Facet-Dependent SnS Nanocrystals as the High-Performance Counter Electrode Materials for Dye-Sensitized Solar Cells

SnS, composed of earth abundant and environmentally benign elements, is a unique material for wide applications in thermoelectricity, solar energy conversion, photocatalysis, and electrochemical energy storage. The controllable synthesis of SnS nanocrystals with exposed different facets is meaningful. In general, an alkylphosphine ligand was used in the preparation of SnS nanocrystals to control its chemical formulas and morphologies. Here, the two-dimensional square-shaped SnS nanosheets (SnS-S) and pentahedron-shaped SnS nanocrystals (SnS-P) were controllably synthesized with alkylamine ligands. The preferential binding of oleylamine and hexadecylamine to the (100) and (130) facets of SnS, respectively, restricted the further growth of the (100) and (130) facets. Then SnS-S with (100) and SnS-P with (130) facets were prepared. The nanomaterial with special facets usually exhibited unique physical and chemical properties compared with the conventional material. When they were exploited as counter electrode (CE) catalysts for dye-sensitized solar cells (DSSCs), the device based on the SnS-S electrode achieved a satisfactory photoelectric conversion efficiency of 8.96%, superior to that of the SnS-P (8.23%) and conventional Pt (7.72%). The excellent DSSCs performance of SnS-S was mainly attributed to the exposed (100) facets improving the catalytic activity for the I-3(-) reduction and the unique layer structure accelerating the electron transfer. It provided a novel insight into preparing a high-performance SnS-based CE catalyst.