Direct synthesis of highly luminescent Cu–Zn–In–S quaternary nanocrystals with tunable photoluminescence spectra and decay times

We report the direct synthesis of highly luminescent Cu–Zn–In–S (CZIS) quaternary nanocrystals (NCs) in the non-coordinating solvent 1-octadecene (ODE) using chloride salts of Cu, In, and Zn as metal precursors in the presence of oleic acid and dodecanethiol. The resulting CZIS NCs had a narrow size distribution with an average diameter of 2.5 nm. The photoluminescence spectra can be tuned from 400 nm–850 nm by varying the Cu : Zn precursor ratio, and a relatively high photoluminescence quantum yield (PL QY) of 46% was obtained without any post-processing. The PL decay times of the as-prepared CZIS NCs were tunable via controlling the Cu : Zn precursor ratio and reaction time. The photoluminescence mechanism of the CZIS nanocrystals was discussed using the PL decay curves. EDS analysis revealed that the resulting CZIS NCs were Cu-deficient, and the internal defect-related emission process could be strongly promoted by the large Cu deficiency which is associated with the improvement of PL QY.