Dual‐Function Interface Engineering of SnO ₂ Electron Transport Layers: Wettability Enhancement and Work Function Tuning for Efficient and Stable Perovskite Solar Cells and Minimodules

The commercialization of perovskite solar cells (PSCs) requires scalable device architectures that integrate high efficiency with long-term stability. Here, we present a dual-function interface engineering strategy in which polyethyleneimine (PEI) is incorporated into SnO₂ to simultaneously enhance surface wettability and tune the work function. This dual control suppresses oxygen-vacancy defects, establishes interfacial dipoles, and optimizes energy-level alignment, thereby enabling efficient carrier extraction and uniform perovskite crystallization. Supported by advanced characterization techniques and density function theory calculations, PEI-modified SnO₂ ETLs yield PSCs with a power conversion efficiency of 24.49% and scalable minimodules (24.8 cm²) achieving 22.56% efficiency. The minimodules further exhibit excellent stability, retaining 94% of their initial performance after 500 h of operation. This solution-processable, ambient-compatible modification provides both mechanistic insight and practical viability, offering a robust pathway toward commercial-scale perovskite photovoltaics.