Fluorene-Based Copolymers for Red-Light-Emitting Diodes

The syntheses of new fluorene-based π-conjugated copolymers; namely, poly((5,5″-(3′,4′-dihexyl-2,2′;5′,2″-terthiophene 1′,1′-dioxide))-alt-2,7-(9,9-dihexylfluorene)) (PFTORT), poly((5,5″″-(3″,4″-dihexyl-2,2′:5′,2′:5″,2‴:5‴,2″″-quinquethiophene 1″,1″-dioxide))-alt-2,7-(9,9-dihexylfluorene)) (PFTTORTT), and poly((5,5-E-α-(2-thienyl)methylene)-2-thiopheneacetonitrile)-alt-2,7-(9,9-dihexylfluorene)) (PFTCNVT), are reported. In the solid state, PFTORT and PFTCNVT present red–orange emission (with a maximum at 610 nm) while PFTTORTT shows a red emission with a maximum at 666 nm. In all cases, electrochemical measurements have revealed p- and n-dopable copolymers. All these copolymers have been successfully tested in simple light-emitting diodes and show promising results for orange- and red-light-emitting devices.