Influence of the doping of the polymer on the dark and photoelectrical properties in the junction ITO/poly(4,4 '-dipentoxy-2,2 '-bithiophene)/aluminium

The transport properties of the system, ITO/poly(4,4'-dipentoxy-2,2'-bithio phene)/aluminium, were investigated both in the dark and under white light illumination for three different oxidation states of the polymer. A deterio ration of both the rectification properties in the dark and the photovoltai c performances was observed by increasing the doping level. The less-doped junction was tested in photoconductive mode and an exponential relationship was found between the photosensitivity and the reverse voltage applied to the junction. A photosensitivity of the order of 10(-3) A W-1 was achieved for an applied voltage as low as 2 V over the full range of the incident po wer intensity (0.4-33 mW cm(-2)). (C) 1999 Elsevier Science S.A. All rights reserved.