Abstract
Chalcogenide perovskites such as BaZrS(3) hold potential as promising photovoltaic materials; however, their integration into solar energy devices is currently limited by the high-temperature processing requirements. To explore alternative low-temperature synthesis pathways, we performed an ab initio thermodynamic analysis, highlighting the critical role of sulfur vapor flux, mainly gaseous S(2) and S(8), in driving the synthesis. Our findings reveal that sulfur vapor precursors can provide a thermodynamic driving force 10-10(2) times stronger than that from traditional solid-state methods. Moreover, we find that sulfur gas composition significantly affects the concentration of sulfur vacancy defects in BaZrS(3). In particular, for low-temperature synthesis below 600 °C, gaseous S(2) emerges as the optimal precursor to produce high-quality BaZrS(3) with reduced defect concentrations. The thermodynamic trend of sulfur vacancy formation is governed by the evaporative nature of sulfur and is independent of specific synthesis reactions. This conclusion holds broader implications for generic chalcogenide synthesis where sulfur vacancy management is important.