Hierarchical SnO2@SnS2 Counter Electrodes for Remarkable High-efficiency Dye-sensitized Solar Cells

A hierarchical SnO2@SnS2 core-shell nanostructure has been prepared by in situ surface sulfurization of hollow SnO2 sphere via a facile two-step solution-based method and used as a substitute for conventional Pt counter electrode (CE) for dye-sensitized solar cells (DSSCs) for the first time. The resulted semitransparent SnO2@SnS2 CEs demonstrate a high electrical conductivity and excellent catalytic activity, which are attributed to the synergetic effect of each component in such hierarchical nanostructure. The hierarchical SnO2@SnS2 CE achieves an impressive photovoltaic conversion efficiency (PCE) of 8.08%, which is significantly higher than those of individual SnO2 (5.26%) and SnS2 (6.00%) and also higher than Pt (7.88%) by 2.5%. This study suggests that the inexpensive hierarchical SnO2@SnS2 CE is a good alternative to the expensive Pt CE in DSSCs.