A spectrally selective superhydrophobic photovoltaic gain coating, and methods of making and using the same

Abstract

The application provides a spectrum-selective super-hydrophobic photovoltaic gain coating and a preparation method and application thereof, and belongs to the technical field of coating. The coating comprises: 45%-65% of a water-based resin matrix, wherein the water-based resin matrix is a hybrid emulsion formed by a fluorosilicon modified acrylic resin and a hydroxyl-terminated aliphatic polyurethane prepolymer; 5%-10% of infrared reflective nanomaterial; 3%-6% of hydrophobic nanoparticles; 1%-3% of a dispersing agent; 1%-3% of a silane coupling agent; 0.5%-2% of a stabilizer; 0.5%-1.5% of a rheological aid; 0.2%-0.5% of a silicone defoaming agent; and the balance is water. The application deeply integrates the spectrum-selective heat management function and the super-hydrophobic self-cleaning function in the water-based coating system at the microscale, simultaneously improves the component efficiency from two dimensions of reducing light loss and reducing heat loss, and the durability and environmental friendliness of the coating itself ensure the reliability of long-term application.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a spectrally selective superhydrophobic photovoltaic gain coating, its preparation method, and its application. Background Technology

[0002] In actual outdoor operation, the photoelectric conversion efficiency of photovoltaic modules is mainly constrained by two major physical factors: first, the loss of electrical performance due to the increase in module operating temperature (crystalline silicon cells have a negative temperature coefficient); and second, the optical loss caused by the deposition of dust and contaminants on the glass cover surface. To address these challenges, the industry has developed various functional coatings, but all of them have significant limitations and cannot meet the comprehensive requirements of high-efficiency photovoltaic modules for high light transmittance, active cooling, long-lasting self-cleaning, and long-term reliability.

[0003] Therefore, there is an urgent need in this field for a coating solution that can meet the following requirements: (1) actively reflect near-infrared light to achieve significant cooling while ensuring extremely high visible light transmittance (>91%); (2) provide durable and stable superhydrophobic self-cleaning ability; (3) adopt an environmentally friendly, low-cost process suitable for large-scale application; and (4) have excellent outdoor weather resistance, with the core functional materials effectively protected in the coating. Summary of the Invention

[0004] In view of this, the present invention provides a spectrally selective superhydrophobic photovoltaic gain coating, its preparation method and application, aiming to solve at least one technical problem in the background art.

[0005] This invention is implemented as follows:

[0006] The first aspect of this invention provides a spectrally selective superhydrophobic photovoltaic gain coating, the coating comprising the following raw materials by weight percentage:

[0007] The aqueous resin matrix comprises 45%-65%, wherein the aqueous resin matrix is ​​a hybrid emulsion formed by fluorosilicone modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer.

[0008] Infrared reflective nanomaterials: 5%-10%;

[0009] Hydrophobic nanoparticles 3%-6%;

[0010] Dispersant 1%-3%;

[0011] Silane coupling agent 1%-3%;

[0012] Stabilizer 0.5%-2%;

[0013] Rheology modifiers: 0.5%-1.5%;

[0014] Silicone defoamer 0.2%-0.5%;

[0015] The remainder is water; replenish to 100%.

[0016] Furthermore, the method for preparing the aqueous resin matrix includes the following steps:

[0017] Hydroxyethyl methacrylate, isophorone diisocyanate, and catalysts dibutyltin dilaurate and perfluorooctyl ethanol are reacted to obtain a fluorocarbon chain-terminated product; hydroxyethyl acrylate, γ-(methacryloyloxy)propyltrimethoxysilane, and polymerization inhibitor hydroquinone are added to the fluorocarbon chain-terminated product to obtain a fluorosilane functional monomer.

[0018] Using the fluorinated silane functional monomer and acrylate monomer as raw materials, copolymerization was carried out by a pre-emulsified semi-continuous seed emulsion polymerization method to obtain a fluorinated silicone modified acrylic resin emulsion.

[0019] Polycaprolactone diol, isophorone diisocyanate and dimethylolpropionic acid were reacted to obtain a prepolymer; the prepolymer was neutralized with triethylamine and then dispersed in water under high-speed shear, and ethylenediamine was added for post-chain extension. After solvent removal, a hydroxyl-terminated polyurethane prepolymer dispersion was obtained.

[0020] The hydroxyl-terminated polyurethane prepolymer dispersion and the fluorosilicone-modified acrylic resin emulsion were mixed at a solid mass ratio of (30-40):(70-60), heated, and an initiator was added to react, resulting in a hybrid emulsion formed by fluorosilicone-modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer.

[0021] Furthermore, the effective component of the infrared reflective nanomaterial is selected from one of antimony-doped tin dioxide, indium tin oxide, aluminum-doped zinc oxide, fluorine-doped tin oxide, gallium-doped zinc oxide, tungsten oxide, or doped tungsten oxide; the doped tungsten oxide is molybdenum-doped tungsten oxide, niobium-doped tungsten oxide, or titanium-doped tungsten oxide. The infrared reflective nanomaterial may also adopt a core-shell structure to further improve interface stability or impart additional functions.

[0022] Furthermore, the hydrophobic nanoparticles are nano-silica with a fluorinated silane-modified surface.

[0023] Furthermore, the raw materials of the coating also include 0.1%-2% by mass of high-hardness nano-wear-resistant particles, wherein the nano-wear-resistant particles are selected from silicon carbide, boron nitride or aluminum oxide.

[0024] Furthermore, the silane coupling agent is an epoxy silane;

[0025] The dispersant is a polymeric block copolymer dispersant; the polymeric block copolymer dispersant is an ammonium polyacrylate, an ammonium polycarboxylate, or an amphiphilic block copolymer containing anchoring groups and polyether solvation chains;

[0026] The stabilizer is a composite system of benzotriazole UV absorbers and low-alkaline hindered amine light stabilizers in a mass ratio of 1:0.8~1.2; the benzotriazole UV absorber is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol or 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole; the low-alkaline hindered amine light stabilizer is bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate or poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexadiyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]};

[0027] The rheology modifier is a nonionic polyurethane associative thickener.

[0028] A second aspect of this invention provides a method for preparing a spectrally selective superhydrophobic photovoltaic gain coating, the method comprising the following steps:

[0029] Dispersant, water, infrared reflective nanomaterials, and hydrophobic nanoparticles are mixed, and high-hardness wear-resistant nanoparticles can be selectively added. After high-shear dispersion and grinding, a uniform functional slurry is obtained.

[0030] The aqueous resin matrix and stabilizer are mixed evenly to obtain the resin mother liquor;

[0031] Under stirring conditions, the functional slurry is slowly added to the resin mother liquor. After gradient mixing, a silane coupling agent is added to carry out an interfacial coupling reaction. After the reaction is completed, water is added for preliminary dilution to adjust the viscosity of the system. Then, a rheology modifier is added, followed by water to adjust the viscosity of the system to 80 mPa·s to 120 mPa·s. After the viscosity is adjusted, an organosilicon defoamer is added and stirred evenly. After standing and aging, the mixture is filtered to obtain a spectrally selective superhydrophobic photovoltaic gain coating.

[0032] Furthermore, the high shear dispersion is performed at a speed of 5000rpm-8000rpm for 20min-30min; the grinding step is as follows: grinding with a basket mill for 1h-2h until the fineness of the functional slurry is ≤20μm.

[0033] Furthermore, the functional slurry is slowly added to the resin mother liquor, which is stirred at 200 rpm to 400 rpm, over a period of 30 min to 60 min.

[0034] The third aspect of the present invention provides the application of the above-mentioned spectrally selective superhydrophobic photovoltaic gain coating, which is coated on the light-receiving surface of photovoltaic glass to form a spectrally selective superhydrophobic photovoltaic gain coating.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This invention deeply integrates spectrally selective thermal management and superhydrophobic self-cleaning functions at the microscale into an environmentally friendly water-based coating system; it simultaneously improves component efficiency from two dimensions: reducing light loss and reducing heat loss, and the coating's own durability and environmental friendliness ensure its long-term reliability.

