Electrical conductivity of halogen doped poly( N-vinylcarbazole) thin films

Abstract

Thin films obtained by thermal evaporation of poly( N-vinylcarbazole) (PVK) powder have been doped with iodine and chlorine either by using a doped powder or by doping deposited films. The doping level of the thin films has been checked by X-ray photoelectron spectroscopy, then the samples have been electrically characterised by current–voltage and room temperature conductivity measurements. It is shown that chlorine reacts with PVK during doping which induces new compounds formation. Three different conductivity domains have been put in evidence, in the case of iodine doping. In the low field range the current is dominated by space charge effect. In intermediary field the current is ohmic. In the high field range the Poole–Frenkel effect is dominating. The evolution of properties of some samples is attributed to iodine ionisation of neutral iodine under high field. These results, obtained on evaporated thin films, are compared to those obtained with spin-coated PVK films.