Branched hierarchical photoanode of titanium dioxide nanoneedles on tin dioxide nanofiber network for high performance dye-sensitized solar cells

We report a branched hierarchical nanostructure of TiO2 nanoneedles on SnO2 nanofiber network (B-SnO2 NF) that serves as model architecture for highly efficient dye-sensitized solar cells (DSSCs). The nanostructure simultaneously offers a low degree of charge recombination, a fast electron transport and a large specific surface area. The power conversion efficiency for B-SnO2 NF52 (with SnO2 NF diameter 52 nm) is up to 7.06%, increased by 26% and 40% compared to B-SnO2 NF113 (5.57%, with SnO2 NF diameter 113 nm) and TiO2 nanoparticle (5.04%, P25), respectively, and more than five times as large as SnO2 NF52 (1.34%). The distinct photovoltaic behavior of the B-SnO2 NF52 is its large short-circuit current density (J(sc), 20.5 mA cm(-2)) as compared with the commonly used P25 photoanode (11.7 mA cm(-2)). Our results indicate that J(sc) enhancement derived by the slower electron recombination associated with the SnO2-TiO2 core shell heterojunction and faster electron transport in SnO2 NF network could synergistically contribute to high efficiency. (C) 2014 Elsevier B.V. All rights reserved.