Photocurrent Enhancement in Diketopyrrolopyrrole Solar Cells by Manipulating Dipolar Anchoring Terminals on Alkyl-Chain Spacers

Authors

  • Ailing Tang,

    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
    2. Graduate School, Chinese Academy of Sciences, Beijing, 100190 (P. R. China)
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  • Zhenhuan Lu,

    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
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  • Shuming Bai,

    1. State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory of Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China)
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  • Jianhua Huang,

    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
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  • Yuxia Chen,

    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
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  • Prof. Qiang Shi,

    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
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  • Prof. Chuanlang Zhan,

    Corresponding author
    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
    • Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517

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  • Prof. Jiannian Yao

    Corresponding author
    1. Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517
    • Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 (P. R. China), Fax: (+86) 10-82616517

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Abstract

We chose DPP-BDT-DPP {DPP=diketopyrrolopyrrole, BDT=4,8-di-[2-(2-ethylhexyl)-thienyl]benzo[1,2-b:4,5-b′]dithiophene} as a model backbone and varied the anchoring groups [[BOND]C5H11, [BOND]COOCH3, and [BOND]SiCH3(OSiCH3)2] terminated on the N-substituted alkyl-chain spacer of the DPP units to study the effect of anchoring terminals on the morphology of blend film and on the device performances of bulk heterojunction solar cells. By replacing the nonpolar [BOND]C5H11 anchoring terminal with the polar [BOND]COOCH3 anchoring terminal leads to an enhancement in the short-circuit current density (Jsc) (4.62 vs. 9.32 mA cm−2), whereas the value of Jsc sharply decreases to 0.45 mA cm−2 if the [BOND]C5H11 anchoring terminal is replaced by a [BOND]SiCH3(OSiCH3)2 group. The changes in Jsc are associated with changes in the π–π stacking distance (3.39→3.34 Å vs. 3.39→3.45 Å) and the phase size (50→20 nm vs. 50→>250 nm) through alteration of the anchoring group from [BOND]C5H11 to [BOND]COOCH3 versus from [BOND]C5H11 to [BOND]SiCH3(OSiCH3)2. Interestingly, the anchoring terminals bring about drastic changes in molecular orientations, which result in different out-of-plane hole transport. This is the first time this effect has been systemically demonstrated to improve photocurrent generation by manipulating the dipolar anchoring groups terminated on the alkyl-chain spacer.

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