CN117025076B - A self-cleaning anti-reflective nanofilm and its preparation method - Google Patents

Abstract

This application discloses a self-cleaning anti-reflective nanofilm and a preparation method thereof. It is specifically formed by coating and curing a nanofilm cross-linked prepolymer. The nanofilm cross-linked prepolymer is a silicon-fluoropolymer and a fluorine-modified polymer. The cross-linking reactant of chemical nano-silica; the silicon fluoropolymer is a mixture of fluorocarbon resin and silicone-modified isocyanate cross-linking agent; the fluorine-modified nano-silica is produced by the sol-gel method, Clustered nanosilica with silica spherical particle cores synthesized through alkali and acid catalysis and modified in situ by fluorination; effectively solves the problem that the current photovoltaic panel coating cannot simultaneously take into account self-cleaning, anti-reflection and weather resistance properties. .

Description

A self-cleaning anti-reflective nanofilm and its preparation method

Technical field

The present disclosure relates to an anti-reflective coating film on the surface of optical equipment such as solar photovoltaic panels, specifically a coating film that takes into account self-cleaning, weather resistance and anti-reflective properties and a preparation method thereof.

Background technique

The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.

In various practical applications of renewable energy, solar photovoltaic cells have become the main way to utilize solar energy due to their advantages of high efficiency, safety and environmental friendliness. With the diversification of photovoltaic module installation areas, photovoltaic modules not only have to face the test of high/low temperature, high humidity, drought, ultraviolet radiation, acid rain and salt spray, but also face the deposition of dirt, sand and other stains. In recent years, in order to alleviate and solve the problems of dust and various pollutant deposition during the operation of photovoltaic modules and to improve the light transmittance and power generation efficiency of the modules, researchers have carried out a lot of work, such as:

Chinese patent CN101805135B uses the sol-gel method to achieve a high-refractive index metal oxide/low-refractive index silica double-layer coating on the glass surface. Compared with a single-layer anti-reflective coating, this double-layer coating can be realized in the visible light band Higher transmittance can improve the power generation efficiency of photovoltaic modules. However, this double-layer coating does not show self-cleaning and lyophobic properties, and does not meet the self-cleaning requirements of photovoltaic modules under real working conditions.

Chinese patent CN102531406B, by rolling an anti-reflective coating liquid containing metal oxides such as silica, titanium dioxide, zirconium dioxide and ceria as well as stabilizers and surface modifiers on the surface of photovoltaic glass, and then heat treating and tempering to obtain the glass. The anti-reflective coating on the surface can increase the light transmittance of the glass by 2.5% in the visible wavelength range. However, the self-cleaning performance of this coating is limited, especially it can only achieve hydrophobicity, but cannot achieve lyophobicity for oily media and organic solvents. Additionally, the weather resistance of this anti-reflective coating is unknown.

Chinese patent CN113088190B, through direct mixing of fluorine-containing siloxane precursor and siloxane prepolymer, and hydrolysis/condensation of the ethoxy or methoxy groups in the precursor and prepolymer under alkaline conditions, A fluorine-containing organopolysiloxane coating film with superhydrophobic and self-cleaning properties was prepared. Although it has excellent hydrophobicity and self-cleaning properties, the polymer coating does not show anti-reflective properties and is difficult to use on optical equipment such as photovoltaic glass.

In summary, existing self-cleaning and anti-reflective coatings for photovoltaic panels still have many shortcomings. First of all, most anti-reflective coatings for optical equipment on the market are composed of low-refractive-index inorganic nanoparticles (such as silica), which are easily contaminated in outdoor environments, causing loss of anti-reflective properties. In addition, with the development of superwetting surface science, many superhydrophilic or superhydrophobic anti-reflective coatings have been developed in recent years, but they all have fine micro/nano structures, which makes them difficult to withstand long-term outdoor wind and sand erosion, and It is not lyophobic to oily media and organic solvent media with low surface tension and is easily contaminated. Finally, the existing self-cleaning anti-reflective coatings have poor weather resistance and cannot meet the needs of long-term stable operation of photovoltaic modules. Therefore, there is still an urgent need to develop multifunctional and durable photovoltaic panel coatings that can take into account self-cleaning, anti-reflective and fully lyophobic properties.

It should be noted that the information disclosed in the above background section is only used to enhance understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art.

Contents of the invention

In view of this, the present disclosure provides a self-cleaning anti-reflective nanofilm, which solves the problem that current photovoltaic panel coating films cannot simultaneously take into account self-cleaning, anti-reflective and weather-resistant properties.

In addition, the present disclosure also provides a method for preparing the self-cleaning anti-reflective nanofilm.

