A Schiff-Base Molecular Crystal with Large Effective Transverse Piezoelectric Coefficient and Low Dielectric Loss

Piezoelectric materials play irreplaceable roles in advanced fields including energy conversion, sensing, and actuation. Recently, molecule-based piezoelectrics have become a research hotspot due to their structural diversity, lightweight nature, and mechanical flexibility. Although significant progress has been made in the longitudinal piezoelectric coefficient of molecular piezoelectrics, their transverse piezoelectric coefficient, which offers unique functionalities, remains less explored. Herein, we report a Schiff-base molecular crystal, 2,2'-[(1S,2S)-cyclohexane-1,2-diylbis(azanylylidenemethanylylidene)]bis(4-bromophenol)((S,S)-BCYD), exhibiting a superior effective transverse piezoelectric coefficient of 41 pC/N after oriented cutting, surpassing the majority of organic piezoelectrics. The energy harvester based on it could generate a robust voltage output of 5 V. Moreover, it surprisingly exhibits an ultralow dielectric constant and loss of 2.537 and 0.0012 at 1 GHz, which are much smaller compared to other molecular piezoelectrics. This work highlights the excellent piezoelectric and dielectric performances in a Schiff-base organic crystal, which provides a multifunctional material platform for flexible electronic devices and high-frequency communication technologies.