Remarkable Enhancement of Piezoelectric Performance by Heavy Halogen Substitution in Hybrid Perovskite Ferroelectrics

Abstract

Piezoelectric materials that enable electromechanical conversion have great application value in actuators, transducers, sensors, and energy harvesters. Large piezoelectric (<i>d</i>₃₃) and piezoelectric voltage (<i>g</i>₃₃) coefficients are highly desired and critical to their practical applications. However, obtaining a material with simultaneously large <i>d</i>₃₃ and <i>g</i>₃₃ has long been a huge challenge. Here, we reported a hybrid perovskite ferroelectric [Me₃NCH₂Cl]CdBrCl₂ to mitigate and roughly address this issue by heavy halogen substitution. The introduction of a large-size halide element softens the metal-halide bonds and reduces the polarization switching barrier, resulting in excellent piezoelectric response with a large <i>d</i>₃₃ (∼440 pC/N), which realizes a significant optimization compared with that of previously reported [Me₃NCH₂Cl]CdCl₃ (You et al. <i>Science</i><b>2017</b>, <i>357</i>, 306-309). More strikingly, [Me₃NCH₂Cl]CdBrCl₂ simultaneously shows a giant <i>g</i>₃₃ of 6215 × 10^-3 V m/N, far exceeding those of polymers and conventional piezoelectric ceramics. Combined with simple solution preparation, easy processing of thin films, and a high Curie temperature of 373 K, these attributes make [Me₃NCH₂Cl]CdBrCl₂ promising for high-performance piezoelectric sensors in flexible, wearable, and biomechanical devices.