Electrochromic windows based on V2O5–TiO2 and poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) coatings

The electrochromic window (ECW) based on poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine), PProDOT-Me2, and V2O5–TiO2 coatings was fabricated for modulating optical transmittance. It exhibited the high contrast of optical transmittance change (ΔT %) to 68% at 580 nm, rapid color-switching time, electrochemically cyclic stability and optical memory. Also, the large-sized ECW of 305×508 mm2 was successfully fabricated. The Li+ insertion/extraction process of PProDOT-Me2 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 (25×25 mm2). The optical memory was the great advantage of the ECW.

► This paper analyses optical and electrochemical properties of electrochromic windows.
► The long-term electrochemical stability of the device is demonstrated.
► The optical memory of the device is investigated