Effect of Templates on the Electrochromic Properties of Tungsten Oxide Thin Films

Abstract

The mesoporous tungsten oxide (WO3) films were derived from the peroxotungstic acid (PTA) sol with templates through sol-gel method. Polyethylene glycol (PEG) 400 and tri-block polymer P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H) were chosen as templates. The structural, morphological, optical and electrochromic properties of the WO3 thin films derived from different sols were studied. The composition and crystal phase of the films change at different annealing temperatures. The films derived from the sols containing templates have higher crystallization temperature than those without templates. And the morphologies are distinctly different from different sols. The addition of the templates can improve the electrochromic properties of the WO3 films, and those prepared from the 3% of P123 sol show the best electrochromic properties. The highest transmittance modulation is near 60%, and the largest ion inserted and deinserted diffusion coefficient can reach 5.706×10-12 cm2/s and 1.271×10-11 cm2/s, respectively.