Piezoelectric–flexoelectric coupling in bent Janus MoSSe: An analytical modeling and first-principles study

Abstract

Bent structures exhibit considerable potential for applications in flexible electronics and sensor technologies. Two-dimensional Janus transition metal dichalcogenides offer an ideal platform for investigating piezoelectric–flexoelectric coupling effects in curved systems, owing to their inherent out-of-plane structural asymmetry. However, existing studies often rely on effective coefficients to approximate electromechanical properties, leading to significant inaccuracies in distinguishing between piezoelectric and flexoelectric contributions. In this work, we focus on monolayer Janus MoSSe and develop an analytical model that precisely captures bending-induced strain and strain gradients. Combined with DFT calculation, the piezoelectric coefficients (e11, e13) and flexoelectric coefficients (μ111, μ422) are successfully separated through polarization decomposition and fitting models. Furthermore, we observe that bending causes the valence band maximum and conduction band minimum to separate in real space and accumulate toward both ends, resulting in a nested type I band alignment. This work overcomes the limitations of traditional simplified models, deepens the understanding of electromechanical coupling mechanisms in two-dimensional Janus materials, and provides theoretical support for designing highly sensitive electromechanical devices.