帶單邊脂肪族鏈與可交聯型釕金屬錯合物在染料敏化太陽能電池之合成與應用

Synthesis and Applications of Tethering Single Alkyl-chain type and Crosslinkable type Ruthenium Complex Dyes on Dye-sensitized Solar Cells

倪偵翔(Jen-Shyang Ni)

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/博士(2013年)

https://doi.org/10.6342/NTU.2013.02976

摘要

染料敏化太陽能電池（DSSC）在各類有機太陽能電池中，擁有最佳的光電轉換效率，其結構包含工作電極、染料、電解質，以及對電極等四大部分，主要染料扮演著分離電子－電洞的重要角色，也是整體元件最重要的一環。因此，在本研究中，將設計出「帶單邊脂肪族鏈」的RuC9與RuEO3，與「可交聯型」RuAS等兩種類型的釕金屬錯合物染料，探討染料吸附於二氧化鈦工作電極後，對整體元件所造成的效應。

在第一部分中，合成了帶有單邊長烷碳鏈段的釕金屬錯合物染料RuC9〔Ru(4,4’-dicarboxyl-2,2’-bipyridine)(4-nonyl-2,2’-bipyridine)(NCS)2〕，除了利用NMR、IR、UV-vis與EIS-MASS等光譜鑑定出染料含有兩種結構異構物之外，還透過UV-vis光譜分析比較RuC9與Z907染料吸附於二氧化鈦之吸附量，從吸附量的表現上發現，單邊取代RuC9染料減少了染料之間長烷鏈段的團聚，得到比雙邊取代的Z907染料較高的吸附量，加上RuC9染料本身擁有較高的MLCT波段吸光係數，不僅表現在元件IPCE上，呈現較卓越的單波長光電轉換效率，而且在DSSC元件短路電流（Jsc）表現上，亦高出雙邊取代的Z907元件約6%。最後，透過EIS分析得知，由於RuC9元件呈現較高的電子與電解質進行再結合機率，致使整體元件的光電轉換效率表現稍低於Z907元件。另外，為了改善二氧化鈦與電解質之間的介面阻抗，合成了含有單邊乙烷氧（EO）鏈段的RuEO3〔Ru(4,4’-dicarboxyl-2,2’-bipyridine)(5-tri(ethylene glycol)-2,2’-bipyridine) (NCS)2〕染料，除了結構上基本的鑑定之外，在經由ATR-FTIR觀察染料上EO鏈段螯合Li＋離子的效應，藉此改善DSSC元件的開環電壓（Voc）與整體的光電轉換效率。

第二部分主要在合成帶有可螯合I3－錯離子之醯胺官能基，以及可進行交聯反應的苯乙烯官能基之釕金屬染料RuAS〔Ru(4,4’-dicarboxyl-2,2’-bipyridine) [4,4’-bis(styrenylaminocarbonyl)-2,2’-bipyridine](NCS)2〕，在NMR與ATR-FTIR之結構鑑定中發現，RuAS擁有螯合I3－錯離子之特性。因此，搭配含有不同I2濃度的液態電解質，在DSSC元件之表現上觀察到，RuAS透過醯胺官能基螯合I3－錯離子，減緩二氧化鈦的電子與電解質進行再結合的機率，進而在高濃度I2濃度環境下，元件依然保有一定的Voc。接著，利用帶有EO鏈段的trimethylol- propane ethoxylate triacrylate（TET，Mn ~912）與PO鏈段的glycerol propoxylate triacrylate（GPTA，Mw ~528）等功能性單體與RuAS染料進行共聚合改質，並於ATR-FTIR光譜中觀察到，改質後的RuAS-co-TET 與RuAS-co-GPTA工作電極表面皆能與Li＋、I3－離子進行螯合之特性。透過UV-vis吸收光譜觀察到，相對於未交聯的RuAS工作電極（39%），RuAS-co-TET 與RuAS-co-GPTA分別保有65%與75%的染料數未被0.1N NaOH溶液脫附。在元件的表現上，亦將原本RuAS自身聚合的crosslinked RuAS元件光電轉換效率從5.9%分別提升到6.9%與7.7%。最後，透過電化學阻抗頻譜（EIS）、開環電壓衰退之瞬態，以及IMVS/IMPS等技術，來分析經由改質後的工作電極對於整體元件所造成的影響。

