A group of dyes derived from coumarin was studied, which consisted of nine molecules using a very similar manufacturing process of dye sensitized solar cells (DSSCs). Optimized geometries, energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and ultraviolet-visible spectra were obtained using theoretical calculations, and they were also compared with experimental conversion efficiencies of the DSSC. The representation of an excited state in terms of natural transition orbitals (NTOs) was studied. Chemical reactivity parameters were calculated and correlated with the experimental data linked to the efficiency of the DSSC. A new proposal was obtained to design new molecular systems and to predict their potential use as a dye in DSSCs.

Eight novel metal-free organic sensitizers were proposed for dye-sensitized solar cells (DSSCs), theoretically calculated and studied via density functional theory with D-π-A structure. These proposals were formed to study the effect of novel π-bridges, using carbazole as the donor group and cyanoacrylic acid as the anchorage group. Through the M06/6-31G(d) level of theory, ground state geometry optimization, vibrational frequencies, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and their energy levels were calculated. Further, chemical reactivity parameters were obtained and analyzed, such as chemical hardness (η), electrophilicity index (ω), electroaccepting power (ω+) and electrodonating power (ω-). Free energy of electron injection (ΔGinj) and light-harvesting efficiency (LHE) also were calculated and discussed. On the other hand, absorption wavelengths, oscillator strengths, and electron transitions were calculated through time-dependent density functional theory with the M06-2X/6-31G(d) level of theory. In conclusion, the inclusion of thiophene groups and the Si heteroatom in the π-bridge improved charge transfer, chemical stability, and other optoelectronic properties of carbazole-based dyes.

Eight coumarin derivative dyes were studied by varying theπ-bridge size with different thiophene and thiazole units for their potential use in dye-sensitized solar cells (DSSC). Geometry optimization, the energy levels and electron density of the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital, and ultraviolet-visible absorption spectra were calculated by Density Functional Theory (DFT) and Time-Dependent-DFT. All molecular properties were analyzed to decide which dye was the most efficient. Furthermore, chemical reactivity parameters, such as chemical hardness, electrophilicity index, and electroaccepting power, were obtained and analyzed, whose values predicted the properties of the dyes in addition to the rest of the studied molecular properties. Our calculations allow us to qualitatively study dye molecules and choose the best for use in a DSSC. The effects ofπ-bridges based on thiophenes, thiazoles, and combinations of the two were reviewed; dyes with three units mainly of thiazole were chosen as the best photosensitizers for DSSC.

UV-Vis spectra were calculated using time-dependent density functional theory for the chrysanthemin pigment, which is used as natural dye in dye sensitized solar cells. To this end, we studied four different calculation protocols in order to obtain the best approximation according to the maximum absorption wavelength (λmax) of the experimental spectrum. Furthermore, the optimized geometry, highest occupied molecular orbitals, lowest unoccupied molecular orbitals and electron density were calculated and analyzed. Several chemical models were used with and without the presence of the chlorine atom: the chosen functionals, B3LYP, PBE0 and the M06 family, represent various approximations with different fractions of Hartree-Fock exchange energy. These functionals were combined with the 6-31+G (d), 6-311+G (d) and the MIDIX+basis sets. All of these calculation protocols proved a good option, though the B3LYP/MIDIX+chemistry model was the best for predicting the λmax value, using the equilibrium calculation protocol (M1a) in the presence of chlorine.

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Ten molecules were theoretically calculated and studied through density functional theory with the M06 density functional and the 6-31G(d) basis set. The molecular systems have potential applications as sensitizers for dye-sensitized solar cells. Three molecules were taken from the literature, and seven are proposals inspired in the above, including the azomethine group in the π-bridge expecting a better charge transfer. These molecular structures are composed of triphenylamine (donor part); different combinations of azomethine, thiophene, and benzene derivatives (π-bridge); and cyanoacrylic acid (acceptor part). This study focused on the effect that the azomethine group caused on the π-bridge. Ground-state geometry optimization, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and their energy levels were obtained and analyzed. Absorption wavelengths, oscillator strengths, and electron transitions were obtained via time-dependent density functional theory using the M06-2X density functional and the 6-31G(d) basis set. The free energy of electron injection (ΔGinj) was calculated and analyzed. As an important part of this study, chemical reactivity parameters are discussed, such as chemical hardness, electrodonating power, electroaccepting power, and electrophilicity index. In conclusion, the inclusion of azomethine in the π-bridge improved the charge transfer and the electronic properties of triphenylamine-based dyes.

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The use of supplementary cementitious materials as partial Portland cement substitutes in concrete is one of the best strategies for reducing carbon dioxide (CO2) emissions in the cement industry, and also improves the properties of concrete. When highly reactive calcined pozzolans such as metakaolin are used, the setting time of concrete is reduced, and the use of retardants is necessary. The effect of zinc oxide (ZnO) as a cement hydration retarder has already been investigated; however, the influence of zinc oxide on ternary mixtures is unknown and needs study. In this research, the effect of adding zinc oxide on the hydration, microstructure and compressive strength of ternary mixtures is studied using setting time and compressive strength tests, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis with differential scanning calorimetry and scanning electron microscopy. The results show that the hydration process of ternary pastes is delayed or even inhibited when the amount of zinc oxide in the paste is increased. With the addition of 0.5 wt.% zinc oxide, the initial setting time and compressive strength of ternary mixtures after 3 days of curing are similar to those of the cement paste without the addition of pozzolans and zinc oxide.