Photoconductivity of Polycyclic Aromatic Compounds

The voltage, light intensity, and temperature dependences for photocurrent in multi-ring compounds were studied as well as the photocurrent produced by the limited-area illumination. The photocurrent was found to be ohmic over the range of voltage employed. The photocurrent increased linearly with the intensity of light in the region of low light intensity, while it increased as the fractional power of the light intensity in the region of high intensity. The photocurrent increased with an increase of the temperature, and the activation energy of the photocurrent was found to be independent of the wavelength and the intensity of illumination. The signs of the thermoelectric power as well as the polarity for the maximum photocurrent, and the experiment on the limited-area illumination indicated that the conduction in polycyclic aromatic compounds was due predominantly to electrons which were generated in the bulk of aromatic film.