Ultralow Roll-Off Quantum Dot Light-Emitting Diodes Using Engineered Carrier Injection Layer.

Quantum dot light-emitting diodes (QLED) have attracted extensive attention due to their high color purity, solution-processability, and high brightness. Due to extensive efforts, the external quantum efficiency (EQE) of QLED has approached the theoretical limit. However, because of the efficiency roll-off, the high EQE can only be achieved at relatively low luminance, hindering their application in high-brightness devices such as near-to-eye displays and lighting applications. Here, we report an ultralow roll-off QLEDs that is achieved by simultaneously blocking electron leakage and enhancing the hole injection, thereby shifting the recombination zone back to the emitting quantum dots (QDs) layer. These devices maintain EQE over 20.6% up to 1000 mA·cm -2 current density, dropping only by ∼5% from the peak EQE of 21.6%, which is the highest value ever reported for the bottom-emitting red QLEDs. Furthermore, the maximum luminance of the optimal device reached 320,000 cd·m -2 , 2.7 times higher than the control device (L max : 128,000 cd·m -2 ). We also demonstrated a passive matrix QLED display panel with high brightness based on the optimized device structure. The proposed approach advances the potential of QLEDs to operate efficiently in high-brightness scenarios. This article is protected by copyright. All rights reserved.