Thermal Annealing Effects of V(2)O(5) Thin Film as an Ionic Storage Layer for Electrochromic Application

A vanadium pentoxide (V(2)O(5)) thin film with thermal annealing as an ionic storage layer for electrochromic devices is presented in our study. The V(2)O(5) thin film was deposited on an ITO glass substrate by an RF magnetron sputtering. The electrochromic properties of the film were evaluated after various thermal annealing temperatures. The structural analysis of the film was observed by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), and atomic force microscopy (AFM). The structure of the V(2)O(5) thin film transformed from an amorphous to polycrystalline structure with directions of (110) and (020) after 400 °C thermal annealing. The electrochromic properties of the film improved compared with the unannealed V(2)O(5) thin film. We obtained a charge capacity of 97.9 mC/cm(2) with a transparent difference ΔT value of 31% and coloration efficiency of 6.3 cm(2)/C after 400 °C thermal annealing. The improvement was due to the polycrystalline orthorhombic structure formation of V(2)O(5) film by the rearrangement of atoms from thermal energy. Its laminate structure facilitates Li(+) ion intercalation and increases charge capacity and transparent difference.