Understanding the phase stability of BaZrS 3 using ab-initio thermodynamics Prakriti Kayastha, Giulia Longo and Lucy D. Whalley Northumbria University, UK Chalcogenide perovskites are a non-toxic, lead-free alternative to halide perovskites for photovoltaics applications. BaZrS 3 is particularly promising as it is chemically stable and earth abundant with an ideal band gap for applications in a tandem solar cell architecture 1,2 . Synthesis routes at the low to moderate temperatures required for successful device fabrication are under-developed, and there is no systematic study of the phase stability against all competing phases in the Ba-Zr-S system. Understanding the stability of these new materials can provide insight into the reaction pathways that are feasible under certain processing conditions. Although there is some first-principles data available through materials databases, this is not sufficient for predictions of thermodynamic stability across a range of temperatures and synthesis conditions. We will present state-of-the-art DFT and lattice dynamics data for predicting the Gibbs free energy of BaZrS 3 and its competing ternary and binary phases, as a function of temperature and sulphur partial pressure. We will use this to locate the conditions under which there is a thermodynamic driving force towards perovskite formation, in particular highlighting the important role that sulphur partial pressure plays in phase formation. We will also introduce the ThermoPot package used to analyze our first-principles data 3 , which can be applied by other researchers to their systems of interest. References
1. Tiwari et al , J Phys. Energy (2021) 3 034010 2. Sophia et al , Adv. Opt. Mater. (2021) 10 2101704 3. https://github.com/NU-CEM/ThermoPot/
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© The Author(s), 2022
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