Abstarct: In recent years, molecular electronics has attracted many researchers’ attentions due to their complementary with traditional silicon devices. The quantum behavior of these devices provides the basic capabilities in generating molecular optical-single molecular devices, plasmonic quantum resonances, single molecular optical switches, tunnel diodes, and quantum transistors. In this thesis, a single molecular solar cell was modeled using Density Function Theory (DFT) and Non-Equilibrium Green function (NEGF). In modeling procedure, primarily using the DFT method and simulation in Gaussian software, the states and energies of the two-part molecule at zero voltage point were obtained. Then, using the obtained results of this method, the Hamiltonian of system was formed and using the self-consistent field method and NEGF simulation in MATLAB software, the self-optical energy of the system and also the voltage-current curve of the device in different optical powers was obtained. According to the results of the simulations, it was found that this device is a single-molecular solar cell with an open-circuit voltage of 2 volts, and also its internal quantum efficiency for a single-mode input light with an energy of 3 electron volt is about 0.8 percent. The results showed that this device has the ability to make negative resistances at different voltages, such that the number and the interval voltage of negative resistance depends on the incoming light frequency and the electrodes' energy alignment (quantization). It was observed that increasing the power of the incoming light lead to an increase in size of the optical peaks, as well as increasing the number of optical modes, the number of peaks in the current-voltage curve increases.