Utilizing Strain-Engineered Stable Halide Perovskite for Interfacial Interaction with Molecular Dipoles To Enhance Ferroelectric Switching and Piezoresponse in Polymer Composite Nanofibers.

Abstract

Mechanical and solar to electrical energy conversion using piezo- and ferroelectric and photovoltaic effects may be a practical answer to the rising energy demand. In this quest, piezoelectric polymer poly(vinylidene fluoride-hexafluoroproylene) (P(VDF-HFP)) has gained interest due to its superior piezo- and ferroelectricity. In photovoltaic applications, inorganic halide perovskite (IHP) of CsPbI3 is considered a prime model compound. However, its application is limited because of the photoactive perovskite phase instability at ambient conditions. Here, we report the in situ synthesis of the stable perovskite γ-CsPbI3 through an electrospinning process at room temperature, encapsulated within a ferroelectric copolymer poly(vinylidene fluoride-hexafluoroproylene) (P(VDF-HFP)) as a composite nanofiber. Computational calculation using density functional theory (DFT) reveals that tensile strain plays a critical role in the dynamical stabilization of γ-CsPbI3. This tensile strain is triggered by the electrospinning process, which aids in the formation and growth of γ-CsPbI3. In the CsPbI3-P(VDF-HFP) composite nanofiber, γ-CsPbI3 nucleates the polar β-crystalline phase in P(VDF-HFP), which results in the intrinsic piezo- and ferroelectric characteristics. The γ-CsPbI3 aids in preferable molecular dipole orientation, resulting in improved nanoscale piezo- and ferroelectric properties. The composite nanofiber features a higher piezoelectric d33 magnitude (∼30 pm/V) and lower decay constant for polarized domains (τcomposite ≈ 17). The composite was utilized as a piezoelectric nanogenerator to demonstrate human physiological motion monitoring in self-power mode. The relevant pressure sensitivities of 81 and 40 mV/kPa for the low-pressure (<0.6 kPa) and high-pressure (>0.6 to 12 kPa) ranges, respectively, promise its suitability in the health care sector.