Abstract: The preparation of large-area organic solar cells through coating or printing is the key to realizing the industrialization of organic photovoltaics. In the organic solar cells, ZnO is a commonly used material as an electron transporting layer. However, the self-aggregation of ZnO nanoparticles and the uneven drying of films during printing cause large numbers of defects and poor uniformity in large-area films, which seriously affects the perfor-mance of large-area printed organic photovoltaic devices. In this work, a ZnO nanoink suitable for large-area slot-die coating was developed by regulating solvent and introducing an ink dispersion stabilizer. The rheological pro-perties of ZnO nanoink were regulated by using a mixed solvent, which solved the issue of edge effect in the coated film. The introduction of ethanolamine additives solves the problem of ink aggregation during storage and printing, allowing the ink to maintain long-term stability during 18 months of storage. With this nanoink, large-area films with a size of 100×100 mm² were obtained by slot-die coating. Such a film shows excellent film uniformity. Using the printed large-area ZnO films as electron transporting layer, an efficiency of higher than 14% is obtained for 1 cm² flexible organic solar cells.