Browsing by Author "Babu, Numbury Surendra"

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    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.
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    Optical and photovoltaic properties of substituted alizarin dyes for dye-sensitized solar cells application
    (Taylor & Francis, 2020) Abubakari, Ismail; Babu, Numbury Surendra; Vuai, Said; Makangara, John
    This paper presents the theoretical study on photovoltaic and absorption properties of alizarin derivatives. Optimization of structures and calculations were performed by density functional theory and time-dependent density functional theory using B3LYP hybrid functional and 6–31 G (d,p) basis set. The dyes were formed by substituting 2-hexylthiophene mixed with carboxylic acid and 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid. The performed substitution shows improvement in most of the properties. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of molecular dyes showed positive effect upon electron injection to semiconductor and subsequent regeneration by the electrolyte. Almost all necessary and important parameters to demonstrate the usefulness of molecular dyes as photo-sensitizers are detailed discussed. Based on the discussion and analysis, all considered molecules are proved to be useful in dye-sensitized solar cells using TiO2 semiconductor and I−/I−3 couple electrolyte. Collectively, dyes DY3 and DY2 showed better results than others with LHE and V oc of 0.2142 and 0.6722 eV, respectively, for DY3 and 0.7033 and 0.6224 eV, respectively, for DY2.
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    Synthesis and photocurrent density–photovoltage (J–V) characterization of a novel alizarin derivative dye for dye-sensitized solar cell technology
    (Springer, 2022) Abubakari, Ismail; Babu, Numbury Surendra; Vuai, Said; Makangara, John
    Dye-sensitized solar cells technology has attracted extensive academic scholars’ interests due to their potential low-cost solar energy harvesting. Increasing performance of dye-sensitized solar cell needs more efficient dye to maximize solar energy absorption. This work presents the synthesis and J–V characterization studies for a novel alizarin derivative dye HDD. The dye was formed by the reaction between brominated alizarin and 5-hexyl-2-thiopheneboronic acid pinacol ester. The final dye product was successfully synthesized as brownish-orange solid. Characterization of the synthesized dye was done using spectroscopic techniques; mass spectrometry, infrared spectroscopy and nuclear magnetic resonance before photovoltaic performance investigation. The dye was found to be useful as photo-sensitizer in dye-sensitized solar cell through calculation of conversion efficiency. Generally, the dye HDD showed better results in terms of photovoltaic properties with open-circuit voltage, short-circuit current density and fill factor of 0.65 V, 0.0146 A/cm2 and 0.612, respectively. The conversion efficiency of the cell using the synthesized dye HDD was found to be 5.81% under 100 mW/cm2 solar illuminations.
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    Theoretical and conceptual framework to design D-π-A type organic dyes for application dye-sensitized solar cells
    (Elsevier BV, 2024) Makangara, John J.; Sahini, Mtabazi G.; Babu, Numbury Surendra
    The optimized structures and absorption spectra of five D-A-type organic dyes (M1, M2, M3, M4, and M5) were investigated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). These dyes contain the same electron acceptors and -spacers but distinct 3,6- and 2,7-carbazole electron-donating groups. The results showed coplanar geometries for the dyes, which implied strong conjugation. When intramolecular charge transfer was investigated, it was discovered that 3,6-carbazole had a better capacity to give electrons than 2,7-carbazole. These dyes' projected orbital energy levels indicate that excited dyes might successfully decrease by electrolyte while oxidized dyes could successfully inject electrons into semiconductor conduction bands. The study investigated the suitability of different dyes for use in dye-sensitized solar cells (DSSCs) and found that the M2 dye, which contains a thio group as the terminal electron donor, exhibited the most promising optoelectronic properties. In particular, M2 had a narrow energy gap, superior optical qualities, optimal FMO energy levels, the lowest total value, and greater GInject and GReg values compared to the other dyes tested. These factors contributed to M2's superior photosensitizing performance, suggesting that using M2 in DSSCs may lead to higher optoelectronic characteristics and total energy conversion efficiency compared to using other dyes.
