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

• SnO2–TiO2 branched nanostructure serves as model architecture for DSSCs.
• The novel structure combines fast electron transport, slow recombination and high specific surface area.
• A maximum efficiency of 7.06% was achieved.

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 (Jsc, 20.5 mA cm−2) as compared with the commonly used P25 photoanode (11.7 mA cm−2). Our results indicate that Jsc 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.

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