IODINE DOPING OF POLY(N-VINYLCARBAZOLE) THIN-FILMS - THERMAL-DEGRADATION

After thermal evaporation, poly(N-vinylcarbazole) (PVK) thin films wer e iodine doped at different temperatures between 300 and 570 K. It is shown that, while thermal evaporation shortened the chain length, ther e is a polymerization effect of the layer induced by iodine and anneal ing. The d.c. conductivity measurements show that, while the iodine do ping increases the conductivity, it is still quite poor because the ch ain of the polymer is saturated. However, after annealing at 570 K, al l the experimental studies (IR absorption, photoelectron spectroscopy (XPS), scanning electron microscopy) have shown that there is PVK degr adation, with NH4I precipitation in an amorphous polymer matrix. The e lectron spin resonance (ESR) and the conductivity studies are in good accordance with this polymer degradation. After annealing the carrier density increases, with the formation of conjugated chains, which just ifies the increase in the conductivity. (C) 1998 Elsevier Science Ltd. All rights reserved.