Improving blue quantum dot light-emitting diodes by a lithium fluoride interfacial layer

Abstract

Unlike green and red quantum dot light-emitting diodes (QLEDs), electron injection is not sufficient for blue QLEDs due to a higher potential barrier at the quantum dot (QD)/ZnO interface. In this work, a lithium fluoride (LiF) interlayer is inserted between ZnO and the quantum dot layer to improve the efficiency and stability of blue QLEDs. The LiF interfacial layer facilitates electron injection into QDs through the electron tunneling effect and suppresses the exciton quenching at the QD/ZnO interface. As a result, the blue QLED devices show the maximum external quantum efficiency and current efficiency of 9.8% and 7.9 cd A−1, respectively, which are 1.45 times and 1.39 times, respectively, higher than those of control devices. The operational lifetime of devices is also improved by two times. Our works indicate that interface engineering is an effective method for high efficiency and stable blue QLEDs.