Wet chemical route to hierarchical TiO2 nanodendrite/nanoparticle composite anodes for dye-sensitized solar cells

Hierarchical rutile TiO2 nanodendrite (ND)/nanoparticle (NP) composite films have been synthesized on fluorine-doped tin oxide (FTO) substrates for use in dye-sensitized solar cells (DSSCs). The rutile TiO2 ND array is first derived from the nanowire (NW) array on FTO by the growth of the branches on the surface of the TiO2 NWs using a wet chemical route in the absence of an organic structure-directing agent. High-resolution transmission electron microscopy (HRTEM) characterization shows that twin structures appear at the boundary of the NWs and branches. The NPs are subsequently grown within the interstices of the ND array by another chemical bath deposition. With an anode thickness of 3 mm, the efficiency of the rutile TiO2 ND/NP DSSC is superior to that of the P25 DSSC. Although a slower electron transport rate is observed in the rutile TiO2 ND/NP anode compared to the P25 anode, the rutile TiO2 ND/NP anode possesses a significantly larger electron lifetime and therefore a superior diffusion length.