Efficient ZnSeTe‐Based Blue Quantum‐Dot Light‐Emitting Diodes via Phosphine Oxide Dual Passivation of Quantum Dots and ZnMgO Interfaces

Abstract ZnSeTe‐based blue quantum dots light‐emitting diodes (QD‐LEDs), characterized by their eco‐friendly nature and high‐performance potential, have emerged as promising cadmium‐free candidates for next‐generation lighting and display technologies. However, the performance of these devices is significantly hindered by the abundance of defects on the surfaces of quantum dots (QDs) and ZnMgO (ZMO), leading to serious exciton quenching. Here, a dual passivation strategy is presented that simultaneously modifies the QDs film and ZMO nanoparticles through the integration of electronegative phosphine oxide (P═O)‐functionalized organic molecules. The results show that the electrons in the P═O functional group are bind to surface defects in QDs, effectively reducing trap states and increasing the population of excitons. Additionally, these electrons interact with oxygen vacancies in ZMO, mitigating exciton quenching caused by vacancy defects in ZMO. This approach simultaneously passivates anionic vacancies on QDs surfaces and hydroxyl‐related defects in ZMO, thereby suppressing non‐radiative recombination pathways and optimizing charge transport dynamics. The optimized QD‐LEDs achieve a peak external quantum efficiency (EQE) of 18.02% and a luminance of 44037 cd m⁻ 2 at 5 V. Furthermore, the operational lifetime (T50) at an initial luminance of 100 cd m⁻ 2 is extended sixfold to 618 h, highlighting remarkable stability. The results indicate that defect passivation engineering is crucial for the fabrication of efficient and stable ZnSeTe‐based blue QLEDs.