Tribo-Piezoelectric Energy Conversion in Bilayer ScN: A First-Principles Investigation

Abstract The strong ionic character and inherent non-centrosymmetric nature of two-dimensional (2D) scandium nitride (ScN) suggest a pronounced out-of-plane piezoelectric response, positioning it as a potential candidate for next-generation nano-energy harvesting. However, the extent to which tribologically driven interlayer interactions can modulate its electromechanical performance has not been systematically established. Here, we investigate the tribo-piezoelectric behavior of bilayer ScN using first-principles density functional theory (DFT) calculations. In-plane sliding and out-of-plane compression are systematically introduced to the ScN bilayer to probe variations in potential energy, polarization, charge redistribution, shear strength, induced voltage, and power density. The analysis indicates that interlayer sliding, accompanied by a transition in stacking configuration, promotes a marked enhancement in out-of-plane polarization, suggesting a strong coupling between structural registry and piezoelectric response. Under vertical compression, the system exhibits an energy corrugation range of 4799.12–7138.83 meV and a corresponding shear strength of 11.19–24.89 GPa, reflecting increased interlayer resistance during mechanical deformation. This behavior gives rise to an induced voltage of ∼1.44 V, highlighting the sensitivity of the bilayer to external mechanical perturbations. We proposed a compression–sliding nanogenerator model, which achieved a maximum theoretical output power density of 464.7 mW cm–2. These findings indicate that controlled interlayer modulation in ScN provides an effective mechanism for enhancing tribo-piezoelectric energy conversion, highlighting its potential in self-powered devices, wearable systems, and miniaturized electronic technologies.