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 piezoand ferroelectric and photovoltaic effects may be a practical answer to the rising energy demand. In this quest, piezoelectric polymer poly(vinylidene fluoridehexafluoroproylene) (P(VDF-HFP)) has gained interest due to its superior piezo-and ferroelectricity. In photovoltaic applications, inorganic halide perovskite (IHP) of CsPbI 3 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-CsPbI 3 through an electrospinning process at room temperature, encapsulated within a ferroelectric copolymer poly(vinylidene fluoridehexafluoroproylene) (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-CsPbI 3 . This tensile strain is triggered by the electrospinning process, which aids in the formation and growth of γ-CsPbI 3 . In the CsPbI 3 −P(VDF-HFP) composite nanofiber, γ-CsPbI 3 nucleates the polar β-crystalline phase in P(VDF-HFP), which results in the intrinsic piezo-and ferroelectric characteristics. The γ-CsPbI 3 aids in preferable molecular dipole orientation, resulting in improved nanoscale piezo-and ferroelectric properties. The composite nanofiber features a higher piezoelectric d 33 magnitude (∼30 pm/V) and lower decay constant for polarized domains (τ composite ≈ 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.

On-Demand MXene-Coupled Pyroelectricity for Advanced Breathing Sensors and IR Data Receivers

“…27,47 These transition dipoles can be correlated with different vibration modes and peak intensities observed at positions 1275 and 840 cm −1 for A 1 , 1075 and 1400 cm −1 for B 1 , and 1182 and 884 cm −1 for B 2 , respectively. 27,47 In the case of parallel mode measurements (Figure 2a, upper panel) for PVDF-MXene nanofibers, the intensity of B 1 (μ⃗ ∥c⃗ ) and B 2 (μ⃗ ∥a⃗ ) vibration bands increases significantly, corresponding to peak positions 1075 and 1400 cm −1 and 1182 and 884 cm −1 , respectively, while in the case of perpendicular mode IR measurements, the intensity of A 1 (μ⃗ ∥b ⃗ ) vibrational bands increases, corresponding to peak positions 1275 and 840 cm −1 . This observation indicates that the −CH 2 and −CF 2 dipoles are oriented perpendicular to the fiber chain axis in the case of PVDF-MXene fibers.…”

“…During this measurement, the fiber stretch axis in electrospinning is considered the z -axis and considered parallel to the IR beam for polarized FTIR measurement. To identify such changes under change in IR polarization, one needs to first identify the different vibrational transition dipole moments μ of PVDF that exists within the unit cell, defined as B 2 (μ⃗∥ a⃗ ), A 1 (μ⃗∥ b⃗ ), and B 1 (μ⃗∥ c⃗ ), as defined in the literature. , These transition dipoles can be correlated with different vibration modes and peak intensities observed at positions 1275 and 840 cm –1 for A 1 , 1075 and 1400 cm –1 for B 1 , and 1182 and 884 cm –1 for B 2 , respectively. , In the case of parallel mode measurements (Figure a, upper panel) for PVDF-MXene nanofibers, the intensity of B 1 (μ⃗∥ c⃗ ) and B 2 (μ⃗∥ a⃗ ) vibration bands increases significantly, corresponding to peak positions 1075 and 1400 cm –1 and 1182 and 884 cm –1 , respectively, while in the case of perpendicular mode IR measurements, the intensity of A 1 (μ⃗∥ b⃗ ) vibrational bands increases, corresponding to peak positions 1275 and 840 cm –1 . This observation indicates that the −CH 2 and −CF 2 dipoles are oriented perpendicular to the fiber chain axis in the case of PVDF-MXene fibers.…”