While high-mobility p-type conjugated polymers have been widely reported, high-mobility n-type conjugated polymers are still rare. In the present work, we designed semifluorinated alkyl side chains and introduced them into naphthalene diimide-based polymers (PNDIF-T2 and PNDIF-TVT). We found that the strong self-organization of these side chains induced a high degree of order in the attached polymer backbones by forming a superstructure composed of “backbone crystals” and “side-chain crystals”. This phenomenon was shown to greatly enhance the ordering along the backbone direction, and the resulting polymers thus exhibited unipolar n-channel transport in field-effect transistors with remarkably high electron mobility values of up to 6.50 cm2 V–1 s–1 and with a high on–off current ratio of 105.
Polymer semiconductors, which can be processed on large-area and mechanically flexible substrates with low cost, are considered as one of the main components for future plastic electronics. However, they, especially n-type semiconducting polymers, currently lag behind inorganic counterparts in the charge carrier mobility – which characterizes how quickly charge carriers (electron) can move inside a semiconductor – and the chemical stability in ambient air.
Recently, a joint research team has developed a new n-type semiconducting polymer with superior electron mobility and oxidative stability. The team modified a n-type conjugated polymer with semi-fluoroalkyl side chains – which are found to have several unique properties, such as hydrophobicity, rigidity, thermal stability, chemical and oxidative resistance, and the ability to self-organize. As a result, the modified polymer was shown to form a superstructure composed of polymer backbone crystals and side-chain crystals, resulting in a high degree of semicrystalline order. The team explained this phenomenon is attributed to the strong self-organization of the side chains and significantly boosts charge transport in polymer semiconductors.
Prof. Cho emphasized “We investigated the effects of semi-fluoroalkyl side chains of conjugated polymers at the molecular level and suggested a new strategy to design highly-performing polymeric materials for next-generation plastic electronics.” http://www.eurekalert.org/pub_releases/2016-04/puos-rdn042016.php
http://pubs.acs.org/doi/abs/10.1021/jacs.5b10445
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