有机分子晶体电荷传输的多尺度模拟：转移积分关联效应

There has been recently a growing consensus indicating that the charge-transport properties of organic molecular crystals are significantly impacted by the nonlocal electron-phonon couplings. However, there is currently still a lack of understanding in some peculiar properties and roles of this coupling mechanism and, accordingly, more intensive and detailed investigations in this respect are highly required. In this project, by focusing on the correlations between intermolecular transfer integrals as a result of the nonlocal electron-phonon couplings, we propose to perform a systematic investigation of the impact on the electronic structure and charge-transport properties of organic molecular crystals by employing a multiscale modeling protocol. By considering the thermal disorders stemming from low-frequency molecular vibrations, we will establish two-dimensional models adequately accounting for the transfer-integral correlations relevant to specific materials. The quasiparticle spectra and associated electronic properties will be evaluated by means of the Green's function method in the semiclassical approximation, and the carrier mobility as a function of temperature, Fermi energy, and carrier concentration will be calculated by several complementary methods, such as the Boltzmann theory, the linear-response theory, and the mixed quantum-classical dynamics approach. The calculated results will be compared with the available experimental findings. These proposed studies are expected to be very important in deepening our understanding of the roles played by the nonlocal electron-phonon couplings in the charge-transport processes of organic molecular crystals as well as in boosting the development of more sophisticated modeling methods in this field.

人们近来逐渐认识到非局域电子-声子耦合对有机分子晶体的电荷传输性质具有重要影响，然而目前对这种耦合机制一些独特的性质和作用依然缺乏了解，迫切需要更加深入细致的研究。本项目拟重点关注非局域电子-声子耦合对分子间转移积分所产生的关联效应，采用多尺度模拟手段系统地研究该效应对有机分子晶体电子结构与电荷传输性质的影响。具体包括：通过考虑低频分子振动所引起的热无序，结合具体材料建立有效描述转移积分关联效应的二维模型；在半经典近似下利用格林函数方法计算体系的准粒子能谱及其相关电子性质，通过玻尔兹曼理论、线性响应理论和混合量子-经典动力学等多种优势互补的方法计算载流子迁移率随温度、费米能以及载流子浓度的变化关系；计算结果将与相关实验数据进行比较。该项研究对于深入理解非局域电子-声子耦合在有机分子晶体电荷传输过程中的作用以及推动相关理论模拟方法的发展都将具有重要意义。

非局域电子-声子耦合对有机半导体电荷传输性质具有重要影响。本项目围绕非局域电子-声子耦合引起的转移积分关联效应，系统研究了有机半导体特别是有机分子晶体的电荷传输性质及其机理，取得的研究进展如下：.（1）系统研究了转移积分关联效应对有机分子晶体电子结构和电荷传输性质的影响。揭示了二维模型下非局域电子-声子耦合对称性与转移积分关联效应之间的对应关系，研究了转移积分关联效应对准粒子能谱和载流子迁移率影响的规律和物理机制。.（2）发展了描述有机半导体电荷传输性质的多尺度模拟方法。通过第一性原理密度泛函理论、紧束缚模型、蒙特卡洛模拟相结合，详细研究了典型有机分子晶体中的电荷传输性质和机理。.（3）有机半导体自旋相关电荷传输和激子动力学性质。基于对非局域电子-声子耦合的理解以及结合相关多尺度模拟手段，研究了有机半导体中自旋极化子的动力学演化性质，以及给体/受体界面处激子的超快解离过程。.这些研究对全面理解有机半导体中的电荷传输性质、机理以及相关多尺度模拟方法的发展具有积极的指导意义。