Photoluminescence (PL) dynamics of localized excitons in a strongly coupled 40 A˚/40 A˚ GaAs/Al0.2Ga0.8/As superlattice under an electric field along the growth direction is reported. At zero field, a delayed PL formation due to the relaxation of dark excitons into radiative states is observed. With increasing field, both the PL decay time and the PL amplitude are strongly reduced. A rate equation analysis of the measured PL transients gives evidence that the field‐induced dissociation of nonradiative excitons is important. ©1995 American Institute of Physics.