Superior transverse piezoelectricity in organic-inorganic hybrid perovskite nanorods for mechanical energy harvesting

Developing highly piezoelectric nanoparticles (NPs) with inherent mechanical-electrical coupling effect is critically important for energy harvesters, self-powered sensors and actuators. Over the past decades, the NPs with a high longitudinal piezoelectric coefficient (d33) were developed for piezoelectric nanogenerators (PENGs) that operate under periodic vertical compression mode. As an alternative, high-performance PENGs can be developed by taking advantage of materials with a superior transverse piezoelectric coefficient (d31). In this work, we successfully synthesized an organic-inorganic hybrid perovskite (OIHP) nanorods (NRs) of (4-aminotetrahydropyran)2 PbBr2Cl2 [(ATHP)2PbBr2Cl2] that exhibits a large d31 of 64.2 pC/N, which is 3 times higher than the well-known poly (vinylidene fluoride) (PVDF) polymer (21 pC/N). A saturated polarization of 5.4 mu C/ cm2 and a piezoelectric voltage coefficient (g33) of 900 mV center dot m/N are also reported. The (ATHP)2PbBr2Cl2 NRs can be dispersed homogeneously in a polymer matrix to make piezoelectric composite films. Due to their excellent flexibility, uniform dispersion and large surface area the concurrent vertical strain and lateral bending yield a high piezoelectric performance. We fabricate a unique piezoelectric composite film for PENGs, which can produce an output voltage (Voc) of 90 V and a short-circuit current (Isc) of 6.5 mu A under an applied force of only 4.2 N, outperforming a number of the state-of-the-art PENGs (Table S2). The harvested electrical energy is stored in a capacitor by a two-stage energy transfer mechanism for self-powered electronics. This is the first work, that not only reveals the large transverse piezoelectricity in the (ATHP)2PbBr2Cl2 NRs, but also coins a route to employ it in practical energy harvesting devices.