Novel Red Light‐Emitting Fluorene‐alt‐Carbazole Copolymers with Carbazole N‐Graft Cyclometalated Ir Complexes

A series of electrophosphorescent fluorene-alt-carbazole copolymers are synthesized by Suzuki polycondensation. A β-diketone-terminated alkyl chain grafted to the N-position of carbazole serves as a ligand to form a pendant cyclometalated Ir complex with 10-methyl-dibenzo[a,c]-phenazine (Mpq), 2,3-diphenylquinoxaline (Bpq), and 1-(benzo[b]thiophen-2-yl)isoquinoline (Biq), respectively. The emission of the device of PFCzIrBiq peaked at 715 and 790 nm, which is among the deepest red emissions reported so far. The well-achieved device performances could be attributed to a combination of a higher triplet energy and suitable HOMO/LUMO energy levels which can assure efficient charge injection as a result of the incorporation of a 3,6-carbazole unit into a polyfluorene backbone.