Strain Engineering of Anisotropic Electronic, Transport, and Photoelectric Properties in Monolayer SnSeP.

In this study, we demonstrate that the SnSeP monolayer exhibits intrinsic anisotropic electronic characteristics with the strain-synergistic modulation of carrier transport and optoelectronic properties, as revealed by various levels of density functional theory calculations combined with the non-equilibrium Green's function method. The calculations reveal that -axis uniaxial compression of the SnSeP monolayer induces an indirect-to-direct bandgap transition (from 1.73 eV to 0.97 eV, as calculated by HSE06), reduces the hole effective mass by ≥70%, and amplifies current density by 684%. Conversely, -axis uniaxial expansion (+8%) boosts ballistic transport (/-axis current ratio > 10), rivaling black phosphorus. Notably, a striking negative differential conductance arises with the maximum / in the order of 10 under the 2% uniaxial compression along the -axis of the SnSeP monolayer. Visible-range anisotropic absorption coefficients (~10 cm) are achieved, where -4% -axis strain elevates the photocurrent density (6.27 μA mm at 2.45 eV) and external quantum efficiency (39.2%) beyond many 2D materials benchmarks. Non-monotonic strain-dependent photocurrent density peaks at 2.00 eV correlate with hole effective mass reduction patterns, confirming the carrier mobility of the SnSeP monolayer as the governing parameter for photogenerated charge separation. These results establish SnSeP as a multifunctional material enabling strain-tailored anisotropy for logic transistors, negative differential resistors, and photovoltaic devices, while guiding future investigations on environmental stabilization and heterostructure integration toward practical applications.