Poly{[N ,N′ -bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis-(dicarboximide)-2,6-diyl]-alt -5,5′ -(2,2′ -bithiophene)} or P(NDI2OD-T2) is an air-stable, electron conducting semiconducting polymer with high mobility due to its unique morphology in the solid state. However, pristine P(NDI2OD-T2) films have a very low electrical conductivity due the absence of free charge carriers. Herein, we focused on measuring the electrical properties of air-stable thermoelectric polymer hybrid films using P(NDI2OD-T2) and Ag2Te nanowires (NWs). Silver telluride was synthesized in a two-step process. First, Te NWs were prepared by chemical reduction of TeO2 with ascorbic acid in ethylene glycol. Transmission electron microscopy (TEM) revealed straight, high aspect ratio Te NWs with average lengths of 26 μm and diameters of 460 nm. Second, Te NWs were stirred with silver nitrate in ethylene glycol and converted into Ag2Te. TEM analysis revealed rough surfaces and bent wire morphology with average lengths of 7.0 μm and diameters of 712 nm. Powder x-ray diffraction confirmed the beta phase of Ag2Te was formed. The electrical conductivity of films containing P(NDI2OD-T2) and 45, 55, 65 and 75 weight percent Ag2Te were measured. As the amount of Ag2Te was increased the electrical conductivity increased. A maximum electrical conductivity of 0.340 S/cm was measured for the 75 wt% Ag2Te/P(NDI2OD-T2) film. The Seebeck coefficients were measured for each film and remained relatively unchanged with values ranging from -109 to -127 μV/K. The negative Seebeck coefficient suggests that the majority charge carriers are electrons. A power factor of 9 x 10-7 W m-1 K-2 was determined for the 75 wt% Ag2Te films and represents one of the highest values measured for an air-stable, P(NDI2OD-T2) derived thermoelectric material.

Electrical conductivity and Seebeck coefficient of air-stable n-type polymer composite films

255th National Meeting (2018)

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