Synthesis and Optical Properties of Cubic Chalcopyrite/Hexagonal Wurtzite Core/Shell Copper Indium Sulfide Nanocrystals.

We report a synthetic method to produce heavy-metal-free heterophase core/shell CuInS2 nanocrystals, which comprise differently sized cores with a cubic chalcopyrite (CP) structure overgrown with hexagonal wurtzite (WZ) shells. For a given core size, CP/WZ core/shell CuInS2 nanocrystals experience shifts in both absorption and photoluminescence spectra toward the near-infrared with increasing shell thickness. Studies of the photoluminescence dynamics of these heterophase CuInS2 nanocrystals reveals behavior similar to that of the typical type II nanostructures constructed from different semiconductor materials of the same crystal structure. The interface between the CP core and the WZ shell has an important effect on the photoluminescence quantum yield.