High-performance 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. A high-reliability light conversion adhesive film comprises a polymer matrix and a light conversion material composite layer dispersed in the polymer matrix, the light conversion material composite layer accounts for 0.1-5wt% of the total mass of the adhesive film, the light conversion material composite layer comprises a core layer and a coating layer, the core layer is made of a light conversion material, and the coating layer is made of a coating material. The coating layer is of a double-layer structure composed of a light stabilizer 770 molecule anchoring layer and a styryl copolymer outer layer. The preparation method of the high-reliability light conversion adhesive film comprises the steps of molecule anchoring, in-situ polymerization and blending film forming. Through a synergistic process of light stabilizer molecular interface passivation and styrene in-situ polymerization coating, the stability of a light conversion material under damp heat, crosslinking and ultraviolet radiation is remarkably improved while the light transmittance of the adhesive film is maintained, and particularly, the problem of efficiency attenuation caused by easy hydrolysis and thermal oxidation of perovskite quantum dots in the EVA / POE adhesive film is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic encapsulant films, and in particular to a high-reliability light conversion encapsulant film 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 technology of existing TOPcon cells and HJT cells depends 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 passivation performance and ultimately causing power attenuation of the cell modules. The prior art 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. The light stabilizer is directly blended, which is easy to migrate and agglomerate, and cannot effectively protect the surface defects of the light conversion material; b. The barrier efficiency of traditional single-layer coating (such as using TiO2) is low and the light transmittance decreases; c. The simple polymer coating layer lacks the ability to capture free radicals and cannot inhibit deep oxidation. When the photovoltaic encapsulant film is crosslinked and cured (the temperature is 140-160 °C), free radicals attack the surface of the light conversion material, resulting in a decline in quantum efficiency; d. Light conversion materials such as perovskite quantum dots are sensitive to humidity and heat. Oxidation on the surface of the light conversion material causes yellowing of the encapsulant film, reducing the power output of the module. Moreover, the existing coating technologies cannot simultaneously solve the problems of water and oxygen penetration and interfacial stress. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to solve the problems in the prior art in the above background art that the light conversion material has poor stability under humidity and heat, crosslinking and ultraviolet irradiation, and cannot simultaneously solve the problems of water and oxygen penetration and interfacial stress, and to provide a high-reliability light conversion encapsulant film. Through the synergistic process of molecular interface passivation of the light stabilizer and in-situ polymerization coating of styrene, while maintaining the light transmittance of the encapsulant film, the stability of the light conversion material under humidity and heat, crosslinking and ultraviolet irradiation is significantly improved, especially solving the problem of efficiency decay caused by easy hydrolysis and thermal oxidation of perovskite quantum dots in EVA / POE encapsulant films.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a high-reliability light conversion encapsulant film, which includes a polymer matrix and a light conversion material composite layer dispersed in the polymer matrix. The light conversion material composite layer accounts for 0.1-5 wt% of the total mass of the encapsulant film, and it includes a core layer and a coating layer. The core layer is a light conversion material, and the coating layer is a double-layer structure composed of a light stabilizer 770 molecular anchoring layer and a styrene-based copolymer outer layer.

[0005] The light conversion material composite layer accounts for 0.1 - 5 wt% of the total mass of the adhesive film, balancing the light conversion efficiency and the mechanical properties of the adhesive film. The light stabilizer 770 selectively modifies the surface defects of the light conversion material through hydrogen bonds / coordination bonds. Meanwhile, the hindered group (NH - O) of the light stabilizer 770 dynamically captures free radicals, inhibiting deep oxidation. The outer layer of the styrene copolymer has no UV - absorbing groups, and in - situ polymerization of styrene forms an amorphous highly transparent layer, ensuring that the light transmittance of the adhesive film is ≥91%.

[0006] According to an embodiment of the present invention, the polymer matrix is at least one of ethylene - vinyl acetate copolymer, polyolefin elastomer, or polyacrylate.

