Role of Core–Shell Interfaces on Exciton Recombination in CdSe–Cd_xZn_1–xS Quantum Dots

The shell thickness and composition of CdSe–Cd_xZn_1–xS core–shell quantum dots (QDs) are defining parameters for the efficiency of such materials as light emitters. In this work we present a detailed study into the optical absorption and fluorescence properties of CdSe–CdS, CdSe–Cd_0.5Zn_0.5S, and CdSe–ZnS QDs as a function of shell thickness. Moreover, the single-exciton recombination dynamics of these systems are analyzed by means of a time-correlated single-photon counting technique and directly related to the specific core–shell interfaces of the various QDs studied using a phenomenological kinetic model. The findings from this model highlight the strong role of the core–shell interface on both steady state photoluminescence and exciton recombination dynamics in these systems.