Inorganic hole injection layers for improving the hole injection of quantum dot light-emitting diodes

Quantum dot light-emitting diodes (QLEDs) hold great potential for next-generation displays, offering outstanding efficiency and exceptional color purity. Nevertheless, their performance remains constrained by poor hole injection and device instability. In this study, a bilayer structure of NiO/NiO_x:Mg is proposed for the hole injection layer (HIL) in QLEDs to address these challenges. This bilayer structure enhances the work function, facilitates hole injection, and thereby improves the performance of QLEDs. As a result, the optimized device exhibits nearly twice the current efficiency compared to its NiO-based counterpart, along with an extended T₅₀ lifetime—approximately eight times longer than that of the NiO-based device. Additionally, Mg doping effectively mitigates photoluminescence quenching in quantum dots, and capacitance–voltage analysis, along with other measurements, confirms the reduction of hole injection barriers. These results suggest that employing bilayer HILs significantly improves QLEDs performance, with possible applications in other optoelectronic devices like perovskite solar cells.