are not particularly limited, as long as the photoconversion material and the transparent matrix resin are mixed uniformly. When using solution blending, the photoconversion material and the transparent matrix resin are added to a solvent, mixed uniformly, and then the solvent is removed to obtain the transparent polymer composite material. The solvent used in solution blending is not particularly limited, as long as it can dissolve the transparent matrix resin; for example, it can be alcohols, ketones, aromatics, chlorinated hydrocarbons, dioxane, tetrahydrofuran, etc. For polymers with initial flowability, such as epoxy resin before curing, the photoconversion material can be directly incorporated through physical blending.

[0020] According to the present invention, the method for preparing the photo-down conversion material includes: mixing polymer monomers including tetraphenylethylene derivatives and optional second polymer monomers, and reacting them under the action of an initiator to obtain the photo-down conversion material.

[0021] According to the present invention, the structural formula of the tetraphenylethylene derivative is as follows:

[0022]

[0023] In formula (Ⅲ), R′1 is one of a substituted or unsubstituted olefinic group having 2 to 20 carbon atoms, and R′2 to R′4 are each independently selected from H, OH, halogen, substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, substituted or unsubstituted aryl or aralkyl group having 6 to 30 carbon atoms; preferably, the tetraphenylethylene derivative is selected from at least one of tetraphenyl acrylate, (2-(4-((4-vinylbenzyl)oxy)phenyl)ethylene-1,1,2-triphenyl)ethylene, and [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene.

[0024]

[0025]

[0026] According to the present invention, the second polymerizing monomer is selected from at least one of styrene, vinylpyrrolidone, vinyl acetate, vinyl caprolactam, vinyl ethers, (meth)acrylic acid, (meth)acrylate, (meth)ethyl acrylate, (meth)acrylate, (meth)acrylate n-butyl acrylate, (meth)acrylate isobutyl acrylate, (meth)acrylate tert-butyl acrylate, (meth)acrylate lauryl acrylate, (meth)acrylate 2-ethylhexyl acrylate, (meth)acrylate octadecyl alcohol ester, (meth)acrylate cyclohexyl acrylate, (meth)acrylate isobornyl acrylate, (meth)acrylate benzyl acrylate, (meth)acrylate phenyl acrylate, and maleic anhydride.

[0027] According to the present invention, in the preparation method of the photo-down-conversion material: the tetraphenylethylene derivative accounts for 5 to 100 wt% of the total weight of the polymer monomers, preferably 10 to 100 wt%.

[0028] According to the present invention, in the method for preparing the optical down-conversion material:

[0029] An organic solvent is also added to the reaction, and the organic solvent is selected from at least one of dioxane, acetone, tetrahydrofuran, aromatic hydrocarbons, and chlorinated hydrocarbons, preferably from at least one of dioxane, toluene, xylene, trimethylbenzene, chloroform, dichloromethane, and tetrachloroethane.

[0030] The reaction is carried out under a protective gas atmosphere, for example, under a nitrogen atmosphere;

[0031] The reaction temperature is 25–110°C, preferably 65–100°C;

[0032] The reaction time is 6 to 48 hours, preferably 8 to 24 hours;

[0033] The reaction process further includes steps of precipitating the product, filtering, and drying. The precipitation method can be a commonly used precipitation method in the art, such as adding a poor solvent for the photoconversion material for precipitation. The drying operation can be carried out using commonly used drying equipment and drying conditions in the art.

[0034] According to the present invention, the synthesis method of the down-conversion material can be selected according to the type of monomer, including but not limited to living radical polymerization, atom transfer radical polymerization (ATRP), nitrile oxide stable radical polymerization (NMP), reversible addition-fragmentation chain transfer polymerization (RAFT), xanthate exchange radical polymerization (MADIX), iodine atom transfer radical polymerization (ITP), reversible catalytic chain transfer radical polymerization (RCTP), cobalt intermediate radical polymerization (CMRP), and organic heteroatom intermediate radical polymerization (OHMRP), preferably living radical polymerization or reversible addition-fragmentation chain transfer polymerization (RAFT). The initiator added during the reaction is not particularly limited and can be a commonly used initiator in the art. For example, the initiator is selected from at least one of peroxide initiators, azo initiators, and persulfate initiators, preferably at least one of benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), and potassium persulfate. The chain transfer agent used in reversible addition-fragmentation chain transfer polymerization (RAFT) is not particularly limited, and can be selected from at least one of 2-cyano-2-propyldodecyl trithiocarbonate, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, cyanomethyl(3,5-dimethyl-1H-pyrazole)-dithioester, 2'-cyanobutyl-2'-3,5-dimethylpyrazole-1-dithiocarbonate, 2-[[(butylthio)thiomethyl]thio]-propionic acid, 1,4-phenylenebis(methylene)bisdodecyl bis-trithiocarbonate, 4-cyano-4-(phenylthioformylthio)valerate, 2,2′-[methylthiobis(thio)]bis[2-methylpropionic acid], and benzyl n-butyl trithiocarbonate.

