Enhanced thermoelectric properties of ZnO: C doping and band gap tuning

Abstract

ZnO is a promising high-temperature thermoelectric material because of its non-toxicity and low-cost. However, the wide band gap and low electrical conductivity lead to inferior thermoelectric properties. Herein, C-doping in ZnO bulk was achieved by the pyrolysis of hydrothermal surfactant TEA through a facile and speedy SPS technique. DFT calculation and experimental results show that C was incorporated into the O-site in ZnO, which reduces band gap and increases carrier concentration, thereby improving electrical conductivity and power factor. Meanwhile, the additional point defects introduced by the substitution of C/O atoms strengthen phonon scattering and decrease thermal conductivity. Benefiting from C-doping via not only tuning the electrical transport properties but also reducing the thermal conductivity, a peak ZT value of 0.024 at 773 K was achieved for Zn(O,C) bulk. It indicates that C-doping in ZnO is an effective and convenient strategy to improve thermoelectric performance.