This work reports a physical model that relates charge transport to the exciton formation rate in organic electroluminescent device, The model assumes ideal charge density profiles and the existence of an "optimal" charge separation for excitons to be formed, This alloy's the exciton formation rate to be dependent on the charge density profiles as well as parameters linked to the exciton formation process. Field dependent effect enters into this model through a "localization" parameter, which is related to the carrier mobility. When the model is applied to the ITO/ 00Pc/NPB/Alq(3)/Mg system, we have found it possible to address a number of observations not fully explained previously. (C) 2002 Elsevier Science Ltd. All rialits reserved.