Generalizing Synthesis Approaches for BaMS₃ Chalcogenide Perovskites and Related Materials

Over the past decade, lead halide perovskites have witnessed a remarkable surge in solar device efficiencies. They possess a defect-tolerant crystal structure, showcasing outstanding optoelectronic and charge transport properties with tunable bandgaps. However, their progress is hindered by limited air, moisture, and thermal stability. While research on these exceptional materials should continue, there is a need to identify stable alternatives that exhibit similar appealing properties. Chalcogenide Perovskites have emerged as promising substitutes for lead halide perovskites. These materials also display defect tolerance and boast one of the highest light absorption coefficients. They demonstrate considerable stability against air, moisture, and thermal conditions, and their bandgaps can be tailored for either single-junction or tandem solar cell applications.<br/><br/>Nevertheless, Chalcogenide Perovskites face a challenge in high-temperature synthesis. Historically, they have been synthesized at temperatures exceeding 900°C, either as powders or vacuum-deposited thin films. Such high-temperature syntheses restrict the choice of substrates for material deposition. Additionally, not all the intermediary layers in a solar cell can endure such high temperatures. Therefore, it is imperative to synthesize these materials of the highest quality at low to moderate temperatures (&lt;600°C). In recent years, multiple research groups have successfully synthesized nanoparticles or inhomogeneous solution-processed films at low temperatures. However, a comprehensive understanding of the critical parameters enabling this achievement is still lacking.<br/><br/>In this work, we present a comprehensive framework for the synthesis of low-temperature BaMS₃ compounds (M=Zr, Hf, Ti) while discussing the interplay of precursor reactivity, availability of a transport agent, and an oxygen sink as the primary factors governing low-temperature synthesis with limited contamination. Furthermore, to validate our framework, we introduce four novel methods to synthesize BaMS₃ compounds at low temperatures, adhering to the guidelines outlined in the framework. Our results highlight a unique opportunity to synthesize BaMS₃ compounds using cost-effective precursors at low temperatures, offering guidance for future research on these materials.