Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots
Ma Hong(马红)a), Ma Guo-Hong(马国宏)a)†, Wang Wen-Jun(王文军)b), Gao Xue-Xi(高学喜)b), and Ma Hong-Liang(马洪良)c)
a Department of Physics, Shanghai University, Shanghai 200444, China; bSchool of Physics Science and Information Engineering, Liaocheng University, Liaocheng 252059, China; cInstrumental Analysis and Research Center, Shanghai University, Shanghai 200444, China
Abstract Size-dependence of optical properties and energy relaxation in CdSe/ZnS quantum dots (QDs) were investigated by two-colour femtosecond (fs) pump--probe (400/800 nm) and picosecond time-resolved photoluminescence (ps TRPL) experiments. Pump--probe measurement results show that there are two components for the excited carriers relaxation, the fast one with a time constant of several ps arises from the Auger-type recombination, which shows almost particle size-independence. The slow relaxation component with a time constant of several decades of ns can be clearly determined with ps TRPL spectroscopy in which the slow relaxation process shows strong particle size-dependence. The decay time constants increase from 21 to 34 ns with the decrease of particle size from 3.2 to 2.1 nm. The room-temperature decay lifetime is due to the thermal mixing of bright and dark excitons, and the size-dependence of slow relaxation process can be explained very well in terms of simple three-level model.
Received: 22 June 2007
Revised: 22 October 2007
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant No 10774099), Science and
Technology Commission of Shanghai Municipal (Grant No 06PJ14042),
Shanghai Municipal Education Commission (Grant No 06AZ089), and the
Shanghai Leading A
Cite this article:
Ma Hong(马红), Ma Guo-Hong(马国宏), Wang Wen-Jun(王文军), Gao Xue-Xi(高学喜), and Ma Hong-Liang(马洪良) Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots 2008 Chin. Phys. B 17 1280
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