In the first aspect, the self-cleaning anti-reflective nanofilm is formed by coating and curing a nanofilm cross-linked prepolymer, wherein:

The nanomembrane cross-linked prepolymer is a cross-linking reaction product of silicon fluoropolymer and fluorine modified nano-silica;

The silicone fluoropolymer is a mixture of fluorocarbon resin and silicone-modified isocyanate cross-linking agent;

The fluorine-modified nanosilica is a clustered nanosilica with a core of silica spherical particles that is synthesized through a sol-gel method, catalyzed by alkali and acid, and modified by in-situ fluorination.

In the second aspect, the preparation method of the self-cleaning anti-reflective nanofilm described in the first aspect includes:

Obtain fluorocarbon resins containing hydroxyl and carboxyl groups;

After adding organic silicon to a mixture containing isocyanate, catalyst and solvent, the product of the reaction in a nitrogen atmosphere and stirring state is silicone-modified isocyanate;

Mix the fluorocarbon resin and the silicone-modified isocyanate at a mass ratio of 3-10:1 to obtain a silicone-fluoropolymer;

The silicon fluoropolymer and modified nano-silica are mixed to obtain the nano-membrane cross-linked prepolymer.

In the present disclosure and possible embodiments, the fluorocarbon resin includes chlorotrifluoroethylene and alkyl vinyl ester copolymer resin, tetrafluoroethylene and alkyl vinyl ester copolymer resin, tetrafluoroethylene and alkyl vinyl ether Copolymer resins and chlorotrifluoroethylene and alkyl vinyl ether copolymer resins; and/or,

The silicone includes reactive polydimethylsiloxane with single or double ends or side chains containing hydroxyl or amino groups; and/or,

The isocyanate is toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, terephthalene diisocyanate, dimethylbiphenyl diisocyanate, polymethylene polyphenyl isocyanate, hexamethylene diisocyanate (or its trimer), trimethylhexamethylene diisocyanate, isophorone diisocyanate, tetramethylphenylmethylene diisocyanate, methylcyclohexyl isocyanate, cyclohexane dimethylene diisocyanate One or more.

In the present disclosure and possible embodiments, the molecular weight of the organic silicon is Mn=500-20000 g/mol; and/or,

The catalyst is at least one of dibutyltin dilaurate and stannous isooctate; and/or,

The solvent is acetone, ethyl ketone, ethylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate and dipropylene glycol. At least one kind of dimethyl ether.

In the present disclosure and possible embodiments, the preparation method of silicone-modified isocyanate includes:

Take the organic silicon equivalent to 0.5-20.0% of the total mass of the fluorocarbon resin and the isocyanate, and add it to the isocyanate cross-linking agent, the catalyst and the solvent. The amount of the catalyst is the total 0.5-3.0% of the solid mass; under nitrogen atmosphere and stirring state, react at a constant temperature of 60-90°C for 1-12 hours to obtain the silicone isocyanate cross-linking agent.

In the present disclosure and possible embodiments, the synthesis method of fluorine-modified nanosilica includes:

Using the sol-gel method, alkali-catalyzed silica sol is synthesized through alkali catalysis, and the alkali-catalyzed silica sol is heat-treated to obtain a concentrated silica sol; the concentrated silica sol and fluorinated modifier are added to the acid-catalyzed synthesis of silica sol. The acid-catalyzed synthesis reaction is carried out in the reaction solution to obtain the fluorine-modified nanosilica.

In the present disclosure and possible embodiments, the alkali catalyst for alkali catalysis is at least one of ammonia water, sodium hydroxide, and potassium hydroxide; and/or,

The acid catalyst for acid catalysis is at least one of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid; and/or,

The fluorinated modifier is 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane, 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane, 1H, 1H, 2H, 2H -Perfluorodecyltrimethoxysilane, at least one of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane; and/or,

The particle size of the cluster nanosilica is 10-500 nm.

In the present disclosure and possible embodiments, the synthesis method of concentrated silica sol includes: adding the alkali catalyst to a uniform mixture of ethyl orthosilicate and absolute ethanol at a volume ratio of 1:10-50 In, stir the reaction at room temperature for 12-24 h to obtain alkali-catalyzed silica sol; heat-treat the alkali-catalyzed silica sol to remove the absolute ethanol and the alkali catalyst to obtain the concentrated silica sol; and/or,

The acid-catalyzed synthesis method includes: after mixing ethyl silicate:water:acid catalyst in a volume ratio of 6-10:1-4:1, add the absolute ethanol dispersion of the concentrated silica sol at room temperature. After stirring for 12-24 hours, a fluorinated modifier is added to the reaction solution. The volume of the fluorinated modifier is 1-10% of the total volume of the system. The reaction product is subjected to rotary evaporation, vacuum distillation, and vacuum drying. After removing the solvent, the cluster nanosilica is obtained.

