多吡啶釕金屬錯合物之性質及其在染料敏化太陽能電池之應用

Properties of Polypyridyl Ruthenium Complexs and Their Application on Dye-sensitized Solar Cells

徐巧玲(Chiao-Ling Hsu)

指導教授 ： 林金福

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.03288

摘要

本論文主要探討Ru-EO3(Ru(4,4’-di carboxylic acid) (5-triethylene glycol methyl ether)methyl ether-2-2’-bipyridine)-(NCS)2)在染料敏化太陽能電池 (DSSCs) 的應用，吸附行為，與其在溶液下奈米結構之研究。研究可分為三部份。第一部份利用NMR與IR鑑定有機釕金屬分子Ru-bpyEO3(Ru(5-triethy lene glycol methyl ether)methyl ether-2-2’- bi pyridine)-(NCS)2)，由UV-Vis光譜發現，溶於MeOH溶劑中其波長在501nm的吸收係數(absorption coefficient)為 9902 M-1 cm-1。此外，利用AFM觀察Ru-bpy EO3於溶液中沉降會形成平均高度為0.8nm單位體的分子聚集行為，推測是其吡啶官能基上帶有親水性EO3鏈段，可與親水性的雲母片產生作用力，形成遍佈整個雲母片基底的分子聚集結構。若在溶液中添加Titania摻和，因Ru-bpyEO3與TiO2間的作用力並不大，以致於無法清楚地發現Titania附著於Ru-bpyEO3分子時所形成有機/無機奈米複合體。
第二部份利用NMR與IR鑑定有機釕金屬染料分子Ru-EO3，由UV-Vis光譜發現其溶於Acentonitile/Tertbutanol(體積比1：1)溶劑下，在可見光區有良好且寬廣的吸收特性，且在波長539nm下的吸收係數可達 11700 M-1cm-1。而Ru-EO3在染料敏化太陽能電池 (DSSC) 的研究結果發現，隨著電解質中的Li+濃度增加，短路電流（Jsc）值上升，開環電壓（Voc）會下降，因Ru-EO3上的EO3鏈段能與Li+產生配位鍵結，緩和TiO2的費米能階(Fermi Level)值下降和Voc降低的趨勢。以元件的表現上來看，當濃度為0.05M LiI的電解質下，效率可達到6.55%。
第三部份利用NMR與IR鑑定有機釕金屬染料分子Ru-C (Ru(4,4’-dicarboxylic acid)(4,4’-bis(diundec-1-ene)-2-2’-bipyridine)-(NCS)2 )，並藉用AFM觀察染料吸附行為，發現染料分子先以類似微胞顆粒或是大顆粒聚集的型態分散吸附在TiO2上，之後染料分子會慢慢均勻吸附到TiO2未被覆蓋的表面，當達到平衡穩定之後，最後可觀察出染料完全覆蓋TiO2，形成高度約一個染料分子的均勻表面。最後利用UV-Vis光譜分析比較Ru-EO3、N3與Ru-C(Ru(4,4’-dicarboxylic acid)(4,4’-bis(diundec-1-ene) -2-2’- bipyridine)-(NCS)2 )吸附於TiO2之吸附量。結果發現，Ru-Ｃ與Ru- EO3分別在12小時及48小時達單層染料分子，為直立於TiO2表面上的奈米結構，因N3帶有四個羧基化吡啶配位鍵，容易平躺於TiO2表面上，使單一分子表面積較Ru-EO3、Ru-C大，並藉由分子間能藉由羧酸基一直吸附上去，因此N3的吸附量有持續增加的現象，在吸附24小時內可達單層吸附。

