Transparent conducting films and their influence on the performance of organic LEDs

Tin-doped indium-oxide (ITO) and Al-doped zinc oxide (AZO) films were fabri cated by reactive evaporation and rf magnetron sputtering. The average opti cal transmittance (lambda: 400-800 nm) reached 95% and the sheet resistance was as low as 30 Omega/square. Organic light-emitting devices (LEDs) were fabricated with ITO and AZO transparent films as anode and poly (1,4-phenyl ene vinylene) (PPV) or tris(8-hydroxyquinoline) aluminum (Alq(3)) as lumine scence layer. EL and PL spectra, current-voltage and brightness-voltage dat a were analyzed. It is revealed that the turn-on voltage of the devices was less than 20 V and the carrier injection was consistent with the tunneling theory. Degradation of current with time at a given external voltage was o btained and discussed. (C) 2001 Elsevier Science B.V. All rights reserved.