Use of anodes with tunable work function for improving organic light-emitting diode performance

•The Fermi level of AZO films was controlled by introducing different reactive gases during deposition process. The maximum tunable work function was 1.44eV.•The AZO anode stacked with high-work-function AZO films, similar to hole transport buffer layers, had a low turn-on voltage of 2.89V.•The luminance efficiency and power efficiency were 5.01% and 6.1% greater than those of tin-doped indium oxide anodes used in OLEDs. The effect of reactive gases—oxygen and hydrogen—on the tunable work function of Al-doped ZnO (AZO) films was studied. An increase in the work function with an increase in the oxygen flow rate was mainly interpreted as reflecting a decrease in the carrier concentration, which was attributed to the filling of oxygen vacancies. However, a decrease in the carrier concentration would result in the resistivity increasing sharply. This article presents a new concept for improving the performance of organic light-emitting diodes (OLEDs) through easy and effective hole injection from a multilayer AZO anode to the organic layer. A bilayer AZO film prepared using a tunable work function technique was used to modify the surface of AZO anodes and to ensure that the anodes had low resistivity. The AZO anode stacked with high-work-function AZO films, similar to hole transport buffer layers, had a low turn-on voltage of 2.89V, and its luminance efficiency and power efficiency were 5.01% and 6.1% greater than those of tin-doped indium oxide anodes used in OLEDs.