Further understanding of the temporal behavior and degradation mechanisms of QLEDs is urgently demanded from both technical and fundamental perspectives. At present, a major obstacle to the practical applications of QLEDs lies in their inferior operational lifetimes. These efforts have led to red, green, and blue QLEDs with high external quantum efficiencies (EQE: >20%), low turn-on voltages, and high brightness 14, 15, 22, 23, 24, 25. Recent years have witnessed substantial advances in the material chemistry of QDs 9, 10, 11, 12, 13, 14, 15, metal-oxide electron-transport layers (ETLs) 16, 17, 18, 19, and organic hole-transport layers (HTLs) for QLEDs 20, 21, 22. Quantum-dot light-emitting diodes (QLEDs) have emerged as cost-effective and high-performance electroluminescent (EL) devices for next-generation display and solid-state lighting technologies 6, 7, 8. Similar content being viewed by othersĬolloidal semiconductor quantum dots (QDs), such as II–VI QDs, III–V QDs, and metal-halide perovskite QDs, feature tunable bandgaps, narrowband emission, high photoluminescent quantum yields (PLQYs), and excellent solution processibility 1, 2, 3, 4, 5. Our work provides new insights into the degradation of red quantum-dot light-emitting diodes and has far-reaching implications for the design of charge-injection interfaces in solution-processed light-emitting diodes. The results indicate that the operation-induced efficiency increase results from the degradation of electron-injection capability at the electron-transport layer/cathode interface, which in turn leads to gradually improved charge balance. Furthermore, we carried out selective peel-off-and-rebuild experiments and depth-profiling analyses to pinpoint the critical degradation site and reveal the underlying microscopic mechanism. Various in-situ/operando characterizations were performed to investigate the evolutions of charge dynamics during the efficiency elevation, and the alterations in electric potential landscapes in the active devices. Here, we show that quantum-dot light-emitting diodes may exhibit an anomalous degradation pattern characterized by a continuous increase in electroluminescent efficiency upon electrical stressing, which deviates from the typical decrease in electroluminescent efficiency observed in other light-emitting diodes. Understanding the operational degradation mechanisms of quantum-dot light-emitting diodes is crucial for their practical applications. Quantum-dot light-emitting diodes promise a new generation of high-performance and solution-processed electroluminescent light sources.
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