A Novel Multi‐Sulfur Source Collaborative Chemical Bath Deposition Technology Enables 8%‐Efficiency Sb2S3 Planar Solar Cells

Sb2S3 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 high‐quality 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 S2‐ releasing 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 Sb2S3 solar cells to date. This study is expected to shed new light on the fabrication of high‐quality Sb2S3 film and further efficiency improvement in Sb2S3 solar cells. Sb2S3 planar solar cell with a power conversion efficiency first exceeding 8% is achieved based on the high‐quality Sb2S3 absorber film fabricated using a novel multi‐sulfur source collaborative chemical bath deposition technology.