Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA.
J Chem Phys. 2013 Mar 21;138(11):114102. doi: 10.1063/1.4794425.
Singlet fission, a spin-allowed energy transfer process generating two triplet excitons from one singlet exciton, has the potential to dramatically increase the efficiency of organic solar cells. However, the dynamical mechanism of this phenomenon is not fully understood and a complete, microscopic theory of singlet fission is lacking. In this work, we assemble the components of a comprehensive microscopic theory of singlet fission that connects excited state quantum chemistry calculations with finite-temperature quantum relaxation theory. We elaborate on the distinction between localized diabatic and delocalized exciton bases for the interpretation of singlet fission experiments in both the time and frequency domains. We discuss various approximations to the exact density matrix dynamics and propose Redfield theory as an ideal compromise between speed and accuracy for the detailed investigation of singlet fission in dimers, clusters, and crystals. Investigations of small model systems based on parameters typical of singlet fission demonstrate the numerical accuracy and practical utility of this approach.
单重态裂变，一种自旋允许的能量转移过程，可将一个单重激发态转化为两个三重激发态，有潜力极大地提高有机太阳能电池的效率。然而，这一现象的动力学机制尚未完全理解，缺乏完整的、微观的单重态裂变理论。在这项工作中，我们组装了一个全面的微观单重态裂变理论的组成部分，该理论将激发态量子化学计算与有限温度量子弛豫理论联系起来。我们详细阐述了局域化和离域化激子基之间的区别，以解释在时间和频率域中单重态裂变实验。我们讨论了精确密度矩阵动力学的各种近似，并提出了 Redfield 理论，作为在二聚体、团簇和晶体中详细研究单重态裂变的速度和准确性之间的理想折衷。基于单重态裂变典型参数的小模型系统的研究表明了这种方法的数值准确性和实际实用性。
