Pressure-Induced Stabilization of Sodium Halide Perovskites

Abstract

Halide perovskites with the chemical formula ABX 3 are promising materials for solar energy harvesting, with their Asite playing an important role in giving stability for the 3D cornersharing octahedron BX 6 , forming the perovskite structure. In its inorganic family, the perovskite A-site is usually occupied by Cs, and when lighter atoms such as Na and K are introduced, the perovskite structure becomes unstable compared to other crystal structures. Here, we show that relatively low pressures, ranging from 6.1 to 7.0 GPa, can stabilize Na-based perovskites. We have also found that the band gap energy of these compounds decreases as a function of pressure, revealing a transition from semiconducting to metallic behavior at pressures larger than 50 GPa. These results present a pathway for the stabilization of new perovskites that can be extended to other systems composed of small ions.