A new structure photoelectrochromic device (PECD) with excellent coloring and bleaching characteristics was developed. In contrast to other photoelectrochromic devices (PECDs), the electrochromic layer (e.g. PEDOT-MeOH) and the photoactive layer (e.g. dye-covered TiO2) are situated on the same FTO glass substrate. The opposing ITO electrode is electropolymerized with highly transparent electrocatalyst material. The electrolyte contains Li+ and a redox couple (I- and I3-) in an organic solvent (e.g. propylene carbonate). Under illumination, the electrochromic layer is colored directly by the injection of electrons from dye molecules, and it is bleached by triiodide in electrolyte under dark surroundings. The advantage of this new structure PECD is that the short electron transfer path can accelerate the coloring process. As for bleaching process, highly transparent PEDOT-MeOH on counter electrode can act as electrocatalyst material to accelerate bleaching process in short circuit. In comparison with the PECD which electrochromic layer and photoactive layer are separated, the c and b shows 5.5 s and 3.3 s, extremely faster than the separated type PECD (S-PECD) which c and b shows 33.1 s and 18.1 s. Therefore, H-PECD would show a rather high PhCE(~160 W-1 min-1 cm2) at initial time so that H-PECD could get same optical contrast without consuming much energy. What’s more, when the new PECD coloring under illumination in short circuit, it could show a 3% optical contrast more than illumination in open circuit. As a result, the new structure PECD could realize a little complementary in optical contrast through the coloring and bleaching in bifunctional counter electrode.
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