Effects of aluminum cathodes prepared by ion-beam-assisted deposition in organic light-emitting devices

Abstract

We have fabricated highly stable organic electroluminescent devices based on spin-coated soluble phenyl-substituted poly- p -phenylene-vinylene (Ph-PPVs) thin films. The electrical properties of aluminumcathode, prepared by ion-beam-assisted deposition, on Ph-PPV have been investigated and compared to those prepared by thermal evaporation. Although energetic particles of Al assisted by Ar + ion may damage the organic material, I – V – L characteristics are improved by evaporating a thin Albuffer layer prior to ion-beam-assisted deposition. In addition, a dense Alcathode inhibits the permeation of H 2 O and O 2 into Ph-PPV film by suppressing pinhole defects, and thus retards dark spot growth. This may be deduced from highly packed structure of Alcathode with smaller contact resistance between Al and Ph-PPV. The lifetime of an organic light-emitting device has been extended by dense Alfilm through an ion-beam-assisted deposition process.