Quantum-Dot-Electrolyte Light-Emitting Diodes for Displays

Electroluminescence (EL) is essential for modern technologies, such as displays, lighting, and optical communications. To date, some kinds of artificial EL devices have been developed, including organic light-emitting diodes (OLEDs), quantum-dot (QD) LEDs, and light-emitting electrochemical cells. However, issues (e.g., inefficient charge injection, exciton quenching) limit the further EL performance. Here, another promising kind of EL device is reported, which is called QD-electrolyte LED (QE-LED). The key feature of QE-LED is that an ionic liquid is doped into QDs as the electrolyte emitter of multi-layer device architectures. Both theoretical and experimental analyses reveal that an enhanced interface electric field from the in situ formed electrical double layer is leveraged to improve the charge injection and transport. With the introduction of insulating polymers into QD-electrolyte emitters, red QE-LED achieves an external quantum efficiency of 20.5% and a lifetime (T₉₅) over 3.74 × 10⁵ h at the display-related luminance of 100 cd m^-2, indicating that the QE-LED is among the best EL devices. Furthermore, an active-matrix QE-LED display is demonstrated with superior stability that overtakes the commercial benchmark. These results offer an avenue to discover unexplored EL devices and provide potential pathways to enhance charge dynamics for EL devices.