High-reliability light conversion adhesive film and preparation method thereof

Abstract

The invention relates to the technical field of photovoltaic adhesive films, in particular to a high-reliability light conversion adhesive film and a preparation method thereof. The high-reliability light conversion adhesive film comprises a polymer matrix and a light conversion material dispersed in the polymer matrix, wherein the polymer matrix is at least one of an ethylene-vinyl acetate copolymer, a polyolefin elastomer and polyacrylate; the light conversion material is nanoparticles coated with an inner layer of a light stabilizer and an outer layer of double-layer SiO2; the double-layer SiO2 comprises a compact SiO2 inner layer of which the density is greater than 2.2 g / cm < 2 > and a porous SiO2 outer layer of which the porosity is 20-40% and the density is 1.5-1.8 g / cm < 2 >, and the surface of the porous SiO2 outer layer is grafted with an amino silane or fluorosilane coupling agent; the average light transmittance of the double-layer SiO2 in the wave band of 250-400 nm is larger than or equal to 90%. According to the adhesive film, double SiO2 inorganic layers are adopted to coat the whole surface of the light conversion material, so that the problems of migration inhibition and oxidation resistance improvement of the light conversion material are solved, and meanwhile, the light transmittance of the adhesive film is not influenced. The preparation method is suitable for an existing adhesive film production line, and equipment does not need to be newly added.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic encapsulant films, and in particular to a light conversion encapsulant film with high reliability and a preparation method thereof. Background Art

[0002] At present, TOPcon cell modules and HJT cell modules have become the mainstream products of crystalline silicon cell modules. However, the passivation technologies of TOPcon cells and HJT cells rely on the stability of Si-H bonds. However, high-intensity UV irradiation will directly damage the Si-H groups of the cells, resulting in a decline in the passivation performance of the cells, and ultimately causing power attenuation of the cell modules. The existing technology mainly protects the cells through UV light conversion encapsulant films. Conventional UV light conversion encapsulant film technologies are often single materials or simply compounded products, and have the following defects: a. Under high temperature or long-term UV irradiation, surface defects of the light conversion materials (such as perovskite quantum dots, rare earth phosphors) cause accelerated ion migration, leading to a sudden drop in the light conversion efficiency; b. The peroxide crosslinking agent (such as DCP) used in the process of film processing will oxidize the molecular structure of the light conversion materials, resulting in a decrease in the light conversion efficiency by more than 30%; c. Direct addition of inorganic barrier materials (such as talcum powder) will reduce the light transmittance; d. Traditional coating materials (such as epoxy resin) chemically bond with the polymer matrix, causing an increase in the crosslinking density, resulting in embrittlement of the material, which may block UV or affect the light transmittance.

[0003] The patent with the publication number CN118813145B discloses an anti-migration light conversion encapsulant film, a preparation method thereof, and a photovoltaic module. It uses a polymethyl methacrylate layer coated outside the organic light conversion agent to slow down the migration of the organic light conversion agent in the film, thereby improving the anti-ultraviolet light aging performance of the photovoltaic module and slowing down its power attenuation under ultraviolet light; however, it uses a polymer material for coating, and there are problems such as insufficient photo-thermal stability of the organic coating layer and coating failure during high-temperature processing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to solve the problems of insufficient photo-thermal stability of the organic coating layer and coating failure during high-temperature processing existing in the prior art in the above background art, and to provide a light conversion encapsulant film with high reliability, which uses a double-layer SiO2 inorganic layer to fully coat the light conversion materials, solves the inhibition of light conversion material migration and the improvement of antioxidant performance, and does not affect the light transmittance of the film.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a light conversion encapsulant film with high reliability, including: A polymer matrix, where the polymer matrix is at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, and polyacrylate; A light conversion material dispersed in the polymer matrix, the light conversion material being nanoparticles coated with an inner layer of a light stabilizer and a double-layer SiO2 outer layer; The double-layer SiO2 includes: A dense SiO2 inner layer with a density > 2.2 g / cm³; A porous SiO2 outer layer with a porosity of 20 - 40% and a density of 1.5 - 1.8 g / cm³, and the surface is grafted with an amino silane or fluoro silane coupling agent; The average light transmittance of the double-layer SiO2 in the 250 - 400 nm band is ≥ 90%.

