Effect of TiO2 modification on urchin-like orthorhombic Nb2O5 nanospheres as photoelectrodes in dye-sensitized solar cells

TiO 2 modification via TiCl 4 treatment has been widely used to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), in which the effects usually attribute to the inhibition of charge recombination by barrier effect. Niobium pentoxide (Nb 2 O 5 ) is considered a promising photoelectrode material for DSSCs. Here we prepared urchin-like orthorhombic Nb 2 O 5 nanospheres consisting of ultrathin nanorods by a hydrothermal method , which were further developed as photoelectrodes for DSSCs. The TiO 2 modification on the urchin-like orthorhombic Nb 2 O 5 nanospheres increases the photocurrent and PCE of the DSSCs. However, the impedance spectroscopy showed that charge recombination was not reduced by the TiO 2 modification. The improvement in the photocurrent and PCE has been attributed to the enhanced absorption of dye molecules (N719). The results indicate that the enhancement of dye absorption for orthorhombic Nb 2 O 5 photoelectrodes is the desirable approach to improve the performance of orthorhombic Nb 2 O 5 -based DSSCs.