The Impact of Interfacial Mixing on Förster Transfer at Conjugated Polymer Heterojunctions

Neutron reflectivity and photoluminescence measurements are reported on bilayers of polyfluorene‐based conjugated polymers. By using a novel thermal processing procedure it is possible to control the width of the interface between poly(9,9‐dioctylfluorene) (F8) and poly(9,9‐dioctylfluorene‐alt‐benzo...

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Veröffentlicht in:Advanced functional materials 2009-01, Vol.19 (1), p.157-163
Hauptverfasser: Higgins, Anthony M., Cadby, Ashley, Lidzey, David G., Dalgliesh, Robert M., Geoghegan, Mark, Jones, Richard A. L., Martin, Simon J., Heriot, Sasha Y.
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Sprache:eng
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Zusammenfassung:Neutron reflectivity and photoluminescence measurements are reported on bilayers of polyfluorene‐based conjugated polymers. By using a novel thermal processing procedure it is possible to control the width of the interface between poly(9,9‐dioctylfluorene) (F8) and poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT), and measure the impact of interfacial roughness on the resonant energy transfer of excitons at the interface (Förster transfer). It is found that increasing the root mean square (rms) roughness of the F8/F8BT interface over the range of ∼1 nm to ∼5 nm leads to a greatly enhanced Förster transfer from F8 to F8BT molecules. By comparing photoluminescence measurements with simple calculations it is concluded that the level of enhancement of the F8BT peak at rough interfaces can only be adequately explained if mixing of F8 and F8BT at a molecular level dominates over the interfacial roughness due to thermally excited capillary waves. Neutron reflectivity measurements demonstrate that thermal processing allows systematic control of the width of polyflourene‐based (F8/F8BT) heterojunctions. Broader interfaces lead to greatly enhanced Förster transfer from F8 to F8BT molecules, which can only be adequately explained if mixing of the polymers at a molecular level dominates over the interfacial roughness due to thermally excited capillary waves.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.200800887