Solid Polyorganodisulfide Electrodes as Ion Storage Layers for Electrochromic Devices

We report on the fabrication and use of new ion storage layers as counter electrodes for completely solid state electrochromic windows. The ion storage layers are transparent composites of a room temperature ion-conducting polymer and an electroactive material based upon the polyorganodisulfide/dithiolate redox couple. Solid state devices consisting of molybdenum doped WO₃, a polymer ion conductor layer and the new ion storage layers colored rapidly from a pale yellow to a deep blue-green, upon application of 1.2 V d.c. The photopic transmittance changed from 61 to 9%, and the solar transmittance from 45 to 5% during the coloration process, for a typical sample. Because the counter electrode does not change optical properties as a function of redox state, problems with color imbalance can be avoided completely. The large number of polyorganodisulfides that may be used for this application allows for flexibility in device design and properties, and the use of solid state components ensures improved stability of windows incorporating this technology.