Variable transmittance coatings using electrochromic lithium chromate and amorphous WO3 thin films

A thin film, Li+ counterion, variable transmittance electrochromic device is described with the structure: glass\TO\LizLiyCrO2+x\Li2O-B2O3\WO3\ITO. The structure is prepared by sequential deposition of the layers using a combination of sputtering and evaporation processes. The LizLiyCrO2+x ''counterelectrode'' has a Li capacity of similar to 0.5 mC/cm(2) nm and exhibits weak anodic coloration with a luminous efficiency of 3 to 4 cm(2)/C. Variable transmittance devices, with an area of 20 cm(2), have been fabricated using 40 to 80 nm thick LizLiyCrO2+x films and cathodically coloring a-LixWO3. 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.