Application of femtosecond transient absorption in the visible and near-IR spectral ranges and time-resolved photoluminescence allows us to separate electron and hole relaxation paths and to map the structure of interband and intraband optical transitions in CdSe and CdS nanocrystals (NC’s) with a wide range of surface properties. In contrast to electron relaxation, which is controlled by NC surface passivation, depopulation of hole quantized states is extremely fast (sub-ps-to-ps time scales) in all types samples, independent of NC surface treatment (including NC’s overcoated with a ZnS layer). Our results suggest that ultrafast hole dynamics are not due to trapping at localized surface defects such as a vacancy, but rather arise from relaxation into intrinsic NC states or intrinsically unpassivated interface states.

• Received 2 September 1998

DOI:https://doi.org/10.1103/PhysRevB.60.R2177