Luminescent 3D chiral hybrid metal-halide perovskites for piezoelectric energy harvesting and ultrasound detection

Hybrid metal-halide perovskites (HMHPs) have received extraordinary attention due to their remarkable application potential in next-generation photoelectric devices. However, three-dimensional (3D) lead-free halide perovskites with piezoelectrics are rare. Here, we report the synthesis of a pair of chiral 3D piezoelectric HMHPs, [(<i>R</i>)-(+)-3-aminoquinuclidine]RbI₃ and [(<i>S</i>)-(-)-3-aminoquinuclidine]RbI₃ [(<i>R</i>-3AQ)RbI₃ and (<i>S</i>-3AQ)RbI₃], which exhibit a reversible order-disorder phase transition with temperature and near-yellow photoluminescence emission under ultraviolet irradiation. Theoretical calculations demonstrate that (<i>R</i>-3AQ)RbI₃ possesses a direct bandgap electronic structure, relatively low elastic properties, and large piezoelectric strain coefficients. The <i>d</i>₁₄ value (14.54 pC N^-1) is approximately 20 times larger than that of quartz crystals. Additionally, a polycrystalline film device of (<i>R</i>-3AQ)RbI₃ was fabricated, which shows favorable performance for piezoelectric energy harvesting. More importantly, this device exhibits exceptional underwater ultrasound detection performance, attributed to the low acoustic impedance (2.68-6.15 MRayl) of (<i>R</i>-3AQ)RbI₃, which matches well with water (1.5 MRayl). This work opens up new avenues for utilizing 3D chiral lead-free halide perovskites in electromechanical sensing applications.