苯并雙三唑拉電子基與噻吩系列推電子基之共軛高分子之合成與鑑定及其在有機場效電晶體之應用

Abstract

本研究使用苯并雙三唑 (benzo[1,2-d:4,5-d']bis([1,2,3]triazole), BBTa) 拉電子基與不同之噻吩 (thiophene) 系列推電子基合成出三個共軛高分子PBTBBTa-BT, PBTBBTa-TT and PBTBBTa-TVT 並作為材料應用於有機場效電晶體 (OFETs) 中。藉由將苯并雙噻二唑 (benzobisthiadiazole, BBT) 結構中的硫原子置換成氮原子，所得到之苯并雙三唑可將增加溶解度之長碳鏈接在其氮原子上，而不是接在高分子主鏈之噻吩上，如此一來可以降低單體間的立體障礙並使高分子之平面性提升。苯并雙三唑作為一電子受體首先與常見之電子施體二噻吩 (2,2'-bithiophene, BT) 做聚合；接下來將電子施體換成平面性較佳的噻吩並噻吩 (thieno[3,2-b]thiophene, TT)，以提升高分子之平面性；最後選擇在二噻吩中插入雙鍵成為噻吩乙烯噻吩 ((E)-2-(2-(thiophen-2-yl)vinyl)thiophene, TVT) 以增加其共軛長度。 我們分別鑑定及分析了三個材料之光學性質、熱性質與電化學性質，同時也利用理論計算來模擬出高分子之最佳分子構型；最後使用 GIWAXS 與 AFM 來探討高分子膜之結構排列與表面形貌。三個高分子皆有良好之熱穩定性並表現出 p-type 之電性，有機場效電晶體元件採用的是底閘極上接觸結構 (bottom gate-top contact，BG-TC)，在調控退火溫度與時間後 PBTBBTa-BT, PBTBBTa-TT 與 PBTBBTa-TVT 所得到之最高電洞遷移率分別為 0.22 cm2 V-1 s-1、0.13 cm2 V-1 s-1 與 3.1×10-2 cm2 V-1 s-1。

In this study, we synthesized three D-A conjugated copolymers PBTBBTa-BT, PBTBBTa-TT and PBTBBTa-TVT based on benzo[1,2-d:4,5-d']bis([1,2,3]triazole) (BBTa) acceptor unit and combined with three different donor units. The obtained polymers were used in organic field-effect transistors (OFETs). By replacing the sulfur atoms in benzobisthiadiazole (BBT) with nitrogen atoms, the benzobistriazole can possess alkyl chains on the central nitrogen atoms rather than on the thiophene rings along the polymer chain, which can reduce the steric hindrance between neighboring monomers and increase the planarity of polymers. The BBTa acceptor unit was copolymerized with donor units 2,2'-bithiophene (BT) first. Next we selected a more planar donor unit thieno[3,2-b]thiophene (TT) to enhance the planarity of polymer chain. (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) with longer conjugation length was chosen as the third donor unit. The optical, thermal and electrochemical properties of the three polymers were characterized respectively. We also used DFT calculations to calculate the optimized geometries of polymer backbones. The thin film microstructures of three polymers were characterized by using GIWAXS and AFM. These three polymers were all thermally stable and showed p-type characteristic. We use bottom gate-top contact (BG-TC) structure for OFETs device. After thermal annealing, PBTBBTa-BT, PBTBBTa-TT and PBTBBTa-TVT displayed the highest hole mobility of 0.22 cm2 V-1 s-1, 0.13 cm2 V-1 s-1 and 3.1×10-2 cm2 V-1 s-1 respectively.