The Photoconductivity of Poly(N-vinylcarbazole). II. Dark Conductivity in a Sandwich-type Cell

The dark conductivity in a sandwich-type cell of PVCz films was investigated in a high vacuum, taking the temperature, the applied voltage, and the film thickness as parameters. In low fields, the conductivity was proportional to the applied voltage. In high fields, however, it was proportional to the fourth power of the applied voltage. This nonohmic dark conductivity in high fields may be attributed to the Pool-Frenkel effect. A model of the energy-level diagram is presented which can explain the dark conductivity in both low and high fields.