Improvement of thermoelectric properties of conductive Ag fabrics covered with ZnO nanostructures for wearable thermoelectric applications
摘要
With the aim of realizing a high-efficient flexible thermoelectric (TE) material, we fabricated Ag fabrics (SFs) covered with ZnO nanostructures grown by hydrothermal synthesis and characterized their crystallographic and TE properties. It was observed that ZnO wires grow longer and thicker and their coverage also becomes higher as the NaOH concentration and the growth temperature are increased. Seebeck coefficient was found to be enhanced with increasing the NaOH concentration at 373 K. This was considered to originate from the reduction in the carrier (electron) concentration, confirmed by Hall measurement, because of the improved ZnO crystallinity leading to the reduction of the O vacancy. On the other hand, the electrical conductivity was also increased for the high NaOH concentration. This was confirmed to be due to the enhancement of the electron mobility caused by an increase in the relaxation time of electrons with the crystallinity improvement. As a result, it brought about a higher power factor of 0.23 mWm−1 K−2 at 373 K. These results show the effectiveness of a tunable hydrothermal growth approach in simultaneously optimizing carrier concentration and mobility, offering a facile and scalable strategy for the development of high-performance, flexible ZnO-based thermoelectric materials.