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 (WO 3 ) to a dye-sensitized solar cell. Layers in different orders are compared: fast, the TiO 2 layer situated above the WO 3 layer; second, the WO 3 layer situated above the TiO 2 layer; and third, the TiO 2 and WO 3 layers situated on opposite electrodes, leaving out the Pt layer. For the first and second configuration, fast and intense coloring is possible together with first 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 TiO 2 and WO 3 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. hut also during continuous illumination. For the first configuration and under I sun of illumination, the visual transmittance changed froom 51 to 4.8%. Switching times are about 3 min for coloring and bleaching.