Evaluating the Film Orientation and Grain Boundary of Vacuum- and Solution-Processed Sb2S3 Films toward Efficient Solar Cells

The quasi-one-dimensional environment-friendly light-harvesting material Sb₂S₃ attracts tremendous attention for photovoltaic applications due to its superior materials and optoelectronic properties. The film orientation and grain boundary are two crucial concerns that greatly influence the device performance of Sb₂S₃ solar cells. In this work, the film orientation and grain boundary of Sb₂S₃ thin films processed by vacuum-based close-spaced sublimation (CSS) and solution-based chemical bath deposition (CBD) and hydrothermal deposition (HD) methods were evaluated. Careful characterization reveals that the vacuum-based method typically affords compact Sb₂S₃ films with pronounced [hk1] orientations, while solution-based methods deliver large-grained Sb₂S₃ films with ultralow grain boundary density. The CBD- and HD-processed devices yielded power conversion efficiencies of 6.43 and 6.51%, respectively, higher than 5.81% for the CSS-processed device. This should be closely associated with the balance of the favorable [hk1] orientations for efficient charge transport and the reduced grain boundary density for suppressed carrier recombination. This work provides insight information for further enhancing the performance of Sb₂S₃ solar cells by devoting more attention to the film orientation and grain boundary.