Synthesis and Photoluminescence Properties of Iridium-Fluorene Main-Chain Copolymers

The cyclometalated iridium complex based on 2-(4-bromophenyl)-benzimidazole as main ligand and acetylacetonate as ancillary ligand was prepared and then introduced in polyfluorene (PFO) subject through Suzuki polycondensation to obtain the main-chain copolymers.The iridium complex and copolymers were characterized by elemental analysis,FT-IR,¹H-NMR,UV and fluorescence spectroscopy.Results showed that the iridium complex emitted green-light with maximum peaks at 505 nm and 535 nm and the copolymers exhibited blue emission of PFO subject and green emission of iridium complex.The green light intensity was enhanced with the increasing of iridium complex content,which indicated that there existed partial transfer of energy between the subject and object and the emission color of copolymers shifted from blue to green by adjusting the proportion of the iridium complex.When the iridium complex mole fraction reached 2%,the color coordinates of copolymer just appeared at the junction of blue and green area and the blue fluorescence intensity was greater than the green phosphor,but the copolymer exhibited green-light emission when the mole fraction of iridium complex was greater than 2%.The copolymer fluorescence quantum efficiency was significantly improved compared with the phosphorescent iridium complex (2.7%) and the copolymer had good thermal stability.