Stability and electronic properties of two-dimensional metal–organic perovskites in Janus phase

Two-dimensional (2D) hybrid metal–organic perovskites have been widely studied due to their good stability and unique optoelectronic properties. By incorporating different ligands on opposite sides of the inorganic octahedron plane, we construct a novel 2D Janus perovskite (2D-JP) exhibiting structural out-of-plane symmetry-breaking. Our first-principles calculations show that the proposed 2D-JPs have thermodynamic stability comparable to that of the corresponding non-Janus perovskites. By modifying the passivating ligands or the thickness of the perovskite phase, we show that the band gaps and the carriers’ effective masses of the 2D-JPs can be modulated up to 0.29 eV and 0.27me, respectively, compared to the non-Janus materials. Furthermore, the structural out-of-plane asymmetry of 2D-JPs leads to the asymmetrical distribution of electrostatic potential and band edge charge density, which facilitates the separation of electrons and holes. Furthermore, we explored the stability and the electronic structures of Ruddlesden–Popper layered Janus perovskites with two different stacking methods. Our results provide a new approach to regulate the electronic properties by constructing 2D-JPs for practical applications in electronic and optoelectronic devices.