Antireflection Coarting of γ-Alumina with Gradient-Refractive Index Structure
Abstract
Light receiving elements including solar cells generally have laminated structure. Inevitable reflection takes place at the interface where the refractive index changes abruptly. Therefore, in such devices as solar cells, suppression of the optical loss is one of the necessary factors for improving power generation efficiency. In our previous investigation, Ishiguro et al., (2009) found that metallic aluminum film can be changed to transparent boehmite film by hydrothermal (HT-) treatment in ultrapure water. Transmittance of HT-treated film was higher than that of glass substrate itself. One of the reasons was thought to be suppression of reflection due to the gradient-refractive index structure. However, HT-treated film (boehmite film) is poor chemical stability and mechanical strength. In this study, boehmite films were heat-treated in the air in order to stabilize and keep the gradient-refractive index structure at the same time.