Methyl red/ indium-tin-oxide organic diode: An electrical and optoelectronic study

摘要

Methyl red / indium-tin-oxide (ITO) organic diode is fabricated by simple, low cost solution drop casting method. Using the conventional Tauc method, the optical bandgap of methyl red is calculated 2.23 eV from the measured absorbance data. The electrical analyses of methyl red/ITO structure are carried out based on the thermionic emission model of Schottky barrier diode. The ideality factor, barrier height and series resistance are calculated using the standard method (5.40, 0.88 eV, 10(6) Omega), Bohlin's method (5.20, 0.87 eV, 1.5 x 10(6) Omega) and Cheung's method (4.88, 0.85 eV, 9 x 10(6) Omega) and the values of such parameters are in close agreement. In the optoelectronic study, a considerable improvement in photocurrent under steady illumination reveals a substantial photosensitivity of the device. The diode is also proved as a stable photo-switch owing to its fine photo absorbing quality. The photo response of the test structure is attributed to the presence of methyl red over layer and the phenomena is ascribed by the delocalization of pi electrons from the conjugated structure between the benzene and azo groups of methyl red.