Electrochromic coloration of sputtered nickel oxide films by injection of anions (Br- ions)

Electrochromic (EC) coloration of nickel oxide films has been achieved by t he injection of anions (Br- ions). This was effected by the use of a polyme ric anion conductor. Nickel oxide films were prepared by rf-sputtering in a n Ar/O-2/H-2 atmosphere from a compressed-powder NiO target. In order to ac hieve reversible EC phenomena, as-deposited films required an aging process (i.e. several cycles of injection and extraction of charge carriers). Afte r aging, charges (Br- ions) were observed to remain in the films. The resid ual charge in the films was observed to increase with hydrogen content in t he sputtering atmosphere, however, coloring efficiency was observed to decr ease. It was proposed that the residual charge (Br- ions) was responsible f or deactivation of the EC color centers.