High‐Performance Tandem quantum‐dot light‐emitting diodes based on bulk‐heterojunction‐like charge‐generation layers

Abstract In this study, the fundamental but previously overlooked factors of charge generation efficiency and light extraction efficiency (LEE) were explored and collaboratively optimized in tandem quantum‐dot light‐emitting diodes (QLEDs). By spontaneously forming a microstructured interface, a bulk heterojunction‐like charge‐generation layer composed of a poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/ZnO bilayer was fabricated and an ideal charge‐generation efficiency surpassing 115% was obtained. The coupling strength of the waveguide mode for the top unit and the plasmon polariton loss for the bottom unit were highly suppressed using precise thickness control, which increased the LEE of the tandem devices. The red tandem QLED achieved an exceptionally low turn‐on voltage for electroluminescence at 4.0 V and an outstanding peak external quantum efficiency of 42.9%. The ultralow turn‐on voltage originated from the sequential electroluminescence turn‐on of the two emissive units of the tandem QLED. Benefiting from its unique electroluminescent features, an easily fabricated optical‐electrical dual anti‐counterfeiting display was built by combining a dichromatic tandem QLED with masking technology. This article is protected by copyright. All rights reserved