Defect management in NiMgO-based hole transport materials for efficient quantum dot electroluminescence devices

Colloidal quantum dot-based light-emitting diodes (QD-LEDs) show great promise for next-generation augmented reality (AR) and virtual reality (VR) displays, which demand ultra-high brightness exceeding 10,000 nits. However, conventional QD-LEDs with organic hole transport layers (HTLs) suffer from thermal instability at high brightness. This work explores defect management in NiMgO nanocrystal (NC)-based HTLs for efficient, stable all-inorganic QD-LEDs. MgO-alloyed NiMgO NCs offer a wide band gap and suitable hole mobility. However, it was found that nickel vacancies (VNi) and surface-bound NiOOH introduce undesired mid-gap states causing exciton quenching and charge imbalance. We mitigated these issues by passivating VNi with Mg(OH)2 and removing NiOOH via acid treatment. These optimizations led to a peak external quantum efficiency over 15%, advancing all-inorganic QD-LEDs for AR/VR applications.