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Propeller-Shaped Acceptors for High-Performance Non-Fullerene Solar Cells: Importance of the Rigidity of Molecular Geometry

Research paper by Qinghe Wu, Donglin Zhao, Jinghui Yang, Valerii Sharapov, Zhengxu Cai, Lianwei Li, Na Zhang, Andriy Neshchadin, Wei Chen, Luping Yu

Indexed on: 25 Jan '17Published on: 06 Jan '17Published in: Chemistry of Materials



Abstract

This paper describes the synthesis and application of βTPB6 and βTPB6-C as electron acceptors for organic solar cells. Compound βTPB6 contains four covalently bonded PDIs with a BDT-Th core at the β-position. The free rotation of PDIs renders βTPB6 with varying molecular geometries. The cyclization of βTPB6 yields βTPB6-C with high rigidity of the molecular geometry and enlarged conjugated skeleton. The inverted solar cells based on βTPB6-C and PTB7-Th as the donor polymer exhibited the highest efficiency of 7.69% with Voc of 0.92 V, Jsc of 14.9 mAcm–2, and FF of 0.56, which is 31% higher than that for βTPB6 based devices. The larger fraction of βTPB6-C and PTB7-Th than that of βTPB6:PTB7-Th in a blend film takes a face-on orientation packing pattern for π-systems that benefits the charge transport and hence higher PCE value than that for βTPB6:PTB7-Th. It was also found that a proper DIO:DPE additive further enhances this trend, which results in an increase of the PCE value for βTPB6-C:PTB7-Th while decreasing the PCE value for βTPB6:PTB7-Th.

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