Piezoelectric properties of CH₃NH₃PbI₃ perovskite thin films and their applications in piezoelectric generators

CH₃NH₃PbI₃ (MAPbI₃) perovskite thin films were applied to fluorine-doped SnO₂ (FTO)/glass and Au/Ti/polyethylene terephthalate (PET) substrates via a two-step process, which involved depositing a CH₃NH₃I (MAI) solution onto PbI₂ films via spin-coating followed by crystallization at temperatures of 100°C. The 500 nm-thick crystallized MAPbI₃ perovskite thin films showed a Curie temperature of ∼328 K, a dielectric permittivity of ∼52, a dielectric loss of ∼0.02 at 1 MHz, and a low leakage current density of ∼10^-7 A cm^-2 at ±3 V. The polarization-electric field (P-E) hysteresis loop and piezoresponse force microscopy (PFM) results showed that the films had well-developed ferroelectric properties and switchable polarization. Poling at an electrical field of 80 kV cm^-1 enhanced the power density of the generator. The values for output voltage and current density of the poled films reached 2.7 V and 140 nA cm^-2, respectively, which were 2.7-fold higher than those of the non-poled samples.