An optical enhancement coating and method of making the same

Abstract

This invention belongs to the field of coating technology, and specifically relates to an optical enhancement coating and its preparation method. The optical enhancement coating, by weight, comprises: 2-5 parts modified nanofiller, 0.3-0.8 parts tetra(substituted pyridine) tetracopper tetraiodide, 5-10 parts hydroxyl-terminated polydimethylsiloxane, 5-10 parts methacryloxypropyl-terminated polydimethylsiloxane, 0.5-1.5 parts photoinitiator, 0.005-0.01 parts curing catalyst, 0.2-0.4 parts dispersant, and 50-70 parts organic solvent. This coating has high light transmittance and, when applied to crystalline silicon solar cells, can improve short-circuit current density and power conversion efficiency, while also exhibiting good storage stability and process compatibility.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an optical enhancement coating and its preparation method. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, crystalline silicon solar cells continue to dominate the photovoltaic market due to their mature technology, controllable cost, and high energy conversion efficiency. However, during long-term use, optical losses on the cell surface, interface recombination, and aging of encapsulation materials consistently limit the improvement of module photoelectric conversion efficiency and the extension of service life.

[0003] To improve light absorption and utilization efficiency, various optical enhancement coatings are often introduced on the front or back of solar cells. These coatings typically possess anti-reflection, reflection modulation, surface passivation, and a certain degree of self-cleaning functions to reduce the reflection and scattering losses of incident light and improve interfacial carrier transport conditions. In traditional approaches, unmodified inorganic particles such as nano-titanium dioxide (TiO2), silicon dioxide (SiO2), or aluminum oxide are often used as fillers to improve the refractive index matching and light scattering performance of the coating. However, these unmodified nanoparticles have high surface energy and are prone to agglomeration in organic matrices, leading to decreased coating transparency, increased haze, and interfacial exfoliation and photocatalytic degradation under humid, hot, or ultraviolet environments, affecting long-term stability.

[0004] Therefore, existing solar cell optical enhancement coating technologies still have significant shortcomings in terms of functional integration, interface compatibility, and process adaptability. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides an optical enhancement coating and its preparation method. The coating has high light transmittance and, when applied to crystalline silicon solar cells, can improve short-circuit current density and power conversion efficiency, while also exhibiting good storage stability and process compatibility.

[0006] The technical solution of the present invention to solve the above problems is as follows: An optical enhancement coating, comprising, by weight: 2-5 parts modified nanofiller, 0.3-0.8 parts tetracopper tetraiodide (substituted pyridine) tetraiodide, 5-10 parts hydroxyl-terminated polydimethylsiloxane, 5-10 parts methacryloyloxypropyl-terminated polydimethylsiloxane, 0.5-1.5 parts photoinitiator, 0.005-0.01 parts curing catalyst, 0.2-0.4 parts dispersant, and 50-70 parts organic solvent; The modified nanofiller is a core-shell structured nanoparticle with three shells, which, from the inside out, include: core layer: nanoparticles selected from rutile titanium dioxide or monoclinic zirconium oxide; First shell layer: a chemical anchoring layer formed by the reaction of isopropyl tris(dioctylpyrophosphoryloxy)titanate with hydroxyl groups on the surface of the core layer; Second shell: A flexible grafted layer formed by the reaction of γ-methacryloyloxypropyltrimethoxysilane with the first shell; The third shell layer is a gradient copolymer formed by stepwise copolymerization of fluorinated acrylate monomers and benzyl methacrylate to create a functional layer.

