Hydrogen-Bonding-Guided Molecular Pair Suppresses Self-Aggregation for Uniform Passivation of Efficient Inverted...

Surface passivation is critical for high-performance perovskite solar cells (PSCs), yet achieving a uniform molecular layer is hindered by uncontrolled molecular aggregation, thereby limiting passivation efficiency. Here, we introduce an aggregation control strategy using two complementary molecules, 4-(trifluoromethyl)benzamidinium chloride (4BH) and piperazinium iodide (PI), directed by mutual N-H···F hydrogen bonding to form a uniform passivation layer. It pre-empts the disordered self-aggregation for each component alone, yielding a pinhole-free layer with homogeneous surface potential and photocurrent distribution. This aggregation-controlled interface delivers cooperative benefits: (i) a built-in potential enhancement (>0.19 V relative to control) that repels minority carriers, (ii) a nearly 70% reduction in trap density (from 2.12 × 1015 to 0.71 × 1015 cm-3), and (iii) a reduced electron injection barrier to C60, reflected in a ∼13.5% relative increase in the fill factor (from 73.77 to 83.72%). Consequently, inverted PSCs based on the 4BH:PI pair achieve a champion efficiency of 26.23% and retain 91% of their initial performance after 700 h of illumination at the maximum power point tracking, outperforming single-component devices. This work establishes aggregation control via specific hydrogen bonding as a design principle that has received limited attention for surface passivation, offering a simple molecular-pair engineering route toward efficient and stable perovskite photovoltaics.