Comparison of photoelectrochromic devices with different layer configurations

We prepared photoelectrochromic devices, which can be switched from transparent to dark, by adding an electrochromic layer (WO3) to a dye-sensitized solar cell. Layers in different orders are compared: first, the TiO2 layer situated above the WO3 layer; second, the WO3 layer situated above the TiO2 layer; and third, the TiO2 and WO3 layers situated on opposite electrodes, leaving out the Pt layer. For the first and second configuration, fast and intense coloring is possible together with fast bleaching, which is in principle not possible for the third. The comparison of the first and the second configurations demonstrated that it is possible to exchange the positions of the TiO2 and WO3 layers. The layers were prepared by dipping the samples in sols and we found that material of the second layer penetrates the first layer, which influences the kinetics of the coloring and bleaching. For the first configuration, we showed that it is possible to switch the transmittance not only from the illuminated to the nonilluminated state, but also during continuous illumination. For the first configuration and under 1 sun of illumination, the visual transmittance changed from 51 to 4.8%. Switching times are about 3 min for coloring and bleaching. (C) 2002 The Electrochemical Society.