Synthesis And Characterization Of Azo Dyes As Sensitizers For Possible Application In Dye-Sensitized Solar Cells (DSSCS)
Date
2021-09
Authors
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Publisher
University Of Ghana
Abstract
Eight azo dyes were synthesized, purified and characterized. The Stuart Melting Point Apparatus was used to measure the melting point of the dyes, UV-Vis spectroscopy was used to measure the absorbance in the UV-Vis region, FT-IR Spectroscopy was used to determine the chemical bonds and composition of the azo dyes. The 1H NMR and 13C NMR were used to successfully elucidate the chemical structures of the synthesized azo dyes (DYE 1, DYE 2, DYE 3, DYE 4, DYE 5, DYE 6, DYE 7 and DYE 8). The Cyclic voltammetry was used to characterize the electrochemical behaviour of the azo dyes as sensitizers for application in Dye Sensitized Solar Cells (DSSCs). The results of the instrumentational analysis of each synthesized azo dye were compared to that of the industrial standard, inorganic ruthenizer 535-bisTBA (N719) dye. The photochemical optical band gap (Eg) calculated for the azo dyes ranged from 1.969 eV to 2.886 eV. The dye sensitizers showed an extrapolated electrochemical oxidation potential were between 0.28 eV to 0.66 eV with DYE 1 and DYE 8 offering the most efficient potential difference to remove an electron from their molecular orbitals. The optical band gaps of the dyes were between 1.969 eV and 2.886 eV as compared to literature value of 1.91 eV of the standard N719 dye. The low Eg of DYE 1, DYE 2, DYE 6 and DYE 7 suggest that the distances between their HOMO and LUMO levels is such that the energy in the visible region is enough to cause electron promotion from their valence band into their conduction bands. The calculated LUMO values obtained were -3.149 eV, -3.204 eV, -3.43 eV for DYE 6, DYE 7 and the standard N719 dye respectively. The DYE 3 has the highest LUMO energy level of -2.313 eV. The difference in the LUMO and the HOMO indicates that the electrochemical band gap of the standard N719 dye is 1.909 eV, which is the least followed by 1.97eV band gap energy for DYE 1. The electrochemical band gap of DYE 7 and DYE 6 were 2.81 eV and 2.28 eV respectively which were the second and third least energy values. These values were closer to that of the standard N719 dye. Out of the eight azo dyes studied, the DYE 1, DYE 6 and DYE 7 showed the best DSSCs sensitizer abilities although they were still less than that of the industrial dye.
Description
MPhil. Chemistry
Keywords
Dye-Sensitized Solar Cells, Synthesis