Topological doping effects in 2D chalcogenide thermoelectrics

A new study shows that doping 2D topological materials can dramatically alter their thermoelectric effects.

The team included: Chaochao Dun, Yu Liu, Ahmad Al-Qawasmeh, Corey A Hewitt, Yang Guo, Junwei Xu, Qike Jiang, Jian Wang, Gabriel Marcus, Doris Cadavid, David Montgomery, Hongzhi Wang, Kirill Kovnir, Andreu Cabot, and David L Carroll.

“This work may represent a major step in understanding how topological states contribute to thermopower.”

The study is an exhaustive examination in the proximal effects and energetic relationships between topological edge states and co-located dopants. Hall effect, XPS, and HRTEM, together with traditional transport, and thermopower as a function of temperature were used in the study.

Abstract

The topological nature of two-dimensional (2D) chalcogenide platelets, can present novel opportunities in thin, flexible thermoelectrics. In this work, metal dopants are added to the reactive edges of 2D Bi 2 Te 3 platelets. We show that along this active edge, an atomically well-ordered heterojunction is formed and facile charge exchange is created, onto the platelet and proximal to its known topological states. Temperature dependent conductivity suggests that local band bending across the interface may act as an injection energy filter for dopant-originated carriers. Moreover, as carrier density increases with increasing edge-dopant, carrier scattering does not appear to increase dramatically. As a result, an apparent decoupling between electrical conductivity and Seebeck coefficient occurs, leading to a surprisingly high power factors (PF): For example, the PF increases in Bi 2 Te 3 platelets by eight times.

reference:

2018/7/16, 2D Materials, Volume 5, Issue 4, Pages 045008, IOP Publishing