High-Performance Quantum-Dot Light-Emitting Diodes Using NiO_x Hole-Injection Layers with a High and Stable Work Function

Solution-processed oxide thin films are actively pursued as hole-injection layers (HILs) in quantum-dot light-emitting diodes (QLEDs), aiming to improve operational stability. However, device performance is largely limited by inefficient hole injection at the interfaces of the oxide HILs and high-ionization-potential organic hole-transporting layers. Solution-processed NiO_x films with a high and stable work function of ≈5.7 eV achieved by a simple and facile surface-modification strategy are presented. QLEDs based on the surface-modified NiO_x HILs show driving voltages of 2.1 and 3.3 V to reach 1000 and 10 000 cd m⁻², respectively, both of which are the lowest among all solution-processed LEDs and vacuum-deposited OLEDs. The device exhibits a T₉₅ operational lifetime of ≈2500 h at an initial brightness of 1000 cd m⁻², meeting the commercialization requirements for display applications. The results highlight the potential of solution-processed oxide HILs for achieving efficient-driven and long-lifetime QLEDs.