Characteristics of piezoelectric ZnO/AlN-stacked flexible nanogenerators for energy harvesting applications

Flexible piezoelectric zinc oxide (ZnO)-based nanogenerators (NGs) using an aluminum nitride (AlN) interlayer are proposed for high-efficiency energy harvesting applications. The effects of the AlN interlayer on device performance are studied. Use of the AlN interlayer in ZnO-based vertically integrated NGs (VINGs) results in a significant improvement in terms of the magnitude of the output voltages of up to 200 times when compared with a ZnO-based VING without any AlN interlayer. The improved device energy conversion efficiency is mainly attributed to a high contact potential barrier that the AlN interlayer provides in VINGs, along with the relatively high dielectric constant and large Young's modulus of the AlN material. In addition, the effects of AlN thickness on the electric potential and device performance of the VINGs are investigated through observation of the output voltages of ZnO-based VINGs with thickness/position-controlled AlN interlayers. Our findings in this work are expected to provide effective and useful approaches for realizing highly energy-efficient ZnO-based NGs and their extended applications, including self-power sources and sensor devices. (C) 2015 AIP Publishing LLC.