[0037] 2. This invention achieves active selection management of the spectrum (transmitting visible light and reflecting infrared light), and at the same time utilizes hydrophobic nanoparticles and low surface energy resin to construct superhydrophobic micro-nano structures. The two work synergistically at the microscale to produce a synergistic gain effect of 1+1>2.

[0038] 3. The average transmittance of the coating in the visible light region of the present invention (>91%) far exceeds that of the physical blend coating (~70%), and is comparable to that of the high-performance anti-reflective coating. At the same time, it has a high average reflectance in the near-infrared region (>35%) that the latter does not have.

[0039] 4. Compared with superhydrophilic photovoltaic coatings, the superhydrophobic approach of this invention is more adaptable to various climates, and its core spectrally selective heat insulation function is more direct and efficient.

[0040] 5. The coating of this invention has better durability and environmental friendliness, and the all-water system is superior to solvent-based blend coatings; the composite system of stabilizers ensures resistance to ultraviolet radiation and damp heat aging far exceeding that of similar coatings.

[0041] 6. The entire process of this invention is an aqueous system, requiring no organic solvents, making the process environmentally friendly and fully in line with the green manufacturing requirements of the photovoltaic industry.

[0042] 7. The coating of the present invention can be adapted to different application scenarios, such as strong wind and sand environment, high humidity environment, etc. Attached Figure Description

[0043] Figure 1 The image shows a comparison of the solar spectral characteristics transmission curves of the coated samples from Examples 1, 2, 4, and 5 of this invention, as well as the uncoated blank photovoltaic glass.

[0044] Figure 2 These are infrared thermal images comparing the coating samples of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 5 of this invention under simulated sunlight.

[0045] Figure 3 This is a bar chart comparing the retention rates of key performance of the coating samples of Example 1, Comparative Example 1, and Comparative Example 2 after accelerated aging in this invention.

[0046] Figure 4This is a schematic diagram comparing the SEM images of the coatings in Example 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] A spectrally selective superhydrophobic photovoltaic gain coating is disclosed, comprising: an aqueous resin matrix, infrared reflective nanomaterials, hydrophobic nanoparticles, additives, and water. In practice, the coating prepared from these raw materials is applied to a target surface and cured to obtain the spectrally selective superhydrophobic photovoltaic gain coating. The coating is configured to have an average transmittance greater than 91% in the visible light band (380nm-780nm), an average reflectance greater than 35% in the near-infrared band (780nm-2500nm), and a static contact angle with water greater than 150°.

[0049] The coating comprises the following raw materials by weight percentage: water-based resin matrix 45%-65%; infrared reflective nanomaterials 5%-10%; hydrophobic nanoparticles 3%-6%; dispersant 1%-3%; silane coupling agent 1%-3%; stabilizer 0.5%-2%; rheology modifier 0.5%-1.5%; silicone defoamer 0.2%-0.5%; the balance is water, to be made up to 100%.

[0050] The waterborne resin matrix is ​​a hybrid emulsion formed by fluorosilicone modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer, and its preparation method includes steps S1.1 to S1.4.

[0051] S1.1 Synthesis of fluorinated silane functional monomers (FA-Si);

[0052] 100 parts by weight (hereinafter referred to as parts) of hydroxyethyl methacrylate (HEMA), 45-55 parts of isophorone diisocyanate (IPDI), 0.1-0.3 parts of catalyst dibutyltin dilaurate (DBTDL), and 120-150 parts of perfluorooctyl ethanol (FOH) were reacted to obtain a fluorocarbon chain-terminated product; 50-70 parts of hydroxyethyl acrylate (HEA), 30-50 parts of γ-(methacryloyloxy)propyltrimethoxysilane (KH-570), and 0.05-0.1 parts of polymerization inhibitor (hydroquinone) were added to the fluorocarbon chain-terminated product to obtain a fluorosilane functional monomer;

[0053] In the following embodiments, the specific steps are as follows: First, under nitrogen protection, 100 parts of HEMA, 50 parts of IPDI, and 0.1 parts of the catalyst DBTDL are added to a reactor and reacted at 60℃-65℃ until the -NCO content reaches half of the theoretical value; FOH and the remaining catalyst DBTDL (0.2 parts) are added, and the temperature is raised to 75℃-80℃ until the -NCO characteristic peak completely disappears (infrared monitoring), obtaining a fluorocarbon chain-terminated intermediate; the temperature is lowered to 60℃, HEA, KH-570, and a polymerization inhibitor are added, and the reaction is continued at 60℃-65℃ for 4h-6h to obtain the final multifunctional monomer (fluorosilane functional monomer FA-Si) containing fluorine, silaneoxy, and acrylate double bonds. The synthesis steps of FA-Si are not limited to the conditions listed, and other unlisted conditions within the scope are also applicable.

[0054] S1.2, Synthetic fluorosilicone modified acrylic resin (FSAR) emulsion;

[0055] Using 10-25 parts of the fluorinated silane functional monomer and 75-90 parts of conventional acrylate monomers (such as methyl methacrylate MMA, butyl acrylate BA, and isooctyl acrylate 2-EHA) as raw materials, copolymerization is carried out by a pre-emulsified semi-continuous seed emulsion polymerization method to obtain the fluorosilicone modified acrylic resin emulsion.

[0056] In the following embodiments, the specific steps are as follows: 15 parts of the fluorosilane functional monomer FA-Si, 2 parts of the emulsifier sodium allyl hydroxypropyl sulfonate, and 60 parts of water are pre-emulsified to form a pre-emulsion; 60 parts of water and 85 parts of methyl methacrylate (MMA) are added to a reactor, the temperature is raised to 80°C, and 0.3 parts of ammonium persulfate initiator are added to initiate seed polymerization; at 80°C-83°C, the pre-emulsion and 0.2 parts of ammonium persulfate initiator are added dropwise simultaneously over 4 hours; the mixture is kept at this temperature for 1 hour to mature, cooled, and the pH is adjusted to 7.5 with ammonia water to obtain a stable FSAR emulsion. The synthesis steps of the FSAR emulsion are not limited to the conditions listed, and other unlisted conditions within the scope are also applicable.

[0057] S1.3, Synthesize hydroxyl-terminated polyurethane prepolymer (HTPU) dispersion;

[0058] 60-120 parts of polycaprolactone diol (PCL, Mn=1000), 15-25 parts of isophorone diisocyanate (IPDI), and 4-8 parts of dimethylolpropionic acid (DMPA) were reacted to obtain a prepolymer. The prepolymer was then extended by adding chain extender 1,4-butanediol (BDO), neutralized with triethylamine (TEA), dispersed in water under high-speed shear, and further extended by adding post-chain extender ethylenediamine (EDA). After removing the solvents acetone and water, a hydroxyl-terminated polyurethane prepolymer dispersion was obtained.

[0059] In the following embodiments, the specific steps are as follows: 100 parts of dehydrated polycaprolactone diol (PCL), 20 parts of isophorone diisocyanate (IPDI), 6 parts of dimethylolpropionic acid (DMPA), and 0.12 parts of catalyst dibutyltin dilaurate (DBTDL) are added to a reactor and reacted at 80°C-85°C until the -NCO content reaches the designed value (0.02 mol); the temperature is lowered to 60°C, and 3.5 parts of BDO are added for chain extension; the temperature is lowered to below 40°C, and 4.55 parts of TEA are added to neutralize and form a salt; the prepolymer is dispersed in 241.7 parts of deionized water under high-speed shear (>2000 rpm); 0.60 parts of EDA are added for chain extension in water; finally, acetone and water are removed by vacuum distillation to obtain an HTPU dispersion with a solid content of approximately 35%. The synthesis steps of the HTPU dispersion are not limited to the conditions listed, and other unlisted conditions within the scope are also applicable.

[0060] S1.4, Synthetic waterborne fluorosilicone / polyurethane hybrid emulsion;

[0061] The hydroxyl-terminated polyurethane prepolymer dispersion and the fluorosilicone-modified acrylic resin emulsion are mixed at a solid mass ratio of (30-40):(70-60). At this ratio, FSAR provides a rigid and low surface energy framework, while HTPU provides flexibility and strong adhesion. The mixture is heated and an initiator is added to carry out the reaction, resulting in a hybrid emulsion formed by fluorosilicone-modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer (hereinafter referred to as waterborne fluorosilicone / polyurethane hybrid emulsion).

