有机电荷转移复合物中超交换电荷传输性质的理论研究

Recently，excellent charge transport properties have been found experimently for alternate stacking charge transfer complexes, many effort have been made to investigate its charge transport properties. However, the transport mechanism is unclear. If based on localized charge model, charge transport will not be allowed, since two molecules is so far away between them that carrier can not cross middle bridge molecule to the other molecule, which is opposite to experimental results. In fact, super-exchange charge transport can be achieved through the middle of bridge molecule. In this project, we will develop a self-consistent interative method to calculate the super-exchange electronic coupling. we will investigate quantum effect of local electron-phonon coupling(mainly from intramolecular vibration with high frequency),and the effect of thermal fluctuation of superexchange electronic coupling, which is induced by nonlocal electron-phonon coupling(from intermolecular vibration with low frequency) on charge transport. Through the implementation of this project,we can deeply understand superexchange charge transport mechanism, try to find the relationship of superexchange effect with electronic structure of donor and acceptor molecules, so as to design ambipolar organic semiconductors with high mobility.

最近,实验发现某些给受体交替堆积的电荷转移复合物具有优异的双极性传输性能,引起人们的广泛关注。但是其电荷传输机制尚不清楚。如果基于目前的局域电荷模型，同种分子之间相距很远，载流子无法越过中间的桥分子实现电荷传输，与实验结果相违背。实际上，中间桥分子作为媒介通过超交换机制对电荷传输起着至关重要的作用。因此，本项目针对复杂给受体电荷转移复合物，拟通过自洽迭代Larsson方法计算分子间超交换电子耦合；结合局域电声子耦合(分子内高频振动)的量子效应、非局域电声子耦合(分子间的低频振动)所导致的转移积分的热涨落研究其对电荷传输的影响。通过本项目的实施，深刻理解给受体交替堆积电荷转移复合物中的超交换电荷传输机制，探讨超交换效应与给受体分子电子结构的关系，从而达到设计双极性高迁移率的有机半导体材料的目标。

本项目通过超交换耦合计算方法的发展，从分子层面上理解给受体交替堆积电荷转移复合物中的超交换电荷传输机制，提供普适的计算电荷转移复合物超交换电子耦合的理论方法。从而为理解有机半导体材料的电荷传输极性，电荷迁移率的理论模拟奠定基础。同时，基于局域电荷传输模型，我们研究了烷基链取代，剪切应力对分子间堆积以及电子耦合的影响。通过考虑原子核振动的量子效应，我们研究了同位素效应对分子内振动（电声子耦合）的影响。基于以上方法的发展， 我们建立一套从电荷传输参数到材料的电荷传输迁移率模拟的计算流程，为理性设计高迁移率有机半导体材料提供有力的理论指导，圆满完成本项目的预期目标。