Effect of Ni and Mn dopant on thermoelectric power generation performance of ZnO nanostructures synthesized via hydrothermal method

In this article, we have presented a low-cost hydrothermal approach to enhance the thermoelectric performance of ZnO nanostructures via modulation doping. For this purpose, we have prepared a series of pure and X:ZnO (X = Ni & Mn) samples. The Seebeck value of the Mn-doped samples possesses the maximum Seebeck coefficient of −36 μV/°C compared to the pure and Ni-doped samples (−22 μV/°C & −27 μV/°C) at room temperature. The highest value of the Seebeck coefficient for the Mn-doped samples is related to the formation of mid-gap energy band states due to the substitution of Mn2+ with Zn2+. These mid-band states induce an imbalance in the DOS, by producing a spin polarization effect that leads to a high Seebeck value. In terms of electrical conductivity, the Ni-doped ZnO sample exhibits the highest electrical conductivity of about 122 S/cm, due to the incorporation of Ni metal ions inside the ZnO matrix (confirmed by XRD) and leads to a high carrier concentration. However, the highest Seebeck value for the Mn-doped sample results in the maximum thermoelectric power factor ∼1.12 × 10−5 Wm−1C−2 at room temperature. •Synthesis of pure and doped ZnO nanostructures by hydrothermal method.•Phase purity of the ZnO nanostructures was confirmed by XRD and Raman.•Influence of Ni and Mn doping was studied over the thermoelectric transport parameters.•Highest thermoelectric power factor (1.12 × 10−5 Wm−1C−2) was observed for Mn doped sample.