Dual‐SAM Passivation of Quasi‐2D Perovskite Film for Efficient Photodetectors

Although quasi‐2D perovskites show promise for photodetection, their high surface defect density severely limits optoelectronic performance and operational stability. Herein, we engineered quasi‐2D PEA 2 MA 2 Pb 3 I 10 films with dual‐surface passivation using 1‐adamantanemethylamine (AdMA) and [2‐(9H‐carbazol‐9‐yl)ethyl]phosphonic acid (Me‐4PACz) self‐assembled monolayers (SAMs) as top/bottom surface modifiers, respectively, yielding high‐performance perovskite photodetectors with exceptional stability. The dual‐SAM layer not only reduces the defect density of perovskite film from 3.39 × 10 22 to 2.14 × 10 22 m −3 but also suppresses ion migration with improved ion migration activation energy from 0.0196 to 0.0405 eV. The optimized quasi‐2D perovskite photodetector exhibited remarkable performance with a high external quantum efficiency (EQE) of 64%, a responsivity of 0.26 A/W, an outstanding specific detectivity of 4.98 × 10 13 Jones, and excellent stability‐showing no measurable degradation after 10 000 light‐dark operational cycles in ambient air. This study provides fundamental insights into the role of SAMs in modulating the surface properties of 2D perovskites and offers a promising pathway for developing high‐performance optoelectronic devices.