A low-index silica coating may be made by forming silica sol comprising a silane and/or a colloidal silica. The silica precursor may be deposited on a substrate (e.g., glass substrate) to form a coating layer. The coating layer may then be cured and/or fired using temperature(s) of from about 550 to 700.degree. C. A surface treatment composition comprising an organic material comprising an alkyl chain or a fluoro-alkyl chain and at least one reactive functionality comprising silicon and/or phosphorous may be formed, deposited on the coating layer, then cured and/or fired to form an overcoat layer Preferably, the overcoat layer does not substantially affect the percent transmission or reflection of the low-index silica coating. The low-index silica based coating may be used as an antireflective (AR) film on a front glass substrate of a photovoltaic device (e.g., solar cell) or any other suitable application in certain example instances.