Thermal Annealing Effects of V2O5 Thin Film as an Ionic Storage Layer for Electrochromic Application

A vanadium pentoxide (V₂O₅) thin film with thermal annealing as an ionic storage layer for electrochromic devices is presented in our study. The V₂O₅ 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 V₂O₅ 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 V₂O₅ thin film. We obtained a charge capacity of 97.9 mC/cm² with a transparent difference ΔT value of 31% and coloration efficiency of 6.3 cm²/C after 400 °C thermal annealing. The improvement was due to the polycrystalline orthorhombic structure formation of V₂O₅ film by the rearrangement of atoms from thermal energy. Its laminate structure facilitates Li⁺ ion intercalation and increases charge capacity and transparent difference.

Electrochromic Properties of the Vanadium Pentoxide Doped with Nickel as an Ionic Storage Layer

The electrochromic property of nickel doped vanadium pentoxide (V2O5) deposited by a co-sputtering system is investigated. The structural analysis of the thin film was done by an X-ray diffraction (XRD) analyzer. The surface morphology of the film was studied by a field emission scanning electron microscopy (FE-SEM). The composition of the film was detected by an Auger analysis. The electrochromic properties of the device were measured by cyclic voltammetry. For the undoped V2O5 thin film, the charge storage capacity increases with the thickness and is 42.58 mC/cm2 at the thickness of 192.4 nm after 2 h deposition. For the Ni-doped V2O5, the Ni-V-O film shows V2O5 structural dominate with cathode coloration in the lower Ni deposition power region and the charge storage capacity decreases with the increases of the power, while the Ni-V-O film transfers to NiO structural dominate with anodic coloration at the realm of higher Ni doping. The charge storage capacity increases with the increase of Ni doping. It can reach to 101.35 mC/cm2. The Ni-V-O electrochromic film shows improvement of transmittance difference between colored and bleached values and improvement of charge store capacity as it is compared to pure V2O5 films.