Investigations of thermoelectric properties of ZnO monolayers from the first-principles approach

Abstract

In recent years, the two-dimensional ZnO has been emerged as promising material for thermoelectric applications due to its low-cost and non-toxic behavior. In this article, we report the thermoelectric response of two monolayers of ZnO derived from polar (0001) surface and non-polar (11 2 ‾ 0) surface in the framework of combined density functional theory and Boltzmann transport theory. The thermoelectric parameters of the designed monolayers have been obtained against the chemical potential and temperature. The thermoelectric power factor (PF) is enhanced by p -type doping in case of single-layered ZnO(11 2 ‾ 0) and by n -type doping in the case of ZnO(0001). Accordingly, the maximum PF (PF max ) of ZnO(11 2 ‾ 0) has been recorded as 4.87 × 10 10 W/mK 2 s for p -type doping, whereas the PF max of ZnO(0001) monolayer amount to 3.42 × 10 10 W/mK 2 s for n -type doping. The PF max of ZnO(11 2 ‾ 0) was found to further increase linearly with an increase in temperature, whereas the PF max of ZnO(0001) increased with an increase in temperature up to 600 K, and decreased with an increase in temperature beyond 600 K. The room temperature thermoelectric figure-of-merit have been recorded as large as zT~0.98 for ZnO(11 2 ‾ 0) monolayer and zT ~1.49 for ZnO(0001) monolayer. These predictions reveal the promise of the devised ZnO monolayers of converting waste heat into electric energy via thermoelectric approach. • Thermoelectric response of the novel ZnO monolayers. • Thermoelectric figure of merit(zT) as large as ~1.49 at room temperature. • Potential resources for clean and sustainable energy. • Promising replacement for expensive and toxic thermoelectric materials.