In this work, a series of ruthenium azopyridine complexes was studied theoretically as a sensitizer in Dye Sensitized Solar Cells (DSSCs) using density functional theory (DFT) and time-dependent DFT (TD-DFT). These dyes derive from ruthenium azopyridine complex RuCl2(Azpy)2 considered as the reference by grafting an anchoring group (-COOH). Hens, 4-Hmazpy, 5-Hmazpy and O-Hazpy ligands as well as Azpy were studied. For the four ligands, 20 isomers expected are studied. In order to explore their photoelectrical properties, the ground state and excited state properties of the isolated dyes have been calculated at B3LYP/LANL2DZ level. And the same work was done with the dye RuCl2(5Hmazpy)2 in interaction with titanium dioxide. Comparing to N3, the key parameters including the light harvesting efficiency (LHE), the electron injection driving force ΔG inject , the regeneration driving force ΔG regen , the open circuit voltage VOC, the life time τ and adsorption energy were all scrutinized in detail. It results from this calculation that the ruthenium azopyridine complexes can be used as sensitizer in DSSCs. This work has highlighted the predictive and the guiding role of the theoretical approach in the design and the conception of new dyes for solar cells.

Ground state geometries, natural bond orbital (NBO), analysis of frontier molecular orbitals (FMOs), analysis and spectral (RMN and UV-Visible) properties of five azopyridine ruthenium (II) complexes α-Cl, β-Cl, γ-Cl, δ-Cl and ε-Cl of RuCl 2 (Dazpy) 2 have been theoretically studied by the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods using two basis sets: Lanl2DZ and a generic basis set in gas or in chloroform solvent. Dazpy stands for 4,6-dimethyl-phenylazopyridine. Optimized geometry shows that, except β-Cl, all the other four isomers α-Cl, γ-Cl, δ-Cl and ε-Cl are C 2 symmetrical. Otherwise, a good agreement was found between experimental and the calculated geometry and NMR data. Moreover, Lanl2DZ effective core potential basis set provides good chemical shifts and geometric properties. Furthermore, the prediction of the frontier orbitals (Highest Occupied Molecular Orbital or HOMO and Lowest Unoccupied Molecular Orbital or LUMO) shows that the most active isomer suitable for electronic reactions is admitted to be δ-Cl. Besides, the NBO analysis indicates that the RuN is formed by the electron delocalization of lone pair atomic orbital of N 2 and N py to Ru. Also, the strongest interactions between LP(N) with LP*(Ru) and LP(Cl) with LP*(Ru) stabilize the molecular structure. In addition, NBO shows that the five d orbitals of Ru in the complex are organized so that there is no order of priority from one complex to another.

Optoelectronics properties as helical molecular fingerprints have been investigated on a set of Helicenes molecules, which form a particular class of compounds and exhibit both π-electron delocalization and chiral properties. In this paper, we investigate the IR and Raman signatures of four representative Helicenes: Hexahilicene (Hexa-Helicene), tetrathia-[7]-helicene (Helicene-4S), and its pyrrole (Helicene-4N) and furan analogs (Helicene-4O), under the visible wavelength of 532 nm. Correctly, the impact of the method of calculation on these signatures has been pointed out. The simulation of the IR and Raman signatures involves two different steps: the evaluation of the vibrational frequencies and normal modes and the calculation of the Cartesian derivatives of electric properties. While most of the time, all the quantities are evaluated with a single method, we believe that this should not be the case since both steps have not the same requirements in terms of computational methods. Density functional theory has been then used with different exchange-correlation functional and Coupled Perturbed Time-Dependent Hartree-Fock (CP-TDHF) for the electric properties investigations. It comes out of the results that B3LYP, B3P86, and PBE0, reproduces better experimental spectra. The impact of the electron correlation as view one the XC functional on the evaluation of the Cartesian derivatives of the electric properties were found to be somewhat limited. Overall, the most crucial point is to have an accurate description of the normal vibrational modes via the choice of appropriate XC functionals, which describe the experiment results.

Organic photovoltaic performance has been investigated about the fluorination effects as one part on the optoelectronic properties. The quantum chemical accuracy of the optoelectronic and structural properties based on D-A (Donor-Acceptor) conjugated copolymers as PDTPQ X -type (Poly-dithieno-pyrrol-Quinoxaline) has been tediously exposed. The Donor-Acceptor in the copolymers was in our case constitutes to the Donor part in the photovoltaic device, while the Acceptor starting is the PC 60 BM in the same device, which composed the photovoltaic solar cells. The choice of the Donor part in the copolymers was obtained by their HOMO-LUMO bandgap and UV-visible absorption. The bandgap of the Donor part must be higher than that of the Acceptor part for an untroubled charges transfer from the Donor to the Acceptor according to the photovoltaic principle. The substitution of fluorine atoms (0F, 1F, 2F) on the quinoxaline constituents is an effective way to low the HOMO and LUMO energy levels of the alternating copolymers. This fluorine effect has been explored on the optoelectronic properties such as the HOMO-LUMO band gap E gap energy, the fill factor FF, the open circuit voltage V oc , the electron transfer energy ∆E et , the excitation energy ∆E ex , the absorption wave length λ and the oscillator strength OS. The equilibrium geometry at the ground state, the electronic structures as the frontier orbital isosurface have been obtained under the caster of the density functional theory (DFT) assist by the time-dependent density functional theory (TD-DFT) with M05 as exchange-correlation functional to come with 6-311G(d,p) basis set. Calculations were performed both in vaccuum and Chlorobenzene (CB) solvent with IEFPCM quantum model. All this has been done with the aim to enhance the energy gap, the V oc values and the fill factor FF, which exposed the nanomorphology as the topology of the solar cells photoactive layers. The results of this study show that these promote compounds systems as in the fluorination order are excellent candidates to build photovoltaic device in aim to enhance the open-circuit voltage for donor-acceptor heterojunctions used in organic solar cells.