Enhancement of hole injection using O-2 plasma-treated Ag anode for top-emitting organic light-emitting diodes

Abstract

We report the enhancement of hole injection using AgOx layer between Ag anode and 4,4(')-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl in top-emitting organic light-emitting diode (OLED). The turn-on voltage of OLEDs decreased from 17 to 7 V as Ag changed to AgOx by the surface treatment using O-2 plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased about 0.4 eV by the O-2 plasma treatment. This led to the decrease of the energy barrier for hole injection, reducing the turn-on voltage of OLEDs. (C) 2005 American Institute of Physics.