Unraveling the highly anisotropic optoelectronic, mechanical, and piezoelectric properties of monolayer SbP3

Low-symmetry, non-centrosymmetric two-dimensional materials offer a promising basis for applications in multifunctional nanoelectronic devices. In this study, we utilize density functional theory calculations coupled with particle swarm optimization to design a monolayer polymorph of SbP3 that exhibits monoclinic Pc symmetry and good stability (M-SbP3). M-SbP3 demonstrates excellent phonon-limited electron mobility of 3525 cm2 V−1 s−1 at room temperature, with an ultrahigh anisotropy ratio of 108, which is four times the previously reported maximum value. Additionally, its optical absorption anisotropy ratio, reaching up to 13.3, is greater than that of most known two-dimensional low-symmetry materials. Due to the high anisotropy of the Young's modulus, the in-plane and out-of-plane Poisson ratios can achieve positive values of 1.29 and 1.91, as well as negative values of −0.43 and −0.88. Furthermore, our results reveal two opposite piezoelectric responses in M-SbP3, with significant in-plane piezoelectric coefficients of up to 50.5 × 10−10 and −86.6 × 10−10 C/m, respectively. These responses are primarily influenced by the clamped-ion term and may be associated with the high anisotropy of the electronic structure. Moreover, the electrical auxetic effects are a natural consequence of the high anisotropic piezoelectric responses. The highly anisotropic optoelectronic, mechanical, and piezoelectric properties, along with the coexisting mechanical and electrical auxetic effects, make M-SbP3 a promising component for multifunctional nanoelectronic devices.