ABSTRACT To overcome the challenge of simultaneously enhancing breakdown strength and dielectric constant in polymer dielectrics, this study proposes a simple layer‐by‐layer casting method to prepare a three‐layer film. The structure features outer layers of PMMA/g‐C 3 N 4 /PVDF for high breakdown strength and a central g‐C 3 N 4 /PVDF layer for high dielectric constant. This “high‐breakdown–high‐dielectric–high‐breakdown” design promotes electric field redistribution and interfacial polarization, maintaining a high dielectric constant (7.26 at 100 Hz) even with 50 wt% PMMA. Moreover, the insulating PMMA outer layers introduce deep charge traps, while embedded g‐C 3 N 4 nanosheets extend carrier migration paths, synergistically inhibiting electrical treeing. Consequently, the three‐layer film achieves a breakdown strength of 647.57 MV/m at 50 wt% PMMA, about 1.15 times that of a single‐layer PCP film (568.1 MV/m). More importantly, the simultaneous enhancement of polarization and breakdown strength yields an energy density of 8.22 J/cm 3 , 2.3 times that of pure PVDF (3.51 J/cm 3 ). This work demonstrates a structural design strategy for breakthrough polymer dielectric performance, offering a new approach to high‐performance organic dielectric films.
Lu et al. (Mon,) studied this question.