Size effect on optical spectrum of coumarin nano molecule dyes via TD-DFTB and turbo-TDDFT approaches

In the dye sensitized solar cell, the dye molecules play the role of light absorption that is a key role in performance of the solar cells. One of the features that affect the optical spectrum of dyes is size of the nano molecules. In this paper, the optical spectrum of nano molecules of coumarin families was calculated with different sizes by using the Time-Dependent Density-Functional Tight-Binding and Time-Dependent Density-Functional methods. In this calculation, the HOMO-LUMO gap increases as the size of the dyes decreases in accordance with the experiment. Our computations confirm the 2 order of speed of first method compared to the second method. Finally, Time-Dependent Density-Functional Tight-Binding method proposed the S-cis Nkx-2311 with ZnO for the simulation of the dye sensitized solar cell.