A series of polymer photodetectors with device configuration of ITO/PEDOT:PSS/P3HT:PC61 BM/C60/Al were prepared by using P3HT as the donor material and PC61BM as the acceptor material.By regulating the content of 1,8-diiodooctane(DIO)(V/V:1%,3%,5%)as a processing additive,the morphology of the active layer can be greatly improved.With C60 as the hole blocking layer,the dark current density of the device can be reduced by about an order of magnitude.When employing 3%DIO(V/V)in the active layer processing,the photodetetcors present the best performance,and the detectivity of the device is 1.52×1012 Jones at 540 nm under a bias of-0.1 V.Moreover,it also has a wider linear dynamic range of 60 dB as well as faster response speed(τr/Tf=0.53/0.71 μs)than those of devices with other content of DIO additives.