2D Perovskite Engineering Enables Robust Self‐Assembled Monolayers for High‐Performance Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) are critical hole‐selective contacts in inverted perovskite solar cells (PSCs), yet their practical implementation is hindered by desorption and aggregation during solution‐based perovskite deposition. Here, we report a transient two‐dimensional (2D) perovskite protection strategy using volatile propylammonium chloride, which temporarily shields SAMs from solvent‐induced degradation and subsequently decouples during thermal annealing. This mechanism preserves the integrity of the SAM interface while enabling uniform crystallization of large‐area perovskite films and efficient charge extraction. Consequently, PSCs achieve a power conversion efficiency (PCE) of 26.14% for 0.05 cm 2 devices, 23.27% for a 5 × 5 cm 2 mini‐module, and 22.34% for a 30 × 30 cm 2 module (615.7 cm 2 active area). Notably, the large‐area module retains 90% of its initial efficiency after 2000 h of continuous maximum power point operation, demonstrating both high performance and operational stability, highlighting a scalable route for reliable perovskite photovoltaics.