Superior Transverse Piezoelectricity in a Halide Perovskite Molecular Ferroelectric Thin Film

Piezoelectric materials with inherent mechanical-electric coupling effect are a crucial family of functional materials in high-end information technology. For practical applications, the transverse piezoelectric performance (d₃₁ or d₃₂) is mainly considered, because this parameter is a vitally important index to characterize the performance of piezoelectric thin films. However, the transverse piezoelectricity of the thin films as a key figure of merit is seldom mentioned in molecular ferroelectrics. Herein, we report that a new 1D halide perovskite ferroelectric N,N-dimethylallylammoniumCdCl₃ (DMAACdCl₃) exhibits an above room-temperature ferroelectric phase transition with a saturated polarization of 1.9 μC cm^-2 and a coercive field of 5.0 kV cm^-1. The thin film of DMAACdCl₃ is successfully fabricated using an easy processing spinning method and maintains well ferroelectric properties verified by piezoresponse force microscopy (PFM). More significantly, the ferroelectric thin film offers superior transverse piezoelectricity with an in-plane piezoelectric response of about 41 pC N^-1, which is about twice that of well-known piezoelectric polymer PVDF (21 pC N^-1). Transverse piezoelectricity has been scarcely studied in molecular ferroelectrics, and its exploitation would play an important role in the design of next-generation smart piezoelectric devices.