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Nat Commun. 2011;2:280. doi: 10.1038/ncomms1281.

Nano-engineered electron-hole exchange interaction controls exciton dynamics in core-shell semiconductor nanocrystals.

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  • 1Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.


A strong electron-hole exchange interaction (EI) in semiconductor nanocrystals (NCs) gives rise to a large (up to tens of meV) splitting between optically active ('bright') and optically passive ('dark') excitons. This dark-bright splitting has a significant effect on the optical properties of band-edge excitons and leads to a pronounced temperature and magnetic field dependence of radiative decay. Here we demonstrate a nanoengineering-based approach that provides control over EI while maintaining nearly constant emission energy. We show that the dark-bright splitting can be widely tuned by controlling the electron-hole spatial overlap in core-shell CdSe/CdS NCs with a variable shell width. In thick-shell samples, the EI energy reduces to <250 μeV, which yields a material that emits with a nearly constant rate over temperatures from 1.5 to 300 K and magnetic fields up to 7 T. The EI-manipulation strategies demonstrated here are general and can be applied to other nanostructures with variable electron-hole overlap.

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