Abstract After doping with a halogen (X=I, Br or Cl) of the PVK, there is charge transfer (CT) complex formation as shown by electron spin resonance (ESR), optical absorption and X-ray electron spectroscopy (XPS). The conductivity of this CT-complex depends on halogen. For halogen with higher electronegativity (Br, Cl) there is not only CT-complex formation, but there is also some polymer degradation by the halogen. This degradation is amplified when the temperature during doping is increased. It results in the formation of a new amorphous polymer with some crystallites of carbazole and NH 4X embedded in an amorphous polymeric matrix. The increase of the conductivity of these new polymers is probably related to the formation of some π bonds. It appears that, after all, doping with iodine is more promising since there is some polymer degradation even at room temperature with other halogens.