Balancing Disparate Crystallization Kinetics in Sn–Pb Perovskites Using a Sulfaguanidine Additive for High-Performance Solar Cells

Mixed tin–lead (Sn–Pb) perovskites hold significant promise for efficient single-junction and tandem solar cells due to their tunable narrow bandgaps, but their performance is often hindered by disparate crystallization kinetics between Sn and Pb precursors and Sn 2+ instability. Herein, we introduce sulfaguanidine (SG) as a multifunctional additive. SG utilizes its dual sulfonyl (S═O) groups to coordinate with Sn 2+ /Pb 2+ ions, crucially balancing their disparate crystallization rates. This kinetically harmonized growth, confirmed by in situ monitoring, significantly enhances film quality, suppressing Sn 4+ formation, reducing defects, and prolonging carrier lifetimes. Consequently, SG-modified inverted devices achieve a champion efficiency of 22.24% (vs 19.75% control) with improved stability. This work presents an effective coordination-driven strategy for kinetic harmonization, overcoming a key bottleneck and advancing efficient, stable Sn–Pb photovoltaics.