Search

DFT and TD-DFT calculations using ten various functionals contain 0 to 100% of HF exchange amount (BLYP, B3LYP, PBE0, M06, BHandH, BHandHLYP, M06-2X, CAM-B3LYP, LC-ωPBE and M06HF), in combination with ten double-ζ and triple-ζ basis sets of Poples, have been performed in order to explore their effects on the geometrical and electronic properties, and evaluate their accuracies to predict the visible spectra of C213, C214 and C215 triphenylamine-based (TPA) dyes for Dye-sensitized solar cells (DSSCs) applications. The calculation of the bond lengths and dihedral angle values for C213 dye ground state geometry showed a sensitive dependence to the percentage of HF exchange amount contribution in xc-functional, while the contributions of augmentation of the basis sets size has no remarkable effect from the 6-31G(d) basis set. Regarding the energies of the HOMO and LUMO levels, their calculation values were dependent on functional nature. The great accuracy to predict the ground state maximum absorption wavelength was showed by the functional approaches having HF exchange amount around 50%. The best prediction was recorded by BHandH functional using 6-31+G(d) basis set for both geometry optimization and TDDFT calculations within CPCM/THF solvent model. Using the lowest computational cost and accurate method, the light harvesting efficiency (LHE) was enhanced from C213 to C215 dye. Additionally, the injection driving force (Δ G inject . ) to TiO 2 semiconductor and the driving force for regeneration (Δ G reg ) by I − /I 3 − electrolyte were evaluated and suggest that the intermolecular charge-transfer mechanism is operative in the studied dyes when applied to DSSC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Newly designed triazatruxene dye-sensitized solar cells are presented. • Different benzodiazine π-linkers as auxiliary acceptors were efficiently studied. • The studied dyes revealed significant light capture in the visible region. • The overall data suggest that these dyes are suitable photosensitizers for DSSCs. In this work, six new organic (D–π–A) dyes based on triazatruxene have been designed by modifying the π- linkers groups and the anchor unit of the reference dye R. Their structural, electronic, frontier molecular orbital, chemical reactivity, and photovoltaic have been studied using DFT (density functional theory) at B3LYP/6-31G (d,p). Furthermore, the TD-DFT (time-dependent DFT) at TD-BHandH/6-31G (d,p) level method was chosen to calculate the optical characteristics of the investigated dyes in the solvent CH 2 Cl 2. Molecular properties such as geometric parameters, optoelectronic properties, frontier molecular orbitals, natural bonding orbitals, the partial density of states analysis, electrostatic surface potential, absorption spectra, and electron accepting and donating parameters were assessed to predict proper candidates for the DSSC device. The studied dyes not only show significant λ m a x in the range of 500–650 nm, with a band gap in the range of 1.64–1.98 eV, lower λ t o t , but also high light capture efficiency and significant intramolecular charge transfer properties compared to the reference dye (R). Notably, dyes with C(CH 3) 2 and Si(CH 3) 2 exhibit the best performance among the designed dyes. [ABSTRACT FROM AUTHOR]

Highlights: [•] The structural and electronic properties of thienopyrazine–thiophene copolymer are studied by DFT. [•] The geometrical parameters ground and doped states showed that the structures of these oligomers are planar. [•] The electronic properties were determined from the fully optimized structures. [•] The investigated compounds show absorption and emission in the visible. [Copyright &y& Elsevier]

[Display omitted] • The detailed DFT and TD-DFT calculations have been performed on novel D-π-A'-π-A phosphonic acid based dyes. • The studied dyes differ in the auxiliary acceptor moiety. • The electronic, optical and photovoltaic properties were studied. • BIA, BSD, BSED, and BTED dyes showed better optical and photovoltaic properties than the other dyes. Dye-Sensitized Solar Cells (DSSCs) that are based on a donor-bridge-acceptor-bridge-donor (D-π-A'-π-A) oligothiophene dye-containing benzothiadiazole mono-functionalized by a phosphonic acid were theoretically studied during the changing of the auxiliary acceptor (A') by six other auxiliary acceptors. To further understand the molecular structure of these series of dyes, a density functional theory (DFT) calculation was performed to study the molecular geometries, frontier molecular orbitals (FMO) by employing the method B3PW91 with the basis set 6-311G(d) for the soft atoms (H, C, N, O, P, Si, S) and LANL2DZ for the heavy atoms (Se, Te). The optical properties of the free and the adsorbed dyes were modelled using TD-DFT simulations employing the functional BHandH. The calculated absorption spectra of the designed dyes indicate that the change of electron-withdrawing groups increases the absorption wavelength significantly. Our results showed that the BTD, BXD, BTED, BSED, BIA, and BSD dyes exhibit a narrower HOMO–LUMO energy gap than BTZ dye. This led to a broader optical absorption and lower oscillator strength in dyes containing Benzimidazole, Benzosiladiazole, Benzoselenodiazole, and Benzotellurodiazole moieties that were verified to be better auxiliary acceptor units. The simulated absorption spectra of the adsorbed dyes on (TiO 2) 9 are red-shifted compared to the free dye. The adsorption energies of all dyes are similar which reveals that the adsorption energy is not depending on the auxiliary moiety but rather on the anchor group. Therefore, it is expected that the results obtained from this investigation will have a substantial impact on the development of DSSC of phosphonic acid-based dyes. [ABSTRACT FROM AUTHOR]

In this work, theoretical study by using the DFT method on eleven conjugated compounds based on thienopyrazine is reported. Different electron side groups were introduced to investigate their effects on the electronic structure; The HOMO, LUMO and Gap energy of these compounds have been calculated and reported in this paper. A systematic theoretical study of such compound has not been reported as we know. Thus, our aim is first, to explore their electronic and spectroscopic properties on the basis of the DFT quantum chemical calculations. Second, we are interested to elucidate the parameters that influence the photovoltaic efficiency toward better understanding of the structure–property relationships. The study of structural, electronic and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials. [ABSTRACT FROM AUTHOR]