Honey-Comb Structured WO 3 /TiO 2 Thin Films with Improved Electrochromic Properties

Abstract

© The Author(s) 2015. The electrochromic properties of 90:10 WO < inf > 3 /TiO < inf > 2 thin films produced by anodizing co-sputtered W/Ti films in a fluorinated ethylene glycol solution are investigated in relation to corresponding pure WO < inf > 3 films. SEM images revealed that the TiO < inf > 2 content resulted in a more open honey-comb structure that increased the charge accommodation ability by 250%. The superior charge storage property of the WO < inf > 3 /TiO < inf > 2 meant that it had a better light modulation range, with transmittance of > 1% at 800 nm in the colored state. The electrochromic kinetic processes associated with coloration and bleaching are also much faster in the presence of TiO < inf > 2, with data generated by electrochemical impedance spectroscopy revealing that this is due to a reduction in the resistance to the insertion of Li + ions. Materials characterization techniques revealed that the WO < inf > 3 /TiO < inf > 2 composite maintains the monoclinic structure of the WO < inf > 3 and that the Ti atoms are substituted into the WO < inf > 3 matrix, rather than forming discrete TiO < inf > 2 blocks.