ZnSeTe blue top-emitting QLEDs with color saturation near Rec.2020 standards and efficiency over 18.16%

ZnSeTe blue Cd-free quantum dot (QD) has emerged as a promising emitter for display applications due to its nontoxicity, tunable wavelength, and high efficiency. However, ZnSeTe-based quantum-dot light-emitting diodes (QLEDs) usually exhibit unsaturated emissions with broad spectra. Herein, a top-emitting structure, equipped with a transparent indium-zinc-oxide (IZO) top electrode and an IZO phase tuning layer (PTL), is developed to modulate the emission spectra and the efficiency of the devices. Saturated blue emissions with color coordinates beyond Recommendation ITU-R BT.709 (Rec.709) and near Rec.2020 standards are achieved. Moreover, benefiting from the improved outcoupling efficiency and the enhanced charge balance, the top-emitting QLED demonstrates a high external quantum efficiency of 15.14%, which is further improved to 18.16% by capping the devices with SiO₂ nanospheres. Simulation analysis reveals that the surface plasmon polariton (SPP) losses are effectively reduced by applying a 100 nm PTL, leading to an outcoupling efficiency of 41.2% at a wavelength of 478 nm. Due to the simultaneously enhanced color saturation and efficiency, a high chroma efficiency (current efficiency/y coordinate in Commission Internationale de l'Eclairage chart) of 123 is obtained. The developed top-emitting architecture could enable the realization of efficient and saturated QLEDs for wide color gamut high-definition display applications.