This study presents a synergistic bimolecular interlayer (SBI) strategy to enhance the performance of inverted perovskite solar cells (PSCs) by reducing nonradiative recombination. The SBI is composed of 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI). MPA forms strong P-O-Pb covalent bonds at the perovskite surface, reducing surface defects and upshifting the Fermi level. PEAI creates a negative surface dipole, enhancing the n-type character of the perovskite surface and improving electron extraction. The resulting p-i-n device achieves a stabilized power conversion efficiency (PCE) of 25.53% and a minimal nonradiative recombination-induced Voc loss of 59 mV, one of the smallest reported values. The certified efficiency is 25.05%. The SBI strategy demonstrates the effectiveness of cooperative interface engineering in improving perovskite solar cell performance.This study presents a synergistic bimolecular interlayer (SBI) strategy to enhance the performance of inverted perovskite solar cells (PSCs) by reducing nonradiative recombination. The SBI is composed of 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI). MPA forms strong P-O-Pb covalent bonds at the perovskite surface, reducing surface defects and upshifting the Fermi level. PEAI creates a negative surface dipole, enhancing the n-type character of the perovskite surface and improving electron extraction. The resulting p-i-n device achieves a stabilized power conversion efficiency (PCE) of 25.53% and a minimal nonradiative recombination-induced Voc loss of 59 mV, one of the smallest reported values. The certified efficiency is 25.05%. The SBI strategy demonstrates the effectiveness of cooperative interface engineering in improving perovskite solar cell performance.