Sodium α‐Olefin Sulfonate Interface Modification for High‐Performance Sb ₂ S ₃ Solar Cells

Antimony sulfide (Sb 2 S 3 ) has garnered significant attention in photovoltaics due to its excellent stability, high absorption coefficient, and accessibility. Unfortunately, the power conversion efficiency (PCE) of Sb 2 S 3 solar cells is hampered by severe interfacial defects and non‐ideal energy alignment, especially the inefficient hole extraction and transport. Herein, we introduce a convenient yet effective post‐treatment method using sodium α‐olefin sulfonate (AOS) as a surface passivator via spin‐coating. Systematic characterizations revealed that AOS successfully interacts with Sb 2 S 3 through forming a coordination bond between the Sb atom and the active sulfonate group (−SO 3 − ), which effectively suppresses interfacial recombination. More importantly, this engineering induces a favorable energy band bending at the Sb 2 S 3 /HTL junction, significantly reducing the hole extraction barrier. This optimized interface promotes more efficient and balanced charge collection, leading to a remarkable 26.4% improvement in carrier lifetime. These improvements collectively enable the PCE of the W‐AOS Sb 2 S 3 device to reach 8.20%, marking a 10.2% relative increase compared to the control device with a PCE of 7.44%. This study not only presents an effective approach to elevate the performance of Sb 2 S 3 solar cells but also accentuates the critical significance of Sb 2 S 3 /HTL interface quality in determining the overall efficiency of thin‐film photovoltaic devices.