PART A: Theoretical Analysis on the Geometry and Electronic Properties of Acceptors-based Poly(heteroarylene methine)sPART B: Synthesis and Characterization of New Fluorene-based Donor-acceptor-Donor Alternating Copolymers for Transistor Applications
| Autor: | Jen-Fu Wang, 王仁甫 |
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| Rok vydání: | 2006 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 94 The electronic structures and electronic properties of conjugated polymers have been tuned by modifying the chemical structures in many studies for specific aims. In this study, we divide two parts to discuss: (A) theoretical analysis on the geometries and electronic properties of acceptors-based poly(heteroarylene methine)s, and (B) synthesis the fluorene-based copolymers with donor-acceptor-donor systems(1:1) and their application on the thin-film transistors. In the PART A of this study, a comprehensive understanding on the relationship between theoretical geometries and electronic properties of acceptor-based poly(heteroarylene methine)s was explored by the density functional theory (DFT) at the B3LYP level with 6-31G basis set. The optimized geometries: bond length alternation and dihedral angle were investigated and correlated with the electronic properties: HOMO, LUMO, band gap and bandwidth. The results suggested that poly(heteroarylene methine)s had smaller band gap relative to the their homopolymers, due to the coexistence of aromatic and quinoid form and the lower LUMO energy levels. The geometries of these poly(heteroarylene methine)s were significantly affected by the fused ring size, side groups, and heteroatoms. The electronic properties of HOMO, LUMO, band gap and bandwidth were significantly controlled by the dihedral angle, bond length alternation, and the acceptor strength. The smaller bond length alternation and stronger acceptor strength result in the smaller band gap. In the PART B of this study, we synthesize the fluorene-based donor-acceptor-donor copolymer for thin film transistor applications. The copolymer was synthesized through the palladium-catalyzed Suzuki coupling reaction. The optical and electrochemical properties of PFO-DTTP determined by UV-vis and CV suggest small band gaps of 1.82 and 1.67 eV, respectively, due to the strong intramolecular charge transfer. Beside, the thin film transistor device fabricated by PFO-DTTP in DCB has field-effect mobility of 1.38*10-5 cm2/(Vs) and the maximum on/off ration observed of 5.91*103, which is slightly higher than the common TFT materials of F8T2. It suggests the significance of intramolecular charge transfer on the transistor characteristics. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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