[0006] The polymer matrix provides the basic mechanical properties and light transmittance of the adhesive film. The dense SiO2 inner layer isolates water, oxygen and free radicals, protecting the light conversion material from chemical corrosion. The porous SiO2 outer layer relieves the interfacial stress, avoiding cross-linking embrittlement of the adhesive film. The surface-grafted coupling agent enhances the compatibility with the polymer matrix. The average light transmittance of the double-layer SiO2 in the 250 - 400 nm band is ≥ 90%, that is, high UV light transmittance, ensuring efficient absorption / conversion of UV light by the light conversion material and reducing the damage to the battery passivation layer.

[0007] According to an embodiment of the present invention, the light conversion material is at least one of rare earth complexes, quantum dots, and organic fluorescent dyes. With this setting, the spectral response range is broadened.

[0008] According to an embodiment of the present invention, the light conversion material is NaYF4:Yb³⁺ / Er³⁺ phosphor. With this setting, the conversion efficiency is specifically improved.

[0009] According to an embodiment of the present invention, the light stabilizer is hindered amine light stabilizer 770, and the dosage is 0.5 - 3% of the mass of the light conversion material. With this setting, the degradation of the light conversion material is inhibited, and the outdoor life of the adhesive film is prolonged.

[0010] According to an embodiment of the present invention, the thickness of the dense SiO2 inner layer is 30 - 50 nm, and the thickness of the porous SiO2 outer layer is 20 - 30 nm. With this setting, the protection and stress buffering are balanced, avoiding the influence of too thick coating on the light transmittance.

[0011] According to an embodiment of the present invention, the fluoro silane coupling agent grafted on the surface of the porous SiO2 outer layer is perfluorooctyltriethoxysilane. With this setting, hydrophobicity is imparted to block the penetration of water vapor.

[0012] There is also provided a method for preparing the high-reliability light conversion adhesive film as described in the above solution, including the following steps: S1. Pretreatment of the light conversion material: Mix the light stabilizer and the light conversion material in a mass ratio of 0.5 - 3%, and compound by ball milling or ultrasonic dispersion, and then dry; S2. Double-layer SiO2 coating: A dense SiO2 inner layer is coated on the surface of the light conversion material after pretreatment by the sol-gel method; SiO2 nanoparticles are adsorbed on the surface of the inner layer by the suspension coating method, and a porous SiO2 outer layer is formed after vacuum drying; S3. Surface hydrophobic modification: The material obtained in step S2 is immersed in a solution containing a fluorosilane coupling agent for reaction and then dried; S4. Melt blending: The coated light conversion material and the polymer matrix are melt blended and granulated, and then extruded and cast into a film.

[0013] Pretreatment with a light stabilizer to uniformly coat the light conversion material and prevent agglomeration during subsequent processing; coating a dense SiO2 inner layer by the sol-gel method to form a defect-free coating by chemical bonding, forming a porous SiO2 outer layer by the suspension coating method, and forming a buffer layer by physically adsorbing nanoparticles; surface modification with fluorosilane to improve hydrophobicity and reduce interfacial side reactions; melt blending to ensure uniform dispersion of the light conversion material and the film has no optical defects.

[0014] According to an embodiment of the present invention, in step S2, the sol-gel method uses a silane precursor to hydrolyze under acidic or alkaline conditions, the reaction temperature is 40-60 °C, and the time is 2-4 hours; In step S2, the suspension coating method uses CTAB as a dispersant, the particle size of the SiO2 nanoparticles is 20-100 nm, and the number of adsorption-drying cycles is ≥3 times.

[0015] With such limitations, the dense layer has no cracks, the porosity of the porous layer is controllable, and CTAB improves the particle dispersibility.

[0016] According to an embodiment of the present invention, in step S3, the concentration of the fluorosilane coupling agent solution is 0.5-2 wt%, the reaction temperature is 50-70 °C, and the time is 1-3 hours.

[0017] With such limitations, the grafting rate is significantly increased, and the hydrophobic layer is stable and does not fall off.

[0018] According to an embodiment of the present invention, in step S4, a peroxide initiator, a co-crosslinking agent, and an antioxidant are added during melt blending, the kneading temperature is 90-110 °C, and the extrusion temperature is 90-120 °C.

