Achieving Ultrahigh Piezoelectricity in Organic–Inorganic Vacancy-Ordered Halide Double Perovskites for Mechanical Energy Harvesting

Piezoelectric charge coefficient (d33) and piezoelectric voltage coefficient (g33) are the two most critical parameters that define output performance of piezoelectric nanogenerators (PNGs). Herein, we propose a vacancy-ordered double perovskite of TMCM2SnCl6 (where TMCM is trimethylchloromethylammonium) with a large d33 of 137 pC/N and g33 of 980 × 10–3 V·m/N. The piezoelectric coefficients are considered from the halogen-bonding-mediated synergistic movements of atomic displacement in inorganic [SnCl6]2– octahedrons, as well as the molecular rotation of organic TMCM+, which is revealed by a combined density functional theory (DFT) and experimental study. The TMCM2SnCl6 possesses a high saturated polarization (Ps) of 8.7 μC/cm2, a high Curie temperature (Tc) of 365 K, and a low coercive field (Ec) of 0.6 kV/cm. The output voltage (Voc) and current (Isc) of the PNGs are 81 V and 2 μA at an applied mechanical excitation of (4.9 N, 40 Hz). We hope this work will provide guidance in energy harvesting by innovatively designing highly piezoelectric perovskites for the PNGs.