[0062] In the following embodiments, the specific steps are as follows: Under slow stirring (200 rpm-400 rpm), the HTPU dispersion (60 parts) prepared in step 1.3 is slowly added to the FSAR emulsion (50 parts) prepared in step 1.2. After the addition is complete, the mixed emulsion is heated to 60℃-65℃, and a small amount of azo initiator V-50 (0.2 wt% of the mixed emulsion) is added. The reaction is maintained at this temperature for 1.5 hours. This process promotes the condensation reaction between unreacted KH-570 silaneoxy groups in the FSAR emulsion and some amino or hydroxyl groups on the HTPU chain, and the formation of graft copolymerization at the FSAR-HTPU interface, forming an interpenetrating network (IPN) or semi-interpenetrating network (Semi-IPN) structure, achieving strong interfacial bonding. After the reaction is complete, the mixture is cooled and filtered to obtain an aqueous fluorosilicone / polyurethane hybrid emulsion. The synthesis steps are not limited to the conditions listed; other unlisted conditions within the scope are also applicable.

[0063] This invention uses a hybrid emulsion formed by fluorosilicone modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer as the waterborne resin matrix of the coating. This emulsion combines the weather resistance of acrylic resin, the low surface energy of fluorosilicone materials, and the excellent toughness and high adhesion to substrates such as glass and metal of polyurethane.

[0064] The effective components of the infrared reflective nanomaterials are selected from one of the following: antimony-doped tin dioxide, indium tin oxide, aluminum-doped zinc oxide, fluorine-doped tin oxide, gallium-doped zinc oxide, tungsten oxide, or tungsten oxide.

[0065] The unique properties of WO3 stem from its temperature-induced phase transition characteristics. At room temperature, WO3 is a semiconductor phase with a certain infrared reflectivity (~32%). When the ambient or module operating temperature rises above 70°C, it undergoes a phase transition to a metallic state, resulting in a sharp increase in the concentration of free electrons and a significant improvement in the average reflectivity in the near-infrared region to ~45%. This enables adaptive intelligent thermal management, where higher temperatures lead to stronger thermal insulation, making it particularly suitable for photovoltaic power plants in high-temperature regions. Tungsten oxide can be doped with elements such as molybdenum (Mo) and niobium (Nb) to adjust its phase transition temperature to a more suitable range for photovoltaic module operation (e.g., 65°C-80°C), or with elements such as titanium (Ti) and silicon (Si) to improve its phase transition cycle stability. The examples below illustrate antimony-doped tin dioxide (ATO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), and tungsten oxide (WO3), but are not limited to the listed infrared reflective nanomaterials; other unlisted infrared reflective nanomaterials within this scope are also applicable.

[0066] In practical implementation, infrared reflective nanomaterials can be directly made from the above-mentioned materials, or they can be made from core-shell structure materials with the above-mentioned effective components as the core, in order to further improve interface stability or give additional functions.

[0067] The hydrophobic nanoparticles are made of nano-silica modified with fluorine-containing silane, which are used to construct the micro-nano rough structure of the coating surface.

[0068] In practice, fluorinated silane-modified nano-silica can be commercially available or prepared in-house. In the following examples, the specific steps for preparing fluorinated silane-modified nano-silica are as follows: 100g of hydrophilic fumed silica nano-particles (10nm-20nm particle size) are dispersed in 800mL of anhydrous ethanol to form a uniform dispersion. Then, approximately 20g of perfluorooctyltriethoxysilane is added, and the mixture is refluxed at 60℃-80℃ for 5 hours. After the reaction is complete, the mixture is centrifuged, washed with ethanol, and vacuum dried to obtain hydrophobic nano-SiO2 powder with low surface energy fluorocarbon chains grafted onto its surface, i.e., fluorinated silane-modified nano-silica. This powder has a static contact angle with water greater than 145°, which is crucial for constructing the superhydrophobic micro / nano rough structure of the coating. The synthesis steps for hydrophobic nanoparticles are not limited to the conditions listed; other unlisted conditions are also applicable.

[0069] The dispersant is a polymeric block copolymer dispersant, preferably ammonium polyacrylate, ammonium polycarboxylate, or an amphiphilic block copolymer containing anchoring groups (such as amino and carboxyl groups) and polyether solvation chains.

[0070] This type of dispersant ensures the long-term uniform dispersion of infrared reflective nanomaterials and hydrophobic nanoparticles in aqueous systems through a combination of electrostatic repulsion and steric hindrance, preventing agglomeration and maintaining the high transmittance and functional uniformity of the coating. Its molecular structure includes anchoring groups (such as carboxyl and amino groups) that can form strong adsorption on the nanoparticle surface and solvation segments (such as polyethers) that are compatible with water. This amphiphilic structure forms a steric hindrance layer around the nanoparticles, effectively overcoming agglomeration caused by van der Waals forces. This is key to maintaining the long-term stability of the nanoslurry (no hard sedimentation for >6 months) and the high transmittance of the coating.

[0071] The preferred silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-aminopropyltriethoxysilane (KH-550), or a mixture thereof, to enhance the interfacial bonding between the inorganic nanofiller and the organic resin matrix.

[0072] Stabilizers include ultraviolet absorbers (UVA) and hindered amine light stabilizers (HALS).

[0073] Photovoltaic coatings are exposed to extremely high intensity sunlight in the ultraviolet (290nm-400nm) band for extended periods. While UVA alone may degrade over time, HALS (Hydrogen Alternating Current) cannot effectively shield against initial UV attack. This invention employs a UVA:HALS ratio of 1:0.8-1.2 by mass, creating a multi-layered defense system against UV aging of the coating. UVA (e.g., Tinuvin 328) first absorbs and converts UV energy, while HALS (e.g., Tinuvin 123 or Chimassorb 2020) efficiently quenches free radicals generated at the resin and interface. The synergistic effect of both extends the coating's UV aging resistance to over 25 years, while maintaining high retention rates of transmittance, hydrophobicity, and infrared reflection.

[0074] The preferred ultraviolet absorber is a benzotriazole compound, such as 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol (Tinuvin 328) and 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole; its function is to efficiently absorb ultraviolet light in the 290nm-400nm range, convert it into harmless heat energy, and protect the resin and core-shell particles from direct impact by ultraviolet photons;

[0075] Hindered amine light stabilizers are preferably low-alkalinity, high-molecular-weight HALS, such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 123) and poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexadiyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]} (Chimassorb 2020). Their function is to capture free radicals generated during the aging process of the coating and interrupt the photo-oxidative degradation chain reaction.

[0076] The rheology modifier is a nonionic polyurethane associative thickener (HEUR). This type of rheology modifier forms a spatial network structure through reversible hydrogen bonding, providing excellent leveling properties, anti-splatter properties, and storage stability. It also exhibits significant high shear thinning characteristics, facilitating various application processes such as spraying and roller coating, while ensuring a smooth and flat film surface without affecting optical properties.

[0077] In practice, the raw materials of the coating also include 0.1%-2% by mass of high-hardness nano-wear-resistant particles, which are selected from silicon carbide, boron nitride or aluminum oxide.

[0078] Through the synergistic formulation of the above components, especially specific types of additives, the coating is configured to have an average transmittance greater than 91% in the visible light band (380nm-780nm), an average reflectance greater than 35% in the near-infrared band (780nm-2500nm), a static contact angle with water greater than 150°, and a water roll-off angle less than 10°. Photovoltaic glass coated with this coating, under standard simulated sunlight irradiation, exhibits a backsheet steady-state temperature that is more than 5°C lower than that of uncoated glass, resulting in a maximum output power increase of over 4.9% for the photovoltaic module.

[0079] A method for preparing a spectrally selective superhydrophobic photovoltaic gain coating includes the following steps:

[0080] S1. Dispersant, water, infrared reflective nanomaterials, and hydrophobic nanoparticles are mixed and then dispersed and ground under high shear to obtain a uniform component A-functional slurry.

[0081] The high-shear dispersion is carried out at a speed of 5000rpm-8000rpm for 20min-30min; the slurry is then ground in a basket mill for 1h-2h until the fineness of the functional slurry is ≤20μm.