[0007] Ethylene - vinyl acetate copolymer (EVA) has high light transmittance (visible light transmittance > 90%) and flexibility, and is suitable for the lamination process of photovoltaic modules; polyolefin elastomer (POE) has anti - PID (potential induced degradation) performance, extending the life of the module; polyacrylate can resist damp - heat aging.

[0008] According to an embodiment of the present invention, the light conversion material is at least one of rare - earth complexes, quantum dots, or organic fluorescent dyes, and the particle size is 2 - 30 nm. The emission peak of the rare - earth complex is 530 nm, and the quantum dots have tunable emission (400 - 700 nm), both of which can achieve broad - spectrum response; the nano - scale particle size (< 30 nm) avoids Rayleigh scattering and maintains the transparency of the adhesive film.

[0009] According to an embodiment of the present invention, the quantum dots are perovskite quantum dots. Perovskite quantum dots have high quantum efficiency and can significantly improve the power gain of the module.

[0010] According to an embodiment of the present invention, the thickness of the molecular anchoring layer of the light stabilizer 770 is 2 - 5 nm, and the thickness of the outer layer of the styrene copolymer is 50 - 150 nm. The 2 - 5 nm light stabilizer layer fully covers the surface defect sites of the light conversion material, and the 50 - 150 nm styrene layer is densely cross - linked, reducing the water and oxygen permeability.

[0011] According to an embodiment of the present invention, the styrene copolymer is styrene monomer or styrene - butyl acrylate copolymer. Styrene monomer has good optical transparency and processing performance, and the flexible chain segment of butyl acrylate improves the processing performance, is fully compatible with EVA, and reduces the phase separation of the material layer.

[0012] There is also provided a preparation method of the high - reliability light conversion adhesive film according to the above - mentioned scheme, including the following steps: S1. Molecular anchoring: Dispersing the light conversion material in an ethanol solution containing light stabilizer 770, and performing ultrasonic treatment at 40 - 60 °C for 1 - 3 h. The dosage of the light stabilizer is 0.5 - 3% of the mass of the light conversion material; S2. In-situ polymerization: Mix the product in step S1 with styrene monomer, control the swelling degree at 30 - 50%, and carry out gradient temperature rise polymerization under an inert atmosphere to form a polystyrene coating layer with a crosslinking degree of 10 - 20%. S3. Co-blending and film forming: Melt-blend the coated light conversion material with a polymer matrix, add a peroxide initiator, a co-crosslinking agent, a tackifier, and an antioxidant, and then extrude and cast to form a film.

[0013] Step S1 is molecular anchoring, and ultrasonic assistance promotes the uniform adsorption of light stabilizer 770 to avoid agglomeration; in the in-situ polymerization of step S2, gradient temperature rise polymerization forms a defect-free coating layer, and a crosslinking degree of 10 - 20% balances the barrier property and flexibility; in the co-blending and film forming of step S3, low-temperature extrusion (80 - 120 °C) prevents the thermal degradation of quantum dots, and a film thickness of 0.5 mm adapts to the component encapsulation process.

[0014] According to an embodiment of the present invention, the in-situ polymerization in step S2 uses a redox initiation system, including ammonium persulfate and ascorbic acid, and the molar ratio of the two is 1:1.2. Using the ammonium persulfate - ascorbic acid redox system, polymerization can be initiated at 50 °C, avoiding high-temperature damage to the light conversion material; ascorbic acid acts as a radical scavenger, reducing unreacted monomers and eliminating ultraviolet absorption.

[0015] According to an embodiment of the present invention, the gradient temperature rise polymerization in step S2 specifically includes three stages. The first stage is to raise the temperature to 50 °C and maintain it for 4 h, the second stage is to raise the temperature to 80 °C and maintain it for 2 h, and the third stage is to raise the temperature to 120 °C and maintain it for 1 h. Pre-swelling at 50 °C ensures the full penetration of monomers; medium-temperature polymerization at 80 °C avoids explosive polymerization, and high-temperature crosslinking is completed at 120 °C.

[0016] According to an embodiment of the present invention, the melt-blending temperature in step S3 is 80 - 120 °C, and extrusion is carried out to form a film. Low-temperature blending protects the light conversion material.

