A comparative study of two-step and three-step annealing processes for PVDF added FASnI3 film quality and solar cell

Among the non-toxic perovskites, tin-halide perovskite solar cell (PSC) is the most attractive for commercial application. However, their efficiencies and long-term stability currently lag behind their toxic lead-based counterparts, primarily due to high open-circuit voltage $(\mathrm{V}_{\mathrm{O}\mathrm{C}})$ loss and oxidation. In this study, we introduce poly(vinylidene fluoride) (PVDF) as a polymer passivation agent within the tin perovskite structure, leveraging the ability of the fluorine atoms in the PVDF chain to establish robust hydrogen bonds with organic cations. The interaction of PVDF with perovskite depends on the twostep and three-step annealing (3SA) process during the perovskite film growth. We obtained a PSC with higher efficiency in the 3SA process, reduced defect density, and improved film quality.