關鍵字

吸收係數 ； 染料敏化太陽能電池 ； 有機/無機奈米複合體 ； 短路電流 ； 開環電壓 ； 費米能階

並列摘要

This research mainly focused on the properties, adsorption behavior and the nanostructures of the Ru-EO3(Ru(5-triethy lene glycol methyl ether)methyl ether-2-2’- bipyridine)-(NCS)2), a new dye for the dye sensitization solar cells (DSSCs). It contains three parts. In the first part, Ru-bpyEO3(Ru(5-triethy lene glycol methyl ether)methyl ether-2-2’- bi pyridine)-(NCS)2) was characterized by NMR and IR, and its optical properties in the methanol solution were studied by UV-vis spectrascopy. From the UV-vis spectra, the absorption coefficient of Ru-bpyEO3 at the wavelength of 501nm is 9902 M-1cm-1. In addition, the nanostructure of compounds was also investigated by AFM. The Ru-bpyEO3 depositing on mica from methanol solution formed a single molecular layer of the aggregated structure with the average height of about 0.8 nm . It is believed that the hydrophilic EO3 chains could interact with mica to form a homogeneous aggregation structure. Due to the weak interaction between Ru-bpyEO3 and TiO2. there is no clear nanostrucuture observed in their hybrid.
In the second part, Ru-EO3 was characterized by NMR and IR, and its optical properties in the acentonitile/tertbutanol(vol%=1:1) solution were studied by UV-vis spectrascopy. From the UV-vis spectra, Ru-EO3 has a strong and board absorption in the visible wavelength range, and the absorption coefficient of Ru-bpyEO3 at the wavelength 539nm is 11700 M-1cm-1. Then, we investigated the application of Ru-EO3 on the DSSCs with a suitable electrolyte system for better performance. Owing to that the EO3 chains on the dye molecules could coordinate with Li+ in the electrolyte system, it reduced the positive shift of the TiO2 conduction band potential caused by Li+. With the addition of Li+ to electrolyte system, we observe a significant increase in the short-circuit current with only small decrease of the open-circuit voltage. In terms of the performances of devices, the best photo-to-electron power conversion efficiency of DSSC was 6.55% with 0.05M LiI in the electrolyte system.
In the final part, the adsorption mechanism of ruthenium dyes such as Ru-EO3, N3, Ru-C(Ru(4,4’-dicarboxylic acid)(4,4’-bis(diundec-1-ene)-2-2’-bipyridine)- (NCS)2) on TiO2 was studied by atomic force microscopy. The results revealed that the adsorption of dye molecules on TiO2 surface began in micelle form, followed by the dissolution of the condensed dyes located away from TiO2, resulting the center-hollowed ring configuration. With the increase of time, the dye molecules adsorbed onto the uncovered TiO2 surface, leading to a homogeneous surface with an approximate height of one dye molecule. Then, we measured the adsorptive amount of Ru-EO3、Ru-C and N3 on the TiO2 at different adsorbing time interval with UV-vis absorption spectrascopy. Through calculation, we suggested that Ru-C and Ru-EO after 12 and 48 h adsorption, respectively covered a monolayer with the molecules tilted vertically with respect to the TiO2 surface. Due to that N3 had four carboxylic acid groups, it easily lied in flat form on the surface of TiO2. This is the reason why the suface of N3 is larger than those of Ru-EO3 and Ru-C. The adsorptive amount of N3 on TiO2 surface reached a monolayer within 24 h. Because the N3 molecules tended to interact each other with their carboxylic acid groups, the adsorption might be more than single layer.

並列關鍵字

absorption coefficient ； dye sensitization solar cells ； hybrid ； short-circuit current ； open-circuit voltage ； Fermi level

參考文獻

7. M. Grätzel, K. Kalyanasundaram, Curr. Sci. 66, 706 (1994)

48. P. J. Li, J. H. Wu, M. L. Huang, S. C. Hao, Z. Lan, Q. H. Li, S. J. Kang, Electrochim. Acta 53, 903 (2007)

49. P. Petrov, I. Berlinova, C. B. Tsvetanov, S. Rosselli, A. Schmid, A. B. Zilaei, T. Miteva, M. Dürr, A. Yasuda, G. Nelles, Macromol. Mater. Eng. 293, 598 (2008)

55. O. Taratula, E. Galoppini, D. Wang, D. Chu, Z. Zhang, H. Chen, G. Saraf, Y. Lu, Journal of Physical Chemistry B 110, 6506 (2006)

41. G. R. R. A. K. Kumara, G.K.R. Senadeera, P.V.V. Jayaweera, D.B.R.A. De Silva, K. Tennakone, Sol. Energy Mater. Sol. Cells 69, 195 (2001)