Hierarchical TiO2 flowers built from TiO2 nanotubes for efficient Pt-free based flexible dye-sensitized solar cells

A novel hierarchical TiO2 flower consisting of anatase TiO2 nanotubes on a Ti foil substrate has been prepared via a mild hydrothermal reaction of TiO2 nanoparticles/Ti foil. The photovoltaic performance of DSSC based on hierarchical TiO2 flowers/Ti (7.2%) is much higher than that of TiO2 nanoparticle/Ti (6.63%) because of its superior light scattering ability and fast electron transport. Moreover, full flexible DSSC based on the novel hierarchical TiO2 flowers/Ti foil photoelectrode and electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) on indium tin oxide-coated poly(ethylene terephthalate) (ITO-PET) counter electrode shows a significant power conversion efficiency of 6.26%, accompanying a short-circuit current density of 11.96 mA cm(-2), an open-circuit voltage of 761 mV and a fill factor of 0.69.