Harvesting and mapping ultrasonic vibration power using semiconducting wire-based tribovoltaic generators

Ultrasonic vibration is an excellent mechanical power source owing to its large power density. Harvesting ul-trasonic vibrations has been demonstrated so far through piezoelectric effect, triboelectric effect, and electro-magnetic induction. However, the majority of these devices only produce AC output which limits their potential applications. This work demonstrates, for the first time, the conversion of ultrasonic vibration power to DC output using semiconducting wire-based electric generators, in which one or several semiconductor wire/metal junction(s) are employed. A current density of up to 19 mu A/cm2 and a peak power density of 5 mu W/cm2 can be obtained under ultrasonic vibrations up to 37 kHz. The mapping of the ultrasonic vibrational strength has been achieved, demonstrating the capability of a self-driven powered ultrasonic sensor. The characteristics of indi-vidual semiconductor junctions and the series connection of several such junctions are studied using equivalent circuits.