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 mu V/degrees C compared to the pure and Ni-doped samples (- 22 mu V/degrees C & -27 mu V/degrees 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 similar to 1.12 x 10(-5) Wm(- 1)C(-2) at room temperature.

Automated summary

In this article, a low-cost hydrothermal approach is used to enhance the thermoelectric performance of ZnO nanostructures through modulation doping. Pure and X:ZnO (X = Ni & Mn) samples are prepared, and it is found that Mn-doped samples exhibit the highest Seebeck coefficient (-36 mu V/degrees C) compared to the pure and Ni-doped samples (-22 mu V/degrees C & -27 mu V/degrees C) at room temperature. The highest Seebeck coefficient in the Mn-doped samples is attributed to the creation of mid-gap energy band states by substituting Mn2+ with Zn2+, leading to a spin polarization effect and imbalanced DOS. On the other hand, Ni-doped ZnO samples show the highest electrical conductivity (122 S/cm) due to the incorporation of Ni metal ions, resulting in a high carrier concentration. Despite this, the Mn-doped sample achieves the maximum thermoelectric power factor of 1.12 x 10^(-5) Wm^(-1)C^(-2) at room temperature.