Tandem dye-sensitized solar cell-powered electrochromic devices for the photovoltaic-powered smart window

Tandem dye-sensitized solar cell (DSSC)-electrochromic (EC) devices were realized using two-faced transparent conducting oxide (TCO). To supply sufficient voltage to drive the EC devices, two series connected, semitransparent DSSCs were fabricated with 7 nm-thick, dye-adsorbed TiO2 and 4 nm-thick Pt layers. The two series connected, semitransparent DSSCs that were used had an open circuit voltage and short circuit current density of about 1.35 V and 3.96 mA cm−2, respectively, at 1-sun. The tandem DSSC-EC devices showed an optical density difference of 1.2 at 750 nm and reasonable response times of about 60 and 45 s during the coloring and bleaching processes, respectively, indicating that the two series-connected, semitransparent DSSCs could be used as the power sources in the tandem photovoltaic-powered EC devices.