Enhancement of the output voltage for triboelectric nanogenerators due to Al doping in the zinc oxide layer

Abstract We fabricated triboelectric nanogenerators (TENGs) consisting of an Al electrode, a polyimide dielectric layer, a ZnO dielectric layer, and an indium tin oxide (ITO) electrode, and we observed an enhancement of the output voltage that was due to Al doping in the ZnO layer. The variation in the surface of the Al doped zinc oxide (AZO) layer, which was found to depend on the Al doping concentration, was studied by using scanning electron microscopy. The existence of Al particles was identified from the X-ray photoelectron spectroscopy results. The open-circuit voltage and the short-circuit current of the TENGs with 2% and 5% Al doping in the ZnO layer and operating in the vertical contact-separation mode were larger than those of TENGs having a ZnO layer without Al doping, respectively. The Al doping reduced the asymmetry of negative and positive output voltages and shortened the duration of the positive peaks. The enhancement in the output properties of the TENGs due to the dielectric properties of the Al particles, which was theoretically analyzed in the contact-separation mode operated TENGs with dimensionless formulations, which is compared with the experimental results.