Synergistic tuning of carrier mobility, effective mass, and point defects scattering triggered high thermoelectric performance in n-type Ge-doped PbTe

Most achievements on remarkable thermoelectric performance have been made in the intermediate-temperature p-type PbTe. However, the n-type PbTe exhibits a relatively poor figure of merit ZT, which is urgently expected to be enhanced and compatible with the p-type counterpart. Here, we report that the introduction of excessive Pb can effectively eliminate cation vacancies in the n-type Pb1+xTe−0.4%I, leading to a considerable improvement of carrier mobility μ. Moreover, further Ge doping induces a large enhancement of thermoelectric properties due to the combined effect of improved electrical transport properties and increased phonon scattering in the n-type Pb1.01Te−0.4%I−y%Ge. The Ge doping not only contributes to the increase of the Seebeck coefficient owing to the increased effective mass m∗, but also gives rise to the dramatic decrease of lattice thermal conductivity due to the strengthened point defects scattering. As a result, a tremendous enhancement of the ZT value at 723 K reaches ∼1.31 of Pb1.01Te−0.4%I−3%Ge. Particularly, the average ZTave value of ∼0.87 and calculated conversion efficiency η∼13.5% is achieved by Ge doping in a wide temperature range from 323 to 823 K. The present findings demonstrate the great potential in the n-type Pb1.01Te−0.4%I−y%Ge through a synergistic tuning of carrier mobility, effective mass, and point defects engineering strategy.