Self-Cleaning and Antireflective Films for All-Glass Evacuated Tube Solar Collectors

SiO2 antireflective nanoporous films were prepared by sol-gel process, combined with dip coating technology. The highest values of solar transmittance (96% in the broader spectrum range of 250 nm-2500 nm) are obtained. The static contact angle values increase after the treatment with 100% ethylchlorosilane and hexamethyldisilazane solutions. The antireflective films has to display long term stability as the operation conditions in solar collectors include low temperatures, high temperatures, and humid environment, all of which can degrade its optical properties.