Inversion of Dominant Polarity in Ambipolar Polydiketopyrrolopyrrole with Thermally Removable Groups

Authors

  • Junghoon Lee,

    1. Interdisciplinary School of Green Energy, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science, and Technology (UNIST), Ulsan 689-798, South Korea
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  • A-Reum Han,

    1. School of Nano-Bioscience and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, South Korea
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  • Jayeon Hong,

    1. School of Nano-Bioscience and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, South Korea
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  • Jung Hwa Seo,

    1. Department of Materials Physics, Dong-A University, Busan 604-714, South Korea
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  • Joon Hak Oh,

    Corresponding author
    1. School of Nano-Bioscience and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, South Korea
    • School of Nano-Bioscience and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, South Korea
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  • Changduk Yang

    Corresponding author
    1. Interdisciplinary School of Green Energy, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science, and Technology (UNIST), Ulsan 689-798, South Korea
    • Interdisciplinary School of Green Energy, KIER-UNIST Advanced Center for Energy, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science, and Technology (UNIST), Ulsan 689-798, South Korea.
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Abstract

A narrow bandgap polymeric semiconductor, BOC-PTDPP, comprising alkyl substituted diketopyrrolopyrrole (DPP) and tert-butoxycarbonyl (t-BOC)-protected DPP, is synthesized and used in organic field-effect transistors (OFETs). The polymer films are prepared by solution deposition and thermal annealing of precursors featuring thermally labile t-BOC groups. The effects of the thermal cleavage on the molecular packing structure in the polymer thin films are investigated using thermogravimetric analysis (TGA), UV-vis spectroscopy, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) analysis. Upon utilization of solution-shearing process, integrating the ambipolar BOC-PTDPP into transistors shows p-channel dominant characteristics, resulting in hole and electron mobilities as high as 1.32 × 10−2 cm2 V−1 s−1 and 2.63 × 10−3 cm2 V−1 s−1, which are about one order of magnitude higher than those of the drop-cast films. Very intriguingly, the dominant polarity of charge carriers changes from positive to negative after the thermal cleavage of t-BOC groups at 200 °C. The solution-sheared films upon subsequent thermal treatment show superior electron mobility (μe = 4.60 × 10−2 cm2 V−1 s−1), while the hole mobility decreases by one order of magnitude (μh = 4.30 × 10−3 cm2 V−1 s−1). The inverter constructed with the combination of two identical ambipolar OFETs exhibits a gain of ∼10. Reported here for the first time is a viable approach to selectively tune dominant polarity of charge carriers in solution-processed ambipolar OFETs, which highlights the electronically tunable ambipolarity of thermocleavable polymer by simple thermal treatment.

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