In situ condensation reaction modulates crystallization kinetics of tin-lead perovskites for high-efficiency photovoltaic devices

While the regulation of crystallization kinetics is crucial for achieving high-performance tin–lead perovskites (ABX 3 ), current strategies have primarily focused on metal-halide coordination. In this study, we introduced L-tryptophan (L-Trp) as a multifunctional additive into the perovskite precursor solution to modulate crystallization kinetics through targeted interactions with the A-site organic cation. Along with experimental evidence (e.g., 1 H NMR, mass spectrometry), transition state calculations revealed that L-Trp targeted formamidinium iodide (FAI) through a trace-water-mediated in-situ condensation reaction and generated L-TrpHI and L-TrpFA. The solvation of these L-Trp derivatives with dimethyl sulfoxide (DMSO), which retarded DMSO desorption during annealing, effectively slowed the crystallization kinetics of perovskites. This tailored crystallization regulation yielded uniform perovskite films with improved crystallization quality. Furthermore, L-Trp derivatives strongly coordinated with Sn 2+ , which inhibited its oxidation and passivated defect states, thus suppressing non-radiative recombination. The optimized surface electronic structure of the perovskites further facilitated charge extraction and transport. As a result, the modified perovskite solar cells achieved a champion power conversion efficiency of 23.72%, with remarkable long-term operational stability, retaining 90% of their initial efficiency after 1350 h under continuous one-sun illumination. Mediated by trace water, the in-situ reaction between L-Trp and FAI generates L-Trp derivatives, which can undergo solvation with DMSO to delay the crystallization kinetics, thereby providing Sn-Pb PSCs with an efficiency of 23.72%. Download: Download high-res image (77KB) Download: Download full-size image