Despite the high efficiency of the perovskite solar cells and the ease of their fabrication process, the presence of hysteresis is still known as an important challenge of the perovskite solar cells. In this study, it is shown that this undesirable phenomenon can be considerably mitigated by adding Cs to the structure of CH₃NH₃PbI₃. Although the exact reason of the hysteresis is still unknown, in this work, it is ascribed to the smaller radius of ionic migration of Cs, in comparison to organic cations such as CH₃NH₃ and improving the trap levels of perovskite.