[0017] Advantages of the present invention: (1) Through the coating layer outside the light conversion material: an inner molecular-level passivation layer (2 - 5 nm) + an outer flexible polymer layer (50 - 150 nm), the inner and outer layers cooperate to protect, and can simultaneously inhibit the migration of the light conversion material in the polymer matrix and improve the photo-thermal stability of the light conversion material in the adhesive film; (2) Light stabilizer 770 selectively modifies the surface defects of the light conversion material through hydrogen bonds / coordination bonds. At the same time, the hindered group (NH - O) of light stabilizer 770 dynamically captures free radicals and inhibits deep oxidation; (3) The outer layer of the styrene-based copolymer has no UV absorption group, and in-situ polymerization of styrene forms an amorphous and highly transparent layer, ensuring that the light transmittance of the adhesive film is ≥91%. Moreover, the outer layer of the styrene-based copolymer has a dense crosslinked network, effectively blocking the penetration of water and oxygen; (4)The elastic modulus of the styrene-based copolymer outer layer matches that of the EVA / POE film to buffer thermal stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the drawings and embodiments.

[0019] Figure 1 It is a schematic structural diagram of the high-reliability light conversion film in the first embodiment of the present invention.

[0020] Figure 2 It is a schematic structural diagram of the light conversion material composite layer in the high-reliability light conversion film of the first embodiment of the present invention.

[0021] In the figure: 1, polymer matrix; 2, light conversion material composite layer; 21, light conversion material; 22, molecular anchor layer of light stabilizer 770; 23, styrene-based copolymer outer layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will now be described in further detail with reference to 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.

[0023] First Embodiment As Figure 1 and Figure 2 shown, a high-reliability light conversion film, the film includes a polymer matrix 1 and a light conversion material composite layer 2 dispersed in the polymer matrix 1. The light conversion material composite layer 2 accounts for 0.1-5 wt% of the total mass of the film, and it includes a core layer and a coating layer. The core layer is the light conversion material 21, and the coating layer is a double-layer structure composed of a molecular anchor layer 22 of light stabilizer 770 and a styrene-based copolymer outer layer 23.

[0024] Among them, the polymer matrix 1 is at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer or polyacrylate. In this embodiment, the polymer matrix 1 uses ethylene-vinyl acetate copolymer (EVA). The light conversion material 21 is at least one of rare earth complexes, quantum dots or organic fluorescent dyes, and the particle size is 2-30 nm. In this embodiment, the quantum dots are perovskite quantum dots. The thickness of the molecular anchor layer 22 of light stabilizer 770 is 2-5 nm, and the thickness of the styrene-based copolymer outer layer 23 is 50-150 nm. In this embodiment, the styrene-based copolymer uses styrene monomer.

[0025] The specific preparation process is as follows: Step 1: Disperse CsPbBr3 quantum dots with a particle size of 10 nm (light conversion material 21) in an ethanol solution containing 1.2 wt% of Tinuvin 770, and ultrasonically treat it at 50 °C for 2 h; after centrifugal washing, the intensity of the N1s peak detected by XPS (X-ray photoelectron spectroscopy) increases by 4 times, proving that the surface has been anchored; Step 2: Mix the modified quantum dots and styrene monomer in a mass ratio of 1:2, add 0.05 wt% of ammonium persulfate, and swell at 50 °C for 4 h; inject ascorbic acid, and the molar ratio of ammonium persulfate to ascorbic acid is 1:1.2, and carry out gradient temperature polymerization, including three stages: the first stage is heated to 50 °C and maintained for 4 h, the second stage is heated to 80 °C and maintained for 2 h, and the third stage is heated to 120 °C and maintained for 1 h, and nitrogen protection is passed to obtain double-coated quantum dots. TEM (transmission electron microscope) shows a bilayer structure with no voids between layers; Step 3: Mix 100 parts of EVA particles with 0.1 - 3 parts of the light conversion material after coating treatment in a mixer, the heating temperature is 80 - 100 °C, the rotation speed is 40 - 90 rpm, 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 90 °C for 15 minutes; in the temperature range of 90 - 120 °C, extrude into a film through a screw extruder, and the thickness of the extruded film is 0.5 mm.

