Synthesis and characterization of highly efficient polyfluorene based green light-emitting copolymers

Abstract

The fluorene-based copolymers derived from 9,9``-dioctylfluorene (DOF) and 2,7-bis{1-(4-bromophenyl)-1-cyanovinyl}-9,9``-dihexylfluorene (BPCHF) were synthesized by a palladium catalyzed Suzuki coupling reaction. The comonomer feed ratios of DOF to BPCHF are 95:5, 75:25 and 50:50, and the corresponding copolymers are named PFPCF5, PFPCF25 and PFPCF, respectively. In the cases of PFPCF5 and PFPCF25, the incorporation of low band gap comonomer, BPCHF, generates distributed low energy site in the polymer chain. Since this site acts as an effective energy trap for exciton, efficient FOrster energy transfer occurred. Light-emitting device fabricated with ITO/PEDOT/PVK/PFPCF5/Ca/AI configuration exhibited very good performance with a high external quantum efficiency and a high brightness