ZnO/ITO anode for organic electro-luminescence devices

A bilayer is used as an anode electrode for organic electroluminescent devices. The bilayer consist of an ultrathjn ZnO layer adjacent to an hole-transporting layer and an Indium tin oxide(ITO) outerlayer. We tried to bring low the barrier between the devices as deposited ZnO films on ITO substrates. We fabricated the organic EL structure consisted of Al as cathode, $Al_{2}O_{3}$ as electro transport layer, Alq3 as luminously layer, triphenyl diamine(TPD) as hole transport layer and ZnO(l nm )/ITO(l50 nm) as anode. The result of this experiment was not good compared with the case of using ITO, Nevertheless, at this structure we obtained the lowest turn-on voltage as the value of 19 V and the good brightness (6200 $cd/m^{2}$) of the emission light from the devices. Then the quantum efficiency was to be 1.0%.