Solution-Processed Double-Junction Quantum-Dot Light-Emitting Diodes with an EQE of Over 40%

Abstract

Despite the rapid development in quantum-dot light-emitting diodes (QD-LEDs) with a single junction, it remains a big challenge to make tandem QD-LEDs with high performance. Here, we report solution-processed double-junction tandem QD-LEDs with a high external quantum efficiency of 42.2% and a high current efficiency of 183.3 cd A–1, which are comparable to those of the best vacuum-deposited tandem organic LEDs. Such high-efficiency devices are achieved by interface engineering of fully optimized single light-emitting units, which improves carriers’ transport/injection balance and suppresses exciton quenching induced by ZnO, and design of an effective interconnecting layer consisting of poly­(4-butylphenyl-diphenylamine) (poly-TPD)-mixed poly­(9-vinylcarbazole) (PVK)/poly­(3,4-ethylenedioxythiophene):polystyrene sulfonate/polyethylenimine ethoxylated-modified ZnO.

Technology progress on quantum dot light-emitting diodes for next-generation displays

“…Even though most of the literature reporting the highest performance are using Cd-based QD materials, [27][28][29][30] there is an urgent need for heavy-metal free QDs as Cd-based QDs are not environmentally friendly and restricted by the regulation of hazardous substances (RoHS). In this regard, ongoing researches on Cd-free QDs are summarised in the following section.…”

“…4 (c), which is used to improve the efficiency of QD-LED by vertically stacking several QD-LED units with a transparent interconnecting layer (ICL). 30,[43][44][45][46][47] Each of the auxiliary layers such as HIL, HTL and ETL is characterised by the layer thickness, the carrier mobilities, the energy band alignments with the neighbouring layers as well as the interfacial morphologies. It is crucial to develop the layer structure of the device architecture and to optimize the materials and the processes of all layers to achieve high electrooptical performance.…”

Efficiency Enhancement of All‐Solution‐Processed Inverted‐Structure Green Quantum Dot Light‐Emitting Diodes Via Partial Ligand Exchange with Thiophenol Derivatives Having Negative Dipole Moment

“…Inverted‐structure QLEDs are advantageous because they are suitable for integrated circuits of n‐type metal oxide transistors having low processing costs . The performance of all‐solution‐processed inverted QLEDs has been improved by introducing various interface and charge transport (CT) layers …”

Quantum‐Dot Light‐Emitting Diodes for Outdoor Displays with High Stability at High Brightness

“…Since the first demonstration of QD‐based light‐emitting diodes (QLEDs) in 1994, device performance has been steadily improved to meet the requirements for low brightness displays (indoor displays). The luminance, external quantum efficiency (EQE), and even operation lifetime of QLEDs is now comparable to that of state‐of‐the‐art organic LEDs (OLEDs) . However, the short operation lifetime under high brightness still limits the application of QLEDs in outdoor displays and lighting.…”