First-principles investigations of ZnO monolayers derived from zinc-blende and 5-5 phases for advanced thermoelectric applications

Two-dimensional (2D) materials have received substantial interest in recycling waste heat via the thermoelectric approach in recent years. In this article, we investigate the thermoelectric response of two novel 2D polymorphs of ZnO derived from the zinc-blende phase (ZnO(zb)) and 5-5 phase (ZnO(5-5)) for advance thermoelectric applications by first-principles. The thermoelectric behavior of these 2D polymorphs of ZnO has been evaluated from calculations of the thermoelectric power factor (PF) and figure-of-merit (zT) values. The p-type of doping results in the enhancement of PF for both monolayers of ZnO. The highest values of PF have been accordingly determined as 15.70 x 10(10) W/mK(2)s at -2.40 eV for single-layered ZnO(zb) and 25.08 x 10(10) W/mK(2) s at -1.81 eV for ZnO(5-5) monolayer. The recorded PF of single-layered ZnO(zb) has been found to decline slightly whereas a drastic increase in the PF of ZnO(5-5) monolayer has been recorded with an increase in temperature. Like PF, the zT values of these monolayers have been found larger for p-type doping of magnitude 0.583 and 0.977 respectively for ZnO(zb) and ZnO(5-5) monolayers. The predictions suggest the ZnO monolayers (ZnO(5-5) in particular) as promising candidates for advanced thermoelectric applications.

Automated summary

This study investigates the thermoelectric response of two novel 2D polymorphs of ZnO under first-principles calculations, revealing that p-type doping significantly enhances the thermoelectric power factor (PF) and shows great potential, especially in the case of the ZnO(5-5) monolayer.