Blade coating of perovskite solar cells (PSCs) and modules has progressed considerably toward the industrial production of perovskite photovoltaics. Developing stable perovskite precursors is critical for achieving uniform coating over large areas. Here, the engineering of a perovskite precursor solution consisting of 2-methoxyethanol (2-Me) and 1,3-dimethyl-imidazolidinone (DMI) with superior intermediate phase stability that enables scalable production of efficient perovskite solar modules is reported. With this perovskite precursor solution, uniform and pinhole-less perovskite film is deposited over a large area of > 100 cm(2) and higher-efficiency PSCs and modules are obtained. The best-performing unit cell and module with n-i-p configuration reach power conversion efficiencies of 23.4% and 20.1%, respectively. Additionally, a series of non-destructive metrology methods, such as spectroscopic ellipsometry, hyperspectral photoluminescence, electroluminescence, and laser beam-induced current mapping, are employed to assess and guide the development the blade-coated perovskite modules. This results show that rational engineering of precursor inks for blade coating is promising for the scalable production of efficient perovskite solar modules.