Dynamics of recombination via conical intersection in a semiconductor nanocrystal†,Chemical Science

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Dynamics of recombination via conical intersection in a semiconductor nanocrystal†
Chemical Science ( IF 7.6 ) Pub Date : 2017-11-13 00:00:00 , DOI: 10.1039/c7sc04221c
Wei-Tao Peng ₁ , B Scott Fales _{2,

3} , Yinan Shu ₄ , Benjamin G Levine ₁

Affiliation

Conical intersections are well known to introduce nonradiative decay pathways in molecules, but have only recently been implicated in nonradiative recombination processes in materials. Here we apply excited state ab initio molecular dynamics simulations based on a multireference description of the electronic structure to defective silicon nanocrystals up to 1.7 nm in diameter to search for accessible nonradiative recombination pathways. Dangling bond defects are found to induce conical intersections between the ground and first excited electronic states of five systems of various sizes. These defect-induced conical intersections are accessible at energies that are in the visible range (2.4–2.7 eV) and very weakly dependent on particle size. The dynamic simulations suggest that these intersections are accessed 40–60 fs after creation of a defect-localized excitation. This ultrafast recombination is attributed to the fact that Jahn–Teller distortion on the first excited state drives the defect directly towards a conical intersection with the ground electronic state.

中文翻译：

半导体纳米晶体中通过圆锥形相交的复合动力学†

众所周知，圆锥形交叉会在分子中引入非辐射衰变路径，但直到最近才与材料中的非辐射复合过程相关。在这里，我们将基于电子结构多参考描述的激发态从头开始分子动力学模拟应用于直径达 1.7 nm 的有缺陷的硅纳米晶体，以寻找可访问的非辐射复合路径。研究发现，悬挂键缺陷会引起五个不同尺寸系统的基态和第一激发电子态之间的锥形交叉。这些缺陷引起的锥形交叉点可以在可见光范围（2.4-2.7 eV）的能量下实现，并且对颗粒尺寸的依赖性非常弱。动态模拟表明，在创建缺陷局部激励后 40-60 fs 即可访问这些交叉点。这种超快复合归因于第一激发态上的 Jahn-Teller 畸变将缺陷直接驱动到与电子基态的圆锥形相交。

更新日期：2017-11-13

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