It has been claimed that the variation of currentIwith voltageVin an organic light emitting diode (LED), based on either metal chelate complexes or conducting polymers, is explained by shallow traps that trap carriers propagating in the conduction or valence band. However, because these are disordered materials all states are localized. We show that it is possible to fit the dependence ofIonVand on film thickness without explicitly introducing traps, but taking their effect into account by including the mobility variation with the electric field that arises from the distribution in energy of the localized levels. ©1998 American Institute of Physics.