Theoretical investigation of the photovoltaic properties of MgSnN$_{2}$ for multi-junction solar cells

Abstract: The orthorhombic crystal structure of the MgSnN$_2$ compound with Pna2$_1$ symmetry has been investigated as a low-cost, non-toxic material for photovoltaic (PV) applications using density functional theory (DFT) and spectroscopic limited maximum efficiency (SLME) calculations. A detailed analysis of the electronic and optical properties was performed using the mBJ semilocal exchange functional. The bandgap of MgSnN$_2$ is found to be 2.45 eV. SLME photovoltaic analysis suggests that a thin film of MgSnN$_2$ with a thickness of 2 $μ$m can reach an efficiency of 13.17% at room temperature. This efficiency was further improved through the simulation of a multi-junction device, where the tandem configuration increased the efficiency from 12.80% (single-junction) to 22.42%. Furthermore, introducing cation disorder can further reduce the bandgap, enhancing its suitability for solar cell applications.