On the Nature of Trapped-Hole States in CdS Nanocrystals and the Mechanism of Their Diffusion,The Journal of Physical Chemistry Letters

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On the Nature of Trapped-Hole States in CdS Nanocrystals and the Mechanism of Their Diffusion
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2018-06-01 00:00:00 , DOI: 10.1021/acs.jpclett.8b01148
R. Peyton Cline ₁ , James K. Utterback ₁ , Steven E. Strong ₁ , Gordana Dukovic ₁ , Joel D. Eaves ₁

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Recent transient absorption experiments on CdS nanorods suggest that photoexcited holes rapidly trap to the surface of these particles and then undergo diffusion along the rod surface. In this Letter, we present a semiperiodic density functional theory model for the CdS nanocrystal surface, analyze it, and comment on the nature of both the hole-trap states and the mechanism by which the holes diffuse. Hole states near the top of the valence band form an energetic near continuum with the bulk and localize to the nonbonding sp³ orbitals on surface sulfur atoms. After localization, the holes form nonadiabatic small polarons that move between the sulfur orbitals on the surface of the particle in a series of uncorrelated, incoherent, thermally activated hops at room temperature. The surface-trapped holes are deeply in the weak-electronic coupling limit and, as a result, undergo slow diffusion.

中文翻译：

CdS纳米晶体中陷阱孔性质的性质及其扩散机理

最近在CdS纳米棒上进行的瞬态吸收实验表明，光激发的空穴会迅速捕获到这些颗粒的表面，然后沿棒表面扩散。在这封信中，我们介绍了CdS纳米晶体表面的半周期密度泛函理论模型，对其进行了分析，并对空穴陷阱状态的性质以及空穴扩散的机理进行了评论。在价带顶部附近的空穴状态与主体形成一个高能近连续体，并位于非键合sp ^3上。表面硫原子上的轨道。定位后，这些孔会形成非绝热的小极化子，这些极化子在室温下以一系列不相关，不相干的热激活啤酒花在颗粒表面的硫轨道之间移动。被表面俘获的空穴深处在弱电子耦合极限中，并且因此经历缓慢的扩散。

更新日期：2018-06-01

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