Interfacial modification of the perovskite surface with octocrylene (2-ethylhexyl-2-cyano-3,3-diphenyl-2-propenoate, OCT) is capable of enhancing humidity stability and passivating the defects of perovskite films. In this study, octocrylene can be attached to the surface of the perovskite, and the carbonyl group (CO) in octocrylene achieved excellent passivation through the Lewis base electron passivation of Pb²⁺ ions. By increasing the concentration of the octocrylene/IPA solution, the modified device exhibited an optimal PCE of 20.54% and a steady state output PCE of 19.75%. This study shows that the introduction of octocrylene in the preparation of perovskite could effectively enhance the performance of perovskite solar cells.