New photoelectrochromic device

A new photoelectrochromic device with excellent coloring and bleaching char acteristics was developed. In contrast to other photoelectrochromic devices , the electrochromic layer (e.g. WO3) and the photoactive layer (e.g, dye-c overed TiO2) are situated on the same TCO-coated glass substrate (TCO: tran sparent conductive oxide). The opposing electrode is a platinized TCO-coate d glass. The electrolyte contains Li+ and a redox couple (I- and I-3(-)) in an organic solvent (e.g. propylene carbonate). Under illumination, the ele ctrochromic layer is colored, and in the dark it is bleached. The advantage of this new device is that a catalyst (Pt) can accelerate the bleaching pr ocess independently of the coloration process. Thus a deep and fast colorat ion, and fast bleaching, can be achieved in the same device. The coloration is fast even for large areas, because the TCO is not necessary for the col oration process. Under I sun of illumination, we measured a transmittance c hange from 64 to 23% in 2 min. The bleaching time is about 2 min. (C) 2001 Elsevier Science Ltd. All rights reserved.