Fluorinated Benzothiadiazole (BT) Groups as a Powerful Unit for High-Performance Electron-Transporting Polymers

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• 作者：Junghoon Lee ; Moonjeong Jang ; Sang Myeon Lee ; Dohyuk Yoo ; Tae Joo Shin ; Joon Hak Oh ; Changduk Yang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：November 26, 2014
• 年：2014
• 卷：6
• 期：22
• 页码：20390-20399
• 全文大小：540K
• ISSN：1944-8252

文摘

Over the past few years, one of the most remarkable advances in the field of polymer solar cells (PSCs) has been the development of fluorinated 2,1,3-benzothiadiazole (BT)-based polymers that lack the solid working principles of previous designs, but boost the power conversion efficiency. To assess a rich data set for the influence of the fluorinated BT units on the charge-transport characteristics in organic field-effect transistors (OFETs), we synthesized two new polymers (PDPP-FBT and PDPP-2FBT) incorporating diketopyrrolopyrrole (DPP) and either single- or double-fluorinated BT and thoroughly investigated them via a range of techniques. Unlike the small differences in the absorption properties of PDPP-FBT and its nonfluorinated analogue (PDPP-BT), the introduction of doubly fluorinated BT into the polymer backbone induces a noticeable change in its optical profiles and energy levels, which results in a slightly wider bandgap and deeper HOMO for PDPP-2FBT, relative to the others. Grazing incidence X-ray diffraction (GIXD) analysis reveals that both fluorinated polymer films have long-range orders along the out-of-plane direction, and 蟺鈥撓€ stacking in the in-plane direction, implying semicrystalline lamellar structures with edge-on orientations in the solid state. Thanks to the strong intermolecular interactions and highly electron-deficient 蟺-systems driven by the inclusion of F atoms, the polymers exhibit electron mobilities of up to 0.42 and 0.30 cm² V^鈥? s^鈥? for PDPP-FBT and PDPP-2FBT, respectively, while maintaining hole mobilities higher than 0.1 cm² V^鈥? s^鈥?. Our results highlight that the use of fluorinated BT blocks in the polymers is a promising molecular design strategy for improving electron transporting performance without sacrificing their original hole mobility values.

Keywords:

n-channel dominant FET; fluorinated benzothiadiazole; diketopyrrolopyrrole; fluorine; organic field-effect transistors (OFET)