關鍵字

染料敏化太陽能電池 ； 單邊取代 ； 釕金屬染料 ； 交聯 ； 螯合 ； 鋰離子 ； 三碘錯離子

並列摘要

Dye-sensitized solar cells (DSSC), composed of working electrode, dye, electrolyte and counter electrode, have the highest power conversion efficiency among the organic solar cells at present. Notably, the ruthenium complex dyes play the most important role for separating the electron-hole pair by exciting the dye with light. In this research, by modifying the bipyridine ligand of the ruthenium complex with single alkyl-chain or crosslinkable functional group, we investigated the relation between molecular structure and photovoltaic performance of DSSC.

In the first part of this research, Ru(4,4’-dicarboxyl-2,2’-bipyridine)(4-nonyl- 2,2’-bipyridine)(NCS)2 (denoted as RuC9) tethering single alkyl chain was synthesized and compared its adsorption behavior onto the mesoporous TiO2 film and photovoltaic properties with Z907, which has alike chemical structure but tethers two alkyl chains. The DSSC with RuC9 dye showed higher short-circuit photocurrent (Jsc) than that with Z907, attributing to its higher molar optical extinction coefficient (ε, 11,400 M-1cm-1), incident photon-to-current conversion efficiency (IPCE) and more adsorption amount onto the mesoporous TiO2 film. However, the DSSC with Z907 dye has higher open-circuit photovoltage (Voc) and power conversion efficiency (PCE), presumably because of the fact that more alkyl chains for Z907 form a molecular layer with higher hydrophobicity reduced the charge recombination at the interface between the dye-sensitized mesoporous TiO2 film and electrolyte, which has been verified by electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent and photovoltage spectroscopies (IMPS/IMVS). Additionally, Ru(4,4’-dicarboxyl-2,2’-bipyridine)(5-tri-(ethylene glycol)-2,2’-bipyridine)(NCS)2 (denoted as RuEO3) tethering single ethylene oxide (EO) chain was synthesized to improve the Voc of DSSC with its capability of coordinating Li+ ion, which was investigated by the ATR-FTIR. The DSSC with RuEO3 had higher Voc (0.7 V) than that with RuC9 (0.67 V), but lower Jsc (13.7 mAcm-2) and PCE (6.55%) due to its lower adsorption amount onto the mesoporous TiO2 film.

In the second part, the crosslinkable ruthenium complex dye, Ru(4,4’-dicarboxyl- 2,2’-bipyridine)[4,4’-bis(styrylaminocarbonyl)-2,2’-bipyridine](NCS)2, denoted as RuAS, was synthesized and well characterized with 1H-NMR, 13C-NMR, HSQC, UV-vis, EA and ESI-MS spectra. Its capability of chelating triiodide anion with 4,4’-bis(styrylaminocarbonyl)-2,2’-bipyridine ligand (bsacbpy) was revealed by ATR-FTIR spectroscopy, which reduced the charge recombination by retarding the triiodide ions from closing to the mesoporous TiO2 film in DSSC. Therefore, the Voc of DSSC barely changed with the triiodide concentration in the electrolyte. Moreover, after polymerizing with trimethylolpropane ethoxylate triacrylate (TET) or glycerol propoxylate triacrylate (GPTA), the crosslinkable extent and ion-coordinating properties of RuAS were measured by ATR-FTIR and UV-vis spectroscopy after rinsed with 0.1 N NaOH solution. The PCE of DSSC with RuAS-co-TET and RuAS-co-GPTA was enhanced up to 6.9% and 7.7%, respectively than that with crosslinked RuAS (5.9%), attributed to the capability of coordinating Li+ ions by TET and GPTA. The enhanced photovoltaic performance was further examined by IPCE, EIS and open-circuit potential decay transient measurements.

並列關鍵字

dye-sensitized soalr cells ； crosslinkable ； ruthenium ； lithium ion ； triiodide ； coordinating ； chelating

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