Preparation and characterization of Ni-indium tin oxide cosputtered thin films for organic light-emitting diode application

The characteristics of organic light-emitting diode (OLED) can be improved by the doping of nickel (Ni) into indium tin oxide (ITO) anode. Ni-doped ITO films were synthesized using Ni and ITO cosputter approach. Film properties, such as surface roughness, optical transmittance, sheet resistivity, and surface work function, independent of Ni-doping level were examined. Results show that the Ni-doped ITO films perform lower surface roughness and higher surface work function without scarifying the optical transmittance after thermal annealing at 300 °C. OLED devices with an Al/tris(8-hydroxyquinoline)aluminum/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'biphenyl-4,4'-diamine/ITO/glass structure were fabricated to investigate the effect of the Ni-doped ITO anode. From the I-V characteristics of the OLED devices, the threshold voltage can be reduced from 12 to 8 V when the Ni atomic concentration is greater than 1.8%.