Synthesis and characterisation of polyfluorenes with light-emitting segments

We present the synthesis and characterisation of two copolymers. They consists of poly(9-hexyl-9-(2'-ethylhexyl)fluorene) (HEH-PF) with a small amount of another polymer with a narrow band-gap. The synthetic route was designed to allow the incorporation of only one low band-gap segment per polymer chain. Photoluminescence measurements showed that energy transfer from the PF-segments to the low band-gap segments did occur. In the solid state, all emissions were detected from the low band-gap segments with photoluminescence quantum yields up to 68%. One copolymer showed a low threshold for lasing (2 μJ/cm 2 ) in a microcavity device.