Growth, microstructure and electrochromic properties of activated reactive evaporated WO3 thin films on flexible substrates

The tungsten trioxide (WO3) thin films were deposited onto flexible ITO coated Kapton substrates using plasma assisted activated reactive evaporation technique. The film depositions were carried out at an optimized glow power and oxygen partial pressures of 8 W and 1 X 10(-3) Torr respectively. The WO3 thin films deposited at a substrate temperature of 473 K were found to be composed of uniformly distributed nano grains with a triclinic structure. These nano crystalline W03 thin films showed 73% optical transmittance in the visible region with an optical band gap of 3.34 eV. The film exhibited an optical 2 modulation of 53 % upon lithium insertion and estimated coloration efficiency at a wavelength 550 nm is about 45 cm(2)/C.