We report the single dot and ensemble spectroscopy studies of colloidal core/thick-shell CdSe/CdS nanocrystals (NCs) combined with the theoretical modeling of the exciton and trion states. At low temperatures NCs are permanently negatively charged and demonstrate trion emission with short radiative life time and 100% quantum yield (QY) 1. The sign of the charge is unambiguously determined by polarization-resolved ensemble photoluminesence (PL) measurements in high magnetic ?elds. Single dot spectroscopy in the range 30�300 K shows that the non-radiative Auger recombination is thermally activated around 200 K resulting into the lowering of the QY while the trion radiative life time increases with increase of the temperature. Experimental results are well described by a model suggesting a temperature-dependent delocalization of one of the trion electrons from the CdSe core and enhanced Auger recombination at the abrupt CdS outer surface. These results point to a route for the design of core/shell structures with 100% quantum yield at room temperature.[1] C. Javaux et al. Nature Nanotechnology published on line: 10 FEBRUARY 2013 | DOI: 10.1038/NNANO.2012.260

Thermal activation of the Auger processes in charged CdSe/CdS core/shell NCs

246th National Meeting (2013)

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