Core/shell quantum dots (QDs) have attracted much interest among experimentalists and theoreticians in recent years due to their unique characteristics (e.g., in reducing or eliminating fluorescence quenching as well as optical blinking, introducing carrier multiplication, and in opening up new absorption/relaxation channels not present in the respective core or shell materials). Here, we present DFT and TDDFT studies of Pb16X16/Cd52Y52 (X, Y = S, Se, Te) Core/Shell quantum dots (QDs). We examined the ground state properties of these systems (i.e., the optimized geometries, density of states, projected density of states, and optical absorption spectra). Most of the heterostructures were analyzed for the first time (e.g., Pb16S16/Cd52Te52 and Pb16Te16/Cd52Se52). We found the thin shell core/shell QDs to be largely borderline type II with much similarly between QDs containing Cd52S52 and Cd52Se52 shells, whereas core/shell QDs with a Cd52Te52 shell appeared to be borderline type-I. All shells were found to enhance the optical properties of the lead chalcogenide cores, brightening initially dark lowest energy transitions. In optimized geometries of the studied QDs, the Pb16X16 cores largely retained their bulk structures, whereas the relaxed shells assumed a somewhat spherical geometry due to surface reconstruction. We are currently performing nonadiabatic DFT-based dynamics, coupled with the surface hopping method, to investigate fates of excited electrons or holes in these systems.

Ground state properties and nonadiabatic dynamical studies of Pb16X16/Cd52Y52 (X, Y = S, Se, Te) core/shell quantum dots

251st National Meeting (2016)

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