Single Chain White-Light-Emitting Polyfluorene Copolymers Containing Iridium Complex Coordinated on the Main Chain

Abstract

We report the synthesis of single chain white-light-emitting polyfluorene copolymers containing a novel iridium complex with a beta-diketonate unit, bis(2-benzothiazol-2-yl-N-ethylearbazle)iridium-1,3-bis(p-bromophenyl)1,3-propanedione ((bec)(2)IrdbmBr), as the red emission unit. The synthesized polyfluorene copolymers containing the carbazole and iridium complex, poly[9,9-bis(4-octyloxyphenyl(fluorene-2,7-dilyl-co-(N-hexylcarbazole-3,6-diyl)]-co-[bis(2-benzothiazol-2-yl-N-ethylcarbazole)iridium-1,3-bis(p-bromophenyl)-propanedione-1,3-diyl]) (PFCzIrbees), were synthesized via palladium-catalyzed Suzuki coupling reactions. These polymers were found to be thermally stable and readily soluble in common organic solvents. Interestingly, the synthesized polymers, PFCzIrbec 05 and PFCzIrbec 2, exhibited two strong emission bands in both the blue and red spectral regions. Light-emitting devices based on these polymers were fabricated in an ITO/PEDOT:PSS/poly(TPD)/polymers/TPBi/LiF/Al configuration. We obtained white light emission from a single polymer chain by incorporating (bec)(2)Irdbm Br as the red emission unit into a BOPF and carbazole main chain as the host and blue emission. This device exhibited good performance. In particular, EL device fabricated with PFCzIrbec 2 was found to emit white light consisting of simultaneous blue and red emission with CIE coordinate of (0.31, 0.32), which are close to the standard for white light emission. Moreover, the EL spectrum of PFCzIrbec 2 was stable with respect applied voltage, and CIE coordinates were almost not changed at various driving voltages.