Organic light-emitting diodes with AZO films as electrodes

Aluminum-doped zinc oxide (AZO) films were prepared by r.f. magnetron sputtering. Organic light-emitting diodes (OLEDs) with AZO/N,N′-diphenyl-N,N′-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD)/tris(8-hydroxyquinoline)aluminum (Alq3)/Al configuration were fabricated. The electroluminescence and current–voltage (I–V) characteristics of the devices were studied and compared with those of tin-doped indium oxide (ITO) devices fabricated under the same conditions. The stability of both AZO/Alq3 and ITO/Alq3 interface was investigated with X-ray photoelectric spectrum (XPS). It was found that zinc or indium would diffuse into Alq3 layer but the diffusive extent of zinc was lower than that of indium.