Enhanced average power factor and ZT value in PbSe thermoelectric material with dual interstitial doping

Thermoelectric materials necessitate both high power factors and ZT values in practical applications, as they determine the output power and conversion efficiency, respectively. However, the average power factor is often suppressed when structural defects are imported to pursue a high-ranged ZT value. In this work, a high average power factor of 24.18 μW cm⁻¹ K⁻² and an average ZT value of 1.01 at 300-773 K are simultaneously achieved for n-type Pb_1.02Se-0.2%Cu through dual interstitial doping, which surpasses other low-cost Se/S-based n-type thermoelectric materials. Its exceptional thermoelectric performance primarily stems from decoupled carrier and phonon transport properties induced by Pb and Cu dual interstitials. Firstly, Pb and Cu dual interstitials in n-type Pb_1.02Se-0.2%Cu can fully optimize temperature-dependent carrier density from 1.27 × 10¹⁹ cm⁻³ at 300 K to 3.90 × 10¹⁹ cm⁻³ at 773 K, thus maximizing the power factor to 32.83 μW cm⁻¹ K⁻² and resulting in an average power factor of 24.18 μW cm⁻¹ K⁻². Additionally, Pb and Cu dual interstitials cause electron-dominated hierarchical defects (cation interstitials, Se vacancies, dislocations and Pb precipitates), which can significantly reduce lattice thermal conductivity while preserving high electrical transport properties. As a result of the optimized electrical and thermal transport properties, the thermoelectric performance of n-type Pb_1.02Se-0.2%Cu is largely enhanced over a wide range of temperatures.