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. , 8 V) and 400 kV/cm ( i.e. , 20 V), respectively, an ultra-high Δ P (45 μC/cm 2 and 60 μC/cm 2 ), U E = U Rec / E (21 J⸱MV/cm 2 and 17 J⸱MV/cm 2 ), and U F = U Rec /(1– η ) (20 J/cm 3 and 47 J/cm 3 ) 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 (Δ P ≈ 78 μC/cm 2 , U E ≈ 17.3 J⸱MV/cm 2 and U F ≈ 288 J/cm 3 ) due to their low leakage current density.