[0007] Furthermore, the modified nanofiller is prepared as follows: S1. Disperse the core layer nanoparticles in anhydrous toluene and sonicate for 20-40 min to form a suspension with a mass fraction of 5-10%. Add 2-5% of the core layer mass of isopropyltris(dioctylpyrophosphoryloxy)titanate and react at 50-65℃ for 4-6 h under nitrogen protection. After the reaction is completed, centrifuge and wash the precipitate with anhydrous toluene until neutral to obtain surface-anchored modified particles. S2, the anchored modified particles obtained in step S1 are dispersed in anhydrous ethanol and ultrasonically dispersed for 15-30 min to form a suspension with a mass fraction of 3-5%. γ-methacryloyloxypropyltrimethoxysilane (KH-570) with a core layer mass of 4-8% is added. Deionized water is added dropwise to adjust the water content of the system to 1-3 wt%. The pH is adjusted to 4.0-5.0 with dilute acetic acid. The reaction is carried out at 50-65℃ for 6-10 h, and the surface-grafted modified particles are purified. S3. Disperse the grafted modified particles obtained in step S2 in anhydrous toluene and sonicate for 15-30 min to form a suspension with a mass fraction of 6-10%. Add 3-5% of the core layer mass of fluorinated acrylate monomer (hexafluorobutyl methacrylate) and 0.5-1.0% of the core layer mass of initiator. After reacting for 8-10 h, add 3-5% of the core layer mass of benzyl methacrylate and 0.5-1.0% of the core layer mass of initiator. Continue reacting for 6-10 h. After purification, the product is obtained.

[0008] Further, in step S3, the fluorinated acrylate monomer is selected from hexafluorobutyl methacrylate, trifluoroethyl methacrylate, or dodecafluoroheptyl methacrylate, and the initiator is selected from azobisisobutyronitrile or benzoyl peroxide.

[0009] Furthermore, the tetracopper tetraiodide (substituted pyridine) is selected from Cu4I4 (4-methylpyridine)4 or Cu4I4 (4-ethylpyridine)4.

[0010] Furthermore, the photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and 1-hydroxycyclohexylphenyl ketone.

[0011] Further, the photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1-2:1.

[0012] Furthermore, the curing catalyst is a mixture of tetrabutyl titanate and dibutyltin dilaurate in a mass ratio of 60-80:1.

[0013] Furthermore, the dispersant is BYK-163.

[0014] Furthermore, the mixture of the organic solvent xylene and isopropanol has a mass ratio of 4-6:1.

[0015] The preparation method of the above-mentioned optical enhancement coating adopts a low-temperature process, specifically as follows: The modified nanofiller was dispersed in an organic solvent, a dispersant was added, and the mixture was ultrasonically dispersed for 20-40 min until uniformly dispersed. Tetra-tetra-copper tetraiodide (substituted pyridine) was added, and the mixture was stirred at room temperature (20-30℃) for 30-60 min until uniformly dispersed. Hydroxyl-terminated polydimethylsiloxane and methacryloyloxypropyl-terminated polydimethylsiloxane were added, and the mixture was stirred until uniform. Then, a photoinitiator and a curing catalyst were added, and the mixture was stirred for another 20-40 min. The mixture was then vacuum degassed for 10-20 min to obtain an optical enhancement coating.

[0016] The tetracopper tetraiodide (4-methylpyridine) can be prepared by the following method: cuprous iodide and 4-methylpyridine are mixed in a molar ratio of 1:1 to 1:1.5, acetonitrile or ethanol is added as a solvent, and the mixture is reacted at 60-80℃ for 2-4 h under nitrogen protection. The mixture is then slowly cooled to room temperature, and the precipitated yellow crystals are collected. After washing with ethanol, the crystals are dried under vacuum at 50-60℃ for 12-24 h to obtain tetracopper tetraiodide (4-methylpyridine) crystals. The preparation method of tetracopper tetraiodide (4-ethylpyridine) is the same as above, except that 4-methylpyridine is replaced with 4-ethylpyridine.

[0017] The present invention has the following beneficial effects: This invention provides an optical enhancement coating that effectively improves photoelectric conversion efficiency through the synergistic optimization of light conversion, light scattering, and antireflection functions. The invention uses tetrasubstituted pyridine tetracopper tetraiodide as the light conversion material to convert ultraviolet light into visible light, reducing thermal loss. A core-shell structure is constructed using modified nanofillers to improve the dispersion and interfacial compatibility of nanoparticles in polydimethylsiloxane. A dual-curing system combining ultraviolet light curing and moisture curing is employed to complete coating curing at room temperature, avoiding the decomposition and deactivation of the thermosensitive light conversion material and effectively protecting the active ingredients.

