Thermoelectric figure-of-merit of iodine-doped copolymer of phenylenevinylene with dialkoxyphenylenevinylene

The copolymers consisting of both unsubstituted and 2,5-dialkoxy-substituted phenylenevinylenes (P(ROPV-co-PV); RO = MeO, EtO and BuO) with ca. 30 mol% of dialkoxy-substituted units were synthesized to evaluate their thermoelectric properties. Iodine-doped P(ROPV-co-PV) exhibited high Seebeck coefficient with relatively high electrical conductivity among electrically conductive polymers ever reported. The effect of the stretching treatment on their thermoelectric properties was examined. Consequently, both P(MeOPV-co-PV) and P(EtOPV-co-PV) constantly showed high Seebeck coefficients with increased electrical conductivities by the stretching alignment because of an increase in the carrier mobility, while the Seebeck coefficient of P(BuOPV-co-PV) varied inversely with a variation of the electrical conductivity. We also evaluated thermal conductivity of the pristine and iodine-doped P(ROPV-co-PV) for calculations of their thermoelectric figure-of-merit ZT. To the best of our knowledge, consequent thermoelectric figure-of-merit ZT of all the iodine-doped copolymer with the stretch treatment is one of the highest thermoelectric performance among conducting polymers reported ever, which are comparable with that of an inorganic thermoelectric materials, such as β-FeSi2.