High-energy density in dielectric film capacitors via interface engineering and polarization behavior regulation

High-performance dielectric film capacitors are crucial for energy storage applications and the modern electronics industry due to their high power density and ultra-fast charge–discharge speed. Herein, we report that high dielectric constant/high polarization coupled with low loss/low leakage characteristics has been achieved by optimizing the ratio of homogeneous/heterogeneous interfaces and paraelectric/ferroelectric phase within a sandwich structure of ferroelectric 0.85BaTiO3–0.15Bi(Mg0.5Zr0.5)O3 (BT-BMZ) and paraelectric SrTiO3 (STO) multilayer prepared on (110)-oriented 0.7 wt. % Nb-doped SrTiO3 (Nb:STO) substrates. The optimized sandwich structure of ferroelectric/paraelectric/ferroelectric film reaches an energy storage density of ∼124.15 J/cm3 with an efficiency of ∼74.6% at room temperature. In addition, the film exhibits excellent thermal stability over a wide temperature range from −100 to 300 °C while maintaining a high-energy storage density (e.g., ∼73.8 J/cm3 with an efficiency of ∼77.6% at 300 °C) due to its low leakage current and hysteresis loss. Our work demonstrates the feasibility and effectiveness of optimized sandwich structures in improving energy storage performance, providing a pathway for the design of high-performance film capacitors.