Preparation method of high-performance mesoporous antireflection nanofilm

Abstract

The application discloses a high-performance mesoporous antireflection nanometer film preparation method and belongs to the technical field of optical film preparation. The method adopts a sol-gel process and comprises sol preparation, film coating, drying and heat treatment. First, silicate, siloxane and water are co-hydrolyzed in an organic solvent under acidic conditions in a certain proportion, and a sol is obtained after refluxing. Then, an organic pore-forming agent, polyethylene glycol monomethyl ether, is added and fully dissolved. The sol is coated on a transparent substrate, dried and then heat-treated to obtain the high-performance mesoporous antireflection nanometer film. The film is composed of SiO2 nanoparticles, the nanoparticles are matched with each other to form holes or pores, the porosity gradually increases from the substrate to the surface, the film is attached to the surface of photovoltaic glass, the transmittance of the glass in the range of 380-1100 nm is improved by 4-6 percent points, the pencil hardness (GB / T1727-92) is higher than 9H, and the adhesion reaches more than 0 level (GB / T 1727-1992).

Description

Technical Field

[0001] This invention belongs to the field of optical thin film material preparation technology, specifically relating to a method for preparing high-performance mesoporous antireflection SiO2 nanofilms. Background Technology

[0002] Antireflective coatings are widely used as cover plates on solar cells to reduce sunlight reflection loss and improve photoelectric conversion efficiency. Based on optical characteristics, antireflective coatings can be classified into single-layer and multi-layer films. Single-layer antireflective films do not require complex thin-film design, but the antireflection effect of a dense single-layer antireflective film is not ideal. Multi-layer antireflective films with optimized designs have a wider antireflection spectral band, but multi-layer antireflective films obviously increase the complexity of the manufacturing process and the production cost.

[0003] Traditional SiO2 antireflective films are typically prepared using the sol-gel method, which includes both alkali-catalyzed and acid-catalyzed methods. The alkali-catalyzed method generally offers advantages such as high transmittance and low cost. Patent application CN105399340A discloses a method for preparing antireflective films using trimethylchlorosilane-modified SiO2, synthesizing SiO2 sol under alkali catalysis to prepare the antireflective film. Similar technologies include authorized patent CN108761581B and patent applications CN110564187A, CN106477909A, and CN104230178A. However, this alkali-catalyzed SiO2 antireflective film is composed of loosely packed solid SiO2 nanoparticles with numerous open pores between them. Furthermore, the particle surface contains abundant hydroxyl groups. This polar porous structure readily adsorbs polar pollutants from the environment, leading to a decline in the optical performance of the antireflective film. In addition, the absorption of moisture from the air by the thin film will severely reduce the transmittance of the antireflective film, damage the structure of the antireflective film, and may further corrode the substrate, thereby significantly shortening the service life of the antireflective film.

[0004] Acid-catalyzed antireflective films are generally very dense, and monolayer acid-catalyzed antireflective films have a high refractive index, making their optical properties insufficient for use as antireflective films. SiO2 molecules prepared under acid catalysis are chain-like, and after being made into a thin film, the exposed polar hydroxyl groups on the molecules form silicon-oxygen bonds with the glass surface, exhibiting excellent adhesion. Furthermore, by controlling the composition and ratio of the catalyst, the film can possess strong hardness [Ye L, Zhang Y, Zhang X, et al. Solar Energy Materials and Solar Cells, 2013, (111) 160-164]. Similar results have also been reported in patent applications CN105776883A and CN102617045A. However, dense materials do not significantly reduce the refractive index, and the antireflective effect of acid-catalyzed SiO2 is not achieved as expected.

[0005] Mesoporous antireflective films are formed by creating ordered pores on the surface of acid-catalyzed thin films. This significantly reduces the refractive index of the film, giving the acid-catalyzed SiO2 thin films a better antireflective effect. One method for preparing mesoporous antireflective films is to introduce a surfactant template, induce pore formation through evaporation, and then remove the template agent through post-treatment (high-temperature calcination) to obtain an ordered mesoporous SiO2 thin film. This film has a low refractive index and also possesses good mechanical properties. Patent application 202010264897 discloses a method for preparing mesoporous SiO2 thin films, in which a pore-forming agent is dispersed in an acid-catalyzed sol, sealed and aged to obtain a mesoporous acid-catalyzed sol; the sol is then stretched into a film and heat-treated to obtain a mesoporous antireflective film. Ye et al. used tetraethyl orthosilicate (TEOS) as a precursor and hexadecyltrimethylammonium bromide (CTAB) as a template to prepare an antireflective film with a weighted average transmittance of up to 98.7% through evaporation-induced self-assembly. This film has excellent mechanical wear resistance [Ye L, Zhang S, Wang Q, et al. RSC Advances, 2014, 4(67): 35818]. Xu et al. used TEOS as a precursor and nonionic triblock copolymer surfactant (F127) as a template agent to successfully prepare a stain-resistant SiO2 mesoporous antireflective film with good optical properties on a quartz substrate [Sun J, Zhang Q, Ding R, et al. Physical Chemistry Chemical Physics, 2014, 16(31): 16684-16693].

