Electronic and photovoltaic properties of a single layer poly [3-(2",5"-diheptyloxyphenyl)-2,2′-bithiophene] devices

A Schottky type contact is formed at the junction between a single layer polymer poly [3-(2",5"-diheptyloxyphenyl)-2,2-bithiophene] in its neutral state and a low work function metal, aluminum. The electrical and optical properties have been investigated by means of current-voltage measurements in the dark as well as under illumination. Various important parameters such as the reverse saturation current density, barrier height, and the diode non-ideality factor are determined from the I-V curves in the dark of indium tin oxide (ITO)/poly[3-(2",5"-diheptyloxyphenyl)-2,2'-bithiophene]/aluminum (Al) sandwich structures using thermionic emission theory. Spectral response of the device is measured at various wavelengths giving a peak at about 540 nm. The incident photon to collected electron efficiency (IPCE%) is obtained for illumination through the ITO and aluminum sides. By illuminating the diode with white light and a monochromatic light of wavelength 540 nm, the open-circuit voltage, short-circuit current, power conversion efficiency, and fill factor (FF) are measured. The dependence of photocurrent on light intensity is also recorded and analyzed. (C) 2004 Elsevier B.V. All rights reserved.