Anomalous enhancement of thermoelectric power factor by thermal management with resonant level effect†
Obtaining high thermoelectric performance has been the biggest historical challenge for thermoelectric power generation. Here, we propose a methodology for thermoelectric power factor enhancement: thermal management with resonant level effect for simultaneous increase of electrical conductivity σ and Seebeck coefficient S. Au crystals and Au impurities are introduced into SiGe. Therein, (1) highly-conductive Au crystals increased σ. (2) Au impurities brought about resonant level effect and phonon scattering, resulting in enhanced S and lowered thermal conductivity κ of SiGe. (3) This κ distribution control brings the focus of temperature difference on SiGe parts with lowered κ, resulting in the availability of the enhanced S of SiGe parts as effective S of the entire nanocomposite. Consequently, we achieved the highest S2σ at room temperature among SiGe-related materials ever reported. Electronic structure calculation and measurement support the existence of resonant levels, which enhances S and lowers κ. These results provide a new route to thermoelectric performance enhancement.