A Solution-Doped Polymer Semiconductor: Insulator Blend for Thermoelectrics

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer- thick films that feature a fine distribution of the F4TCNQ dopant: semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm(-1) and Seebeck coefficient from 100 to 60 mu V K-1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m(-1)K(-1) gives rise to a thermoelectric Figure of merit ZT similar to 10(-4) that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant: semiconductor: insulator ternary blends.