Jones Marcus, Lo Shun S, Scholes Gregory D
Department of Chemistry, 80 Saint George Street, Institute for Optical Sciences, and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, ON, Canada M5S 3H6.
Proc Natl Acad Sci U S A. 2009 Mar 3;106(9):3011-6. doi: 10.1073/pnas.0809316106. Epub 2009 Feb 13.
Charge carrier trapping is an important phenomenon in nanocrystal (NC) decay dynamics because it reduces photoluminescence (PL) quantum efficiencies and obscures efforts to understand the interaction of NC excitons with their surroundings. Particularly crucial to our understanding of excitation dynamics in, e.g., multiNC assemblies, would be a way of differentiating between processes involving trap states and those that do not. Direct optical measurement of NC trap state processes is not usually possible because they have negligible transition dipole moments; however, they are known to indirectly affect exciton photoluminescence. Here, we develop a framework, based on Marcus electron transfer theory, to determine NC trap state dynamics from time-resolved NC exciton PL measurements. Our results demonstrate the sensitivity of PL to interfacial dynamics, indicating that the technique can be used as an indirect but effective probe of trap distribution changes. We anticipate that this study represents a step toward understanding how excitons in nanocrystals interact with their surroundings: a quality that must be optimized for their efficient application in photovoltaics, photodetectors, or chemical sensors.
电荷载流子俘获是纳米晶体（NC）衰变动力学中的一个重要现象，因为它会降低光致发光（PL）量子效率，并妨碍人们理解NC激子与其周围环境的相互作用。对于我们理解例如多NC组件中的激发动力学而言，尤为关键的是要找到一种方法，来区分涉及陷阱态的过程和不涉及陷阱态的过程。通常无法直接通过光学手段测量NC陷阱态过程，因为它们的跃迁偶极矩可以忽略不计；然而，已知它们会间接影响激子的光致发光。在此，我们基于马库斯电子转移理论开发了一个框架，用于从时间分辨的NC激子PL测量中确定NC陷阱态动力学。我们的结果证明了PL对界面动力学的敏感性，表明该技术可作为陷阱分布变化的一种间接但有效的探测手段。我们预计，这项研究朝着理解纳米晶体中的激子如何与其周围环境相互作用迈出了一步：这一特性对于它们在光伏、光电探测器或化学传感器中的高效应用而言必须进行优化。
