R.D. Gould and T.S. Shafai

Thin Films Laboratory, Department of Physics, School of Chemistry and Physics, Keele University, Keele, Staffs. ST5 5BG, U.K.

Electronic conduction has been investigated in evaporated lead phthalocyanine thin films with aluminium electrodes. In contrast to previously investigated samples where the injecting electrode was a gold ohmic contact, these samples did not exhibit space-charge-limited conductivity, but showed carrier excitation via a field-lowering mechanism with a logJ a V^1/2 current density-voltage (J-V) characteristic. Both polarities showed two regions in the J-V characteristics having different slopes, leading to the conclusion that conduction is via Schottky and Poole-Frenkel emission at lower and higher voltages respectively. In the presence of air there was a decrease in conductivity, which was attributed to the effects of oxygen at the electrodes.