Electrochromic properties of MnO2 thin films

Electrochromic tungsten oxyfluoride thin films were made by reactive magnetron sputtering of W in Ar+O 2 +CF 4 . A moderate CF 4 fraction led to deposition at enhanced rates and films with fairly neutral colour in their dark state. Transparent vanadium oxyfluoride films were made analogously; they were annealing posttreated in Ar+0 2 +CF 4 . By fluorination it was possible to avoid the short-wavelength absorption that otherwise limits the usefulness of V 2 0 5 in electrochromic smart windows. A transparent, adhesive, viscoelastic polymer electrolyte laminate was developed. It has good voltammetric cycling capability (106 times), good optical transmittance, and high conductivity, ranging from 10 -6 S/cm (-10°C) to 10 -3 S/cm (80°C).