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Center for Nonlinear Studies |
Emission of light in semiconductor nanocrystals proceeds through recombination of confined electron-hole pairs, or excitons, with tunable size-dependent resonant frequencies. Usually, their brightness is reduced by the ``dark exciton'' -- a non-emissive state into which electron-hole pairs relax before recombining radiatively. It was conjectured that, in cesium lead halide perovskite nanocrystals, the lowest exciton involves a highly emissive triplet state. However, this conjecture was proved to be invalid by magneto-photoluminescence spectroscopy of single nanocrystals. Nevertheless, the search for nanocrystals with the bright ground exciton state remains ongoing. In this talk I will analyze the fine structure of exciton states in wurtzite CdSe nanorods and demonstrate that, for cylindrical nanorods of small enough radii and aspect ratios larger than a certain critical value, the exciton ground state is the bright emissive state polarized parallel to the axis of the nanorod.
Host: Andrei Piryatinski (T-4)