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It is still challenging to fabricate efficient large-area organic solar modules by solution processing. Processing window is important to obtain optimal aggregation of an active layer in large area for high efficiency. The star active layer of PM6:Y6 is processed from chloroform (for high efficiency) that has a narrow processing window due to the low boiling point of the solvent. In this work, the correlation between chemical structure (side chains) and processing solvents is investigated to obtain high efficiency and long processing windows. It is found that large side chains on the pyrrole ring are the key factor influencing the aggregation of active layer films. Short side chain (in Y6 and Y6-1O) will cause excess aggregation when processed from high-boiling-point solvent (chlorobenzene, CB), while long side-chain (in BTP-BO-4F, BTP-BO-4Cl, and BTP-eC9) can inhibit such aggregation and maintain high photovoltaic performance when processed from CB with wide processing window. In the end, over 25 cm 2 organic solar module via doctor blading based on PM6:BTP-eC9 active layer has been fabricated with a PCE of 14.07%.