In the present disclosure and possible embodiments, the fluorine-modified nanosilica is dispersed in a diluent to obtain a dispersion with a solid content of 5-50%;

Mix the fluorocarbon resin:silicone modified isocyanate at a mass ratio of 3-10:1 and dilute it with the diluent to a silicon fluoropolymer solution with a solid content of 20-50%;

Under the state of ultrasonic for 10-30 minutes and stirring for 10-60 minutes, the silica dispersion is dropped into the silicon fluoropolymer solution and a cross-linking reaction occurs to obtain the nano-membrane cross-linked prepolymer.

In the present disclosure and possible embodiments, the mass ratio of the silicone fluoropolymer solution to the dispersion is 0.07-0.6:1; and/or,

The diluent is at least one of butyl acetate, butyl acetate, propylene glycol methyl ether acetate and xylene; and/or,

The curing is performed at room temperature for 24-48 hours, or at 50-120°C for 1-12 hours; the coating film thickness is 100-900 nm.

In the self-cleaning anti-reflective nanofilm of the present disclosure, the nanomembrane cross-linked prepolymer forming the film contains silicone fluoropolymer and modified nanosilica, and the silicone fluoropolymer contains fluorocarbon resin and silicone modified Isocyanate cross-linking agent is used to cross-link the isocyanate group with the fluorocarbon resin branched hydroxyl/carboxyl group and the nano-silica surface hydroxyl group to obtain a nanomembrane cross-linked prepolymer, which is further used to obtain Nanofilm; firstly, because the modified nanosilica in the cross-linked prepolymer is a cluster material with a core of silica spherical particles, it increases the multiple refraction of incident light inside the coating film/ Reflection enhances the anti-reflective performance of the nano-coating film, and because the nano-silica has been modified by fluorination, the nano-coating film has low surface energy characteristics, further strengthening the self-cleaning performance of the anti-reflective nano film; second aspect , the high bond energy of the C-F bonds in the fluorocarbon resin and the Si-O-Si bonds in the silicone, as well as the inorganic nano-silica particles, enhance the weather resistance of the nano-membrane, enabling it to withstand thousands of hours of UV irradiation and moisture-heat damage; thirdly, by modifying isocyanate with silicone, it is ensured that silicone can give the nano-coating film a certain degree of fully lyophobicity and self-cleaning properties, and is conducive to the refractive index matching between fluorocarbon resin and nano-silica particles. , further meeting the demand for high light transmittance in optical equipment; in addition, the nano-coating film has a high contact angle and extremely low sliding angle for water-based, oil-based and organic solvents, and various types of droplets can easily escape from the surface of the nano-film. It can slide off, and during the sliding process, dust and other stains on the surface of the nanofilm can be taken away to achieve efficient self-cleaning. In summary, the self-cleaning anti-reflective nanofilm of the present invention can achieve self-cleaning, anti-reflective and weather-resistant properties at the same time.

Description of the drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

Figure 1 is the water contact angle result of the nanofilm of Comparative Example 2;

Figure 2 is the light transmittance result of the nanofilm of Comparative Example 2;

Figure 3 is the water contact angle result of the nanofilm of Comparative Example 3;

Figure 4 is the light transmittance result of the nanofilm of Comparative Example 3;

Figure 5 is a TEM image of the clustered nanosilica particles of Example 1;

Figure 6 is the water contact angle result of the nanomembrane surface in Example 1;

Figure 7 is the light transmittance result of the nanofilm of Example 1;

Figure 8 is the short-circuit current density of the battery die, and the results of the battery short-circuit circuit density-voltage curve after the ultra-white glass coated with the nanofilm of Example 1 is covered on the photovoltaic cell, contaminated, and cleaned;

Detailed ways

The present disclosure is described below based on examples, but it is worth noting that the present disclosure is not limited to these examples. In the detailed description of the disclosure that follows, certain specific details are set forth in detail. However, those parts which are not described in detail can also be fully understood by those skilled in the art.

At the same time, unless the context clearly requires it, the words "including", "includes" and other similar words in the entire specification and claims should be interpreted as an inclusive meaning rather than an exclusive or exhaustive meaning; that is, as a "including but not exclusive" meaning. limited to" meaning.

In order to enable those skilled in the art to better understand the technical solutions of the present application, the preferred solutions of the present application are described in detail below through specific examples and in conjunction with the accompanying drawings. In this application, all equipment and raw materials can be purchased from the market, and the test methods and testing methods are conventional methods.

The fluorocarbon resin used in the following examples of the present disclosure was purchased from DAIKIN.

