Hello, I tried to figure out that how smart window works and I had read several papers and web-pages. I did understand how colour centres in WO3 thin film works which is described at page 820 of the paper of Deb, S. K. Recent papers, related to electrochromic window, are using electrolytes for ion transferring from ion storage layer to electrochromic layer (WO3 film). I don't know why they use electrolyte for transferring electrons (ions). Was it possible to remove electrolyte and apply proper electric field between anode and cathode with WO3 film with short distance? I might miss something about changing band-gap with electric field. References are below : - https://en.wikipedia.org/wiki/Electrochromism - Deb, S. K. Philos. Mag. 1973, 27 (4), 801−822.