New Semiconducting Polymers Based on Benzobisthiadiazole Analogues: Tuning of Charge Polarity in Thin Film Transistors via Heteroatom Substitution

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• 作者：Yang Wang ; Hiroyasu Masunaga ; Takaaki Hikima ; Hidetoshi Matsumoto ; Takehiko Mori ; Tsuyoshi Michinobu
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：48
• 期：12
• 页码：4012-4023
• 全文大小：807K
• ISSN：1520-5835

文摘

As one of the most effective molecular design strategies in organic electronics, heteroatom substitution was employed for the first time to study the acceptor variation effects on the optical, electrochemical, molecular assembling, and charge-transport properties of novel semiconducting polymers containing benzobisthiadiazole (BBT)-related heterocycles, namely, poly(dithiazolfluorene-alt-thiadiazolobenzotriazole) (PSN), poly(dithiazolfluorene-alt-selenadiazolobenzotriazole) (PSeN), and poly(dithiazolfluorene-alt-selenadiazolobenzothiadiazole) (PSeS). The effect of the heteroatom substitution was clearly shown in the UV鈥搗is鈥揘IR absorption spectra in which the substitution of the sulfur (S) and/or nitrogen (N) atoms in PSN with the selenium (Se) and sulfur (S) atoms led to a red-shift in the absorption profile. In addition, the energy levels of these polymers, determined from cyclic voltammetry (CV) measurements and density functional theory (DFT) calculations, also varied due to the hetroatom substitution effect. Accordingly, thin film transistors (TFTs) based on these polymers showed different charge transport properties. For example, PSN displayed p-type unipolar performances with a high hole mobility up to 0.65 cm² V^鈥? s^鈥?. In contrast, PSeS showed n-type dominant charge transport properties with an electron mobility up to 0.087 cm² V^鈥? s^鈥?. Intriguingly, PSeN exhibited ambipolar charge transport properties with balanced 渭_h and 渭_e values. These different charge polarities in the TFTs were correlated to the energy levels, 蟺鈥撓€ stacking distances, and polymer crystallinities evaluated by their grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns and atomic force microscopy (AFM) images. We believe that this simple and effective approach will guide the way to developing high-performance ambipolar and/or n-channel semiconducting polymers for TFTs.