Transparent conducting aluminum-doped zinc oxide thin films for organic light-emitting devices

Abstract

Aluminum-doped zinc oxide (AZO) thin films (∼3000 Å) with low electrical resistivity and high optical transparency have been grown by pulsed-laser deposition on glass substrates without a postdeposition anneal. Films were deposited at substrate temperatures ranging from room temperature to 400 °C in O2 partial pressures ranging from 0.1 to 50 mTorr. For 3000-Å-thick AZO films grown at room temperature in an oxygen pressure of 5 mTorr, the electrical resistivity was 8.7×10−4 Ω cm and the average optical transmittance was 86% in the visible range (400–700 nm). For 3000-Å-thick AZO films deposited at 200 °C in 5 mTorr of oxygen, the resistivity was 3.8×10−4 Ω cm and the average optical transmittance in the visible range was 91%. AZO films grown at 200 °C were used as an anode contact for organic light-emitting diodes. The external quantum efficiency measured from these devices was about 0.3% at a current density of 100 A/m2.