High performance mesoporous tungsten oxide films were deposited by ultrasonic spray deposition using
templated sol–gel chemistry. The dynamics of both sol preparation and hydrolysis were investigated by
UV–vis spectroscopy. A stable sol was formed after 12 h, while optimum electrochromic performance
was obtained for 12 h of hydrolysis. Electrochromic performance is strongly correlated to the annealing
conditions, with optimized films displaying coloration efficiency 450 cm2
/C and switching times o10 s.
FTIR spectroscopy revealed that WO3 produced under optimized conditions were free of hydroxyl
and carbonate impurities. Performance scaled with the specific surface area and nanoscale morphology.
The WO3 films display good long term cycling durability up to 2500 cycles, which was attributed to the
high degree of film crystallinity