Energy Regulation in White-Light-Emitting Diodes

Full electroluminescence (EL) white-light-emitting diodes (WLEDs) are currently a focus of research in the development of white light sources, owing to their outstanding potentiality and advantages in energy saving. The achievement of EL white emission always involves balanced co excitation of multi-color emissive centers (red/green/blue (R/G/B) or blue/orange (B/O)). However, R/G/B/O emitters have different bandgaps, making co-excitation extremely difficult. It is known that excitons formed in a widebandgap emitter are easily transferred to any narrow-bandgap emitter. Therefore, the regulation of the energy distribution among multi-color emissive centers is one of the key issues for the realization of white emission and improvement of EL performances and color quality/stability of WLEDs. Currently, many energy regulation strategies have been proposed, promoting the development of full EL-WLEDs. In this Focus Review, we discuss energy transfer mechanisms and energy regulation strategies in various of WLEDs, including white organic light-emitting diodes (WOLEDs), white quantum-dots light-emitting diodes (WQLEDs), and white perovskite light-emitting diodes (WPeLEDs). Finally, according to their status and challenges, we will offer an outlook, which we hope can inspire researchers and make a contribution to the developments of lighting, display fields, etc.