Thermodynamic stability and electronic properties of 2D all-inorganic halogen perovskites

Abstract

Two-dimensional (2D) all-inorganic metal halide perovskites capture more attentions due to its superior stability compared with three-dimensional (3D) perovskites. However, the power conversion efficiency of 2D all-inorganic perovskite is needed to be largely improved and few theoretical research focuses on its structural stability and optoelectronic properties in depth. Herein, we exploit the electronic structure, thermodynamically stable phase, effective masses, and optical properties of Ruddlesden-Popper (RP) 2D inorganic perovskites Csn+1MnIn+1Cl2n (M = Pb or Sn, n = 1–4 and ∞) by employing density functional theory calculations. It is found that the most stable configuration is closely related to the specific position of the halogen atoms. Moreover, the thermodynamic stability of Pb-based 2D perovskites is further calculated based on the phase diagram, which is notably more stable than that of Cs2SnI2Cl2. In addition, our calculated results show that the band gaps decrease as the number of layers increase in both Sn- and Pb-based perovskites. Moreover, Sn-based 2D perovskites can be adjusted to superior electronic properties with the optimal bandgap ranging from 0.9 to 1.6 eV and small effective mass of carriers considering its future application. This systematic theoretical study provides a significant methodology for fabricating stable, new-type 2D inorganic photoelectric materials according to a reasonable stoichiometric ratio.