[0082] In practice, nano-abrasion-resistant particles can be added in this step as part of the functional slurry.

[0083] This step aims to pre-disperse a high content of infrared-reflective nanomaterials into a highly stable slurry in an aqueous medium, avoiding agglomeration caused by the direct addition of dry powder during final mixing.

[0084] S2. Mix the aqueous resin matrix and stabilizer evenly to obtain component B - resin mother liquor;

[0085] Specifically, in a low-speed stirring vessel, add the formulated amount of aqueous resin matrix (preferably with a solid content of about 45%). While stirring slowly at 300-500 rpm, sequentially add the formulated amount of ultraviolet absorber (such as benzotriazole) and hindered amine light stabilizer (HALS). Continue stirring for 30-45 minutes to ensure all additives are fully dissolved or uniformly dispersed in the resin emulsion, forming a uniform and stable component B resin mother liquor.

[0086] In practice, other functional additives that need to be premixed (such as adhesion promoters) may be added to this step. The functional additives used are permitted in this field and are not specifically limited here.

[0087] S3, gradient mixing, interfacial coupling, viscosity adjustment and system maturation;

[0088] This step aims to achieve uniform dispersion and stable bonding of functional nanoparticles such as infrared reflective nanomaterials and hydrophobic nanoparticles in an aqueous resin matrix through precisely controlled hybrid dynamics, and to construct a final coating system with excellent application rheology and stability.

[0089] Specifically, it includes the following sub-steps:

[0090] S3.1 Gradient Mixing:

[0091] Under low-speed stirring conditions, component A (functional slurry) is slowly and uniformly pumped into component B (resin mother liquor) which is being stirred at 200 rpm to 400 rpm within a time window of 30 to 60 minutes using a peristaltic pump or a controlled dripping device.

[0092] S3.2 Interface Coupling:

[0093] After component A is added, continue stirring the system at 200-400 rpm; slowly add the prescribed amount of silane coupling agent (such as γ-(2,3-epoxypropoxy)propyltrimethoxysilane). After adding the agent, maintain the stirring speed within the same range and continue stirring for 20 to 30 minutes.

[0094] S3.3, Viscosity Adjustment:

[0095] Preliminary dilution: After the interfacial coupling reaction is completed, add about 50%-70% of the amount of deionized water to initially reduce the viscosity of the system from the high viscosity state after mixing, which facilitates the uniform dispersion of subsequent additives.

[0096] Rheology modifier: Add the full amount of rheology modifier (such as nonionic polyurethane associative thickener) to the formulation.

[0097] Final viscosity setting: The viscosity of the system is finely adjusted using the remaining deionized water until the viscosity of the coating reaches the target range of 80 mPa·s to 120 mPa·s, as measured by a rotational viscometer at 25°C.

[0098] Defoaming treatment: After viscosity adjustment, add the formulated amount of silicone defoamer. Keep stirring (200rpm-400rpm) for 10 to 15 minutes to ensure the silicone defoamer is evenly dispersed throughout the coating system, eliminating bubbles introduced in the previous process and inhibiting the generation of new bubbles in subsequent processes.

[0099] S3.4, Maturation:

[0100] After all materials have been added and viscosity adjusted, adjust the stirring speed of the coating system to 300 rpm to 500 rpm and continue stirring for 1 to 2 hours. This continuous stirring helps to further homogenize the components and complete some of the later reactions. Subsequently, stop stirring, seal the container, and place it at room temperature (25℃±5℃) for at least 24 hours to mature.

[0101] S3.5, Filtration:

[0102] After curing, the coating is filtered using a 200-300 mesh filter or filter bag to remove any trace amounts of large particles or abrasive media fragments, thus obtaining a uniform and stable spectrally selective superhydrophobic photovoltaic gain coating.

[0103] The coating prepared according to this invention is applied to the light-receiving surface of photovoltaic glass to form a dry film of 1.5μm-5.0μm. After curing at room temperature or low temperature, a spectrally selective superhydrophobic photovoltaic gain coating is formed. The specific steps are as follows: The coating is applied to the thoroughly cleaned and dried photovoltaic glass surface using methods such as ultrasonic spraying, slot coating, or precision roller coating. By controlling the wet film thickness, the final dry film thickness is precisely controlled within the preferred range of 1.5μm-5.0μm, preferably 2.0μm-4.0μm, and further preferably 2.5μm-3.5μm. This thickness range represents the optimal balance between high light transmittance, sufficient functional particle loading, and film mechanical strength. After coating, the coating can quickly surface dry at room temperature, with a touch-drying time of approximately 15-30 minutes. Complete curing can be achieved in two ways: firstly, curing at room temperature (25℃) for 5-7 days to allow the silane network to fully cross-link; secondly, heat treatment in an oven at 50℃-70℃ for 1-2 hours to accelerate the curing process.

[0104] The microscopic mechanism of the coating of this invention is as follows: the infrared-reflective nanomaterials reflect the incident near-infrared light of the sun back, while allowing visible light to pass through. The micro-nano rough surface constructed by the hydrophobic nanoparticles and the low surface energy resin exhibits a superhydrophobic lotus leaf effect, making it easy for water droplets to roll off and carry away dust.

[0105] The technical effects and mechanisms of action of this invention are as follows:

[0106] (1) Spectral selectivity and thermal insulation mechanism: The selected infrared reflective nanomaterials (ATO, ITO, AZO, WO3, etc.) are wide-bandgap n-type semiconductors with a high concentration of free carriers. When sunlight is incident, the near-infrared light with photon energy lower than the bandgap cannot excite valence electrons, but can interact with free carriers, inducing plasma oscillation and free carrier absorption, thus reflecting most of this energy back instead of absorbing it and converting it into heat. By controlling the process, the infrared reflective nanomaterials are uniformly and densely arranged in the coating to form an effective reflective layer in the 780nm-2500nm wavelength band.

[0107] (2) Superhydrophobic self-cleaning mechanism: The superhydrophobicity of the coating surface is determined by the low surface energy chemical composition and the micro-nano rough structure. During the film formation process, some of the fluorinated silane-modified nano-SiO2 migrates to the surface, and together with the fluorinated silicon segments of the resin itself, reduces the surface energy to an extremely low level (<20mN / m). At the same time, these nanoparticles form a multi-level rough structure on the surface at the scale of hundreds of nanometers to micrometers. When water droplets come into contact with it, air is trapped in the rough grooves, forming a composite contact (Cassie-Baxter model). The actual solid-liquid contact area is greatly reduced, thus exhibiting a high water contact angle (>150°) and a low water roll-off angle (<10°), making it easy for dust particles to be carried away by the rolling water droplets.

[0108] (3) Long-term durability:

[0109] Light stabilization mechanism: The combination of UVA and HALS constitutes a dual prevention-repair mechanism. UVA preferentially absorbs ultraviolet radiation and converts it into harmless heat energy; HALS efficiently captures and neutralizes alkyl radicals (R·) and peroxy radicals (ROO·) generated by the coating under trace amounts of ultraviolet radiation, interrupting the photo-oxidation chain reaction.

[0110] Mechanical and chemical stabilization mechanisms: Silane coupling agents (such as KH-550, KH-560) form a -Si-O-Si covalent cross-linked network at the nanoparticle-resin interface and between resin molecular chains, significantly improving the coating's cohesive strength, adhesion, and hydrolysis resistance. The chemical inertness of the fluorosilicone components in the waterborne resin matrix also enhances the coating's resistance to chemical corrosion such as acid rain and salt spray.

[0111] (4) Synergistic Gain Mechanism: The two core functions of this coating constitute a positive gain cycle. The superhydrophobic self-cleaning function maintains high light transmittance over a long period of time, ensuring maximum photon intake of the module. The infrared reflection function actively reduces the operating temperature of the module, reducing efficiency loss caused by temperature rise (the temperature coefficient of crystalline silicon cells is approximately -0.3% / ℃ to -0.4% / ℃), and slows down the aging rate of the encapsulation material. The two complement each other, jointly ensuring that the photovoltaic module maintains high energy output throughout its entire life cycle, and its comprehensive power improvement effect is far superior to coatings with only a single function.

[0112] (5) Intelligent Adaptive Thermal Insulation Mechanism: When infrared reflective nanomaterials such as tungsten oxide (WO3) and its doped materials are used, the coating possesses temperature sensing and response capabilities. Its crystal structure undergoes a reversible change with temperature, causing the material's electrical properties to transform from semiconductor to metal-like. In the metal-like state, the concentration of free electrons in the material is significantly increased, and the plasma reflection effect on near-infrared light is significantly enhanced. This characteristic enables the coating to automatically provide stronger thermal insulation power during the high-temperature period when the component needs cooling the most, realizing intelligent and optimized thermal energy management.

[0113] Example 1

[0114] I. The raw material formulation of the spectrally selective superhydrophobic photovoltaic gain coating used in this implementation is as follows:

[0115] Waterborne resin matrix (waterborne fluorosilicone / polyurethane hybrid emulsion, solid content 45%): 58.0%;

[0116] Antimony-doped tin dioxide (ATO) nanomaterials (D50=80nm): 8.0%;

[0117] Hydrophobic nanoparticles (perfluorooctyltriethoxysilane modified nano-SiO2, particle size 15±3nm): 4.5%;

[0118] Dispersant (ammonium polyacrylate): 1.5%;

[0119] Aminosilane coupling agent (KH-550): 2.0%;

[0120] Ultraviolet absorber (2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol): 0.8%;

[0121] Hindered amine light stabilizer (bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Tinuvin 123): 0.7%;

[0122] Rheology modifier (nonionic polyurethane associative thickener): 1.0%;

[0123] Organosilicon defoamer: 0.3%;

[0124] Deionized water: Replenish to 100.0%.

[0125] II. A method for preparing a spectrally selective superhydrophobic photovoltaic gain coating, comprising the following steps:

[0126] S1. Weigh all the raw materials in the above proportions. First, add 60% of the formula amount of deionized water and all of the dispersant to a mixing container. Under medium-speed stirring at 500 rpm, slowly add antimony-doped tin dioxide (ATO) nanomaterials. After the addition is complete, transfer the mixture to a high-shear emulsifier and disperse it continuously at 7000 rpm for 25 minutes to initially break up the particle aggregates. Then, immediately add the hydrophobic nanoparticles and transfer the mixture to a basket mill. Use zirconia beads as the grinding medium to grind and disperse until the slurry fineness is ≤20μm and the particle size distribution is uniform, obtaining component A-functional slurry with stable solid content and good suspension properties for later use.

[0127] S2. In a low-speed stirring container, add the formulated amount of aqueous resin matrix. While stirring slowly at 400 rpm, add the formulated amounts of UV absorber and hindered amine light stabilizer sequentially. Continue stirring for 40 minutes to ensure that all stabilizers are fully dissolved or uniformly dispersed in the resin emulsion, forming a uniform and stable component B resin mother liquor.

[0128] S3. Under stirring at 300 rpm, slowly add component A to component B, which is being stirred at 300 rpm, over 45 minutes. Continue stirring while adding KH-550, and continue stirring for another 25 minutes to complete the interfacial coupling reaction. Add approximately 60% of the remaining amount of deionized water and rheology modifier from the formula. Use the remaining deionized water to finely adjust the viscosity of the system until the viscosity of the coating reaches (95±5) mPa·s at 25℃, as measured by a rotational viscometer. Then add the formula amount of silicone defoamer, and stir at 300 rpm for 15 minutes. Increase the speed to 500 rpm and continue stirring for 1.5 hours. After that, stop stirring, seal the container, and place it at room temperature (25℃±5℃) for 24 hours to mature. Then filter it using a 200-mesh filter to obtain the spectrally selective superhydrophobic photovoltaic gain coating.

[0129] III. Preparation of a spectrally selective superhydrophobic photovoltaic gain coating: The specific steps are as follows: First, clean and dry the surface of the photovoltaic glass; then, apply the above coating to the light-receiving surface of the photovoltaic glass by ultrasonic spraying, and control the wet film thickness to make the final dry film thickness = (3.0±0.5) μm; then, quickly surface dry at room temperature, with a touch drying time of about 20 min; finally, cure in an oven at 65℃ for 2 h to obtain a spectrally selective superhydrophobic photovoltaic gain coating, the properties of which are shown in Table 1 below.

[0130] Example 2

[0131] The difference between this embodiment and Embodiment 1 is that the antimony-doped tin dioxide (ATO) nanomaterial in the raw materials of the coating is replaced with indium tin oxide (ITO) nanomaterial (D50=85nm), while the other conditions and steps are the same as in Embodiment 1.

[0132] Example 3

[0133] The difference between this embodiment and Embodiment 1 is that the antimony-doped tin dioxide (ATO) nanomaterials in the raw materials of the coating are replaced with aluminum-doped zinc oxide (AZO) nanomaterials (D50=75nm), while the other conditions and steps are the same as in Embodiment 1.

[0134] Example 4

[0135] The difference between this embodiment and Embodiment 1 is that the antimony-doped tin dioxide (ATO) nanomaterial in the raw materials of the coating is replaced with tungsten oxide (WO3) nanomaterial (D50=90nm), while the other conditions and steps are the same as in Embodiment 1.

[0136] Example 5

[0137] The difference between this embodiment and embodiment 1 is that 1.2% of nano-silicon carbide (β-SiC, particle size D50=50nm) is added to the raw materials of the coating as high-hardness nano-wear-resistant particles, and added to component A - functional slurry. In order to maintain the total proportion, the amount of deionized water is reduced by an equal amount.

[0138] Specifically, S1, weigh all the raw materials in the above proportions, and first add 60% of the formula amount of deionized water and all of the polymer block copolymer dispersant to a mixing container; under medium-speed stirring at 500 rpm, slowly add antimony-doped tin dioxide (ATO) nanomaterials and nano-silicon carbide; after the addition is complete, transfer the mixture to a high-shear emulsifier and disperse it continuously at 7000 rpm for 25 minutes to initially break up the particle aggregates. Then, immediately add hydrophobic nanoparticles and transfer the mixture to a basket mill, using zirconia beads as the grinding medium, and grind and disperse until the slurry fineness is ≤20 μm and the particle size distribution is uniform, to obtain component A-functional slurry with stable solid content and good suspension, for later use. Other conditions and steps are the same as in Example 1.

[0139] Example 6

[0140] The difference between this embodiment and Example 1 is that the silane coupling agent is replaced by aminosilane coupling agent (KH-550) with γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and its dosage is increased to 3.0%. In order to maintain the total proportion, the amount of deionized water is reduced by the same amount. Other conditions and steps are the same as in Example 1.

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 1 is that the infrared reflective nanomaterial - antimony-doped tin dioxide (ATO) nanomaterial - was removed from the raw materials of the coating, while other conditions were the same as in Example 1.

[0143] Comparative Example 2

[0144] The difference between this comparative example and Example 1 is that the coating is prepared using a simple physical blending method. The steps of this preparation method are as follows: all raw materials for the coating are added to a stirred tank at once, subjected to high-speed shear dispersion for 2 hours, then cured for 24 hours and filtered to obtain the coating. The coating preparation steps are the same as in Example 1.

[0145] Comparative Example 3

[0146] The difference between this comparative example and Example 1 is that the waterborne resin matrix is ​​replaced by a waterborne fluorosilicone / polyurethane hybrid emulsion with a regular acrylic emulsion, while the other conditions are the same as in Example 1.

[0147] Comparative Example 4

[0148] The difference between this comparative example and Example 1 is that hydrophobic nanoparticles were removed from the raw materials of the coating, while other conditions were the same as in Example 1.

[0149] Comparative Example 5

[0150] The coating was prepared according to the preparation method of Example 1 in the invention patent application with publication number CN117701114A entitled "Preparation Method of Transparent Superhydrophobic Thermal Insulation Coating". The process is as follows: modified nano-SiO2, modified ATO powder and epoxy resin E51 curing agent system are simply mixed in a solvent and then sprayed.

[0151] The coating properties obtained in Examples 1 to 6 are summarized in Table 1 below. The coating properties obtained in Comparative Examples 1 to 5 are summarized in Table 2 below.

