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To investigate the effects of polymer donors with isomeric alkyl chains on the interfacial charge-transfer (CT) processes, the rates of exciton dissociation (kED) and charge recombination (kCR) have been calculated for complexes PM6/Y6 and PM6i/Y6, where isomer PM6i was designed by shifting the side chains in the electron-withdrawing units to the thiophene-bridges based on PM6. For complex PM6/Y6, kED of PM6 and Y6 exciton are calculated to be 1010–1012 s−1 and 1012–1013 s−1, and kCR is 1011–1012 s−1 for recombination of the lowest CT (CT0) excitons into the lowest triplet states of Y6, which are consistent with the experimental results. When going to complex PM6i/Y6, kED of PM6i exciton is higher than that of PM6 exciton, and of Y6 exciton is decreased to 1011–1012 s−1, but kCR is decreased to 1010–1011 s−1. The calculated results reveal that isomeric alkyl chains of polymer donors can enhance the polymer exciton dissociation and suppress the charge-recombination processes, underlining the important role of isomeric alkyl chains in design of polymer donors for high performance non-fullerene organic photovoltaics. [ABSTRACT FROM AUTHOR]