Effects of UV Irradiation and Storage on the Performance of Inverted Red Quantum-Dot Light-Emitting Diodes

Yu Luo,Boon Kar Yap,Pu Wang,Junjie Wang,Junbiao Peng,Chaohuang Mai,Jian Wang

doi:10.3390/nano11061606

Abstract

We report the effects of ultraviolet (UV) irradiation and storage on the performance of ZnO-based inverted quantum-dot light-emitting diodes (QLEDs). The effects of UV irradiation on the electrical properties of ZnO nanoparticles (NPs) were investigated. We demonstrate that the charge balance was enhanced by improving the electron injection. The maximum external quantum efficiency (EQE) and power efficiency (PE) of QLEDs were increased by 26% and 143% after UV irradiation for 15 min. In addition, we investigated the storage stabilities of the inverted QLEDs. During the storage period, the electron current from ZnO gradually decreased, causing a reduction in the device current. However, the QLEDs demonstrated improvements in maximum EQE by 20.7% after two days of storage. Our analysis indicates that the suppression of exciton quenching at the interface of ZnO and quantum dots (QDs) during the storage period could result in the enhancement of EQE. This study provides a comprehension of the generally neglected factors, which could be conducive to the realization of high-efficiency and highly storage-stable practical applications.

Highlights

In the past few years, the performance of quantum-dot light-emitting diodes (QLEDs) has been significantly improved via thorough study of the core/shell structure of quantum dots (QDs) [4,5], the surface ligands of
We investigated the effects of UV irradiation during the encapsulation process on the efficiency and storage stability of ZnO-based inverted QLEDs
The low performance could be attributed to a reduction in ZnO conductivity due to the trace amount of O2 in the glovebox being adsorbed on the surface of ZnO, and in turn capturing the free electrons of ZnO

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Quantum-dot light-emitting diodes (QLEDs) are promising large-area electroluminescent devices used for display and solid-state lighting applications, due to their high efficiency, tunable color, high color purity, and simple yet cost-effective solution processibility [1,2,3]. In the past few years, the performance of QLEDs has been significantly improved via thorough study of the core/shell structure of QDs [4,5], the surface ligands of QDs [6,7], and device structure engineering [8,9]. The QLEDs with high efficiency and long operational lifetime mainly adopt a multilayer hybrid structure with an organic hole injection/transport layer and an inorganic electron injection/transport layer (ZnO or ZnMgO)

Methods

Results

Conclusion