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Diketopyrrolopyrrole-based liquid crystalline conjugated donor–acceptor copolymers with reduced band gap for polymer solar cells

Authors

  • Yunli Han,

    1. Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
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  • Lie Chen,

    Corresponding author
    1. Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
    2. Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
    • Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
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  • Yiwang Chen

    Corresponding author
    1. Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
    2. Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
    • Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China
    Search for more papers by this author

Abstract

A new liquid crystalline (LC) acceptor monomer 2,5-bis[4-(4′-cyanobiphenyloxy)dodecyl]-3,6-dithiophen-2-yl-pyrrolo[3,4-c]pyrrole-1,4-dione (TDPPcbp) was synthesized by incorporating cyanobiphenyl mesogens into diketopyrrolopyrrole (DPP). The monomer was copolymerized with bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′] dithiophene (BDT) and N-9′-heptadecanylcarbazole (CB) donors to obtain donor–acceptor alternating copolymers poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-alt-3,6-bis(thiophen-5-yl)-2,5-bis[4-(4′-cyanobiphenyloxy)dodecyl]-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione] (PBDTDPPcbp) and poly[N-9′-heptadecanyl-2,7-carbazole-alt-3,6-bis(thiophen-5-yl)-2,5-bis[4-(4′-cyano-biphenyloxy)dodecyl]-2,5-dihydropyrrolo[3, 4-c]pyrrole-1,4-dione] (PCBTDPPcpb) with reduced band gap, respectively. The LC properties of the copolymers, the effects of main chain variation on molecular packing, optical properties, and energy levels were analyzed. Incorporating the mesogen cyanobiphenyl units not only help polymer donors to pack well through mesogen self-organization but also push the fullerene acceptor to form optimized phase separation. The bulk heterojunction photovoltaicdevicesshow enhanced performance of 1.3% for PBDTDPPcbp and 1.2% for PCBTDPPcbp after thermal annealing. The results indicate that mesogen-controlled self-organization is an efficient approach to develop well-defined morphology and to improve the device performance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

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