Tuning the electronic and optical properties of SnSe 2 /MgBr 2 heterostructures via biaxial strain and vertical electric field

Abstract Stacking structurally analogous two-dimensional (2D) materials to fabricate van der Waals heterostructures (vdWHs) has emerged as an effective strategy for achieving targeted material properties. Regarding the regulatory mechanisms governing enhanced optical absorption and bandgap modulation in SnSe 2 -based heterostructures, detailed investigations remain scarce. This work investigates the structural, electronic and optical properties of SnSe 2 /MgBr 2 vdWHs, selecting two representative configurations from multiple stacked arrangements. Biaxial strain and perpendicular electric fields can effectively modulate the bandgap, wherein compressive strain reaching −10% drives the system toward a semiconductor-to-metal transition. The application of an external electric field enables effective modulation of the bandgap. Notably, the bandgap of A 3 undergoes a sudden reduction when the field strength reaches 0.5 V Å −1 . The construction of the heterostructure significantly enhances the optical absorption capability of the monolayer. Compared with the constituent monolayers, optical absorption (UV to visible) is enhanced (maximum ~10 5 cm −1 ). These findings elucidate the tunable properties of SnSe 2 /MgBr 2 vdWHs, providing crucial theoretical guidance for optimising semiconductor sensors and photovoltaic devices based on 2D vdWHs.