Direct Evidence of\nExcessive Charge-Carrier-Induced\nDegradation in InP Quantum-Dot Light-Emitting Diodes

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