Near‐Surface Reconstruction of Sb 2 Se 3 Absorber for Defect‐Tolerant Solar Cells with Modified Surface Energetics

ABSTRACT Deep‐level defects in the bulk and near‐surface regions of Sb 2 Se 3 absorbers constitute important non‐radiative recombination pathways that limit photovoltaic performance. Here, we develop a near‐surface reconstruction strategy based on a mild solution‐processed sulfur treatment to regulate defect states and surface energetics of Sb 2 Se 3 . Controlled sulfurization of the Sb 2 Se 3 film facilitates the formation of S─Sb bonds in the near‐surface region, suppresses non‐radiative recombination, shifts the surface Fermi level upward, and enhances the built‐in electric field for charge separation. Meanwhile, limited sulfur diffusion into the shallow bulk substantially reduces deep‐trap densities and gives rise to slower photoexcited‐carrier relaxation/recombination dynamics. Furthermore, the spatially confined sulfur distribution largely preserves the bulk crystal structure, optical bandgap, and broad spectral response of the Sb 2 Se 3 absorber. Benefiting from the concurrent regulation of defect states and surface energetics, the optimized device achieves a power conversion efficiency of 10.89%, representing highly competitive performance among Sb 2 Se 3 solar cells.