Effect of molybdenum doping on the electrochromic properties of tungsten oxide thin films by RF magnetron sputtering

Thin films of pure and molybdenum (Mo)-doped tungsten trioxide (WO3) were deposited on indium tin oxide (ITO)-coated glass and Corning glass substrates by RF magnetron sputtering technique. The effect of Mo doping on the structural, morphological, optical and electrochromic properties of WO3 films was studied systematically. The energy dispersive X-ray analysis (EDAX) revealed that the films consist of molybdenum concentrations from 0 to 2 at.%. X-ray diffraction (XRD) studies indicated that with the increase of Mo concentration the structural phase transformation takes place from polycrystalline to amorphous phase. The crystallite size of the films decreased from 24 to 12 nm with increase of doping concentration of Mo in WO3. Scanning electron microscope (SEM) analysis revealed that Mo dopant led to significant changes in the surface morphology of the films. The electrochemical and electrochromic performance of the pure and Mo-doped WO3 were studied. The WO3 films formed with 1.3 at.% Mo dopant concentration exhibited high optical modulation of 44.3 % and coloration efficiency of 42.5 cm(2)/C.