[C H N]PbBr : An ABX -Type Semiconducting Perovskite Hybrid with Above-Room-Temperature Phase Transition.

Organic-inorganic hybrid perovskites, with the formula ABX (A=organic cation, B=metal cation, and X=halide; for example, CH NH PbI ), have diverse and intriguing physical properties, such as semiconduction, phase transitions, and optical properties. Herein, a new ABX -type semiconducting perovskite-like hybrid, (hexamethyleneimine)PbBr (1), consisting of one-dimensional inorganic frameworks and cyclic organic cations, is reported. Notably, the inorganic moiety of 1 adopts a perovskite-like architecture and forms infinite columns composed of face-sharing PbBr octahedra. Strikingly, the organic cation exhibits a highly flexible molecular configuration, which triggers an above-room-temperature phase transition, at T =338.8 K; this is confirmed by differential scanning calorimetry (DSC), specific heat capacity (C ), and dielectric measurements. Further structural analysis reveals that the phase transition originates from the molecular configurational distortion of the organic cations coupled with small-angle reorientation of the PbBr octahedra inside the inorganic components. Moreover, temperature-dependent conductivity and UV/Vis absorption measurements reveal that 1 also displays semiconducting behavior below T . It is believed that this work will pave a potential way to design multifeatured perovskite hybrids by utilizing cyclic organic amines.