Large-scale growth of Cu₂ZnSnSe₄ and Cu ₂ZnSnSe₄/Cu₂ZnSnS₄ core/shell nanowires

We present a fast and simple protocol for large-scale preparation of quaternary Cu₂ZnSnSe₄ (CZTSe), as well as CZTSe/Cu ₂ZnSnS₄ (CZTS) core/shell nanowires using CuSe nanowire bundles as self-sacrificial templates. CuSe nanowire bundles were synthesized by reacting Cu_{2 - x}Se nanowire bundles with sodium citrate solution. CZTSe nanowires were prepared by reacting CuSe nanowire bundles with Zn(CH ₃COO)₂ and SnCl₂ in triethylene glycol. X-ray diffraction (XRD) and selected area electron diffraction studies show that stannite CZTSe is formed. The formed CZTSe nanowire bundles have diameters of 200-400nm and lengths of up to hundreds of micrometers. CZTSe/CZTS nanocable bundles with similar morphologies were grown by the addition of some elemental sulfur to the reaction system for growth of CZTSe bundles. The stannite CZTSe/kesterite CZTS core/shell structure of the grown nanocables was confirmed by XRD and high-resolution transmission electron microscope investigation. The influence of S/Se molar ratio in the reaction system on the crystallographic structures and optical properties of CZTSe/CZTS nanocables was studied. The obtained CZTSe/CZTS core/shell nanocable bundles show broad and enhanced optical absorption over the visible and near-infrared region, which is promising for use in photovoltaic applications.