Effects of donor unit and π-bridge on photovoltaic properties of D–A copolymers based on benzo[1,2-b:4,5-c']-dithiophene-4,8-dione acceptor unit

Authors

  • Haijun Bin,

    1. College of Chemistry and Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University, Xiangtan, People's Republic of China
    2. CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, People's Republic of China
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  • Lu Xiao,

    1. CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, People's Republic of China
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  • Yong Liu,

    1. College of Chemistry and Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University, Xiangtan, People's Republic of China
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  • Ping Shen,

    Corresponding author
    1. College of Chemistry and Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University, Xiangtan, People's Republic of China
    2. CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, People's Republic of China
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  • Yongfang Li

    Corresponding author
    1. CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, People's Republic of China
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ABSTRACT

A series of donor-π-acceptor (D-π-A) conjugated copolymers (PBDT-AT, PDTS-AT, PBDT-TT, and PDTS-TT), based on benzo[1,2-b:4,5-c']dithiophene-4,8-dione (BDD) acceptor unit with benzodithiophene (BDT) or dithienosilole (DTS) as donor unit, alkylthiophene (AT) or thieno[3,2-b]thiophene (TT) as conjugated π-bridge, were designed and synthesized for application as donor materials in polymer solar cells (PSCs). Effects of the donor unit and π-bridge on the optical and electrochemical properties, hole mobilities, and photovoltaic performance of the D-π-A copolymers were investigated. PSCs with the polymers as donor and PC70BM as acceptor exhibit an initial power conversion efficiency (PCE) of 5.46% for PBDT-AT, 2.62% for PDTS-AT, 0.82% for PBDT-TT, and 2.38% for PDTS-TT. After methanol treatment, the PCE was increased up to 5.91%, 3.06%, 1.45%, and 2.45% for PBDT-AT, PDTS-AT, PBDT-TT, and PDTS-TT, respectively, with significantly increased FF. The effects of methanol treatment on the photovoltaic performance of the PSCs can be ascribed to the increased and balanced carrier transport and the formation of better nanoscaled interpenetrating network in the active layer. The results indicate that both donor unit and π-bridge are crucial in designing a D-π-A copolymer for high-performance photovoltaic materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1929–1940

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