We show that partial substitution of up to 30% Ni 2+ into MAPbI3 thin films is possible while retaining the 3D perovskite structure. Ni 2+ concentrations above 30% result in new low dimensional perovskite phases and unconverted NiI2 precursor. We do not observe correlations between unit cell parameters and Ni 2+ concentration, which suggests that Ni 2+ does not mix uniformly and may not substitute into the B site of the ABX3 perovskite as anticipated. The bandgap the mixed materials ranges from 1.3 -1.6 eV and is enhanced in the visible region with the incorporation of Ni 2+ , which is optimal for a solar cell device. However, emission quenching suggests that Ni 2+ may introduce new low-lying states that act as charge carrier traps which would limit device performance. Additionally, the significant water sensitivity of the materials limits the potential application of these materials in solar cells. Thus, we conclude that given the conditions presented in this paper, Ni 2+ is not a good candidate for Pb 2+ replacement in thin-film MAPbI3 solar cells prepared under these conditions.