Example 1

1. Preparation of nanomembrane cross-linked prepolymer

Step (1): Add 0.03 g of hydroxyl-terminated polydimethylsiloxane into a flask containing 0.4 g of hexamethylene diisocyanate trimer, 0.025 g of dibutyltin dilaurate and 1 g of propylene glycol methyl ether. , stir under a nitrogen atmosphere, keep the temperature at 90°C, and react for 1 h to obtain a silicone-modified hexamethylene diisocyanate trimer; 4 g of tetrafluoroethylene and alkyl vinyl ester copolymer resin, 0.4 g The silicone-modified hexamethylene diisocyanate trimer was dissolved in 5 g xylene by ultrasonic for 10 min and stirred for 30 min to obtain a silicon-fluoropolymer solution for later use;

Step (2): Mix 2 mL of ethyl orthosilicate and 20 mL of absolute ethanol, keep stirring for 5 min, add 5 mL of ammonia solution, keep stirring at room temperature, and react for 15 h to obtain a base-catalyzed silica sol; The alkali-catalyzed silica sol was heated, the solvent and alkali catalyst were removed, and then dispersed again in 40 mL of absolute ethanol. 2.4 mL of ethyl orthosilicate, 0.8 mL of deionized water, and 0.4 mL of sulfuric acid were added, and the mixture was stirred and reacted at room temperature. After 12 hours, add 0.45 mL of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and continue the reaction for 3 hours; finally, the solvent is removed by rotary evaporation to obtain clustered nanosilica;

Step (3): Disperse 2 g of clustered nanosilica in 20 g of xylene, add dropwise into the above silicon fluoropolymer solution, ultrasonic for 10 min, stir for 30 min, and obtain nanomembrane cross-linked prepolymer. things.

2. Preparation of self-cleaning anti-reflective nanofilm

1: Fix the ultra-white glass substrate on the imprinting table, and roll the above-mentioned nanofilm cross-linked prepolymer onto the surface of the substrate;

2: Place the above substrate coated with the nanomembrane cross-linked prepolymer for heat treatment in a blast drying oven at 120°C for 2 hours to obtain the final solidified nanomembrane with a thickness of about 300 nm.

Example 2

1. Preparation of nanomembrane cross-linked prepolymer

Step (1): Add 0.8 g of amino-terminated polydimethylsiloxane into a flask containing 0.5 g of isophorone diisocyanate, 0.01 g of dibutyltin dilaurate and 1.5 g of dipropylene glycol butyl ether. Stir under nitrogen atmosphere, keep the temperature at 60°C, and react for 12 hours to obtain silicone-modified isophorone diisocyanate; 4 g of chlorotrifluoroethylene and alkyl vinyl ester copolymer resin, 0.5 g of silicone-modified The isophorone diisocyanate was dissolved in 5 g of propylene glycol methyl ether acetate by ultrasonic for 10 minutes and stirred for 30 minutes to obtain a silicon fluoropolymer solution for later use;

Step (2): Mix 2.5 mL ethyl orthosilicate and 75 mL absolute ethanol, keep stirring for 10 min, add 6 mL sodium hydroxide solution, keep stirring at room temperature, and react for 24 h to obtain alkali-catalyzed silica sol ; After removing the solvent and catalyst of the alkali-catalyzed silica sol, disperse it in 50 mL of absolute ethanol again, continue to add 3 mL of ethyl orthosilicate, 0.5 mL of deionized water and 0.3 mL of sulfuric acid, and keep stirring at room temperature. After reacting for 18 hours, add 5 mL of 1H, 1H, 2H, 2H-perfluorodecyltrimethoxysilane, and continue the reaction for 4 hours; finally, the solvent is removed by rotary evaporation to obtain clustered nanosilica;

Step (3): Disperse 3 g of clustered nanosilica in 18 g of propylene glycol methyl ether acetate, dropwise into the above silicon fluoropolymer solution, ultrasonic for 10 min, and stir for 45 min to obtain nanomembrane cross-linking Prepolymer.

2. Preparation of self-cleaning anti-reflective nanofilm

1: Place the ultra-white glass substrate on the platform, and spray the above-mentioned nanofilm cross-linked prepolymer on the surface of the substrate;

2: Place the substrate coated with the nanomembrane cross-linked prepolymer at room temperature for 36 hours to obtain the final cured nanomembrane with a thickness of about 900 nm.

Example 3

1. Preparation of nanomembrane cross-linked prepolymer

Step (1): Add 0.2 g of hydroxyl-terminated polydimethylsiloxane into a flask containing 0.3 g of hexamethylene diisocyanate, 0.01 g of dibutyltin dilaurate and 2 g of propylene glycol butyl ether, and mix under nitrogen Stir in the atmosphere, keep the temperature at 80°C, and react for 6 hours to obtain a silicone-modified hexamethylene diisocyanate cross-linking agent; 2.4 g of chlorotrifluoroethylene and alkyl vinyl ether copolymer resin, 0.3 g of silicone The modified hexamethylene diisocyanate was dissolved in 6 g of butyl acetate by ultrasonic for 10 min and stirred for 30 min to obtain a silicon fluoropolymer solution for later use;

Step (2): Mix 3 mL of ethyl orthosilicate and 100 mL of absolute ethanol, keep stirring for 10 min, add 4 mL of potassium hydroxide solution, keep stirring at room temperature, and react for 18 h to obtain alkali-catalyzed silica sol ; After removing the solvent and catalyst of the alkali-catalyzed silica sol, disperse it in 60 mL of absolute ethanol again, continue to add 4 mL of ethyl orthosilicate, 0.5 mL of deionized water and 0.6 mL of hydrochloric acid, and keep stirring at room temperature. After reacting for 20 hours, add 4 mL of 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane and continue the reaction for 6 hours; finally, the solvent is removed by rotary evaporation to obtain clustered nanosilica;

Step (3): Disperse 2 g of clustered nanosilica in 22 g of butyl acetate, add dropwise into the above silicon fluoropolymer solution, ultrasonic for 10 min, and stir for 60 min to obtain the nanomembrane cross-linking preset. Polymer.

2. Preparation of self-cleaning anti-reflective nanofilm

1: Fix the ultra-white glass substrate on the imprinting table, and roll the above-mentioned nanofilm cross-linked prepolymer onto the surface of the substrate;

2: Place the above-mentioned substrate coated with the nanomembrane cross-linked prepolymer for heat treatment in a blast drying oven at 100°C for 3 hours to obtain the final solidified nanomembrane with a thickness of about 100 nm.

Comparative example 1

Step (1): Dissolve 4 g of chlorotrifluoroethylene and alkyl vinyl ester copolymer resin and 0.24 g of isophorone diisocyanate in 5 g of butyl acetate by ultrasonic for 10 min and stir for 20 min to obtain a coating liquid ;

Step (2): Fix the ultra-white glass substrate on the imprinting table, and apply the above coating liquid on the surface of the substrate;

Step (3): Place the above-mentioned substrate coated with the coating liquid in a blast drying oven at 80°C for heat treatment for 2 hours to obtain a final cured coating with a thickness of approximately 500 nm.

Comparative example 2

Step (1): Dissolve 4 g of tetrafluoroethylene and alkyl vinyl ester copolymer resin, 0.25 g of hexamethylene diisocyanate, and 0.02 g of hydroxyl-terminated polydimethylsiloxane by ultrasonic for 10 min, and stir for 20 min. In 6 g butyl acetate, a coating liquid was obtained;

Step (2): Mix the above coating liquid with the silica dispersion, ultrasonic for 10 minutes, and stir for 30 minutes to obtain a mixed coating liquid;

Step (3): Place the ultra-white glass substrate on the platform, and spray the above mixed coating liquid on the surface of the substrate;

Step (4): Place the substrate coated with the coating liquid above for heat treatment in a blast drying oven at 100°C for 2 hours to obtain a final solidified nanofilm with a thickness of about 500 nm.

Comparative example 3

Step (1): Add 1 g of commercially available alkali-catalyzed synthesized silica nanoparticles to 50 mL of absolute ethanol, 5 mL of ammonia water, and 0.6 mL of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane. In the mixed solution, ultrasonicate for 20 min, stir and react at room temperature for 18 h, filter the mixed solution, wash with ethanol three times, and dry the obtained filter cake in an oven at 80°C for 12 h to obtain fluorinated silica nanoparticles;

Step (2): Dissolve 4 g of chlorotrifluoroethylene and alkyl vinyl ester copolymer resin and 0.4 g of hexamethylene diisocyanate trimer in 5 g of butyl acetate by ultrasonic for 10 min and stir for 30 min to obtain Coating liquid; disperse 0.025 g fluorinated silica nanoparticles in 3 g butyl acetate by ultrasonic for 30 minutes to obtain a fluorinated silica dispersion;

Step (3): Mix the above coating liquid with the fluorinated silica dispersion, ultrasonic for 10 minutes, and stir for 30 minutes to obtain a mixed coating liquid;

Step (4): Fix the ultra-white glass substrate on the imprinting table, and apply the above coating liquid on the surface of the substrate;

Step (5): Place the above-mentioned substrate coated with the coating liquid in a blast drying oven at 90°C for heat treatment for 2 hours to obtain a final solidified nanofilm with a thickness of approximately 500 nm.

