A model for the multi-exponential excited-state decay of CdSe nanocrystals
We report on photoluminescence decay measurements of CdSe nanoparticles over several decades of intensities and times, and as a function of size and temp. A model is proposed for the multi-exponential decay kinetics, and their temp. dependence, in which a major role is played by the now well established presence of a large ground-state dipole moment in CdSe nano crystals. By two-photon excitation within the bandgap region we show that there is a link between the ground-state dipole moment and the excited-state decay. The stochastic nature of the magnitude of the dipole moment results in a complex temp. dependence. Contrary to studies that ascribe non-radiative decay processes to surface states/traps, the mechanism we propose considers the intrinsic states described within the effective mass approxn. models for the spectroscopy of the bandgap. Surface effects are mediated by the ground-state dipole moments that they constitute, which in turn perturb the intrinsic states.
Keywords: Cadmium selenide ; Nanoparticles ; Electron-hole recombination ; Nanosecond kinetics ; Dipole moments ; Permanent Dipole-Moment ; Quantum Dots ; Radiative Decay ; Dark-Exciton ; Monodisperse ; Luminescence ; Dependence ; Origin
Laboratoire de Spectroscopie Ultrarapide,Ecole Polytechnique Federale de Lausanne, ISIC-FSB-BSP,Lausanne,Switz.
written in English.
Record created on 2006-02-27, modified on 2016-08-08