含三噻吩側鏈基團之 [Benzodithiophene - Terthiophene] 共聚物的合成與性質探討

本文實驗設計主要是將benzodithiophene (BDT)與含三噻吩基團作為共軛側鏈之單體，以Stille polycondensation進行共聚，合成一系列新穎二維共軛高分子，P3EHTBDT、 P3TBDT、P3TBDTDT及P3TBDTCN，並針對其光學性質及電化學性質作分析與討論。此一系列共軛高分子的側鏈皆具有以雙鍵(vinyl group)作為共軛橋樑並以三噻吩為主要共軛側鏈基團，在共軛側鏈上接乙基己基（2ethylhexyl）烷鏈來增加高分子的溶解度。P3TBDT於主鏈中較P3EHTBDT多引入了兩個噻吩，而P3TBDTDT及P3TBDTCN則是於共軛側鏈上以縮合反應的方式分別修飾上兩種不同的拉電子基團，分別研究引入噻吩以及於側鏈接上拉電子基團後對於結晶行為、光學及電化學性質之影響。本研究合成出之中間物、單體以及最終的共軛高分子均應用核磁共振光譜儀 (1H NMR、13C NMR、COSY、HSQC以及HMBC) 及質譜儀 (mass spectrometry) 對其分子結構進行鑑定，而共軛高分子 P3TBDTDT 及 P3TBDTCN 則進一步使用紅外線光譜儀 (FT-IR spectrometer) 以及元素分析儀 (elemental analyzer) 來鑑定其末端修飾是否完全。共軛高分子的性質研究分別是由凝膠滲透層析 (Gel permeation chromatography, GPC) 進行分子量特性分析、 X 光單晶繞射儀 (XRD) 做結晶測試、紫外光-可見光光譜儀 (UV/Vis spectroeter) 測量其吸收範圍以及吸收係數等光學性質、循環伏安法 (cyclic voltammtry) 作電化學性質分析以及光電子光譜儀 (photoelectron spectrometer, AC-2) 做表面功函數分析量測 HOMO 能階。實驗結果顯示，將噻吩引入兩單體之間作為隔離物 (spacer group) ，可有效的減少空間位阻增加高分子主鏈的共平面性，使其紫外光-可見光吸收光譜更加寬廣並且增強吸光能力。另一方面，在二維共軛高分子 P3TBDTCHO 側鏈的末端利用縮合反應修飾上兩種拉電子基團，由其光學性質可證實透過結構修飾可使共軛側鏈的吸收光譜紅位移進而增加特定範圍的吸光能力，其中 P3TBDTCN 於單一波長 (500nm) 展現出優異的吸收係數，而由電化學性質中可以發現透過結構的修飾不僅可有效降低能隙並能有效控制其 HOMO 能階。

關鍵字

二維共軛高分子；拉電子基團；高分子太陽能電池

並列摘要

In this study, a series of new two-dimensional conjugated polymers with benzodithiophene (BDT) unit, including PTBDT、P3TBDT、P3TBDTDT and P3TBDTCN were designed and synthesized using Stille coupling polymerization methed. These polymers bear terthiophene groups as conjugated side-chains and vinyl groups as conjugated bridge to link the side-chains to polymer backbone. To enhance the solubility, each terminal thiophenes of the terthiophene unit was incorporated with one ethylhexyl group. To reduce the crowd of effect in PTBDT, two thiophene rings were inserted into the backbone as space to form P3TBDT；moreover, the two ends of terthiophene side group in P3TBDT were further chemically modified with two different acceptor units, 1,3-diethyl-2-thiobarbituric and ethyl-2-cyanoacetate, to yield P3TBDTDT and P3TBDTCN, respectively. All intermediates and monomers were characterized using 1H NMR, 13C NMR, COSY, HSQC, HMBC and HRESI mass spectrometry. The properties of as-synthesized copolymers were characterized by UV-vis absorption spectrometer, X-ray Diffractometer, photoelectron spectrometer AC-2 and cyclic voltammetry. Gel permeation chromatography (GPC) was employed to determine the molecular weight characteristics of the final polymers. Experimental results show that inserting two thiophenes as spacer into the main chain of P3TBDT improves the coplanarity and increases the effective conjugation length of the polymer backbone. Compared with PTBDT, P3TBDT exhibits a narrower bandgap, a broader absorption spectrum and an enhanced absorption coefficient. Moreover, the incorporation of electron-withdrawing units to the terthiophene side groups in P3TBDTDT and P3TBDTCN greatly red-shifts the absorption of terthiophene into visible range and overlap with the absorption of main-chain that substantially increases the light-harvesting capability of polymer in a specific wavelength region.

並列關鍵字

electron-withdrawing ； two-dimensional polymer ； polymer solar cell

參考文獻

1. Tang, C. W.; VanSlyke, S. A., "Organic electroluminescent diodes," Appl. Phys. Lett., vol. 51, no. 12, 1987, pp. 913-915.

2. Coakley, K. M.; McGehee, M. D., "Conjugated Polymer Photovoltaic Cells," Chem. Mater., vol. 16, no. 23, 2004, pp. 4533-4542.

3. Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J., "Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-Acceptor Heterojunctions," Science, vol. 270, no. 5243, 1995, pp. 1789-1791.

4. Sun, S.-S., "Design of a block copolymer solar cell," Sol. Energy Mater. Sol. Cells, vol. 79, no. 2, 2003, pp. 257-264.

5. Ma, W.; Yang, C.; Gong, X.; Lee, K.; Heeger, A. J., "Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology," Adv. Funct. Mater., vol. 15, no. 10, 2005, pp. 1617-1622.

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含三噻吩側鏈基團之 [Benzodithiophene - Terthiophene] 共聚物的合成與性質探討

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