Discovery of an Unprecedented Above-Room-Temperature Antiferroelectric in Two-dimensional Hybrid Perovskite.

Antiferroelectric materials have been regarded as promising candidate for electronic energy storage devices, due to their natural double polarization versus electric field ( P- E) hysteresis loops. Currently, two-dimensional organic-inorganic hybrid perovskites with structural diversity and tunability, have received blooming interests, whereas above-room-temperature antiferroelectrics are still unreported in this perovskite system. Herein, for the first time, we successfully acquire a two-dimensional Ruddlesden-Popper hybrid perovskite antiferroelectric, ((CH3 )2 CHCH2 NH3 )2 CsPb2 Br7 (1), which shows an above-room-temperature Curie temperature at 353 K, trigging by the synergistic dynamic motion of inorganic Cs atoms and organic i-BA cations. Intriguingly, the antiferroelectric-ity of 1 existing over a wide temperature range of 298~353 K are revealed by the distinct double P- E hysteresis loops. Besides, 1 possesses remarkable energy storage efficiency up to 69%, comparable to those of some reported inorganic antiferroelectric ceramics, promoting 1 potential application in energy storage devices. This work provides an avenue to construct novel antiferroelectric materials for high-performance electronic device applications.