期刊
CHEMICAL PHYSICS
卷 357, 期 1-3, 页码 96-101出版社
ELSEVIER
DOI: 10.1016/j.chemphys.2008.10.042
关键词
Cadmium selenide; Nanoparticles; Electron-hole recombination; Nanosecond kinetics; Dipole moments
资金
- Swiss National Science Foundation [200020-105333]
- NCCR Quantum Photonics program.
We report on photoluminescence decay measurements of CdSe nanoparticles over several decades of intensities and times, and as a function of size and temperature. A model is proposed for the multi-exponential decay kinetics, and their temperature 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 temperature 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 approximation 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. (c) 2008 Elsevier B.V. All rights reserved.
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