Effect of post-annealing temperature distribution on the orientation growth of Sb₂Se₃ films for efficient solar cells

Antimony selenide (Sb₂Se₃) has emerged as a highly promising photovoltaic absorber owing to its cost-effectiveness and distinctive one-dimensional crystal structure. Recent research has increasingly focused on crystal orientation engineering to improve the efficiency of Sb₂Se₃-based solar cells. Herein, an Sb₂Se₃ film prepared by chemical bath deposition was post-treated by open-space annealing (OSA) and close-space annealing (CSA). The two annealing methods resulted in different temperature distributions on the surface of the films, and the films showed a significantly different grain growth model and preferred orientation. The [301]- and [311]-oriented Sb₂Se₃ films were obtained following the normal grain growth model during close-space annealing. Enhanced grain orientation can substantially enhance carrier transport. Furthermore, close-space annealing can effectively passivate film defects. Finally, solar cells based on CSA-Sb₂Se₃ thin films achieved a power conversion efficiency (PCE) of 8.57%. This study provides a new insight for the orientation engineering of quasi-one-dimensional thin-film materials.