BaZrS Chalcogenide Perovskite Thin Films by HS Sulfurization of Oxide Precursors

The earth-abundant ternary compound BaZrS, which crystallizes in the perovskite-type structure, has come into view as a promising candidate for photovoltaic applications. We present the synthesis and characterization of polycrystalline perovskite-type BaZrS thin films. BaZrO precursor layers were deposited by pulsed laser deposition and sulfurized at various temperatures in an argon-diluted HS atmosphere. We observe increasing incorporation of sulfur for higher annealing temperatures, accompanied by a red shift of the absorption edge, with a bandgap of = 1.99 eV and a large absorption strength >10 cm obtained for sulfurization temperatures of 1000 °C. X-ray diffraction analysis and SEM indicate enhanced crystallization at the higher annealing temperatures, but no evidence for a crystalline solid solution between the BaZrO and BaZrS phases is found. The charge carrier sum mobility estimated from optical-pump-terahertz-probe spectroscopy indicates increasing mobilities with increasing sulfurization temperature, reaching maximum values of up to ∼2 cm V s.