Thienopyrazine電子施體-受體共軛高分子之合成、性質及其光電元件應用

Abstract

電子施體/受體共軛高分子在最近幾年被廣泛的研究。 藉由選擇不同的施體和受體,共軛高分子具有不同電子和光學特性。 因此共軛高分子在發光二極體，太陽能電池和薄膜電晶體上有廣泛應用。 然而，以thienopyrazine為主的電子施體-電子受體和電子施體-電子受體-電子施體共軛高分子在薄膜電晶體上的應用尚未深入的研究。此論文目標主要是以成thienopyrazine結構為主之共軛高分子合成，光電性質分析和在薄膜電晶體上的應用。 在第二章，合成新穎的thienopyrazine和電子施體的共軛高分子材料。四種共軛高分子均具有良好的溶解度，光學性質在薄膜狀態下具有寬廣的吸收，其最大吸收峰約在540到950nm左右，其中以PTPTP的能隙為最小，表示具有較強的分子內電荷傳遞。其電化學性質均具有低游離能 (4.57-4.99eV) 和高電子親和力(3.26-3.49eV)。 PDPTP、PCPTP和PTPTP的電洞遷移率分別為2.62×10-6、2.74×10-5和2.00×10-4 cm2V-1s-1。 PTPTP具有最高的電洞遷移率是因為有較低的能隙和較強的分子內電荷轉移。由原子力顯微鏡可知共軛高分子在薄膜狀態下均為平滑和無定形的。 因此，分子內電荷傳遞可能是主要影響電洞遷移率的因素。 在第三章，合成以thienopyrazine為主的電子施體-電子受體-電子施體的共軛高分子。從薄膜狀態的吸收光譜圖中可知，三種共軛高分子具有寬廣的吸收範圍延伸到紅外光區且具有小的能隙 (1.15-1.57eV)。在電化學循環伏安法均具有可逆的氧化還原和低游離能 (4.62-4.98 eV)。PDDTTP、PFDTTP和PDTTP的電洞遷移率分別為7.24×10-4、1.61×10-3和1.16×10-3cm2V-1s-1。 従原子力顯微鏡中，可發現PFDTTP具有較平滑且無定形的型態，因此其電洞遷移率為最高。從上述結果可知thienopyrazine為主的電子施體-電子受體-電子施體的共軛高分子兼具有廣的吸收範圍且高的電洞遷移率。因此，這三種共軛高分子在薄膜電晶體跟太陽能電池材料的應用上，具有不錯潛力。

Donor-acceptor conjugated polymers have been widely investigated in recent years. By optimization of donor and acceptor structures, the conjugated copolymers can exhibit broad absorption from visible region to near-infrared range for electronic and optoelectronic applications, such as light-emitting diodes, photovoltaic cells, and thin film transistor. However, the electronic and optoelectronic properties of thienopyrazine-based conjugated polymers have not been fully explored yet. The goal of this thesis is to investigate the effects of donor-acceptor or donor-acceptor-donor structures on the electronic properties of thienopyrazine based conjugated polymers. In chapter 2, the optical, electrochemical, and field effect charge transport properties of the new thienopyrazine-based alternating donor-acceptor conjugated copolymers were explored. The new copolymers, Poly[5-(2,5-bis(decyloxy)phenyl)-2,3- bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PDPTP), Poly[5-(9,9-dioctyl- 9H-fluoren-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PFPTP), Poly[5-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PCPTP) and Poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5-(thiophen-2-yl) thieno[3,4-b]pyrazine] (PTPTP) had excellent solubility and broad optical absorption bands with absorption maxima at 540-950nm in thin film. The PTPTP exhibits the smallest band gap (0.98eV), indicating a stronger intramolecular charge transfer. The four polymers show the low ionization potentials (4.57-4.99 eV) and high electron affinity (3.26-3.49eV). The hole mobilities of PDPTP, PCPTP, and PTPTP are 2.62×10-6, 2.74×10-5, and 2.00×10-4 cm2V-1s-1. PTPTP has the highest hole mobility due to low band gap and strong intramolecular charge transfer.The AFM topographic images of the copolymers show smooth and amorphous phases. From these results, intramolecular charge transfer might be main impact on hole mobility. In chapter 3, thienopyrazine-based donor-acceptor-donor alternating conjugated copolymers were synthesized. The copolymers including Poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PDDTTP), Poly[5-(5-(9,9- dioctyl-9H-fluoren-2-yl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(thiophen-2-yl)thieno[3,4-b]pyrazine] (PFDTTP), and Poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5 ,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine] (PDTTP) exhibit broad optical absorption bands (662-816nm) and small optical band gaps (1.15-1.57eV). All polymers exhibit reversible oxidation and reduction and low ionization potential (4.62-4.98 eV). The hole mobility of PDDTTP, PFDTTP, and PDTTP are 7.24×10-4, 1.61×10-3 and 1.16×10-3cm2V-1s-1. The hole mobility of PFDTTP is the highest probably due to the relatively smooth and amorphous phase in thin film. According to these results, thienopyrazine-based donor-acceptor-donor copolymers combine small band gap and high carrier mobility. Such polymers may have potential optoelectronic device applications, such as thin film transistor and photovoltaic cells.