Giant Band Gap Narrowing under Hydrostatic Pressure in (4FP)₂SnI₄ Halide Perovskite

One of the most intriguing properties of hybrid halide perovskites is their structural softness. The interplay between organic and inorganic sublattices leads to a multitude of physical phenomena that are not observed in conventional semiconductors such as III-V materials. One among these is the exceptional band gap tunability under hydrostatic pressure. In this context, tin-based perovskites exhibit a more pronounced effect than their lead-based counterparts. Here, we report on one of the largest band gap tunabilities in this material family. The studied material, layered tin-based (4FP)₂SnI₄ perovskite, exhibits an exceptionally strong pressure sensitivity, with a band gap shift of up to -160 meV/GPa at room temperature. Combined experimental and computational studies reveal that its band gap dependence on pressure remains linear in the 0-5 GPa range, making (4FP)₂SnI₄ highly attractive for pressure-sensor applications.