Browsing by Author "Khalfan, Mwanahadia Salum"
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Item DFT and TD-DFT studies for optoelectronic properties of coumarin based donor-π-acceptor (D-π-A) dyes: applications in dye-sensitized solar cells (DSSCS)(Elsevier, 2021) Khalfan, Mwanahadia Salum; Babu, Numbury Surendra; Vuai, Saidi A, H.A series of six coumarin based dye derivatives were investigated and their geometry and optoelectronic properties elucidated for suitability in dye-sensitized solar cells (DSSCs) using TD-DFT/B3LYP with 6-31G basis set. D-π-A schemes were developed by attaching various donors and acceptors to coumarin dye (CM) to calculate changes in their photovoltaic properties. D2-CM-A2 and D4-CM-A4 showed less dihedral angle because of the low steric effect between donor and connector. The D1-CM-A1 and D2-CM-A2 results of intramolecular charge transfer were higher because of low bond length and a strong group of electron donors. The results revealed that LUMO energies of D1-CM-A1, D2-CM-A2, D3-CM-A3 and D4-CM-A4 were higher than the conduction band edge of TiO2 electrode (-4.0 eV) suggesting that these dyes will inject the electrons into the conduction band of the semiconductor. In addition, the light harvest efficiency (LHE), open-circuit voltage (VOC) and band energy gap (Eg) values are calculated in the gas phase, as well as in the solvent phase. This study shows that D1-CM-D1 and D2-CM-A2 derivatives have better properties for application in the DSSCs.Item Optoelectronic properties of Coumarin based donor-π-acceptor (D-π-A) dyes for applications in dye sensitized solar cells (DSSCS)(The University of Dodoma, 2019) Khalfan, Mwanahadia SalumDye sensitized solar cells (DSSCs) are the one among the important device which established a consideration attention for transferring a fresh solar energy to electricity in the most recent decade. Coumarin dye is one among metal free organic dyes which hold a higher potential for operating in DSSC because of its environmentally friendly, inexpensive and easy to fabricate. The aim of this study was to apply computational quantum calculations which persuade to appreciate the molecular structure, optical absorption spectra, electronic and photo physical properties of coumarin dye derivatives calculation by using DFT and TD-DFT computational method. The organic dye D-π-A dye based on coumarin and their derivatives were investigated by attaching various donors and acceptors to coumarin dyes (D-CM-A). The geometry optimization was done in gas and solvent phases. Electron absorption spectra in excited state energies and oscillator strength (f) were calculated through TD-DFT/B3LYP method with 6-3IG basis set calculations of fully DFT optimized geometries. The results show that, D4-CM-A4 in third and fourth positions have the smallest energy gap (‒1.98 and ‒1.49 eV respectively). On the contrary, the light harvesting efficiencies (LHE) were calculated and this parameter depends upon the oscillator strength of the dye molecules. The results depicted that, in both positions D1-CM-A1 and D2-CM-A2 have the highest LHE (0.85 and 0.91 respectively) than other dye derivatives. Therefore, it is suggested that, D1CM-A1 and D2-CM-A2 have better properties for application in DSSC as compared with rest dye derivatives.Item Theoretical studies of electronic and optical characteristics in donor-π-Acceptor (D-π-A) dyes: DFT and TD-DFT methods(Oxford University Press (OUP), 2023) Numbury, Surendra Babu; Khalfan, Mwanahadia Salum; Vuai, Said A HThis research focused on enhancing D-π-A organic dyes derived from coumarin and its derivatives, collectively referred to as D-CM-A dyes. The study aimed to improve these dyes by introducing various donors and acceptors to the coumarin structure. Six new coumarin dyes were evaluated, primarily for their potential application in dye-sensitized solar cells (DSSCs) to enhance energy efficiency. The analysis involved calculating the geometry, electronic properties, and optoelectronic characteristics of the dye molecules using DFT and TD-DFT methods with the B3LYP functional and the 6-311G basis set in both gas and solvent phases. The primary focus was to understand how modifications to the π-conjugated D-π-A organic dyes influenced their optoelectronic properties, including key factors such as maximum absorption wavelength (λmax), highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), and energy gap (Egap). Additionally, the study explored the photovoltaic properties of these dyes. The findings highlighted D4-CM-A4 as a promising candidate with the narrowest energy gap, while D1-CM-A1 and D2-CM-A2 showed superior light-harvesting efficiencies (LHE) compared to other derivatives. In conclusion, this study suggests that D1-CM-A1 and D2-CM-A2 are favourable choices for enhancing the performance of DSSCs due to their promising optoelectronic properties.Item Theoretical studies of electronic and optical characteristics in donor-π-Acceptor (D-π-A) dyes: DFT and TD-DFT methods(Oxford University Press (OUP), 2023-12-25) Numbury, Surendra Babu; Khalfan, Mwanahadia Salum; Vuai, Said A. H.This research focused on enhancing D-p-A organic dyes derived from coumarin and its derivatives, collectively referred to as D-CM-A dyes. The study aimed to improve these dyes by introducing various donors and acceptors to the coumarin structure. Six new coumarin dyes were evaluated, primarily for their potential application in dye-sensitized solar cells (DSSCs) to enhance energy efficiency. The analysis involved calculating the geometry, electronic properties, and optoelectronic characteristics of the dye molecules using DFT and TD-DFT methods with the B3LYP functional and the 6-311G basis set in both gas and solvent phases. The primary focus was to understand how modifications to the p-conjugated D-p-A organic dyes influenced their optoelectronic properties, including key factors such as maximum absorption wavelength (kmax), highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), and energy gap (Egap). Additionally, the study explored the photovoltaic properties of these dyes. The findings highlighted D4-CMA4 as a promising candidate with the narrowest energy gap, while D1-CM-A1 and D2-CM-A2 showed superior light-harvesting efficiencies (LHE) compared to other derivatives. In conclusion, this study suggests that D1-CM-A1 and D2-CM-A2 are favourable choices for enhancing the performance of DSSCs due to their promising optoelectronic properties.