Suppressing Energy Loss due to Triplet Exciton Formation in Organic Solar Cells: The Role of Chemical Structures and Molecular Packing

Xiankai Chen, Tonghui Wang, Jean-Luc Bredas

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34 Scopus citations

Abstract

In the most efficient solar cells based on blends of a conjugated polymer (electron donor) and a fullerene derivative (electron acceptor),ultrafast formation of charge-transfer (CT) electronic states at the donor-acceptor interfaces and efficient separation of these CT states into free charges, lead to internal quantum efficiencies near 100%. However, there occur substantial energy losses due to the non-radiative recombinations of the charges, mediated by the loweset-energy (singlet and triplet) CT states; for example, such recombinations can lead to the formation of triplet excited electronic states on the polymer chains, which do not generate free charges. This issue remains a major factor limiting the power conversion efficiencies (PCE) of these devices. The recombination rates are, however, difficult to quantify experimentally. To shed light on these issues, here, an integrated multi-scale theoretical approach that combines molecular dynamics simulations with quantum chemistry calculations is employed in order to establish the relationships among chemical structures, molecular packing, and non-radiative recombination losses mediated by the lowest-energy charge-transfer states.
Original languageEnglish (US)
Pages (from-to)1602713
JournalAdvanced Energy Materials
Volume7
Issue number15
DOIs
StatePublished - Apr 21 2017

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: X.-K.C. and T.W. contributed equally to this work. This work was supported by competitive research funding at the King Abdullah University of Science and Technology (KAUST) and by the ONR Global, Grant N62909-15-1-2003. The authors acknowledge the KAUST IT Research Computing Team and Supercomputing Laboratory for providing precious continuous assistance as well as computational and storage resources.

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