Predicting properties of Zn_1+xSn_1-xN_2-2xO_2x: defects and disorders

ZnSnN₂ (ZTN) is a promising absorber material for photovoltaic (PV) applications. However, in practice, the growth of ZTN thin film incorporates non-trivial amount of oxygen. The excess amount of oxygen can lead to cation off-stoichiometry, such as Zn excess (Zn_1+xSn_1-xN_2-2xO_2x), and disorders in the material. As a result, it becomes essential to investigate the effects of these complications to materials properties, such as optoelectronic properties, and their implications for PV devices. In this contribution, we will present our computational studies of defects and disorders in Zn_1+xSn_1-xN_2-2xO_2x (ZTNO), and their relations to materials properties, such as defect phase diagram, net doping, band gap, carrier localization, and absorption coefficients. The disordered ZTNO structures were created by motif-based Monte Carlo (MC) simulations. The MC generated structures were then passed to density functional theory (DFT) based calculations for the study of oxygen content induced changes in the electronic structures. The defect phase diagram was calculated through a DFT based thermodynamic simulation with a consideration of oxygen-induced band edge shifts.