Effects of Inhomogeneous Shell Thickness in the Charge Transfer Dynamics of ZnTe/CdSe Nanocrystals

ZnTe/CdSe core/shell nanocrystals with varying ZnTe core sizes and CdSe shell thickness have been synthesized. The absorption onset and photoluminescence (PL) wavelengths vary from the mid-visible to the near-infrared range. The conduction and valence band energies as well as bandgap and electron hole overlap are accurately described by an effective mass approximation model. These particles are type-II, with the hole confined to the ZnTe core. PL quenching dynamics of ZnTe/CdSe nanocrystals having various shell thicknesses by hole acceptors are studied. A model has been developed to describe the interfacial charge transfer of the core-confined holes to adsorbed acceptors. This model considers a Poisson distribution of acceptor numbers and includes shell thickness variability. The shell thickness variability occurs on each particle and corresponds to surface roughness. The shell local thickness is assumed to have a Poisson distribution of numbers of layers.