Signatures of Exciton Dynamics and Carrier Trapping in the Time-Resolved Photoluminescence of Colloidal CdSe Nanocrystals
Signatures of Exciton Dynamics and Carrier Trapping in the Time-Resolved Photoluminescence of Colloidal CdSe Nanocrystals
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DOI：
10.1021/jp9078772
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发表时间：
2009-10-29
影响因子：
3.7
通讯作者：
Scholes, Gregory D.
中科院分区：
文献类型：
--
作者：
Jones, Marcus;Lo, Shun S.;Scholes, Gregory D.
表面效应显著影响胶体纳米晶体的光激发动力学，但由于样品的复杂性和陷阱态典型的小消光系数，其影响难以研究。利用温度依赖的时间分辨光致发光（PL）测量，我们研究了表面局域载流子陷阱对纳米晶体激子动力学的扰动。我们提出了一个基于Marcus电子转移理论的载流子捕获模型，并使用它来精确地再现五种核壳CdSe/CdZnS纳米晶体样品在宽温度范围内的PL动力学。由此产生的载流子动力学图像然后用于识别PL数据中的特征，这些特征可能用于随后的实验中，以揭示有关表面局域陷阱态的能量和分布的信息。我们发现，在某些情况下，陷阱能量的集合分布的形状可以准确地从单一温度下记录的数据中确定，这很容易从平均PL寿命图中确定。
Surface effects significantly affect the photoexcitation dynamics of colloidal nanocrystals, but their influence is hard to study because of sample complexity and the typically small extinction coefficient of trap states. Using temperature-dependent time-resolved photoluminescence (PL) measurements, we investigate the perturbations induced by surface-localized carrier traps on the exciton dynamics of the nanocrystals. We present a model of carrier trapping that is based on Marcus' electron-transfer theory and use it to accurately reproduce PL dynamics over a wide temperature range in five core-shell CdSe/CdZnS nanocrystal samples. The resulting pictures of carrier dynamics are then used to identify features in the PL data that may be used in subsequent experiments to reveal information about the energy and distribution of surface-localized trap states. We find that in certain cases, the shape of the ensemble distribution of trap energies can be accurately determined from data recorded at a single temperature that is easily identified from plots of average PL lifetime.