Breaking Barriers in Chalcogenide Perovskite Synthesis: A Generalized Framework for Fabrication of BaMS3 (M═Ti, Zr, Hf) Materials

Abstract

Chalcogenide perovskites have garnered increasing attention as stable, non-toxic alternatives to lead halide perovskites. However, their conventional synthesis at high temperatures (>1000 °C) has hindered widespread adoption. Recent studies have developed low-to-moderate temperature synthesis methods (<600 °C) using reactive precursors, yet a comprehensive understanding of the pivotal factors affecting reproducibility and repeatability remains elusive. This study delineates the critical factors in the low-temperature synthesis of BaMS₃ (M═Zr, Hf, Ti) compounds and presents a generalized framework. Innovative approaches are developed for synthesizing BaMS₃ compounds using this framework involving organometallics for solution deposition. The molecular precursor routes, employing metal acetylacetonates to generate soluble metal–sulfur bonded complexes and metal–organic compounds to produce soluble metal-thiolate, metal-isothiocyanate, and metal-trithiocarbonate species, are demonstrated to yield carbon-free BaMS₃. These methods have achieved the most contiguous films of BaZrS₃ and BaHfS₃ using solution deposition to date. Furthermore, a hybrid solution processing method involving stacking sputter-deposited Zr and solution-deposited BaS layers is employed to synthesize a contiguous, oxygen-free BaZrS₃ film. The diffuse reflectance measurements indicate a direct bandgap of ≈ 1.85 eV for the BaZrS₃ films and ≈ 2.1 eV for the BaHfS₃ film under investigation.