We
demonstrate a simple, but efficient, approach for improving
the semiconducting performances of DPP-based conjugated D-A polymers.
This approach involves the replacement of one bulky branching alkyl
chain with the linear one at each DPP unit in regular polymer PDPPSe-10
and PDPPSe-12. The UV–vis absorption, Raman spectra, PDS data,
and theoretical calculations support that the replacement of bulky
branching chains with linear ones can weaken the steric hindrance,
and accordingly conjugated backbones become more planar and rigid.
GIWAXS data show that the incorporation of linear alkyl chains as
in PDPPSe-10 and PDPPSe-12 is beneficial for side-chain interdigitation
and interchain dense packing, leading to improvement of interchain
packing order and thin film crystallinity by comparing with PDPPSe,
which contains branching alkyl chains. On the basis of field-effect
transistor (FET) studies, charge mobilities of PDPPSe-10 and PDPPSe-12
are remarkably enhanced. Hole mobilities of PDPPSe-10 and PDPPSe-12
in air are boosted to 8.1 and 9.4 cm2 V–1 s–1, which are about 6 and 7 times, respectively,
than that of PDPPSe (1.35 cm2 V–1 s–1). Furthermore, both PDPPSe-10 and PDPPSe-12 behave
as ambipolar semiconductors under a nitrogen atmosphere with increased
hole/electron mobilities up to 6.5/0.48 cm2 V–1 s–1 and 7.9/0.79 cm2 V–1 s–1, respectively.