Growth Kinetics of Monodisperse Cu-In-S Nanocrystals Using a Dialkyl Disulfide Sulfur Source

Well-defined and monodisperse wurtzite Cu-In-S nanocrystals were synthesized via a solution-based method using di-tert-butyl disulfide as the sulfur source. Reaction control (i.e., coordinating solvent, capping ligand, and sulfur source) proved critical for providing a kinetic pathway to the metastable wurtzite phase. The crystal phase was confirmed by powder X-ray diffraction and selected area electron diffraction. Quantitative nanocrystal growth kinetics were studied on a Cu-In-S system for the first time, clearly showing that the nanocrystals pass through a size focusing event before undergoing steady-state Ostwald ripening at later stages of growth. The size-focused 6.9 nm Cu-N-S nanocrystals have an optical band gap of E-g = 1.47 eV and an electrochemical band gap of E-g = 1.84 eV.