Study on the interaction between Ag and tris(8-hydroxyquinoline) aluminum using x-ray photoelectron spectroscopy

In the present study, model organic light-emitting diodes (OLEDs) with a st ructure of Ag/tris(8-hydroxyquinoline) aluminum (Alq(3))/indium tin oxide ( ITO) were fabricated using vacuum evaporation and analyzed using an x-ray p hotoelectron spectroscopy (XPS) depth profile technique. Diffusion of Ag in to the Alq(3) layer was clearly observed. Applying a positive electron fiel d enhanced the diffusion. Compared with pure Ag, the binding energy of diff used Ag 3d(5/2) at the interface increased slightly, and the contribution o f Ag to the valence-band spectra also was changed across the depth, implyin g a weak interaction between diffused Ag and the hydroxyquinoline ligands. Copyright (C) 2001 John Wiley & Sons, Ltd.