Nanoporöse SiO2-Antireflexschichten für solare Anwendungen

Solar energy generation gains in significance within the scope of a sustainable and environmentally oriented energy policy. An approach to efficiency increases of solar modules is to increase light transmission through the glass coverings by the use of anti reflection coatings. In the transmission of light through a grass screen because of the different refraction indexes at each boundary about 4% of the light is reflected. By bringing to bear an anti reflection coating with a refractive index of 1.23 on both sides of the glass an optimally stable reflection reduction is achieved over the entire spectral range of sunlight. Silica with a nano scale porosity of about 50% is a material that fulfills these conditions. A wet chemical coating process was developed for nano coatings about 130 nm thick with porous structures. The coating is applied by the sol/gel process. After applying a nano-particulate silica sol by immersion coating a thermal treatment hardens the glass. Th e so obtained anti reflection coating leads to an increase in energy transmission of about 6% and reduction of the angle dependence. With such an anti reflection covering glass the annual yield of a photovoltaic facility increases by 6% and the annual heat yield of a collector facility increases by 10%. The anti reflection glass has passed relevant stability tests and is used increasingly as standard glass for photovoltaic modules.