[0026] After laminating and crosslinking the light conversion film obtained in Example 1, test its performance data.

[0027] Example 2 The difference from Example 1 is that the light conversion material 21 uses a rare earth complex, specifically β-SiAlON:Eu²⁺ green phosphor, and the styrene-based copolymer uses a styrene-butyl acrylate copolymer.

[0028] The specific preparation process is as follows: Step 1: Immerse β-SiAlON:Eu²⁺ green phosphor with a particle size of 20 μm and a main peak wavelength of 530 nm in a tetrahydrofuran solution containing 1.0 wt% of Tinuvin 770, reflux at 60 °C for 4 h, and centrifuge and dry. XRD (X-ray diffraction) shows that the crystal plane spacing changes by 0.02 Å, proving surface modification; Step 2: Mix the modified quantum dots and styrene-butyl acrylate copolymer (the mass ratio of styrene to butyl acrylate is 9:1) in a mass ratio of 1:2, add 0.05 wt% of AIBN (azobisisobutyronitrile), and cure with ultraviolet light at a wavelength of 365 nm, 10 mW / cm², for 5 min. The light conversion material with a thickness of 80 ± 5 nm is measured by SEM (scanning electron microscope) and the surface roughness Ra < 5 nm is measured by AFM (atomic force microscope); Step 3: Mix 100 parts of EVA particles with 0.1 - 3 parts of the coated light conversion material in a mixer. The heating temperature is 90 - 110°C, the rotation speed is 50 - 100 rpm. 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 in the temperature range of 90 - 120°C through a screw extruder, and the thickness of the extruded film is 0.5 mm.

[0029] After laminating and crosslinking the light conversion film obtained in Example 2, test its performance data.

[0030] Comparative Example 1: The difference from Example 1 is that only styrene coating is carried out without the pretreatment of light stabilizer. After laminating and crosslinking the light conversion film obtained in Comparative Example 1, test its performance data.

[0031] Comparative Example 2: The difference from Example 1 is that light stabilizer 770 is directly added to the film without anchoring. After laminating and crosslinking the light conversion film obtained in Comparative Example 2, test its performance data.

[0032] Comparative Example 3: The difference from Example 1 is that the TiO2 layer is coated by the sol - gel method, and the thickness of the TiO2 layer is 50 nm, which has the property of absorbing ultraviolet light (UV). After laminating and crosslinking the light conversion film obtained in Comparative Example 3, test its performance data.

[0033] Performance Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Light transmittance loss (%) 0.2 0.5 1.8 None 2.5 PLQY (Photoluminescence Quantum Yield) 93 95 90 92 88 Crosslinking damage inhibition Complete (by elastic modulus matching) Complete (by elastic modulus matching) None Partial None Power increase of the component compared with the same formula film without light conversion agent 0.3% 0.5% 0.1% 0.3% -0.5% Power attenuation of the component after damp heat aging 0.72% 0.75% 3.85% 3.76% 3% Power attenuation after UV aging 1.2% 0.95% 5% 2% 2% Compared with Comparative Examples 1 - 3, Examples 1 - 2 have the lowest light transmittance loss (only 0.2% in Example 1, up to 2.5% in Comparative Example 3), proving that the styrene - based copolymer coating layer (without UV - absorbing groups) effectively reduces light scattering. The highest PLQY (up to 95% in Example 2), indicating that the double - layer coating structure perfectly protects the luminous efficiency of the light conversion material. The lowest damp heat aging attenuation rate (only 0.72% in Example 1, up to 3.85% in Comparative Example 1), verifying the reliability of the water and oxygen barrier layer. The best ultraviolet aging attenuation rate (only 0.95% in Example 2, 5% in Comparative Example 1), highlighting the ability of light stabilizer 770 to capture free radicals. The significant improvement in module power (0.5% increase in Example 2, a 0.5% decrease in Comparative Example 3), reflecting the high - efficiency spectral conversion ability of the light conversion material.

