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Intermolecular vibrations mediate ultrafast singlet fission.
Science Advances ( IF 13.6 ) Pub Date : 2020-09-18 , DOI: 10.1126/sciadv.abb0052
Hong-Guang Duan 1, 2, 3 , Ajay Jha 1 , Xin Li 4 , Vandana Tiwari 1, 5 , Hanyang Ye 6 , Pabitra K Nayak 7 , Xiao-Lei Zhu 4 , Zheng Li 1, 8 , Todd J Martinez 4, 9 , Michael Thorwart 2, 3 , R J Dwayne Miller 1, 3, 10
Affiliation  

Singlet fission is a spin-allowed exciton multiplication process in organic semiconductors that converts one spin-singlet exciton to two triplet excitons. It offers the potential to enhance solar energy conversion by circumventing the Shockley-Queisser limit on efficiency. We study the primary steps of singlet fission in a pentacene film by using a combination of TG and 2D electronic spectroscopy complemented by quantum chemical and nonadiabatic dynamics calculations. We show that the coherent vibrational dynamics induces the ultrafast transition from the singlet excited electronic state to the triplet-pair state via a degeneracy of potential energy surfaces, i.e., a multidimensional conical intersection. Significant vibronic coupling of the electronic wave packet to a few key intermolecular rocking modes in the low-frequency region connect the excited singlet and triplet-pair states. Along with high-frequency local vibrations acting as tuning modes, they open a new channel for the ultrafast exciton transfer through the resulting conical intersection.



中文翻译:

分子间的振动介导了超快单峰裂变。

单重态裂变是有机半导体中自旋允许的激子倍增过程,它将一个自旋单态激子转换为两个三重态激子。通过规避肖克利-奎塞尔对效率的限制,它具有增强太阳能转化的潜力。我们通过使用TG和2D电子光谱结合量子化学和非绝热动力学计算,研究并五苯膜中单重态裂变的主要步骤。我们表明,相干的振动动力学通过势能面的退化(即多维圆锥形交点)引起从单重态激发电子态到三重态对态的超快速转变。电子波包与低频区域中一些关键的分子间摇摆模式的显着振动耦合将激发的单重态和三重态对耦合。伴随着高频局部振动作为调谐模式,它们为超快激子传递通过圆锥形相交点开辟了新的渠道。

更新日期:2020-09-20
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