Electrochromic device with a redox electrolyte

Electrochromic glazing allows the solar energy gain and daylighting in buildings and cars to be controlled. Here we report new results about a special type of electrochromic device. It consists of an electrochromic layer (WO3) on a transparent electrode, an electrolyte containing Li+ cations and a redox system (I-/I-3(-)), and a catalyst (Pt) on a second transparent electrode. The electrolyte is based on gelled ionic liquids. The change in the transmittance is extremely high: the visible (solar) transmittance can be switched between 63% (46%) and 1.2% (0.7%). A segmented 30 x 30 cm(2) sample with conductor paths reduces the transmittance by a factor of 10 in 8 s.