In this letter, we present the fabrication and characterization of a zinc oxide (ZnO)-based nanogenerator for piezoelectric micro-energy harvesting by combining thin films of amorphous silicon (a-Si) and ZnO. We utilized the a-Si thin film as an interlayer to assemble several a-Si/ZnO-stacked piezoelectric nanogenerators (SZPNGs) on indium tin oxide (ITO)-coated polyethylene naphthalate substrates. We investigated the influence of the a-Si layer thickness on the output voltages of the SZPNGs and demonstrated the existence of an optimal a-Si thickness for maximizing the output voltage. Overall, the SZPNGs generated higher output voltages than a conventional ZnO-based piezoelectric nanogenerator (ZPNG) lacking an a-Si interlayer, indicating enhanced performance. In particular, the SZPNG based on the optimal a-Si thickness exhibited a sixfold higher output voltage compared with the conventional ZPNG. This improved performance was ascribed to a combination of the Schottky barrier at the ITO/a-Si interface, preventing the screening effect and the relatively high dielectric constant (εr≈13) of a-Si, minimizing the loss of the piezoelectric potential induced in the ZnO layer. The results herein are expected to assist the development of even more advanced ZnO-based piezoelectric nanogenerators in the future.

Here, we present a study of thermoelectric devices with amorphous silicon/zinc oxide (a-Si/ZnO)-stacked hetero-structures fabricated using both radio frequency magnetron sputtering and rapid thermal annealing techniques. Overall, the Seebeck coefficient (S) and power factor (S2σ, where σ is the electrical conductivity) of the a-Si/ZnO-stacked hetero-structures were found to be superior to those of pure a-Si structures. In particular, the Seebeck coefficient and power factor of the a-Si/ZnO (9/8 layers)-stacked hetero-structures were about 1.6 and 23.8 times those of the pure a-Si structures, respectively. These improvements can be attributed to hole blocking by the a-Si/ZnO potential barriers formed at the interface between the ZnO layer with a wide energy bandgap and the a-Si layer with a relatively narrow bandgap. In addition, the a-Si and ZnO materials used in this work are non-toxic, earth-abundant, and cheap, and the fabrication processes were simple and cost-effective, making the hetero-structures suitable for use in non-toxic and biocompatible thermoelectric devices and also for micro-energy harvesting applications.