Phase‐Field Simulations of Tunable Polar Topologies in Lead‐Free Ferroelectric/Paraelectric Multilayers with Ultrahigh Energy‐Storage Performance

Dielectric capacitors are emerging energy‐storage components that require both high energy‐storage density and high efficiency. The conventional approach to energy‐storage enhancement is polar nanodomain engineering via chemical modification. Here, a new approach of domain engineering is proposed by exploiting the tunable polar topologies that have been observed recently in ferroelectric/paraelectric multilayer films. Using phase‐field simulations, it is demonstrated that vortex, spiral, and in‐plane polar structures can be stabilized in BiFeO3/SrTiO3 (BFO/STO) multilayers by tailoring the strain state and layer thickness. Various switching dynamics are realized in these polar topologies, resulting in relaxor‐ferroelectric‐, antiferroelectric‐, and paraelectric‐like polarization behaviors, respectively. Ultrahigh energy‐storage densities above 170 J cm−3 and efficiencies above 95% are achievable in STO/BFO/STO trilayers. This strategy should be generally implementable in other multilayer dielectrics and offers a new avenue to enhancing energy storage by tuning the polar topology and thus the polarization characteristics.