The thermoelectric characteristics of aligned ZnO/PVP composite nanofibers (NFs) prepared by electrospinning and subsequent thermal annealing were examined by the comparison between their mesoscale structure and the Seebeck coefficient. Rapid thermal annealing of NFs produces mesoscale grains and a Seebeck coefficient of -313.7 mu V/K. In contrast, the NFs annealed in a conventional furnace have a straight-line shape without any discernible grains, and their Seebeck coefficient is largely four times smaller (-82.1 mu V/K). The difference in the structural morphology of the NFs results in their difference in Seebeck coefficients. The mesoscale grains of the NFs annealed by rapid thermal annealing are efficient in reducing thermal conductivity and contribute to an enhancement of the thermoelectric properties. (C) 2014 Elsevier B.V. All rights reserved.