POLYANILINE SCHOTTKY-BARRIER - EFFECT OF DOPING ON RECTIFICATION AND PHOTOVOLTAIC CHARACTERISTICS

Schottky diodes of aluminium/polyaniline (PAn)/indium-tin oxide (ITO) with large area (0.3-1 cm2) are prepared using the casting technique. The PAns investigated involve undoped polyaniline (undoped PAn), polyacrylic acid-doped polyaniline (PAA-doped PAn) and toluene-4-sulfonic acid-doped polyaniline (TSA-doped PAn). The diodes, in which the undoped and doped PAns behave as p-type semiconductors, exhibit a moderate rectifying behaviour and low leakage current. Photovoltaic measurements on the three diodes at various light intensities from 1 to 40 mW/cm2-show power conversion efficiencies of about 0.04, 0.57 and 0.88%, respectively, at a light intensity of 1 mW/cm2 (which, for doped PAns, are comparable with that of HCl-doped (CH)x, 1% at 7 mW/cm2). The conversion efficiency decreases with increasing light intensity (1 to 40 mW/cm2). Acid-doping of PAn can cause a higher photovoltaic conversion efficiency.