Optimizing Device Efficiency and Lifetime through Positive Ageing in Quantum Dot Light-Emitting Diodes

As solution-processed hybrid quantum dot light-emittingdiodes(QLEDs), they may undergo a positive ageing process to improve theirperformance. It is highly desirable to investigate the ageing treatmentand further use this positive effect to regulate the performance ofthe device. Under different ageing periods, we analyze how CdSe/Zn x Cd1-x Se/ZnSe y S1-y core/shellquantum dot (QD)-ZnMgO interface and possible interface reactionsbetween the QD, ZnMgO, and the Al electrode can affect device performancevia positive ageing. The Kelvin probe measurements indicate a reductionin the energy level difference between ZnMgO and Al, leading to arelatively large built-in potential. By simply adjusting the annealingtemperature of ZnMgO, the degree of positive ageing can be adjustedto optimize the device performance. By comparing the work functionchange of ZnMgO at different annealing temperatures, the change ofsurface electron affinity becomes more obvious, which may affect thedegree of positive ageing. With an about 22 times improvement in operationallifetime, the peak external quantum efficiency of aged QLEDs can beoptimized from 14.7 to 26.7%. This work presents an entirely new perspectiveon positive ageing and can serve as an important scientific guidelineto further improve device performance.

Automated summary

This study investigates the positive ageing process of solution-processed hybrid quantum dot light-emitting diodes (QLEDs) and demonstrates how it can be used to improve device performance. By adjusting the annealing temperature, the degree of positive ageing can be optimized.