Phenyl-Substituted Acene Derivatives as Candidates for Intermolecular Singlet Fission

A significant increase in the solar conversion efficiency of organic photovoltaic (OPV) devices could be achieved by harnessing singlet fission (SF), the down-conversion of one singlet exciton into two triplet excitons. Acene and acene derivatives, such as pentacene, tetracene, and rubrene, exhibit intermolecular SF in the solid state. Here, we systematically examine a family of crystalline phenyl-substituted tetracene and pentacene derivatives to elucidate the effect of phenyl substitutions. Many-body perturbation theory (MBPT) in the GW approximation and the Bethe-Salpeter equation (BSE) is used to describe the electronic and excitonic properties of isolated molecules and molecular crystals. We show that the properties of acene derivatives may be modified by changing the number of phenyl side groups, which affects the single molecule properties, as well as the crystal packing. This produces a versatile family of acene derivatives with tunable excitonic properties, some of which are attractive candidates for intermolecular SF.