Preparation and Durability of SiO2 Antireflection Thin Film by Sol-gel Method

Solar energy is an important sustainable and clean energy source. However, the reflection of light by the cover glass leads to the reduction of the efficient utilization for the incident solar energy. In order to reduce light reflection on cover glass, SiO2 antireflection thin films were prepared on glass by sol-gel dip-coating method. A series of SiO2 sols were prepared with ethyl orthosilicate (TEOS) as raw material, ethanol as solvent, and ammonia as catalyst. The structure of SiO2 was characterized by X-ray diffraction. The surface morphology of SiO2 thin films were observed by scanning electron microscopy. The optical properties and wettability were measured with ultraviolet-visible-near infrared spectrophotometer and contact angle tester. The effect of SiO2 sol and dip-coating withdraw speed on the optical properties of SiO2 thin films was investigated. The results showed that SiO2 prepared by alkaline sol was amorphous phase. The different precursor sol had no significant effect on the crystal structure. The SiO2 thin films prepared on glass by sol-gel dip-coating method had loose structure and micro cracks. The optical properties of SiO2 thin films could be controlled by Sol-gel dip-coating process. When the ratio of TEOS to ethanol was 1∶20 and the dip-coating withdraw speed was 500 μm/s (SiO2-2-500) or the ratio of TEOS to ethanol was 1∶30 and the dip-coating withdraw speed was 1 000 μm/s (SiO2-3-1000), the SiO2 films had excellent antireflection performance. The maximum transmittance and average transmittance of glass coated SiO2-2-500 film was 98.38% and 93.19% in the wavelength range of 400-1 100 nm, which was 6.57% and 5.01% higher than those of bare glass. While, the maximum transmittance and average transmittance of glass coated SiO2-3-1000 film was 98.75% and 93.52% in the wavelength range of 400-1 100 nm, which was 6.94% and 5.34% higher than those of bare glass. The refractive index of SiO2-2-500 and SiO2-3-1000 film was 1.35 and 1.33. The thickness of SiO2-2-500 and SiO2-3-1000 film was 101.11 nm and 102.63 nm. The excellent antireflection performance of SiO2-2-500 and SiO2-3-1000 films might be related to the low refractive index and appropriate film thickness. The water contact angle of SiO2 thin films was about 5o, showing excellent superhydrophilic performance. To evaluate the durability of the antireflection films, the glasses without and with SiO2 antireflection film were exposed in the laboratory for 5 months and their transmission spectra were tested. The maximum transmittance and average transmittance of glass coated SiO2-2-500 film was 97.36% and 92.47% in the range of 400-1 100 nm wavelength after 5 months, which was 7.50% and 5.94% higher than those of bare glass. Meanwhile, the maximum transmission and average transmission of glass coated SiO2-3-1000 film was 96.57% and 92.12% in the range of 400-1 100 nm wavelength after 5 months, which was 6.71% and 5.59% higher than those of bare glass. The glass coated SiO2-2-500 and SiO2-3-1000 films maintain high transmittance in long time. The durability of antireflection properties for SiO2 films is excellent in the experiment. These results indicate that SiO2 films prepared by Sol-gel method have excellent antireflection, superhydrophilic and good durability properties and have potential application value in solar cell cover glass. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.