Facile formation of a hierarchical TiO2–SnO2 nanocomposite architecture for efficient dye-sensitized solar cells†
In this paper, a hierarchical nanocomposite architecture consisting of TiO2 nanoflakes on SnO2 nanofibers was successfully synthesized using a simple and cost-effective hydrothermal method. The correlation between the structural changes in nanoflake size and density in accordance with the prolongation of hydrothermal growth duration was observed and discussed using high-resolution scanning and transmission electron microscopies. The dye-sensitized solar cells (DSSCs) utilizing these double-layered TiO2–SnO2 hierarchical nanostructures as photoelectrodes exhibited significant improvement in their photovoltaic properties. In particular, the DSSCs made from 24 h hydrothermally grown TiO2 nanoflakes on the surface of SnO2 nanofibers stood out to be the best performing cells, delivered a promising efficiency of 3.73%, which was more than a 4-fold increment over the DSSC with SnO2 nanofibers alone. This enhancement was attributed to the superiority in dye-loading and light scattering properties of the hierarchical architecture. Benefiting from the constituent advantages of both materials, the photoelectrodes with hierarchical nanostructures also inhibited back electron transfer to reduce electron recombination, leading to improved electron lifetime. These results suggest that a simple strategy to synthesize hierarchical nanostructures for efficient DSSCs was achieved.