Solvent-Assisted Heterojunction Interface Passivation via DMSO Modification for High-Efficiency Sb₂Se₃ Solar Cells

Antimony selenide (Sb₂Se₃) has recently surpassed the benchmark of 10% power conversion efficiency, establishing itself as a highly promising photovoltaic absorber. However, its further development is largely limited by severe performance losses within the space charge depletion region near the heterojunction interface. Here, we introduce a solvent-assisted annealing strategy utilizing dimethyl sulfoxide (DMSO) to effectively passivate the surface defects. The DMSO treatment simultaneously removes surface oxides and incorporates trace sulfur into the near-surface region, thereby neutralizing surface states. Notably, the incorporated sulfur passivates deep-level selenium vacancy defects V_Se2 and V_Se3. Theoretical calculations reveal that DMSO chemisorbs onto Sb₂Se₃ via strong Sb─S bonding, which weakens the native Sb─Se lattice and facilitates controlled surface etching. This passivation of interface regions significantly improves the heterojunction quality, yielding a champion power conversion efficiency of 10.48%, corresponding to a 17% relative improvement over the control device (8.99%). This work presents a simple yet effective route to defect mitigation in Sb₂Se₃ photovoltaics, supporting their development toward practical application.