In this work, CZTSSe thin film is prepared by selenizing CZTS precursor with Sb and Sb2Se3 doping layer at the bottom. The XRD and Raman results demonstrate that kesterite CZTSSe thin film with preferred crystalline quality is prepared. XPS and EDS results indicate that the inserted Sb and Sb2Se3 atoms do not occupy the lattice of CZTSSe. Both Sb and Sb2Se3 will transfer into semi-liquid phase Sb2Se3 during selenization process, which diffuses into the surface of the absorber from the bottom of the absorber and finally volatilize at the elevated temperature. The semi-liquid phase Sb2Se3 effectively promotes the grain growth of CZTSSe. CZTSSe thin film with Sb2Se3 doping layer has a better crystalline quality than that with Sb doping layer, which exhibited a best PCE of 4.03%, featuring 361.15 mV Voc, 23.19 mA/cm2 Jsc and 48.23% FF.

In recent years, CsFAMAPbI1-xBrx-based lead halide perovskite solar cells have been widely studied for their high efficiency. However, lead-based perovskite films exhibit inherent defects, leading to significant stability degradation under high humidity and temperature. In this study, we used three alcohol additives (IPA, IBA, and NBA) combined with CB-PMMA to form mixed solutions, focusing on their effects on large grain formation and thermal stability enhancement. The CB-PMMA mixed solution provided the least improvement in thermal stability, with CsFAMAPbI1-xBrx films degrading after annealing at 150 °C for 9 hours. In contrast, the CB/IPA-PMMA, CB/IBA-PMMA, and CB/NBA-PMMA mixed solutions significantly enlarged perovskite grain sizes, reduced grain boundary counts, lowered carrier recombination at grain boundaries, and improved device photocurrent and fill factor. The optimized perovskite films maintained a high photoelectric conversion efficiency of 15.42% after annealing at 150 °C for 9 hours, demonstrating excellent thermal stability.