FORMATION OF ION-PAIRS AND CARRIER TRANSPORT IN UNDOPED AND DYE-DOPED POLY(N-VINYLCARBAZOLE) FILMS

Dark conductivities sigma-d of undoped and dye-doped poly(N-vinylcarbazole) (PVK) films have been measured at 298, 276, and 208 K over a wide range of static electric field E = 10(4) approximately 10(6) V/cm. The observed field dependence of sigma-d follows apparently the E0.6-power law, rather than the E1/2-power law of the well-known Poole-Frenkel (PF) type expression. Based on these experimental results, we have discussed the field-induced carrier generation processes from "ion pairs" (bound holes-charged acceptors) that are formed by an electron transfer between carbazole-rings and acceptors involved. Here we have taken into account the Onsager "dissociation-association" model to account for the observed electric field dependence of sigma-d, in which the dissociation of the ion pairs is enhanced by an applied field.