Substrate dependence of thermal effect on organic light-emitting films

Tris-(8-hydroxyquinoline) aluminium (Alq3) 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 °C. However, the electronic structures of the organic/ITO systems were not changed until annealing at or above 150 °C. 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.