Multi-functional molecule advancing the efficiency of pure 3D FASnI3 perovskite solar cells based on the tin tetraiodide reduction method

Tin halide perovskite solar cells (PSCs) show promise as lead-free photovoltaic alternatives, but face challenges due to Sn2+ oxidation and crystallization control issues. We introduce a novel method to enhance PSC performance: by reducing tin tetraiodide with elemental tin, we produce a highly reactive Sn2+ precursor solution, yielding perovskite films with improved crystallinity, smoother surfaces, and reduced Sn4+ residue. Additionally, we incorporate phenylhydrazine-4-sulfonic acid (PHPA) as an additive to further enhance film quality. PHPA synergically forms hydrogen bonds with formamidinium cations (FA+) and coordinates with Sn2+ to inhibit its oxidation, reducing defective states within the film. This results in an FASnI3 perovskite device achieving a remarkable PCE of 12.22%. Notably, the device maintains 80% of its initial PCE after 200 h under light-soaking. Our approach offers a reproducible method for fabricating high-performance and stable tin halide PSCs, addressing key challenges and advancing sustainable energy solutions.