Enhanced Stability of Cd‐Free Quantum Dot Light‐Emitting Diodes via Yttrium Acetate‐Modified ZnMgO: Suppressing Mg Migration

Abstract The operational lifetime of colloidal quantum dot (QD)‐based QD light‐emitting diodes (QLEDs) remains a critical challenge for commercialization in practical applications. This limitation primarily results from non‐radiative recombination processes at the interface between the Mg‐doped ZnO (ZMO) electron transport layer and the QD emissive layer. This study provides direct evidence that Mg ions migrate from the ZMO lattice into the QD layer, leading to device degradation. Hence, a surface‐passivation strategy is implemented by incorporating a thin yttrium acetate layer on the ZMO surface. The proposed approach effectively passivates oxygen vacancies in the ZMO lattice, increases the binding energy of Mg ions, and suppresses their migration, thereby reducing non‐radiative exciton quenching and enhancing radiative exciton recombination. Consequently, QLEDs fabricated with passivated ZMO demonstrate substantially enhanced charge‐induced emission efficiency and a 65.5% increase in operational lifetime at 100 cd/m², improving from 1448 to 2396 h. These findings provide a promising strategy for improving the stability and commercial viability of eco‐friendly InP‐based QLEDs, contributing to advancements in next‐generation display technologies.