Electrical properties of polyvinylcarbazole-tetracyanoquinodimethane charge transfer complexes

Electrical properties of polyvinylcarbazole-tetracyanoquinodimethane (PVK:TCNQ) charge transfer complexes were investigated as a function of the composition of the mixture, temperature, pressure and the method of sample preparation. It was shown that the electrical conductivity of the PVK:TCNQ complex (for TCNQ content <10% by weight) increased only slowly with increasing concentration of TCNQ and was only slightly higher than the conductivity of pure PVK. At higher TCNQ concentrations however an abrupt increase of the complex conductivity was observed. This effect may be attributed to the formation of semi-conductive tracks composed of uncomplexed neutral TCNQ molecules. The electrical conductivity of PVK:TCNQ complex was lower than the conductivity of TCNQ alone. The activation energy for electrical conductivity in the complex decreased with increasing TCNQ concentration from 0.99 eV for pure PVK to 0.37 eV for PVK:TCNQ (6:1) complex. The high field conductivity of the PVK:TCNQ complex could be explained by using the Poole-Frenkel model.