Triplet dynamics in pentacene crystals: applications to fission-sensitized photovoltaics

The decay and transport of triplet excitons photogenerated via singlet exciton fission in polycrystalline and single-crystalline pentacene is reported. Using transient absorption spectroscopy, we find evidence for diffusion-mediated triplet-triplet annihilation. We estimate monomolecular lifetimes, bimolecular annihilation rate constants, and triplet exciton diffusion lengths. We discuss these results in the context of current solar cell device architectures.