Efficient Solution-Processed Blue Electrophosphorescent Devices Based on a Novel Small-Molecule Host

Efficient blue small molecular phosphorescent light-emitting diodes with a blue phosphorescent dyebis(3,5-difluoro-2-(2-pyridyl)-phenyl-(2-carboxypride) iridium (III) (FIrpic) doped into a novel small-molecule host 9,9-bis4-(3,6-di-tert-butylcarbazol-9-yl)phenyl] fluorene (TBCPF) as the light-emitting layer have been fabricated by spin-coating. The host TBCPF can form homogeneous amorphous films by spin-coating and has triplet energy higher than that of the blue phosphorescent dye FIrpic. All the devices with different FIrpic concentration in the emitting layer give emission from FIrpic indicating complete energy transfer from TBCPF to FIrpic. The device shows the best performance with a peak brightness of 8050cd/m2 at 10.2V and the maximum current efficiency up to 3.52cd/A, when the FIrpic doped concentration is ashigh as 16%.