Constructing all-solution-processed green phosphorescent organic light-emitting diodes based on zinc sulfide QDs as an electron injection layer

Abstract

We have demonstrated an all-solution-processed multi-layer green phosphorescent organic light-emitting diodes(OLEDs) using zinc sulfide quantum dots (ZnS QDs) based electron injection layer (EIL) in the conventional device structure. The ZnS QDs EIL with proper work function offers efficient electron injection and retains the solvent resistance to the adjacent electron transportation layer. By inserting of a poly-ethyleneimine(PEI) interlayer between the emitting layer and electron transportation layer, solvent can be prevented from permeating through the emissive layers beneath and no additional injection barrier is formed. Thereby, the all-solution-processed OLED with a ZnS QDs EIL exhibits a highest current efficiency of 12.5 cd A−1 based on the PVK: Ir(ppy)3 emitter, achieving a 27.6% improvement in comparison to the reference without a ZnS QDs EIL. Our results provide a facile approach for the development of all-solution-processed OLEDs.