Optical and electrochromic properties of sol-gel made CeO2TiO2 thin films

The optical and electrochromic properties of sol-gel dip coated equimolar CeO2-TiO2 thin films were investigated. The coating solutions were prepared by using mixed organic and inorganic (Ti[O(CH2)(3)CH3](4) and (NH4)(2)Ce(NO3)(6)) precursors. The refractive index, absorption coefficient and packing densities of the films have been calculated with respect to the pulling rate and number of coating layers. The surface compositions of the films were studied by an X-ray photoelectron spectrometer (XPS). A scanning electron microscope was used for the analysis of surface structure. The optical band gaps have been found as E-g(d) = 3.59 +/- 0.12 eV and E-g(ind) = 3.19 +/- 0.08 eV for direct and indirect transitions, respectively. The results show independence of optical band gaps with dipping rate and number of layers. The dip coating process is also an important method for the preparation of thin films used in the held of electrochromism. The porous structure of dip coated CeO2-TiO2 films have the required properties for ion-storage counter electrodes. We studied the electrochromic properties of CeO2-TiO2 films by means of cyclic voltammetry. We report the results on the films capable of serving as transparent ion storage in smart windows. (C) 1999 Elsevier Science Ltd. All rights reserved.