Tunability of Mobility and Conductivity over Large Ranges in Poly(3,,3'"-didodecylquaterthiophene)/Insulating Polymer Composites

Semiconducting polymers are currently being considered as active layers in field-effect transistors in which high charge carrier mobility and low off conductivity are important. For other applications, such as certain spintronic mechanisms, the opposite characteristics are desirable. Blending such polymers with insulating polymers would be expected to lower the mobility. In this paper we report that the use of hydrocarbon polymers such as polystyrene as insulatorsigenerally raises the mobility when the semiconducting polymer is poly(bisdodecylquaterthiophene). A high mobility value of nearly 0.1 cm(2)/V . s was obtained for an optimal blend. While this is counterintuitive. It is consistent with a few other recent reports in order to lower the mobility significantly a much more polar and irregular blending agent is needed. The further addition of tetrafluorotetracyanoquinodimethane as a dopant gave a rare low mobility/high conductivity combination of properties, with a charge carrier density on the order of 10(19) cm(-3), Thus mobility and conductivity were tuned somewhat independently over 3 and 4 orders of magnitude respectively.