Enhanced output performance of piezoelectric energy harvester based on hierarchical Bi3.15Nd0.85Ti3O12 microspheres/PVDF-HFP composite

Abstract

The inclusion of inorganic piezoelectric fillers in the polymeric matrix of flexible ferroelectric polymer synergies the piezoelectricity for wearable electronics. Herein, hierarchical Bi3.15Nd0.85Ti3O12 microspheres (H-BNdT MPs) embedded in the polymeric matrix of polyvinylidene fluoride–hexafluoropropylene (PVDF-HFP) based piezoelectric thin films are fabricated by using a facile and cost-effective film-forming method, drop-casting. The composites possess improved dielectric and ferroelectric properties comparing with that of the pure PVDF-HFP film without any electrical poling treatment. More importantly, the highest outputs of an open-circuit voltage of 20 V and a short-circuit current of 1.9 μA under the repeated mechanical force of 10 N at the frequency of 2 Hz were successfully achieved. The maximum power of the optimal PEH can reach as high as 4.6 mW, corresponding to a power density of 938 μW/cm2, and the output electricity can light up 10 LEDs with a full-wave rectifier circuit. The enhanced output performance is attributed to the high local stress around the H-BNdT MPs arising from the hollow hierarchical architecture of the inorganic fillers. The lead-free flexible PEH is also proved to have the ability to harvest the biomechanical energy of human movements, such as finger pinching, finger tapping, and fist punching. In particular, a PEH shoe is made to harvest energy from walking and running. This PEH is confirmed to be a potential energy harvester and effective self-powered generator to drive wearable devices.