Unprecedented Ferroelectric-Antiferroelectric-Paraelectric Phase Transitions Discovered in an Organic-Inorganic Hybrid Perovskite.

As a promising candidate for energy storage capacitors, antiferroelectric (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization versus electric field (P-E) hysteresis characteristics in contrast to ferroelectrics and linear dielectrics. However, antiferroelectricity has only been discovered in inorganic oxides and some hydrogen-bonded molecular systems. In view of the structural diversity and unique physical properties of organic-inorganic hybrid system, it remains a great opportunity to introduce antiferroelectricity into organic-inorganic hybrid perovskites. Here, we report that polarizable antiparallel dipole arrays can be realized in an organic-inorganic hybrid perovskite, (3-pyrrolinium)CdBr, which not only exhibits an excellent ferroelectric property (with a high spontaneous polarization of 7.0 μC/cm), but also presents a striking AFE characteristic revealed by clear double P-E hysteresis loops. To the best of our knowledge, it is the first time that such successive ferroelectric-antiferroelectric-paraelectric phase transitions have been discovered in organic-inorganic perovskites. Besides, a giant dielectric constant of 1600 even at high frequency of 1000 kHz and a bulk electrocaloric effect with entropy change of 1.18 J K kg under 7.41 kV/cm are also observed during the phase transition. Apparently, the combined striking AFE characteristic and giant dielectric constant make (3-pyrrolinium)CdBr a promising candidate for next generation high-energy-storage capacitors.