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)­CdBr3, which not only exhibits an excellent
ferroelectric property (with a high spontaneous polarization of 7.0
μC/cm2), 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–1 kg–1 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)­CdBr3 a promising candidate for next
generation high-energy-storage capacitors.