Abstract
An environment-friendly inverted indium phosphide red quantum dot light-emitting diode (InP QLED) was fabricated using Mg-doped zinc oxide (ZnMgO) as the electron transport layer (ETL). The effects of ZnMgO ETL on the performance of InP QLED were investigated. X-ray diffraction (XRD) analysis indicated that ZnMgO film has an amorphous structure, which is similar to zinc oxide (ZnO) film. Comparison of morphology between ZnO film and ZnMgO film demonstrated that Mg-doped ZnO film remains a high-quality surface (root mean square roughness: 0.86 nm) as smooth as ZnO film. The optical band gap and ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the conduction band of ZnO shifts to a more matched position with InP quantum dot after Mg-doping, resulting in the decrease in turn-on voltage from 2.51 to 2.32 V. In addition, the ratio of irradiation recombination of QLED increases from 7% to 25% using ZnMgO ETL, which can be attributed to reduction in trap state by introducing Mg ions into ZnO lattices. As a result, ZnMgO is a promising material to enhance the performance of inverted InP QLED. This work suggests that ZnMgO has the potential to improve the performance of QLED, which consists of the ITO/ETL/InP QDs/TCTA/MoO3/Al, and Mg-doping strategy is an efficient route to directionally regulate ZnO conduction bands.
Highlights
In the past decade, quantum dot (QD) has been considered a promising next-generation light-emitting material due to its outstanding photo-electrical properties [1,2,3] and great solution-processing ability [4,5]
We verified that introduction of ZnMgO electron transport layer (ETL) can still improve the performance of Indium phosphide (InP) QLED devices with an inverted structure
We found that Mg-doping can broaden the band gap of zinc oxide (ZnO), which is mainly attributed to the conduction band minimum (CBM) shift upward
Summary
Quantum dot (QD) has been considered a promising next-generation light-emitting material due to its outstanding photo-electrical properties [1,2,3] and great solution-processing ability [4,5]. A multi-layer device structure that includes an electron injection/transport layer (EIL/ETL), emitting layer (EML), hole injection/transport layer (HIL/HTL), and electrode layer is required to achieve high-performance InP-based QLED, which helps to balance the injection of carriers and reduce the barrier of interface [1,19,20,21]. Among these layers, the ETL plays an important role in electron injection efficiency, exciton dissociation, and hole blocking [22,23,24].
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