Buried Interface Modification Using PEACl for Efficient and Stable Inverted Solar Cells

ABSTRACT Although [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl] phosphonic acid (Me‐4PACz) self‐assembled molecules have been widely used in inverted perovskite solar cells (PSCs), their strong hydrophobicity is difficult to form a dense perovskite film, and the defect passivation ability is weak, resulting in serious non‐radiative recombination loss of carriers between them and the perovskite film, which limits the further improvement of device performance. Here, we introduce 2‐phenylethylamine hydrochloride (PEACl) to modify the buried interface in PSCs. The incorporation of PEACl molecules not only reduces the substrate's hydrophobicity, enabling uniform growth of perovskite film, but also enhances carrier transport at the interface through π‐π stacking interaction with Me‐4PACz, thereby reducing charge accumulation. Furthermore, PEACl reacts with PbI 2 at the bottom interface to form a 2D structure that effectively passivated interface defects and suppressed non‐radiative recombination. Consequently, the PEACl‐treated PSCs demonstrate an impressive power conversion efficiency of 26.08%. Notably, these PEACl‐treated PSCs exhibit exceptional stability, retaining 90.80% of their initial efficiency after 2 500 h of continuous operation at the maximum power point under ambient conditions at 55°C, using 1‐sun illumination without a UV filter. The effectively suppressed of interface defects by PEACl at the buried perovskite interface offers a promising strategy for advancing the commercial viability of PSCs.