A method of preparing an electrochromic device involves forming multiple layers of selected materials on a substrate in a vacuum processing chamber. A first of these layers is an electrode layer deposited directly on the substrate and used for making contact to a subsequently deposited precursor film, preferably tungsten oxide, from which an electrochromic layer is formed by lithium loading in the presence of ionized nitrogen. This not only forms the electrochromic layer by diffusion of the lithium into the tungsten oxide, but also forms a thin lithium nitride ion transfer layer on the then exposed surface. Subsequently, a lithium fluoro-nitride electrolyte layer is formed on the ion transfer layer by evaporation from a lithium fluoride source in the presence of ionized nitrogen. An ion storage layer, which may be a vanadium oxide and a transparent second electrode layer are subsequently vacuum deposited.