Hydrothermal synthesis of Fe- and Nb-doped titania nanobelts and their tunable electronic structure toward photovoltaic application

One-dimensional (1D) oxide nanostructures have been widely investigated to find novel properties. The study prepared titania nanobelts doped with iron (Fe) and niobium (Nb) at ultralow concentrations by one-step hydrothermal synthesis and post-calcination, and explored their electronic structure by spectroscopic and electrochemical analyses. The Fe and Nb doping generated Ti3+ donor levels and trap states as well as induced bandedge shift. The doped nanobelts produced higher photocurrents and quantum efficiencies, when evaluated as anode materials in dye-sensitized solar cells. Formation of the shallow states exerts a major influence on charge carrier diffusion in titania nanobelts, because of their roles as photoactive sites to facilitate electron transport via hopping and trapping/de-trapping events. The Fe and Nb dopants have a synergistic effect in the electronic conduction by increasing electron density and lifetime. Results demonstrate a feasibility of using aliovalent substitution by co-dopants to tailor extrinsic 1D oxide semiconductors.