Low-Power Piezoelectric Energy From Chiral Supramolecular Polymer of a Donor-Acceptor-Donor Conjugated π-System

Soft piezoelectric systems have high demands in flexible, shape conformable and biocompatible low-power electronics. This paper explores chiral supramolecular polymerization of an ambipolar donor-acceptor-donor (DAD)-type π-system showing emerging piezoelectric properties for harvesting micro energies. The DAD molecule is designed with two conjugated thiophene donors with a central naphthalene-diimide (NDI) acceptor chromophore to facilitate intra-molecular charge-transfer, evident from a prominent absorption band in the visible region. This chromophore is further appended with two chiral benzamide-wedges for homochiral supramolecular polymerization. The ambipolar character of the chiral DAD chromophore is manifest from the cyclic voltammogram. Extended H-bonding among the amide groups leads to homochiral supramolecular polymerization in methyl-cyclohexane, which is retained in the solid film. The impeccable piezoelectricity in poled DAD film revealed a d₃₃ ∼ 7 pm/V as measured by the piezoforce microscopy. Poled piezo DAD devices under optimized periodic external impact force, frequencies and supplied electric field generate a viable output voltage and current density of 1.3 V, 0.8 µA/cm², and P_output ∼ 1.6 µW/cm², respectively. As a proof-of-concept demonstration, stacked and poled supramolecular π-conjugated DAD devices are shown to viably illuminate a light emitting diode through charging a series of micro capacitors, indicating the potential utility for low power technologies.