Realization of both n- and p-type GeTe Thermoelectrics: Electronic Structure Modulation by AgBiSe2 Alloying

Successful applications of a thermoelectric material require simultaneous development of compatible n- and p-type coun-terparts. While the thermoelectric performance of p-type GeTe has been improved tremendously in recent years, it has been a challenge to find compatible n-type GeTe counterpart due to the prevalence of intrinsic Ge vacancies. Herein, we have shown that alloying of AgBiSe2 with GeTe results in an intriguing evolution in its crystal and electronic structures, resulting in n-type thermoelectric properties. We have demonstrated that the ambient rhombohedral structure of pristine GeTe transforms into cubic phase in (GeTe)100-x(AgBiSe2)x for x ≥ 25, with concurrent change from its p-type electronic character to n-type character in electronic transport properties. Such change in structural and electronic properties is con-firmed from the non-monotonous variation of band gap, unit cell volume, electrical conductivity and Seebeck coefficient, all of which show an inflection point around x ~ 20, as...