Surface-Dominant Fluorinated Structures in Sn-Based Perovskite Solar Cells

The incorporation of two-dimensional (2D) structures into Sn-based perovskites has been confirmed to effectively improve both efficiency and stability. While the use of fluorinated organic materials is known to improve device performance, a detailed understanding of their mechanisms has remained elusive. In this study, we demonstrate that incorporating a trifluoromethyl-substituted organic halide material (F₃-BAI) directly into the perovskite precursor without additional surface treatment results in predominant surface localization and acts as surface passivation. This passivation reduces charge recombination and enhances charge extraction, leading to an increased power conversion efficiency in perovskite solar cells (PeSCs). The device incorporating the fluorinated material achieved an efficiency of up to 12.92% compared to 10.01% for the control device. Furthermore, the hydrophobicity of the fluorinated groups substantially improves the stability of Sn-based PeSCs, particularly in humid environments (60%) and ambient air.