Promising Thermoelectric Performance in Two-Dimensional Semiconducting Boron Monolayer.

Yonglan Hu,Guangqian Ding,Shichang Li,Rongkun Liu,Dengfeng Li,Ding Li,Chunbao Feng

doi:10.3389/fchem.2021.739984

Yonglan Hu, Guangqian Ding + Show 5 more

Open Access

https://doi.org/10.3389/fchem.2021.739984

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Abstract

A heavy element is a special character for high thermoelectric performance since it generally guarantees a low lattice thermal conductivity. Here, we unexpectedly found a promising thermoelectric performance in a two-dimensional semiconducting monolayer consisting of a light boron element. Using first-principles combined with the Boltzmann transport theory, we have shown that in contrast to graphene or black phosphorus, the boron monolayer has a low lattice thermal conductivity arising from its complex crystal of hexagonal vacancies. The conduction band with an intrinsic camelback shape leads to the high DOS and a high n-type Seebeck coefficient, while the highly degenerate valence band along with the small hole effective mass contributes to the high p-type power factor. As a result, we obtained the p-type thermoelectric figure of merit up to 0.96 at 300 K, indicating that the boron monolayer is a promising p-type thermoelectric material.

Highlights

In the past decade, people devoted themselves to improve the thermoelectric efficiency by trying to individually control the thermoelectric coefficients through low-dimensional crystals such as single layers, nanowires, 2D heterostructures, and nanotubes
To explore the potential of the semiconducting βs1 boron monolayer as a thermoelectric material, we studied its thermoelectric transport performance by first-principles combined with Boltzmann transport equations
0.998 p-type phonon spectrum and molecular dynamics simulation confirm the thermal stability of this boron monolayer

Summary

INTRODUCTION

People devoted themselves to improve the thermoelectric efficiency by trying to individually control the thermoelectric coefficients through low-dimensional crystals such as single layers, nanowires, 2D heterostructures, and nanotubes. Using a molecular dynamics simulation, Xu et al (2015) obtained the lattice thermal conductivity of phosphorene along the zigzag direction that is higher than 150 W/mK at 300 K Among these popular single-layer crystals, it was found that an extremely high thermal conductivity leads to poor ZT, which can be ascribed to the following two factors: 1) light elements with high vibration frequency and 2) large atomic weight difference forbids the anharmonic scattering. Within this approximation, the Seebeck coefficient can be calculated independent of carrier relaxation time τ, while the evaluation of electrical conductivity still requires the knowledge of τ In this regard, we employed deformation potential theory based on effective mass approximation to FIGURE 1 | The atomic structure (A) and the Brillouin zone path (B) of the βs boron monolayer and (C) shows the calculated band structure and density of states. The phonon spectrum was obtained from the Phonopy code (Togo et al, 2008), and a converged cutoff distance of 0.4 nm for interactive distance was used in calculating anharmonic IFCs

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT