Side chain engineering of cyclopentadithiophene based conjugated polymers for high-performance organic thin-film transistors
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Conjugated polymers based on cyclopentadithiophene (CPDT) moieties widely used in optoelectronic devices are rarely applicated in thin-film transistors (TFTs). This is because the steric hindrance at the tetrahedral center of the CPDT core deteriorates the polymer crystallinity and solubility. In this work, high-mobility conjugated copolymers based on CPDT are synthesized through side chain engineering of the polymers. The addition of bulky ethylhexyl side chains to CPDT does not interfere with the molecular ordering when linear alkyl side chains based on co-monomeric moieties are combined. The polymer shows excellent π–π interactions, good solubility, and bimodal orientated packing structure with strong intercalation of linear alkyl side chains in the thin film states. As a result, the optimized TFTs achieve the hole mobilities of 1.08–1.64 cm2 V−1 s−1, which are the highest mobilities among the reported CPDT based conjugated polymers with branched alkyl side chains.