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, FASnI 3 films remains a crucial factor due to their rapid crystallization. To address this issue, we incorporated 2-pyridylthiourea (2PTU) into the precursor solution during FASnI 3 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 SnI 6 4– octahedral. Moreover, the 2PTU-added FASnI 3 film contained fewer defects and a prolonged carrier lifetime. These substantial improvements in the FASnI 3 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 FASnI 3 -based PSCs showed remarkable stability and maintained above 90% of their initial PCE.