Optimizing Device Efficiency and Lifetime through Positive Ageing in Quantum Dot Light-Emitting Diodes
Ning Li, Yanbing Lv, Lei Wang, Jinjie Li, Yuanqi He, Jinjin Fan, Huanhuan Xing, Huaibin Shen, Xintong Zhang, Lin Song Li
Abstract
As solution-processed hybrid quantum dot light-emitting diodes (QLEDs), they may undergo a positive ageing process to improve their performance. It is highly desirable to investigate the ageing treatment and further use this positive effect to regulate the performance of the device. Under different ageing periods, we analyze how CdSe/Zn x Cd 1– x Se/ZnSe y S 1– y core/shell quantum dot (QD)–ZnMgO interface and possible interface reactions between the QD, ZnMgO, and the Al electrode can affect device performance via positive ageing. The Kelvin probe measurements indicate a reduction in the energy level difference between ZnMgO and Al, leading to a relatively large built-in potential. By simply adjusting the annealing temperature of ZnMgO, the degree of positive ageing can be adjusted to optimize the device performance. By comparing the work function change of ZnMgO at different annealing temperatures, the change of surface electron affinity becomes more obvious, which may affect the degree of positive ageing. With an about 22 times improvement in operational lifetime, the peak external quantum efficiency of aged QLEDs can be optimized from 14.7 to 26.7%. This work presents an entirely new perspective on positive ageing and can serve as an important scientific guideline to further improve device performance.