[0019] With such limitations, the crosslinking degree of the film is significantly increased, and the balance between mechanical strength and light transmittance is achieved.

[0020] Advantages of the present invention: (1) Dual protection mechanism: The light stabilizer inhibits photooxidation by capturing free radicals, increasing the stability of the light conversion material; the double-layer structure SiO2 layer shell isolates oxygen, moisture, and free radical attacks, synergistically reducing the thermal oxidation and crosslinking degradation of the light conversion material; (2) No UV blocking property: The energy band structure design of the double-layer SiO2 ensures that it absorbs as little as possible in the UV band (such as 250 - 400 nm), allowing UV light to penetrate efficiently and excite the light conversion material; The dense SiO2 inner layer (with a thickness of 5 - 50 nm) directly coats the light conversion material particles, filling surface defects. The dense SiO2 inner layer blocks the penetration of more than 98% of the small molecules decomposed by DCP, isolating oxygen, moisture, and free radical attacks, and enhancing thermal stability and chemical stability; The porous / low-density SiO2 outer layer (with a thickness of 10 - 100 nm) provides a buffering effect, dispersing external mechanical or thermal stress and reducing the mobility of the light conversion particles; it has high transparency (UV transmittance > 95%), avoiding interference with the excitation and emission spectra of the light conversion material; (3) Anti-crosslinking reaction design: The surface of the porous SiO2 outer layer is modified with inert groups (such as silane coupling agents) to reduce chemical bonding with the polymer matrix and inhibit the embrittlement of the material caused by crosslinking; (4) Process compatibility: The preparation method of the present invention is compatible with existing film production lines without the need for new equipment. Brief Description of the Drawings

[0021] The present invention will be further described below in conjunction with the drawings and embodiments.

[0022] Figure 1 It is a schematic structural diagram of the highly reliable light conversion film in the first embodiment of the present invention.

[0023] Figure 2 It is a schematic structural diagram of the light conversion material in the highly reliable light conversion film in the first embodiment of the present invention.

[0024] In the figure: 1, polymer matrix; 2, light conversion material; 3, light stabilizer; 4, double-layer SiO2; 41, dense SiO2 inner layer; 42, porous SiO2 outer layer. Detailed Embodiments

[0025] The present invention will now be further described in detail in conjunction with the drawings. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic manner, so they only show the components related to the present invention.

[0026] First Embodiment As Figure 1 and Figure 2As shown in the figure, a high-reliability light conversion film includes a polymer matrix 1 and a light conversion material 2 dispersed in the polymer matrix 1. Among them, the polymer matrix 1 is at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, and polyacrylate, and the light conversion material 2 is nanoparticles coated with a light stabilizer 3 on the inner layer and a double-layer SiO2 4 on the outer layer. The double-layer SiO2 4 includes a dense SiO2 inner layer 41 with a density > 2.2 g / cm³ and a porous SiO2 outer layer 42 with a porosity of 20 - 40% and a density of 1.5 - 1.8 g / cm³. The surface of the porous SiO2 outer layer 42 is grafted with an amino silane or fluoro silane coupling agent; the average light transmittance of the double-layer SiO2 4 in the 250 - 400 nm band is ≥ 90%.

[0027] The preparation method of the above high-reliability light conversion film specifically includes the following steps: Step 1. Coating the light conversion material 2 with SiO2: 1.1. Pretreatment of the light conversion material 2: Mix 10 g of NaYF4: 10 g Yb³⁺ / Er³⁺ phosphor, 0.5 g of light stabilizer 770 with a concentration of 5 wt%, and 50 ml of ethanol, ball mill for 2 hours (300 rpm), and vacuum dry at 80 °C for 12 hours; 1.2. Coating with SiO2: 1.21. Inner layer coating (sol-gel method): Disperse 10 g of NaYF4:Yb³⁺ / Er³⁺ phosphor pretreated with light stabilizer 770 in 200 mL of ethanol solution containing 0.1 wt% PVP, and ultrasonically treat for 30 min to fully dissolve; after adding silane, use acidic (HCL) or alkaline (ammonia water) catalytic hydrolysis for coating, stir at 40 °C for 4 hours to obtain nano-sphere particles; centrifuge and wash to obtain quantum dots coated with a dense SiO2 inner layer 41 with a thickness of 30 - 50 nm; 1.22. Outer layer coating (suspension coating method): Disperse 5 g of SiO2 nanoparticles with a particle size of 50 nm and 0.5 g of CTAB in 100 mL of isopropanol, and ultrasonically treat for 1 hour; add the inner layer coated phosphor, ultrasonically disperse at 100 W for 30 min, vacuum filter and dry; repeat the adsorption-drying process 3 times, and vacuum dry at 80 - 150 °C for 2 hours to obtain a porous SiO2 outer layer 42 with a thickness of 20 - 30 nm and a porosity of 35%; 1.3. Surface modification: Immerse the sample in an ethanol solution of 1 wt% perfluorooctyltriethoxysilane, react at 60 °C for 2 hours, and dry to obtain a hydrophobic outer layer; Step 2. Pretreatment of the light conversion material 2: Ultrasonically disperse the double-layer SiO2 4 coated NaYF4:Yb³⁺ / Er³⁺ quantum dots and KH-550 (mass ratio 1:0.05) in ethanol for 30 minutes, and dry for standby.

