Georgia Tech Research Corporation (Atlanta, GA) garnered U.S. Patent 7,705,523 for hybrid solar-piezoelectric nanogenerator cells. The hybrid nanogenerator consists of dye-sensitized solar cells made of zinc oxide (ZnO) nanowire arrays grown of a flat substrate for harvesting solar energy integrated with a piezoelectric nanogenerator for harvesting ultrasonic wave energy.
According to inventors Zhong L. Wang and Xudong Wang, the two energy harvesting approaches can work simultaneously or individually and can be integrated in parallel or serial for raising the output current, voltage or power, respectively.
The solar cells employ optical fibers and semiconductor nanowires grown around the fibers. A p-n junction based design, organic-inorganic heterojunction, or a dye-sensitized structure is built at the surfaces of the nanowires. Light entering the fiber from a tip propagates through the fiber until it enters a nanowire where it reaches a photovoltaic element. Light entering the fiber cannot escape until it interacts with a photovoltaic element, thereby increasing the solar conversion efficiency. The fiber can transmit light, while the nanowires around the fibers increase the surface area of light exposure.
The piezoelectric nanowire vibrational power generating portion includes an electrical contact structure electrically coupled to and extending downwardly from the first electrode and disposed adjacent to the solar power generating portion. A plurality of piezoelectric semiconductor nanorods extends upwardly from a second electrode that is spaced apart from the first electrode so as to be directed toward the electrical contact structure. The plurality of piezoelectric semiconductor nanorods are configured to release electrons across a Schottky barrier formed between the piezoelectric semiconductor nanorods and the electrical contact structure when mechanical energy is applied to the piezoelectric nanowire vibrational power generating portion.