Improving Ambipolar Semiconducting Properties of Thiazole-Flanked
Diketopyrrolopyrrole-Based Terpolymers by Incorporating Urea Groups
in the Side-Chains
Two new ambipolar thiazole-flanked
diketopyrrolopyrrole-based polymers
pDPPTz2T-1 and pDPPTz2T-2 with urea-containing linear side-chains
were prepared. The formation of hydrogen bonding enhanced the ambipolar
semiconducting properties, including mobilities and on/off ratios.
The average mobilities (hole and electron) of pDPPTz2T-2 were 25 and
3 times higher than those of pDPPTz2T without urea groups, whereas
the average on/off ratios (Ion/Ioff) for hole and electron were 100 and 4 times
higher than those obtained for pDPPTz2T. Thin-film microstructure
studies reveal that incorporating urea groups into polymer side-chains
can enhance interchain packings, including the alkyl chain lamellar
and π–π stackings. Our results clearly show how
incorporating urea groups in side-chains significantly influence semiconducting
properties, which could be extended to other conjugated systems toward
ambipolar and even n-type FETs.