AbstractSolution processing of hybrid perovskite semiconductors is a highly promising approach for the fabrication of cost‐effective electronic and optoelectronic devices. However, challenges with this approach lie in overcoming the controllability of the perovskite film morphology and the reproducibility of device efficiencies. Here, a facile and practical aging treatment (AT) strategy is reported to modulate the perovskite crystal growth to produce sufficiently high‐quality perovskite thin films with improved homogeneity and full‐coverage morphology. The resulting AT‐films exhibit fewer defects, faster charge carrier transfer/extraction, and suppressed non‐radiative recombination compared with reference. The AT‐devices achieve a noticeable improvement in the reproducibility, operational stability, and photovoltaic performance of devices, with the average efficiency increased by 16%. It also demonstrates the feasibility and scalability of AT strategy in optimizing the film morphology and device performance for other perovskite components including MAPbI₃, (MAPbBr₃)₁₅(FAPbI₃)₈₅, and Cs_0.05(MAPbBr₃)_0.17(FAPbI₃)_0.83. This method opens an effective avenue to improve the quality of perovskite films and photovoltaic devices in a scalable and reproducible manner.This article is protected by copyright. All rights reserved