Ultrahigh carrier mobility contributes to remarkably enhanced thermoelectric performance in n-type PbSe

A high average ZT value (ZTave) of ∼1.13 in an n-type PbSe-based thermoelectric material at 300-873 K has been achieved in this work. Its high thermoelectric performance originates from ultrahigh carrier mobility in the whole working temperature range through synergistically tuning the carrier effective mass, carrier density and microstructure. To maximize the carrier mobility in n-type PbSe, the conduction band shape is firstly optimized through SnS alloying to lower the carrier effective mass, which can benefit a high carrier mobility. Moreover, the carrier density is reoptimized to match its lowered carrier effective mass with Cu interstitial doping, and the suppressed carrier-carrier scattering can further enhance its carrier mobility, leading to a maximum carrier mobility of ∼6081 cm2 V-1 S-1 and a maximum power factor of ∼26.1 μW cm-1 K-2 at 300 K in PbSe-18%SnS-0.5%Cu. Additionally, the microstructure observation reveals that the intrinsically layered SnS phase can be endotaxially embedded as cubic SnS nanocrystals to form semi-coherent phase boundaries in a PbSe matrix, which also plays a significant role in maintaining carrier transmission and simultaneously blocking phonons. With these well optimized carrier and phonon transport properties, the room-temperature ZT value reaches ∼0.6 and continuously increases to ∼1.6 at 773 K in n-type PbSe-18%SnS-0.5%Cu. This remarkably enhanced thermoelectric performance in this work outperforms that of previously reported n-type PbSe-based materials.