Structural and Electrical Properties of Nb‐Doped Anatase TiO ₂ Nanowires by Electrospinning

Abstract

One‐dimensional nanostructures of niobium‐doped anatase TiO 2 (Nb:TiO 2 ) up to 5 at.% Nb were synthesized by electrospinning a polymeric solution containing titanium and niobium precursors and subsequent annealing. Thus obtained fibers had diameter ∼150 nm. The undoped TiO 2 fibers were constituted by larger single crystalline grains of size ∼50 nm, whereas the doped ones had decreased grain sizes (∼30 nm) under similar processing conditions. The Nb doping decreased the BET surface area of TiO 2 . A strain‐induced lattice contraction was observed in Nb:TiO 2 . The continuous nanofibers were shortened to nanowires (NW) of aspect ratio 10:1 by ultrasonically dispersing them in acetic acid, which were developed as films of thickness ∼8–13 μm onto conducting glass substrates. The TiO 2 and Nb:TiO 2 nanowire films were further sensitized by a dye; the amount of dye anchored was found to decrease with increase in the dopant concentration. The dye‐sensitized solar cells fabricated using the doped fibers, although with a nominally increased current density ( J SC ), have reduced efficiency due to lower fill factor and open circuit voltage ( V OC ). The electron diffusion coefficient ( D n ) and mobility (μ n ) of the TiO 2 and Nb:TiO 2 NW in the presence of iodide/triiodide ions were an order of magnitude higher compared with the undoped samples.