BaZrS<sub>3</sub> Chalcogenide Perovskite Thin Films by H<sub>2</sub>S Sulfurization of Oxide Precursors
J.A. Marquez, Marin Rusu, Hannes Hempel, Ibbi Y. Ahmet, Moritz Kölbach, Ibrahim Simsek, Léo Choubrac, Galina Gurieva, René Gunder, Susan Schorr, Thomas Unold
Abstract
The earth-abundant ternary compound BaZrS3, 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 BaZrS3 thin films. BaZrO3 precursor layers were deposited by pulsed laser deposition and sulfurized at various temperatures in an argon-diluted H2S atmosphere. We observe increasing incorporation of sulfur for higher annealing temperatures, accompanied by a red shift of the absorption edge, with a bandgap of Eg = 1.99 eV and a large absorption strength >105 cm–1 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 BaZrO3 and BaZrS3 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 cm2 V–1 s–1.