Synthesis and Electroluminescence of New Polyfluorene Copolymers Containing Iridium Complex Coordinated on the Main Chain

Abstract

We have synthesized new light-emitting polyfluorene copolymers containing a novel iridium complex with a beta-diketonate unit as an ancillary and characterized them by gel permeation chromatography (GPC), UV-vis absorption spectrophotometer, PL emission spectrofluorometer, and cyclic voltammetry. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DCS) measurements indicated that the copolymers have good thermal and morphological stability. The synthesized polyfluorene copolymers with the iridium complex, PFIrptbs, were synthesized through palladium-catalyzed Suzuki coupling reactions. These polymers were found to be thermally stable and readily soluble in common organic solvents. The UV-vis absorption and PL emission spectra of he synthesized polymers did not show significant energy transfer from PBOPF segments to the iridium complex units. Light-emitting devices based on these polymers were fabricated with an indium-tin oxide/poly(3,4-ethylene dioxythiphene):poly(styrenesulfonate) (PEDOT:PSS)/polymers/Balq/LiF/Al configuration. Examination of the electroluminescence (EL) emissions of the synthesized showed that the EL intensity of the orange color slightly increased with increasing content of the iridium complex. In particular, the device using PFIrptb 025 exhibits a maximum brightness of 2260 cd/m(2) and a maximum current efficiency of 1.10 cd/A.