Liquid-derived, solvent-free vapor-mediated dimensional reconstruction yields a record fill factor in inverted perovskite solar cells.

Abstract

Despite recent advances, the fill factor (FF) of perovskite solar cells remains limited, largely owing to defect-related recombination. Paradoxically, most defect passivation approaches still depend on solvents, which deteriorate stability and pose challenges for large-scale fabrication. Here, we introduce a vapor-phase deposited from a liquid triethylammonium pentafluoropropionate (TEA-PFP) layer on top of perovskite. During deposition, TEA⁺ reacts with residual PbI₂ to generate a one-dimensional TEAPbI₃ interfacial phase, promoting continuous electronic coupling and facilitating charge extraction. Simultaneously, the Lewis-basic PFP^- anion passivates under-coordinated Pb²⁺ and suppresses vacancy formation, markedly reducing non-radiative recombination. The bulky TEA⁺ and strongly dipolar PFP^- groups anchor at surface Pb sites, forming a self-limited, surface-confined layer. As a result, we achieve a champion power conversion efficiency of 26.71% (certified 26.15%) and a record FF = 89.13% for small area device, while attaining a PCE of 25.32% for 1 cm² device. Moreover, this strategy effectively mitigates Ag⁺ diffusion during accelerated aging and preserves outstanding stability under combined thermal and humidity stress, providing a robust pathway to overcome the FF bottleneck in perovskite photovoltaics.