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

Abstract

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.