According to Shockley-Queisser's theory, the maximum power conversion efficiency (PCE) of a single-junction Sb 2 S 3 solar cell is up to 28.64%. [2] Owing to the wide band gap (≈1.7 eV), it is also a suitable candidate for tandem solar cell applications. As an emerging solar cell material, its device efficiency has fallen far short of expectations and has remained limited for 8 years. [3] It has been acknowledged that the material processing method plays a vital role in improving device efficiency. In this regard, tremendous efforts have been made in developing film deposition techniques for Sb 2 S 3 absorbers, including hydrothermal, chemical bath deposition (CBD), fast chemical approach, vapor transport deposition, thermal evaporation, rapid thermal evaporation, atomic layer deposition, and closed space sublimation. [4] Among them, the CBD approach is featured as simple operation, low cost and high production capacity, [5] and the systematical survey (Figure 1f) suggested that the overall PCEs of Sb 2 S 3 solar cells are all lower than that reported in 2014 by Choi et al. using CBD method (7.5%). [3] Therefore, CBD is recognized as the most feasible and successful method for chalcogenide film deposition.Sb 2 S 3 as a light-harvesting material has attracted great attention for applications in both single-junction and tandem solar cells. Such solar cell has been faced with current challenge of low power conversion efficiency (PCE), which has stagnated for 8 years. It has been recognized that the synthesis of highquality absorber film plays a critical role in efficiency improvement. Here, using fresh precursor materials for antimony (antimony potassium tartrate) and combined sulfur (sodium thiosulfate and thioacetamide), a unique chemical bath deposition procedure is created. Due to the complexation of sodium thiosulfate and the advantageous hydrolysis cooperation between these two sulfur sources, the heterogeneous nucleation and the S 2releasing processes are boosted. As a result, there are noticeable improvements in the deposition rate, film morphology, crystallinity, and preferred orientations. Additionally, the improved film quality efficiently lowers charge trapping capacity, suppresses carrier recombination, and prolongs carrier lifetimes, leading to significantly improved photoelectric properties. Ultimately, the PCE exceeds 8% for the first time since 2014, representing the highest efficiency in all kinds of Sb 2 S 3 solar cells to date. This study is expected to shed new light on the fabrication of high-quality Sb 2 S 3 film and further efficiency improvement in Sb 2 S 3 solar cells.