[0018] The modified nanofiller employs a three-stage synergistic modification strategy, sequentially constructing a titanate anchoring layer, a silane grafting layer, and a gradient copolymer brush functional layer from the inside out, forming a core-shell structure with clearly defined functional zones. The first shell layer uses isopropyltris(dioctylpyrophosphate)titanate to react with the hydroxyl groups on the core surface to form a chemical anchoring layer. This layer solves the interfacial bonding problem between inorganic nanoparticles and the organic modified layer through the chelation of pyrophosphate groups with the surface of titanium dioxide or zirconium oxide, providing a reliable substrate for the subsequent attachment of the silane coupling agent. The titanate coupling agent exhibits good hydrolytic stability and can react with surface hydroxyl groups at relatively low temperatures to form stable chemical bonds. The second shell layer uses γ-methacryloyloxypropyltrimethoxysilane to react with the first shell layer to form a flexible grafting layer. This layer provides an elastic transition through a siloxane network, alleviating the modulus mismatch between the rigid inorganic core and the flexible polymer shell. This layer introduces polymerizable double bonds, providing reactive sites for the graft polymerization of fluorinated acrylates, achieving a transition from an inorganic core to an organic shell. The third shell layer is a gradient copolymer brush functional layer formed by stepwise copolymerization of fluorinated acrylate monomers and benzyl methacrylate. This layer employs a stepwise copolymerization strategy: the first step preferentially grafts fluorinated acrylate monomers to form a high-density inner brush layer; the second step grafts benzyl methacrylate to form a gradient distribution outer layer. This gradient structure produces multiple beneficial effects: fluorine migrates to the surface to form a fluorine-rich surface layer, reducing surface energy; the benzyl groups provide steric hindrance, preventing nanoparticle aggregation; the low refractive index of the inner fluorinated component matches the refractive index of the polydimethylsiloxane, reducing interfacial light scattering and reflection, and improving optical transparency. There is a progressive synergistic relationship between the three modification steps: the chemical anchoring in the first step provides a stable substrate for the second step; the active double bonds in the second step provide polymerization sites for the third step; and the functionalization in the third step endows the entire filler system with special surface properties. Modification with titanate alone can only improve dispersibility to a limited extent; modification with silane alone results in general interfacial bonding and lacks special surface functions; direct polymer coating results in weak interfacial bonding and easy desorption. The three elements work together to form a chemically bonded three-layer structure, with functions amplified layer by layer. The three-layer barrier effectively prevents water penetration and protects the inorganic core layer.

[0019] Simultaneously, this invention employs a dual-curing system composed of hydroxyl-terminated polydimethylsiloxane and methacryloxypropyl-terminated polydimethylsiloxane. The hydroxyl-terminated component, acting as a moisture-curing component, undergoes a condensation reaction with moisture in the air at room temperature to achieve crosslinking, curing without heating. The methacryloxypropyl-terminated component, acting as a photocuring component, rapidly cures through double-bond polymerization under ultraviolet light irradiation, forming a preliminary network structure. The two components work synergistically to form a dual-curing system: photocuring provides initial strength and rapid setting ability, while moisture curing provides final performance and deep crosslinking density. This system ensures room temperature operation throughout the process, effectively protecting the molecular structural integrity of tetrasubstituted pyridine tetracopper tetraiodide and avoiding loss of light conversion efficiency due to thermal decomposition.

[0020] Furthermore, this invention employs a photoinitiator system formed by combining 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 1-hydroxycyclohexylphenyl ketone (184). 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide (TPO) possesses strong penetrating power and primarily contributes to the deep curing effect. 1-Hydroxycyclohexylphenyl ketone (184) has high initiation efficiency and primarily contributes to the surface curing effect. The two work synergistically to achieve broad-spectrum coverage, with simultaneous surface and deep curing, effectively reducing defects such as surface wrinkles or uncured bottom layers, and ensuring uniform cross-linking of the coating as a whole.

