Study on increasing output current of piezoelectric energy harvester by fabrication of multilayer thick film

Piezoelectric energy harvesting generally demonstrates low output power because its output current is low compared to its high output voltage. The low current and high impedance limit the applications of piezoelectric energy harvesting systems. Thus, it is necessary to increase the output current and reduce the internal impedance. This study presents the fabrication of multilayer piezoelectric thick films with high output currents. Single-layer and five-layer piezoelectric devices are prepared using the tape-casting process. The material properties of each lead zirconate titanate (PZT) ceramic are measured using an impedance analyzer and a d33 meter. The electrical properties of the piezoelectric devices were evaluated by a controllable strain module using vibration exciter. The capacitance of the single-layer device was 7.33 nF and that of the five-layer device was 241.04 nF, which was 32.88 times higher than that of the single-layer device. The open circuit voltage of the five-layer device decreased 6.09 times compared to the single-layer, but the short circuit current increased 5.30 times. The impedance matching load of the five layer device for maximum power transfer was averagely 34.05 times smaller than that of single-layer. Under maximum power transfer conditions, the current of the five-layer PZT device was 6.61 times larger than the single-layer, even though the output power of both devices was similar. Because of this capacitance and current increase, the energy stored in the 220 μF capacitor for 10 s using the five-layer device was 920% larger compared to the energy stored using a single-layer.