Defect Suppression Strategy Targeting Oxygen‐Related States in Sb ₂ (S,Se) ₃ Thin‐Film Solar Cells

Antimony chalcogenide Sb₂(S,Se)₃ has emerged as a promising light-harvesting material for eco-friendly thin-film photovoltaics due to its earth-abundant composition and suitable optoelectronic properties. However, its device performance remains highly sensitive to the defect landscape and crystalline quality of the absorber layer. In this study, we reveal that the post-annealing environment plays a decisive role in governing oxygen-related states formation and the resulting structural evolution of Sb₂(S,Se)₃ films. Annealing in nitrogen effectively suppresses oxidation pathways, enabling the growth of dense, well-oriented crystallites with reduced defect densities, whereas low-vacuum conditions promote partial oxidation and void generation that hinder charge transport. The best device incorporating nitrogen-treated absorbers exhibits markedly enhanced carrier collection and lowered interfacial recombination, achieving a power conversion efficiency of 8.84%. These findings clarify the crystallization mechanism in Sb₂(S,Se)₃ and establish a viable route toward high-quality absorber layers for next-generation sustainable photovoltaic technologies.