End Group Tuning in Acceptor–Donor–Acceptor Nonfullerene Small Molecules for High Fill Factor Organic Solar Cells

Andrew Wadsworth, Helen Bristow, Zeinab Hamid, Maxime Babics, Nicola Gasparini, Colm W. Boyle, Weimin Zhang, Yifan Dong, Karl J. Thorley, Marios Neophytou, Raja Shahid Ashraf, James R. Durrant, Derya Baran, Iain McCulloch

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

High fill factors have only recently become commonplace in nonfullerene-based organic solar cells, with the balance of charge carrier mobilities often cited as the contributing factor. Here an end-group modification to a commonly used nonfullerene acceptor (O-IDTBR) is reported, in which the rhodanine end groups are replaced with dicyano moieties, resulting in the acceptor O-IDTBCN. This new acceptor affords significant improvement in the fill factor (73%) and photocurrent (19.8 mA cm−2) in organic solar cells with the low bandgap polymer PTB7-Th. A narrowing of the bandgap, as a result of greater push–pull hybridization, allows complementary absorption to the donor and thus improved photon harvesting. Additionally, the measurement of charge carrier mobilities and lifetimes in both systems reveal that the PTB7-Th:O-IDTBCN blend possesses more balanced charge carrier mobilities, and longer lifetimes. Morphology studies reveal a slightly greater degree of molecular mixing of the O-IDTBCN when blended with PTB7-Th, despite the greater and more balanced charge carrier mobilities in this blend.
Original languageEnglish (US)
Pages (from-to)1808429
JournalAdvanced Functional Materials
Volume29
Issue number47
DOIs
StatePublished - Jun 11 2019

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