Piezoelectricity of Janus group-III monochalcogenide monolayers, multilayers and their vdW heterostructures: Insight from first-principles calculations

Using first-principles calculations, we have explored the piezoelectric properties of Janus multilayers and vdW heterostructures based on Janus group-III monochalcogenides. Our calculation results show that all the in-plane and out-of-plane piezoelectricity exists in Janus group-III monochalcogenide multilayers with the atomic radii difference and within intra-layer dipole moments affecting the e₃₃/d₃₃ value. For the vdW heterostructures, the e₃₃ depends on the stacking configuration and increases with the decreasing interlayer distance. Furthermore, the piezoelectric effect properties of the vdW heterostructures are independent of the biaxial strain. Our understanding of how the layer number and vdW integration affect the piezoelectric effect in 2D materials provides theoretical guidance for the experimental application of 2D Janus monolayer and their vdW heterostructures and will also contribute to the development of robust electrical-mechanical-coupled systems with large power densities and energy harvesting capabilities.