Traditional ferroelectric materials, such as lead zirconate titanate (PZT) ceramics, exhibit positive strain when subjected to an electric field along the polarization direction. In contrast, the piezoelectric polymer polyvinylidene fluoride (PVDF) and its copolymer P(VDF-TrFE) display unique negative strain properties. While extensive research has focused on understanding the origin and mechanisms of this negative strain, limited efforts have been directed toward regulating these properties. This study optimizes the electro-strain and ferroelectric properties of P(VDF-TrFE) piezoelectric films through the synergistic effect of PbTiO₃ nanosheets and an in-situ electrostatic field. Our results demonstrate that while the incorporation of PbTiO₃ nanosheets does not notably enhance ferroelectricity, it significantly improves electro-strain properties, particularly negative strain, which increases from −0.097% to −0.185%, an enhancement of 91%. Moreover, the ferroelectric polarization and positive strain of P(VDF-TrFE) are further enhanced under the combined influence of PbTiO₃ nanosheets and in-situ electrostatic field, increasing maximum polarization from 10.79 μC/cm² to 13.16 μC/cm², a 22% improvement, and positive strain from 0.213% to 0.267%, a 25% enhancement. We propose a possible mechanism for these improvements, attributed to the enhanced flexibility of the amorphous phase and increased content of polar β-phase in P(VDF-TrFE) films under this synergistic effect. This work highlights novel strategies for controlling the electro-strain and ferroelectric properties of P(VDF-TrFE) piezoelectric films.

Piezoelectric materials that can effectively convert natural mechanical energy into electrical energy without time and space constraints have been widely applied for energy harvesting and conversion. The piezocomposites with high piezoelectricity and flexibility have shown great promise for renewable electric energy generation that can power implantable and wearable electronics. This minireview aims to summarize the recent progress of the piezocomposites with different composite structures, as well as the role of the theoretical understandings and designs in the development of new piezoelectric nanogenerator materials. Thereinto, the most common composite structural types (0-3, 1-3, and 3-3) have been discussed systematically. Several strategies for high output performance of piezocomposites are also proposed on the basis of current experimental and simulation results. Finally, the review concludes with perspectives on the future design of flexible piezoelectric nanocomposites for energy harvesters.