Effect of Electron-Hole Overlap and Exchange Interaction on Exciton Radiative Lifetimes of CdTe/CdSe Heteronanocrystals
Effect of Electron-Hole Overlap and Exchange Interaction on Exciton Radiative Lifetimes of CdTe/CdSe Heteronanocrystals
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DOI：
10.1021/acsnano.5b07158
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发表时间：
2016-04-01
期刊：
影响因子：
17.1
通讯作者：
Christianen, Peter C. M.
中科院分区：
文献类型：
--
作者：
del Aguila, Andres Granados;Groeneveld, Esther;Christianen, Peter C. M.
波函数工程已经成为定制半导体胶体纳米晶光学性质的有力工具。核壳系统允许分别设计导带和价带中电子(E)和空穴(H)波函数的空间范围。然而，调节e和h波函数之间的重叠不仅影响负责发光的耦合e-h对(激子)的振子强度，而且还改变e-h交换相互作用，导致激子能谱的改变。在这里，我们提出了在强磁场中测量激子寿命，以确定e-h交换相互作用的强度，而不依赖于从室温下的寿命测量得出的e-h重叠。我们使用了一组具有不同电子空穴间距的Cd Te/Cd Se核/壳异质晶体。我们能够揭示e-h重叠和e-h交换对激子寿命的单独影响，我们提出了一个简单的模型，该模型完全描述了异质结构(HNC)的复合寿命作为核体积、壳体积、温度和磁场的函数。
Wave function engineering has become a powerful tool to tailor the optical properties of semiconductor colloidal nanocrystals. Core-shell systems allow to design the spatial extent of the electron (e) and hole (h) wave functions in the conduction- and valence bands, respectively. However, tuning the overlap between the eand h -wave functions not only affects the oscillator strength of the coupled e-h pairs (excitons) that are responsible for the light emission, but also modifies the e-h exchange interaction, leading to an altered excitonic energy spectrum. Here, we present exciton lifetime measurements in a strong magnetic field to determine the strength of the e-h exchange interaction, independently of the e-h overlap that is deduced from lifetime measurements at room temperature. We use a set of CdTe/CdSe core/shell heteronanocrystals in which the electron hole separation is systematically varied. We are able to unravel the separate effects of e-h overlap and e-h exchange on the exciton lifetimes, and we present a simple model that fully describes the recombination lifetimes of heteronanostructures (HNCs) as a function of core volume, shell volume, temperature, and magnetic fields.