Browsing by Author "Wazzan, Nuha"

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Effect of Electron Donor Groups on Optoelectronic Properties of Betalain Dyes: A DFT Study
(wiley, 2025-05) Tsere, Melkizedeck; Costa, Rene; Deogratias, Geradius; Pogrebnaya, Tatiana; Pogrebnoi, Alexander; Machunda, Revocatus; Al-Qurashi, Ohoud; Wazzan, Nuha; Babu, Nambury
A sensitizer is a vital component of dye-sensitized solar cells(DSSCs); it absorbs incident photons, excites electrons, and facil-itates charge transfer to the semiconductor. In the present work,modification of betalain dyes through grafting of electron donorgroups has been performed. The reported optoelectronic properties of the investigated dyes are determined using densityfunctional theory (DFT) and time-dependent DFT methods. The investigated sensitizers exhibit maximum absorption between400 and 442 nm with light-harvesting efficiencies exceeding 93%.Favorable interactions are observed between the dyes and the hydrogenated TiO2 cluster, (TiO2)6H3. The obtained binding energies range from 1.39 to 0.97 eV in the gas phase and 0.31 to 0.03 eV in water. The electronic spectra of the dye@TiO2 complexes show broader and intensive bands with bathochromicshifts when compared to the individual dyes. The charge density distribution in the complexes indicates appropriate ability of thedyes for charge injection to the semiconductor. Among the considered dyes, the most promising candidates for use in DSSCs have been selected.
Enhancing the optoelectronic properties of blended triphenylamine-betalain based dyes through tailoring the anchoring unit: a theoretical investigation
(Taylor & Francis, 2024-11-25) Tsere, Melkizedeck; Costa, Rene; Deogratias, Geradius; Al-Qurashi, Ohoud; Wazzan, Nuha; Pogrebnaya, Tatiana; Pogrebnoi, Alexander; Machunda, Revocatus
A series triphenyl-betalain organic dyes featuring carboxylic acid and nitro anchoring groups CH = C(X)COOH for the A1-X dyes and -CH = C(X)NO2 for the A2-X dyes, respectively, where X = CN, CH3, CCl3 and CF3 was evaluated for dye sensitised solar cells application. The geometrical structures, molecular orbitals and energies, light absorption patterns, free energies of electron injection and dye regeneration and binding to the semiconductor have been explored using DFT/TD-DFT methods. The nitro-based anchoring group resulted in pronounced red-shift in absorption spectra between 111 and 317 nm compared to carboxylic acid-based dyes. 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 A1-X dyes with BEs range of −1.11 to −0.05 eV. The results evince that the dyes with CH = C(X)NO2 anchoring groups could be promising materials for light harvesting application.
Investigation of optoelectronic properties of triphenylamine-based dyes featuring heterocyclic anchoring groups for DSSCs’ applications: a theoretical study
(Springer Nature Switzerland AG., 2020-08-05) Deogratias, Geradius; Al-Qurashi, Ohoud S.; Wazzan, Nuha; Seriani, Nicola; Pogrebnaya, Tatiana P.; Pogrebnoi, Alexander M.
Design and synthesis of new potent sensitizers are of interest for realization of high-efficiency Dye Sensitized Solar Cells (DSSCs). Modification of the triphenylamine-based dyes by introducing suitable anchoring groups aimed at improvement of optoelectronic properties is attempted in our work. The molecular structure, molecular orbitals and energies, electronic absorption spectra, free energies of electron injection and dye regeneration, chemical reactivity parameters and adsorption to TiO2 semiconductor have been reported. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were used to obtain the reported properties. The results reveal superior optical, electronic properties, chemical reactivity parameters and adsorption energies for the investigated dyes. The findings evince that the dyes featuring heterocyclic anchoring groups could be potential candidates for DSSCs’ applications; the new materials are worthy of being investigated experimentally.