Tonami Takayoshi, Miyamoto Hajime, Nakano Masayoshi, Kishi Ryohei, Kitagawa Yasutaka
Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Research Center for Solar Energy Chemistry (RCSEC), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
J Phys Chem A. 2023 Mar 2;127(8):1883-1893. doi: 10.1021/acs.jpca.2c08864. Epub 2023 Feb 17.
Singlet fission (SF) occurs as a result of complex excited state relaxation dynamics in molecular aggregates, where a singlet exciton (FE) state is converted into a double-triplet exciton (TT) state through the interactions with several other degrees of freedom, such as nuclear motions. In this study, we combined quantum dynamics simulation based on the quantum master equation approach with all-atom-based classical molecular mechanics/molecular dynamics to examine the thermal structural fluctuation (i.e., static disorder) effects of intermolecular configuration on SF in pentacene crystal models. In particular, we considered two types of static-disordered models, in which excited states are assumed to interact with nuclear motions of intermolecular modes in the classical mechanical/statistical manner. We found that the introduction of static disorder effects leads to a faster decay of coherence between the FE and charge transfer (CT) states in the early stage of SF, contributing to the accelerations of several FE → TT relaxation pathways. Such acceleration in these models is shown to be attributed to fluctuations in the energies and electronic coupling of the CT states based on relative relaxation factor analysis. The present study is expected to contribute to further development of bottom-up materials design for efficient SF in condensed phases where the exitonic system interacts with nuclear motions in various coupling strengths.
单重态裂变（SF）是分子聚集体中复杂的激发态弛豫动力学的结果，其中单重态激子（FE）态通过与其他几个自由度（如核运动）的相互作用转化为双三重态激子（TT）态。在本研究中，我们将基于量子主方程方法的量子动力学模拟与基于全原子的经典分子力学/分子动力学相结合，以研究并五苯晶体模型中分子间构型的热结构涨落（即静态无序）对SF的影响。具体而言，我们考虑了两种类型的静态无序模型，其中假设激发态以经典力学/统计方式与分子间模式的核运动相互作用。我们发现，引入静态无序效应会导致SF早期FE与电荷转移（CT）态之间的相干性更快衰减，从而促进了几种FE→TT弛豫途径。基于相对弛豫因子分析，这些模型中的这种加速归因于CT态的能量和电子耦合的涨落。本研究有望为凝聚相中高效SF的自下而上材料设计的进一步发展做出贡献，在凝聚相中，激子系统以各种耦合强度与核运动相互作用。
