Advances in understanding quantum dot light-emitting diodes

Quantum dot light-emitting diodes (QD-LEDs) are attractive for display and lighting applications owing to their high colour rendering index, their low-cost solution processability and their ability to achieve simultaneous high brightness and near-unity internal quantum efficiency at low voltages. Since 1994, tremendous progress has been made in improving the external quantum efficiency and lifetimes of QD-LEDs, and there has been growing understanding of the operational and degradation mechanisms. However, there are still critical problems that remain to be clarified, such as the origin of positive ageing and the role of zinc oxide nanoparticles in achieving high performance. In this Review, we analyse the key factors influencing voltage, internal quantum and photon out-coupling efficiencies of QD-LEDs. We point out the issues related to cadmium-free quantum dots and short-lifetime blue QD-LEDs. Finally, we clarify the challenges and summarize the latest progress in commercializing QD-LEDs. Quantum dot light-emitting diodes (QD-LEDs) are attractive for display and lighting applications. Precise understanding of their operational and degradation mechanisms will greatly promote the commercialization of this technology. This Review summarizes the key understanding and remaining challenges of QD-LEDs.