High-color rendering index white organic light-emitting diodes based on exciplex forming blue emitters

A novel emitting layer structure of white organic light-emitting diodes (WOLED) was developed using exciplex-forming two blue emitters, 2,3,4,5,6-penta(9H-carbazol-9-yl)benzonitrile (5CzCN) and tris(2-(1-(2,4-diisopropyldibenzo[b,d]furan-3-yl)-1H-imidazol-2-yl)phenyl)iridium (Ir(dbi)₃). The 5CzCN blue delayed fluorescence material and Ir(dbi)₃ phosphorescent emitter partially formed a red exciplex in the mixed film. Combination of blue emission from the blue emitters and red emission from the exciplex provided white emission in the blue emitting 5CzCN and Ir(dbi)₃ co-doped device. The WOLED fabricated using the blue emitting 5CzCN and Ir(dbi)₃ emitters achieved high color rendering index of 90.8 at 100 cd/m².