以噻吩為主幹之二維共軛分子與高分子之合成與性質探討

Abstract

本篇論文分為兩個主題，分別探討應用在混摻異質介面太陽能電池之二維共軛高分子以及二維共軛小分子的各種合成性質與探討。在第一部分，我們改變二維共軛高分子側鏈之鍵結位址，合成出P(v-3EHT-BT)以及P(h-3EHT-BT)兩種高分子，並探討這些噻吩(Thiophene)共軛鏈段所連接的型態對於二維共軛高分子之光電、物理特徵的影響。研究中，我們利用核磁共振光譜(NMR)與質譜(Mass)鑑定合成出來的分子結構；再利用紫外光/可見光光譜儀分析高分子側鏈不同的連結方向對於吸收光譜的影響，並利用兩者不同的共軛方式探討其結果；接著藉由電化學分析法以及低能量表面功函數量測儀(AC2)測量兩高分子的HOMO能階；使用熱重損失分析儀(TGA)、微差掃描分析儀(DSC)測量兩者的熱性質；最後利用X光繞射圖譜(XRD)探討其結晶性。我們發現側鏈與主鏈垂直之P(v-3EHT-BT)，因為其側鏈對於吸收的幫助更大而在紫外光/可見光光譜上可以測得更大的吸收係數；相對地，側鏈與主鏈平行之P(h-3EHT-BT)則因為其更高的對稱性，而使其在X光繞射圖譜上有明顯的吸收峰。 第二個主題承接第一個主題，利用第一部分所得到之結果，即主鏈平行於側鏈之P(h-3EHT-BT)具有一定的結晶性，以此結構為基礎，合成出一系列二維共軛小分子。與第一部分相同，我們也利用核磁共振光譜、質譜分析、以及元素分析鑑定所合成之分子；也利用紫外光/可見光光譜分析、電化學分析、熱重損失分析、微差掃描分析、以及低能量表面功函數量測探討其性質。在紫外光/可見光光譜的量測可以發現，此系列的小分子可以藉由共軛鏈段長短或拉電子基(electron-withdrawing group)的改變調控吸收光譜；並在X光繞射圖譜中，皆可發現一定的結晶性；最後，在低能量表面功函數量測(AC2)的分析可知，未來將可再增加推電子基或更加延長共軛，促使最高佔有電子之軌域(HOMO)提高。

This research focuses on two topics, whichincludes the synthesis and characterization of two-dimensional conjugated polymers and macromoleculesfor high-efficiency bulk-heterojunction solar cells application. At first,two-dimensional conjugated polymers, P(v-3EHT-BT) and P(h-3EHT-BT) in which a bithiophenewas employed as comonomer to reduce the crowdedness of side chains, and terthiophene units were bonded to the backbone vertically and horizontally, respectively, were designed, synthesized and characterized. The molecular structure of these polymers and the related intermediates were characterized using nuclear magnetic resonance(NMR) and mass spectrometry. Moreover, UV-visible spectroscopy was applied to examine how the side-chain architecture affects the light absorption properties of the polymers. Electrochemical analysis together with AC2 were used to determinethe band gap and energy levels, thermogravimetry analyzer (TGA) and differential scanning calorimeter (DSC) to investigate the thermal properties, and, finally, X-ray diffraction(XRD) spectrometer to study the crystallinity of the polymers. We found that the conjugation length of the side chains in P(v-3EHT-BT) is longer than that in P(h-3EHT-BT), causing the red-shift of the absorption band of side chains to visible region and the overlap with the absorption band of main chain that results in a substantial increase in the extinction coefficient of the polymer. Conversely, the thin film of P(h-3EHT-BT) possesses a strong X-ray diffraction peak, indicating the formation of orderly packed polymer chains, however, no such crystallization peak was observed for P(v-3EHT-BT). In the second topic, following the conclusion of the first part, i.e. horizontal orientation of side-chains along the polythiophene backbone can effectively promotethe formation of polymer crystallites, a series of two-dimensional conjugated macromolecules in which two linear conjugated moieties are connected by a vinyl bridge in parallel, was designed and developed. Similarly, the structure of these molecules were characterized by NMR, mass spectrometry and elemental analysis; their optical, electronic and thermal properties as well as crystallization behavior were investigated by UV-visible spectroscopy, electrochemical analysis, AC2, TGA, DSC, and XRD. Experimental results demonstrates all molecules developed herein have distinct crystallization peaks. More importantly, the absorption spectra, band-gap and energy levels of the molecules can be fine-tuned by controlling the conjugation length of two sides or by introducing proper electron-withdrawing units.