Highly stable Al-doped ZnO transparent conductors using an oxidized ultrathin metal capping layer at its percolation thickness

Metal capping layer can be used to enhance the physical properties of thin films. We propose a transparent conductor structure made of Al-doped ZnO (AZO) and an oxidized Ni capping layer, the latter with a thickness in proximity of its percolation threshold (2.5 nm). The capping layer inhibits the penetration of oxygen and water into the AZO’s grain boundaries thus significantly increasing the stability of the combined structure, as it is shown by its resistance in damp heat testing at 95 °C and 95% humidity. In addition, the oxidized Ni capping layer increases the performance of AZO transparent anodes in organic light emitting diodes by producing efficiencies as high as those of indium-tin-oxide based devices.