Low‐Cost Antimony Selenosulfide with Tunable Bandgap for Highly Efficient Solar Cells

About 10% efficient antimony selenosulfide (Sb₂ (S,Se)₃ ) solar cell is realized by using selenourea as a hydrothermal raw material to prepare absorber layers. However, tailoring the bandgap of hydrothermal-based Sb₂ (S,Se)₃ film to the ideal bandgap (1.3-1.4 eV) using the selenourea for optimal efficiency is still a challenge. Moreover, the expensive selenourea dramatically increases the fabricating cost. Here, a straightforward one-step hydrothermal method is developed to prepare high-quality Sb₂ (S,Se)₃ films using a novel precursor sodium selenosulfate as the selenium source. By tuning the Se/(Se+S) ratio in the hydrothermal precursor solution, a series of high-quality Sb₂ (S,Se)₃ films with reduced density of deep defect states and tunable bandgap from 1.31 to 1.71 eV is successfully prepared. Consequently, the best efficiency of 10.05% with a high current density of 26.01 mA cm^-2 is achieved in 1.35 eV Sb₂ (S,Se)₃ solar cells. Compared with the traditional method using selenourea, the production cost for the Sb₂ (S,Se)₃ devices is reduced by over 80%. In addition, the device exhibits outstanding stability, maintaining more than 93% of the initial power conversion efficiency after 30 days of exposure in the atmosphere without encapsulation. The present work definitely paves a facile and effective way to develop low-cost and high-efficiency chalcogenide-based photovoltaic devices.