Ferroelectricity and Piezoelectric Energy Harvesting of Hybrid A(2)BX(4)-Type Halogenocuprates Stabilized by Phosphonium Cations

[Image: see text] Perovskite-structured compounds containing organic cations and inorganic anions have gained prominence as materials for next-generation electronic and energy devices. Hybrid materials possessing ferro- and piezoelectric properties are in recent focus for mechanical energy harvesting (nanogenerator) applications. Here, we report the ferroelectric behavior of A(2)BX(4)-type halogenocuprate materials supported by heteroleptic phosphonium cations. These lead-free discrete Cu(II) halides [Ph(3)MeP](2)[CuCl(4)] (1) and [Ph(3)MeP](2)[CuBr(4)] (2) exhibit a remnant polarization (P(r)) of 17.16 and 26.02 μC cm(–2), respectively, at room temperature. Furthermore, flexible polymer films were prepared with various weight percentage (wt %) compositions of 1 in thermoplastic polyurethane (TPU) and studied for mechanical energy harvesting applications. A highest peak-to-peak voltage output of 25 V and power density of 14.1 μW cm(–2) were obtained for the optimal 15 wt % 1-TPU composite film. The obtained output voltages were utilized for charging a 100 μF electrolytic capacitor that reaches its maximum charging point within 30 s with sizable stored energies and accumulated charges.