This paper describes a simple approach for reducing the contact resistances at the source/drain (S/D) contacts in solution-processed n-channel organic thin-film transistors (OTFTs). Blending poly(ethylene glycol) (PEG) into the fullerene semiconducting layer significantly improved the device performance. The PEG molecules in the blends underwent chemical reactions with the Al atoms of the electrodes, thereby forming a better organic-metal interface. Further, the rougher surface obtained after the addition of PEG could also increase the effective contact area, thereby reducing the resistance. As a result, the electrical properties of the devices were significantly improved. Unlike conventional bilayer structures, this approach allows the ready preparation of OTFTs with a low electron injection barrier at the S/D contacts.