Large piezoelectric response in a Jahn-Teller distorted molecular metal halide

• Published in: Nature communications 2023-04, Vol.14 (1), p.1852-1852, Article 1852
• Main Authors: Wang, Sasa, Khan, Asif Abdullah, Teale, Sam, Xu, Jian, Parmar, Darshan H., Zhao, Ruyan, Grater, Luke, Serles, Peter, Zou, Yu, Filleter, Tobin, Seferos, Dwight S., Ban, Dayan, Sargent, Edward H.
• Format: Article
• Language: English
• Subjects: 147/135; 639/166/988; 639/301/1023/303; 639/301/930/1032; 639/4077/4072/4062; Coefficients; Dielectric constant; Distortion; Energy; Energy harvesting; Fluorides; Halides; Humanities and Social Sciences; Jahn-Teller effect; Mechanical analysis; Metal halides; Molecular structure; multidisciplinary; Permittivity; Piezoelectricity; Polarization; Polyvinylidene fluorides; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-37471-3

Piezoelectric materials convert between mechanical and electrical energy and are a basis for self-powered electronics. Current piezoelectrics exhibit either large charge ( d 33 ) or voltage ( g 33 ) coefficients but not both simultaneously, and yet the maximum energy density for energy harvesting is determined by the transduction coefficient: d 33 * g 33 . In prior piezoelectrics, an increase in polarization usually accompanies a dramatic rise in the dielectric constant, resulting in trade off between d 33 and g 33 . This recognition led us to a design concept: increase polarization through Jahn-Teller lattice distortion and reduce the dielectric constant using a highly confined 0D molecular architecture. With this in mind, we sought to insert a quasi-spherical cation into a Jahn-Teller distorted lattice, increasing the mechanical response for a large piezoelectric coefficient. We implemented this concept by developing EDABCO-CuCl 4 (EDABCO = N-ethyl-1,4-diazoniabicyclo[2.2.2]octonium), a molecular piezoelectric with a d 33 of 165 pm/V and g 33 of ~2110 × 10 −3  V m N −1 , one that achieved thusly a combined transduction coefficient of 348 × 10 −12  m 3  J −1 . This enables piezoelectric energy harvesting in EDABCO-CuCl 4 @PVDF (polyvinylidene fluoride) composite film with a peak power density of 43 µW/cm 2 (at 50 kPa), the highest value reported for mechanical energy harvesters based on heavy-metal-free molecular piezoelectric. Here, the authors utilise a combination of quasi-spherical theory and Jahn-Teller distortion to enhance the piezoelectric response of molecular metal halides, and the resulting piezoelectric energy harvesters exhibit superior power densities to the best-reported molecular hybrid energy harvesters.