Low driving voltage indium–tin oxide/Al–Ni–Cu–La anode electrodes for top-emission organic light-emitting diodes

We have developed indium–tin oxide (ITO)/Al–Ni–Cu–La anode electrodes for cost-effective large top-emission organic light-emitting diode (OLED) displays. By combining alkaline cleaning with thermal annealing, the driving voltage of the OLED devices containing Al–Ni–Cu–La thin films was effectively reduced, becoming comparable to that for conventional Ag alloy thin films. Cross-sectional transmission electron microscopy (XTEM) observation revealed that the grains in the Al matrix and the precipitates on the Al–Ni–Cu–La surface were small, resulting in a low driving voltage and a high optical reflectivity. The Al–Ni–Cu–La thin films overcome the oxidation issues that cause an increase in contact resistance due to the formation of AlO x between the Al alloy and the ITO thin films, and could replace conventional anode electrodes having an ITO/Ag/ITO structure.