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Improved Performance of Polymer:Polymer Solar Cells by Doping Electron-Accepting Polymers with an Organosulfonic Acid

Authors

  • Sungho Nam,

    1. Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea
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  • Minjung Shin,

    1. Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea
    2. Solar Cell Business Team, LG Innotek, Gyeonggi-do 447-705, S. Korea
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  • Hwajeong Kim,

    Corresponding author
    1. Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea
    • Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea.
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  • Chang-Sik Ha,

    1. Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, S. Korea
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  • Moonhor Ree,

    1. Division of Advanced Materials Science, Department of Chemistry, Center for Electro-Photo Behaviors in Advanced Molecular Systems, BK School of Molecular Science, and Polymer Research Institute, Pohang University of Science and Technology (POSTECH), Pohang 790-784, S. Korea
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  • Youngkyoo Kim

    Corresponding author
    1. Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea
    • Organic Nanoelectronics Laboratory, Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, S. Korea.
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Abstract

The performance of polymer:polymer solar cells that are made using blend films of poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co- benzothiadiazole (F8BT) is improved by doping the F8BT polymer with an organosulfonic acid [4-ethylbezenesulfonic acid (EBSA)]. The EBSA doping of F8BT, to form F8BT-EBSA, is performed by means of a two-stage reaction at room temperature and 60°C with various EBSA weight ratios. The X-ray photoelectron spectroscopy measurement reveals that both sulfur and nitrogen atoms in the F8BT polymer are affected by the EBSA doping. The F8BT-EBSA films exhibit huge photoluminescence quenching, ionization potential shift toward lower energy, and greatly enhanced electron mobility. The short-circuit current density of solar cells is improved by ca. twofold (10 wt.% EBSA doping), while the open-circuit voltage increases by ca. 0.4 V. Consequently, the power conversion efficiency was improved by ca. threefold, even though the optical density of the P3HT:F8BT-EBSA blend film is reduced by 10 wt.% EBSA doping due to the nanostructure and surface morphology change.

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