[0152] (1) Test method for average transmittance in the visible light region: The test was conducted using a spectrophotometer equipped with an integrating sphere (such as a PerkinElmer Lambda 1050+). A coated photovoltaic glass sample (at least 50 mm × 50 mm in size) was placed in the sample's optical path, with an uncoated photovoltaic glass of the same specifications used as a reference baseline. The transmission spectrum of the sample was measured at 5 nm intervals within the visible light wavelength range of 380 nm to 780 nm. The average transmittance was obtained by calculating the arithmetic mean of all data points within this wavelength range. The test light source was a standard D65 light source or a simulated AM 1.5G solar spectrum.

[0153] (2) Test method for average reflectance in the near-infrared region: Measurement was performed using a reflectance accessory (e.g., a 150mm integrating sphere) of the same spectrophotometer. The total reflectance spectrum (including specular and diffuse reflection) of the coated sample surface was measured at 10nm intervals within the near-infrared wavelength range of 780nm to 2500nm. Calibration was performed using the reflectance of a standard white plate (e.g., BaSO4 or Spectralon) as a 100% reference. The average reflectance was obtained by calculating the arithmetic mean of all data points within this wavelength range.

[0154] (3) Test method for water contact angle: The test was conducted according to ASTM D7334-08(2013) standard, "Standard Practice Guide for Measuring the Wettability of Coated Surfaces by Advance Contact Angle". A contact angle measuring instrument (such as the Dataphysics OCA series) was used, and the test was conducted in a constant temperature and humidity environment of 25℃±1℃ and relative humidity of 50%±5%. 4 μL of deionized water was vertically dropped onto at least 5 different locations on the coating surface using a microsyringe. Within 10 seconds of the water droplet deposition, the contact angle was calculated using the instrument software with the tangent method or the Young-Laplace fitting method. The arithmetic mean of all measurements was taken as the static water contact angle of the sample.

[0155] (4) Test method for water roll-off angle: The test is conducted using the tilt stage attachment of the same contact angle measuring instrument. Place a 10 μL droplet of deionized water on a horizontal coating surface. Then, slowly tilt the sample stage at a rate of 1° / s until the droplet begins to roll. Record the tilt angle of the sample stage at the instant the droplet begins to roll; this is the water roll-off angle of the droplet. Repeat the test at at least three different locations on the sample surface and take the maximum value as the reported water roll-off angle value for that sample. Generally, a water roll-off angle of less than 10° is considered to indicate excellent self-cleaning ability.

[0156] (5) Test method for thermal insulation temperature difference: A simulated test platform was constructed: A coated glass sample (100mm × 100mm) was placed on top of a sealed cavity (80mm × 80mm × 30mm) made of thermal insulation foam (thickness ≥ 30mm). Aluminum foil was attached to the inner surface of the cavity to form a blackbody cavity. A high-precision thermocouple (±0.1℃) was placed at the center of the cavity. The entire device was placed in a standard solar simulator (spectral matching AM 1.5G, irradiance 1000W / m²). 2 Directly below. Simultaneously, using an identical setup but with uncoated blank glass as a control. The simulator was turned on for irradiation. Once the center temperatures of the backplates of both cavities reached a steady state (temperature change rate < 0.1℃ / min), their respective temperatures were recorded. The thermal insulation temperature difference (ΔT) was calculated as the difference between the steady-state temperature of the blank glass cavity and the steady-state temperature of the coated glass cavity.

[0157] (6) Test method for overall power improvement rate: A standard commercial small photovoltaic module (such as 36 monocrystalline silicon cells in series, with a nominal power of about 50W) was selected as the test carrier. An IV curve tester was used under standard test conditions (STC: irradiance 1000W / m²). 2 Under AM 1.5G spectrum and battery temperature of 25°C, the maximum output power (P1) of the uncoated module was accurately measured and recorded. Subsequently, a coating was applied to the light-receiving surface of the module's glass cover according to the method of this invention. After the coating had fully cured, the maximum output power (P2) of the coated module was measured again under the same STC conditions. The overall power improvement rate (η) was calculated using the following formula: η(%)=[(P2-P1) / P1]×100%.

[0158] (7) Pencil Hardness Test Method: The test was conducted according to ASTM D3363-05(2011) standard, "Standard Test Method for Hardness of Films by Pencil Test." A set of standard drawing pencils ranging from 9B (softest) to 9H (hardest) was used. The pencil lead was smoothed on sandpaper and fixed in the pencil hardness tester at a 45° angle to the coating surface. Approximately 7.5 N of force was applied, advancing about 6.5 mm along the coating surface. The test was started with a softer pencil and gradually replaced with harder pencils until a pencil of a certain hardness grade caused a permanent scratch on the coating (i.e., scratched the coating). The previous hardness grade is the pencil hardness of the coating. At least three different locations were tested for each sample.

[0159] (8) Cross-cut adhesion test method: The test is conducted according to ISO 2409:2013 standard, "Paints and varnishes—Cross-cut test". Using a sharp cross-cutting tool (blade spacing 1mm or 2mm, depending on film thickness), cut six parallel lines perpendicular to each other on the coating surface, forming 25 or 100 squares. Securely adhere a pressure-sensitive adhesive tape (such as 3M 610 tape) to the cross-cut area, ensuring no air bubbles. Remove the tape smoothly and quickly at a 90° angle. Assess the adhesion grade based on the number of squares that detach from the substrate, referring to a standard chart. Grade 0 indicates completely smooth cut edges with no squares detached, representing the optimal grade.

[0160] Table 1

[0161]

[0162] The coating prepared in Example 1 meets the comprehensive requirements of high light transmittance, active cooling, long-lasting self-cleaning and long-term reliability.

[0163] Thanks to the excellent intrinsic electrical and optical properties of ITO, the coating performance obtained in Example 2 is further improved compared to Example 1, but the disadvantage is that the cost is higher.

[0164] The coating obtained in Example 3 has slightly lower performance than that in Example 1, but it achieves indium-free coating while maintaining good overall performance, making it more environmentally friendly and cost-effective.

[0165] The coating prepared in Example 4 has an average near-infrared reflectance of about 32% at room temperature. When the temperature rises above 70°C, due to the phase change of WO3, its average near-infrared reflectance can be dynamically increased to 45%, showing an adaptive heat insulation characteristic that the higher the temperature, the stronger the reflection. It is suitable for areas with large day-night temperature differences or high summer temperatures.

[0166] Example 5 is an optimization of Example 1, significantly improving the mechanical abrasion resistance of the coating to cope with strong wind and sand erosion environments such as deserts and Gobi. While basically maintaining the optical and thermal insulation performance of Example 1 (average light transmittance in the visible light region of 91.0%, temperature drop of 6.1℃), its abrasion resistance is greatly improved. After abrasion testing using the falling sand method (ISO 7784-2), the coating mass loss rate after 1000L of wear is 35% lower than that of Example 1, the water contact angle remains at 151°, and the adhesion is grade 0, meeting the long-term service requirements in areas with strong winds and sand.

[0167] The coating of Example 6 can be used in coastal environments with high temperature, high humidity, and severe salt spray corrosion, enhancing the interfacial adhesion and hydrolysis resistance between the coating and the substrate. The initial adhesion of the coating is grade 0; after 1000 hours of damp heat aging test at 85℃ / 85% RH, the cross-cut adhesion remains grade 0, while the coating of Example 1 showed an adhesion grade of 1 under the same conditions. Its salt spray resistance (ASTM B117, 5% NaCl, 500h) is excellent, with no blistering or peeling. The water contact angle is 152°, and the temperature drop is 6.0℃, providing reliable protection for coastal photovoltaic power plants.

[0168] Table 2

[0169]

[0170] Note: Due to the lack of self-cleaning function, the power boost rate of Comparative Example 4 decreased after a short period of testing due to dust accumulation. The data in Table 2 are the initial values.

[0171] The performance comparison between Comparative Example 1 and Example 1 shows that the introduction of functional materials such as infrared reflective nanomaterials is the fundamental reason why this invention upgrades from a common self-cleaning coating to a high-gain photovoltaic functional coating. It not only contributes directly and significantly to the cooling and energy-saving benefits (accounting for the main part of the overall gain), but also slightly improves the mechanical properties of the coating. This verifies the correctness and necessity of the technical approach of deeply synergistically designing the two functional dimensions of spectral selectivity and superhydrophobicity. Without either dimension, the synergistic gain effect exceeding expectations achieved by this invention cannot be realized. Furthermore, testing showed that after 1000 hours of UV damp heat aging, there was no reflective function, the water contact angle decreased by >10%, and no yellowing occurred.

