Cyclodextrin-Threaded Conjugated Polyrotaxanes for Organic Electronics: The Influence of the Counter Cations

Autor: Michael J. Frampton, Sergio Brovelli, Lisa-Jodie Parrott, Gianluca Latini, Franco Cacialli, Harry L. Anderson
Rok vydání: 2008
Předmět:
Zdroj: Advanced Functional Materials. 18:2419-2427
ISSN: 1616-3028
1616-301X
DOI: 10.1002/adfm.200800120
Popis: A systematic investigation is reported into the influence of the counter cations on the optical, electrical and electroluminescent properties of polyelectrolytic conjugated polymers and of their cyclodextrin-threaded rotaxanes. We compare conjugated polyelectrolytes with sulfonated side groups where the anionic charge is balanced by Li+, K+, Cs +, tetramethylammonium (Me4N+) and cryptate-encapsulated potassium (K+ at [2.2.2]). Narrowing (for the unthreaded analogues) and a slight red-shift of the absorption spectra (for the rotaxanes) are found upon exchange of Li+ for larger cations, together with a blue-shift and an efficiency enhancement of the luminescence. These effects are similar in nature to those induced by rotaxination, and are therefore assigned to a marked reduction of intermolecular interactions between the conjugated cores. Exchange of Li+ for K+, Cs +, or Me4N+ results in a higher electroluminescence external quantum efficiency (EQE) for both polyrotaxanes and unthreaded polymers. For polyrotaxane-based devices the EQE increased approximately 7 times upon substitution of Li+ with Cs+ or Me4N+, thereby demonstrating the importance of the selection of the counter-cations for optimizing the performance of polyelectrolytic conjugated polymers in light-emitting devices. © 2008 WILEY-VCH Verlag GmbH and Co. KGaA.
Databáze: OpenAIRE
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