A series of new π-conjugated D–A copolymers PDMOTT-n (n = 118, 122, 320, and 420) containing a diketopyrrolopyrrole unit and a 3,6-dimethoxythieno[3,2-b]thiophene moiety was designed and synthesized, and their field-effect properties were characterized. The polymers PDMOTT-n have a low bandgap of 1.27 eV and exhibit a broad absorption. Solution-processed field-effect transistors based on these polymers were fabricated with a bottom-gate/bottom-contact configuration and demonstrated typical p-type charge transporting properties. Of these, PDMOTT-420 with the longest alkyl side chains and having the longest distance between the branching point of the alkyl side chain and π-conjugated backbone of the polymer, exhibited the best carrier transporting performance with a hole mobility of 2.01 cm² V⁻¹ s⁻¹ and with an on/off current ratio of 10⁴–10⁵. The characterization results of grazing incidence X-ray diffraction and tapping-mode atomic force microscopy showed that the thin film of the polymer PDMOTT-420 forms larger grains and more useful nanofibrillar intercalated structures and owns shorter π–π stacking distance and better crystallization than those of another three polymers. These results could help us to better understand the structure–property relationship of polymer semiconductors and to design novel π-conjugated polymers for high-performance field-effect transistors.

中文翻译：

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由低带隙DPP基半导体材料制成的高性能聚合物场效应晶体管†

一系列新的π共轭d-A的共聚物PDMOTT- Ñ（Ñ = 118，122，320，和420）含有二酮吡咯并吡咯单元和3,6- dimethoxythieno并[3,2- b ]噻吩基部分被设计并合成，并对其场效应性质进行了表征。聚合物PDMOTT- n具有1.27 eV的低带隙，并显示出较宽的吸收率。基于这些聚合物的溶液处理的场效应晶体管采用底栅/底接触配置制造，并展现出典型的p型电荷传输特性。其中，PDMOTT-420烷基侧链最长，烷基侧链的支化点与聚合物的π共轭主链之间的距离最大的分子，表现出最佳的载流子传输性能，空穴迁移率为2.01 cm ² V ^-1 s ^-1和开/关电流比为10 ⁴ –10 ⁵。掠入射X射线衍射和振型原子力显微镜的表征结果表明，聚合物PDMOTT-420的薄膜形成更大的晶粒和更有用的纳米原纤维插层结构，并且比其他三种聚合物拥有更短的π-π堆积距离和更好的结晶性。这些结果可以帮助我们更好地理解聚合物半导体的结构-性质关系，并设计出用于高性能场效应晶体管的新型π共轭聚合物。