Metal-Free Enantiomeric Organic Crystals for Piezoelectric Energy Harvesting

The power source material applied in wearable electronic devices should be soft, flexible, stretchable, and biocompatible. Organic piezoelectric materials, with their unique combination of these properties, show great promise as innovative energy-harvesting materials. Herein, we present an enantiomeric organic piezoelectric material, <i>R</i>/<i>S</i>-MP-TFSA (MP = 2-Methylpiperazine, TFSA = Trifluoromethanesulfonimide), which crystallizes at room temperature in the polar space group <i>P</i>1 and exhibits a pronounced second-harmonic generation (SHG) response. With a piezoelectric coefficient (<i>d</i>₃₃) of 20 pC/N, the <i>R</i>/<i>S</i>-MP-TFSA- based piezoelectric device demonstrates a stable piezoelectric output voltage of approximately 16 V under simple finger-tapping conditions, a representative example of human mechanical motion. These characteristics highlight its considerable potential for applications in piezoelectric sensors for energy harvesting and self-powered low-voltage electronic devices.