Over 30% Efficient Non‐Vacuum Quantum‐Dot Light‐Emitting Diode with a Bi‐Layer High‐Precision Patternable EGaIn Top Electrode

Abstract Although functional layers of quantum dot light‐emitting diodes (QLEDs) can be fabricated by solution processing, expensive vacuum deposition techniques are still required to form the top electrode, which hinders the commercialization of QLEDs. Here, efficient non‐vacuum QLEDs with a bi‐layer eutectic gallium‐indium (EGaIn) top electrode consisting of a viscous EGaIn layer and a liquid EGaIn interface layer is demonstrated. Due to the low flowable properties of the viscous EGaIn, bi‐layer EGaIn electrodes can be patterned directly by laser ablation with a narrow line width of 30 µm. As a result, non‐vacuum QLEDs with an excellent external quantum efficiency (EQE) of 30.49% are obtained, and by using poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate as the bottom electrode, fully solution‐processed (including electrodes) non‐vacuum QLEDs with an EQE exceeding 24% are further achieved. Moreover, by precisely patterning the bi‐layer EGaIn electrode, the non‐vacuum QLED with high‐precision emission patterns (line width: 30 µm) can also be realized. To the best of the knowledge, these efficiencies are the highest ever reported for the non‐vacuum QLEDs. It is believed that the demonstrated high‐efficiency non‐vacuum QLEDs, with high‐precision patternable electrodes and low manufacturing cost, will advance the commercialization of QLEDs in displays.