摘要
Formamidinium lead triiodide (FAPbI3) is a highly promising semiconductor for efficient and thermally stable perovskite solar cells (PSCs). However, its photoactive black alpha-phase often transitions to the photoinactive yellow delta-phase below 150 degrees C, degrading photovoltaic performance. Here, we introduce cesium thiocyanate (CsSCN) as a dual-functional additive into the perovskite precursor solution to stabilize the alpha-phase, enhance phase purity, and improve device efficiency. X-ray diffraction (XRD) confirms CsSCN promotes pure alpha-phase formation, while molecular dynamics (MD) simulations reveal that co-doping with Cs+ and SCN- ions yields a more stable lattice structure. CsSCN-modified PSCs achieve a peak power conversion efficiency (PCE) of 22.91 % and retain over 90 % of their initial performance after 1000 h under continuous illumination. These improvements stem from larger grain sizes (up to 1.5 mu m), enhanced film uniformity, and reduced defects, which collectively improve charge transport. By addressing phase instability and degradation, CsSCN offers a robust strategy to advance the efficiency and durability of perovskite solar cells, paving the way for their commercial viability.