[0021] This invention employs a curing catalyst system composed of tetrabutyl titanate and dibutyltin dilaurate. Tetrabutyl titanate acts as the main catalyst, promoting the condensation crosslinking reaction between the silanol groups and silanoxy groups of hydroxyl-terminated polydimethylsiloxane. Dibutyltin dilaurate acts as a synergistic catalyst; even a small amount can accelerate the moisture curing process while avoiding premature gelation of the coating. The two catalysts work synergistically to achieve a gradient curing effect. After rapid photocuring and setting, the catalyst system slowly promotes deep moisture curing, reducing the risk of coating cracking caused by internal stress.

[0022] The optical enhancement coating of this invention achieves comprehensive optimization of optical performance, interfacial compatibility, and process stability through a combination of modified nanofillers, tetraiodide tetra(substituted pyridine) tetracopper photoconversion material, and a two-component polydimethylsiloxane matrix. This coating exhibits high light transmittance and, when applied to crystalline silicon solar cells, can improve short-circuit current density and power conversion efficiency, while also possessing good storage stability and process compatibility. Attached Figure Description

[0023] Figure 1 This is a comparison chart of the conversion efficiency tests of Examples 1-3 and Comparative Examples 1-3; Figure 2 The graph shows the initial conversion efficiency test results for Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The following raw materials are all commercially available. Rutile titanium dioxide, 20nm, 99.9% purity, Qinghe County Chaotai Metal Materials Co., Ltd.; Hydroxyl-terminated polydimethylsiloxane, 99% effective ingredient content, Kandis Chemical (Hubei) Co., Ltd.; Methacryloxypropyl-terminated polydimethylsiloxane, density 0.98g / cm³. 3 Hubei Kefule Materials Technology Co., Ltd.

[0026] Example 1 An optical enhancement coating, comprising, by weight: The composition includes 3 parts modified nanofiller, 0.5 parts tetracopper tetraiodide (substituted pyridine)tetracopper, 8 parts hydroxyl-terminated polydimethylsiloxane, 8 parts methacryloyloxypropyl-terminated polydimethylsiloxane, 1 part photoinitiator, 0.3 parts dispersant, 60 parts organic solvent, and a curing catalyst, the amount of which is 0.008 parts by mass of the hydroxyl-terminated polydimethylsiloxane. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 1-hydroxycyclohexylphenyl ketone (184) in a mass ratio of 1.5:1. The curing catalyst is a mixture of tetrabutyl titanate and dibutyltin dilaurate in a mass ratio of 70:1. The dispersant is BYK-163. The tetracopper tetraiodide (substituted pyridine)tetracopper is Cu4I4(4-methylpyridine)4. The organic solvent is a mixture of xylene and isopropanol in a mass ratio of 5:1.

[0027] The modified nanofiller is a core-shell structured nanoparticle with three shells, comprising, from the inside out: a core layer: selected from rutile titanium dioxide nanoparticles; a first shell layer: a chemical anchoring layer formed by the reaction of isopropyltris(dioctylpyrophosphate)titanate with the hydroxyl groups on the surface of the core layer; a second shell layer: a flexible grafting layer formed by the reaction of γ-methacryloyloxypropyltrimethoxysilane with the first shell layer; and a third shell layer: a gradient copolymer brush functional layer formed by the stepwise copolymerization of fluorinated acrylate monomers and benzyl methacrylate.

