Rhodium-oxide-coated indium tin oxide for enhancement of hole injection in organic light emitting diodes

Abstract

The authors report the enhancement of hole injection using an RhOx layer between indium tin oxide anodes and 4, 4′ -bis[N-(1-naphtyl)- N -phenyl-amino]biphenyl in organic light-emitting diodes (OLEDs). The operation voltage of OLEDs at 700 cdm2 decreased from 13 to 10 V as the Rh layer changed to RhOx by surface treatment using O2 plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased by 0.2 eV as the Rh layer transformed into RhOx. Thus, the hole injection energy barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs.