Electrochemically engineered NiO_x for high-performance quantum dot light-emitting diodes

Solution-processed nickel oxide (NiO_x) is expected as low-cost alternatives to organic hole injection layers (HILs) in quantum dot light-emitting diodes (QLEDs) for long-term operating stability. However, precisely modulating the energy levels of NiO_x while ensuring alignment with the organic hole transport layers (HTLs) possessing high ionization energies remains challenging. Herein, we demonstrate a post-electrochemical engineering strategy that facilitates precise control of NiO_x work function. This approach enhances hole injection capability by lowering the energy barrier at HIL/HTL interface, thereby suppressing charge accumulation and non-radiative energy loss. The electrochemical engineering strategy significantly enhances hole transport kinetics, yielding a ∼ 80 % improvement in current efficiency and a 4-fold extension of operational lifetime compared to untreated NiO_x-based QLEDs. Our findings demonstrate an electrochemical engineering method for precisely tailoring NiO_x HIL properties, advancing QLEDs efficiency through charge functional layer optimization.