A Quasi-2D Polypyrrole Film with Band-Like Transport Behavior and High Charge-Carrier Mobility.

Liu, Kejun; Réhault, Julien; Liang, Baokun; Hambsch, Mike; Zhang, Yingying; Seçkin, Sezer; Zhou, Yunxia; Shivhare, Rishi et al. · Adv Mater · 2023

basic_science · Level V

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Abstract

Quasi-2D (q2D) conjugated polymers (CPs) are polymers that consist of linear CP chains assembled through non-covalent interactions to form a layered structure. In this work, the synthesis of a novel crystalline q2D polypyrrole (q2DPPy) film at the air/H<sub>2</sub> SO<sub>4</sub> (95%) interface is reported. The unique interfacial environment facilitates chain extension, prevents disorder, and results in a crystalline, layered assembly of protonated quinoidal chains with a fully extended conformation in its crystalline domains. This unique structure features highly delocalized π-electron systems within the extended chains, which is responsible for the low effective mass and narrow electronic bandgap. Thus, the temperature-dependent charge-transport properties of q2DPPy are investigated using the van der Pauw (vdP) method and terahertz time-domain spectroscopy (THz-TDS). The vdP method reveals that the q2DPPy film exhibits a semiconducting behavior with a thermally activated hopping mechanism in long-range transport between the electrodes. Conversely, THz-TDS reveals a band-like transport, indicating intrinsic charge transport up to a record short-range high THz mobility of ≈107.1 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup> .