Dynamic doping and Cottrell atmosphere optimize the thermoelectric performance of n-type PbTe over a broad temperature interval

• Published in: Nano energy 2022-10, Vol.101, p.107576, Article 107576
• Main Authors: Yu, Yuan, Zhou, Chongjian, Zhang, Xiangzhao, Abdellaoui, Lamya, Doberstein, Christian, Berkels, Benjamin, Ge, Bangzhi, Qiao, Guanjun, Scheu, Christina, Wuttig, Matthias, Cojocaru-Mirédin, Oana, Zhang, Siyuan
• Format: Article
• Language: English
• Subjects: Atom probe tomography; Cottrell atmosphere; Dislocation array; Dynamic doping; In-situ scanning transmission electron microscopy; Thermoelectric
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2022.107576

High thermoelectric energy conversion efficiency requires a large figure-of-merit, zT, over a broad temperature range. To achieve this, we optimize the carrier concentrations of n-type PbTe from room up to hot-end temperatures by co-doping Bi and Ag. Bi is an efficient n-type dopant in PbTe, often leading to excessive carrier concentration at room temperature. As revealed by density functional theory calculations, the formation of Bi and Ag defect complexes is exploited to optimize the room temperature carrier concentration. At elevated temperatures, we demonstrate the dynamic dissolution of Ag2Te precipitates in PbTe in situ by heating in a scanning transmission electron microscope. The release of n-type Ag interstitials with increasing temperature fulfills the requirement of higher carrier concentrations at the hot end. Moreover, as characterized by atom probe tomography, Ag atoms aggregate along parallel dislocation arrays to form Cottrell atmospheres. This results in enhanced phonon scattering and leads to a low lattice thermal conductivity. As a result of the synergy of dynamic doping and phonon scattering at decorated dislocations, an average zT of 1.0 is achieved in n-type Bi/Ag-codoped PbTe between 400 and 825 K. Introducing dopants with temperature-dependent solubility and strong interaction with dislocation cores enables simultaneous optimization of the average power factor and thermal conductivity, providing a new concept to exploit in the field of thermoelectrics. [Display omitted] •Carrier concentrations are optimized over a broad temperature interval by combining static and dynamic doping.•The formation of Bi and Ag defect complexes is revealed by density functional theory calculations.•Dynamic dissolution of Ag2Te in PbTe is demonstrated by in-situ heating scanning transmission electron microscope.•Dislocation arrays and Cottrell atmospheres as revealed by atom probe tomography lead to a low lattice thermal conductivity.•An average zT of 1.0 is achieved in n-type PbTe between 400 and 825 K temperature intervals.