（A）電子受體-異芳香環次甲基共軛高分子之理論電子結構特性分析;（B）結合笏體和電子施體-電子受體-電子施體之共聚合物之合成與其在薄膜電晶體的應用

Abstract

中文摘要 共軛高分子的電子結構和電子特性可藉由改變其化學結構來做調整。在這份論文中，有兩個討論被提出來探討以瞭解化學結構對共軛高分子電子特性的影響。（A）電子受體-異芳香環次甲基共軛高分子之結構和電子特性之理論分析 ;（B）結合笏體和電子施體-電子受體-電子施體之共聚合物之合成與其在薄膜電晶體的應用。 在這份研究的第一部份，藉由density functional theory 探索關於電子受體-異芳香環次甲基共軛高分子之結構和電子特性之關連的全面性瞭解並將最佳化結構：鍵長變化、兩面夾角與電子性質，例如：HOMO、LUMO、能隙和傳導帶寬做連結。結果顯示相對於其單聚合高分子，異芳香環次甲基共軛高分子有較小的能隙是因為aromatic 和 quinoid 型態能夠在共軛鍊上共存，或者是因為擁有較低的LUMO能階所導致。而異芳香環次甲基共軛高分子的幾何結構被許多因素影響，包含雜環的大小、側鏈基、異原子。電子特性，含HOMO、LUMO、能隙和傳導帶寬也深受兩面夾角、鍵長變化、電子受體強度控制。較小的鍵長變化和較強的電子受體強度都會導致較小的能隙。 在這份研究的第二部份，我們合成笏體和電子施體-電子受體-電子施體之共聚合物並將其應用在薄膜電晶體上。這共聚合物是透過Suzuki coupling反應合成。因為分子內強的電子轉移，由儀器UV-vis和CV所得到PFO-DTTP的光學和電化學性質可得到的能隙分別為1.67 和1.82 eV。此外，由PFO-DTTP在溶劑DCB中配置的薄膜傳導體有field-effect mobility高達1.38*10-5 cm2/Vs和最大on/off ration（5.91*103），這些數據相較於常用來置備薄膜傳導體的物質F8T2都有較佳的結果。這顯示了在電晶體中有顯著的分子內電子轉移。

Abstract 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.