[0028] The modified nanofiller is prepared as follows: S1, core layer nanoparticles were dispersed in anhydrous toluene and ultrasonically dispersed for 30 min to form a suspension with a mass fraction of 8%. Isopropyl tris(dioctyl pyrophosphoryloxy) titanate with a mass fraction of 3% of the core layer was added. The mixture was reacted at 60 °C for 5 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged and the precipitate was washed with anhydrous toluene until neutral to obtain surface-anchored modified particles. S2, the anchored modified particles obtained in step S1 are dispersed in anhydrous ethanol and ultrasonically dispersed for 25 min to form a suspension with a mass fraction of 4%. γ-methacryloyloxypropyltrimethoxysilane (KH-570) with a core layer mass of 6% is added. Deionized water is added dropwise to adjust the water content of the system to 3 wt%. The pH is adjusted to 4.0-5.0 with dilute acetic acid. The reaction is carried out at 60℃ for 8 h. After the reaction is completed, the precipitate is separated by centrifugation. The precipitate is washed 4 times with anhydrous ethanol (each time the amount of anhydrous ethanol used is 8 times the mass of the precipitate, and the mixture is stirred and dispersed for 13 min before centrifugation) to obtain the surface-grafted modified particles. S3, the grafted modified particles obtained in step S2 are dispersed in anhydrous toluene and ultrasonically dispersed for 20 min to form a suspension with a mass fraction of 8%. 4% (by mass) of a fluorinated acrylate monomer (hexafluorobutyl methacrylate) and 0.8% (by mass) of an initiator are added to the core layer. After reacting for 9 h, 4% (by mass) of benzyl methacrylate and 0.8% (by mass) of an initiator are added to the core layer, and the reaction continues for another 8 h. After the reaction is complete, the precipitate is centrifuged, and washed four times with anhydrous toluene (each wash using 8 times the mass of the precipitate, stirred and dispersed for 13 min before centrifugation). The precipitate is then vacuum dried at 55 °C for 14 h to obtain the final product. In step S3, the fluorinated acrylate monomer is hexafluorobutyl methacrylate, and the initiator is azobisisobutyronitrile (AIO).

[0029] The preparation method of the above-mentioned optical enhancement coating is as follows: The modified nanofiller was dispersed in an organic solvent, a dispersant was added, and the mixture was ultrasonically dispersed for 30 min until uniformly dispersed. Tetra-tetra-copper tetraiodide (substituted pyridine) was added, and the mixture was stirred at room temperature (20-30℃) for 45 min until uniformly dispersed. Hydroxyl-terminated polydimethylsiloxane and methacryloyloxypropyl-terminated polydimethylsiloxane were added, and the mixture was stirred until uniform. Then, a photoinitiator and a curing catalyst were added, and the mixture was stirred for another 30 min. The mixture was then vacuum degassed for 15 min to obtain an optical enhancement coating.

[0030] Example 2 An optical enhancement coating, comprising, by weight: The composition includes 2 parts modified nanofiller, 0.3 parts tetracopper tetraiodide (substituted pyridine)tetracopper, 10 parts hydroxyl-terminated polydimethylsiloxane, 5 parts methacryloyloxypropyl-terminated polydimethylsiloxane, 1.5 parts photoinitiator, 0.4 parts dispersant, 50 parts organic solvent, and a curing catalyst, the amount of which is 0.005 parts by mass of the hydroxyl-terminated polydimethylsiloxane. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 1-hydroxycyclohexylphenyl ketone (184) in a mass ratio of 2:1. The curing catalyst is a mixture of tetrabutyl titanate and dibutyltin dilaurate in a mass ratio of 60:1. The dispersant is BYK-163. The tetracopper tetraiodide (substituted pyridine)tetracopper is Cu4I4(4-methylpyridine)4. The organic solvent is a mixture of xylene and isopropanol in a mass ratio of 6:1.

[0031] The modified nanofiller is a core-shell structured nanoparticle with three shells, as described in Example 1. The preparation method of the modified nanofiller is the same as in Example 1.

[0032] The preparation method of the above-mentioned optical enhancement coating is the same as that in Example 1.

[0033] Example 3 An optical enhancement coating, comprising, by weight: The composition includes 5 parts modified nanofiller, 0.8 parts tetracopper tetraiodide (substituted pyridine)tetracopper, 5 parts hydroxyl-terminated polydimethylsiloxane, 10 parts methacryloyloxypropyl-terminated polydimethylsiloxane, 0.5 parts photoinitiator, 0.4 parts dispersant, 70 parts organic solvent, and a curing catalyst, the amount of which is 0.01 parts by mass of the hydroxyl-terminated polydimethylsiloxane. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 1-hydroxycyclohexylphenyl ketone (184) in a mass ratio of 1:1. The curing catalyst is a mixture of tetrabutyl titanate and dibutyltin dilaurate in a mass ratio of 80:1. The dispersant is BYK-163. The tetracopper tetraiodide (substituted pyridine)tetracopper is Cu4I4(4-methylpyridine)4. The organic solvent is a mixture of xylene and isopropanol in a mass ratio of 4:1.

