The Influence of Resistance and Carrier Concentration on the Output Voltage of a ZnO Nanogenerator

Different techniques to increase the output voltage of a zinc oxide (ZnO) nanogenerator are investigated. As a first optimization step, the ZnO nanowires were annealed in different gases after growth, and this led to a threefold increase in the output voltage. The effect of the different gases on the ZnO nanowires, and hence on the output voltage, is discussed. Next, the addition of different materials to the polymethylmethacrylate that is spun onto the substrate also showed an increase in the output voltage by a factor of 3. The effect of the different materials on the nanogenerator is discussed and the relationship with the output voltage is shown. Combining the mentioned optimization techniques into one nanogenerator led to a measured output voltage larger than 5 V, with a power output of 0.23$\mu$W/cm$^2$.