Further, in order to more clearly illustrate the advantages of the present disclosure, the coating films of the above-mentioned embodiments and comparative examples were subjected to performance tests, and the test methods were as follows:

(1) Water/oil/organic solvent contact angle and sliding angle test

Use a contact angle meter to measure the static contact angle of a volume of 10 μL of deionized water, 10 μL of sunflower oil, and 10 μL of absolute ethanol on the coating surface. Use a volume of 30 μL of deionized water, 15 μL of sunflower seeds, and For the dynamic sliding angle of oil and 15 μL of absolute ethanol on the coating surface, take the average of the measured values at at least 5 different positions as the final static contact angle or dynamic sliding angle of the coating.

(2) Light transmittance test

A UV-visible spectrophotometer was used to measure the light transmittance of the nanofilm coated on the float ultra-white glass substrate in the wavelength range of 300-800 nm, with air as the blank background.

(3) Short circuit current density recovery rate (solar cell characteristics) test

A solar simulator (AM 1.5 G, 100 mW/cm ² ) was used with a data source meter to collect the short-circuit current-voltage curve of the monocrystalline silicon cell. During the test, ultra-white glass with a coated sample was placed above the cell. Dust was sprayed on the surface of the coating sample through an electric powder spray gun to simulate the dust deposition phenomenon in nature, and the dust deposition density (g/cm ² ) was controlled to be consistent. The dusty coating samples were then cleaned using deionized water of the same quality at the same dripping speed to simulate rainfall and self-cleaning processes in nature. The short circuit current density recovery rate (%) is defined as follows:

Short-circuit current density recovery rate = (Battery short-circuit current density of the coated glass sample after covering and cleaning - Battery short-circuit current density of the coated glass sample after covering dust contamination) / (Battery short-circuit current density of the initial coated glass sample after covering - Dust covering Battery short-circuit current density of the coated glass sample after contamination) *100%

The performance test results of the comparative examples and examples are shown in Table 1 below:

Table 1 Comparison of the comprehensive results of contact angle, sliding angle, light transmittance and short-circuit current density of photovoltaic cells by coating films in the above-mentioned embodiments and comparative examples

Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Water contact angle/° 110.1 106.4 108.3 91.2 98.8 103.8 Oil contact angle/° 68.2 64.5 65.3 36.4 46.2 57.3 Organic solvent contact angle/° 28.9 26.4 25.7 8.3 15.3 12.2 Water sliding angle/° 18.6 22.2 21.6 66.5 43.5 36.4 Oil sliding angle/° 5.2 8.6 7.2 / 34.6 47.8 Organic solvent sliding angle/° 13.5 14.8 15.1 / / / Light transmittance-550 nm/% 93.0 92.3 92.7 91.3 82.7 84.6 Short circuit current density recovery rate/% 97.3 94.5 95.6 18.2 25.2 32.5

As shown in Table 1, compared with the comparative example, the nanofilm prepared by the method of the present disclosure integrates fully lyophobic, anti-reflective and self-cleaning properties, and the ultra-white glass coated with the nanofilm of the present disclosure is used as a photovoltaic cell panel. It can achieve efficient self-cleaning, and the short-circuit current density recovery rate can reach more than 94.5%.

As shown in Table 1, Comparative Example 3 is directly prepared using a single catalyst and modified by fluorination to obtain a silica sol. Although it can improve the liquid contact angle of the nano-coating film, it is difficult to improve the sliding angle and reinforcement of the nano-coating film. Anti-reflective properties. The reason is: the silica obtained by using alkali catalysis alone is spherical particles. At this time, the liquid repellency of the coating film depends on the roughness. Only when the roughness increases significantly, the contact angle of the coating film increases, but at the same time it slides The horns are also enlarged. In addition, the silica obtained by single base catalysis has a low refractive index and poor anti-reflective properties. Although silica with a higher refractive index can be obtained by single acid catalysis, it requires a long aging time and a long production cycle. In Example 1-3, the spherical silica obtained by alkali catalysis is used as the core, and the silica outer shell is further coated by acid catalysis. Combining the advantages of the two catalytic methods, clustered silica nanoparticles and free silica particles are obtained. The latter can fill in the pores of the clusters formed by the former, reducing the roughness of the nano-coating film and reducing the damage of the coating film. Dependence of lyophobicity on roughness. In addition, the multiple refraction/reflection of incident light inside the coating film is increased, further enhancing the anti-reflective performance of the nano-coating film.

