Tris-(8-hydroxyquinoline) aluminium (Alq(3)) and N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) were thermally deposited on both Si- and indium tin oxide (ITO)-coated glass substrates. Ultraviolet photoelectron spectroscopy studies indicated that the electronic structures of the organic/Si systems were obviously changed upon annealing at 90 degreesC. However, the electronic structures of the organic/ITO systems were not changed until annealing at or above 150 degreesC. X-ray photoelectron spectroscopy results indicated that organic/Si interfacial reaction readily took place at elevated temperatures, However, no reaction was observed at the organic/ITO interfaces as the annealing temperature increased. (C) 2002 Elsevier Science B.V. All rights reserved.