Quantum dot light-emitting diodes (QD-LEDs) are highly promising light sources with excellent figures of merit. Although great successes have been achieved in elevating some key parameters to an ideal level, QD-LEDs with superior performance in all aspects have rarely been realized. Herein, by exploring crystalline structure-dependent electronic properties, it is shown that QD-LEDs can simultaneously exhibit high external quantum efficiency, roll-off-free under high brightness, and dramatically improved operational stability. This improved performance stems from the crystal phase engineering of QD. Reduced structure symmetry in the wurtzite phase introduces an unneglectable internal crystal field compared with the zinc-blende one, which raises both the conduction and valence band energy levels, thus, facilitating a more balanced charge injection. The crystal phase-optimized superior-comprehensive performance in the QD-LED offers a novel degree of freedom for device engineering and promotes commercial applications for the upcoming display and illumination technologies.
Solution-processed quantum-dot light-emitting diodes (QLEDs) are attractive owing to high color purity and low-cost fabrication for large-area display panels, but the inferior carrier mobility of the organic polymer hole transport...
Quantum dot light-emitting diodes (QD-LEDs) have made great development in the performance. However, the efficiency droop at high brightness limits their applications in daylight displays and outdoor lightings. Herein, we systematically regulate the shell structure and composition, and the results indicate that CdSe-based QDs with ZnSe interlayer and thinner ZnSeS outermost layer as emitting layers (EML) enable high-performance QD-LEDs. Accordingly, the devices exhibit peak external quantum efficiency (EQE) of 22.9% with corresponding brightness of 67,840 cd/m2, and this efficiency can be still maintained > 90% of the maximum value even at 100,000 cd/m2, which satisfies the requirements for high-brightness display and lighting applications. This strong performance is mainly attributed to the ZnSe/ZnSeS graded shell that smooths the injection barrier between QD EML and the adjacent hole transport layers (HTL), and then improves the hole injection and charge injection balance, in particular at the high luminance and/or at high current density.
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