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This work reports density functional theory and time-dependent density functional theory calculations of the optimized geometries, electronic structures and optical properties of molecular dyes D1, D2, D3, D4, D5, and D6 formulated through substitution of 2-hexylthiophene to alizarin using the hybrid functional B3LYP and 6-31G (d,p) basis sets. The dyes are considered as potential pigments for dye-sensitized solar cells. For all dyes, HOMO/LUMO (Highest Occupied Molecular Orbital/Lowest Unoccupied Molecular Orbital) analysis results in positive outcomes upon electron injection to semiconductors and subsequent dye regeneration by the electrolyte. It is found that charge transfer is from the thiophene and unsubstituted ring of alizarin to the substituted ring of alizarin containing C=O and OH groups. The C=O groups are observed to be very important in strengthening the dyes as they are revealed to be the anchoring group bonding to the TiO2 semiconductor. Comparatively, dye D6 is observed to possess high absorption ability and electron injection power through a study of the light-harvesting efficiency and injection driving force (Δ Ginject). The estimated values of open-circuit voltage ( Voc) for the computed dyes are also presented. Decisively, all the considered dyes prove to be useful as potential photosensitizers in solar cells using a TiO2 semiconductor and [Formula: see text] coupling electrolyte.

In this study, the geometrical structure and vibrational spectra of the trimer molecule Rb 3 F 3 and ionic clusters Rb 2 F + , RbF 2-, Rb 3 F 2 + , and Rb 2 F 3 were studied by density functional theory (DFT) with hybrid functional B3P86 and Møller-Plesset perturbation theory of second order (MP2). The effective core potential with Def2-TZVP (6s4p3d) basis set for rubidium atom and aug-cc-pVTZ (5s4p3d2f) basis set for fluorine atom were used. The triatomic ions have a linear equilibrium geometric structure of D∞ h symmetry, whereas for pentaatomic ions Rb 3 F 2 + , Rb 2 F 3 and trimer molecule Rb 3 F 3 different isomers have been revealed. For the ions Rb 3 F 2 + , Rb 2 F 3 three isomers were confirmed to be equilibrium; the linear (D∞ h), the planar cyclic (C 2v) and the bipyramidal (D 3h) while for trimer Rb 3 F 3 , two isomers were found; the hexagonal (D 3h) and the "butterfly-shaped" (C 2v) configuration.

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/cm 2 and 0.612, respectively. The conversion efficiency of the cell using the synthesized dye HDD was found to be 5.81% under 100 mW/cm 2 solar illuminations. keywords Dye-sensitized solar cell • Photovoltaic properties • Photo-sensitizer • Photocurrent density • Photovoltage

The geometrical structure and the vibrational spectra of dimer Rb 2 Cl 2 , trimer Rb 3 Cl 3 , tetramer Rb 4 Cl 4 molecules and heptaatomic Rb 4 Cl 3 + , Rb 3 Cl 4 ions were studied. The cluster molecules and ions had been detected in equilibrium vapour over rubidium chloride previously. The quantum chemical calculations by DFT with hybrid functional B3P86 and MP2 methods were performed. The effective core potential with Def2-TZVP (6s4p3d) basis set for rubidium atom and full electron aug-cc-pVTZ (6s5p3d2f) basis set for chlorine atom were used. The equilibrium configuration was confirmed to be rhomb of symmetry D 2h for dimer Rb 2 Cl 2 , distorted cube (T d) for tetramer Rb 4 Cl 4 and polyhedral (C 3v) for heptaatomic ions Rb 4 Cl 3 + and Rb 3 Cl 4-. For the trimer molecule Rb 3 Cl 3 two isomers have been revealed: hexagonal (D 3h) and butterfly-shaped (C 2v), the latter has lower energy and is proved to be predominant in equilibrium vapour in a broad temperature range.