Theoretical Investigation of Intramolecular Singlet Fission

单线态裂变（SF）的光物理过程，涉及到分子材料中的单线态激子分裂成两个三重态激子，最近受到了极大的关注，特别是因为它有可能提高太阳能电池的效率，超过Shockley-Queisser极限。虽然传统上大多数关于这一主题的研究都是针对有机晶体中的分子间SF，但最近在溶液中化学键合的双显色或多显色体系中的分子内SF已成为该领域的焦点。分子内单线态裂变的过程为在分子水平上理解顺丰提供了一个通用的场景，并为可溶液处理的基于顺丰的光伏器件开辟了道路。该项目的长期目标是获得对分子内SF机制的详细和全面的了解。为此，sf活性分子体系的光致动力学将采用高水平从头算电子结构计算、量子动力学方法和混合量子经典方法的组合来模拟和分析。要解决的具体方面包括直接和介导途径在多激子态形成中的重要性，振动耦合的影响以及自旋偶极子-偶极子耦合引起的自旋混合的作用。此外，将研究从SF活性分子到不同受体物种的电子转移动力学，这一过程对SF在太阳能电池中的潜在应用至关重要。

The photophysical process of singlet fission (SF), which involves the splitting of a singlet exciton into two triplet excitons in molecular materials, has received great attention recently, in particular due to its potential to increase the efficiency of solar cells beyond the Shockley–Queisser limit. While traditionally most research on this topic has addressed intermolecular SF in organic crystals, more recently intramolecular SF in chemically bonded bichromophoric or multichromophoric systems in solution has become a focus of the field. The process of intramolecular singlet fission provides a versatile scenario for understanding SF at the molecular level and opens the way to solution-processable SF-based photovoltaic devices. The long-term goal of the project is to obtain a detailed and comprehensive understanding of the mechanisms of intramolecular SF. To this end, the photoinduced dynamics of SF-active molecular systems will be simulated and analyzed using a combination of high-level ab initio electronic structure calculations, quantum dynamical methods, and mixed quantum-classical approaches. Specific aspects to be addressed include the importance of direct and mediated pathways in the formation of multiexciton states, the influence of vibronic coupling as well as the role of spin-mixing induced by spin dipole-dipole coupling. Furthermore, the dynamics of electron transfer from SF-active molecules to different acceptor species will be investigated, a process which is crucial for potential application of SF in solar cells.