Operation Degradation Influence on InP/ZnSe/ZnS and ZnTeSe/ZnSe/ZnS QD-LEDs

Cadmium-free colloidal quantum dots have been previously reported as promising candidates in quantum dot light-emitting diodes (QD-LEDs) due to their tunable optical properties and quantum confinement effects. With the state-of-art external quantum efficiency of red, green and blue QD-LEDs, light out-coupling theoretical limits have been nearly achieved. However, comparing to the high T95 operational lifetime of red and green QD-LEDs counterparts, blue QD-LEDs perform a much lower operation lifetime. In this work, we probe the operation degradation mechanisms on both InP/ZnSe/ZnS (red) and ZnSe(Te)/ZnSe/ZnS (blue) QD-LEDs from a perspective of nanoscale device morphology and interlayer elemental tracing. A coarsening and thinning phenomenon is observed in both quantum dots and Mg-doped zinc oxide nanoparticle (ZnMgO NP) layers after LT50 aging. Meanwhile, an extra oxygen peak shows up in the InP/ZnSe QD layer after biasing the device. Additionally, our findings indicate that long-time high-dose electron beam irradiation contributes to the coarsening of the ZnMgO NP layer, and the presence of hydrogen significantly accelerates the coarsening process under electron beam exposure. This study reveals the morphological thinning and particle coarsening in the electron transport layer (ETL) and active layer after diode aging, establishing a framework for understanding QD-LED degradation mechanisms during operation.