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Tuning the optoelectronic properties of polyfluorenes by copolymerisation with thiophene moieties

A series of alternating copolymers of the type A- alt-B, where A is 9,9-bis(2′-ethylhexyl)fluorene and B is a thiophene-based moiety, was synthesised via the palladium-catalysed Suzuki coupling. These copolymers were characterised by optical and electrochemical methods and used in the fabrication of...

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Bibliographic Details
Published in:Synthetic metals 2002-03, Vol.127 (1), p.251-254
Main Authors: Charas, A, Morgado, J, Martinho, J.M.G, Alcácer, L, Cacialli, F
Format: Article
Language:English
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Summary:A series of alternating copolymers of the type A- alt-B, where A is 9,9-bis(2′-ethylhexyl)fluorene and B is a thiophene-based moiety, was synthesised via the palladium-catalysed Suzuki coupling. These copolymers were characterised by optical and electrochemical methods and used in the fabrication of light-emitting diodes. We find that upon increasing the conjugation length of the B moiety, from a thiophene unit to 2,5-bis(2′-vinyl thienyl)thiophene, the fluorescence quantum yields are reduced both in solution (from 51 to 11%) and in solid state. Both absorption and emission are red-shifted, with the solid state emission maximum increasing from 476 nm (green) to 600 nm (orange). When the B unit is changed from thiophene to thiophene- S, S-dioxide, there is a significant increase in both the ionisation potential and electron affinity, and a concurrent reduction of the solution fluorescence efficiency (down to 16%). These polymers appear promising materials for optoelectronic applications.
ISSN:0379-6779
1879-3290
DOI:10.1016/S0379-6779(01)00637-3