Ultra-high energy storage density and efficiency at low electric fields/voltages in dielectric thin film capacitors through synergistic effects

Ensuring reliable and safe operation of high-power electronic devices necessitates the development of high-quality dielectric nano-capacitors with high recoverable energy density (U_Rec) and efficiency (η) at low applied electric fields (E)/voltages. In this work, we demonstrate ultra-high U_Rec and η at low E <500 kV/cm in as-grown epitaxial relaxor ferroelectric (RFE) PMN-33PT films, rivaling those typically achieved in state-of-the-art RFE and antiferroelectric (AFE) materials. The high energy storage properties were achieved using a synergistic strategy involving large polarization, a giant built-in potential/imprint (five times higher than the coercive field), and AFE like behavior. The structural, chemical, and electrical investigations revealed that these achievements mainly arise from the effects of strain, dipole defects, and chemical composition. For instance, at low E, the capacitors exhibit under 160 kV/cm (i.e., 8V) and 400 kV/cm (i.e., 20V), respectively, an ultra- high ΔP (45 μC/cm² and 60 μC/cm²), U_E= U_Rec /E (21 J⸱MV/cm² and 17 J⸱MV/cm²), and U_F=U_Rec/(1–η) (20 J/cm³ and 47 J/cm³) with a robust charge-discharge fatigue endurance and outstanding frequency and thermal stability. Additionally, the designed films exhibit outstanding energy storage performance at higher E up to 2 MV/cm (ΔP ≈ 78 μC/cm², U_E≈ 17.3 J⸱MV/cm² and U_F≈ 288 J/cm³) due to their low leakage current density.