Emerging Design Principles for Enhanced Solar Energy Utilization with Singlet Fission

Singlet fission (SF), the generation of two triplet excitons per the absorption of one photon, is a promising strategy for increasing the efficiency of solar cells beyond the theoretical Shockley–Queisser limit of 34%. Upon photon absorption by a SF molecule, the initially created singlet excited state (S1) interacts with a neighboring chromophore and is first transformed into a triplet pair (TT), which can be subsequently separated into independent triplet excitons (2T1). These independent triplet excitons can be harvested through triplet charge extraction or triplet energy transfer to an acceptor. Research on SF systems has revealed rates and efficiencies of triplet formation and triplet pair decorrelation that are strongly dependent on interchromophore coupling, which is dictated by molecular structure and the resulting geometrical arrangement of chromophores adopted in covalent (e.g., dimers) and noncovalent (e.g., films and crystals) systems. Incorporation of SF materials into realistic device archit...