The Transient Localization Scenario for Charge Transport in Crystalline Organic Materials
The Transient Localization Scenario for Charge Transport in Crystalline Organic Materials
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DOI：
10.1002/adfm.201502386
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发表时间：
2016-04-12
影响因子：
19
通讯作者：
Ciuchi, Sergio
中科院分区：
文献类型：
--
作者：
Fratini, Simone;Mayou, Didier;Ciuchi, Sergio
晶体有机半导体中的电荷输运本质上受到大分子热运动的限制，大的热分子运动是分子间弱相互作用的直接结果。这导致了一种称为瞬时局域化的原始输运机制，它共享局域电子系统和巡回电子系统的特征。在简要回顾了对理论提出挑战的实验观察之后，我们集中讨论了一个通常研究的模型，该模型描述了电荷载流子与分子间振动的相互作用。我们介绍了过去应用于这个问题的不同的理论方法，然后转向更现代的方法，这些方法能够捕捉到令人困惑的实验观测的起源的关键微观现象，即电子波函数在比典型分子运动更短的时间尺度上的量子局域化。我们特别描述了一个驰豫时间近似，它阐明了动态分子运动引起的瞬时局域化与静态无序实现的Anderson局域化之间的关系，并允许我们设计策略来改善实际化合物的迁移率。简要讨论了瞬变本地化方案与其他类型系统的相关性。
Charge transport in crystalline organic semiconductors is intrinsically limited by the presence of large thermal molecular motions, which are a direct consequence of the weak van der Waals intermolecular interactions. These lead to an original regime of transport called transient localization, sharing features of both localized and itinerant electron systems. After a brief review of experimental observations that pose a challenge to the theory, we concentrate on a commonly studied model which describes the interaction of the charge carriers with intermolecular vibrations. We present different theoretical approaches that have been applied to the problem in the past, and then turn to more modern approaches that are able to capture the key microscopic phenomenon at the origin of the puzzling experimental observations, i.e., the quantum localization of the electronic wavefunction at timescales shorter than the typical molecular motions. We describe in particular a relaxation time approximation which clarifi es how the transient localization due to dynamical molecular motions relates to the Anderson localization realized for static disorder, and allows us to devise strategies to improve the mobility of actual compounds. The relevance of the transient localization scenario to other classes of systems is briefl y discussed.