Superradiance in molecular H aggregates

Direct evidence of superradiance from an organic semiconductor (quaterthiophene) whose molecules are arranged in a H aggregate fashion, is reported. Time resolved photoluminescence measurements show a linear correlation between the radiative lifetime (tau(rad)) of the purely electronic exciton recombination and the inverse of the number (N-C) of the coherently emitting dipoles, i.e., tau(rad)proportional to1/N-C. These data support the recently developed theoretical models describing the optical properties of H aggregates of rodlike molecules with a nonvanishing component of the perpendicular molecular transition dipole moment.