构建有机光伏材料的电子激发透热态

Rational construction of electronically excited diabatic state of organic photovoltaic material, and accurate evaluation of diabatic coupling are the key steps of describing the photoelectric conversion process, as well the basic questions in the field theoretical chemistry, which make themselves hot topics with high practical significance and very important theoretical value. At the moment, there are still many challenges in the construction of diabatic states of complicated systems. This project will improve the molecular orbital localization method to improve the diabatic basis which is used to describe the diabatic state, and further to generalize a more reasonable way to construct diabatic state. Then we are going to apply the method on the system of practical application in the experiments, and compare the diabatic coupling strengths which are obtained based on the results of various excited state methods. Eventually we could provide guiding suggestions for designing and improving the organic photovoltaic materials. At the same time we are going to optimize the program, such that this method can be easily and widely used in the relevant research areas.

合理构建机光伏材料的电子激发透热态，以及精确计算态间耦合强度是描述其光电转化过程的关键步骤，也是理论化学领域的基本问题，是具有极高现实意义和重要理论价值的热点课题。现阶段理论上对复杂体系的透热态构建仍面临许多挑战。本项目将通过改进分子轨道定域化方法来改良用于描述透热态的透热基，以此来得到更合理的透热态构建方式。然后建立实验中实际应用的体系，比较基于各种激发态计算方法的结果得到的透热态间耦合强度，为设计和改进有机光伏材料提出指导性建议。同时本项目希望通过优化计算程序，将此方法推广至更多相关领域的研究。

相较于现阶段成熟的硅基太阳能电池产业，有机光伏电池则具有可大量溶剂化制备，成本更加低廉，以及兼具柔韧性和环境友好等众多优点，在原理上深入理解有机光伏体系，可对未来材料／器件的选择和设计提供理论指导。目前比较前沿的有机太阳能电池器件均存在一个核心的“给体-受体”结构在产生并传导激子的同时促进激子分离成为电子和空穴，并在工作电压下最终形成电流。整个过程中对激子的产生，传导和分离的最基本（第一性原理）阐述，都需要采用电子结构理论中的透热态理论来描述。本项目通过结合对有机光伏体系的从头算计算，改进了构建近似透热态的理论方法，扩展并优化了程序代码，同时推广了该方法在量子动力学和激发态化学中的应用。.在方法改进方面，我们提出了一个基于前线轨道构型相互作用的模型哈密顿方法，此方法定量的拟合了基于高精度从头算方法（CC2）的聚集体体系的透热态相互作用耦合矩阵，使该方法在保证计算精度的同时大大减少计算量，因此该方法可应用于大型的聚集体体系的计算。我们同时应用透热态分析的方法定量解释了实验中发现的P3HT有序聚集体的π−π堆积间距由于分子掺杂而减少的原因。