Innovative In Situ Passivation Strategy for High‐Efficiency Sb₂(S,Se)₃ Solar Cells

Abstract An effective defect passivation strategy is crucial for enhancing the performance of antimony selenosulfide (Sb₂(S,Se)₃) solar cells, as it significantly influences charge transport and extraction efficiency. Herein, a convenient and novel in situ passivation (ISP) technique is successfully introduced to enhance the performance of Sb₂(S,Se)₃ solar cells, achieving a champion efficiency of 10.81%, which is among the highest recorded for Sb₂(S,Se)₃ solar cells to date. The first principles calculations and the experimental data reveal that incorporating sodium selenosulfate in the ISP strategy effectively functions as an in situ selenization, effectively passivating deep‐level cation antisite Sb_Se defect within the Sb₂(S,Se)₃ films and significantly suppressing non‐radiative recombination in the devices. Space‐charge‐limited current (SCLC), photoluminescence (PL), and transient absorption spectroscopy (TAS) measurements verify the high quality of the passivated films, showing fewer traps and defects. Moreover, the ISP strategy improved the overall quality of the Sb₂(S,Se)₃ films, and fine‐tuned the energy levels, thereby facilitating enhanced carrier transport. This study thus provides a straightforward and effective method for passivating deep‐level defects in Sb₂(S,Se)₃ solar cells.