As shown in Table 1, in Comparative Example 2, when a reactive silicone modifier is directly introduced into the reaction system of fluorocarbon polymer and isocyanate cross-linking agent for cross-linking reaction, the silicone modifier with low surface energy will The system has poor compatibility and is prone to macroscopic phase separation, resulting in a significant decrease in light transmittance. Therefore, although silicone modifiers can impart certain fully lyophobic and self-cleaning properties to nanocoatings, they cannot meet the high transmittance requirements of optical equipment. In Examples 1-3, the silicone modifier and excess isocyanate cross-linking agent are grafted in advance to modify the isocyanate cross-linking agent, thereby improving system compatibility and eliminating macroscopic phase separation. In addition, the reasonable and effective distribution of silicone segments and nanoparticles in the resin system is beneficial to the refractive index matching between the resin and nanoparticles, and jointly improves the light transmittance of the nanofilm.

Figure 1 is the water contact angle result of the nanofilm of Comparative Example 2; Figure 2 is the light transmittance result of the nanofilm of Comparative Example 2; Figures 1 and 2 show that adding silicone directly to fluorocarbon polymer and isocyanate can To a certain extent, the liquid repellency of the nanomembrane is improved, but due to the macroscopic phase separation of the organic silicon chain segments, it has a significant adverse impact on the light transmittance of the coating film, and the nanomembrane cannot achieve dynamic slip against organic solvents;

Figure 3 is the water contact angle result of the nanomembrane of Comparative Example 3; Figure 4 is the light transmittance result of the nanomembrane of Comparative Example 3; Figures 3 and 4 show the low-density fluorine modification directly introduced into the fluorocarbon polymer. Surface energy silica particles can improve the liquid repellency of nanofilms to a certain extent, but due to the agglomeration of the particles, the light transmittance decreases and the nanofilms cannot be given anti-reflective properties, and the nanofilms cannot achieve dynamic slip against organic solvents. shift;

Figure 5 is a TEM image of the clustered nanosilica particles in Example 1; Figure 5 shows that the nanosilica has a core-shell structure, and the shell has a villi-like structure, interconnected and stacked into clusters. The unique core-shell and The cluster structure is conducive to multiple refraction and reflection of light inside the nanofilm;

Figure 6 is the water contact angle result on the surface of the nanomembrane in Example 1; Figure 7 is the light transmittance result of the nanomembrane in Example 1; Figures 6 and 7 show that the combination of core-shell cluster nanosilica particles and The advantages of both silicone and fluoropolymers are that the obtained nanomembrane cross-linked prepolymer has excellent fully lyophobic and anti-reflective properties after curing into a nanomembrane;

Figure 8 is the short-circuit current density of the battery die, and the results of the battery short-circuit circuit density-voltage curve after covering the photovoltaic cell with the nanofilm-coated ultra-white glass of Example 1, being contaminated, and being cleaned; Figure 8 shows that samples coated with nanofilm can increase the short-circuit current density of the battery. Even after being contaminated by dust, it can be easily self-cleaned with a small amount of water, and the short-circuit current density recovery rate after cleaning reaches 97.8%.

The above-described embodiments are only ways to express the present disclosure. The descriptions are relatively specific and detailed, but should not be construed as limiting the patent scope of the present disclosure. It should be noted that those of ordinary skill in the art can make several modifications, equivalent substitutions, improvements, etc. without departing from the concept of the present disclosure, and these all fall within the scope of the present disclosure. Therefore, the protection scope of the patent disclosed should be determined by the appended claims.

Claims (15)

1. The self-cleaning anti-reflection nano film is formed by coating and curing a nano film crosslinking prepolymer, and is characterized in that:

the nano-film crosslinking prepolymer is a crosslinking reactant of a silicon fluoropolymer and fluorine modified nano-silicon dioxide;

the silicon fluorine polymer is a mixture of fluorocarbon resin and organosilicon modified isocyanate crosslinking agent;

the fluorine modified nano silicon dioxide is cluster nano silicon dioxide which is synthesized by a sol-gel method through alkali and acid catalysis and is modified by in-situ fluorination and has a silicon dioxide spherical particle inner core;

the synthesis method of the fluorine modified nano silicon dioxide comprises the following steps:

synthesizing alkali-catalyzed silica sol by alkali catalysis by adopting the sol-gel method, and thermally treating the alkali-catalyzed silica sol to obtain concentrated silica sol; adding the concentrated silica sol and the fluorination modifier into a reaction solution for acid-catalyzed synthesis of the silica sol, and carrying out acid-catalyzed synthesis reaction to obtain the fluorine-modified nano-silica;

the fluorocarbon resin comprises a chlorotrifluoroethylene and alkyl vinyl ester copolymer resin, a tetrafluoroethylene and alkyl vinyl ether copolymer resin and a chlorotrifluoroethylene and alkyl vinyl ether copolymer resin;

the preparation method of the organosilicon modified isocyanate cross-linking agent comprises the following steps:

