High-performance phosphorescent organic light-emitting diodes prepared using an amorphous indium zinc oxide anode film grown by box cathode sputtering

The preparation and characteristics of amorphous indium zinc oxide (a-IZO) anode films grown using a plasma damage-free box cathode sputtering (BCS) technique for use in phosphorescent organic light-emitting diodes (OLEDs) is described. The electrical, optical, structural, and surface properties of the a-IZO anode, which was prepared by BCS at room temperature, were comparable to those of commercial ITO anode films. In addition, the work function of the ozone-treated a-IZO anode (5.23 +/- 0.01 eV) was much higher than that of an ozone-treated commercial ITO anode (4.95 +/- 0.01 eV). Due to high work function and transmittance of the BCS-grown a-IZO anode, Ir(ppy)(3)-doped phosphorescent OLED prepared on the BCS-grown a-IZO, anode films showed identical or better electrical and optical properties than OLEDs prepared on a commercial ITO anode film. In particular, both the quantum efficiency (16.3%) and power efficiency (40.7 lm/W) of the Ir(ppy)(3)-doped phosphorescent OLED fabricated on the amorphous IZO anode film was much higher than the quantum efficiency (12.4%) and power efficiency (30.1 lm/W) of an OLED with a commercial ITO anode. This indicates that a-IZO anode prepared by BCS technique affords OILED performance that rivals or exceeds that of devices fabrication with commercial ITO anode, even though it was prepared at room temperature. (C) 2008 Elsevier B.V. All rights reserved.