XPS study of interfaces in a two-layer light-emitting diode made from PPV and Na®on with ionically exchanged Ru(bpy)3 2‡

X-ray photoelectron spectroscopy (XPS) was used to investigate the interfacial chemistries occurring in a prototype twolayer polymer light-emitting diode that had been fabricated from PPV and Na®on with ion-exchanged Ru(bpy)3 2‡. Magnesium and indium tin oxide (ITO) were used as electrodes, and XPS observations were made as the different layers were added sequentially. Speci®cally, Mg was deposited on a layer of Na®on with incorporated Ru(bpy)3 2‡, and this was itself deposited on PPV-coated ITO. The morphology of Na®on, which is dictated by the strongly hydrophilic and hydrophobic groups that compose it, is indicated to rearrange with the incorporation of Ru(bpy)3 2‡; this rearrangement appears reinforced when a thin ®lm is deposited on PPV. The Mg deposition results in substantial changes in XPS spectra, in part due to a direct interaction with the ¯uorocarbon backbone of Na®on. # 2001 Elsevier Science B.V. All rights reserved.