Philbin John P, Rabani Eran
Department of Chemistry , University of California , Berkeley , California 94720 , United States.
The Sackler Center for Computational Molecular and Materials Science , Tel Aviv University , Tel Aviv 69978 , Israel.
Nano Lett. 2018 Dec 12;18(12):7889-7895. doi: 10.1021/acs.nanolett.8b03715. Epub 2018 Nov 12.
The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valence electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron-hole models. Herein we present a novel approach for calculating Auger recombination lifetimes in confined nanostructures having thousands to tens of thousands of electrons, explicitly including electron-hole interactions. We demonstrate that the inclusion of electron-hole correlations are imperative to capture the correct scaling of the Auger recombination lifetime with the size and shape of the nanostructure. In addition, correlation effects are required to obtain quantitatively accurate lifetimes even for systems smaller than the exciton Bohr radius. Neglecting such correlations can result in lifetimes that are two orders of magnitude too long. We establish the utility of the new approach for CdSe quantum dots of varying sizes and for CdSe nanorods of varying diameters and lengths. Our new approach is the first theoretical method to postdict the experimentally known "universal volume scaling law" for quantum dots and makes novel predictions for the scaling of the Auger recombination lifetimes in nanorods.
通过俄歇复合实现的多激子态快速非辐射衰变是一个影响基于半导体纳米结构的多种应用的基本过程。从理论角度来看，由于大量价电子以及通过库仑相互作用耦合的激发激子态和双激子态数量呈指数增长，描述受限半导体纳米结构中的俄歇复合是一项具有挑战性的任务。这些挑战使得俄歇复合的处理局限于简单的、非相互作用的电子 - 空穴模型。在此，我们提出一种新颖的方法来计算具有数千到数万个电子的受限纳米结构中的俄歇复合寿命，明确考虑电子 - 空穴相互作用。我们证明，包含电子 - 空穴相关性对于捕捉俄歇复合寿命随纳米结构尺寸和形状的正确缩放关系至关重要。此外，即使对于小于激子玻尔半径的系统，也需要相关性效应来获得定量准确的寿命。忽略这种相关性会导致寿命比实际长两个数量级。我们确立了这种新方法对于不同尺寸的CdSe量子点以及不同直径和长度的CdSe纳米棒的实用性。我们的新方法是第一种能够推断出量子点实验已知的“通用体积缩放定律”并对纳米棒中俄歇复合寿命的缩放做出新预测的理论方法。
