Optimization of Crystal Growth and Defect Passivation of FASnI₃ Film by Using 2-Pyridylthiourea for Sn-Based Perovskite Solar Cells

Currently, tin (Sn) is the most efficient alternative to lead (Pb) for perovskite solar cells (PSCs). However, the fabrication of pinhole-free uniform and highly crystalline Sn-perovskite typically, FASnI3 films remains a crucial factor due to their rapid crystallization. To address this issue, we incorporated 2-pyridylthiourea (2PTU) into the precursor solution during FASnI3 film fabrication. Based on the morphology, structure, and elements analysis, we have observed that 2PTU impacts the growth of perovskite crystals and surface morphology by coordinating with SnI6 4– octahedral. Moreover, the 2PTU-added FASnI3 film contained fewer defects and a prolonged carrier lifetime. These substantial improvements in the FASnI3 film resulted in an enhanced open-circuit voltage, elevating the power conversion efficiency of Sn-PSC from 10.23% (pristine) to 12.85% (2PTU). Significantly, after 500 h of continuous illumination at maximum power point tracking under one sun, the 2PTU-added FASnI3-based PSCs showed remarkable stability and maintained above 90% of their initial PCE.