利用電泳沉積製備染料敏化太陽能電池中的多壁奈米碳管對應電極

Multi-Wall Carbon Nanotubes Based Counter Electrodes for Dye-Sensitized Solar Cells by Electrophoretic Deposition

連志恒(Chih-Heng Lien)

指導教授 ： 萬其超

國立清華大學/工學院/化學工程學系/碩士(2011年)

https://doi.org/10.6843/NTHU.2011.00205

摘要

近年來，染料敏化太陽能電池(Dye-sensitized solar cells, DSSC)因其高效率、低成本和簡單的製程而引起廣泛的注意。其中，白金電極在DSSC的對應電極上扮演降低過電位和加速I3-還原速率的角色，然而，因為白金的使用會造成DSSC成本的上升，所以很多替代性材料已被研發來取代白金對應電極。其中，多壁奈米碳管因為具有較大的比表面積和快速的電子傳遞特性，使其有潛力的替代性材料。
現今，有許多製備多壁奈米碳管的方式，例如網印、刮刀塗佈漢化學氣相沈積。但目前的製備方式大多需要高溫製程，而高溫製程將會限制可撓式基板的應用於DSSC上，因此在本實驗中，利用奈米碳的的電泳沈積製備染料敏化太陽能電池的奈米碳管對應電極
在本篇論文中，應用奈米碳管的電泳沈積技術製備染料敏化太陽能電池中的奈米碳管對應電極。首先，利用硫酸和硝酸的混合溶劑改質奈米碳管表面，使奈米碳管表面官能基化。然後根據藉由拉曼光譜和掃描式電子顯微鏡的分析，可以推知奈米碳管在改質過程中，會使碳管表面產生缺陷和造成奈米碳管的斷裂。而這些缺陷和斷面會成為一個催化點，促進電解質中的I3-還原成I-，進而提升染料敏化太陽能電池的效率。因此在本實驗中可藉由改質技術將DSSC效率從大幅提升。此外，藉由CV的分析，可證實用電泳沈積方式製備的奈米碳管電極具有良好的穩定性。將本實驗製作的奈米碳管電極和刮刀塗佈比較，並藉由膠帶測試碳膜的附著力，可證實本實驗所製備的奈米碳管電極具有較佳的附著力，此外，利用CV分析奈米碳管的催化活性，可發現由電泳沈積所製備的電極具有較佳的催化性，這是因為刮刀塗佈中碳膜的黏著劑所造成的屏障，使其活性下降。因此，在本論文中可證實，利用電泳沈積技術製備奈米碳管電極具有相當大的潛力於低成本DSSC的應用.

關鍵字

多壁奈米碳管 ； 電泳沉積 ； 染料敏化太陽能電池 ； 對應電極

並列摘要

In recent years, dye-sensitized solar cells (DSSCs) have aroused intensive interests due to their high efficiency, low cost, and simple fabrication procedure. Pt is still the effective catalytic material for a DSSC counter electrode to reduce voltage loss and speed up the reduction of triiodide (I3-) ions. In order to reduce the cost of DSSCs, great deals of alternatives have been proposed to replace noble Pt. Multi-wall carbon nanotube (MWCNT) is one of the promising alternatives due to its high specific surface area and rapid electron transfer nature. Until now, various approaches have been made to fabricate MWCNT-base counter electrode, such as screen printing, doctor-blade and chemical vapor deposition. Most of methods must need the requirement of high temperature treatment to remove binder from the paste after the coating. The use of heat treatment limits the application in plastic substrates, and thus a low temperature method to fabricate the MWCNT-base film is needed for flexible DSSCs.

In this study, electrophoretic deposition (EPD) was employed to make MWCNT-base counter electrode for DSSC. Firstly, an acid mixture solution was used to functionalize MWCNTs. According to the Raman spectra and SEM results, the defects and open-ends were observed by chemical functionalization. In general, those defects and open-ends would become catalytic sites and benefit the enhancement in the catalytic ability of MWCNTs. Consequently, it can be observed that the catalytic ability of MWCNT-base electrode and the efficiency of DSSC assembled with MWCNT-base counter electrode were much improved by the optimization of surface functionalization on the MWCNT. In addition, the CV test demonstrated that an excellent electrochemical stability of the prepared MWCNT counter electrode can be obtained. Comparing with tape-cast, the CNT electrode fabricated by EPD had better adhesion and catalytic ability because the binder added into the paste for coating CNT film by doctor blade which may produce some shielding effect on CNT and lower its catalytic ability. Therefore, the MWCNT electrode prepared by EPD could be great potential for use in low-cost DSSCs.

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