Boosting External Quantum Efficiency of Blue Perovskite QLEDs Exceeding 23% by Trifluoroacetate Passivation and Mixed Hole Transportation Design.

Perovskite quantum dot-based light-emitting diodes (QLEDs) have been considered a promising display technology due to their wide color gamut for authentic color expression. Currently, the external quantum efficiency (EQE) for state-of-the-art blue perovskite QLEDs is about 15%, which still lags behind its green and red counterparts (>25%) and blue film-based LEDs. Here, we present blue perovskite QLEDs that achieve an EQE of 23.5% at 490 nm, to our best knowledge, which is the highest value reported among blue perovskite-based LED fields. This impressive efficiency is achieved through a combination of quantum dot (QD) passivation and optimal device design. First, the blue mixed halide perovskite CsPbCl 3-x Br x QDs passivated by fluorocarboxylic acid exhibit excellent exciton recombination behavior with a photoluminescence quantum yield (PLQY) of 84% due to reducing uncoordinated Pb surface defects. Furthermore, we design the device by introducing a mixed hole-transport layer (M-HTL) to increase hole injection and transportation capacity and improve carrier balance. We further find that M-HTL could decrease carrier leakage and increase radiative recombination in the device, evidenced by the visual electroluminescence spectrum at 2.0 V. Our work breaks through the EQE gap of 20% for blue perovskite-based QLEDs and significantly promotes their commercialization process. This article is protected by copyright. All rights reserved.