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Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non‐toxic composition. However, these perovskite‐like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite‐like hybrid ferroelectric with a formula [Me(Ph)3P]3[Bi2Br9] (MTPBB) and its mechanical energy harvesting capability. The Polarization‐Electric field (P‐E) measurements resulted in a well‐defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 μC cm−2. Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient (d33) for an MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt % of MTPBB in PDMS rendered a maximum peak‐to‐peak open‐circuit voltage of 22.9 V and a maximum power density of 7 μW cm−2 at an optimal load of 4 MΩ. Moreover, the potential of MTPBB‐based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors. [ABSTRACT FROM AUTHOR]

Organic ferroelectrics due to their low cost, easy preparation, light weight, high flexibility and phase stability are gaining tremendous attention in the field of portable electronics. In this work, we report the synthesis, structure and ferroelectric behavior of a two‐component ammonium salt 2, containing a bulky [Bn(4‐BrBn)NMe2]+ (Bn=benzyl and 4‐BrBn=4‐bromobenzyl) cation and tetrahedral (BF4)− anion. The structural analysis revealed the presence of rich non‐classical C−H⋅⋅⋅F and C−H⋅⋅⋅Br interactions in this molecule that were quantified by Hirshfeld surface analysis. The polarization (P) vs. electric field (E) hysteresis loop measurements on 2 gave a remnant polarization (Pr) of 14.4 μC cm−2 at room temperature. Flexible polymer composites with various (5, 10, 15 and 20) weight percentages (wt%) of 2 in thermoplastic polyurethane (TPU) were prepared and tested for mechanical energy harvesting applications. A notable peak‐to‐peak output voltage of 20 V, maximum current density of 1.1 μA cm−2 and power density of 21.1 μW cm−2 were recorded for the 15 wt% 2‐TPU composite device. Furthermore, the voltage output generated from this device was utilized to rapidly charge a 100 μF capacitor, with stored energies and measured charges of 156 μJ and 121.6 μC, respectively. [ABSTRACT FROM AUTHOR]