Growth of BaZrS3 Chalcogenide Perovskite Thin Films Without Post Annealing

Tandem solar cells based on hybrid organic–inorganic metal halide perovskites have achieved power conversion efficiencies of up to 28%. However, issues related to long-term stability and lead (Pb) toxicity have prompted the search for earth-abundant, chemically stable, and non-toxic alternatives. In this work, we report the first vacuum evaporation synthesis of BaZrS₃ (barium zirconium sulfide) thin films at a substrate temperature of 550 °C. The resulting films exhibit near-stoichiometric Ba:Zr ratios and strong light absorption, with absorption coefficients exceeding 10⁵ cm⁻¹ near 1.9 eV. Under controlled conditions, a baseline oxygen content of 4–6% was consistently observed. The absence of an additional sulfurization step markedly increased the resistance of the thin film and suppressed the dark current by approximately three orders of magnitude, indicating a substantial reduction in carrier density likely resulting from a decreased concentration of sulfur vacancies. These findings highlight the potential of BaZrS3 as a stable, lead-free absorber for next-generation photovoltaics.