Enhanced Energy‐Storage Density and Resistive Switching Behavior in Lead‐Free Ba _0.7 Sr _0.3 TiO ₃ /Ba _0.6 Sr _0.4 TiO ₃ Multilayer Thin Films

Ferroelectric thin‐film capacitors are of interest for energy storage due to their high charge/discharge rates, essential for compact electronics. As alternatives to Pb‐based materials, environmentally friendly barium titanate–based systems show great energy‐storage potential. Herein, Ba 0.7 Sr 0.3 TiO 3 (BST7)/Ba 0.6 Sr 0.4 TiO 3 (BST6) thin films altering the layer structure are designed and constructed on boron‐doped Si <100> substrates by solution‐based spin‐coating method. The structural and electric properties of trilayer thin films are investigated, and the results are compared with those of monolayer thin films such as BST7 and BST6. An enhanced polarization and improved breakdown strength are simultaneously achieved in the BST767 (Ba 0.7 Sr 0.3 TiO 3 /Ba 0.6 Sr 0.4 TiO 3 /Ba 0.7 Sr 0.3 TiO 3 ) trilayer thin film caused by the interfacial effect, which leads to an ultrahigh energy‐storage density ( W rec ) of ≈56.9 J cm −3 accompanying an efficiency ( η ) of ≈72%. The BST767 trilayer capacitor processes a fast charging/discharging speed and a giant power density of 0.72 MW cm −3 . These thin‐film capacitors exhibit a relatively high resistive switching behavior with an improved on–off ratio compared to ceramic capacitors. The mechanisms underlying current conduction are thoroughly analyzed. Such performance makes them suitable for future portable electronics, hybrid vehicles, and aerospace applications.