Molecular Disorder Induces an Unusual Phase Transition in a Potential 2D Chiral Ferroelectric Perovskite
Lin Sui Li, Wen Juan Wei, Hong Qiang Gao, Yu Tan, Xiao Han
Abstract
Abstract Two‐dimensional hybrid halide perovskites with single chiral and ferroelectricity together with various structural phase transitions provide the possibility for more diverse functional properties. Here, we present a 2D chiral hybrid halide perovskite ferroelectric, [C 6 H 5 (CH 2 ) 4 NH 3 ] 2 CdCl 4 (4PBA−CdCl 4 , 4PBA=4‐phenylbutylamine) that experiences two continuous phase transitions from centrosymmetric triclinic P to polar chiral monoclinic P 2 and then to another centrosymmetric tetragonal P 4 /mmm with increasing temperature, accompanied by symmetry breaking, due to the prominent octahedral distortion and disorder transformation of organic 4PBA cations. In the polar chiral phase, 4PBA−CdCl 4 gives a significant CD signal and has a moderate ferroelectric polarization of 0.35 μC/cm 2 . In addition, 4PBA−CdCl 4 occupies a wide band gap of 4.376 eV that is chiefly contributed by the inorganic CdCl 6 octahedron. This finding offers an alternative pathway for designing new phase transitions and related physical properties in hybrid halide perovskites and other hybrid crystals.