AbstractThree‐dimensional hybrid perovskite materials (CH3NH3PbI3) suffer from intrinsic instability owing to organic cation evaporation and ion migration. The inclusion of a large organic cation such as guanidinium has been probed to stabilize the structure. This work proposes the inclusion of imidazolium iodide (C3N2H5I) as an organic cation inside the CH3NH3PbI3 matrix, as a reservoir to control the spontaneous loss of iodide. The introduction of imidazolium iodide in amounts below 20 % has an impact on the crystallization process but not on the optical properties. It also positively controls non‐radiative recombination and improves the open‐circuit voltage of the solar cells. The present study paves way for a deeper insight into the limit of multi‐dimensional perovskite to further push the performance.