No abstract

Four thermally cleavable polythiophene derivatives containing carbonate and solubilizing groups were synthesized for noncovalent modification of single-walled carbon nanotubes (SWCNTs). A well-dispersed polythiophene/SWCNTs composite was obtained by adsorption of the polymer at the SWCNT surface. The solution-processed composite film exhibited solid-state thermal cleavage of the insulating solubilizing group through decarboxylation, producing an insoluble composite film. The thermally cleavable composite film was evaluated for potential application as a thermoelectric (TE) material. The electrical conductivity (σ) of the thermally treated composite film was up to 250 times higher than that of the as-prepared composite film. The increased σ contributed to an increase in the power factor (PF). The ethanol-processed composite film could be applicable for green processing of a TE material using the less-toxic solvent. The substrate-free polythiophene/SWCNTs composite film prepared by simple solvent evaporation yielded a figure-ofmerit of 3.1 × 10 −2 with a PF of 28.8 μW m −1 K −2 at 25 °C. This solution-processed methodology is beneficial for the development of a flexible TE material.

Thermoelectric energy conversion is one of the most important applications of functional materials for energy. To realize practical applications, high conversion efficiency is required over a wide range of temperatures. Furthermore, abundance as well as environmental load of the elements constituting thermoelectric materials are important aspects to be considered. We report high thermoelectric performance over a wide range of temperatures in doped SnTe with multiple elements by exploiting synergistic effects of band convergence, resonance level formation, and carrier density optimization. An averaged ZT value between near room temperature and around 800 K is found to exceed 0.80 for Sn0.92Mn0.10In0.01Bi0.01Cu0.01Te, which shows that the SnTe-based thermoelectrics possess high potential for practical applications.