Enhanced passivation characteristics in OLEDs by modification of aluminum cathodes using Ar+ ion beam

Organic light-emitting diodes (OLEDs) with aluminum cathodes prepared by the ion-beam-assisted deposition (IBAD) have a longer lifetime than thermally evaporated one. The electroluminescent features were examined to compare the rate of degradation in the devices with thermally evaporated Al cathodes and ion-beam-assisted Al cathodes. The dense and highly packed Al cathode effectively prevents the permeation of H2O and O-2 through pinhole defects, which results in retarding dark spot growth. Employing thin Al buffer layer diminished Ar+ ion-induced damages in phenyl-substituted poly-p-phenylene-vinylene (Ph-PPVs) and limited permeation against H2O and O-2. The interface between Al and Ph-PPV may be modified in IBAD case, even though buffered Al layer was deposited to 30 nm by thermal evaporation prior to Ar+ ion beam irradiation. It is believed that the buffered Al film cannot screen the Ar+ ions or Al atoms wholly due to the existence of pinholes or non-deposited regions among the columnar structures. (c) 2005 Published by Elsevier Ltd.