Issue 39, 2019

Improving the photovoltaic performance of fluorinated 2,2′-bithiophene core-based D(A–Ar)2 type small molecules via strategically end-capped heteroaromatic substitution

Abstract

To reveal the influences of introducing various end-capping units onto small-molecule (SM) donors, in this article, 2-octylthio-thiophene (TS), 2-octyl-thiazole (TZ) and 2-octylthiothiazole (TZS) are strategically selected as end-capping units to combine with a fluorinated 2,2′-bithiophene (FBT) core and thiophene-flanked diketopyrrolopyrrole (TDPP) units as electron acceptors to afford three novel D(A–Ar)2 type SM donors, namely FBT(TDPP-TS)2, FBT(TDPP-TZ)2 and FBT(TDPP-TZS)2. The structure-property relationships provoked by slight changes in the terminal groups were systematically evaluated. In particular, TZS end-units make FBT(TDPP-TZS)2 possess better molecular stacking, higher mobility and better miscibility in the blend with PC71BM in comparison with the other two SMs. As a result, the introduction of TZS end-groups has been found to enhance the open-circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF) simultaneously. After optimization, an outstanding power conversion efficiency (PCE) of 8.91% with a Voc of 0.80 V, a Jsc of 16.75 mA cm−2 and a FF of 66.93% was obtained for the FBT(TDPP-TZS)2 based device, which is among the top values of the D(A–Ar)2 type single junction small molecular BHJ-OSCs. Our results obtained here indicate that strategic hetero-substitution of end-capping units in D(A–Ar)2 type SMs is an efficient strategy to improve photovoltaic performance.

Graphical abstract: Improving the photovoltaic performance of fluorinated 2,2′-bithiophene core-based D(A–Ar)2 type small molecules via strategically end-capped heteroaromatic substitution

Supplementary files

Article information

Article type
Paper
Submitted
02 Jul 2019
Accepted
31 Aug 2019
First published
03 Sep 2019

J. Mater. Chem. C, 2019,7, 12217-12230

Improving the photovoltaic performance of fluorinated 2,2′-bithiophene core-based D(A–Ar)2 type small molecules via strategically end-capped heteroaromatic substitution

M. Li, S. Wang, C. Bao, Z. Liu, D. Bai, Z. Yang, W. Zhu, Q. Peng and Y. Liu, J. Mater. Chem. C, 2019, 7, 12217 DOI: 10.1039/C9TC03577J

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