A method of making an antiglare coating using a mullite sol, possibly for use in a plasma display device, a photovoltaic device, or the like. The method may include the following steps in certain example embodiments: forming a mullite sol by mixing glycycloxypropyltrimethoxysilane (or other suitable silane) with an aluminum chloride (or other suitable aluminum-containing compound), and one or more of a solvent and water; casting the mixture by spin coating to form a layer on a substrate (e.g., a glass substrate); and curing and/or heat treating the layer. This layer may make up all or only part of an antiglare coating.