Challenge to the deep-trap model of the surface in semiconductor nanocrystals

Temperature-dependent photoluminescence spectra of a range of semiconductor nanocrystals are presented which reveal an unanticipated thermodynamic relationship between the core excitonic states and the surface of the nanocrystal. These results challenge the widely held view of the surface emission arising from an energetically broad distribution of midgap defect states at the surface. We show that a simpler model based on semiclassical electron transfer and invoking only a single surface state uniquely describes all observables.