Realizing n-Type GeTe through Suppressing the Formation of Cation Vacancies and Bi-Doping

It is known that p-type GeTe-based materials show excellent thermoelectric performance due to the favorable electronic band structure. However, n-type doping in GeTe is of challenge owing to the native Ge vacancies and high hole concentration of about 10^21 cm^-3. In the present work, the formation energy of cation vacancies of GeTe is increased through alloying PbSe, and further Bi-doping enables the change of carrier conduction from p-type to n-type. As a result, the n-type thermoelectric performance is obtained in GeTe-based materials. A peak zT of 0.34 at 525 K is obtained for (Ge_0.6Pb_0.4)_0.88Bi_0.12Te_0.6Se_0.4. These results highlight the realization of n-type doping in GeTe and pave the way for further optimization of the thermoelectric performance of n-type GeTe.