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Origin of Positive Aging in Quantum‐Dot Light‐Emitting Diodes
Advanced Science ( IF 14.3 ) Pub Date : 2018-07-03 , DOI: 10.1002/advs.201800549 Qiang Su 1 , Yizhe Sun 1 , Heng Zhang 1 , Shuming Chen 1
Advanced Science ( IF 14.3 ) Pub Date : 2018-07-03 , DOI: 10.1002/advs.201800549 Qiang Su 1 , Yizhe Sun 1 , Heng Zhang 1 , Shuming Chen 1
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The phenomenon of positive aging, i.e., efficiency increased with time, is observed in quantum‐dot light‐emitting diodes (QLEDs). For example, the external quantum efficiency (EQE) of blue QLEDs is significantly improved from 4.93% to 12.97% after storage for 8 d. The origin of such positive aging is thoroughly investigated. The finding indicates that the interfacial reaction between Al cathode and ZnMgO electron transport layer accounts for such improvement. During shelf‐aging, the Al slowly reacts with the oxygen from ZnMgO, and consequently, leads to the formation of AlOx and the production of oxygen vacancies in ZnMgO. The AlOx interlayer reduces the electron injection barrier while the oxygen vacancies increase the conductivity of ZnMgO and, as a result, the electron injection is effectively enhanced. Moreover, the AlOx can effectively suppress the quenching of excitons by metal electrode. Due to the enhancement of electron injection and suppression of exciton quenching, the aged blue, green, and red QLEDs exhibit a 2.6‐, 1.3‐, and 1.25‐fold efficiency improvement, respectively. The studies disclose the origin of positive aging and provide a new insight into the exciton quenching mechanisms, which would be useful for further constructing efficient QLED devices.
中文翻译：
量子点发光二极管正老化的起源
在量子点发光二极管（QLED）中观察到正老化现象，即效率随时间增加。例如，蓝色QLED的外量子效率（EQE）在储存8天后从4.93%显着提高到12.97%。这种积极老化的根源已得到彻底研究。研究结果表明，Al 阴极和 ZnMgO 电子传输层之间的界面反应是这种改善的原因。在搁置老化过程中，Al 与 ZnMgO 中的氧缓慢反应，从而导致 AlO x的形成并在 ZnMgO 中产生氧空位。 AlO x中间层降低了电子注入势垒，而氧空位增加了ZnMgO的电导率，从而有效增强了电子注入。此外，AlO x可以有效抑制金属电极对激子的猝灭。由于电子注入的增强和激子猝灭的抑制，老化的蓝色、绿色和红色 QLED 的效率分别提高了 2.6 倍、1.3 倍和 1.25 倍。这些研究揭示了正老化的起源，并为激子猝灭机制提供了新的见解，这将有助于进一步构建高效的 QLED 器件。
更新日期：2018-07-03
中文翻译：
量子点发光二极管正老化的起源
在量子点发光二极管（QLED）中观察到正老化现象，即效率随时间增加。例如，蓝色QLED的外量子效率（EQE）在储存8天后从4.93%显着提高到12.97%。这种积极老化的根源已得到彻底研究。研究结果表明，Al 阴极和 ZnMgO 电子传输层之间的界面反应是这种改善的原因。在搁置老化过程中，Al 与 ZnMgO 中的氧缓慢反应，从而导致 AlO x的形成并在 ZnMgO 中产生氧空位。 AlO x中间层降低了电子注入势垒，而氧空位增加了ZnMgO的电导率，从而有效增强了电子注入。此外，AlO x可以有效抑制金属电极对激子的猝灭。由于电子注入的增强和激子猝灭的抑制，老化的蓝色、绿色和红色 QLED 的效率分别提高了 2.6 倍、1.3 倍和 1.25 倍。这些研究揭示了正老化的起源，并为激子猝灭机制提供了新的见解，这将有助于进一步构建高效的 QLED 器件。
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