Molecular Induced Patching Process Improving Film Quality for High-Efficiency Cd-Free Antimony Selenosulfide Solar Cells

The preparation of thin films with flat, compact morphology and fewer defects is the key to the efficiency of solar cells. For antimony selenosulfide (Sb-2(S,Se)(3)), developing flexible preparation methods that can regulate the structure of the films is crucial for the defect control and performance of the devices. Herein, an effective strategy is developed of intervening in the intermediate deposition process of Sb-2(S,Se)(3) film to regulate its growth on the titanium dioxide (TiO2) electron transport layer (ETL). Thioacetamide (TA) is introduced as an additive and sulfur source during the chemical bath deposition. By reacting with (SbO)OH, it not only eliminates the Sb2O3 phase, but also in-situ patches the pinholes in the Sb-2(S,Se)(3) film. In addition, it is found that the increase in sulfur content promotes the transformation of Sb-S defect to V-S defect, while a lower S/Se atomic ratio can simultaneously reduce the formation of Sb-S and V-S defects. As a result, a PCE of 8.52% is obtained, which is the champion efficiency for the solution-processed TiO2/Sb-2(S,Se)(3) solar cells. This work provides a guidance for synthesizing high-quality metal chalcogenide films on oxide substrates in terms of morphology and defect control.