Colloidal quantum dot-based light-emitting diodes (QLEDs) exhibit a high potential of being the next-generation technology of large-scale display and solid-state lighting, thanks to their unique advantages of tunable emission wavelength, narrow emission spectral bandwidth, and low processing cost. A typical QLED device is composed of QD light emitting layer (EML), hole transport layer (HTL), and electron transport layer (ETL). To achieve a high-efficiency QLED, fast electron transport and charge balance are highly desirable. ZnO nanoparticle film has a high carrier mobility and therefore became a good ETL candidate in QLEDs. On the other hand, the high work function of ZnO nanoparticles causes a charge unbalance in the QD/ZnO interface, which leads to limited device efficiency. A good capability of charge balance is then required to overcome the efficiency limitation. In the article, Q. Zhang and coworkers present a method to improve the electron transport and charge balance performance of QLEDs by introducing ZnMgO nanoparticles to the ZnO nanoparticle film as ETL. It is demonstrated that ZnMgO can effectively widen the band gap of ZnO and achieve a charge balance. In this work, a luminance intensity of 22100 cd/cm² and an external quantum efficiency of 13.5% are reported by using the proposed ZnMgO:ZnO-based QLEDs. The research provides a useful pathway for achieving high-performance QLEDs.

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