Quasi-Vertically-Orientated Antimony Sulfide Inorganic Thin-Film Solar Cells Achieved by Vapor Transport Deposition

The one-dimensional photovoltaic absorber material Sb₂S₃ requires crystal orientation engineering to enable efficient carrier transport. In this work, we adopted the vapor transport deposition (VTD) method to fabricate vertically aligned Sb₂S₃ on a CdS buffer layer. Our work shows that such a preferential vertical orientation arises from the sulfur deficit of the CdS surface, which creates a beneficial bonding environment between exposed Cd²⁺ dangling bonds and S atoms in the Sb₂S₃ molecules. The CdS/VTD-Sb₂S₃ interface recombination is suppressed by such properly aligned ribbons at the interface. Compared to typical [120]-oriented Sb₂S₃ films deposited on CdS by the rapid thermal evaporation (RTE) method, the VTD-Sb₂S₃ thin film is highly [211]- and [121]-oriented and the performance of the solar cell is increased considerably. Without using any hole transportation layer, a conversion efficiency of 4.73% is achieved with device structure of indium tin oxide (ITO)/CdS/Sb₂S₃/Au. This work provides a potential way to obtain vertically aligned thin films on different buffer layers.