Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots

• 来源期刊: 中国物理B（英文版）
• 关键词: semiconductor quantum dots Auger-type recombination time-resolved spectroscopy
• 年，卷（期）: 2008,（4）
• 页码范围: 1280-1285
• 页数: 6页
• 语种: 英文

摘要

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 sizeindependence. 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 34ns 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.