Significant enhancement of thermoelectric properties of conducting PTB7 polymer by addition of appropriate dopants

Abstract

AbstractThermoelectric properties of poly({4,8‐bis [(2‐ethylhexyl)oxy] benzo [1,2‐b:4,5‐b'] dithiophene‐2,6‐ diyl}{3‐fluoro‐2‐ [(2‐ethylhexyl) carbonyl] thieno[3,4‐b] thiophenediyl}), commonly known as PTB7 conducting polymer was investigated for the first time by the first author in 2017, and it showed higher electrical conductivity or Seebeck coefficient (or even both) and hence, higher thermoelectric power factor than a variety of organic semiconductors. Therefore, it is worth working more on this semiconductor to improve its thermoelectric power factor. In this work, for the first time, 4 new dopants are introduced to PTB7 polymer to improve its thermoelectric properties. The materials are famous oxidants that are inexpensive and easily available with no need to perform any synthesis process, including antimony pentachloride (SbCl5), iron trichloride (FeCl3), thionyl chloride (SOCl2), and iodine (I2). As a result, significant enhancement of thermoelectric power factor after doping with antimony pentachloride (from 0.224 to 25.5 μWK−2 m−1,) and iron trichloride (from 0.224 to 18.2 μWK−2 m−1,) and moderate enhancement with thionyl chloride was obtained. For the case of iodine doping, simultaneous enhancement of electrical conductivity and Seebeck coefficient was observed due to increasing the mobility.