FRET‐Enhanced Singlet Fission in Pentacene Derivatives

Abstract Conversion of solar energy with high quantum efficiencies is a key challenge in energy technologies. Excitation energy transfer (EET) mechanisms, such as Förster resonance energy transfer (FRET), play a crucial role in facilitating minimal energy loss in biological light‐harvesting systems by directing excitation energy to conversion centers. Inspired by this, it is shown that singlet fission (SF) sensitizers are multi‐exciton generation centers, to which surrounding molecules funnel excitation energy via FRET. The impact of such EET on SF is investigated using two structurally distinct yet optically similar pentacene derivatives: a stability‐enhanced “Geländer” pentacene, and the well‐studied TIPS‐pentacene. Transient absorption spectroscopy reveals a R ⁻⁶ dependence of the SF rate on molecular separation R in binary acene:polymethylmetacrylate thin film blends, which is typical for FRET. Optimizing FRET is a promising direction for future improvements in light harvesting using SF materials, inspired by natural light‐harvesting complexes.