Enhancement of ZnO-based flexible nano generators via a sol-gel technique for sensing and energy harvesting applications.

Zinc oxide (ZnO) is a remarkable inorganic semiconductor with exceptional piezoelectric properties compared to other semiconductors. However, in comparison to lead-based hazardous piezoelectric materials, its properties have undesired limitations. Here we report a 5∼6 fold enhancement in piezoelectric features via chemical doping of copper matched to intrinsic ZnO. A flexible piezoelectric nanogenerator (F-PENG) device was fabricated using an unpretentious solution process of spin coating, with other advantages such as robustness, low-weight, improved adhesion, and low cost. The device was used to demonstrate energy harvesting from a standard weight as low as 4 gm and can work as a self-powered mass sensor in a broad range of 4 to 100 gm. The device exhibited a novel energy harvesting technique from a wind source due to its inherent flexibility. At three different velocities (10∼30 m s) and five different angles of attack (0∼180 degrees), the device validated the ability to discern different velocities and directions of flow. The device will be useful for mapping the flow of air apart from harvesting the energy. The simulation was done to verify the underlining mechanism of aerodynamics involved.