Improved energy storage performance of P (VDF-TrFE-CFE) films by growing superficial AlN insulation Layer

Ferroelectric polymers, such as PVDF and its copolymers, have attracted much attention because of their high dielectric constants, which exhibit great potential for use as capacitive films. However, serious polarization loss and conduction loss at high electric fields limit their wider application. In this study, magnetron sputtering was used to grow AlN insulation layer on the surfaces of P(VDF-TrFE-CFE) (PVTC) ferroelectric films. The microstructure of AlN/PVTC/AlN films, abbreviated as APA, and the effects of the AlN layer on the dielectric and energy storage properties were systematically studied. The results demonstrate that the growth of the AlN insulation layer can suppress electric charge injection and improve the insulation properties compared with those of pristine PVTC films. APA films with a 150 nm AlN layer possess a superior electric breakdown strength of 544.1 kV/mm and a reduced leakage current density. In particular, a decrease in the conduction/polarization loss and an increase in the dielectric constant were obtained in the APA-150 nm composite films. An energy storage density of 15.87 J/cm 3 and an efficiency of 55% were obtained at an electric field of 540 kV/mm, which is superior to those of pristine PVTC films. The results indicate that depositing a superficial insulation layer on dielectric films may be a good way to improve energy storage properties.