Zero bias high responsive visible organic photodetector based on pentacene and C60

•Pentacene/C60 based bilayer heterojunction photodetector has been fabricated.•Generation of equal magnitude of photocurrent under blue and red light.•Under zero bias and in the spectral range between 450 and 650 nm, EQE is 5–8%.•Improvement of responsivity with annealing the photodetector. Organic photodetector (OPD) based on simple bilayer heterojunction of pentacene and fullerene (C60) has been fabricated using thermal evaporation method. Absorption spectra of series of OPD, annealed at different temperatures, have been observed over a spectral range between 400 nm and 700 nm. At 0 V and at wavelength 650 nm, external quantum efficiency (EQE) = 5% and responsivity of 0.025 A/W have been achieved for an OPD annealed at 90 °C. For the same device, the maximum ratio of photocurrent to dark current density is found to be of the order of 2.5 × 103. Furthermore, OPD annealed at 90 °C has exhibited maximum detectivity of 2 × 1010 Jones and response time of 180 ms. Structural characterization confirms formation of small grain size of pentacene and C60 molecules thereby leading to improvement of the device performance. Our experimental signatures seem to indicate that pentacene and C60 based OPD, after suitable engineering, might be promising for red light detection applications.