Photovoltaic properties of octithiophene-based Schottky and p/n junction cells: Influence of molecular orientation

We report here on the photovoltaic properties of Schottky and p/n junction cells based on octithiophene (8T). In the solid state, 8T is an elongated p lanar molecule with efficient p-type transport properties, We investigate i n particular the influence of molecular orientation of 8T films on light ab sorption, I/V characteristics and photocurrent spectra. We show that a subs tantial increase of the photocurrent density is obtained by aligning the 8T molecules horizontally and parallel to each other on the substrate by mean s of a simple rubbing technique. This improvement is attributed to a more e fficient light absorption rather than to an improvement of the charge trans port properties in the sandwich devices. (C) 2000 Published by Elsevier Sci ence B.V. All rights reserved.