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.