Influence of Semiconductor Thickness and Molecular Weight on the Charge Transport of a Naphthalenediimide-Based Copolymer in Thin-Film Transistors

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• 作者：Yevhen Karpov ; Wei Zhao ; Ivan Raguzin ; Tetyana Beryozkina ; Vasiliy Bakulev ; Mahmoud Al-Hussein ; Liane H盲u脽ler ; Manfred Stamm ; Brigitte Voit ; Antonio Facchetti ; Roman Tkachov ; Anton Kiriy
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：June 17, 2015
• 年：2015
• 卷：7
• 期：23
• 页码：12478-12487
• 全文大小：478K
• ISSN：1944-8252

文摘

The N-type semiconducting polymer, P(NDI2OD-T2), with different molecular weights (MW = 23, 72, and 250 kg/mol) was used for the fabrication of field-effect transistors (FETs) with different semiconductor layer thicknesses. FETs with semiconductor layer thicknesses from 鈭?5 to 50 nm exhibit similar electron mobilities (渭鈥檚) of 0.2鈥?.45 cm² V^鈥? s^鈥?. Reduction of the active film thickness led to decreased 渭 values; however, FETs with 鈭? and 鈭? nm thick P(NDI2OD-T2) films still exhibit substantial 渭鈥檚 of 0.01鈥?.02 and 鈭?0^鈥? cm² V^鈥? s^鈥?, respectively. Interestingly, the lowest molecular weight sample (P-23, MW 鈮?23 kg/mol, polydispersity index (PDI) = 1.9) exhibited higher 渭 than the highest molecular weight sample (P-250, MW 鈮?250 kg/mol, PDI = 2.3) measured for thicker devices (15鈥?0 nm). This is rather unusual behavior because typically charge carrier mobility increases with MW where improved grain-to-grain connectivity usually enhances transport events. We attribute this result to the high crystallinity of the lowest MW sample, as confirmed by differential scanning calorimetry and X-ray diffraction studies, which may (over)compensate for other effects.