# Thermodynamics of Sulfur Vacancy Formation in the Chalcogenide Perovskite BaZrS3

## TL;DR

This paper studies how sulfur vapor can help make a promising solar material, BaZrS3, at lower temperatures with fewer defects.

## Contribution

The study introduces a thermodynamic analysis showing sulfur vapor's role in low-temperature synthesis of BaZrS3.

## Key findings

- Sulfur vapor precursors offer a thermodynamic driving force 10–102 times stronger than solid-state methods.
- Gaseous S2 is optimal for low-temperature synthesis of high-quality BaZrS3 with fewer defects.
- Sulfur vacancy formation trends depend on sulfur evaporation, not specific synthesis reactions.

## Abstract

Chalcogenide perovskites such as BaZrS3 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 S2 and S8, in driving the synthesis. Our findings reveal
that sulfur vapor precursors can provide a thermodynamic driving force
10–102 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 BaZrS3. In particular, for low-temperature synthesis
below 600 °C, gaseous S2 emerges as the optimal precursor
to produce high-quality BaZrS3 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.