Interfacial Exciplex Host to Release Interfacial Accumulated Charges for Highly Efficient and Bright Solution‐Processed White Organic Light‐Emitting Diodes

Abstract White organic light‐emitting diodes (WOLEDs) have attracted extensive attention and are considered as an ideal next‐generation lighting source. However, maintaining high efficiency and high color rendering index (CRI) in WOLEDs still faces great challenges. The charges accumulation at the interface leads to nonradiative recombination and further Joule heat, which is a source of efficiency decrease and device degradation. In this paper, the interfacial exciplex is designed as the host for high efficiency; the blue thermally activated delayed fluorescence (TADF) material and the red phosphorescent material are employed as guests for high CRI. Due to the interfacial exciplex host, electrons don't need to overcome the potential barrier to inject into the light‐emitting layer, but can directly compound with holes at the interface, so as to release the interfacial accumulated charges and improve the recombination efficiency of carriers. Also, a suitable energy level gradient for hole injection transmission is constructed. Finally, WOLEDs with a current efficiency of 52.8 cd A −1 , an external quantum efficiency of 22.9 %, the Commission Internationale de I'Eclairage (CIE) coordinate of (0.35,0.39), and the high CRI of 80 are obtained, which are the highest values ever achieved by the solution processed WOLEDs based on blue TADF emitters.