Biaxial strain modulating optoelectronic responses in Janus MoTeSe monolayers

The modulation mechanism of biaxial strain (-9 % to 9 %) on the structural stability, electronic properties, and optical properties of Janus monolayer MoTeSe is systematically investigated based on first-principles density functional theory calculations. The pristine monolayer exhibits a direct bandgap of 1.277 eV. Under biaxial tensile strain, the bandgap narrows significantly, decreasing from 1.277 eV to 0.021 eV, thereby enhancing carrier mobility. Notably, a semiconductor-to-metal transition occurs at 9 % tensile strain. Conversely, biaxial compressive strain induces a shift from a direct to an indirect bandgap. Optical analysis reveals that tensile strain causes a red shift in the absorption peaks and relocates energy loss to lower energies. In contrast, compressive strain induces a blue shift in absorption, substantially increasing the absorption coefficient (from 1.062 × 10⁵cm^-1 to 1.278 × 10⁵cm^-1) and light-harvesting capability. Additionally, compressive strain elevates the static dielectric constant, reaching 3.061 at -9 % strain. The study reveals the role of biaxial strain in modulating the optoelectronic properties of Janus MoTeSe. It provides a theoretical basis for the design of tunable optoelectronic devices based on strain engineering.