Novel Chemical Route to Prepare a New Polymer Blend Gate Dielectric for Flexible Low-Voltage Organic Thin-Film Transistor

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• 作者：Jagan Singh Meena ; Min-Ching Chu ; Yu-Cheng Chang ; Chung-Shu Wu ; Chih-Chia Cheng ; Feng-Chih Chang ; Fu-Hsiang Ko
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2012
• 出版时间：June 27, 2012
• 年：2012
• 卷：4
• 期：6
• 页码：3261-3269
• 全文大小：473K
• 年卷期：v.4,no.6(June 27, 2012)
• ISSN：1944-8252

文摘

An organic鈥搊rganic blend thin film has been synthesized through the solution deposition of a triblock copolymer (Pluronic P123, EO₂₀鈥揚O₇₀鈥揈O₂₀) and polystyrene (PS), which is called P123鈥揚S for the blend film whose precursor solution was obtained with organic additives. In addition to having excellent insulating properties, these materials have satisfied other stringent requirements for an optimal flexible device: low-temperature fabrication, nontoxic, surface free of pinhole defect, compatibility with organic semiconductors, and mechanical flexibility. Atomic force microscope measurements revealed that the optimized P123鈥揚S blend film was uniform, crack-free, and highly resistant to moisture absorption on polyimide (PI) substrate. The film was well-adhered to the flexible Au/Cr/PI substrate for device application as a stable insulator, which was likely due to the strong molecular assembly that includes both hydrophilic and hydrophobic effects from the high molecular weights. The contact angle measurements for the P123鈥揚S surface indicated that the system had a good hydrophobic surface with a total surface free energy of approximately 19.6 mJ m^鈥?. The dielectric properties of P123鈥揚S were characterized in a cross-linked metal鈥搃nsulator鈥搈etal structured device on the PI substrate by leakage current, capacitance, and dielectric constant measurements. The P123鈥揚S film showed an average low leakage current density value of approximately 10^鈥?0 A cm^鈥? at 5鈥?0 MV cm^鈥? and large capacitance of 88.2 nF cm^鈥? at 1 MHz, and the calculated dielectric constant was 2.7. In addition, we demonstrated an organic thin-film transistor (OTFT) device on a flexible PI substrate using the P123鈥揚S as the gate dielectric layer and pentacene as the channel layer. The OTFT showed good saturation mobility (0.16 cm² V^鈥? s^鈥?) and an on-to-off current ratio of 5 脳 10⁵. The OTFT should operate under bending conditions; therefore flexibility tests for two types of bending modes (tensile and compressive) were also performed successfully.

Keywords:

flexible electronics; polymer gate dielectrics; polystyrene; pentacene; block copolymer; organic thin-film transistor