Betalain-based dyes as photosensitizers for energy harvesting application: a theoretical investigation
| dc.contributor.author | Tsere,Melkizedeck | |
| dc.date.accessioned | 2025-09-16T12:18:19Z | |
| dc.date.issued | 2025-07 | |
| dc.description | SDG-7:Affordable and Clean Energy SDG-9:Industry, Innovation and Infrastructure SDG-12:Responsible Consumption and Production SDG-13:Climate Action | |
| dc.description.abstract | Betalain dyes are natural pigments that have attracted growing research interest as promising materials for light-harvesting applications. In the present work, the modification of betalain dyes was performed through a computational approach, aimed at screening the wide spread of blended triphenylamine-betalain dyes for dye sensitized solar cell applications. In the first modification approach, betalamic acid was joined to the phenyl ring and further grafted with electron donor groups to enhance light absorption and charge transfer ability. The second approach involved the introduction of new anchoring groups featuring carboxylic acid CH=C(X)COOH for the A1-X dyes and nitro group -CH=C(X)NO2 for the A2-X dyes, where X = CN, CH3, CCl3, CF3. In addition to molecular grafting, the solvent effects on the optoelectronic parameters and dye adsorption to the semiconductor surface were evaluated. The geometrical structures, optoelectronic properties of designed dyes and binding to the semiconductor have been explored. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods coupled with B3LYP and CAM-B3LYP at 631+G(d,p) basis set were used for ground and excited state calculations, respectively. In the UV-Vis spectra, the maximum absorption wavelengths range between 400 ‒ 442 nm based on grafting with an electron donor. However, further modifications by introducing new anchoring units resulted in huge redshifts in wavelengths: 400 ‒ 700 nm for CH=C(X)COOH and between 500 and 1000 nm for the -CH=C(X)NO2. The attachment of the dyes to the semiconductor was modelled via binding to (TiO2)6H3 cluster; A2-X dyes exhibited more stable Dye@TiO2 complexes with binding energies (BEs) ranging between ‒4.08 and ‒2.88 eV compared to A1X dyes with BEs from ‒1.11 to ‒0.05 eV in water solution. The results evince that the blended triphenyl-betalain dyes with the CH=C(X)NO2 anchoring groups could be promising materials for light harvesting applications. Among the CH=C(X)NO2 dyes, the CH=C(CN)NO2 demonstrated superior optoelectronic properties and binding stability, thus, would be expected the most favourable candidate for light-harvesting applications in dye sensitized solar cells. | |
| dc.identifier.uri | https://dspace.nm-aist.ac.tz/handle/123456789/3248 | |
| dc.language.iso | en | |
| dc.publisher | NM-AIST | |
| dc.title | Betalain-based dyes as photosensitizers for energy harvesting application: a theoretical investigation | |
| dc.type | Thesis |