Facile synthesis of silica composite films with good mechanical property for spectrally broadband antireflection coatings

Recently, antireflection films have been widely used in the glass cover of solar cells because it can improve the solar transmittance obviously and are usually prepared by a facile sol-gel method and subsequent annealing process. However, the annealing process is complicated, leading to a large preparation cost. In order to solve the problem, a facile one-step annealing method under ammonia mixed atmosphere was developed to prepare the silica composite films with good mechanical property for antireflection coatings. The obtained silica composite film exhibited enhanced hardness of H and good solar transmittance increase of 3.74% in the wavelength range from 380 nm to 1100 nm compared with bare glass substrate. This is mainly because that the ethoxy in the films can be further hydrolyzed to hydroxyl in mixed ammonia gas atmosphere to intensify self-condensation reaction of hydroxyl in the film, leading to a reduced distance between particles for enhanced hardness and a decrease in the film thickness to increase solar transmittance. The increase of chemical connection between particles can improve the mechanical property of the film obviously. Therefore, this work can provide a facile way to simultaneously improve the mechanical performance and the visible transmittance of the antireflection film.