Orbital Splitting and Interstitial Doping Lead to High Thermoelectric Performance in n-type PbSe.

PbSe has garnered significant attention due to its earth-abundance and low cost of Se element. Here the synthesis of Zn and Sn co-doped n-type PbSe with noteworthy thermoelectric performance enhancement is reported. Microstructural characterization and first-principles calculations demonstrate that Zn occupies the interstitial site between Se tetrahedra in PbSe, thereby creating a high-density network of needle-like defects that induces lattice strain and reduces the lattice thermal conductivity. Zn interstitial doping provides additional free electrons, leading to sharp increase of carrier concentration. DFT calculation reveals that orbital splitting of VBM boosts carrier mobility of PbSe. The significantly enhanced carrier mobility produces high power factor in the whole temperature range. As a result, a high peak ZT of 1.7 is realized for Zn and Sn co-doped n-type PbSe with a remarkable average ZT of 1.2 over the temperature range of 423-873K. These findings demonstrate that combining orbital splitting and interstitial doping is an effective strategy to synergistically optimize the electrical-thermal transport of n-type PbSe, making it a promising candidate for energy conversion applications.