posted on 2023-12-08, 17:06authored byAesun Kim, Yooseong Ahn, Wenhao Li, Su Hong Park, Min Ju Cho, Dong Hoon Choi, Hoichang Yang
Diketopyrrolopyrrole (DPP)-based conjugated copolymers
are important
organic semiconductors for applications in high-efficiency organic
thin-film transistors (OTFTs). However, the direct application of
these polymers with rigid backbones in stretchable devices has limitations.
In this study, we designed and synthesized three kinds of DPPBT-based
copolymers, DPPBT-A1, DPPBT-A3, and DPPBT-A5, which have amide-coupled
alkylene conjugation breakers capable of hydrogen bonding. Linkers
with different segment lengths were copolymerized with DPP and bithiophene
(BT) backbone units. A DPP-based copolymer with alternating BT moieties,
DPPBT, was synthesized as a reference fully conjugated copolymer.
The synthesized polymers with freely rotational backbone linkers have
sufficient flexibility to develop ordered phase domains, even in thin
films, in comparison to the reference copolymer. However, the introduction
of the conjugation breakers, which disconnect the intramolecular π–π
overlapping, tends to decrease the hole mobility (μ) from 0.76
to 0.20 cm2 V–1 s–1 in the corresponding OTFT devices. The TFT fabricated using DPPBT-A3
showed a mobility of 0.50 cm2 V–1 s–1, and the mobility value did not show a significant
change even when elongated by more than 50%. Therefore, the molecular
design strategy of introducing amide-coupled alkylene conjugation
breakers into conjugated polymer chains can contribute significantly
to the development of high-mobility stretchable conjugated polymers
in future.