Properties of Polypyridyl Ruthenium Complexs and Their Application on Dye-sensitized Solar Cells
Date Issued
2009
Date
2009
Author(s)
Hsu, Chiao-Ling
Abstract
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.n 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.
Subjects
absorption coefficient
dye sensitization solar cells
hybrid
short-circuit current
open-circuit voltage
Fermi level
Type
thesis
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