Mg-Incorporated Nickel Oxide Hole Injection Layer for Stable and Efficient Quantum Dot Light-Emitting Diodes

High-quality hole injection layers (HILs) are essential for efficient and stable quantum dot light-emitting diodes (QLEDs). While NiO_x is a stable alternative to the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HIL, its low hole injection limits its practical application. This work enhances NiO_x hole injection efficiency by combining Mg alloying to deepen work function (5.49 eV vs 5.20 eV) with O₃ treatment to boost conductivity while suppressing traps. Using sol-gel synthesized Mg-alloyed NiO_x nanoparticles followed by O₃ treatment via atomic layer deposition, the resulting QLEDs achieve peak efficiencies of 17.85 cd A^-1 and 11.23 lm W^-1, representing 54% and 171% improvements over NiO_x-based QLEDs (11.56 cd A^-1, 4.15 lm W^-1). Operational stability significantly improves, with a T₅₀ lifetime of 272 h (L₀ = 1000 cd m^-2), over 2.2-fold that of NiO_x-based QLEDs (84 h). This methodology provides a viable pathway to develop a NiO_x HIL for advancing stable and high-efficiency QLEDs.