Optoelectronic properties of CVD MoO3 and MoO3-Wo3 films and their applications in electrochromic cells

Thin Films Of MoO3 and mixed Mo/W oxides were obtained by atmospheric pressure CVD, implying pyrolytic decomposition of metal hexacarbonyls. The optical transmittance was measured for the films. When deposited on typical glass substrates, the films showed about 80% transmittance in the visible. Oil conductive glass, this value dropped to around 60%. The electrochromic properties of MoO3 and the mixed Mo/W oxide films were investigated by cyclic voltammetry, performed in a standard three-electrode arrangement. The cyclic change of current and transmittance as a function of the applied voltage for different wavelengths was measured. Over the voltage range studied, coloring appears in the cathodic EC film - MoO3, WO3 or mixed film, which at negative voltage suddenly colors to deep blue. Correspondingly, at that moment, there is a minimum in the transmittance curve. Going towards positive applied voltages, the EC film begins bleaching (for about 3 minutes) and the cell regains its initial transparency. With the help of a monochromator, the experimental set-up allowed to study the change in the colour efficiency, as a function of different wavelengths in the spectral range of 400-800 nm.