Aqueous-Solution-Based Approach Towards Carbon-Free Sb₂ S₃ Films for High Efficiency Solar Cells

Sb₂ S₃ is a new kind of photovoltaic material that is promising for practical application in solar cells owing to its suitable bandgap, earth-abundant elements, and excellent stability. Here, we report on an aqueous-solution-based approach for the synthesis of Sb₂ S₃ films from easily accessible Sb₂ O₃ as antimony source. In this reaction, 3-mercaptopropionic acid was applied as both solvent and sulfur precursor, aqueous ammonia was employed as a solvent. After simple annealing at a temperature as low as 270 °C, the spin-coated precursor solution can generate compact, flat, uniform, and well-crystallized Sb₂ S₃ film. Mechanistic study showed that the formation of Sb-complex with ammonium carboxylates leads to the successful dissolution of Sb₂ O₃ powder. A suitable annealing process was able to generate carbon-free Sb₂ S₃ films. Planar heterojunction solar cell based on the as-prepared Sb₂ S₃ film delivered a power conversion efficiency of 5.57 %, which is the highest efficiency of solution-processed planar heterojunction Sb₂ S₃ solar cells and a high value in all kinds of Sb₂ S₃ solar cells. This research provides a convenient approach for the fabrication of device-quality Sb₂ S₃ films, and highlights solution processing of carbon-free metal chalcogenide thin films as a suitable process for application in optoelectronic devices.