Diameter Dependent Ultra-High Thermoelectric Performance of ZnO Nanowires

The zinc oxide (ZnO) shows a great potential in electronics, while the large intrinsic thermal conductivity limits its thermoelectric applications. In this work, we explored the significant carrier transport capacity and diameter dependent thermoelectric characteristics of wurtzite-ZnO<0001> nanowires based on the first principles simulation and molecular dynamics simulation. Under the synergistic effect of band degeneracy and weak phonon-electron scattering, P-type (ZnO)73 nanowires achieve an ultra-high power factor above 1500 μW·cm-1·K-2 in a wide temperature range. The lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size dependence. When the ZnO nanowire diameter exceeds 12.72 Å, the carrier transport properties increase significantly, while the thermal conductivity shows a slight increase with the diameter size, resulting in a ZT value up to 6.4 at 700 K for P-type (ZnO)73. The size effect is also illustrated by introducing two geometrical configuration models of ZnO nanowires for the first time. This work can theoretically depict the strategy of size optimization for thermoelectric conversion of ZnO nanowires.