Size-, shape-, and composition-controlled synthesis and localized surface plasmon resonance of copper tin selenide nanocrystals

We report a robust methodology for synthesizing monodisperse copper-tin-selenide (CTSe) nanocrystals (NCs) of tunable size, shape, and composition including single-crystalline nanosheets, nanoplates, spheres, and tetrahedra. Both the identity and concentration of the selenium precursor play important roles in determining the morphology and crystal structure of the CTSe NCs. In contrast to previous studies, we demonstrated broad tunability of the Cu to Sn ratio. The size of CTSe NCs continuously decreased with increasing Sn incorporation. Moreover, the near-infrared (NIR) localized surface plasmon resonance (LSPR) in CTSe alloy NCs was tuned over a broad range by varying the Cu:Sn ratio. The LSPR red-shifted and decreased in intensity with increasing Sn content. This indicates that the free charge carrier concentration can be manipulated by varying the cation ratio. The cation deficiency responsible for self-doping in these NCs decreases with increasing Sn content. The resulting CTSe NCs and related materials with tunable size, shape, band gap, and doping level provide new opportunities in solution-processed optoelectronic devices.