Electrical conduction mechanisms in thermally evaporated thin films of 2-(4-biphenyly)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole

The AC electrical behaviour of sandwich devices fabricated entirely in vacuum using thermally evaporated thin films of 99 + % pure 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4 oxadiazole (Bu-PBD) and gold electrodes, is observed over the frequency range 10(4) to 10(7) Wt and the temperature range 297 to 398 K. The capacitance and dissipation factor decrease with increasing frequency and at high frequency (> 2 x 10(6) Hz) the capacitance and dissipation factor are not temperature dependent. The results obtained show the relative importance of the variable range hopping model and band theory in describing the film conductivity. (C) 1998 Elsevier Science S.A. All rights reserved.