1,2,4-Azadiphosphole-based piezoelectric penta-CNP sheet with high spontaneous polarization

Miniaturizing piezoelectric devices calls for the rational design of two-dimensional (2D) materials with outstanding piezoelectric response and good synthetic feasibility. Here we propose a new ternary 2D pentagonal structure named penta-CNP by assembling the precursor of 1,2,4-azadiphosphole molecule. Based on state-of-the-art theoretical calculations, we find that penta-CNP is dynamically, thermally and mechanically stable with a direct band gap of 2.62 eV, and is anisotropic in its mechanical properties with a negative Poisson’s ratio in the [1 1 0] direction. Due to its non-centrosymmetric geometry and semiconducting characteristic, penta-CNP possesses a large spontaneous polarization of 4.33 × 10−10 C/m and significant intrinsic piezoelectric response with d16 = 1.80 pm/V, surpassing the previously reported penta-BCN because of the larger size of phosphorous atom. This study expands the family of 2D ternary pentagonal structures for piezoelectric applications.