Passivation properties of OLEDs with aluminum cathodes prepared by ion-beam-assisted deposition process

A long-lived organic light emitting diode (OLED) was fabricated using a dense aluminum cathode prepared by the ion-beam-assisted deposition (IBAD) process. We investigated the passivation properties of ion-beam-assisted and thermal evaporation-induced aluminum cathodes mounted on Ph-PPV. The dense and highly packed Al cathode effectively prevents the permeation of H₂O and O₂ through pinhole defects, which results in retarding dark spot growth. Employing thin Al buffer layer diminished Ar⁺ ion-induced damages in Ph-PPV 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.