[0035] In this invention, when tetraphenylethylene derivatives are used as repeating units in the downconversion material polymer, the aggregates of tetraphenylethylene derivative units can achieve downconversion function within a single polymer molecule, thus ensuring luminescence intensity. When other copolymer units (Y repeating units in formula (Ⅰ)) in the downconversion material polymer have good compatibility with the light-transmitting matrix resin, the downconversion material polymer, when added as an additive to the light-transmitting matrix resin, can be uniformly dispersed within the main body of the light-transmitting matrix resin and maintain high luminescence intensity and stability.

[0036] A third objective of this invention is to provide an application of the above-mentioned transparent polymer composite material or the transparent polymer composite material obtained by the above preparation method in photovoltaic encapsulation films.

[0037] The transparent polymer composite material containing a light down-conversion material with light conversion function provided in this invention can be added to a photovoltaic encapsulation film to improve the responsiveness or external quantum efficiency (EQE) of the ultraviolet region of the photovoltaic module, thereby reducing the use of ultraviolet absorbers.

[0038] The beneficial effects of this invention are:

[0039] (1) In the light-transmitting polymer composite material provided by the present invention, the photo-down conversion material is a high molecular polymer, which has good compatibility with the light-transmitting matrix resin, and the photo-down conversion material can be uniformly dispersed in the matrix resin.

[0040] (2) In the prior art, commonly used photo-down-conversion fluorescent small molecules and inorganic quantum dots mostly have aggregation fluorescence quenching characteristics. Their luminescence efficiency and intensity are easily affected by the dispersion of small molecules / inorganic quantum dots in the resin matrix. The photo-down-conversion function of commonly used fluorescent small molecules / inorganic quantum dots has great instability in later use. The photo-down-conversion material used in this invention contains an aggregated tetraphenylethylene structure, which has aggregation-induced emission (AIE) characteristics. This photo-down-conversion material has high luminescence efficiency and more stable performance in the cluster state.

[0041] (3) The photostability of the down-conversion material used in this invention is significantly better than that of commonly used fluorescent small molecules. The photovoltaic encapsulation film containing this down-conversion material has a longer service life compared with other films with light conversion function in the prior art.

[0042] (4) The photoconversion material used in this invention has a maximum absorption value of incident radiation below 400 nm and a maximum emission value of radiation in a longer wavelength range of 400 to 900 nm. Therefore, when applied in photovoltaic modules, the photoconversion material will not cause loss of visible light (it does not absorb the visible light portion).

[0043] (5) The light-transmitting polymer composite material provided by the present invention can be used as a photovoltaic encapsulation film to effectively improve the efficiency and stability of photovoltaic modules.

[0044] (6) The light-transmitting polymer composite material provided by the present invention has a simple preparation process, low cost, and broad application prospects. Attached Figure Description

[0045] Figure 1 The image shows the translucent polymer composite material prepared in Example 1 under ultraviolet light irradiation.

[0046] Figure 2 The emission spectrum of the transparent polymer composite material prepared in Example 1 at an excitation wavelength of 375 nm is shown.

[0047] Figure 3 The external quantum efficiency (EQE) test results are shown for the transparent polymer composite material prepared in Example 9 and the transparent polymer composite material prepared in Comparative Example 1. Detailed Implementation

[0048] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0049] The testing instruments and conditions used in this embodiment are as follows:

[0050] Transmittance testing instrument: Shanghai Unico UV-4802 UV-Vis spectrophotometer.

[0051] Battery quantum efficiency testing: QE-R Guangyan Technology quantum efficiency testing system.

[0052] Emission spectrum: FLS1000 fluorescence spectrometer.

