Chemical bath deposition and characterization of electrochromic thin films of sodium vanadium bronzes

Thin yellow-orange films of sodium vanadium oxide bronzes have been prepared from a sodium-vanadium solution (1:1) at 75 degrees C and pH = 3. The composition, structure and morphology of the films have been studied by XRD, IR spectroscopy, TG and SEM-EDX analyses. It has been established that the prepared films are a phase mixture of hydrated NaV6O15 (predominant component) and Na1.1V3O7.9 with total water content of 10.58%. The sodium vanadium bronze thin films exhibit two-step electrochromism followed by color change from yellow-orange to green, and then from green to blue. The cyclic voltammetry measurements on the as-deposited and annealed vanadium bronze films reveal the existence of different oxidation/reduction vanadium sites which make these films suitable for electrochromic devices. The annealing of the films at 400 degrees C changes the composition, optical and electrochemical properties (C) 2011 Elsevier Ltd. All rights reserved.