Re‐Thinking Dimer Design Principles with Indolonaphthyridine Intramolecular Singlet Fission

Abstract

AbstractSinglet fission is a phenomenon that could significantly improve the efficiency of photovoltaic devices. Indolonaphthyridine thiophene (INDT) is a photostable singlet fission material that could potentially be utilised in singlet fission‐based photovoltaic devices. This study investigates the intramolecular singlet fission (i‐SF) mechanism of INDT dimers linked via para‐phenyl, meta‐phenyl and fluorene bridging groups. Using ultra‐fast spectroscopy the highest rate of singlet fission is found in the para‐phenyl linked dimer. Quantum calculations show the para‐phenyl linker encourages enhanced monomer electronic coupling. Increased rates of singlet fission were also observed in the higher polarity o‐dichlorobenzene, relative to toluene, indicating that charge‐transfer states have a role in mediating the process. The mechanistic picture of polarisable singlet fission materials, such as INDT, extends beyond the traditional mechanistic landscape.