聚合物半导体中载流子量子输运的微观、介观尺度贯通模拟研究

High optoelectronic conversion efficiency combined with reduced fabrication costs make solution-processable conjuagated polymer a compelling option for tomorrow’s optoelectronic devices, such as light-emitting diodes, field-effect transistors, and photovoltaic cells. In order to further improve their device performances, a deeper understanding of charge transport properties is of crucial importance. The main goal of this research is to examine charge transport properties in conjugated polymers. In particular, we examine theoretically the influences of temperature, electric field and morphology upon mobility and current-voltage characteristics for neat polymers, via multi-scale simulation which is based on coarse-graining molecular dynamics and reverse-mapping technique and quantum chemical calculation that is based on first-principle methods. Our main theoretical goal is to develop a unified description of quantum nuclear-tunneling mediated charge transport in conjugated polymers that could explain the recent observations. Since the charge transport properties of conjugated polymers are highly dependent on chain conformation and detailed morphology, the quantum description of charge transport, which directly includes the vibration modes and environment contribution of the specific polymer system, is essential. In this study, we examine closely the validity of the Einstein relation and Shockley diode equation by taking the quantum effects into consideration. This research will provide new insight into the polaron transport in conjugated polymers.

载流子输运是聚合物半导体基础研究中的重要课题。研究载流子输运规律，对促进聚合物半导体在太阳能电池、发光二极管和场效应晶体管等领域的应用有重要意义。最新的实验结果已证实聚合物中的载流子传输符合量子跳迁的机制，原有的半经典理论不能完整描述的器件伏安特性。基于这些发现，本项目将利用全新的量子跳迁理论，结合微观、介观尺度贯通的分子动力学模拟开展载流子传输的研究。研究将应用全量子载流子跳迁速率公式，考察聚合物半导体电学性质和微观结构之间的联系，以及半经典微观规律的适用性。研究内容包括分子结构、链构象、微相形貌等因素对载流子迁移率和器件伏安特性的影响，以及电学性质随温度、电场等因素的基本变化规律。研究将发展从第一性原理出发计算聚合物迁移率的理论方法，并选取具有代表性的共轭聚合物进行计算，致力于加深对聚合物半导体中载流子传输的理解，并为高迁移率聚合物半导体设计和器件表征提供重要的理论依据。