Enhanced piezoelectric nanogenerator performance with AZO/NiO heterojunction

ZnO nanorods (NRs) are piezoelectric materials used as nanogenerators because of their ease of synthesis, nontoxicity, low production costs, good electrical properties, and suitable flexibility for human movement as a source of mechanical energy. ZnO NRs are usually doped or composited with other materials to enhance their properties. Here we discuss the effect of the aluminum (Al) doping of ZnO using the hydrothermal method and subsequent coating with NiO to form a p–n junction in a nanogenerator application. According to XRD characterization, Al doping caused a shift in the ZnO NRs diffraction peaks toward a larger angle and a decrease in the diameter of the NRs. The doping of Al and NiO composites could also widen the bandgap. Moreover, current and voltage characterization results showed that the nanogenerator output power was 14.8 µW, which reached saturation (19.5 µW) at 4 % doping. Therefore, Al doping can improve the output power of the nanogenerator compared with pure ZnO.