On the aim of finding the optimal solar cell structure which allows better efficiency, stability and reduced cost, a general study of a Methyl Ammonium lead Iodide CH3NH3PbI3 based perovskite solar cell is made. Three different electron transport material compounds ETMs; TiO2, ZnO and SnO2 are comparatively studied considering the same hole transport material HTM, Spiro-OMeTAD. The photovoltaic parameters, i.e. the open circuit voltage (Voc), the short circuit current (Jsc) and the power conversion efficiency (PCE) are performed considering the ETM layer thicknesses, and the defect densities in both interfaces ETM/Perovskite and Perovskite/HTM. It is found that solar cell with SnO2 present the highest PCE for almost all configurations. Finally, the optimized cell is simulated with different organic and inorganic HTMs such as PEDOT: PSS, Cul and CuSbS2.