Facile synthesis of V2O5 films and devices exhibiting multicolor electrochromic properties

V2O5 films were facilely fabricated on indium tin oxide glasses by spin coating vanadyl oxalate precursor sols and subsequent calcination. The as-prepared V2O5 films and devices exhibit multicolor electrochromic performances: yellow, green and blue. Calcination temperature, precursor concentration and applied power were found to largely affect the electrochromic properties of the V2O5 films. The calcination temperature is key factor for the successful preparation of vanadium oxide films with electrochromic properties. V2O5 film could be synthesized by calcining above 300 ℃ for 1 h. With the increase of temperature, the morphology of the film changes from flat plane to wrinkle and crack to rice-like nanoparticles and to nanoplate. The transmittance modulation in the near-infrared region is relatively high, and the maximum light modulation can reach to 48.3%. Cyclic voltammetry tests indicate that the as-prepared V2O5 films have high cycling stability. After 1000 cycles, the V2O5 films prepared at 400 ℃ still have excellent electrochromic properties. The coloration efficiency value is ca. 29.6 cm2/C at a wavelength of 890 nm and the exact coloring/bleaching times of the V2O5 device are 12 s/18 s, respectively. The study provided a simple and low-cost method to fabricate V2O5 films and their devices.