Highly stable organic electroluminescent devices based on spin-coated poly-p-phenylene-vynylene (PPV) thin films have been achieved. We investigated the electrical properties of ion beam assisted aluminum cathode contacting PPV compared that of thermal evaporation. Energetic particles of Al assisted by Ar+ ion increase the contact area between Al and PPV minimizing contact resistance. In addition, dense Al cathode inhibits the permeation of H2O and O-2 through pinhole defects, which results in retarding dark spot growth. It is believed that the lifetime of organic light-emitting diode (OLED) device was enhanced effectively by ion beam assisted deposition process resulting from dense Al structure. (C) 2004 Elsevier B.V. All rights reserved.