Highly Efficient Phosphorescent Light-Emitting Diodes by Using New Host Material

An electron-transporting triazole (Tz) and hole transporting carbazole (Cz) moieties were introduced into the fluorene structure via a Suzuki coupling reaction. The resulting material, 9-(4'-(9-(4'-(4,5-diphenyl-4H-1,2,4-triazol-3-y)-[1,1'-biphenyl]-4-yl)-9H-fluoren-9-yl)-[1,1'-biphenyl]-4-yl)-9H-carbazole (Tz-FL-Cz), was synthesized and can be used as the host layer in phosphorescent OLEDs. The synthesized material exhibits wide energy gap (3.46 eV). The absorption and emission maximum of the Tz-FL-Cz was observed at 300 nm and 389 nm, respectively. Blue phosphorescent devices using Tz-FL-Cz as host material exhibited maximum current efficiency of 3.2 cd/A and power efficiency of 1.3 lm/W, respectively.