No abstract

We used first-principles calculations based on density functional theory and the Boltzmann transport equation with an empirical relaxation time scheme to investigate the thermoelectric (TE) properties of Bi2(Se x Te1-x )3 alloys. We examined various TE indicators and found that Bi2SeTe2 shows relatively highest TE performance in Bi2(Se x Te1-x )3 alloys than bulk Bi2Te3. The result indicated that it is difficult to find the favorable Se composition for Bi2(Se x Te1-x )3 via power factor. The findings suggested that our computational framework provides a useful guide for the effect of Se incorporation on TE performance of Bi2(Se x Te1-x )3 alloys.

The long-term stability of n-type single-walled carbon nanotubes (SWCNTs) in air makes all-carbon thermoelectric generators (TEGs) viable. To increase the performance of TEGs, we developed a dual-type flexible-film thermoelectric generator (DFTEG). The vacuum filtering was used to form p- and n-type SWCNT films from ethanol-based dispersion and water-based solutions with cationic surfactant, respectively. DFTEGs were fabricated as follows: strip-shaped p- and n-type SWCNT films were attached on the top and back sides of a polyimide substrate, respectively, and were connected alternately in series by bending copper tapes on the edge of the polyimide substrate. The thermoelectric performance was measured after attaching the DFTEG outside a beaker full of water, where the water surface reached the center of the DFTEG. For a 10 mm long film and 15 p-n pairs, the DFTEG had an output voltage of 40 mV and a maximum power of 891 nW at a temperature difference of 25 K. The measured thermoelectric performance was significantly higher than that of the single-type TEG for almost the same SWCNT films. This result demonstrates that thermoelectric performance can be improved by using DFTEGs that are fabricated with optimum structural designs.