High-Quality All-Solution-Processed White Light-Emitting Diodes Based on Colloidal Quantum Wells

White light-emitting diodes (WLEDs) with high-quality emissions ( $\ge 80$ ) are essential for general lighting. However, the color rendering index (CRI) of nanocrystal WLEDs are usually poor, particularly for colloidal quantum-well (CQW) based WLEDs due to the lack of suitable blue emitters. Here, a deep-blue (445 nm) colloidal quantum-dot LED (CQD-LED) is developed, which shows a luminance of 1335 cd/m2, marking it among the brightest deep-blue Zn-based CQD-LEDs. Then, for the first time, an all-solution-processed WLED based on CQWs is reported. Such WLED is achieved by incorporating blue CQDs with red CQWs, coupled with the additional generation of interfacial emissions. The WLED exhibits a high CRI of 85.3, an external quantum efficiency of 0.085%, and a luminance of 1290 cd/m2, representing the best performance for WLEDs based on CQWs.