Electrochromic characteristics of fibrous reticulated WO 3 thin films prepared by pulsed spray pyrolysis technique

Abstract

The electrochromic (EC) behavior of fibrous reticulated WO 3 films prepared from ammonium tungstate precursor by pulsed spray pyrolysis method was investigated. All the films were prepared using identical technological parameters and a thorough investigation of the electrochromic properties of the films deposited at 300 °C is reported. The structural properties were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochromic and optical properties were measured using cyclic voltammetry and ultraviolet (UV)-visible spectrophotometry. The films are amorphous and have a fibrous reticulate-like morphology having micron-size circular rings. The films show high transparency in the visible range and the optical band gap energy is about 3.1 eV. Electrical measurements show that the resistivity monotonically decreases as temperature increases, which indicates thermal hopping transport. The activation energy for hopping transport is of the order 4×10 −4 eV. The electrochromic coloration efficiency (CE) is found to be 34 cm 2/C at 630 nm.