[0172] The coating prepared in Comparative Example 2 exhibited poor storage stability and was prone to settling. The coating's light transmittance decreased to 88.5%, and its haze significantly increased. The average reflectance in the near-infrared region was only 31.2%, and the water contact angle was 147°. Its performance was comprehensively lower than that of Example 1, demonstrating that simple blending cannot achieve ideal dispersion and functional synergy of nanoparticles. Furthermore, testing showed that after 1000 hours of UV damp heat aging, the average reflectance in the near-infrared region decreased by >11%, the water contact angle decreased by >15%, and slight gloss loss occurred.

[0173] The coating prepared in Comparative Example 3 had a water contact angle of only 132°, failing to meet the superhydrophobic standard; its pencil hardness was 2H, but its flexibility was poor. Furthermore, microcracks appeared after 10 temperature cycles (-40℃ to 85℃), and its adhesion was rated as Grade 1. This demonstrates that ordinary resins cannot meet the stringent requirements of photovoltaic coatings for comprehensive mechanical properties and surface characteristics. In addition, testing showed that after 1000 hours of UV damp heat aging, the average reflectance in the near-infrared region decreased by >8%, the water contact angle decreased by >25%, and slight cracks appeared.

[0174] The coating surface obtained in Comparative Example 4 was relatively smooth, with a water contact angle of 82°, exhibiting hydrophilicity. Although its thermal insulation performance was comparable to that of Example 1 (reflectivity 36.8%), it completely lost its self-cleaning ability. Artificial dust accumulation tests showed that dust was difficult to wash away with water droplets, and long-term dust accumulation would severely negate the thermal insulation gain. Furthermore, tests showed that after 1000 hours of UV damp heat aging, the average reflectivity in the near-infrared region decreased by >6%, indicating a lack of hydrophobicity.

[0175] The coating prepared in Comparative Example 5 exhibited an optimal average transmittance of 71.5% in the visible light region, an average reflectance of 28.5% in the near-infrared region, a water contact angle of 158°, and a water roll-off angle of 8°. The thermal insulation temperature difference was 4.2°C, and the overall module power was increased by approximately 3.0%. Its transmittance, thermal insulation performance, and power generation gain were significantly lower than any embodiment of this invention (such as Example 1). Furthermore, testing revealed that after 1000 hours of UV damp heat aging, the average reflectance in the near-infrared region decreased by >12%, the water contact angle decreased by >10%, and slight yellowing occurred.

[0176] Figure 1 The solar spectral characteristics transmission curves of the coated samples of Examples 1, 2, 4, and 5 of this invention and the blank control photovoltaic glass without coating are shown in the comparison graph. Figure 1 All curves show a high transmittance plateau in the visible light region (380nm-780nm); in the near-infrared region (780nm-2500nm): the two curves of Example 1 and Example 2 of this invention show a significant and selective decrease in transmittance (i.e., an increase in reflectance), while the curve of the coating in Comparative Example 5 decreases gently, and the curve of the coating in Comparative Example 4 with only heat insulation function is similar but has no self-cleaning property. Figure 1 This directly proves that the present invention has successfully integrated and optimized spectral selectivity characteristics.

[0177] Figure 2 These are infrared thermographic comparison images of the coating samples of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 5 of the present invention under simulated sunlight. Under the same sunlight simulator irradiation, the surface temperature of the glass coated with the coatings of Comparative Example 2 and Example 1 of the present invention (mainly blue and green) is significantly lower than that of the glass coated with the coatings of Comparative Example 1 and Comparative Example 5 (mainly yellow and red). Figure 2The labeled average temperature (Avg) data corresponds to the temperature drop data (ΔT) in Table 1, which intuitively and powerfully demonstrates that the coating of the present invention has an excellent effect in reducing the operating temperature of the component.

[0178] Figure 3 This is a bar chart comparing the retention rates of key performance characteristics of the coating samples from Examples 1, 1, and 2 of this invention after accelerated aging. The test method for performance retention after UV-damp heat aging: A composite aging test was developed according to the requirements of the relevant accelerated aging test sequence in IEC 61215-2:2021 "Design Qualification and Type Approval of Ground-mounted Photovoltaic Modules". The coating samples were placed in a UV-damp heat composite aging test chamber for cyclic testing. A typical cycle included: maintaining at 85°C and 85% relative humidity for 20 hours, followed by irradiation at 60°C with a wavelength of 280nm-400nm and a total irradiance of 15kWh / m². 2 The sample was exposed to ultraviolet light for 4 hours. The cumulative aging time was 1000 hours. Before and after the aging test, the key performance indicators of the sample were tested, including water contact angle, average reflectance in the near-infrared region, and average transmittance in the visible light region. The performance retention rate was calculated as follows: Performance retention rate (%) = (Performance value after aging / Initial performance value before aging) × 100%. Figure 3 In the figure, the bar charts representing the retention rates of the three performance parameters of Example 1 of the present invention are significantly higher than the corresponding bar charts of the photovoltaic glass of Comparative Example 1 and Comparative Example 2. This quantitatively proves that the coating of the present invention has made progress in long-term environmental durability due to the introduction of a particle passivation and composite stabilization system, thus ensuring the persistence of its gain effect.

[0179] A comparative schematic diagram of the microstructure (SEM) of the coatings obtained in Example 1 and Comparative Example 2 is shown below. Figure 4 As shown, Figure 4 Image A shows the coating surface produced using the gradient mixing process of Example 1 of this invention, where functional nanoparticles are uniformly distributed and the micro / nano structure is ordered. Figure 4 The coating surface of Comparative Example 2, which uses a simple one-time blending process, shows severe particle agglomeration and a rough, uneven structure. Figure 4 The microscopic level demonstrates the criticality and necessity of the core preparation process of this invention in achieving coating uniformity, high light transmittance, and stable performance.

[0180] Example 7

[0181] This embodiment is a simplified application variant coating adapted to roller / brush coating processes, demonstrating the adaptability of the invention's formulation system to simple, low-cost application techniques (such as on-site construction or small-scale maintenance of distributed power plants). By adjusting rheology and optimizing application methods, high-performance coatings can be applied with simple tools while maintaining excellent functionality.

[0182] The difference between this embodiment and Embodiment 1 is that:

[0183] 1. Raw material adjustment: Increase the amount of rheology modifier (nonionic polyurethane associative thickener) from 1.0% to 2.0%-2.5%, and 2.25% is used in this example.

[0184] 2. Coating preparation process: In step S3, the final viscosity of the system is adjusted to 1500 mPa·s-2500 mPa·s (measured at 25°C) by adjusting the amount of rheology modifier and water. In this embodiment, 2000 mPa·s is used. This viscosity range provides good anti-sagging properties and roller coating feel, ensuring that the wet film has a certain thickness and uniformity.

[0185] 3. Coating preparation process, specifically:

[0186] First, thoroughly clean the photovoltaic glass with detergent and deionized water, and then wipe it with anhydrous ethanol to ensure that the surface is clean and dry.

[0187] Apply an appropriate amount of coating using a short-pile fiber roller. Apply the coating to the glass surface in a single pass at a uniform speed, avoiding repeated rolling that could lead to uneven film thickness. The resulting wet film thickness is approximately 80μm-120μm.

[0188] The coated photovoltaic glass was placed horizontally in a clean, room temperature (25℃±5℃) environment. After surface drying for about 45 minutes, it was cured in a 60℃ oven for 3 hours. The thickness of the dry film formed after curing was 8μm-12μm, and a spectrally selective superhydrophobic photovoltaic gain coating was obtained. Its performance and comparative analysis with Example 1 are shown in Table 3 below.

[0189] Table 3

[0190]

[0191] Manual roller coating cannot achieve the ultra-thin thickness of ultrasonic spraying; its optimal thickness is 10.0 μm ± 2.0 μm. Increasing the film thickness introduces slight light scattering, resulting in a slight decrease in the average transmittance in the visible light region compared to sprayed films, but it is still better than most comparative examples. Since the total amount of functional particles such as infrared-reflective nanomaterials increases proportionally with film thickness, infrared reflectivity and active cooling effects are maintained. Even in thicker film layers, micro-nano rough structures can still be effectively formed, thus maintaining a water contact angle >150°.

