Hydrothermal growth of Sb2S3 thin films on molybdenum for solar cell applications: Effect of post-deposition annealing

The binary chalcogenide material antimony sulfide (Sb2S3) has attracted significant attention as a potential absorber material for photovoltaics (PVs) owing to its suitable bandgap of ~1.7 eV and other unique properties. However, only a few substrate-configured Sb2S3 thin-film solar cells (TFSCs) have been reported, and they demonstrated an extremely low power conversion efficiency (PCE, η < 2.5%) owing to the unfavorable (hk0) orientation of Sb2S3. In most studies, Sb2S3 absorber layers were grown through physical vapor deposition or high-vacuum methods. By contrast, we used a facile hydrothermal approach to deposit Sb2S3 thin films on molybdenum and investigated the effect of post-deposition annealing on the structure, orientation, and morphology of Sb2S3 thin films. Annealing at temperatures ranging from 0° to 350°C transformed the Sb2S3 thin films from nearly amorphous to polycrystalline with large, horizontally aligned plate-like grains. All the annealed Sb2S3 thin films were confirmed to have a preferred orientation along the (hk0) crystal direction. The fabricated substrate-configured TFSCs with SLG/Mo/Sb2S3/CdS/i-ZnO/Al-doped ZnO/Al configuration exhibited the highest PCE of ~1.0%. Further, over 95% of this initial efficiency was maintained after 90 days. We also addressed the underlying reasons for the low efficiency of Sb2S3 TFSCs to provide a pathway for improving the device performance in the future.