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Polaron pair mediated triplet generation in polymer/fullerene blends

Stoichko Dimitrov Orcid Logo, Scot Wheeler, Dorota Niedzialek, Bob C. Schroeder, Hendrik Utzat, Jarvist M. Frost, Jizhong Yao, Alexander Gillett, Pabitra S. Tuladhar, Iain McCulloch, Jenny Nelson Orcid Logo, James Durrant Orcid Logo

Nature Communications, Volume: 6, Start page: 6501

Swansea University Authors: Stoichko Dimitrov Orcid Logo, Jenny Nelson Orcid Logo, James Durrant Orcid Logo

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DOI (Published version): 10.1038/ncomms7501

Abstract

Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pai...

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Published in: Nature Communications
ISSN: 2041-1723 2041-1723
Published: 2015
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URI: https://cronfa.swan.ac.uk/Record/cronfa31796
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Abstract: Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.
Item Description: The author made a substantial contribution to the conception and design of the study; to the organisation of the conduct of the study; to carrying out the study (including acquisition of study data); to analysis and interpretation of study data. The author helped draft the output.
College: Faculty of Science and Engineering
Start Page: 6501