| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 100 === Though ruthenium dyes provide high power conversion efficiency in photoelectrochemical cells, pollution and costliness are fatal flaws. Therefore, researchers made efforts in biological pigments, which are easy to be collected and environmental friendly. Researchers had modified chlorophyll a structure and obtained a dye with 6.1% power conversion efficiency named chlorin. Furthermore, they added various hydrocarbon chains to chlorin. With diffierent hydrocarbon chains, the chlorin derivatives provide different efficiencies.
This research intends to find out the main factors that affect the power conversion efficiency of chlorin derivaives. By using density functional theory (DFT) with hybrid exchange-correlation functional B3LYP and 6-31G basis set, we calculated the photoelectronic properties of chlorin derivatives, such as energy gap, molecular orbital and UV/VIS absorbance spectrum. We also calculated electron injenction speed, proton affinity, and transition dipole moment. Each property is compared and discussed to analyze the major factors that affect the photoelectronic characteristics.
In addition, we use chlorin as a basic structure and alternate the central metal ion to obtain variations in photoelectrochemical properties. According to our results, the differenece in electronegativity between the central metal ion and the adjacent nitrogen atom causes changes in distribution of electron clouds, which indirectly affect the molecule absorbance magnitude in ultra violet and long wavelength range. Therefore, by alternating central metal ion with different electronegativity, the absorbance spectrum can be controlled.
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