[0034] The modified nanofiller is a core-shell structured nanoparticle with three shells, as described in Example 1. The preparation method of the modified nanofiller is the same as in Example 1.

[0035] The preparation method of the above-mentioned optical enhancement coating is the same as that in Example 1.

[0036] Comparative Example 1 An optical enhancement coating, wherein commercially available unmodified nano-TiO2 is used as a filler, and the rest is the same as in Example 1.

[0037] Comparative Example 2 An optical enhancement coating, wherein the modified nanofiller has a core-shell structured nanoparticle with a single-layer shell, the shell being a chemical anchoring layer formed by the reaction of isopropyl tris(dioctylpyrophosphoryloxy)titanate with hydroxyl groups on the surface of the core layer; The modified nanofiller is prepared as follows: The core layer nanoparticles were dispersed in anhydrous toluene and ultrasonically dispersed for 30 min to form a suspension with a mass fraction of 8%. Isopropyl tris(dioctyl pyrophosphoryloxy) titanate with a mass fraction of 3% of the core layer was added, and the mixture was reacted at 60 °C for 5 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged and the precipitate was washed with anhydrous toluene until neutral to obtain the final product.

[0038] The rest is the same as in Example 1.

[0039] Comparative Example 3 An optical enhancement coating, wherein the modified nanofiller is prepared by: S1, core layer nanoparticles were dispersed in anhydrous toluene and ultrasonically dispersed for 30 min to form a suspension with a mass fraction of 8%. Isopropyl tris(dioctyl pyrophosphoryloxy) titanate with a mass fraction of 3% of the core layer was added. The mixture was reacted at 60 °C for 5 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged and the precipitate was washed with anhydrous toluene until neutral to obtain surface-anchored modified particles. S2, the anchored modified particles obtained in step S1 are dispersed in anhydrous ethanol and ultrasonically dispersed for 25 min to form a suspension with a mass fraction of 4%. γ-methacryloyloxypropyltrimethoxysilane (KH-570) with a core layer mass of 6% is added. Deionized water is added dropwise to adjust the water content of the system to 3 wt%. The pH is adjusted to 4.0-5.0 with dilute acetic acid. The reaction is carried out at 60℃ for 8 h. After the reaction is completed, the precipitate is separated by centrifugation. The precipitate is washed 4 times with anhydrous ethanol (each time the amount of anhydrous ethanol used is 8 times the mass of the precipitate, and the mixture is stirred and dispersed for 13 min before centrifugation) to obtain the surface-grafted modified particles. S3. The grafted modified particles obtained in step S2 are dispersed in anhydrous toluene and ultrasonically dispersed for 20 min to form a suspension with a mass fraction of 8%. 8% methyl methacrylate (replacing fluorinated acrylate and benzyl methacrylate) and 1.6% azobisisobutyronitrile (AIBN) of the core layer are added. The mixture is reacted at 70 °C for 17 h. After the reaction is completed, the mixture is centrifuged, and the precipitate is washed four times with anhydrous toluene and vacuum dried at 55 °C for 14 h to obtain PMMA-coated nanofiller.

[0040] The rest is the same as in Example 1.

[0041] The method for preparing tetracopper tetraiodide (4-methylpyridine)tetracopper in this invention is as follows: Cuprous iodide and 4-methylpyridine are mixed at a molar ratio of 1:1.2, acetonitrile or ethanol is added as a solvent, and the mixture is reacted at 70°C for 3 hours under nitrogen protection. The mixture is then slowly cooled to room temperature, and the precipitated yellow crystals are collected. After washing with ethanol, the crystals are dried under vacuum at 55°C for 20 hours to obtain tetracopper tetraiodide (4-methylpyridine)tetracopper crystals. The method for preparing tetracopper tetraiodide (4-ethylpyridine)tetracopper is the same as above, except that 4-methylpyridine is replaced with 4-ethylpyridine.

[0042] The coatings obtained in Examples 1-3 and Comparative Examples 1-3 of the present invention were respectively coated on monocrystalline silicon solar cells, with a coating amount of 1.0–1.5 mg / cm³. 2 Curing conditions: UV curing (365nm, 100mW / cm²) 2 Nitrogen protection, 30s), moisture curing (25℃, 60%RH, 24h), to obtain the sample.