[0006] In summary, the monolayer acid-catalyzed mesoporous antireflective film has a relatively simple structure and preparation process, and its refractive index can be changed by adjusting the porosity. Only by achieving high optical performance while also possessing high adhesion and high hardness can mesoporous films meet the requirements for continuous and efficient operation of solar cells in harsh outdoor environments. Summary of the Invention

[0007] The purpose of this invention is to address the contradiction between the mechanical and optical properties (transmittance) of SiO2 nanoparticle antireflective films by providing a method for preparing high-performance mesoporous antireflective films. The method is characterized by the preparation of the film using a sol-gel method, including sol preparation, film coating, drying, and heat treatment. Specifically, silicate ester, siloxane, and water are first co-hydrolyzed in an organic solvent under acidic conditions in a certain proportion, and the resulting sol is obtained after reflux. An organic porogen, polyethylene glycol monomethyl ether, is added to the sol and fully dissolved. The sol is then coated onto a transparent substrate, dried, and subsequently heat-treated to obtain the high-performance mesoporous antireflective nanofilm.

[0008] The specific technical solution adopted in this invention is as follows:

[0009] (1) The silicate ester, siloxane and water are fully hydrolyzed in an organic solvent under acidic conditions in a certain proportion. After reflux, an organic porogen is added and fully dissolved in the sol to obtain a sol colloid. The volume ratio of silicate ester to siloxane is 1:0.1 to 1:1, the volume ratio of silicate ester to water is 1:0.1 to 1:0.5, the volume ratio of silicate ester to organic solvent is 1:10 to 1:20, and the mass ratio of organic porogen to sol is 1:20 to 1:50.

[0010] (2) Using the sol colloid obtained in (1), the glass surface is uniformly coated by dip-coating method. After drying, a SiO2 film is obtained. The organic pore-forming agent is removed by calcination heat treatment in a muffle furnace to obtain a porous SiO2 film. The dip-coating speed of the dip-coating method is 500 μm / s, the drying temperature is 80℃, and the calcination temperature is 100℃~500℃.

[0011] Preferably, the organic porogen in step (1) is one or more of polyethylene glycol monomethyl ether (mPEG) 350, mPEG 750, mPEG 1000, mPEG 1900 or other molecular weights of mPEG.

[0012] Preferably, in step (1), the silicate ester is one or two of tetraethyl silicate and tetrabutyl silicate; the siloxane is one or more of methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, n-octyltriethoxysilane, ethyltriethoxysilane, octadecyltriethoxysilane, hexyltriethoxysilane, and propyltrimethoxysilane.

[0013] Preferably, the organic solvent in step (1) is one or more of ethanol, methanol, and propanol.

[0014] Preferably, the acid used to adjust the pH value in step (1) is one or more of hydrochloric acid, acetic acid and nitric acid.

[0015] Preferably, the water in step (1) is deionized water.

[0016] This invention effectively shortens the aging time of the sol.

[0017] The beneficial effects of this invention are as follows: This invention resolves the contradiction between the adhesion and transmittance of antireflective films, effectively improving the mechanical properties of the antireflective films and facilitating outdoor use. The film prepared by this invention is composed of SiO2 nanoparticles, which are interlocked to form pores and voids. From the substrate interface to the film surface, the porosity of the film gradually increases, forming a gradient. Furthermore, it is characterized by its adhesion to the surface of photovoltaic glass, increasing the transmittance of the glass at 380-1100nm by 4-6 percentage points, achieving a pencil hardness (GB / T1727-92) of 9H or higher, and an adhesion level of 0 (GB / T 1727-1992) or higher. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the SiO2 nanofilm in this invention, magnified 20,000 times. The film surface shows relatively large pores, and it can be seen that the pores are composed of small particles, with certain porosity between the particles.

[0019] Figure 2 This is a spectral comparison of the transmittance of ultra-clear glass coated with an anti-reflective film and ultra-clear glass without an anti-reflective film in this invention. It can be seen that the film has a good anti-reflection effect.

[0020] Figure 3 These are scanning electron microscope images of the SiO2 nano-antireflective film of this invention after being scratched with a cross-cut adhesion tester and then peeled off with 3M tape. It can be seen that after peeling with tape, there was no significant detachment at the edges of the scratches, and the adhesion reached level 0 (GB / T 9826—1998) or higher.

