Lewis acid additive semicarbazide hydrochloride improves the formation of α-phase FAPbI3-based films and promotes a homogeneous vertical distribution of A-site cations through a deprotonation–reprotonation process. The upgraded device performance reaches up to 26.12% with high stability, and mini-module perovskite solar cells achieving 21.47% (area, 11.52 cm2) demonstrate great scalability.