Mechanically flexible piezoelectric organic single crystals for electrical energy harvesting

Piezoelectric crystalline materials—a class of ordered materials that can derive electric current due to charge accumulation via electromechanical coupling—have gained tremendous interest owing to their use as highly portable energy sources; however, the exceptional mechanical bendability coupled with high crystallinity offered by molecular single crystals is yet to be explored. Here, we present the discovery of a mechanically flexible (bendable) all-organic single-crystalline material exhibiting a remarkable piezoelectric energy-harvesting property. These soft piezoelectric crystals, with helical structure and the presence of predominantly weak noncovalent interactions therein, allowed us to fabricate flexible, electrical energy-harvesting devices using a polymer matrix, which yielded instantaneous peak power density of ∼66 μW/cm3 with an excellent energy conversion efficiency of ∼41%. The real-life application potential of the devices is validated by successfully powering LEDs and showcasing sensitivity to biomechanical activity. This research lays the foundation for designing flexible and environmentally friendly electronics using mechanically flexible organic single crystals.