Two band transport and disorder effects in a series of organic alloys: (TTF_1-xTSeF_x)-TCNQ (tetrathiafulvalene-tetraselenafulvalene-tetracyanoquinodimethane)

We have measured the thermoelectric power of the organic solid solutions (TTF1-xTSeFx)-TCNQ from 300 to 20 K. We find that in TTF- TCNQ the conductivity is dominated by the TCNQ chain down to 58 K and the TTF chain dominates between 58 and 38 K. In TSeF-TCNQ the cation and anion conductivities are comparable at all temperatures. We also find that the disorder leads to band tailing and a finite density of localized states within the Peierls gap. © 1976.