A Chiral Edge-Sharing Bioctahedral Chlorobismuthate(III) Hybrid Ferroelectric and Its Application in Piezoelectric Energy Harvesting

Halogenobismuthate(III)-based organic-inorganic hybrid ferroelectrics integrate molecular dipoles arising from organic cations with intrinsic polarization originating from the inorganic backbones, offering a promising avenue for the development of environmentally benign and structurally tunable materials for advanced electronics. Although their potential in piezoelectric energy harvesting has rarely been explored, this study presents a novel chiral ammonium chlorobismuthate(III), <b>[(</b><i><b>S</b></i><b>)-NEA]</b>_<b>4</b><b>[Bi</b>_<b>2</b><b>Cl</b>_<b>10</b><b>]</b> ((<i>S</i>)-NEA represents (<i>S</i>)-1-(naphthalen-2-yl)ethan-1-ammonium), crystallizing in the polar space group <i>P</i>2₁ and exhibiting ferroelectric properties. Its noncentrosymmetric structure was further confirmed by second harmonic generation (SHG) measurements. Ferroelectric characterization using <i>P-E</i> hysteresis loop measurements revealed a saturation polarization (<i>P</i>_s) of 3.8 μC cm^-2. The microscopic ferroelectric domain structure was confirmed by the piezoresponse force microscopy (PFM) studies. For energy harvesting, <b>[(</b><i><b>S</b></i><b>)-NEA]</b>_<b>4</b><b>[Bi</b>_<b>2</b><b>Cl</b>_<b>10</b><b>]</b> was incorporated into a polycaprolactone (PCL) matrix to fabricate piezoelectric nanogenerator (PENG) devices. The composite with 15 wt % <b>[(</b><i><b>S</b></i><b>)-NEA]</b>_<b>4</b><b>[Bi</b>_<b>2</b><b>Cl</b>_<b>10</b><b>]</b> device exhibited the highest output voltage of 15 V, current density of 3.2 μA cm^-2, and power density of 4.6 μW cm^-2. The device demonstrated notable sensitivity and responsivity (0.44 V N^-1 and 274.9 V MPa^-1, respectively), a fast response time of 14.5 ms, and efficient energy storage, charging a 22 μF capacitor with 0.50 μJ within 400 s.