Enhanced Thermoelectric Performance of ZnO-Based Thin Films via Interface Engineering

Abstract

Zinc oxide (ZnO) is a potential thermoelectric material with good chemical and thermal stability as well as an excellent Seebeck coefficient. However, the extremely low carrier concentration brings poor electrical transport properties. Although Gallium (Ga) doping could increase the carrier concentration of ZnO film, its thermoelectric performance is still limited due to the deteriorated Seebeck coefficient and enhanced thermal conductivity. Interface engineering is an effective strategy to decouple electron-phonon interaction for thermoelectric materials. Thus, in this work, GZO (Ga-doped ZnO)/NAZO (Ni, Al co-doped ZnO) multilayer films were designed to further improve the thermoelectric properties of GZO films. It was found that GZO/NAZO multilayer films possessed better electrical conductivity, which was attributed to the increased carrier concentration and Hall mobility. Meanwhile, benefiting from the energy filtering that occurred at GZO/NAZO interfaces, the density of states effective mass increased, resulting in comparable Seebeck coefficient values. Ultimately, an enhanced power factor value of 313 μW m−1 K−2 was achieved in the GZO/NAZO multilayer film, which is almost 46% larger than that of GZO film. This work provides a paradigm to optimize the thermoelectric performance of oxide films and other thermoelectric systems by multilayer structure design with coherent interfaces.