CuInS2/ZnS core/shell quantum dots by cation exchange and their blue-shifted photoluminescence

Highly luminescent CuInS2/ZnS (CIS/ZnS) core/shell quantum dots with a quantum yield of 65% were synthesized by a cation exchange reaction. Similar sized CIS cores and CIS/ZnS core/shells, which were confirmed by TEM, showed that cation exchange occurred inside the core, which reduced the core size and increased the blue-shift in their emission. ICP revealed the CIS cores to have a gradient composition that is richer in indium close to the surface of the core, which explains the broad emission spectrum. This cation exchange reaction could be applied to AgInS2 (AIS) QDs, which showed a blue shift of 70 nm in the emission spectrum. The PXRD pattern also showed a peak shift as evidence of a core/shell structure.