Human beings, due to the growing needs for energy and concern of the disadvantages of fossil fuels, environmental pollution, and consumption of resources has begun to use renewable energy resources. One of these resources that is clean, free and always available, is solar energy and one of the ways to use it, is manufacturing solar cells. There are different types of solar cells. Common solar cells including silicon solar cells, despite of their good efficiency have high production costs. In the meantime, dye sensitized solar cells have acceptable efficiency, traarency and high flexibility and because of their low manufacturing costs, are more considered. These cells formed of a thin layer of metal oxide semiconductors such as or , and the dye molecule on it. Dye molecule absorbs the radiation spectrum to cell and become excited. Afterward excited electron injection into the metal oxide conduction band leads to oxidation of the dye. By moving electrons between metal oxide particles, an electric field and then an electric current is created and this current is transferred through an external circuit to the electrolyte solution and dye molecule obtain electron from redox couple in the electrolyte solution and finally regeneration happens with returning to the ground state. So the role of redox couple is to transfer electrons. In this thesis dye sensitized solar cell based on nano dye molecule N3 has been investigated. The main focus is on the interface between the electrolyte-dye and the complexes that is formed due to regeneration of dye. In this thesis the calculation is done using the Quantum Espresso and FHI-aims packages that are pseudopotentials and full-potentials codes, respectively and validity of pseudopotentials has been confirmed through equality of calculated energy gap with both codes. The main target of this research is study of the absorption spectra of metalliferous dye molecule, N3, and its complexes using density functional theory and turbo-TDDFT code. We also determined the reaction path of dye regeneration by Nudged Elastic Band (NEB) method. IR spectrum and vibrational spectra (phonon spectrum in Gamma point) of various configurations of dye molecule were calculated. We also found that complexes of N3 dye molecule and transition states formed in reactions, are magnetic.