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 wide-bandgap 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.