Boosting the Efficiency of NiO_x-Based Perovskite Light-Emitting Diodes by Interface Engineering

Nickel oxide (NiOx) is a promising hole-transporting material for perovskite light-emitting diodes (PeLEDs) because of its low cost, excellent stability, and simple fabrication process. However, the electroluminescence efficiencies of NiOx-based PeLEDs are greatly limited by inefficient hole injection and exciton quenching at the NiOx-perovskite interfaces. Here, a novel interfacial engineering method with sodium dodecyl sulfate-oxygen plasma (SDS-OP) is demonstrated to simultaneously overcome the aforementioned issues. Experimental results reveal that a short OP treatment on the top of the SDS-coated NiOx significantly deepens the NiOx work function (from 4.23 to 4.85 eV) because of the formation of a large surface dipole, allowing for efficient hole injection. Moreover, the SDS-OP layer passivates the electronic surface trap states of perovskite films and suppresses the exciton quenching by NiOx. These improvements inhibit the nonradiative decays at the NiOx-perovskite interface. As a result, the external quantum efficiency of CsPbBr3 LEDs is increased from 0.052 to 2.5%; that of FAPbBr3 nanocrystals LEDs is increased from 5.6 to 7.6%.