Abstract

Scalable inverted perovskite solar cells require top interfaces that combine defect passivation with spatially uniform electron extraction as the device area increases. Low-dimensional capping layers based on bulky spacer cations can suppress surface recombination, but poorly controlled molecular packing often introduces transport barriers and local interfacial heterogeneity. Here, we introduce indol-3-ylethylammonium iodide (Ind) as a π-electron-rich spacer cation for asymmetric lamellar templating at the perovskite/C₆₀ junction. The heteroatom-polarized indole framework creates lateral electrostatic anisotropy within the aromatic plane, promoting face-to-face spacer association and aligning the lamellar interphase. The resulting π-rich lamellar interphase suppresses interfacial recombination, preserves electron extraction, and improves spatial optoelectronic uniformity in large-area devices. Ind-based devices achieve a certified efficiency of 26.94% in small-area cells and a certified module efficiency of 23.21% for a 25 cm² monolithic module. They further retain > 93% efficiency after 1000 h at 85^◦C and maintain 85% of their initial efficiency after 1800 h under continuous 1-sun MPP tracking. These results identify lateral electrostatic anisotropy as a molecular design principle for scalable perovskite/C₆₀ top interfaces.