Enhanced piezoelectricity of composite piezoelectric nanogenerators by varying the aspect ratio of zinc oxide nanoparticles

The relationship between the ZnO aspect ratio (AR) and the piezoelectric performance of the composite piezoelectric nanogenerators (PNGs) has not been clearly identified, especially theoretically. Herein, we developed a multiphysics simulation considering the mechanical and electrical coupling mechanism to identify the theoretical mechanism for the relationship. In addition, a strategy to control the ZnO AR according to the synthesis conditions was adopted to minimize changes in the chemical composition that could affect the consistency of the experimental results when compared to theoretical results. The ZnO AR increased from 3.3 to 26.3 as the growth temperature increased from 65 to 95 °C at the optimum growth time of 60 min. The piezoelectric current/voltage of the composite PNGs was improved by 1367/232 and 650/516 % by repetitive mechanical force and hammer stamping, respectively, according to the increased AR of randomly dispersed ZnO. From the developed simulation, which can successfully describe these experimental results, it was demonstrated that the increased AR was advantageous for large deformation of ZnO, continuous stress transfer and piezoelectric potential generation in the composite PNG.