Study of new solution-processable gate dielectric layer for flexible organic thin film transistors
| Autor: | Tsai, I-Hsin, 蔡毅昕 |
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| Rok vydání: | 2014 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 Organic thin film transistors (OTFTs) are an important class of electronic devices owing to their easy processability, light weight and flexibility. They also offer a better understanding of the material properties as used in it through structure property relationship study. It can be foreseen that this new technology can play a leading role in the future studies for commercialization of electronic devices based on OTFTs. In this study, we have utilized the organic materials to fabricate flexible devices namely, metal-insulator-metal (MIM) capacitor and organic thin-film transistor (OTFT) by simple solution process. In this study, we have analyzed the potential of dielectric material PAN (Polyacrylonitrile) and PS (Polystyrene)-P123 (Pluronic® P123 Block Copolymer Surfactant) through fabrication of metal insulator metal capacitor devices. Sol gel process and spin coating techniques are applied to deposit PAN and PS-P123 dielectric layer. We have demonstrated several parameters of PAN layer fabrication conditions like solubility, concentration and annealing. After extracting best conditions from this part, we drop casted a PS-P123 layer penultimate to the PAN layer which has acted as a buffer region. This bilayer dielectric strategy has prevented the direct contact between organic semiconductor and the high k dielectric PAN, and provided a lower surface energy. The capacitor with bilayer structure have attained better electrical performance and reliability as compared to their monolayer counterparts. FTIR and contact angle analysis study has further revealed other interesting properties of the polymer dielectric materials. The conditions for fabrication of PAN and PS-P123 based bilayer dielectric was optimized before employing it further as a gate dielectric in OTFT based on DH4T (α,ω-dihexylquaterthiophene) as an active semiconducting layer. The OTFTs devices are fabricated on the flexible polyimide (PI) substrate. The best electrical performance was acquired by drop-casting the DH4T solution on PI substrate followed by annealing at 90 oC for 30 min. The ON/OFF ratio can attain 103, and the mobility is at the order of 10-2, which is comparable to the reported researches. Different top contact metals electrode are also tested, and the Ag and Au are found to be the better candidate. Several bending situation are applied, to explore the charge carrier hopping mechanism involved in deterioration of electrical properties of OTFTs. Finally, reliability experiments are conducted, which revealed that the electrical performance of OTFTs was deteriorated after five days, but the electric property can be recovered by means of re-baking the devices at the temperature of 90 oC. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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