[0192] Example 8

[0193] The application scenario of this embodiment is for on-site renovation of photovoltaic power stations that have been installed and connected to the grid. The core constraint of this scenario is that the photovoltaic modules are fixedly installed at an angle of 8°-30° and cannot be moved. They must be constructed and cured in situ in an outdoor environment.

[0194] The difference between this embodiment and Embodiment 1 is that:

[0195] 1. Raw material adjustment: Increase the amount of rheology modifier (nonionic polyurethane associative thickener) from 1.0% to 2.5%-3.0%, and 2.75% is used in this embodiment.

[0196] 2. Coating Preparation Process: In step S3, by adjusting the amount of rheology modifier and water, ensure that the coating reaches surface dryness on the inclined substrate within 5-10 minutes, preventing dripping. For manual roller coating, the final application viscosity is 2000 mPa·s-3500 mPa·s (25°C); for machine spraying, the final application viscosity is 100 mPa·s-300 mPa·s (25°C).

[0197] 3. The specific process for on-site coating application is as follows:

[0198] (1) Manual roller coating

[0199] Tools: Short-haired (6mm-9mm) roller and extension rod.

[0200] Technique: Unidirectional roller coating from top to bottom, applying uniform pressure, avoiding back-rolling, and using single-pass forming.

[0201] Film thickness control: target wet film thickness 60μm-100μm, corresponding to dry film thickness 6μm-10μm.

[0202] Curing: After coating, the components are kept at their original installation angle and cured in situ in an outdoor environment. After surface drying, they are unaffected by wind and sand, and their performance is fully established after 5-7 days.

[0203] (2) Machine spraying

[0204] Equipment: Portable airless sprayer, equipped with fan-shaped nozzles (orifice diameter 0.4mm-0.6mm).

[0205] Parameters: Spraying pressure 80bar-120bar, gun distance 20cm-30cm, move at a constant speed from top to bottom, spray overlap 50%.

[0206] Film thickness control: Target dry film thickness 4μm-6μm.

[0207] Curing: Same curing scheme as manual roller coating.

[0208] Following the above process, the coating performance was verified on a simulated tilt test bench and in an actual pilot power station. The results are shown in Table 4 below.

[0209] Table 4

[0210]

[0211] Example 8 demonstrates the technical feasibility of the coating of the present invention in harsh real-world application scenarios, and establishes the industrial applicability of the technology by disclosing complete and repeatable engineering parameters; it clarifies the entire process from formula fine-tuning to construction control and performance assurance.

[0212] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A spectrally selective superhydrophobic photovoltaic gain coating, characterized in that, The coating comprises the following raw materials by weight percentage: The aqueous resin matrix comprises 45%-65%, wherein the aqueous resin matrix is ​​a hybrid emulsion formed by fluorosilicone modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer. Infrared reflective nanomaterials: 5%-10%; Hydrophobic nanoparticles 3%-6%; Dispersant 1%-3%; Silane coupling agent 1%-3%; Stabilizer 0.5%-2%; Rheology modifiers: 0.5%-1.5%; Organosilicon defoamer 0.2%-0.5%; The remaining amount is water; replenish to 100%. The method for preparing the aqueous resin matrix includes the following steps: Hydroxyethyl methacrylate, isophorone diisocyanate, and catalysts dibutyltin dilaurate and perfluorooctyl ethanol are reacted to obtain a fluorocarbon chain-terminated product; hydroxyethyl acrylate, γ-(methacryloyloxy)propyltrimethoxysilane, and polymerization inhibitor hydroquinone are added to the fluorocarbon chain-terminated product to obtain a fluorosilane functional monomer. Using the fluorinated silane functional monomer and acrylate monomer as raw materials, copolymerization was carried out by a pre-emulsified semi-continuous seed emulsion polymerization method to obtain a fluorinated silicone modified acrylic resin emulsion. Polycaprolactone diol, isophorone diisocyanate and dimethylolpropionic acid were reacted to obtain a prepolymer; the prepolymer was neutralized with triethylamine and then dispersed in water under high-speed shear, and ethylenediamine was added for post-chain extension. After solvent removal, a hydroxyl-terminated polyurethane prepolymer dispersion was obtained. The hydroxyl-terminated polyurethane prepolymer dispersion and the fluorosilicone-modified acrylic resin emulsion were mixed at a solid mass ratio of (30-40):(70-60), heated, and an initiator was added to react, resulting in a hybrid emulsion formed by fluorosilicone-modified acrylic resin and hydroxyl-terminated aliphatic polyurethane prepolymer.

2. The spectrally selective superhydrophobic photovoltaic gain coating according to claim 1, characterized in that, The effective component of the infrared reflective nanomaterial is selected from one of antimony-doped tin dioxide, indium tin oxide, aluminum-doped zinc oxide, fluorine-doped tin oxide, gallium-doped zinc oxide, tungsten oxide, or doped tungsten oxide; the doped tungsten oxide is molybdenum-doped tungsten oxide, niobium-doped tungsten oxide, or titanium-doped tungsten oxide.

3. The spectrally selective superhydrophobic photovoltaic gain coating according to claim 1, characterized in that, The hydrophobic nanoparticles are made of nano-silica with a fluorinated silane surface modified.

4. The spectrally selective superhydrophobic photovoltaic gain coating according to claim 1, characterized in that, The raw materials of the coating also include 0.1%-2% by mass of high-hardness nano-wear-resistant particles, which are selected from silicon carbide, boron nitride or aluminum oxide.

5. The spectrally selective superhydrophobic photovoltaic gain coating according to claim 1, characterized in that, The silane coupling agent is an epoxy silane; The dispersant is a polymeric block copolymer dispersant; the polymeric block copolymer dispersant is an ammonium polyacrylate, an ammonium polycarboxylate, or an amphiphilic block copolymer containing anchoring groups and polyether solvation chains; The stabilizer is a composite system of benzotriazole UV absorbers and low-alkaline hindered amine light stabilizers in a mass ratio of 1:0.8-1.2; the benzotriazole UV absorber is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol or 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole; the low-alkaline hindered amine light stabilizer is bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate or poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexamethylenediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}; The rheology modifier is a nonionic polyurethane associative thickener.

6. A method for preparing a spectrally selective superhydrophobic photovoltaic gain coating according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: Dispersant, water, infrared reflective nanomaterials, and hydrophobic nanoparticles are mixed, and high-hardness wear-resistant nanoparticles can be selectively added. After high-shear dispersion and grinding, a uniform functional slurry is obtained. The aqueous resin matrix and stabilizer are mixed evenly to obtain the resin mother liquor; Under stirring conditions, the functional slurry is slowly added to the resin mother liquor. After gradient mixing, a silane coupling agent is added to carry out an interfacial coupling reaction. After the reaction is completed, water is added for preliminary dilution to adjust the viscosity of the system. Then, a rheology modifier is added, followed by water to adjust the viscosity of the system to 80 mPa·s to 120 mPa·s. After the viscosity is adjusted, an organosilicon defoamer is added and stirred evenly. After standing and aging, the mixture is filtered to obtain a spectrally selective superhydrophobic photovoltaic gain coating.

7. The method for preparing a spectrally selective superhydrophobic photovoltaic gain coating according to claim 6, characterized in that, The high-shear dispersion is performed at a speed of 5000rpm-8000rpm for 20min-30min; the grinding step is as follows: grinding with a basket mill for 1h-2h until the fineness of the functional slurry is ≤20μm.

8. The method for preparing a spectrally selective superhydrophobic photovoltaic gain coating according to claim 6, characterized in that, The functional slurry is slowly added to the resin mother liquor, which is stirred at 200 rpm to 400 rpm, over a period of 30 to 60 minutes.

9. The application of the spectrally selective superhydrophobic photovoltaic gain coating according to any one of claims 1 to 5, characterized in that, The coating is applied to the light-receiving surface of the photovoltaic glass to form a spectrally selective superhydrophobic photovoltaic gain coating.

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