Doping by introducing transition metal ions into host lattice is an efficient strategy to modify and/or introduce new properties of nanocrystals. The final properties of doped quantum dots (QDs) highly depend on the dopant sites because of the distance-dependent host-dopant coupling. Recent discovery of dopant migration inside core/shell QDs provide a new way to fine tune the properties of doped QDs. Although the dopant ion migration was found to be thermodynamically driven in CdS/ZnS core/shell QDs, whether the dopant migration can be further controlled by intentionally inserted shell(s) with less size mismatch with dopant is still unknown. In this work, we aim to control the Mn dopant migration rate and distance through the introduction of different thicknesses of CdZnS alloyed shell in CdS/CdZnS/ZnS core/shell/shell QDs. The radial position of the Mn inside the CdS/CdZnS/ZnS QDs was monitored by the Mn photoluminescence (PL) peak because Mn PL is very sensitive to the shell applied pressure (proportional to shell thickness) based on the spherically symmetric elastic continuum model. It was found that upon growth of thicker CdZnS alloyed interface, the dopants were able to migrate further away from the CdS core resulting in a smaller redshift in Mn PL. Furthermore, the delocalization of core excitons into the CdZnS shell provides further opportunity to finely control the CdS PL position and the CdS to Mn PL ratio.

Fast dopant migration in Mn:CdS/CdZnS/ZnS core/shell/shell quantum dots

256th National Meeting (2018)

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