[0028] Step 3. Melting and blending: Mix 100 parts of EVA particles with 0.1 - 3 parts of the coated light conversion material in a mixer at a temperature of 90 - 110 °C and a rotation speed of 50 - 100 rpm. Then add 1 - 1.5 parts by weight of peroxide initiator, 0.5 - 10 parts by weight of co-crosslinking agent, 0.1 - 5 parts by weight of tackifier, and 0.03 - 5 parts by weight of antioxidant to the mixer and knead at 100 °C for 15 minutes. Extrude into a film through a screw extruder (temperature range 90 - 120 °C) with a thickness of 0.5 mm.

[0029] The inner sol-gel layer in Step 1.21 forms a dense SiO2 layer through chemical bonding to isolate oxygen, moisture, and free radical attacks, enhancing thermal stability and chemical stability. The outer suspension coating layer in Step 1.22 forms a loose SiO2 layer through physical adsorption or electrostatic interaction to optimize particle dispersion and relieve interfacial stress, avoiding crosslinking embrittlement of the rubber film.

[0030] In Step 1.3, the surface of the double-layer SiO2 is modified with a silane coupling agent (such as KH-550), which can replace the hydroxyl groups on its surface with inert groups such as alkyl and amino groups. These groups have low chemical affinity with the polymer matrix, thus reducing the interfacial bonding strength and avoiding excessive crosslinking. The outer modified inert groups (such as -CH3) inhibit side reactions with rubber film additives (such as peroxides).

[0031] After laminating and crosslinking the light conversion rubber film prepared by the above preparation method, the crosslinking degree is 72.3%, the light transmittance in the 300 - 380 nm band is 7%, and the light transmittance in the 380 - 780 nm band is 91.5%. When applied to HJT modules, the initial power generation is increased by 0.3% compared with the rubber film of the same formula without the light conversion material 2. After damp heat aging, the power generation of this module decays by 0.5%, and after UV aging, the power generation decays by 0.2%.

[0032] Comparative Example 1 The difference from Example 1 is that the light conversion material 2 is not coated.

[0033] Comparative Example 2 The difference from Example 1 is that the light conversion material 2 is coated with a single layer of SiO2, and only the sol-gel method is used to obtain a SiO2 layer with a thickness of 50 nm.

[0034] Comparative Example 3 The difference from Example 1 is that the light conversion material 2 is coated with TiO2, and a 50 nm thick, UV-absorbing TiO2 layer is prepared by the sol-gel method.

[0035] Compare the performance of Comparative Examples 1 - 3 with that of Example 1, as shown in the following table: Performance Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Visible light transmittance (380 - 780nm) 91.5% 91% (scattering caused by fluorescent agent aggregation) 91.2% 91% PLQY (photoluminescence quantum yield) 94.7% 87.9% 95% <![CDATA[62.4% (strong UV absorption of TiO2)]]> Degree of crosslinking of the glue film 72.3% 83.2% 78.9% (surface hydroxyl groups not passivated) <![CDATA[82.1% (Side reactions initiated by surface active sites of TiO2)]]> Power improvement of the module compared with the glue film of the same formula without the light conversion agent 0.3% 0.1% 0.3% -0.5% Power attenuation of the module after damp heat aging 0.5% 5% 3% 3% Power attenuation after UV aging 1.2% 5% 2% 2% As can be seen from the above table information, the double-layer SiO2 coating in Example 1 significantly improves the light transmittance (>91%) while avoiding the UV absorption defect of TiO2; the porous SiO2 outer layer structure and hydrophobic modification block the penetration of water and oxygen and the interfacial reaction, and the power attenuation of the module after damp heat aging is the smallest; surface passivation inhibits the cross-linking of the adhesive film, and the cross-linking degree is stable at 70-75%, which is better than Comparative Examples 1-3.

