Optimized energy storage performance in bilayer heterogeneous films

Film-based dielectric capacitors featured with small size, high breakdown field, and high energy storage density enable the application for integrated and miniatured electronic devices. So far, kinds of dielectrics have been explored for higher energy storage performance. Linear-like dielectrics can endure a high breakdown field but the polarization is too small. Conversely, ferroelectrics have high polarization but a low breakdown field, limiting their further performance optimization. Herein, we designed bilayer dielectric film capacitors that combined the linear-like dielectric layer and the ferroelectric layer, which brings in a redistribution of electric field owing to the different capacitance of each layer, thus improving the breakdown field and delaying the polarization saturation. Consequently, a high energy density of 57 J cm−3 with an efficiency of 88% was achieved. In addition, the bilayer film also exhibited excellent anti-fatigue and temperature-invariant characteristics, showing great potential for future applications in dielectric energy storage.