Enhanced Thermoelectric Performance of n-Type Bi2Se3 Nanosheets through Sn Doping.

Ke Xiao,Andreu Cabot,Jordi Arbiol,Jordi Llorca,Yu Liu,Ting Zhang,Yu Zhang,Yong Zuo,Mengyao Li

doi:10.3390/nano11071827

Abstract

The cost-effective conversion of low-grade heat into electricity using thermoelectric devices requires developing alternative materials and material processing technologies able to reduce the currently high device manufacturing costs. In this direction, thermoelectric materials that do not rely on rare or toxic elements such as tellurium or lead need to be produced using high-throughput technologies not involving high temperatures and long processes. Bi2Se3 is an obvious possible Te-free alternative to Bi2Te3 for ambient temperature thermoelectric applications, but its performance is still low for practical applications, and additional efforts toward finding proper dopants are required. Here, we report a scalable method to produce Bi2Se3 nanosheets at low synthesis temperatures. We studied the influence of different dopants on the thermoelectric properties of this material. Among the elements tested, we demonstrated that Sn doping resulted in the best performance. Sn incorporation resulted in a significant improvement to the Bi2Se3 Seebeck coefficient and a reduction in the thermal conductivity in the direction of the hot-press axis, resulting in an overall 60% improvement in the thermoelectric figure of merit of Bi2Se3.

Highlights

Thermoelectric (TE) devices that directly and reversibly convert heat into electricity find unlimited applications [1,2,3,4,5,6], but their real implementation is hampered by their low cost-effectiveness
The X-ray diffraction (XRD) analysis showed that the crystal structure of the obtained nanosheets matched the rhombohedral Bi2 Se3 phase (Figure 1d, JCPDS No 00-033-0214)
The HRTEM characterization showed that the material has good crystallinity and has a crystal phase consistent with the Bi2 Se3 rhombohedral phase with a = b = 4.1340 Å and c = 28.6300 Å (Figure 1f,g)

Summary

Introduction

Thermoelectric (TE) devices that directly and reversibly convert heat into electricity find unlimited applications [1,2,3,4,5,6], but their real implementation is hampered by their low cost-effectiveness. The efficiency of energy conversion of a TE device is in part determined by the transport properties of the TE material: Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ. These material properties are generally grouped into a dimensionless figure of merit, ZT = S2 σT/κ, where T is the absolute temperature. TE materials are characterized by high power factors, S2 σ, and low thermal conductivities, κ. Several strategies have been developed to maximize ZT, including engineering the electronic band structure of the TE material through doping [7], the use of energy filtering interphases [8], and the reduction in lattice thermal conductivity through the introduction of abundant grain boundaries [9]

Methods

Results

Conclusion