Approaching Intra- and Interchain Charge Transport of Conjugated Polymers Facilely by Topochemical Polymerized Single Crystals

Charge transport of small molecules is measured well with scanning tunneling microscopy, conducting atomic force microscopy, break junction, nanopore, and covalently bridging gaps. However, the manipulation and measurement of polymer chains remain a long-standing fundamental issue in conjugated polymers and full of challenge since conjugated polymers are naturally disordered materials. Here, a fundamental breakthrough in generating high-quality conjugated-polymer nanocrystals with extended conjugation and exceptionally high degrees of order using a surface-supported topochemical polymerization method is demonstrated. In the crystal the conjugated-polymer chains are extended along the long axis of the crystal with the side chains perpendicular to the long axis. Devices with conducting channels along the polymer chains show efficient charge transport, nearly two orders of magnitude greater than the interchain charge transport along the π–π stacking direction. This is the first example to clarify intra- and interchain charge transport based on an individual single crystal of conjugated polymers, and demonstrate the importance of intrachain charge transport in plastic electronics.

High-quality conjugated-polymer crystals with extended conjugation and exceptionally high degree of molecular order are obtained through a modified topochemical polymerization method. For the first time, the fundamental studies of intra- and interchain charge transport based on an individual polymer crystal are approached, giving a high carrier mobility up to 50 cm² V⁻¹ s⁻¹ along the backbones, which is two orders of magnitude greater than that in the interchain direction.

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