First principles calculations of the optoelectronic properties of magnesium substitutes in Lead based ABX₃ compounds

Perovskites are potential materials for the fabrication of cheap and efficient solar cells with a suitable Electron Transport Layer (ETL) as base. Currently, the most efficient Perovskite Solar Cells (PSCs) are made of Methyl Ammonium Lead Iodide (MALI), CH₃NH₃PbI₃, typically with anatase ETL, which is toxic due to the presence of lead. Magnesium is a non-toxic potential substitute for lead in MALI PSCs. This study focuses on simulating and calculating the optoelectronic properties of magnesium based perovskites and comparing them with those of the lead-based perovskites, to know if they will serve as a better substitute for lead (due to its high toxicity). We performed atomistic simulations of Methyl Ammonium Magnesium Iodide (MAMI), CH₃NH₃MgI₃ and Methyl Ammonium Lead Iodide (MALI), CH₃NH₃PbI₃, both in the triclinic and orthorhombic phases, using Density Functional Theory within the Generalised Gradient Approximation using Ultra Soft Perdew-Burke-Enzherh of pseudopotentials. All atomistic simulations were done using well-converged k-points and cut-off energies. Results obtained showed that both MAMI and MALI possess similar optoelectronic properties in the triclinic and orthorhombic phases, strongly indicating that MAMI based perovskite materials are potential replacement candidates for fabricating cheap and efficient solar cells with little or no toxicity. (paper)