Efficient and bright phosphorescent organic light-emitting diodes adopting MoO3/PEDOT:PSS as dual hole injection layers

Abstract

It has been demonstrated that high efficiency and brightness can be achieved in phosphorescent organic light-emitting diodes (PHOLEDs) by using molybdenum oxide (MoO3)/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) as dual hole injection layers (HILs) on indium tin oxide (ITO) substrate. The dual HILs were simply fabricated by spin-coating PEDOT:PSS solution on a thin MoO3 layer deposited by vacuum thermal evaporation. This work reveals that PEDOT:PSS coating on MoO3 resulted in a smoother surface, simultaneously MoO3 lamella prevented acid corrosion of PEDOT:PSS on ITO. Meanwhile, with the insertion of PEDOT:PSS and MoO3 as HILs between anode and hole transporting layer (HTL), the energy barrier has been reduced and gave rise to effective hole injection. OLEDs with dual HILs resulted in the maximum current efficiency (CE) of 61.3 cd A[Formula: see text] and maximum luminance of 112200 cd cm[Formula: see text], which showed a superior performance compared to those devices with single HIL of PEDOT:PSS or MoO3. Our results proved the composition of PEDOT:PSS and MoO3 as HILs were beneficial for high performance OLEDs.