Band-gap engineering in Aurivillius BaBi4Ti4O15 thin film capacitors for enhanced energy storage performance

High-quality Aurivillius ferroelectric thin film capacitors have garnered extensive research interest due to their excellent insulating properties, anti-fatigue capabilities, and satisfactory energy storage performance. However, the relatively low energy density of these ferroelectric thin films impedes the miniaturization and integration of capacitor devices. In this work, we have designed a band-gap engineering strategy to enhance the dielectric breakdown strength, consequently improving the energy storage performance of BaBi4Ti4O15 (BBT) Aurivillius ferroelectric thin film capacitor. This engineering approach involves incorporating a broader band-gap BiInO3 (Eg ∼ 4.5 eV) into the BBT thin films (Eg ∼ 3.59 eV), thereby improving their insulating characteristics. Especially in the BaBi4Ti4O15-0.09BiInO3 (BBT-0.09BIO) thin film capacitor, an exemplary energy storage density ∼ 111.5 J cm−3 and efficiency ∼ 78.2 % under breakdown electric field of 4227 kV cm−1 are acquired. Furthermore, the BBT-0.09BIO thin film capacitor also demonstrates favorable thermal stability (ranging from 25 to 220 °C), frequency reliability (from 50 Hz to 10,000 Hz), and endurance over 107 fatigue cycles. This work paves the way for further exploration of band-gap engineering applications to enhance energy storage performance in capacitor technology.