[0043] According to GB / T 14522-2008 "Artificial Climate Aging Test Method for Plastics, Coatings and Rubber Materials for Mechanical Industry Products - Fluorescent Ultraviolet Lamp" and IEC 61215 standard, the UV aging resistance and damp heat resistance were determined respectively. The short-circuit current (Isc), open-circuit voltage (Voc), and conversion efficiency (η) were tested according to GB / T 6495.1-1996 "Photovoltaic Devices - Part 1: Measurement of Photovoltaic Current-Voltage Characteristics".

[0044] Table 1. Test Results

[0045] From Table 1, Figure 1 , Figure 2 As can be seen, the optical enhancement coatings of Examples 1-3 of this invention significantly improve the photoelectric conversion performance of monocrystalline silicon solar cells. Example 1 achieved a conversion efficiency of 21.4% and a short-circuit current density (Isc) of 38.7 mA / cm². 2The open-circuit voltage (Voc) was 620 mV, representing improvements of 8.1%, 4.0%, and 1.6% compared to Comparative Example 1 (unmodified nano-TiO2), respectively. This improvement reflects the synergistic optical enhancement mechanism of the three-layer core-shell modified nanofiller and tetracopper tetraiodide (Cu4I4(4-methylpyridine)4). Example 3 performed best, achieving a conversion efficiency of 21.5%, which is related to its higher content of modified nanofiller and tetracopper tetraiodide in its formulation, indicating that increasing the functional components within a reasonable range can further enhance the light-harvesting ability. The efficiencies of Comparative Example 2 (monolayer titanate modification) and Comparative Example 3 (PMMA coating) were 20.2% and 20.5%, respectively, significantly lower than those of Example 3, demonstrating the necessity of the gradient copolymer brush functional layer design—the stepwise copolymerization of fluorinated acrylate and benzyl methacrylate not only optimizes refractive index matching but also improves compatibility with the organosilicon matrix.

[0046] Examples 1-3 all maintained an efficiency retention rate of over 95.8% after 1000 hours of QUV aging and over 94.9% after hygrothermal aging (85℃ / 85%RH, 1000 hours), significantly better than the comparative examples. Comparative Example 1 only retained 82.3% and 78.6%, indicating poor dispersion of unmodified nano-TiO2 in the organosilicon matrix, easily forming defects that accelerate degradation. Comparative Example 3, coated with PMMA, showed a decent initial efficiency (20.8%), but a hygrothermal retention rate of only 84.7%, indicating that PMMA's hygrothermal resistance is far inferior to that of fluorinated gradient copolymers. Example 2 exhibited the best weather resistance (97.0% QUV, 96.2% hygrothermal), which may be related to the higher proportion of hydroxyl-terminated polydimethylsiloxane in its formulation, forming a denser cross-linked network.

[0047] The optical enhancement coating of this invention, firstly, utilizes a three-layer core-shell structure (anchoring layer - flexible grafting layer - gradient functional layer) to achieve a gradual refractive index transition from the TiO2 core to the organosilicon matrix, minimizing interface reflection; secondly, Cu4I4 clusters convert ultraviolet light into visible light, expanding the spectral response range of the battery; and finally, a fluoropolymer brush provides a hydrophobic and oleophobic surface, blocking moisture and ultraviolet corrosion. In summary, this coating improves photoelectric conversion efficiency while ensuring long-term reliability, meeting the 25-year outdoor lifespan requirement for photovoltaic modules, and possesses promising industrialization prospects.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An optical enhancement coating, characterized in that, By weight, it includes: 2-5 parts modified nanofiller, 0.3-0.8 parts tetracopper tetraiodide (substituted pyridine) tetraiodide, 5-10 parts hydroxyl-terminated polydimethylsiloxane, 5-10 parts methacryloyloxypropyl-terminated polydimethylsiloxane, 0.5-1.5 parts photoinitiator, 0.005-0.01 parts curing catalyst, 0.2-0.4 parts dispersant, and 50-70 parts organic solvent; The modified nanofiller is a core-shell structured nanoparticle with three shells, which, from the inside out, include: core layer: nanoparticles selected from rutile titanium dioxide or monoclinic zirconium oxide; First shell layer: a chemical anchoring layer formed by the reaction of isopropyl tris(dioctylpyrophosphoryloxy)titanate with hydroxyl groups on the surface of the core layer; Second shell: A flexible grafted layer formed by the reaction of γ-methacryloyloxypropyltrimethoxysilane with the first shell; The third shell layer is a gradient copolymer formed by stepwise copolymerization of fluorinated acrylate monomers and benzyl methacrylate to create a functional layer.

