High-Efficiency, Large-Area, Flexible Top-Emitting Quantum-Dot Light-Emitting Diode

Abstract

Flexible displays are essential to provide information in real time for human–machine interactions. As a next-generation display technology, quantum-dot light-emitting diodes (QLEDs) are potentially serving as key components for flexible displays. However, it is still challenging for QLEDs to simultaneously achieve flexibility, large-scale production, and high efficiencies. To this end, a strategy is proposed here by combining a top-emitting structure, optical microcavity optimization, and large-scale film preparation. A top-emitting microcavity with semitransparent and reflective metals is designed to achieve flexibility, efficient carrier injection, and high light extraction efficiency. Precision manufacturing of large-area QLEDs with the designed top-emitting microcavity is achieved by combining surfactant-assisted blade-coating and vacuum thermal evaporation processes. With this strategy, a large-area flexible QLED with an active area of 400 mm2 and a maximum external quantum efficiency of 21.8% is developed. This strategy provides a promising approach toward the development of flexible displays with the demonstration of a 1.3 in. passive-matrix flexible QLED display of 19 by 19 pixels.

Flexible Quantum Dot Light‐Emitting Device for Emerging Multifunctional and Smart Applications

“…[225] Recently, Yu et al reported large-area top-emitting QLEDs (Figure 6e) prepared by combining surfactant-assisted blade-coating and vacuum evaporation processes. [229] Nonionic surfactant Tween 60 is introduced to achieve blade-coated ZnO and QD films on the Al-coated substrate. A flexible QLED with an active area of 400 mm 2 and EQE of 21.8% were fabricated with this approach (Figure 6f) as well as a 1.3-inch passive-matrix top-emitting QLED display by using patterned Ag cathode (Figure 6g,h).…”

“…f) Images with a pattern, g) 19 × 19 passivematrix flexible top-emitting QLED display array, and h) EL image of Arabic numbers. (e-h) Reproduced with permission [229]. Copyright 2022, American Chemical Society.…”

Progress in the Development of Active-Matrix Quantum-Dot Light-Emitting Diodes Driven by Non-Si Thin-Film Transistors

“…No substrate in the optical path may considerably improve the light outcoupling efficiency [ 89 , 90 , 91 ]. Also, a microcavity effect between two metallic electrodes can be utilized to tune the peak wavelength and enhance the color purity [ 92 , 93 , 94 , 95 ]. However, intense light emission in the normal direction results in a distorted angular profile of the Lambertian distribution, which may cause a poor viewing angle in display devices.…”

Highly Efficient Top‐Emitting Quantum‐Dot Light‐Emitting Diodes with Record‐Breaking External Quantum Efficiency of over 44.5%

“…Moreover, in terms of displays, the TE structure is more favorable because it allows a higher display aperture ratio and enables the devices to be integrated with opaque substrates such as Si wafers. [18][19][20][21] Optically, the QLEDs can be modeled as a cavity, in which light reflect back and forth by the bottom and the top electrodes. It is well known that there are two types of optical interferences in microcavity, namely wide-angle interference and multiple-beam interference.…”