The charge-carrier mobility of organic semiconducting polymers is known
to be enhanced when the energetic disorder of the polymer is minimized.
Fused, planar aromatic ring structures contribute to reducing the polymer
conformational disorder, as demonstrated by polymers containing the
indacenodithiophene (IDT) repeat unit, which have both a low Urbach energy
and a high mobility in thin-film-transistor (TFT) devices. Expanding on this
design motif, copolymers containing the dithiopheneindenofluorene repeat unit
are synthesized, which extends the fused aromatic structure with two additional
phenyl rings, further rigidifying the polymer backbone. A range of copolymers
are prepared and their electrical properties and thin-film morphology evaluated,
with the co-benzothiadiazole polymer having a twofold increase in hole mobility
when compared to the IDT analog, reaching values of almost 3 cm2 V−1 s−1 in
bottom-gate top-contact organic field-effect transistors.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank KAUST and BASF for financial support and
acknowledge EC FP7 Project SC2 (610115) EC H2020 Project
SOLEDLIGHT (643791), and EPSRC Projects EP/G037515/1 and
EP/M005143/1. M.N. and H.S. acknowledge financial support from
the Engineering and Physical Sciences Research Council through a
Programme Grant (EP/M005141/1). M.A.J. gratefully acknowledges
Nava Technology Limited for a Ph.D. scholarship. The authors also
thank Mr. James Fraser for the help of synthesizing several intermediates
and Dr. Aditya Sadhanala for help with PDS measurements. C.R.M.
also acknowledges support from the Australian Research Council
(DP130102616). This research was undertaken in part on the SAXS/
WAXS beamline at the Australian Synchrotron, Victoria, Australia.