Paraelectric/ferroelectric bilayer
composites are promising candidates
for high-performance dielectric capacitors. However, the energy densities
of these composites need to be further improved to satisfy the miniaturization
of electronic devices. Herein, an Al2O3/P(VDF–HFP)
buffer layer is inserted between a paraelectric PMMA layer and a ferroelectric
P(VDF–HFP) layer, forming a novel trilayer structure. It is
interesting to find that the buffer layer effectively alleviates the
huge electric field gap between the P(VDF–HFP) layer and PMMA
layer, yielding substantially improved breakdown strengths (>600
kV/mm),
which are over 140% that of the bilayer P(VDF–HFP)/PMMA composite
(∼425 kV/mm). In addition, the introduction of the buffer layer
also results in improved interfacial polarization, hence, the moderately
elevated permittivity. Consequently, a high energy density of 10.03
J/cm3, which is about 260% that of the bilayer P(VDF–HFP)/PMMA
composite (∼3.9 J/cm3), is achieved at 600 kV/mm.
This work offers a facile strategy to achieve dielectric composites
with high breakdown strengths, which is illuminating for the design
of high-voltage energy-storage capacitors.