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

Autor: Jen-Shyang Ni, 倪偵翔
Rok vydání: 2013
Druh dokumentu: 學位論文 ; thesis
Popis: 101
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.
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