Cooperative Self‐Assembled Monolayers for Minimizing Voltage Losses in Inverted Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) such as the carbazole‐based 4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butylphosphonic acid (Me‐4PACz) are widely used as hole‐selective layers in inverted perovskite solar cells (PSCs). However, their performance is fundamentally constrained by (i) inadequate coverage of NiO x surfaces caused by molecular self‐aggregation and (ii) severe non‐radiative recombination at the buried perovskite interface due to insufficient defect passivation. Here, we introduce 4‐(trifluoromethyl) benzamide (4‐TB) into Me‐4PACz to form a synergistic SAM (Syn‐SAM) that simultaneously addresses both issues. The strong intermolecular π–π stacking between 4‐TB and Me‐4PACz suppresses aggregation, enhances surface uniformity, and increases the interfacial dipole, thereby improving hole extraction. Meanwhile, the carbonyl functionality of 4‐TB effectively passivates undercoordinated Pb 2+ defects at the buried interface, reducing interfacial energy losses. Consequently, the champion device delivers an efficiency of 25.27% with an ultralow voltage loss of 0.356 V and retains 80% of its initial efficiency after over 1300 h of continuous 1‐sun operation. A 1.82 eV wide‐bandgap PSC also achieves an efficiency of 19.44% with a high V OC of 1.33 V, demonstrating the broad applicability of this synergistic molecular‐engineering strategy.