Electrochromic performance of sol-gel deposited CeO2 films

Ceria ( CeO2 ) films were prepared by a sol-gel technique onto fluorine doped tin oxide (FTO) coated glass substrates. The coating solution was derived from cerium amonium nitrate dissolved in ethanol with diethanolamine (DEA) used as a complexing agent. Lithium intercallating properties of the films were investigated using cyclic voltammetry (CV) and UV-visible (UV-Vis) spectroscopy. The electrochemical examinations were performed in a 0.5 M LiClO4 propylene carbonate (PC) electrolyte. The additional film characterizations were performed by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). XRD of the films showed that they had an cerianite structure for heat treatment temperatures at or above 450 degrees C. The SEM examinations showed that the surface texture was uniform and homogeneous. CV examinations showed a reversible electrochemical insertion or extraction of Li+/e(-) ions maintaining a high optical transmissivity. Spectroelectrochemistry showed that these films can be used as optically passive counter-electrode in transmissive electrochromic devices.