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    Theoretical design of low bandgap donor–acceptor (D-A) monomers for polymer solar cells: DFT and TD-DFT study
    (Taylor & Francis, 2021) Vuai, Said A.H.; Babu, Numbury Surendra
    Endeavors have been made to construct new donor–acceptor (D-A) monomers utilizing 9 H-carbazole (CB) as electron donors and different electron acceptors. All estimations were finished using DFT and TD-DFT, and B3LYP level with a 6–311 G basis set in the gas and chloroform solvent. The impacts of the distinctive acceptors on the geometry of molecules and optoelectronic properties of these D-A monomers were discussed to dissect the connection connecting the molecular structures and the optoelectronic properties. Likewise, the HOMO – LUMO energies, atomic orbital densities are calculated theoretically. Notwithstanding the charge transfer measure between the carbazole electron donor unit and the electron acceptor one is upheld by breaking down the optical spectra of the acquired monomers and the restriction of involved HOMO and LUMO. The outcomes show that the D-A monomers, CB-ODP, CB-TDP, and CB-SDP, are acceptable for optoelectronic applications in organic solar cells like BHJ.
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    Theoretical studies of electronic and optical properties for some new azo disperse dyes for dye-sensitized solar cells by using TD and TD DFT method
    (East African Nature and Science Organization, 2018) Onoka, Isaac; Babu, Numbury Surendra; Makangara, John J.
    The ground states geometries, absorption wavelengths, oscillation strengths of new azo disperse dyes such as 3-aminopyrazoleazo -4- thiol-2,3,5-thiadiazole (D1),3-amino-4-methylpyrazoleazo-4-thiol-2,3, 5-thiadiazol (D2),2, 4-dihydroxybenzeneazo-4-thiol 1-2, 3,5- thiadiazole (D3),4-amino-3-benzonitrileazo-4-thiol-2,3,5-thiadiazole (D4), 2-hydroxylnaphtholazo-4-thiol-2,3,5-thiadiazole (D5) and 2-amino-5-ethylcarbazoleazo-4-thiol-2,3,5-Thiadiazole (D6) have been optimized by using density functional theory (DFT) at B3LYP level of theory with 6-31G(d) basis set. The excitation energies have been computed by using time dependent density functional theory (TDDFT). The study of structural, electronic and optical properties for these dyes could help to design more efficient functional photovoltaic organic materials. The electron injection (ΔGinject), electron coupling constants (|VRP|) and light harvesting efficiencies (LHE) of studied dyes and have been discussed with esteem to DSSCs. This theoretical designing will the pave way for experimentalists to synthesize the efficient sensitizers for solar cells
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    Theoretical studies of optoelectronic and photovoltaic properties of D–A polymer monomers by Density Functional Theory (DFT)
    (Taylor & Francis, 2021) Babu, Numbury Surendra; Vuai, Said A. H.
    In this research article, the new donor–acceptor (D–A) monomers developed using 4-methoxy- 9-methyl-9 H-carbazole (MMCB) as electron donors and various electron acceptors. DFT and TDDFT methods at the level of B3LYP with a 6–311 G basis set in a gas and chloroform solvent were used to calculate electronic and optoelectronic properties. To dissect the relationship between the molecular and optoelectronic structures, the impacts of specific acceptors on the geometry of molecules and optoelectronic properties of these D–A monomers were discussed. The calculations are also carried out on HOMO–LUMO, atomic orbital densities. The calculated band gap Eg of the monomers considered increases 3,6-MMCB-OCP ≈ 3,6-MMCB-BCO < 3,6-MMCB-SDP < 3,6-MMCBSCP < 3,6-MMCB-TCP < 3,6-MMCB-TDP < 3,6-MMCB-BCS < 3,6-MMCB-BCT in both in the gas and solvent phases. Subsequently, the optoelectrical properties of EHOMO, ELUMO, Eopt, and EB energies were critically updated. Compared to different monomers, the far lower Eg of the 3,6-MMCB-OCP and 3,6-CB-BCO has shown optoelectronic applications in organic solar cells like BHJ.