Spiro-functionalized polyfluorene derivatives as blue light-emitting materials

New spiro-functionalized polyfluorene derivatives were synthesized with relatively high molecular weight. Among the polymers obtained, poly[(9,9-di-n-octyl-fluorene-2,7-diyl)-alt-co-(9,9′-spirobifluorene- 2,7-diyl)] exhibits narrow emission spectra and more stable photoluminescence spectra compared with conventional polyfluorenes. The pure blue emission is attributed to the amorphous structure and weak interchain interactions resulting from steric hindrance of the spiro-structure. The improved spectral stability results from higher glass transition temperature. Pure blue electroluminescence was demonstrated in single- and double-layer devices.