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

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. Perovskite solar cells lose efficiency due to defect driven recombination, while solvent based passivation undermines stability and scalable manufacturing. Liu et al. use a solvent-free vapor deposited organic salt to create a conductive interface and passivate defects, boosting device performance.