High-efficiency transparent organic light-emitting diode with one thin layer of nickel oxide on a transparent anode for see-through-display application

Work functions of different species of metal oxide have been investigated. The work function of nickel oxide was found to reach about 5.4 eV, much higher than those of other metal species and indium tin oxide (ITO). A transparent organic light-emitting diode using a thin oxidation of nickel film on ITO as an anode and a thin MgAg layer as a cathode has been fabricated. Device performance was found to improve greatly due to efficient hole injection from nickel oxide; moreover, the top-emitting intensity was nearly same as the bottom-emitting intensity of the device. The current efficiencies of the bottom and top emissions reached about 4.1 and 3.2 cd A(-1), respectively.