Over 10% Efficient Sb ₂ (S,Se) ₃ Solar Cells Enabled by CsI‐Doping Strategy

Abstract Antimony selenosulfide (Sb ₂ (S,Se) ₃ ) is an emerging quasi‐1D photovoltaic semiconductor with exceptional photoelectric properties. The low‐symmetry chain structure contains complex defects and makes it difficult to improve electrical properties via doping method. This article reports a doping strategy to enhance the efficiency of Sb ₂ (S,Se) ₃ solar cells by using alkali halide (CsI) as the hydrothermal reaction precursor. It is found that the Cs and I ions are effectively doped and atomically coordinate with Sb ions and S/Se ions. The CsI‐doping Sb ₂ (S,Se) ₃ absorbers exhibit enhanced grain morphologies and reduced trap densities. The consequential CsI‐doping Sb ₂ (S,Se) ₃ based solar cells demonstrate favorable band alignment, suppressed carrier recombination, and improved device performance. An efficiency as high as 10.05% under standard AM1.5 illumination irradiance is achieved. This precursor‐based alkali halide doping strategy provides a useful guidance for high‐efficiency antimony selenosulfide solar cells.