A high performance near-infrared organic phototransistor is achieved via introducing a small molecule acceptor as an electron trapping site into the narrow-bandgap conjugated polymer films. With only 10% (wt) addition of the acceptor molecule, the photoresponse to light of 850 nm has been significantly improved with a best photoresponsivity up to 2000 A W-1, high detectivity of 1016 Jones and fairly good photosensitivity in the order of 106.