Ferroelectric Organic–Inorganic Hybrid Ammonium Halogenobismuthate(III) for Piezoelectric Energy Harvesting

Halogenobismuthate(III) compounds are of recent interest because of their low toxicity and distinct electrical properties. The utility of these materials as ferroelectrics for piezoelectric energy harvesters is still in its early stages. Herein, we report a hybrid ammonium halogenobismuthate(III) [BP_BrDMA]₂·[BiBr₅], crystallizing in a ferroelectrically active polar noncentrosymmetric Pna2₁ space group. Its noncentrosymmetric structure was confirmed by the detection of the second harmonic generation response. The ferroelectric P–E hysteresis loop measurements on the thin film sample of [BP_BrDMA]₂·[BiBr₅] gave a saturation polarization (P_s) of 5.72 μC cm^–2. The piezoresponse force microscopy analysis confirmed its ferroelectric and piezoelectric nature, showing characteristic domain structures and signature hysteresis and butterfly loops. The piezoelectric energy harvesting attributes of [BP_BrDMA]₂·[BiBr₅] were further probed on its polylactic acid (PLA) composites. The 15 wt % [BP_BrDMA]₂·[BiBr₅]-PLA polymer composite resulted in a high output voltage of 26.2 V and power density of 15.47 μW cm^–2. The energy harvested from this device was further utilized for charging a 10 μF capacitor within 3 min.