Strong Valence Band Convergence to Enhance Thermoelectric Performance in PbSe with Two Chemically Independent Controls

Abstract

We present an effective approach to favorably modify the electronic structure of PbSe using Ag doping coupled with SrSe or BaSe alloying. The Ag- 4d states make a contribution to in the top of the heavy hole valence band and raise its energy. The Sr and Ba atoms diminish the contribution of Pb- 6s2 states and decrease the energy of the light hole valence band. This electronic structure modification increases the density- of- states effective mass, and strongly enhances the thermoelectric performance. Moreover, the Ag- rich nanoscale precipitates, discordant Ag atoms, and Pb/Sr, Pb/Ba point defects in the PbSe matrix work together to reduce the lattice thermal conductivity, resulting a record high average ZTavg of around 0.86 over 400- 923- K.We find a new mechanism of strong band convergence with low onset temperature for p- type PbSe. The discordant Ag doping raises the heavy hole band and Sr/BaSe alloying lowers the light hole band, leading to the fast and strong band convergence and significantly enhanced Seebeck coefficient.