A Series of Dibenzofuran-Based n-Type Exciplex Host Partners Realizing High-Efficiency and Stable Deep-Red Phosphorescent OLEDs

Deep-red to near-infrared (NIR) OLEDs, which yield emission peak wavelengths beyond λ=660 nm, are applicable as unique light sources in plant growth or health monitoring systems. Compared with other visible-spectrum OLEDs, however, research in the field of deep-red OLEDs is not as advanced. In this work, three new types of dibenzofuran-based host materials are developed as n-type exciplex host partners. Combining these with the deep-red iridium complex bis(2,3-diphenylquinoxaline)iridium(dipivaloylmethane) ((DPQ)₂Ir(dpm)]) and N,N′-di(naphalene-1-yl)-N,N′-diphenylbenzidine (α-NPD) as a p-type exciplex host partner, a highly efficient deep-red OLED can be realized with a maximum external quantum efficiency (η_ext,max) of over 16 % with Comission Internationale de l′Éclairge (CIE) coordinates of (0.71, 0.28). In addition, the effect of the doping concentration and the p/n ratio of the exciplex host on the efficiency and the lifetime of the OLEDs are investigated. Consequently, the optimized device exhibits a η_ext,max of over 15 % and a six-time longer lifetime operating at high brightness of 100 cd m^?2 compared with other state-of-the-art deep-red OLEDs.