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 structure of Ag/tris(8-hydroxyquinoline) aluminum (Alq(3))/indium tin oxide (ITO) were fabricated using vacuum evaporation and analyzed using an x-ray photoelectron spectroscopy (XPS) depth profile technique. Diffusion of Ag into the Alq(3) layer was clearly observed. Applying a positive electron field enhanced the diffusion. Compared with pure Ag, the binding energy of diffused Ag 3d(5/2) at the interface increased slightly, and the contribution of Ag to the valence-band spectra also was changed across the depth, implying a weak interaction between diffused Ag and the hydroxyquinoline ligands. Copyright (C) 2001 John Wiley & Sons, Ltd.