Optoelectronic Properties Prediction of Lead-Free Methylammonium Alkaline-Earth Perovskite Based on DFT Calculations

Dynamical stability plays an essential role in phase transition and structure, and it could be a fundamental method of discovering new lead-free perovskite materials. The perovskite materials are well-known for their excellent optoelectronic properties, but the lead element inside could be a hindrance to future development. This research is trying to predict the promising cation candidates in the high-temperature application for lead-free perovskite materials from the replacement of lead in MAPbCl₃ (MA = methylammonium) with alkaline-earth cations. The alkaline-earth cations are of a stable positive divalent sort, which is the same as Pb, and most of them are abundant in nature. Therefore, by improving the dynamical stability, the Mg²⁺, Ca²⁺, and Sr²⁺ cations replacement of lead ions could stabilize the perovskite structure by decreasing the imaginary part of phonon density of states. Finally, the density functional theory results show that the MACaCl₃ could be a dynamic stable lead-free methylammonium perovskite material with an ultrawide band gap (5.96 eV).