Fluorene-based light-emitting polymers

Several series of fluorene-based light-emitting polymers with the emphasis on achieving efficient and stable blue light emission are reported. Spiro-functionalization may narrow the emission spectra (with smaller tail at longer wavelengths) of fluorene homopolymers to provide purer blue emission. The thermal spectral stability of the polymers could also be improved because of the elevation of the glass transition temperature caused by the spiro-functionalization. However, the excimer emission in fluorene homopolymers is not suppressed by the spiro-functionalization. Alternate copolymers of 9,9-dihexylfluorene and substituted phenylenes may emit efficient blue light both in solution and in film. The optical properties are dependent on the substitution on the phenylene ring. The alkoxy-substituted polymers displayed efficient PL and EL and good thermal spectral stability. The HOMO and LUMO energy levels of the polymers based on the backbone structure could be tuned in a wide range by attaching different functional groups on the phenylene ring. By attaching europium(III) complex at the ends of the side chains in the alternate copolymers, we have demonstrated a new approach to achieving red emission with a very narrow spectrum. The copolymers of 9,9-dihexylfluorene and thiophene and bithiophene with different substitutions were also synthesized to study the effect of substitution and regioregularity on the optical and other physical properties of the polymers.