Optical and electrochemical properties of sol-gel spin coated CeO(sub 2)-TiO(sub 2) films

摘要

There are numerous literature reports on the fabrication of CeO(sub 2)-TiO(sub 2) thin films for use in electrochromic applications. As such, CeO(sub 2)-TiO(sub 2) have attracted interest as transparent counter electrodes for smart windows. Here, the optical and electrochemical properties of sol-gel spin coated CeO(sub 2)-TiO(sub 2) (50% CeO(sub 2)) films were investigated for electrochromic applications. The coating solutions were prepared by using mixed organic-inorganic (Ti(OC(sub 2)H(sub 5))(sub 4) and Ce(NH(sub 4))(sub 2) (NO(sub 3))(sub 6)) precursors. X-ray diffraction studies showed the sol-gel spin-coated films were composed of an amorphous matrix of titanium oxide containing nanocrystallites of cerium oxide. The coating solar transmission value was T(sub s) = 0.8 (250 nm thick). The refractive index and the extinction coefficient were derived from transmittance measurements in the UV-VIS-NIR regions. These films had refractive index value of n = 2.18 and extinction coefficient value of k = 8 (times) 10(sup 4) at (lambda) = 550 m. Cyclic voltammetric measurements showed reversible electrochemical insertion of lithium ions in a CeO(sub 2)-TiO(sub 2)/LiClO(sub 4)-propylene carbonate electrochemical cell. During cycling the films maintain high optical transmittance. Spectrophotometric and electrochemical investigations performed on CeO(sub 2)-TiO(sub 2) films revealed that these films are suitable as an optically passive counter-electrode in lithium electrochromic devices.