High in-plane piezoelectricity of two-dimensional Janus BiOX (X = Cl, Br, and I) monolayers

Abstract

• The d 11 of the 2D Janus BiOI reached 34.36 pm/V. • The ternary bismuth-based compound BiXY exhibits the rule of d 11 (_Cl) < d 11 (_Br) < d 11 (_I). • The response of the BiOI model is sensitive, and its I-V curve and charge density change very regularly. Piezoelectric materials can realize the direct conversion of strain and voltage, and have been widely used in the field of energy supply of micro-nano devices and pressure sensing. Based on the unique Janus structure, the electronic structures and piezoelectric properties of the BiOX (X = Cl, Br and I) monolayers were systematically studied by using first principles calculations. The results of the calculations show that the BiOI monolayer exhibits a largest in-plane piezoelectric coefficients ( d 11 ) value of 34.36 pm/V, which is far higher than the previously reported two-dimensional (2D) materials, such as MoS 2 (3.73 pm/V) and BiXY (the largest BiSI is 23.11 pm/V), the sensitive and regular response of the BiOI model also broaden its application opportunities in micro-nano piezoelectric devices.