The ‘‘analysis of microelectronic and photonic structures’’ (amps) transport‐simulation computer program has been used to show that a distinction can be made between the effects of light‐induced bulk and interfacial degradation in hydrogenated amorphous silicon (a‐Si:H)p‐i‐ndetector and solar cell structures. Using reverse bias leakage (dark) currents,ampssimulations show that, forpandnlayers that do not allow significant injection of electrons and holes into the intrinsic layer of thep‐i‐nstructure, a light‐induced increase in the density of interfacial states will result in significantly different changes in the voltage behavior of the reverse bias dark currents than will a corresponding increase in the density of bulk defect states. This communication demonstrates that a careful study of the reverse bias dark currents can provide an excellent means of determining if light soaking ofa‐Si:Hp‐i‐ndevices results in bulk degradation, interfacial degradation, or both.