Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Nano Lett. 2013 Mar 13;13(3):1092-9. doi: 10.1021/nl304426y. Epub 2013 Feb 11.
Nanomaterials with efficient carrier multiplication (CM), that is, generation of multiple electron-hole pairs by single photons, have been the object of intense scientific interest as potential enablers of high efficiency generation-III photovoltaics. In this work, we explore nanocrystal shape control as a means for enhancing CM. Specifically, we investigate the influence of aspect ratio (ρ) of PbSe nanorods (NRs) on both CM and the inverse of this process, Auger recombination. We observe that Auger lifetimes in NRs increase with increasing particle volume and for a fixed cross-sectional size follow a linear dependence on the NR length. For a given band gap energy, the CM efficiency in NRs shows a significant dependence on aspect ratio and exhibits a maximum at ρ ∼ 6-7 for which the multiexciton yields are a factor of ca. 2 higher than those in quantum dots with a similar bandgap energy. To rationalize our experimental observations, we analyze the influence of dimensionality on both CM and non-CM energy-loss mechanisms and offer possible explanations for the seemingly divergent effects the transition from zero- to one-dimensional confinement has on the closely related processes of Auger recombination and CM.
具有高效载流子倍增（CM）的纳米材料，即通过单个光子产生多个电子-空穴对，一直是科学界的研究热点，因为它们可能成为高效第三代光伏的实现手段。在这项工作中，我们探索了纳米晶体形状控制作为增强 CM 的一种手段。具体来说，我们研究了 PbSe 纳米棒（NRs）的纵横比（ρ）对 CM 和这一过程的逆过程——俄歇复合的影响。我们观察到，NR 中的俄歇寿命随着粒子体积的增加而增加，而对于固定的横截面尺寸，其线性依赖于 NR 的长度。对于给定的带隙能量，NR 中的 CM 效率对纵横比有显著的依赖性，并在 ρ∼6-7 时表现出最大值，此时多激子产率比具有相似带隙能量的量子点高约 2 倍。为了使我们的实验观察合理化，我们分析了维度对 CM 和非-CM 能量损耗机制的影响，并对从零维到一维限制的转变对密切相关的俄歇复合和 CM 过程的看似发散的影响提供了可能的解释。
