Strain-responsive PH-SiBiX monolayers: computational design of multifunctional 2D materials for piezotronic and optoelectronic applications

Abstract

Two-dimensional materials with coupled electromechanical and optoelectronic functionalities are highly desirable for next-generation adaptive devices, yet their design remains challenging due to the trade-off between piezoelectricity, auxeticity, and optical tunability. Here, we propose a class of transition metal-adsorbed PH-SiBiX (X = Sc–Cd) monolayers as a multifunctional platform via first-principles calculations. Ti-adsorbed PH-SiBiTi exhibits a record-high in-plane piezoelectric coefficient (d₁₁ = 13.057 pm V⁻¹), outperforming conventional 2D materials (e.g., MoS₂) and bulk quartz, while Co/Ni/Ru/Rh-adsorbed systems demonstrate negative Poisson's ratios (ν = −0.068 to −0.206) through hinge-like lattice deformations. The strain sensitive d–p orbital hybridization between transition metals and Bi/Si atoms governs both the giant piezoelectric response and visible-light absorption anisotropy (7.5–16%), enabling mechanical tuning of optoelectronic properties. Furthermore, strong spin–orbit coupling induces band splitting (Δ ∼ 50 meV) and shifts band extrema, suggesting potential for spin-valleytronic applications. By synergizing high piezoelectricity, auxetic behavior, and strain-tunable optical absorption, PH-SiBiX monolayers bridge the gap between theoretical design and practical applications in self-powered sensors, flexible optoelectronics, and mechanically adaptive energy harvesters. This work establishes a symmetry-guided paradigm for engineering 2D materials with on-demand multifunctionality.