A low bandgap polymer based on isoindigo and bis(dialkylthienyl)benzodithiophene for organic photovoltaic applications

Authors

  • Kangli Cao,

    1. School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, China
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  • Zhongwei Wu,

    1. Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren'ai Road, Suzhou 215123, China
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  • Shugang Li,

    1. School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, China
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  • Baoquan Sun,

    1. Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren'ai Road, Suzhou 215123, China
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  • Guobing Zhang,

    1. School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, China
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  • Qing Zhang

    Corresponding author
    1. School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, China
    • School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, China
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Abstract

A new conjugated polymer PBDTT-ID based on N-alkylated isoindigo (ID) and bis(2,3-dialkylthienyl)-substituted benzo[1,2-b:4,5-b′]dithiophene (BDTT) as repeating units was synthesized. It had an optical bandgap of 1.56 eV and a highest occupied molecular orbital (HOMO) energy level of −5.71 eV. The optical, electrochemical, and photovoltaic properties of new polymer were compared with previous reported polymer PBDT-ID, which was based on bis(alkoxy)-substituted benzo[1,2-b:4,5-b′]dithiophene. The new polymer displayed lower HOMO energy level and better absorption properties than polymer PBDT-ID. The solar cells fabricated with PBDTT-ID/PC61BM (1:2, w/w) blends as active layers exhibited photoresponse in the range of 300–800 nm. A power conversion efficiency of 4.02% and an open circuit voltage (Voc) of 0.94 V were achieved in polymer solar cell device based on the new polymer. This was the highest Voc realized among the isoindigo-based polymers. The relatively high performances of new polymer in solar cell devices were interpreted in terms of material properties and morphologies of polymer/PCBM blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

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