Iridium complex grafted to 3,6-carbazole-alt-tetraphenylsilane copolymers for blue electrophosphorescence

Abstract

We designed a 3,6-dibromo-9-hexyl-9H-carbazole derivative with the blue emissive iridium complex bis[2-(4,6-difluorophenyl)pyridyl-N,C 2′](picolinato)iridium(III) (Flrpic) linked at the alkyl terminal. Based on this monomer, novel 3,6-carbazole-alt-tetraphenylsilane copolymers grafted with Flrpic were synthesized by palladium-catalyzed Suzuki coupling reaction, and the content of Flrpic in the polymers could be controlled by feed ratio of the monomers. The polymer films mainly show blue emission from Flrpic, and the emission intensity from the polymer backbones is much weaker compared with the doped analogues, which demonstrates an efficient energy transfer from polymeric host to covalently bonded guest. The phase separation in the polymers was suppressed, which can be identified by atomic force microscopy and designed electroluminescent (EL) devices. EL devices based on the polymers exhibited blue phosphorescence from Flrpic. The luminous efficiency of preliminary devices reached 2.3 cd/A, and the efficiency roll-off at high current densities was suppressed. © 2010 Wiley Periodicals, Inc.