Stable Breakdown-Resistant Molecular Antiferroelectric Triggered by Confinement-Dependent Atomic Displacement.

Molecular antiferroelectrics (AFEs) with antiparallel dipole alignment are promising for energy-storage capacitor applications. However, it is challenging to design new molecular AFEs with superior breakdown resistance, owing to the lack of knowledge on the atomic-level origin regarding AFE orders. Here, we present stable breakdown resistance in 2D perovskite AFE, (2‑MBA)2CsPb2Br7 (2‑MBA = 2‑methylbutylammonium), involved with the confinement-dependent atomic displacement. It shows antiferroelectricity with a large spontaneous polarization of 5.0 µC/cm2. Particularly, the cage‑confined Cs+ cations display atomic displacement to create stable antifatigue merits, including high breakdown field up to 175 kV/cm and the fatigue endurance beyond ∼106 cycles, falling in the range of the highest level for molecular AFEs. Combination of energy barrier calculation and in situ solid-state NMR spectroscopy was used to reveal the crucial role of displacive dynamics. Contrary to order-disordering dynamics, it is the high energy barrier (Ea = 2.91 eV) of cage-confined Cs+ cation displacement that leads to the increase in Curie temperature (∼327 K) and forward coercive field (∼56.8 kV/cm). Such attributes allow for AFE switching under stronger external stimuli, thus endowing stable fatigue resistance even at higher breakdown fields. This work provides a feasible principle of delicately manipulating cage-confined dynamics to design new electric-ordered candidates.