Efficient Red-Emitting Cyclometalated Iridium(III) Complexes Containing Lepidine-Based Ligands

Heteroleptic cyclometalated iridium(III) complexes featuring lepidine-based ligands and acetyl acetone auxiliary ligand are synthesized. Multiple lowest energy absorption bands are observed for these complexes indicating substantial mixing of the singlet and triplet levels. All the complexes emit orange or red color in dichloromethane solutions with lifetimes in the range 1.6−3.7 μs. The emission in the complexes probably originates from the ³MLCT state. The complexes are applied as emitting guests in LED devices of the structure ITO/HTL(BPAPF or NPB)/6% Ir in CBP/BCP/Alq₃/LiF/Al. They exhibit excellent device characteristics with an orange to red EL profile.