Two soluble polymers with lower ionization potentials: doping and thermoelectric properties

Doping and thermoeLectric properties of two soLution-processabLe conjugated poLymers with Low ionization potentials (IPs) have been studied and compared. An optimized thermoeLectric power factor (PF) approaching 40 mu W m(-1) K-2 at 390 K was achieved in films of poLymer PDTPT-C12, by performing doping treatment with LiTFSI soLution in air, while an optimized thermoeLectric power factor around 12 mu W m(-1) K-2 at 390 K was observed when CuTFSI2 soLution was used instead of LiTFSI. In contrast, such effects on thermoeLectric performance as a result of dopant species were not observed in the other studied poLymer PTVT2T-C12 with comparable IP. Based on the results of thermoeLectric measurements and optical spectroscopy as weLL as photoelectron spectroscopy, the role of Li+ in the resultant thermoeLectric performance was proposed. Moreover, owing to the relatively Low IPs of the two studied poLymers, the as -doped poLymer films are reasonably stable under ambient conditions. Therefore, Na[kyE dithieno[3,2b:2',3'-d] pyrroLes (DTPs) as exemplified in the case of PDTPT-C12 are suggested to be promising building-blocks and the incorporation of small cations Like Li+ may be an alternative to increase the thermopower in solid state devices.