[0021] Figure 4 This is a scanning electron microscope image of the SiO2 nano-antireflective film of this invention after being marked with a pencil hardness test. The pencil used was 9H (GB / T 1727-1992), and it can be seen that the hardness reaches 9H or higher. Detailed Implementation

[0022] The present invention will be further illustrated below through specific implementation examples. These examples are descriptive and not limiting, and cannot limit the scope of protection of the present invention.

[0023] Example 1:

[0024] A friction-resistant antireflective nanofilm and its preparation method include the following steps: Tetraethyl orthosilicate, methyltriethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a volume ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A certain amount of mPEG is then added to the sol to obtain a solution for preparing an antireflective coating. This solution is coated onto a photovoltaic white glass sheet using an dip-coating method at a speed of 500 μm / min. After the film dries, it is heated at 400℃ for 1 hour to obtain the antireflective film.

[0025] Example 2:

[0026] A friction-resistant antireflective nanofilm and its preparation method include the following steps: Tetraethyl orthosilicate, dimethyldiethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a molar ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 3 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A measured amount of mPEG is then added to the solution to obtain a solution for preparing an antireflective coating. This solution is coated onto a photovoltaic white glass sheet using an dip-coating method at a speed of 400 μm / min. After the film material is dried, it is heated at 400℃ for 1 hour to obtain the antireflective film.

[0027] Example 3:

[0028] A friction-resistant antireflective nanofilm and its preparation method include the following steps: Tetraethyl orthosilicate, trimethylethoxysilane, and deionized water are co-hydrolyzed in anhydrous ethanol at a molar ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. This solution is then used to prepare the antireflective coating. The solution is coated onto a photovoltaic white glass substrate using a dip-coating method at a speed of 200 μm / min, and heated at 400℃ for 1 hour to obtain the antireflective film.

[0029] Example 4:

[0030] A friction-resistant antireflective nanofilm and its preparation method include the following steps: Parts of tetramethyl orthosilicate, n-octyltriethoxysilane, and deionized water are co-hydrolyzed in methanol at a molar ratio of 1:1:0.3 for 1 hour. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution, which is the solution used to prepare the antireflective coating. This solution is coated onto a photovoltaic white glass sheet using an dip-coating method at a speed of 750 μm / min, and heated at 400℃ for 1 hour to obtain the antireflective film.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-performance mesoporous antireflective nanofilms, the method employing a sol-gel process, including sol preparation, film coating, drying, and heat treatment, characterized in that... First, silicate ester, siloxane and water are co-hydrolyzed in an organic solvent under acidic conditions in a certain proportion, and after reflux, a sol is obtained; then, an organic porogen, polyethylene glycol monomethyl ether, is added to the sol and fully dissolved; finally, the sol is coated onto a transparent substrate, dried and then heat-treated to obtain a high-performance mesoporous antireflective nanofilm.

2. The method for preparing the high-performance mesoporous antireflective nanofilm according to claim 1, characterized in that: The silicate ester is one or two of tetraethyl or tetrabutyl silicate; the siloxane is one or more of methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, n-octyltriethoxysilane, ethyltriethoxysilane, octadecyltriethoxysilane, hexyltriethoxysilane, and propyltrimethoxysilane; the organic porogen polyethylene glycol monomethyl ether is one or more of polyethylene glycol monomethyl ether 350, polyethylene glycol monomethyl ether 750, polyethylene glycol monomethyl ether 1000, and polyethylene glycol monomethyl ether 1900; the organic solvent is one or more of ethanol, methanol, and propanol; and the acid used to adjust the pH value is one or more of hydrochloric acid, acetic acid, and nitric acid.

3. The method for preparing the high-performance mesoporous antireflective nanofilm according to claim 1, characterized in that... The volume ratio of the silicate ester to the organic solvent is 1:10 to 1:20, the volume ratio of the silicate ester to the siloxane is 1:0.1 to 1:1, the mass ratio of the polyethylene glycol monomethyl ether to the sol is 1:20 to 1:50, and the volume ratio of the silicate ester to water is 1:0.1 to 1:0.

5.

4. The method for preparing the high-performance mesoporous antireflective nanofilm according to claim 1, characterized in that: The reflow temperature is 50–95℃, and the reflow time is 1–2 hours; the film heat treatment temperature is 100℃–500℃.

5. The method for preparing the high-performance mesoporous antireflective nanofilm according to claim 1, characterized in that... The thin film prepared by this method is composed of SiO2 nanoparticles, which are arranged together to form pores and voids. From the substrate interface to the film surface, the porosity of the film gradually increases to form a gradient. When the transparent substrate is photovoltaic glass, the film increases the transmittance of the photovoltaic glass in the 380-1100nm range by 4-6 percentage points. The film has a pencil hardness (GB / T1727-92) of 9H or higher and an adhesion of 0 grade (GB / T 1727-1992) or higher.

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