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One of the outstanding challenges in the field of organic
semiconductors, in particular those of macromolecular nature, is
the establishment of the relationship between their structure and
transport properties. One of the potential advantages of polymer
semiconductors in comparison with low-molecular weight systems
is the possibility to achieve particularly extensive charge delocalization
(and thus fast transport pathways) along the conjugated
polymer backbone. This advantage became particularly clear with
the development of regioregular poly(3-hexylthiophenes) (RRP3HTs),
which, owing to their regioregularity, have a high tendency
to self-assemble into highly ordered, partially crystalline structures
which facilitate high conjugation and result in dramatic improvement
of field effect mobility.
Herein we demonstrated that the careful
choice of processing conditions of RR-P3HTs with narrow polydispersities
can lead to the formation of very well-defined nanofibrillar
morphologies in which the width of the nanofibrils corresponds
very closely to the weight average contour length of polymer chains.
Moreover, we show that the charge carrier mobility in field effect
transistors (FETs) fabricated from these well-ordered polymers
increases exponentially with the nanofibril width. This remarkable correlation appears to
directly point to the prominent role of extended, conjugated states
in the charge transport in semiconducting polymers.
Zhang, R., et. al, J. Am. Chem. Soc. 2006, 128 (11), 3480 -3481 |
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Phase contrast TMAFM image of RR-P3HT nanofibril transistor thin film and schematic model of nanofibril
GISAXS patterns of RR-P3HT nanofibril thin film
Exponential dependence of transistor field-effect mobility on nanofibril widths
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