Limitations of dual and complementary inorganic–organic electrochromic device for smart window application and its colorimetric analysis

Inorganic tungsten oxide (WO3) and organic polyaniline (PANI) films were used as the cathodic and anodic electrodes of an inorganic–organic electrochromic device (IOECD). WO3 was deposited by sputtering while PANI films were electrodeposited on transparent Indium doped Tin Oxide (ITO) glass substrates, respectively. Optical and electrochemical studies were performed to find the optical attenuation, coloration efficiencies, reversibility and response time separately for the individual films as well as for the assembled IOECD. The change in transmittance of WO3 film was found to be 63.92%. PANI film showed an optical attenuation of 50.69% while the transmission change through the IOECD was equal to 57%. Colorimetric analysis was done to define the colors in the bleached and colored states in terms of L*ab values and xy chromaticity diagram. Factors limiting the performance of an IOECD were analyzed. It was found that in a charge unbalanced dual complementary IOECD, the coloration efficiency is always less than that of one of the constituent electrodes.