Regular Tandem Quantum Dot Light-Emitting Diodes with over 51% External Quantum Efficiency for Next-Generation...

Despite excellent efficiency and stability achieved in regular single-unit quantum dot light-emitting diodes (QLEDs), regular tandem QLEDs still suffer from limited device performance, lagging far behind the inverted tandem QLEDs. Here, novel regular tandem QLEDs are demonstrated with an ultrathin (≈4 nm) indium tin oxide (ITO) charge generation layer (CGL). Through systematic optimization of charge injection balance and light out-coupling efficiency, the resulting tandem QLEDs can exhibit a record-breaking EQE of 51.2%, an exceptional T₉₅ lifetime of ≈31383 h (at 1000 cd m^-2), and an ultralow turn-on voltage of 2.8 V, which represent the highest performance metrics reported to date for regular tandem QLEDs. Thanks to the fast response of this tandem device (≈4.8 µs), the first-ever fabricated 8 × 8 passive-matrix displays can present flicker-free images with either fixed color or dynamically transitioning colors at a stable brightness, demonstrating that the achievable color display capability and driving scheme of QLED displays can be expanded by using the tandem architecture. It is believed the results will significantly promote the development of regular tandem QLEDs, which will lead to unprecedented improvements in device efficiency and stability, accelerating their application in next-generation displays and lighting.