Chiral 2D Halide Perovskites for Piezoelectric Energy Harvesting and Ultrasound Detection

Hybrid organic-inorganic perovskite (HOIPs) has emerged as a great promising class of piezoelectric materials due to their solution processability, ease of structural adjustment, and high piezoelectricity. However, to date, their energy application and ultrasound detection has been relatively unexplored. Here, a pair of chiral two-dimensional (2D) HOIPs, R-/S-[3MeOPEA]₂PbBr₄ (3MeOPEA=1-(3-Methoxyphenyl) ethylamine), were synthesized, and the structure, photoluminescence and piezoelectric properties are reported. Our results demonstrate these materials exhibit consistent broad PL peaks under 360 nm excitation and density functional theory (DFT) calculations reveal their direct bandgap characteristic. Moreover, the incorporation of chirality into the structure of R- and S-[3MeOPEA]₂PbBr₄ endows them with significant piezoelectric properties. 5 wt% R-[3MeOPEA]₂PbBr₄/PDMS (polydimethylsiloxane) composite film can generate a maximum open-circuit piezoelectric voltages (V_oc) of 1.98 V and short circuit currents (I_sc) of 0.50 μA upon a loading force of 2 N at 10 Hz. Additionally, the device can sensitively detect ultrasound waves underwater at varying distances of 3, 6, and 9 mm, with corresponding peak-to-peak voltage (V_p-p) responses of 52.3 mV, 41.1 mV, and 31.7 mV, respectively. Our research broadens the potential applications of multifunctional chiral 2D perovskite materials in the fields of piezoelectric energy harvesting and underwater ultra-sound detection.