Title: Novel Chemical Route to Prepare a New Polymer Blend Gate Dielectric for Flexible Low-Voltage Organic Thin-Film Transistor
Authors: Meena, Jagan Singh
Chu, Min-Ching
Chang, Yu-Cheng
Wu, Chung-Shu
Cheng, Chih-Chia
Chang, Feng-Chih
Ko, Fu-Hsiang
Department of Materials Science and Engineering
Department of Applied Chemistry
Keywords: flexible electronics;polymer gate dielectrics;polystyrene;pentacene;block copolymer;organic thin-film transistor
Issue Date: 1-Jun-2012
Abstract: An organic-organic blend thin film has been synthesized through the solution deposition of a triblock copolymer (Pluronic P123, EO20-PO70-EO20) and polystyrene (PS), which is called P123-PS 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-PS 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-PS surface indicated that the system had a good hydrophobic surface with a total surface free energy of approximately 19.6 mJ m(-2). The dielectric properties of P123-PS were characterized in a cross-linked meta-insulator-metal structured device on the PI substrate by leakage current, capacitance, and dielectric constant measurements. The P123-PS film showed an average low leakage current density value of approximately 10(-10) A cm(-2) at 5-10 MV cm(-1) and large capacitance of 88.2 nF cm(-2) 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-PS as the gate dielectric layer and pentacene as the channel layer. The OTFT showed good saturation mobility (0.16 cm(2) V-1 s(-1)) and an on-to-off current ratio of 5 x 10(5). The OTFT should operate under bending conditions; therefore flexibility tests for two types of bending modes (tensile and compressive) were also performed successfully.
URI: http://hdl.handle.net/11536/16503
ISSN: 1944-8244
Volume: 4
Issue: 6
End Page: 3261
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