Ultraviolet Transient Photocurrents in Polyethylene with Zero External Field

Transient photocurrents in polyethylene with zero external field were investigated in the ultraviolet region. There were considerable differences between the results obtained with Al and Au electrodes. The transient photocurrent with Al electrodes had a simple time constant which decreased with increasing temperature with the activation energy Et=0.1 eV. This behavior could be explained by a simplified model on the basis of photoinjection of electrons from Al electrodes. On the other hand, in the cases of Au and Ag electrodes having relatively high work functions the direction of the phototransients was found to be opposite to that observed with Al electrodes. This observation will be discussed in terms of diffusion of photo-excited positive carriers in the bulk.