Thermally stimulated current measurements on a UV irradiated organic photoreceptor layer

Thermally stimulated current (TSC) measurements have been performed on a xerographic photoreceptor which has been treated with ultraviolet (UV) radiation. The charge transport layer of the photoreceptor consists of a polyester molecularly doped with an arylamine substituted hydrazone which was observed to undergo UV induced rearrangement to an indazole derivative. The indazole derivative is transparent to the wavelength component inducing the photo-reaction so that the depth of converted material gradually extends farther into the CTL with UV exposure time. The xerographic residual potential variation with irradiation time is attributed to the formation of a potential barrier to transfer of charge from hydrazone hopping states to indazole hopping states. The mobility activation energy obtained from TSC measurements is 0.22 eV for unirradiated material, which decreases to 0.12 eV after 1200 s of irradiation. The latter energy is identified as a signature of the potential barrier. This identification is corroborated by the correlation between the decrease of the residual potential and the increase of the TSC activation energy after 3600 s of irradiation.