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⁻/I₃⁻), 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 30×30 cm² sample with conductor paths reduces the transmittance by a factor of 10 in 8 s.