Niobium and iron co-doped titania nanobelts for improving charge collection in dye-sensitized TiO2 solar cells

Niobium (Nb) and iron (Fe) co-doped titanium oxide nanobelts were prepared in a one-pot alkaline hydrothermal process followed by calcination treatment, and evaluated in TiO2 nanoparticle-based composite anodes for dye-sensitized solar cells. Addition of Nb and Fe species caused an increase in donor density and trap-mediated charge transition, as characterized by electrochemical and photoluminescence analyses. Under illumination with simulated solar light, the co-doped single-crystalline nanobelts promoted photocurrent yield and open-circuit voltage, because they facilitate electronic conduction and chemical capacitance in the composite anodes. This improved photovoltaic performance is associated with the enhanced charge collection efficiency, mechanistically attributed to rapid electron transport and prolonged electron lifetime via shallow trapping sites. Results demonstrate that the Nb and Fe co-doped titania nanobelts are effective to provide longer electron diffusion lengths and favor charge accumulation during cell operation.