Electrochromism in sputter deposited nickel-containing tungsten oxide films

Thin films of NixW1−x oxide were prepared by reactive DC magnetron co-sputtering and were investigated by optical and electrochemical measurements. Electrochromism was found only for 0<x<0.3 but not for 0.3<x<0.6, though films with x∼0.4 could still sustain reversible charge insertion. The coloration efficiency was largest for 0.10<x<0.15. The charge capacity of the NixW1−x oxide films decreased upon increasing the value of x as a consequence of a decreasing ion diffusion coefficient leading to slower kinetics.