Thermoelectric performances for both p- and n-type GeSe.

Qiang Fan,Jin Cao,Chunhai Liu,Jianhui Yang

doi:10.1098/rsos.201980

Abstract

In this paper, the thermoelectric properties of p-type and n-type GeSe are studied systematically by using first principles and Boltzmann transport theory. The calculation includes electronic structure, electron relaxation time, lattice thermal conductivity and thermoelectric transport properties. The results show that GeSe is an indirect band gap semiconductor with band gap 1.34 eV. Though p-type GeSe has a high density of states near Fermi level, the electronic conductivity is relative low because there is no carrier transport pathway along the a-axis direction. For n-type GeSe, a charge density channel is formed near conduction band minimum, which improves the electrical conductivity of n-type GeSe along the a-axis direction. At 700 K, the optimal ZT value reaches 2.5 at 4 × 1019 cm−3 for n-type GeSe, while that is 0.6 at 1 × 1020 cm−3 for p-type GeSe. The results show n-type GeSe has better thermoelectric properties than p-type GeSe, indicating that n-type GeSe is a promising thermoelectric material in middle temperature.

Highlights

Thermoelectric material, as a functional material that can directly convert thermal energy to electrical energy without mechanical components, plays an important role in environmental pollution control and energy crisis resolution
The band gap calculated by generalized gradient approximation (GGA)-optB88 functional is 0.87 eV, which is consistent with 0.81 eV [39] and 0.85 eV [19] predicted by GGA-PBE functional
The electronic structure, band decomposition charge density and thermoelectric transport properties of GeSe are calculated by first-principles method and Boltzmann transport theory

Summary

Introduction

Thermoelectric material, as a functional material that can directly convert thermal energy to electrical energy without mechanical components, plays an important role in environmental pollution control and energy crisis resolution. Hao et al [19] calculated the GeSe electronic structure using VASP software with generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) exchange functional, and comparative study of the thermoelectric performance of GeSe and SnSe with the Boltzmann transport theory. They reported the ZT value of p-type GeSe along the b-axis is even higher than that of SnSe at the same carrier concentration. We do a systematic study on the electronic structure, electron transport properties, lattice thermal conductivity of GeSe to strengthen the understanding of the thermoelectric performance of GeSe, and promote its application in the thermoelectric field

Computational details

Results and discussion

Conclusion