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,

2,

3,

4} , B. Scott Fales _{1,

4,

5,

6,

7} , Yinan Shu _{1,

4,

8,

9} , Benjamin G. Levine _{1,

2,

3,

4}

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：

重组的动力学通过锥形相交在半导体纳米晶体

众所周知，圆锥形相交会在分子中引入非辐射衰变途径，但直到最近才涉及材料的非辐射重组过程。在这里我们应用激发态从头算基于对电子结构的多参考描述的分子动力学模拟，该电子结构对直径最大为1.7 nm的有缺陷的硅纳米晶体进行了搜索，以寻找可及的非辐射重组途径。发现悬空键缺陷在不同尺寸的五个系统的基态和第一激发电子态之间引起锥形相交。这些缺陷诱发的圆锥形交叉点可以在可见范围（2.4-2.7 eV）的能量下接近，并且对颗粒大小的依赖性很小。动态模拟表明，在产生缺陷定位的激励之后，这些相交点进入40-60 fs。这种超快速的重组归因于以下事实：在第一个激发态上的Jahn-Teller畸变将缺陷直接驱动到与基态电子态的圆锥形相交处。

更新日期：2017-11-22

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