Variable Transmittance Coatings Using Electrochromic Lithium Chromate and Amorphous WO 3 Thin Films

Abstract

A thin film, counterion, variable transmittance electrochromic device is described with the structure: . The structure is prepared by sequential deposition of the layers using a combination of sputtering and evaporation processes. The "counterelectrode" has a Li capacity of ∼0.5 mC/cm2 nm and exhibits weak anodic coloration with a luminous efficiency of 3 to 4 cm2/C. Variable transmittance devices, with an area of 20 cm2, have been fabricated using 40 to 80 nm thick films and cathodically coloring a‐. The luminous transmittance range and switching speed of as‐fabricated devices are typically 10 to 70% and 30 s, respectively. Multicycle switching reveals a decrease in switching speed over the first 5000 cycles while the luminous transmittance range is unchanged.