Post‐deposition Treatment of Sb ₂ Se ₃ Enables Defect Passivation and Increased Carrier Transport Dimension for Efficient Solar Cell Application

Post-deposition treatment in thin film preparation can compensate for the inability of directly deposited films by fundamentally altering the chemical, electrical, morphological and defect properties. However, as an emerging photovoltaic material, the synthesis of Sb₂Se₃ film has so far been unable to effectively adjust the carrier transport and defect properties, thereby hindering performance improvement. In this study, we report that P₂O₅ can serve as a post-deposition treatment material to modify the chemical and electrical properties of Sb₂Se₃ thin films. Through experimental analysis, we discover that P atoms from P₂O₅ can occupy the Se vacancy and convert the deep-level anti-site defect (Sb_Se) to a shallower defect (P_Se), rendering efficient defect passivation. Simultaneously, P-doping induced lattice distortion closes the ribbon spacing of (Sb₄Se₆)_n, promoting efficient carrier transport from one dimension to three dimensions. This structure reduces the restriction of carrier transport in low-dimensional materials, which suppresses the carrier non-radiative recombination and improves the carrier transport efficiency. As a result, we achieved a champion power conversion efficiency of 9.50 % in thermal evaporation derived Sb₂Se₃ superstrate solar cells. This study provides a novel strategy and guidance for passivating deep-level defects and modifying the crystal structure of low-dimensional solar cell materials.