Modulating Phosphonic Acid Anchoring Groups in Self‐Assembled Molecules via Dibutyl Ether‐Mediated Multi‐Interactions for High‐Performance Large‐Area Organic Solar Cells

Abstract Self‐assembled molecules (SAMs) have become a prominent class of hole‐transport materials for organic solar cells (OSCs). However, their amphiphilic nature promotes micelle formation, severely limiting performance in large‐area (>1 cm 2 ) devices. Current modification strategies primarily focus on carbazole headgroup engineering while seriously overlooking the crucial phosphonic acid anchoring groups, leading to persistent interfacial defects and incomplete surface coverage. Herein, a multiple‐interaction‐suppressed aggregation (MISA) strategy is introduced, employing dibutyl ether (DBtE) as a solvent additive that concurrently enables: 1) selective electrostatic interactions with hydroxyl groups in phosphonic acid, 2) directional steric hindrance effects to inhibit the self‐aggregation, and 3) the regulated film‐formation kinetics via low volatility. The synergetically theoretical and experimental characterizations verified the DBtE's ability to optimize substrate‐anchoring precision by reconstructing aggregation behavior, thereby enhancing surface coverage and passivating oxygen vacancy defects concurrently. These modifications significantly suppress interfacial trap‐assisted recombination while enhancing charge extraction capability. Indeed, MISA‐engineered devices achieve a best efficiency of 20.3% (vs 18.9% for controls) in small‐area cells. More strikingly, thanks to the modulated aggregation of the SAM layer via the MISA strategy, a champion PCE of 18.6% is harvested at 1.0 cm 2 scale, which is one of the highest reported for 1 cm 2 large‐area OSCs.