[0053] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0054] Example 1

[0055] Preparation of downconversion material A – Living radical polymerization:

[0056] Weigh 0.1g of [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene, 0.7g of styrene, 0.2g of maleic anhydride, 10mg of azobisisobutyronitrile, and 5g of xylene, and add them to a two-necked flask. Use a double-row tube system to remove all oxygen from the system and replace it with nitrogen. Stir the reaction at 95°C for 8 hours. After the reaction cools to room temperature, add ethanol to precipitate and filter out the solid. Wash and dry at 70°C to obtain the product, namely photoconversion material A, with a number average molecular weight of 12000.

[0057] The structural formula of photo-down-conversion material A is:

[0058]

[0059] Preparation of translucent polymer composites - solution method:

[0060] 3g of ethylene-vinyl acetate copolymer (model E282PV, manufacturer Hanwha Total) and 45mg of crosslinking agent 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane were dissolved in tetrahydrofuran. After the solid was fully dissolved, 9mg of the above-prepared photoconversion material A (0.3wt%) was added and stirred thoroughly. After the photoconversion agent was completely dissolved, the film was laid in a petri dish and then placed in a vacuum drying oven at 65°C overnight to remove the solvent. The final film was a light-transmitting polymer composite material containing photoconversion material.

[0061] The emission spectrum of the transparent polymer composite material measured using an FLS1000 fluorescence spectrometer is as follows: Figure 1 The fluorescence quantum yield of the above-mentioned transparent polymer composite film was measured to be 43% using this device.

[0062] The obtained transparent polymer composite film was sandwiched between two ultra-white glass sheets and hot-pressed at 140°C for 40 minutes. The test results showed that the transmittance of the film in the visible light region was 91%.

[0063] Example 2

[0064] Preparation of photo-down-conversion material B – Living radical polymerization:

[0065] Weigh 0.1 g of [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene, 0.6 g of methyl methacrylate, 0.2 g of styrene, 10 mg of azobisisobutyronitrile and 5 g of dioxane, and add them to a two-necked flask. Use a double-row tube system to remove all oxygen from the system and replace it with nitrogen. Stir the reaction at 85 °C for 9 hours. After the reaction cools to room temperature, add ethanol to precipitate and filter out the solid. Wash and dry at 70 °C to obtain the product, namely photoconversion material B, with a number average molecular weight of 18,000.

[0066] The structural formula of photo-down-conversion material B is:

[0067]

[0068] Preparation of translucent polymer composite materials:

[0069] The preparation process was the same as in Example 1, except that the added photoconversion material A was replaced with photoconversion material B. The fluorescence quantum yield of the resulting transparent polymer composite film was 46%, and after being sandwiched between two ultra-white glass sheets and hot-pressed at 140°C for 40 minutes, the transmittance of the film in the visible light region was 90%.

[0070] Example 3:

[0071] Preparation of downconversion material C – Reversible addition-fragmentation chain transfer polymerization (RAFT):

[0072] Weigh 0.4 g of [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene, 40 mg of chain transfer agent 2-cyano-2-propyldodecyl trithiocarbonate, 4 mg of azobisisobutyronitrile, and 2 ml of dioxane, and add them to a reaction flask and mix. Use a double-row tube system to remove all oxygen from the system and replace it with nitrogen. Stir the reaction at 75 °C for 24 hours. After the reaction cools to room temperature, add n-hexane to precipitate the solid and filter it out. Wash the solid and dry it at 70 °C overnight to obtain the product, namely photoconversion material C, with a number average molecular weight of 20,000.

[0073] The structural formula of the photo-down-conversion material C is:

[0074]

[0075] Preparation of translucent polymer composite materials:

[0076] The preparation process was the same as in Example 1, except that the added photoconversion material A was replaced with photoconversion material C. The fluorescence quantum yield of the resulting transparent polymer composite film was 68%, and after being sandwiched between two ultra-white glass sheets and hot-pressed at 140°C for 40 minutes, the transmittance of the film in the visible light region was 86%.

[0077] Examples 4-8

[0078] Preparation of translucent polymer composite materials:

[0079] Following the preparation process of Example 1, except that the added down-conversion material A accounted for 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of the matrix resin by weight, respectively. The resulting transparent polymer composite films had fluorescence quantum yields of 44%, 44%, 45%, 45%, and 43%, respectively. After being sandwiched between two ultra-white glass sheets and hot-pressed at 140°C for 40 minutes, the transmittance of the films in the visible light range was 90%, 90%, 89%, 87%, and 85%, respectively.

