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Alkylthienyl substituted asymmetric 2D BDT and DTBT-based polymer solar cells with a power conversion efficiency of 9.2%

Abstract

Alkyl thiophene unit was employed for the first time as side chain substituent on an asymmetric benzodithiophene (BDT) building block in the design of novel light-harvesting polymers. A new D–A type polymer (PBDTTh-DTffBT) based on the alkylthienyl asymmetric BDT and the well-known 4,7-di(thiophen-2-ethylhexyl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) was synthesized through a palladium catalyzed Stille coupling reaction. Efficient bulk heterojunction solar cells were fabricated by blending PBDTTh-DTffBT with PC71BM. The optimized PBDTTh-DTffBT -based photovoltaic device exhibits an open circuit voltage (VOC) of 0.87 V, a short-circuit current density (JSC) of 15.06 mA cm-2, a fill factor (FF) of 70.4% and a high power conversion efficiency (PCE) of 9.22%. The PCE was higher than the polymers which have the same backbone structure but also have the 1D or 2D symmetric BDT unit. In addition, a PCE of 7.83% with a VOC of 0.91 V, a JSC of 13.62 mA cm-2, and an FF of 63.2% was obtained for PBDTTh-DTffBT/ITIC, which is also impressive for non-fullerene PSCs. The results indicate that our design strategy of introducing alkylthienyl unit as side chain to fabricate asymmetric BDT-based polymer is efficient in improving photovoltaic performance.

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Publication details

The article was received on 21 Nov 2017, accepted on 03 Jan 2018 and first published on 04 Jan 2018


Article type: Paper
DOI: 10.1039/C7TA10247J
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Alkylthienyl substituted asymmetric 2D BDT and DTBT-based polymer solar cells with a power conversion efficiency of 9.2%

    C. Gu, D. Liu, J. Wang, Q. Niu, C. Gu, B. Shahid, B. Yu, H. Cong and R. Yang, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C7TA10247J

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