The Syntheses And Characterization Of Novel Sensitizers For Application Of Dye-sensitized Solar Cells

As the third generation solar cell, dye-sensitized solar cell(DSC) has attracted considerable interest due to the high efficiency, low cost and the simple fabrication process. As the key component of DSC, photosensitizer has an important influence on the efficiency of DSC. Therefore, it is necessary to develop the new types of photosensitizers.In order to develop novel photosensitizer with high efficiency and good stability, in this work, we synthesized an important intermediate(G-0), using thiophene as the starting material, followed by the brominated reaction, nitrification reaction, reduction reaction and condensation reaction. Then, a novel Double-Channel photosensitizer (G-1) was obtained by using efficient Suziki coupling reaction and mild hydrolysis reaction. The structure of the synthesized dye was confirmed by 1H NMR, MS, etc. This is the first time that the thiophene[3,4-b]pyrazine structure has been designed and used as the photosensitizer for DSC.The photophysical and electrochemical properties of G-1 were studied by UV-vis spectra, fluorescence emission spectrum and cyclic voltammetry(CV). UV-Vis spectra showed the broad absorptions between 350 nm to 850 nm. The solvent effect of the G-1 was investigated and the blue-shifted absorption band was observed as increasing the polarity of the solvent. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels were calculated by CV, Uv-vis spectra and fluorescence emission spectrum. The results show that:with the appropriate energy level, G-1 can be used as the photosensitizer in the DSC system. The synthesized Double-Channel photosensitizer was applied to DSCs. The influence of different dye bath and different dye concentration on the performance of DSCs was investigated. The results showed that the best photoelectric performance can be obtained when the dye concentration is 0.2 mM; the performance of DSC in the mixed solvent of THF and acetonitrile was the best. Under the optimized conditions, we studied the influence of CDCA. A slight influence on the performance of DSC was observed. Finally, the efficiency of DSC base on G-1 reached 4.66%, which shows the promising potential of this dye for DSC.To further broaden the absorption spectrum of photosensitizer, a series of Near-IR (NIR) dyes named nickel bis(dithiolene) complexes with different substituent groups were synthesized and characterized. The physical and chemical properties of the complexes were systematically studied. The UV-Vis-NIR spectra showed strong and broad absorptions in the NIR region (700 nm-1100 nm). The substituent effect and solvent effect of the obtained complexes were investigated. The electrochemical properties were investigated by CV. We also computed HOMO and LUMO energy levels of the dyes using Density Functional Theory (DFT) calculations. TG-DTG studies revealed the good thermal stability of the complexes. Furthermore, the applications of the NIR dyes DSCs were attempted and confirmed.