Achieving ZT=2.2 with Bi-doped n-type SnSe single crystals.

Anh Tuan Duong,Jae Yong Song,Sunglae Cho,Van Thiet Duong,Van Quang Nguyen,Jae Ki Lee,Sudong Park,Jungdae Kim,Taewon Min,Ji Eun Lee,Jaekwang Lee,Suyong Kwon,Ganbat Duvjir

doi:10.1038/ncomms13713

Abstract

Recently SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. For thermoelectric device applications, it is necessary to have n-type materials with comparable ZT value. Here, we report that n-type SnSe single crystals were successfully synthesized by substituting Bi at Sn sites. In addition, it was found that the carrier concentration increases with Bi content, which has a great influence on the thermoelectric properties of n-type SnSe single crystals. Indeed, we achieved the maximum ZT value of 2.2 along b axis at 733 K in the most highly doped n-type SnSe with a carrier density of −2.1 × 1019 cm−3 at 773 K.

Highlights

SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K
The performance of a thermoelectric material is estimated via the relation of the Seebeck coefficient (S), electrical conductivity (s) and thermal conductivity (k) at a temperature (T), which is called the thermoelectric figure of merit, ZT 1⁄4 S2sT/k
Bulk SnSe is a well-known p-type semiconductor with an indirect band gap energy of Eg 1⁄4 0.829 eV at 300 K with an orthorhombic Pnma phase (a 1⁄4 11.49 Å, b 1⁄4 4.44 Å, c 1⁄4 4.14 Å) and a direct band gap of Eg 1⁄4 0.464 eV with a Cmcm structure phase at high temperatures (750–800 K)[6,7]. It exhibits a two-dimensional (2D) layered structure with strong tin–selenium (Sn–Se) covalent bonding along the b–c plane and a weak Van der Waals force along the a axis, which gives the material strong anisotropic transport properties[8]

Summary

Introduction

SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. Zhao et al.[9] reported that bulk SnSe is a very good p-type thermoelectric material due to its low thermal conductivity at high temperature; ZT values along the b and c axes are up to 2.6 and 2.3 at 923 K, respectively.

Results

Conclusion