Positive Aging‐Free Quantum Dot Light‐Emitting Diodes Enabled by Single‐Source Chloride‐Doped ZnMgO Electron Transport Layers

ABSTRACT Colloidal quantum dot light‐emitting diodes (QD‐LEDs) offer narrowband, color‐pure emission, solution processability, and wavelength tunability for next‐generation displays. However, commercialization is hindered by positive aging—a storage‐driven drift in which device external quantum efficiency (EQE) increases for several days before peaking, reflecting slow interfacial trap passivation in oxide electron‐transport layers (ETLs). This drift delays qualification, complicates calibration, and degrades device‐to‐device uniformity because the as‐fabricated performance does not represent the final state. Here, we suppress positive aging by pre‐stabilizing ZnMgO ETLs via single‐source chloride doping (MgCl ₂ ), which mitigates oxygen vacancy (OV)‐related defect signatures. Time‐dependent X‐ray photoelectron spectroscopy, single‐carrier device measurements, and steady‐state/time‐resolved QD photoluminescence show that undoped ZnMgO undergoes gradual defect passivation during storage, whereas Cl‐doped ZnMgO remains nearly time‐invariant. As a result, devices with Cl‐doped ZnMgO reach peak EQE at day 0 and maintain it during storage, while devices with undoped ZnMgO require several days to reach peak efficiency. In addition, as‐fabricated QD‐LEDs employing Cl‐doped ZnMgO exhibit ≈1.8× higher peak EQE and ≈1.3× longer operational lifetime than undoped controls, with negligible positive aging signatures. This intrinsic ETL stabilization enables day‐0 calibration, improves uniformity and yield, and removes the need for storage‐driven conditioning—identifying single‐source chloride doping as a practical route to robust ZnMgO ETLs for display applications.