| Due to its wide direct band gap of 3.37 eV, large exciton binding energy of 60 meV, ZnO has been demonstrated to have broad applications in electronic, optoelectronic, electrochemical, and electromechanical devices. Among these, utilizing the semiconductor and piezoelectric properties possessed by ZnO nanorods, many kinds of piezoelectric devices have been developed. Since the initial study in 2006 by Z. L. Wang’s group, piezoelectric nanogenerator based on the ZnO nanostructures’piezoelectric effect has been an active research field. A series of ZnO based nanogenerators on different substrates such as sapphire, ITO and fibers were raised. Various approaches have been developed for converting different kind of mechanical energy into electric energy with ZnO based nanogenerators, such as ultrasonic waves, body movement, and irregular air flow.In this paper, based on the growth of ZnO nanorods by low-temperature hydrothermal method, two types of flexible nanogenerators were presented. The main work and result are as follows.We synthesized a heterostructure comprised of ZnO nanorods and flower-like CuO nanostructures on an indium tin oxide (ITO) coated flexible substrate (polyethylene terephthalate, PET) by a two-step hydrothermal method. SEM, XRD and EDS were used to characterize the heterostucture’s morphologies and structure. The results show that ZnO nanorods have hexagonal geometry and densely distributed on the substrate, the CuO nanostructures have a flower-like shape with high purity.Moreover, a flexible nanogenerator based on the p-CuO/n-ZnO heterostructure was fabricated for harvesting energy from environment. Electrical property of the nanogenerator was measured using a Keithley 4200 semiconductor characterization system. The nanogenerator has well-defined rectifying behavior and demonstrates an enhancement output performance because the piezoelectric potential screening by excessive electrons was successfully suppressed. A larger output current of～100nA was obtained in comparison with ZnO based nanogenerator. The study can stimulate a research trend on designing a new material system for high-performance piezoelectric nanogenerator.We also present a simple, lowcost approach to fabricate a flexible NG based on Cu2O-ZnO p-n junction on Cu wire. Wrapped by external Au-coated paper electrode, the NG can convert mechanical energy into electricity under external force. The output voltage and current generated from the generator can reach up to 42 mV and 400 nA respectively. The enhance performance is mainly due to the existence of Cu2O-ZnO p-n junction reducing the screening effects of the residual free electrons and the flexible outer electrode making more nanorods involved in the power generation process. It is indicated that this kind of nanogenerator has potential application for harvesting energy from environment to power nanodevices. |
