Nowadays, the exploding population causes increasing of consumption of different types of energies. The most consuming form of the energies are fossil, oil and gas fuels, which they are not renewable and will be running out in the near future. As a result, Human Being is interested to use of renewable resources such as solar energy that can turn into electrical energy by using different methods. One of these methods is the use of the solar cells. One types of solar cells, is dye solar cell which is cheap and has an acceptable efficiency and also has decorative applications. In this thesis, the dye molecules, which are used in dye solar cell, are studied by using Time-Dependent Density Functional Tight-Binding (TD-DFTB). TD-DFTB method is Time-dependent density functional theory (TDDFT) based on the Tight-Binding (TB) model. TD-DFTB method compared to the TDDFT method reduces computation time one or two orders of magnitude. In this thesis, gap of energies for some dye nano molecules which are used in the dye solar cell are calculated by TD-DFTB method and results of calculation are in accordance with experiment and other computational methods. The computational speed is about 2 orders of magnitude greater than TDDFT method. It seems among nano dye molecules, Opv3-cooh is more appropriate for a dye solar cell, because the energy gap of this molecule is in range of visible wavelengths, radiation of solar cell has the highest power in this range.