Pressure-Induced Topological Nontrivial Phase and Tunable Optical Properties in All-Inorganic Halide Perovskites

Cesium-based all-inorganic halide perovskites CsMX₃ (M = Pb, Sn; X = Cl, Br, I) have been considered as important candidates for highly-efficient, chemically stable optoelectronic devices and solar cells. Pressure can serve as an effective and clean thermodynamic approach to better performance of CsMX₃. In this work, we use first-principles density functional theory calculations with both Perdew-Burke-Ernzerhof and GW + Bethe-Salpeter equation to systematically study the effects of pressure on the electronic structures, carrier transport, and optical properties of cubic phase CsMX₃. Our results show that with increasing hydrostatic pressure, the optical band gap red-shifts until the pressure reaches a critical value, above which the band inversion is observed due to the spin-orbit coupling. The resulting nontrivial topological gap blue-shifts with further increasing pressure. This work provides insights into the rational design of experiments to engineer the properties of CsMX₃ perovskites by applying pressure.