NOVELTY - Making (M1) low-index silica based coating (3) involves forming silica precursor comprising radiation curable composition of radiation curable monomer and photoinitiator, and silica sol that comprises silane and/or colloidal silica; depositing the silica precursor on a substrate (1) to form coating layer; curing the coating layer using at least exposure to electromagnetic radiation; and after the curing, firing the coating layer in an oven at 550-700 degrees C for 1-10 minutes.    USE - For making low-index silica based coating useful in photovoltaic device (claimed), e.g. solar cells, such as in storefront windows, display cases, picture frames, greenhouse glass/windows, solariums, and other types of windows.    ADVANTAGE - The low-index silica based coating is an improved antireflective coating useful in photovoltaic device and other applications to reduce reflection off of glass or other substrates.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) photovoltaic device comprising either photoelectric transfer film and the low-index coating that is provided on a light incident side of a front glass substrate of the photovoltaic device; or photovoltaic film and at least a glass substrate on a light incident side of the photovoltaic film; and an antireflection coating provided on the glass substrate and comprises at least a layer provided on the glass substrate, where the layer comprises high index coating; and over the high index coating, a coating layer obtained by the method (M1); and    (2) making photovoltaic device including low-index silica based coating used in an antireflective coating, involving the method (M1); and using the glass substrate with the low-index silica based coating on it as a front glass substrate of the photovoltaic device so that the low-index silica based coating is provided on a light incident side of the glass substrate.    DESCRIPTION OF DRAWING(S) - The figure shows cross sectional view of photovoltaic device that uses the antireflective coating.    Glass (1)    Low index silica-based antireflective coating (3)    Thin film solar cell layer (5)    Reflection enhancement oxide and/or ethylene vinyl acetate film (6)    Back metallic contact (7)