Theoretical Investigation of Intramolecular Singlet Fission

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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.