RF Sputtered <TEX>$SnO_2$</TEX>, Sn-Doped <TEX>$In_2O_3$</TEX> and Ce-Doped <TEX>$TiO_2$</TEX> Films as Transparent Counter Electrodes for Electrochromic Window

The <TEX>$SnO_2$</TEX>, Sn-doped <TEX>$In_2O+3; and ;Ce-doped; TiO_2$</TEX> films have been prepared by RF sputtering method, and their opto-electrochemical properties were investigated in view of the applicability as counter electrodes in the electrochromic window system. These oxide films could reversibly intercalate <TEX>$Li^+$</TEX> ions owing to the nanocrystalline texture, but remained colorless and transparent. The high transmittance of the lithiated films could be attributed to the prevalence of the <TEX>$Sn^{4+}/Sn^{2+}; and; Ce^{4+}/Ce^{3+}$</TEX> redox couples having 5s and 6s character conduction bands, respectively. For the Ce-doped <TEX>$TiO_2$</TEX> film, <TEX>$(TiO_2)_{1-x}(CeO_2)_x$</TEX>, an optimized electrochemical reversibility was found in the film with the composition of x = 0.1.