Electrochromic behavior of Mo/W oxides related to their surface morphology and intercalation process parameters

The investigation presented in this paper is related to the electrochromic (EC) behavior of sputtered and CVD deposited films of WO3 and W/Mo based mixed oxide films. The electrochromic effect is a reversible change in the film transmittance under a small voltage applied across the film. Optimization of the films performance as functional layers in EC cell (three electrode electrochemical cell arrangement) is studied through changing the electrolyte (type of ions) and the ions concentrations. The study is supported by results from the films structure in its dependence on deposition process parameters. The change in films microstructure and morphology, as well as bonds and their configuration is investigated by Raman and Fourier transform infrared (FTIR) spectroscopy, respectively, and by scanning electron microscopy (SEM). The electrochromic properties, as presented by color efficiency (CE) and optical modulation (ΔT) of optimized CVD films are compared with the ones of sputtered WO3 films. Sputtered WO3 films show high color efficiency exceeding 113.7 cm2/C and high value of optical modulation reaching 87% at 600 nm. Corresponding values for APCVD deposited tungsten oxide films are 111 cm2/C and 55% at 650 nm.