The fate of electron–hole pairs in polymer:fullerene blends for organic photovoltaics

Martina Causa', Jelissa De Jonghe-Risse, Mariateresa Scarongella, Jan C. Brauer, Ester Domingo, Jacques-E. Moser, Natalie Stingelin, Natalie Banerji

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

There has been long-standing debate on how free charges are generated in donor: acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.
Original languageEnglish (US)
JournalNature Communications
Volume7
Issue number1
DOIs
StatePublished - Sep 2 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: M.C., M.S., J.C.B. and N.B. thank the Swiss National Science Foundation (PP00P2_150536) and the University of Fribourg for funding. N.B., J.D.J.-R and J.-E.M are grateful to NCCR-MUST, a research instrument of the Swiss National Science Foundation, for support. N.S. is supported by a European Research Council (ERC) Starting Independent Researcher Fellowship under the grant agreement No. 279587. E.B.-D. is funded by a SABIC Post-Doctoral Fellowship at King Abdullah University of Science and Technology. We thank Prof. Martin Heeney (Imperial College, London, UK) for providing the pBTTT polymer, and we thank Prof. E. Vauthey and R. Letrun (Univ. of Geneva, Switzerland) for use of their fluorescence up-conversion set-up and help with the experiment. We thank Dr A. Devizis (Center for Physical Sciences and Technology, Vilnius) for having built the EDA set-up and for useful discussion.

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