Abstarct: Solar cell is a device that converts sun light into electricity. In recent studies, there has been a special focus on organic and inorganic solar cells, particularly Perovskite ones. The reason behind this attempt is high energy absorption, low fabrication cost, and relatively high efficiency of this kind of solar cells. In this dissertation, simulation and optimization of Perovskite solar cells has been performed. All simulations have been done using Silvaco TCAD. In order to further improvement of a solar cell, it is vital to understand its performance mechanism. Among important factors affecting Perovskite solar cells performance, more light absorption, more carrier transmission, and high carrier mobility can be mentioned. In this regard, firstly TiO2 baxsed structure as ¬ITO/ TiO2/Perovskite/Spiro/Au has been investigated and simulated. Then for improving the solar cell performance, TiO2 has been replaced with multilxayer graphene as electron transfer laxyer. By applying AM1.5 standard spectrum to the solar cell and conducting an investigation into results, it has been concluded that the proposed graphene baxsed structure can achieve higher light absorption as a result of high transparency of graphene, more effective separation of charge carriers, and less recombination within the cell. Graphene has been employed because of its remarkable features as high carrier mobility, high transparency, and good optical, mechanical, and electrical properties. Final simulations has been performed on glass/ITO/Graphene/CH3NH3PbI3/Spiro/Au structure and baxsed on them photovoltaic parameters of the solar cell were obtained as Voc=1.09V, Jsc=25.15mA/cm2, and FF=74/01%. Power conversion efficiency of the proposed structure is 18.25%.