Successive near-room-temperature dielectric phase transitions in a lead-free hybrid perovskite-like compound

Solid–solid phase transition materials have attracted increasing attention because of their variety of applications in optoelectronic devices, data storage, and ferroelectric field-effect transistors. Hybrid organic–inorganic perovskite materials combine the characteristics of organic and inorganic components and thus might be promising candidates to obtain phase-transition materials. Here, we report a lead-free organic–inorganic hybrid (hexamethyleneimine)2BiBr5 (1), which displays successive phase transitions at 268 K, 304 K and 311 K upon heating; these phase transitions are induced by the distorted configurational change in organic cations and slight reorientational displacement of [BiBr5]n2− polyanionic zigzag chains. In addition, the UV/Vis optical spectrum indicates that 1 has an indirect bandgap of 2.70 eV. Furthermore, computational analyses disclose that the inorganic perovskite-like building blocks of 1 contribute significantly to its semiconducting properties. This study offers a pathway to explore new lead-free organic–inorganic hybrids with phase transition.