Colossal Electrocaloric Effect in an Interface-Augmented Ferroelectric Polymer.

The electrocaloric effect demands the maximized degree of freedom (DOF) of polar domains and the lowest energy barrier to facilitate the transition of polarization. However, optimization of the DOF and energy barrier-including domain size, crystallinity, multiconformation coexistence, polar correlation, and other factors in bulk ferroelectrics-has reached a limit. We used organic crystal dimethylhexynediol (DMHD) as a three-dimensional sacrificial master to assemble polar conformations at the heterogeneous interface in poly(vinylidene fluoride)-based terpolymer. DMHD was evaporated, and the epitaxy-like process induced an ultrafinely distributed, multiconformation-coexisting polar interface exhibiting a giant conformational entropy. Under a low electric field, the interface-augmented terpolymer had a high entropy change of 100 J/(kg·K). This interface polarization strategy is generally applicable to dielectric capacitors, supercapacitors, and other related applications.