[0034] The "cross-linking damage inhibition" of Examples 1 and 2 was completely passed, while Comparative Examples 1 and 3 had interfacial stress cracking due to unregulated modulus. The UV aging attenuation of Comparative Example 2 (light stabilizer directly mixed into the film) was 2%, which was far worse than 1.2% of Example 1, proving the necessity of surface anchoring. The transmittance loss of Comparative Example 3 was the largest (2.5%), which contrasted the advantage of the high transparency of the styrene layer.

[0035] Therefore, the double-layer coating structure (light stabilizer molecular anchoring + polystyrene physical barrier) is the core of performance improvement, and its synergistic effect leads in transmittance, PLQY, and environmental stability. It achieves a breakthrough in "low transmittance loss" coating, which improves the stability of light conversion materials (quantum dots, rare earth phosphors, etc.) under moisture, heat, cross-linking and ultraviolet radiation. Elastic modulus matching solves the cross-linking stress problem and avoids interface failure.

[0036] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A high-reliability light conversion film, characterized in that: The film includes a polymer matrix (1) and a light conversion material composite layer (2) dispersed in the polymer matrix (1). The light conversion material composite layer (2) accounts for 0.1-5 wt% of the total mass of the film. It includes a core layer (21) and a coating layer. The core layer (21) is a light conversion material, and the coating layer is a double-layer structure composed of a light stabilizer 770 molecular anchoring layer (22) and a styrene-based copolymer outer layer (23).

2. The high-reliability light conversion adhesive film according to claim 1, wherein: The polymer matrix (1) is at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer or polyacrylate.

3. The highly reliable light conversion adhesive film according to claim 1, characterized in that: The light conversion material is at least one of rare earth complexes, quantum dots or organic fluorescent dyes, and the particle size is 2-30 nm.

4. The high-reliability light conversion adhesive film according to claim 3, characterized in that: The quantum dots are perovskite quantum dots.

5. The high-reliability light conversion adhesive film according to claim 1, characterized in that: The thickness of the light stabilizer 770 molecular anchoring layer (22) is 2-5 nm, and the thickness of the styrene-based copolymer outer layer (23) is 50-150 nm.

6. The high-reliability light conversion adhesive film according to claim 1 or 5, characterized in that: The styrene-based copolymer is styrene monomer or styrene-butyl acrylate copolymer.

7. A method for preparing a highly reliable light conversion adhesive film according to any one of claims 1 to 6, characterized in that, It includes the following steps: S1. Molecular anchoring: Dispersing the light conversion material in an ethanol solution containing light stabilizer 770, ultrasonic treating at 40-60 °C for 1-3 h, and the dosage of the light stabilizer is 0.5-3% of the mass of the light conversion material. S2. In-situ polymerization: Mixing the product in step S1 with styrene monomer, controlling the swelling degree at 30-50%, and carrying out gradient temperature rising polymerization under an inert atmosphere to form a polystyrene coating layer with a crosslinking degree of 10-20%. S3. Co-blending and film forming: Melting and co-blending the coated light conversion material with the polymer matrix, adding a peroxide initiator, a co-crosslinking agent, a tackifier and an antioxidant, and then extruding and casting into a film.

8. The preparation method of the high-reliability light conversion adhesive film according to claim 7, wherein: In step S2, the in-situ polymerization adopts a redox initiation system, including ammonium persulfate and ascorbic acid, and the molar ratio of the two is 1:1.

2.

9. The preparation method of the high-reliability light conversion adhesive film according to claim 7, characterized in that: The gradient temperature rising polymerization in step S2 specifically includes three stages. The first stage is to raise the temperature to 50 °C and keep it for 4 h. The second stage is to raise the temperature to 80 °C and keep it for 2 h. The third stage is to raise the temperature to 120 °C and keep it for 1 h.

10. The preparation method of the high-reliability light conversion adhesive film according to claim 7, wherein: In step S3, the melting and co-blending temperature is 80-120 °C, and extrusion film forming is carried out.

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