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.