Broadband Piezoelectric Harvester Utilizing Three-wafer Bonding for Self-powered Wireless Sensor System

The development prospect of the piezoelectric harvesters mostly subject to its operation bandwidth. This paper reports a piezoelectric energy harvester with the material of the AlN with a broadband of 37 Hz (743 Hz-780 Hz) through the simple method of mechanical limiter. The broadband harvester was packaged by a novel method of wafer-level vacuum packaging which employs two times of eutectic Al-Ge bonding to bond the layers of device wafer, the top wafer and the bottom wafer. And the peak-peak open-circuit output voltage is about 10 V, and an output density is 342.87 mu W/cm(2) with the size of 0.6x1 cm(2). Furthermore, the reported energy harvester is hopeful applied in powering wireless sensor nodes with a wideband vibration frequencies.