the method comprises the steps of (1) adding organosilicon which is equivalent to 0.5-20.0% of the total mass of fluorocarbon resin and isocyanate crosslinking agent into the isocyanate crosslinking agent, catalyst and solvent, wherein the dosage of the catalyst is 0.5-3.0% of the total solid mass; reacting at the constant temperature of 60-90 ℃ under the nitrogen atmosphere and in a stirring state for 1-12 h to obtain the organosilicon modified isocyanate crosslinking agent;

the organosilicon comprises reactive polydimethylsiloxane with hydroxyl or amino at a single end, double ends or side chains;

the isocyanate crosslinking agent is one or more of toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dimethylbiphenyl diisocyanate, polymethylene polyphenyl isocyanate, hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylylene diisocyanate, methylcyclohexyl isocyanate and cyclohexane dimethylene diisocyanate.

2. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the alkali catalyst for the alkali catalysis is at least one of ammonia water, sodium hydroxide and potassium hydroxide.

3. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the acid catalyst for acid catalysis is at least one of hydrochloric acid, sulfuric acid, nitric acid and acetic acid.

4. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the fluorination modifier is at least one of 1H, 1H, 2H, 2H-perfluoro octyl trimethoxysilane, 1H, 2H, 2H-perfluoro octyl triethoxysilane, 1H, 2H, 2H-perfluoro decyl trimethoxysilane and 1H, 1H, 2H, 2H-perfluoro decyl triethoxysilane.

5. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the particle size of the cluster nano silicon dioxide is 10-500 nm.

6. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the synthesis method of the concentrated silica sol comprises the following steps: base catalyst was added to the catalyst in the following 1: stirring and reacting the mixture of ethyl orthosilicate and absolute ethyl alcohol in a volume ratio of 10-50 at room temperature for 12-24 h to obtain alkali-catalyzed silica sol; and thermally treating the base-catalyzed silica sol to remove the absolute ethyl alcohol and the base catalyst to obtain the concentrated silica sol.

7. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the acid catalyzed synthesis method comprises the following steps: according to the ethyl silicate, the water and the acid catalyst are 6-10:1-4: and (3) after mixing according to the volume ratio of 1, adding the absolute ethyl alcohol dispersion liquid of the concentrated silica sol, stirring at room temperature for reaction for 12-24 h, adding a fluorinated modifier into the reaction liquid, wherein the volume of the fluorinated modifier is 1-10% of the total volume of the system, and removing the solvent from the reaction product through rotary evaporation, reduced pressure distillation and vacuum drying to obtain the clustered nano silica.

8. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the curing is 24-48 h at room temperature or 1-12 h at 50-120 ℃; the thickness of the coated film is 100-900 nm.

9. The method for preparing the self-cleaning anti-reflection nano film according to any one of claims 1 to 8, comprising:

obtaining fluorocarbon resin containing hydroxyl and carboxyl groups;

after adding organosilicon into a mixture containing isocyanate crosslinking agent, catalyst and solvent, the organosilicon modified isocyanate crosslinking agent is obtained as a reaction product in a nitrogen atmosphere under a stirring state;

according to the fluorocarbon resin: the mass ratio of the organosilicon modified isocyanate crosslinking agent is 3-10:1, mixing the two materials in proportion to obtain a silicon fluorine polymer;

and mixing the silicon fluoropolymer with fluorine modified nano silicon dioxide to obtain the nano film crosslinking prepolymer.

10. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the molecular weight of the organic silicon is Mn=500-20000 g/mol.

11. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the catalyst is at least one of dibutyl tin dilaurate and stannous isooctanoate.

12. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the solvent is at least one of acetone, butanone, ethylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol butyl ether, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether.

13. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

dispersing the fluorine modified nano silicon dioxide in a diluent to obtain a dispersion liquid with the solid content of 5-50%;

according to fluorocarbon resin: the organosilicon modified isocyanate crosslinking agent is 3-10:1, mixing the two materials in a mass ratio, and diluting the mixture with a diluent to obtain a silicon-fluorine polymer solution with a solid content of 20-50%;

and (3) dripping fluorine modified nano silicon dioxide dispersion into the silicon-fluorine polymer solution in a state of ultrasonic treatment for 10-30 min and stirring for 10-60 min, and performing a crosslinking reaction to obtain the nano film crosslinking prepolymer.

14. The method for preparing the self-cleaning anti-reflection nano film according to claim 13, wherein:

the mass ratio of the silicon fluorine polymer solution to the fluorine modified nano silicon dioxide dispersion liquid is 0.07-0.6:1.

15. the method for preparing the self-cleaning anti-reflection nano film according to claim 13, wherein:

the diluent is at least one of butyl acetate, propylene glycol methyl ether acetate and xylene.