Using tunneling junction to enhance hole-injection in organic light-emitting diodes

Abstract

We demonstrate enhanced hole-injection and lower driving voltage in vacuum-deposited organic light-emitting diodes (OLEDs) with a novel tunneling junction composed of the Mg:Alq(3)/WO3 layer. The device, ITO/Mg:Alq(3)/WO3/NPB/Alq(3)/LiFAl achieved one of the lowest driving voltages of 5.8 V at 20mA/cm(2) for conventional small molecule OLEDs. We propose the laminated Mg:Alq(3)/WO3/NPB functions as a Fowler Nordheim tunneling junction, which can improve hole-injection. It was found to also prolong device lifetime under dc driving, that is comparable to the best reported for the Alq(3) emitter.