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

Organic photodetector (OPD) based on simple bilayer heterojunction of pentacene and fullerene (C-60) 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 degrees C. For the same device, the maximum ratio of photocurrent to dark current density is found to be of the order of 2.5 x 10(3). Furthermore, OPD annealed at 90 degrees C has exhibited maximum detectivity of 2 x 10(10) Jones and response time of 180 ms. Structural characterization confirms formation of small grain size of pentacene and C-60 molecules thereby leading to improvement of the device performance. Our experimental signatures seem to indicate that pentacene and C-60 based OPD, after suitable engineering, might be promising for red light detection applications.