[0080] Example 9

[0081] Preparation of translucent polymer composites - physical blending method:

[0082] 10 mg of photoconversion material A was dissolved in 1 ml of tetrahydrofuran. After complete dissolution, the solution was added dropwise to 20 g of uncured epoxy resin solution. The epoxy resin solution was placed in a 65°C oil bath and stirred for 20 minutes, followed by sonication for 30 minutes to remove the solvent and fully disperse the photoconversion material A, resulting in a photoconversion agent-epoxy resin mixture. The resulting mixture was placed in a vacuum degassing machine, evacuated, and stirred for 3–5 minutes. The mixture was then poured into a petri dish for film deposition and cured with a UV curing lamp for 2 minutes to obtain a translucent polymer composite film containing the photoconversion material.

[0083] The resulting transparent polymer composite film has a fluorescence quantum yield of 46% and a visible light transmittance of 93%.

[0084] Example 10

[0085] Preparation of translucent polymer composites - melt blending method:

[0086] Ten parts by weight of photoconversion material A and 90 parts by weight of ethylene-vinyl acetate copolymer (model E282PV, manufactured by Hanwha Total) were mixed uniformly at a melt flow rate of 20 g / 10 min. The mixture was then extruded through a screw extruder at 80°C and 150 r / min and water-cooled to granulate, thus preparing a photoconversion material masterbatch. Five parts by weight of the photoconversion material masterbatch, 190 parts by weight of ethylene-vinyl acetate copolymer, 2.85 parts by weight of crosslinking agent 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, 0.3 parts by weight of N,N'-m-phenylbismaleimide co-crosslinking agent, and 0.8 parts by weight of tris(nonylphenyl) phosphite antioxidant were mixed uniformly and then added to a casting machine for plasticizing extrusion at 80°C. The resulting film was stretched, drawn, and wound to form a transparent polymer composite film with a thickness of 0.8 mm. The fluorescence quantum yield of the obtained film was 45%, and the transmittance of the film in the visible light region was 89%.

[0087] Example 11

[0088] Preparation of translucent polymer composites - solution blending method:

[0089] 10 mg of photoconversion material A was dissolved in 1 ml of tetrahydrofuran and added dropwise to a reaction flask containing 10 ml of methyl methacrylate. 50 mg of photoinitiator trimethylbenzoyl-diphenylphosphine oxide (TPO) was added to the reaction flask, and the flask was sonicated for 30 minutes to ensure thorough dispersion of the photoinitiator and photoconversion agent. The liquid from the reaction flask was then poured into a petri dish for film deposition and cured under UV light for 2 hours to obtain a transparent polymethyl methacrylate film containing the photoconversion material. The resulting transparent polymer composite film exhibited a fluorescence quantum yield of 46% and a visible light transmittance of 91%.

[0090] Comparative Example 1

[0091] An epoxy resin solution without added photoconversion material was used as Comparative Example 1.

[0092] The epoxy resin solution without photoconversion material in Comparative Example 1 (blank epoxy resin solution) and the epoxy resin mixture containing photoconversion material obtained in Example 9 were uniformly spread on top of the silicon solar cell. The epoxy resins were cured by irradiation with a UV lamp for 2 minutes. The results were displayed according to the QE-R spectral response test system (see...). Figure 3Example 9 shows that the silicon cell containing the photo-down-conversion material has a higher external quantum efficiency (EQE) and a higher ultraviolet responsivity.

[0093] Comparative Example 2

[0094] 3g of ethylene-vinyl acetate copolymer (matrix resin) (model E282PV, manufacturer: Hanwha Total) and 45mg of crosslinking agent 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane were dissolved in tetrahydrofuran. After the solid was fully dissolved, 9mg of [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene (tetraphenylethylene derivative monomer) was added and stirred thoroughly. After complete dissolution, the mixture was spread into a petri dish and then dried overnight at 65°C in a vacuum drying oven to remove the solvent. The resulting film was a transparent polymer material containing a tetraphenylethylene derivative monomer. The fluorescence quantum yield of the film was measured to be less than 18% using an FLS1000. After hot pressing at 140°C for 40 minutes, the visible light transmittance of the resulting transparent polymer material film was less than 86%. In contrast, the transparent polymer composite film obtained in Example 1 using photoconversion material A had higher luminous quantum efficiency and transmittance.

