大尺寸复杂分子体系中的相干载流子动力学理论及应用

Quantum dynamics theory in complex molecular systems is one of hot topics in theoretical chemistry because the traditional carrier transfer theories meet many challenges, especially in the explanation of mechanism for organic photovoltaic materials and DNA molecules. At present, the well-developed band-like theory and hopping-type model are applicable for researching the coherent transport of carrier and the systems with strong carrier-phonon coupling, respectively. In complex molecular systems, those models cannot be straightforwardly used to their carrier dynamics because of the strong carrier-phonon couplings as well as the coherent property of carrier motions, resulting in that the key factor for controlling the carrier transport mechanism has been controversial. Focusing on this problem, our project will propose the coherent quantum dynamics theory to unify the band-like and hopping-type models and clarify the mechanism of carrier motions. Furthermore, the project will combine the developed model with electronic structure calculations to investigate the carrier dynamics in realistic complex molecular systems, specifically: (1) propose coherent carrier dynamics theory for systems with thousands of molecules and the population satisfying the principle of detailed balance; (2) apply the proposed model, together with electronic structure calculations, to research the energy and charge transfer processes in the concrete light-harvesting systems and DNA molecules; (3) investigate the photo-physical mechanism of organic solar cells in details, such as considering the effect of configurations and possible arrangements in donor and acceptor materials, and try to clarify the present controversy and design the organic photovoltaic devices with high efficiency.

复杂分子体系量子动力学理论的发展和应用一直是学术界研究的热点和难点之一，尤其是近年来有机光伏材料和生物DNA分子中载流子传输机制的争论对该领域的理论方法提出了新挑战。目前发展较成熟的能带理论研究载流子的相干传输，而局域蛙跳模型适用于电声耦合较强的体系，均无法直接应用于同时存在强的电声耦合和载流子相干运动的复杂分子体系。本课题拟针对量子动力学的新挑战，发展统一能带与蛙跳模型的相干载流子动力学理论，并与电子结构计算相结合理论预测真实体系中的载流子行为，找出控制其传输机制的关键因素，具体而言：（1）发展满足精细平衡原理且适用于纳米尺度材料的相干载流子动力学理论；（2）结合电子结构计算，研究具体复杂分子体系（如光捕获体系和DNA分子）中的能量及电荷转移过程；（3）深入探讨有机太阳能电池中给体与受体材料的结构和排列方式等对光电转换效率的影响，尝试澄清当前的争议并对设计高效的有机光伏器件提供理论指导。

本项目按照计划较好地完成了预期目标。针对载流子传输机制的争议，本课题对原创性的含时波包扩散方法进行改进：解决了方法中复数随机力的问题并重新推导记忆效应项得到了新的表达式，改进的方法在数值模拟（与严格量子动力学相比较）和应用（参数范围和体系大小）上均有了明显的提高；将含时波包扩散方法与电子结构计算相结合，研究了具体有机材料（芘基衍生物材料）中的电荷迁移率，给芘基衍生物在有机光伏器件中的应用提供了新的思路；与有机实验课题组合作，应用他们合成的苯基卤代铜配合物和富勒烯衍生物及相应晶体材料制作的光伏器件的实验数据，我们给出理论上的解释并期望设计高效率的有机光伏器件（如由芘基衍生物材料和富勒烯衍生物组成的有机太阳能电池）。本项目的理论研究对自然界光合作用的能量及电荷传递过程、DNA 分子中的载流子动力学及有机光伏器件的光电转换效率进行解释和预测具有一定的影响。在项目支持下共发表学术论文3篇，包括J. Org. Chem. 1 篇，Sensor. Actuat. B-Chem. 1 篇，New J. Chem. 1 篇，共支持3名研究生进行科研工作。