Synergy between Inter- and Intramolecular Interactions on Relaxation Pathways of Oligomeric Pentacene Assemblies

Precise control over the couplings between molecules that govern excited-state relaxation processes remains a challenge in organic materials. A primary example of this is in singlet fission, which has the potential to boost photovoltaic efficiencies through exciton multiplication. While detailed solution-phase mechanistic studies of this phenomenon now exist, bridging the gap to practical devices has yet to be realized. We address this issue by showcasing several different ways to steer the excited-state relaxation of new fission-active pentacene and fission-inactive anthracene oligomers, highlighting how the balance of inter- and intramolecular coupling plays a crucial role. We achieve this by engineering specific interactions via supramolecular self-assembly. These interactions promote the uncommon occurrence of strong J-aggregation in acenes. Within the aggregates, intermolecular couplings result in the formation of a strongly bound ¹TT state, which outcompetes the parasitic charge transfer process that dominates in isolated molecules. These findings highlight that balancing intra- and intermolecular interactions offers an effective strategy for regulating the singlet fission process, a critical requirement for advancing future solid-state devices and applications.