Claims

1. A light-transmitting polymer composite material, comprising a photodown-conversion material and a light-transmitting matrix resin, wherein the photodown-conversion material is a polymer with a tetraphenylethylene side chain, and by mass percentage, the photodown-conversion material comprises 0.01-5% of the light-transmitting matrix resin; the light-transmitting matrix resin is selected from at least one of ethylene-vinyl acetate copolymer, polymethyl methacrylate, and epoxy resin, and the structural formula of the photodown-conversion material is as follows: In formula (I) or formula (II), R1 is independently a substituted or unsubstituted alkyl group having 2 to 20 carbon atoms, R2 to R4 are independently selected from H, OH, halogen, substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and substituted or unsubstituted aryl or aralkyl group having 6 to 30 carbon atoms, and Y is a derivatizing group of the second polymerizing monomer, wherein the second polymerizing monomer is selected from styrene, vinylpyrrolidone, vinyl acetate, vinyl caprolactam, and (meth)acrylic acid. The material comprises at least one of the following: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, phenyl methacrylate, and maleic anhydride; wherein the number average molecular weight of the photoconversion material is 5000 to 50000.

2. The light-transmitting polymer composite material according to claim 1, characterized in that, The number-average molecular weight of the photo-down-conversion material is 10,000 to 30,000.

3. The light-transmitting polymer composite material according to claim 1, characterized in that, The photoconversion material comprises, by weight percentage, 0.025% to 1% of the light-transmitting matrix resin; and / or, The light transmittance of the light-transmitting polymer composite material is 70-99%.

4. The light-transmitting polymer composite material according to claim 3, characterized in that, The light transmittance of the light-transmitting polymer composite material is 80-95%.

5. A method for preparing the light-transmitting polymer composite material according to any one of claims 1 to 4, comprising the step of mixing components including the light down-conversion material and the light-transmitting matrix resin.

6. The preparation method according to claim 5, characterized in that, The photoconversion material is 0.01 to 5% of the light-transmitting matrix resin by weight percentage.

7. The preparation method according to claim 6, characterized in that, The photoconversion material is 0.025 to 1% of the light-transmitting matrix resin by weight percentage.

8. The preparation method according to claim 5, characterized in that, The method for preparing the photo-down conversion material includes: mixing polymer monomers, including tetraphenylethylene derivatives and optional second polymer monomers, and reacting them under the action of an initiator to obtain the photo-down conversion material.

9. The preparation method according to claim 8, characterized in that, The structural formula of the tetraphenylethylene derivative is: In formula (Ⅲ), R′1 is one of a substituted or unsubstituted olefinic group having 2 to 20 carbon atoms, and R′2 to R′4 are independently selected from H, OH, halogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and a substituted or unsubstituted aryl or aralkyl group having 6 to 30 carbon atoms; and / or, The second polymerization monomer is selected from at least one of styrene, vinylpyrrolidone, vinyl acetate, vinyl caprolactam, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, phenyl methacrylate, and maleic anhydride; and / or, The initiator is selected from at least one of peroxide initiators, azo initiators, and persulfate initiators; and / or, The tetraphenylethylene derivatives account for 5 to 100 wt% of the total weight of the polymer monomers.

10. The preparation method according to claim 9, characterized in that, The tetraphenylethylene derivative is selected from at least one of tetraphenyl acrylate, (2-(4-((4-vinylbenzyl)oxy)phenyl)ethylene-1,1,2-triphenyl)ethylene, and [1-(4-vinylphenyl)-1,2,2-triphenyl]ethylene; and / or, The initiator is selected from at least one of benzoyl peroxide, azobisisobutyronitrile, and potassium persulfate; and / or, The tetraphenylethylene derivative accounts for 10 to 100 wt% of the total weight of the polymer monomers.

11. The preparation method according to claim 8, characterized in that, The reaction also includes the addition of an organic solvent, which is selected from at least one of dioxane, acetone, tetrahydrofuran, aromatic hydrocarbons, and chlorinated hydrocarbons; and / or, The reaction is carried out under a protective gas atmosphere; and / or, The reaction temperature is 25–110°C; and / or, The reaction time is 6–48 h; and / or, The reaction also includes steps of precipitating the product, filtering it, and drying it.

12. The preparation method according to claim 11, characterized in that, The organic solvent is selected from at least one of dioxane, toluene, xylene, trimethylbenzene, chloroform, dichloromethane, and tetrachloroethane; and / or, The reaction temperature is 65–100°C; and / or, The reaction time is 8 to 24 hours.

13. The application of a light-transmitting polymer composite material according to any one of claims 1 to 4 or a light-transmitting polymer composite material obtained by the preparation method according to any one of claims 5 to 12 in a photovoltaic encapsulation film.

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