The electrochromic window (ECW) based on poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine), PProDOT-Me-2, and V2O5-TiO2 coatings was fabricated for modulating optical transmittance. It exhibited the high contrast of optical transmittance change (Delta T %) to 68% at 580 nm, rapid color-switching time, electrochemically cyclic stability and optical memory. Also, the large-sized ECW of 305 x 508 mm(2) was successfully fabricated. The Li insertion/extraction process of PProDOT-Me-2 and V2O5-TiO2 films was monitored by cyclic voltammetry and the diffusion coefficient was calculated. The optical transmittance changes of the ECW were observed by applying potential steps. It demonstrated long-term electrochromic and electrochemical stability after over 150,000 cyclic switches. It was found that the response time of the ECW was rapid. It was five seconds for coloration and four seconds for bleaching in the ECW (25 x 25 mm(2)). The optical memory was the great advantage of the ECW. (C) 2012 Elsevier B.V. All rights reserved.