2. The optical enhancement coating according to claim 1, characterized in that, The modified nanofiller is prepared as follows: S1. Disperse the core layer nanoparticles in anhydrous toluene and sonicate for 20-40 min to form a suspension with a mass fraction of 5-10%. Add 2-5% of the core layer mass of isopropyltris(dioctylpyrophosphoryloxy)titanate and react at 50-65℃ for 4-6 h under nitrogen protection. After the reaction is completed, centrifuge and wash the precipitate with anhydrous toluene until neutral to obtain surface-anchored modified particles. S2, the anchored modified particles obtained in step S1 are dispersed in anhydrous ethanol and ultrasonically dispersed for 15-30 min to form a suspension with a mass fraction of 3-5%. γ-methacryloyloxypropyltrimethoxysilane with a core layer mass of 4-8% is added, and deionized water is added dropwise to adjust the water content of the system to 1-3 wt%. The pH is adjusted to 4.0-5.0 with dilute acetic acid, and the reaction is carried out at 50-65℃ for 6-10 h. The surface-grafted modified particles are then purified. S3. Disperse the grafted modified particles obtained in step S2 in anhydrous toluene and sonicate for 15-30 min to form a suspension with a mass fraction of 6-10%. Add 3-5% of the core layer mass of fluorinated acrylate monomer and 0.5-1.0% of the core layer mass of initiator. After reacting for 8-10 h, add 3-5% of the core layer mass of benzyl methacrylate and 0.5-1.0% of the core layer mass of initiator. Continue reacting for 6-10 h. After purification, the product is obtained.

3. The optical enhancement coating according to claim 2, characterized in that, In step S3, the fluorinated acrylate monomer is selected from hexafluorobutyl methacrylate, trifluoroethyl methacrylate, or dodecafluoroheptyl methacrylate, and the initiator is selected from azobisisobutyronitrile or benzoyl peroxide.

4. The optical enhancement coating according to claim 1, characterized in that, The tetracopper tetraiodide (substituted pyridine) is selected from Cu4I4 (4-methylpyridine)4 or Cu4I4 (4-ethylpyridine)4.

5. The optical enhancement coating according to claim 1, characterized in that, The photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and 1-hydroxycyclohexylphenyl ketone.

6. The optical enhancement coating according to claim 5, characterized in that, The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1-2:

1.

7. The optical enhancement coating according to claim 1, characterized in that, The curing catalyst is a mixture of tetrabutyl titanate and dibutyltin dilaurate in a mass ratio of 60-80:

1.

8. The optical enhancement coating according to claim 1, characterized in that, The dispersant is BYK-163.

9. The optical enhancement coating according to claim 1, characterized in that, The mixture of the organic solvent xylene and isopropanol has a mass ratio of 4-6:

1.

10. A method for preparing the optical enhancement coating according to any one of claims 1-9, characterized in that, The process employs a fully cryogenic process, specifically: The modified nanofiller was dispersed in an organic solvent, a dispersant was added, and the mixture was ultrasonically dispersed for 20-40 min until uniformly dispersed. Tetra-tetra-copper tetraiodide (substituted pyridine) was added, and the mixture was stirred at room temperature for 30-60 min until uniformly dispersed. Hydroxyl-terminated polydimethylsiloxane and methacryloyloxypropyl-terminated polydimethylsiloxane were added, and the mixture was stirred until uniform. Then, a photoinitiator and a curing catalyst were added, and the mixture was stirred for another 20-40 min. The mixture was then vacuum degassed for 10-20 min to obtain an optical enhancement coating.

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