This paper proposes high-sensitive polymer/ fullerene bulk-heterojunction organic photodetectors (OPDs). A typical polymeric hole transport layer, (poly(3,4-ethylenedioxythophene):poly(styrenesulfonate), has substitutes with a molybdenum (VI) oxide (MoO3) layer. A thin C60 hole blocking layer was also introduced to reduce the dark current performance of the OPD. Optical interference simulation also accomplished along with the generalized transfer matrix method to show the behavior of wavelengths in OPDs. As a result, the lowest dark current density of 14 pA/cm 2 , and 40% above EQE, has achieved in the visible range. In regards to the photodetector characteristics, a reasonable responsivity of 0.21 A/W and high detectivity of 2.4 × 10 12 cmHz 1/2 /W were also obtained.