[0036] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A light conversion film with high reliability, characterized in that, Comprising: A polymer matrix (1), where the polymer matrix (1) is at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, and polyacrylate; A light conversion material (2) dispersed in the polymer matrix (1), where the light conversion material (2) is nanoparticles coated with a light stabilizer (3) on the inner layer and double-layer SiO2 (4) on the outer layer; The double-layer SiO2 (4) includes: A dense SiO2 inner layer (41) with a density > 2.2 g / cm³; A porous SiO2 outer layer (42) with a porosity of 20 - 40% and a density of 1.5 - 1.8 g / cm³, and the surface is grafted with an amino-silane or fluoro-silane coupling agent; The average light transmittance of the double-layer SiO2 (4) in the 250 - 400 nm wavelength band is ≥ 90%.

2. The high-reliability light conversion film according to claim 1, wherein: The light conversion material (2) is at least one of rare earth complexes, quantum dots, and organic fluorescent dyes.

3. The light conversion adhesive film with high reliability according to claim 2, characterized in that: The light conversion material (2) is NaYF4:Yb³⁺ / Er³⁺ phosphor.

4. The light conversion adhesive film with high reliability according to claim 1, wherein: The light stabilizer (3) is a hindered amine light stabilizer 770, and the dosage is 0.5 - 3% of the mass of the light conversion material (2).

5. The light conversion adhesive film with high reliability according to claim 1, wherein: The thickness of the dense SiO2 inner layer (41) is 30 - 50 nm, and the thickness of the porous SiO2 outer layer (42) is 20 - 30 nm.

6. The light conversion adhesive film with high reliability according to claim 1, characterized in that: The fluoro-silane coupling agent grafted on the surface of the porous SiO2 outer layer (42) is perfluorooctyltriethoxysilane.

7. A method for preparing a light conversion adhesive film with high reliability according to any one of claims 1 to 6, characterized in that, Including the following steps: S1. Pretreatment of the light conversion material (2): Mix the light stabilizer (3) and the light conversion material (2) in a mass ratio of 0.5 - 3%, and compound by ball milling or ultrasonic dispersion, then dry; S2. Coating with double-layer SiO2 (4): Use the sol-gel method to coat the dense SiO2 inner layer (41) on the surface of the pretreated light conversion material (2); Use the suspension coating method to adsorb SiO2 nanoparticles on the inner layer surface, and form the porous SiO2 outer layer (42) after vacuum drying; S3. Surface hydrophobic modification: Immerse the material obtained in step S2 into a solution containing a fluoro-silane coupling agent for reaction, then dry; S4. Melt blending: Melt blend and pelletize the coated light conversion material (2) and the polymer matrix (1), and extrude and cast into a film.

8. The method for preparing the highly reliable light conversion adhesive film according to claim 7, characterized in that: In step S2, the sol-gel method uses a silane precursor to hydrolyze under acidic or alkaline conditions, the reaction temperature is 40 - 60 °C, and the time is 2 - 4 hours; In step S2, the suspension coating method uses CTAB as a dispersant, the particle size of the SiO2 nanoparticles is 20 - 100 nm, and the number of adsorption-drying cycles is ≥ 3 times.

9. The preparation method of the light conversion adhesive film with high reliability according to claim 7, wherein: In step S3, the concentration of the fluoro-silane coupling agent solution is 0.5 - 2 wt%, the reaction temperature is 50 - 70 °C, and the time is 1 - 3 hours.

10. The preparation method of the light conversion adhesive film with high reliability according to claim 7, wherein: In step S4, a peroxide initiator, a co-crosslinking agent, and an antioxidant are added during melt blending, the internal mixer temperature is 90 - 110 °C, and the extrusion temperature is 90 - 120 °C.

Images