Efficient Hole Injection From Indium Tin Oxide in Quantum-Dot Light-Emitting Diodes

Abstract

PEDOT:PSS thin film is commonly used as a hole injection layer (HIL) in quantum-dot light-emitting diodes (QLEDs). However, the realization of QLEDs-based displays remains challenging due to the complex effects of acidic surfaces on device performance. Here, it is demonstrated that in the operation of QLEDs, metal diffusion from electrodes into the QD films can result in exciton quenching. By applying an organic molecule [4-(3,6-dibromo-9H-carbazol-9-yl)butyl]phosphonic acid (2BrCzPA), as a treatment on the ITO, The role of traditional PEDOT:PSS can be replaced. The formation of strong dipoles at the ITO/2BrCzPA self-assembled molecules (SAM) interfaces exhibits excellent hole injection abilities. This method leads to more efficient exciton generation in the QD layer and outstanding operational stability, enabling QLEDs to exhibit superior performance. Specifically, high external quantum efficiencies of 15.28%, 12.63%, and 14.83% are achieved at the brightness of 34 250, 22 640, and 9147 cd m⁻² for the green, blue, and red QLEDs, respectively. This work presents a high-performance ITO/SAM QLED that eliminates the unstable PEDOT:PSS and exhibits better stability, which can promote the practical application of QLED technology in displays and solid-state lighting.