Electrical properties of polymer Si heterojunctions

Metal/conjugated polymer film/silicon structures have been fabricated. Curr ent-voltage measurements have been performed with both Pi and Au metal elec trodes on n- and p-type Si substrates. The conjugated polymer was regioregu lar poly (3-octylthiophene) (P3OT). Rectification ratios as high as similar to 10(6) have been observed, with turn on voltages of similar to 1.5 V. Ev idence of Schottky barrier formation at the Al/polymer interface, and Fowle r-Nordheim tunnelling at the P3OT/p-Si interface is shown. Capacitance-volt age characteristics were obtained in the frequency range 10 Hz to 1 MHz. St rong frequency dispersion is observed which is indicative of the presence o f traps. A model is proposed to explain this dispersion which shows good ag reement with the experimental results. Preliminary optical results indicate that these diodes may have applications as optical sensors. (C) 1999 Elsev ier Science S.A. All rights reserved.