Carriers: the Less, the Faster

Abstract

Thermoelectric (TE) community has long believed that high TE performance requires an optimal carrier concentration traditionally locating in the range of ~1019 to ~1021 cm−3. Herein, we propose that potential high TE performance might also be achieved at lower carrier concentrations of ~1018 to ~1019 cm−3. At this range, extremely large Seebeck coefficient with low thermal conductivity can be effortlessly obtained. The next step to achieve high ZT values is boosting the carrier mobility. We then propose two aspects for carrier mobility optimization, including the strategies of preparing single crystals, improving crystal symmetry, texturing, controlling microscopic defects, sharpening bands, aligning bands, and modulation doping. We also suggest it rather essential to utilize multiple of the strategies to achieve the significant optimization of carrier mobility. Our proposal will be the important guidance for realizing promising performance in new TE materials as well as revisiting the TE performance for traditional systems.