Direct Evidence of Excessive Charge-Carrier-Induced Degradation in InP Quantum-Dot Light-Emitting Diodes

The limited operational lifetime of quantum-dot light-emitting diodes (QLEDs) poses a critical obstacle that must be addressed before their practical application. Specifically, cadmium-free InP-based QLEDs, which are environmentally benign, experience significant operational degradation due to challenges in charge-carrier confinement stemming from the composition of InP quantum dots (QDs). This study investigates the operational degradation of InP QLEDs and provides direct evidence of the degradation process. To facilitate degradation studies, a double-emission structure was designed. We employed transient electroluminescence and photoluminescence for nondestructive analysis of charge-carrier dynamics during device degradation. The time-resolved emission sequence revealed changes in carrier mobility within the QD layer as devices degraded. Furthermore, prolonged exposure of QDs to the charge-carrier population hindered their radiative recombination. Our observations indicate clear evidence of QLED degradation, characterized by ligand detachment from the QD surface and deterioration of the hole-transporting material due to excessive electrons. This comprehensive analysis of degradation mechanisms in InP QLEDs lays the groundwork for improving operational stability and longevity, serving as a benchmark for future research and development in the field of nanocrystal-based electroluminescent devices.