The formation of methyl radicals in a suspension of the donor/acceptor pair PCDTBT:PC₆₀BM in di-chloro-benzene (diCB) and 1-butyl-3-methylimidazolium acetate as ionic liquid (IL) has been recorded at 77K temperature under UV illumination of a continuous waves Xe-lamp (30 mW/cm² output power density). Taking into account that methyl radicals were not found in pure 1-butyl-3-methylimidazolium acetate under the same conditions of illumination, it was supposed that acetate anion interacts with the positive PCDTBT polaron due to the electron transfers to the polymer and therefore polaron annihilation.