Strain tunable high absorptivity and carrier mobility in two-dimensional multiferroic Cr₂SOCl₂ monolayer

Based on first-principles calculations, this paper presents a study on the stability, electronic structure, ferromagnetic, ferroelectric, and optical properties of Cr₂SOCl₂ monolayer. The calculations reveal that the Cr₂SOCl₂ monolayer is a typical magnetoelectric and bipolar magnetic semiconductor with a direct bandgap of 1.25 eV, where the ferromagnetic and ferroelectric ordering can coexist simultaneously below 76 K. The electronegativity difference between S and O atoms leads to a redistribution of charge, which drives the ferroelectric polarization of the Cr₂SOCl₂ monolayer. The application of uniaxial strain allows for the control of bandgap, light absorption, and carrier mobility in Cr₂SOCl₂ monolayer. Specifically, when a tensile strain is applied along the y direction, the monolayer undergoes a transition from the bipolar magnetic semiconductor to ferromagnetic half-semiconductor phase. At 12% strain, the absorptivity of Cr₂SOCl₂ monolayer can reach the maximum (∼8%) within the visible light range; moreover, the mobility of both electrons and holes is large in the x direction, but their difference is small, almost on the same order of magnitude. Based on these findings, we propose that Cr₂SOCl₂ monolayer under this strain could be a promising ferroelectric photovoltaic material for the absorption layer in solar cells.