Novel light-emitting electrophosphorescent copolymers based on carbazole with an Ir complex on the backbone

Abstract

Novel light-emitting phosphorescent polymers based on 3,6-carbazole with an iridium complex on the backbone were synthesized by Suzuki polycondensation of A-A and B-B type monomers. Three difluoro-substituted phenylpyridine iridium complexes with different ancillary ligands (FIrptz, FIrpic and FIrtmd) were introduced into the poly(3,6-carbazole) (PCz) backbone, causing distinct differences in the photo- and electroluminescence properties. The PL efficiency of PCz-FIrtmd5 is as high as 62% compared with the value of 9% of the fluorene-alt-carbazole-based copolymer (PFCz-FIrtmd5), which indicated that the 3,6-carbazole unit was suitable to serve as the host for a green electrophosphorescent polymer. The ancillary ligand of bicycloiridium complexes also affects the device performance based on chelating copolymers. The best device performances were obtained from copolymer PCz-FIrtmd5 with the maximal luminous efficiency of 4.4 cd A−1 and a luminance of 453 mA cm−2 at a current density of 10.3 mA cm−2 with the configuration: ITO/PEDOT/polymer + PBD(30 wt%)/Ba/Al.