Environmentally benign and earth-abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have advanced rapidly through solution-based processing. However, scaling from laboratory-scale devices to modules remains a major challenge, largely because complex coordination networks in the precursors hinder the formation of uniform large-area films. Here we show that molecular-level regulation of metal–organic coordination can suppress the formation of cross-linked networks in precursor solutions, promoting efficient solvent removal and uniform selenization and crystallization. This coordination-controlled strategy enables the blade coating of highly homogeneous films over 10 cm2, realizing certified efficiencies of 14.2% for 1 cm2 cells and 13.0% for 10.5 cm2 modules, representing a leap-forward improvement in scalable kesterite photovoltaics. Beyond performance, the provided molecular insights into kesterite solution chemistry facilitate establishing a scalable and low-cost route towards industrial deployment of this thin-film solar technology.