LAUSR

Recently, organic-inorganic hybrid perovskite has attracted increasingly attention because of its excellent piezoelectric and ferroelectric properties. In this letter, the first principles method was employed to analyze the piezoelectric properties of two-dimensional (2D) organic-inorganic perovskite (4-aminotetrahydropyran, ATHP)2PbX4(X = Cl, Br and I). The calculation shows that 2D (ATHP)2PbX4 has large out-of-plane dipole moment and excellent out-of-plane piezoelectric properties. Among them, the out-of-plane piezoelectric coefficient ${d}_{{31}}$ of 2D (ATHP)2PbI4 reaches 41.90 pm/V, which is about 8 times the out-of-plane piezoelectric coefficient ${d}_{{33}}$ of bulk material AlN, and one to two orders of magnitude larger than ${d}_{{31}}$ of most 2D piezoelectric materials. The electronic properties of 2D (ATHP)2PbX4 are calculated to reveal its energy band structure and charge density. The elastic tensors of 2D (ATHP)2PbX4 is calculated. The stress-strain analysis suggested the 2D (ATHP)2PbX4 has an ultra-soft mechanical flexibility. Our research shows that 2D (ATHP)2PbX4 is of great application value in various micro-nano piezoelectric devices.