Electrochemically engineered NiO(x) for high-performance quantum dot light-emitting diodes.

Solution-processed nickel oxide (NiO) 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 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 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-based QLEDs. Our findings demonstrate an electrochemical engineering method for precisely tailoring NiO HIL properties, advancing QLEDs efficiency through charge functional layer optimization.