Charge transport mechanism and thermoelectric behavior in Te:(PEDOT:PSS) polymer composites

Abstract

Polymer thermoelectics are an emerging class of materials for realizing flexible thermoelectric devices due to its low cost, solution processability and bio-compatibility. We report a systematic investigation of the charge transport and thermoelectric properties of polymer composites comprising of tellurium (Te) nanorods and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) spanning over a temperature range from 10 K up to 320 K. The temperature dependence of electrical resistivity for Te:(PEDOT:PSS) composites is dominated by the thermal assisted hopping following Mott’s and Efros-Shklovskii (ES) variable range hopping (VRH) mechanism. A cross-over from ES to Mott VRH model is observed near 105 K. The Seebeck coefficient and the electrical resistivity values for Te:(PEDOT:PSS) composites are found to decrease with the increase in PEDOT:PSS concentration at 300 K. Moreover, the thermal conductivity of the polymer composites is found to decrease due to enhanced phonon-phonon scattering ascribed to the acoustical mismatch between the Te-nanorods and PEDOT:PSS interface. The maximum thermoelectric figure of merit, ZT, of the polymer composites is estimated to be 0.013 ± 0.001 for Te:(PEDOT:PSS) (1:5) weight percentage. The bending test done on the polymer composite film and mechanical properties investigated using nanoindentation technique suggest the flexible nature of the composite sample which is promising for room temperature flexible thermoelectric application.