Achieving seasonal reproducibility in wide-bandgap sn-based perovskite solar cells via proton-locking interface engineering

The advancement of wide-bandgap (WBG) Sn-perovskite devices is substantially hindered by seasonal instability and limited reproducibility, primarily due to moisture-induced over-doping of PEDOT:PSS and Sn²⁺ oxidation. Here, we introduce a hydrophobic proton-locking interface engineering strategy by incorporating a novel S-benzyl-L-cysteine (SBLC) molecule into PEDOT:PSS. The hydrophobic benzyl backbone, amine groups, and significant dipole moment of SBLC facilitate strong coordination with Sn²⁺, effectively preventing moisture ingress and stabilizing buried interfacial energetics. This multifunctional modulation suppresses defects and promotes uniform crystallization across varying humidity and seasonal conditions. The optimized Target device, based on a WBG Sn-perovskite composition of PEA_0.10FA_0.75EA_0.15SnI_2.15Br_0.85, achieves a power conversion efficiency of 11.50% and retains >80% of its average performance across 279 devices fabricated monthly over 11 months, thereby establishing the first seasonal reproducibility benchmark. Furthermore, this approach exhibits increased stability of various stress conditions and enables a record efficiency of 17.40% in all-perovskite tandem devices featuring a WBG Sn-perovskite. These findings provide a scalable pathway toward reproducible, tandem-compatible, lead-free photovoltaics.